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The article presents the case of a 58-year-old man, who visited the outpatient clinic of department of neurology due to onset of a new onset, persistent, progressive, and severe headache. The patient felt pressure in the vertex area, and tightness in the shoulders, the back of the neck and occipital regions, but there were no other associated symptoms.

Clinically, implant-related bone infections are a serious concern as they reduce the success rate of grafting techniques and increases the risk of morbidity. Clinicians use antibiotics to treat bone grafts. Silver-based components are gaining popularity for their exceptional antimicrobial activity. The current review provides the preparative procedure, characterization methods, and mechanical strength of silver-based composites. Additionally, the assessment includes information on the biocompatibility of silver-based composites and clinical studies for bone tissue engineering. Finally, the review discusses titanium implants coated with silver-based composites, their derivatives, and related studies. Overall, silver-based composites are a potential candidate for bone tissue engineering. [ABSTRACT FROM AUTHOR]

A novel method for identifying DNA-binding proteins from image analysis using AFM was developed. Here, transcription factor NFκB, which a well-studied example of transcription activator proteins, was used as a target protein. 5′-Biotinlynated double-stranded DNA probe was labeled site specifically through high affinity with streptavidin. When the biotinylated DNA fragments were incubated with the streptavidin at a 1:2 molar ratio of DNA:streptavidin, the overall efficiency of labeling was over 90%. The double-stranded DNA probes were immobilized on a mica surface by the adsorption of streptavidin that attached to the 5′-end of DNA and applied for selection of the target protein NFκB in solution and then AFM was used to image the DNA probe–NFκB complexes. The length of the distance between 5′-labeled streptavidin and NFκB bound on DNA probes from AFM images is 0.64, the normalized position of the NFκB binding site, and this result is in close agreement with the expected 299 and 167 bp values. [Copyright &y& Elsevier]

Nanoparticle-based therapy has gained much attention in the pharmaceutical industry. Fucoidan is a sulfated polysaccharide naturally derived from marine brown algae and is widely used for medical applications. We explore preparation of fucoidan-based nanoparticles and their biomedical applications in the current review. The fucoidan-based nanoparticles have been synthesized using microwave, emulsion, solvent evaporation, green synthesis, polyelectrolyte self-assembly, precipitation, and ultrasonication methods. The synthesized nanoparticles have particle sizes ranging from 100 to 400 nm. Therefore, fucoidan-based nanoparticles have a variety of potential therapeutic applications, including drug delivery, cancer therapies, tissue engineering, antimicrobial applications, magnetic resonance imaging contrast, and atherothrombosis imaging. For example, fucoidan nanoparticles have been used to deliver curcumin, dextran, gentamicin, epigallocatechin gallate, and cisplatin for cancer therapies. Furthermore, fucoidan nanoparticles coupled with metal nanoparticles have been used to target and recognize clinical conditions for diagnostic purposes. Hence, fucoidan-based nanoparticles have been helpful for biomedical applications. [Display omitted] [ABSTRACT FROM AUTHOR]

The in situ synthesis is reported of citric acid-functionalized ultra-fine bimetallic PtRu alloy nanoparticles (CA@PtRu ANPs) through a simple one-pot wet chemical method. The cost-efficient CA@PtRu ANPs with an average diameter of 3.2 nm revealed to have enhanced surface area, peroxidase-like activity, high stability, and adequate availability of functional groups to bind biomolecules. Along with nanoparticle surface area, the surface charge has also significantly affected the peroxidase-like activity and the colloidal suspension stability. As an excellent immobilization matrix and peroxidase mimic, the CA@PtRu ANPs were utilized to develop non-enzymatic colorimetric immunoassay for rapid, selective, and sensitive quantification of C-reactive protein (CRP) biomarkers. In this immunoassay, CA@PtRu ANPs serve as enzyme mimic that significantly amplifies the color signals, and amine-functionalized silica-coated magnetic microbeads (APTES/SiO2@Fe3O4) act as CRP-recognizing capture probes. The absorbance curves of colorimetric immunoassay were measured in wavelengths between 550 and 750 nm, and the maximum absorbance at 652 nm was used to establish a linear relationship between absorbance and CRP concentrations. The developed colorimetric immunoassay showed rapid and sensitive quantification of CRP levels from 0.01 to 180 μg mL−1 with a LOD of 0.01 μg mL−1. Moreover, the mean recovery of CRP from spiked human serum samples lies between 97 and 109% (n = 3), which indicates that the proposed nanozyme-linked immunoassay has the potential to be used in rapid point-of-care applications. [ABSTRACT FROM AUTHOR]

The widespread use of cyanide (CN−) in industry results in contamination of various effluents such as drain, lake, and tap water, an imminent danger to the environment and human health. We prepared naphthoquinolinedione (cyclized; 1 – 5) and anthracenedione (un-cyclized) probes (6 – 7) for selective detection of CN−. The addition of CN− to the probe solutions (1 – 5) resulted in a color change from pale green to orange under 365 nm illumination. The nucleophilic addition of CN− to C2 of the imidazolium ring of the probes is responsible for selective CN− detection. Among all probes, 1 gave the lowest fluorescence-based LOD of 0.13 pM. In contrast, the un-cyclized probes (6 and 7) were substantially inferior to the cyclized counterparts (1 and 2 , respectively) for detecting a trace amount of CN−. The notably low LOD displayed by probe 1 was maintained in the detection of CN− in real food samples, human fluids, and human brain cells. This is the first report studying imidazolium-bearing naphthoquinolinedione-based probes for CN− sensing in 100% water. Water-soluble probe 1 displayed a selective CN− sensing in water, along with a very low LOD of 0.13 pM and the probe was successfully applied for CN− sensing in human bio-fluids and food items. [Display omitted] • Several probes 1 – 7 were prepared in a single step. • Probe 1 showed a selective color change upon addition of CN−. • Formation of [probe 1 -CN−] adduct is responsible for fluorescence response. • Probe 1 displayed an effective detection of CN− in food samples and human bio-fluids. • A concentration of CN− as low as 1 μM was detected in human brain cells using probe 1. [ABSTRACT FROM AUTHOR]

[Display omitted] • Tumor microenvironment (TME)-activatable metal–organic frameworks (MOF) were developed for targeted tumor therapy. • pH-responsive breakdown of the framework gradually released glucose oxidase/Prussian Blue nanozyme, boosting tumor specificity. • Starvation therapy mediated by glucose oxidase was used to enhance chemodynamic therapy as well as to starve tumor cells. • Cascade catalytic reactions promoted ROS-induced DNA cleavage, growth inhibition, and finally tumor cell apoptosis. • The antitumor nanocomposites enabled chemodynamic/starvation synergism, high therapeutic efficiency, and minimal side effects. Targeted tumor therapy through tumor microenvironment (TME)-responsive nanoplatforms is an emerging treatment strategy used to enhance tumor-specificity to selectively kill cancer cells. Here, we introduce a nanosized zeolitic imidazolate framework-8 (ZIF-8) that simultaneously contains natural glucose oxidase (GOx) and Prussian blue nanoparticles (PBNPs) to construct multi-component metal-organic framework nanocomposites (denoted as ZIF@GOx@PBNPs), which possess cascade catalytic activity selectively within the TME. Once reaching a tumor site, GOx and PBNPs inside the nanocomposites are sequentially released and participate in the cascade catalytic reaction. In weak acidic TME, GOx, which effectively catalyzes the oxidation of intratumoral glucose to hydrogen peroxide (H 2 O 2) and gluconic acid, not only initiates starvation therapy by cutting off the nutrition source for cancer cells but also produces the reactant for sequential Fenton reaction for chemodynamic therapy. Meanwhile, PBNPs, which are released from the ZIF-8 framework dissociated by acidified pH due to the produced gluconic acid, convert the generated H 2 O 2 into harmful radicals to melanomas. In this way, the cascade catalytic reactions of ZIF@GOx@PBNPs enhance reactive oxygen species production and cause oxidative damage to DNA in cancer cells, resulting in remarkable inhibition of tumor growth. The tumor specificity is endowed by using the biomolecules overexpressed in TME as a "switch" to initiate the first catalytic reaction by GOx. Given the significant antitumor efficiency both in vitro and in vivo, ZIF@GOx@PBNPs could be applied as a promising therapeutic platform enabling starvation/chemodynamic synergism, high therapeutic efficiency, and minimal side effects. [ABSTRACT FROM AUTHOR]

Lysophosphatidylcholine (LPC) can be used as a biomarker for diseases such as cancer, diabetes, atherosclerosis, and sepsis. In this study, we demonstrated the ability of nanozymes to displace the natural derived enzyme in enzyme-based assays for the measurement of LPC. Synthesized polyvinylpyrrolidone-stabilized platinum–ruthenium nanozymes (PVP/PtRu NZs) had a uniform size of 2.48 ± 0.24 nm and superb peroxidase-mimicking activity. We demonstrated that the nanozymes had high activity over a wide pH and temperature range and high stability after long-term storage. The LPC concentration could be accurately analyzed through the absorbance and fluorescence signals generated by the peroxidation reaction using the synthesized nanozyme with substrates such as 3,3′,5,5′-tetramethylbenzidine (TMB) and 10-acetyl-3,7-dihydroxyphenoxazine (Ampliflu™ Red). LPC at a concentration of 0–400 µM was used for the analysis, and the coefficient of determination (R2) was 0.977, and the limit of detection (LOD) was 23.1 µM by colorimetric assay. In the fluorometric assay, the R2 was 0.999, and the LOD was 8.97 µM. The spiked recovery values for the determination of LPC concentration in human serum samples were 102–115%. Based on these results, we declared that PVP/PtRu NZs had an ability comparable to that of the native enzyme horseradish peroxidase (HRP) in the enzyme-based LPC detection method. [ABSTRACT FROM AUTHOR]

This paper describes a simple electrochemical sensing platform based on single-walled carbon nanotube (SWCNT) electrodes for glucose detection. The device fabrication using O2-plasma treatment allows precision and uniformity for the construction of three SWCNT electrodes on the flexible plastic substrate. Glucose assay can be simply accomplished by introducing a glucose sample into the fabricated biosensor. The marked electrocatalytic and biocompatible properties of biosensors based on SWCNT electrodes with the incorporation of ferrocenecarboxylic acid and polyethylene glycol enable effective amperometric measurement of glucose at a low oxidation potential (0.3 V) with low interferences from coexisting species. The device shows efficient electroanalytical performances with high sensitivity (5.5 μA·mM−1·cm−2), good reproducibility (CV less than 3%), and long-term stability (over a month). A linear range of response was found from 0 to 10 mM of glucose with a fast response time of 10 s. This attractive electroanalytical device based on GOx/FCA/PEG/SWCNT electrodes offers a promising system to facilitate a new approach for diverse biosensors and electrochemical devices. [ABSTRACT FROM AUTHOR]

Nanozymes, or artificial enzymes, have received a great deal of attention in recent years because of their superior enzyme-like capabilities over natural enzymes. The transition-metals are being investigated for their intrinsic nanozyme activity in various applications, including biosensors, antimicrobials, cytoprotection, anticancer, tissue engineering, and drug delivery. Especially, silver (Ag) is one of the transition-metals that has been investigated intensively since the turn of the century because of its biological activity and catalytic properties. This review discussed various Ag-based hybrid nanozymes preparation and their enzyme-like activity by combining Ag with other metals, salts, and organic molecules. Ag-based hybrid nanozymes in the form of metal–organic frameworks, complexes, bimetallic, hexacyanoferrate structures were summarized. Based on the literature results, Ag-based hybrid nanozymes are rapid, sensitive, and selective detection of various compounds, ions, and biological species such as hydrogen peroxide, glucose, phosphatase, glucose oxidase, acetylcholinesterase, cysteine, hepatitis E virus, sulfamethazine, uric acid, hypoxanthine, spermine, and gonadotropin. Moreover, Ag-based nanozymes are being investigated for antibacterial, cell protection, and anticancer applications. Future perspectives on Ag-based nanozymes were discussed at the end of the review. As a result, Ag-based hybrid nanozymes offer great potential for clinical trial applications and commercialization. [ABSTRACT FROM AUTHOR]

Dental caries is a common problem in adolescents, leading to permanent loss of teeth or cavitation. Caries is a continuous process wherein demineralization and remineralization occur regularly. Hydroxyapatite (HA) is one of the most biocompatible and bioactive materials, as it closely resembles the mineral composition of teeth. The present study deals with isolating hydroxyapatite from fish bone (Epinephelus chlorostigma) by alkaline hydrolysis and thermal calcination. The isolated nano HA was characterized using FT-IR, XRD, TGA, FE-SEM-EDX, and HR-TEM analysis. The nano HA isolated by alkaline hydrolysis is nontoxic, and the cells are viable. The isolated HA enhances the proliferation of L929 cells. The remineralization potential of the extracted nano HA was evaluated in healthy premolars by DIAGNOdent/laser fluorescence quantification, surface microhardness test, and SEM-EDX analysis. Surface morphological observations in SEM and EDX analyses show that thermally calcined HA and alkali-treated HA can induce mineralization and deposit minerals. Therefore, HA obtained from Epinephelus chlorostigma could be a potential biomaterial for treating early caries. [ABSTRACT FROM AUTHOR]

The generation of a mesoporous structure in platinum nanoparticles can effectively enhance physical and chemical properties. In this study, mesoporous platinum nanoparticles (MPNs) were synthesized by a soft template-mediated one-pot chemical method. To develop a mesoporous structure, Pluronic F-127 was employed. The Pluronic F-127 surfactant forms self-assembled micelles, and the micelles act as the pore-directing agents in the synthesis of nanoparticles. Scanning electron microscopy results revealed that the MPN had a uniform size of 70 nm on average and a distinct mesoporous structure. The development of a concave mesoporous structure on the surface of the MPNs can increase the surface area and facilitate the efficient transport of reactants. The synthesized MPNs exhibited peroxidase-like activity. Furthermore, the MPNs showed excellent catalytic efficiency compared to HRP, due to the high surface area derived from the presence of the mesoporous structure. The peroxidase-like MPNs were applied to the enzyme-linked immunosorbent assay (ELISA) of C-reactive protein (CRP). The MPN-based ELISA exhibited sensitive CRP detection in the range from 0.24 to 7.8 ng/mL with a detection limit of 0.13 ng/mL. Moreover, the recoveries of the CRP concentrations in spiked human serum were 98.6% and 102%. These results demonstrate that as a peroxidase mimic, the MPNs can replace the natural enzymes in conventional ELISA for sensitive CRP detection. [ABSTRACT FROM AUTHOR]

Chitosan (CS)-stabilized platinum nanoparticles (CS/PtNPs) were employed to develop a novel aptamer-based dual-mode colorimetric and photothermal biosensor for selective detection of kanamycin (KAN). As a peroxidase-like catalyst, the CS/PtNPs showed outstanding catalytic activity for the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H 2 O 2). As a stabilizing agent, CS excelled at fixing the KAN binding aptamer on the surface of the CS/PtNPs, amplifying their catalytic activity and enhancing colloidal dispersion and stability. The oxidized TMB (TMB ox) functioned as a signal for the colorimetric, photothermal aptasensor because of its observable absorbance of light in the visible and near-infrared (NIR) regions. When light from a NIR laser was absorbed by the TMB ox in the reaction solution, heat was generated in inverse proportion to the KAN concentration. The developed colorimetric and photothermal modes of the aptasensor showed a linear detection range of 0.1–50 and 0.5–50 μM, with a limit of detection (LOD) of 0.04 and 0.41 μM, respectively. Moreover, the aptasensor successfully determined KAN concentrations in spiked milk samples, verifying the reliability and reproducibility in practical applications. The dual-mode aptasensor based on CS/PtNPs for KAN detection, utilizing both color change and heat generation signals through a single probe (TMB ox), demonstrates rapid response, simplicity in operation, cost-effectiveness, and high sensitivity. In addition, unlike typical immunoassays, this aptamer-based peroxidase-like nanozyme activation and inhibition strategy required no washing process, which was very effective in terms of reducing the time required for an assay and sustaining a high sensitivity. [Display omitted] [ABSTRACT FROM AUTHOR]

Mercury ions are an industrial and environmental toxin that need to be monitored and regulated in aqueous samples. We prepared six probes (1 – 6) using a naphthoquinolinedione ring as a fluorophore platform that contains different substituents on the quinolone ring. All probes showed abilities to selectively bind Hg2+, but their sensitivity to the detection of this metal ion significantly varied depending on the substituent pattern. Among these probes, probe 5 with Br and CN substituents on the quinolone ring was most effective for the sensitive detection of Hg2+ in aqueous solutions. This probe showed a naked-eye color change from yellow to purple upon binding to Hg2+. A ratio-metric method using UV–visible absorption data gave a limit of detection (LOD) of 20 nM, while the fluorescence-based result yielded an LOD of 0.047 pM. When bio-samples such as human urine and serum were used as media, the fluorescence-based LOD of this probe for Hg2+ detection increased to 50 nM. Probe 5 was also effective at detecting methylmercury, an organic mercury species, dissolved in drainage water or urine. Based on the results of DLS, FE-SEM, and DFT calculations, the probe appeared to form large aggregates and undergo photo-induced electron transfer (PET) upon Hg2+ binding, both of which are responsible for the probe fluorescence quenching. Probe 5 also showed the ability to sense Hg2+ within three different types of human cells: Brain cells (U87MG), Hela cells and skin cancer cells (SK-MEL28). Furthermore, this probe holds significant potential for on-site applications since various solid supports such as silica gel, filter papers and TLC plates were effectively used for sensitive and selective Hg2+ sensing, following probe coating/adsorption. Probe 5 showed the ability to effective detect Hg2+ in a buffer as well as bio-fluids such as humane urine and serum. The fluorescence-based LOD of this probe was found to be 0.047 pM for Hg2+ detection. [Display omitted] • Six naphthoquinolinedione-based probes (1 – 6) were prepared in two or three steps. • The fluorescence emission of probe 5 was effectively quenched upon Hg2+ addition. • Probe 5 gave an ultra-sensitive LOD of 0.047 pM for Hg2+ detection. • Probe 5 was capable of effectively sensing Hg2+ in bio-samples or within live cells. • Photo-induced electron transfer (PET) is mainly responsible for the fluorescence quenching. [ABSTRACT FROM AUTHOR]

The development of efficient and sensitive point-of-care testing is crucial for preparedness in the post-pandemic era. Although paper-based lateral flow assays have attracted attention and have various advantages for rapid, on-site diagnosis, they have low sensitivity. To overcome the limitations of the existing assays, in this study, we aimed to develop a new, one-step, nanozyme-amplified SlipChip for the sensitive detection of C-reactive protein (CRP). The SlipChip was constructed by combining wax-printed paper with different channel designs. The three-dimensional (3D) fluidic configuration of the SlipChip allowed for the sequential delivery of reagents, enabling mixing and signal amplification with a one-step sliding operation. As a signal-amplifying reagent, peroxidase-mimicking porous platinum nanozyme (pPtNZ) was synthesized using a simple wet chemical method. The pPtNZ conjugated on the test line catalyzes the oxidation of diaminobenzidine (DAB) in the presence of hydrogen peroxide, increasing the color intensity. The immunoassay results of the SlipChip were easily interpreted within 20 min, and the color intensity was visually enhanced by DAB precipitation over time, resulting in up to 6-fold signal amplification. The proposed pPtNZ-SlipChip exhibited high analytical performances for the one-step detection of serum and salivary CRP from 0.1 to 1000 ng/mL, with a limit of detection of 0.03 ng/mL. These results revealed the potential and applicability of the pPtNZ-SlipChip, with the advantages of simplicity, sensitivity, low cost, and portability for on-site detection and point-of-care testing. [ABSTRACT FROM AUTHOR]

Cancer is a life-threatening disease when it is diagnosed at a late stage or treatment procedures fail. Inhibiting cancer cells in the tumor environment is a significant challenge for anticancer therapy. The photothermal effects of nanomaterials are being studied as a new cancer treatment. In this work, rhenium disulfide (ReS 2) nanosheets were made by liquid exfoliation with gum arabic (GA) and coated with silver nanoparticles (AgNPs) to produce reactive oxygen species that destroy cancer cells. The synthesized AgNP-GA-ReS 2 NPs were characterized using UV, DLS, SEM, TEM, and photothermal studies. According to the DLS findings, the NPs were about 216 nm in size and had a zeta potential of 76 mV. The TEM and SEM analyses revealed that the GA-ReS 2 formed single-layered nanosheets on which the AgNPs were distributed. The photothermal effects of the AgNP-GA-ReS 2 NPs at 50 μg/mL were tested with an 808 nm laser at 1.2 W cm−2, and they reached 55.8 °C after 5 min of laser irradiation. MBA-MB-231 cells were used to test the cytotoxicity of the newly designed AgNP-GA-ReS 2 NPs with and without laser irradiation for 5 min. At 50 μg/mL, the AgNP-GA-ReS 2 showed cytotoxicity, which was confirmed with calcein and EtBr staining. The DCFH-DA and flow cytometry analyses demonstrated that AgNP-GA-ReS 2 nanosheets under NIR irradiation generated ROS with high anticancer activity, in addition to the photothermal effects. [Display omitted] • Gum arabic was the exfoliating agent for the liquid exfoliation of rhenium disulfide nanosheets. • Silver nanoparticles were capped onto gum arabic rhenium disulfide as a photothermal agent. • The silver nanoparticles in the AgNP-GA-ReS 2 generated reactive oxygen species and killed MDA-MB-231 cancer cells with an efficiency of 45.9% without laser treatment. • The synthesized AgNP-GA-ReS 2 showed an excellent photothermal conversion efficiency of 79.6% in MDA-MB-231 cells. • DCFH-DA and flow cytometry analyses demonstrated that reactive oxygen species formation increased during photothermal treatment with AgNP-GA-ReS 2. [ABSTRACT FROM AUTHOR]

A sensitive on-site mercury sensing platform was developed for simple and effective monitoring of mercury levels in the field. The simple and practical mercury detection system was designed by integrating an Au nanoparticle-PEG hydrogel block nanozyme (Au-HBNz) into a polymer film-based colorimetric device. Upon addition of Hg2+ ions, Au-HBNz exhibited excellent peroxidase-like activity, catalyzing the oxidation of 3,3',5,5'-tetramethylbenzidine into a blue-colored product, which has a maximum absorbance at 652 nm. The resulting color intensity change was evaluated using a smartphone for simple and rapid Hg2+ detection with a broad detection range (0.008–20 μg∙mL−1) and a linear concentration–response relationship (R2 = 0.96). The detection limit (1.10 ng∙mL−1) was lower than the maximum permissible Hg2+ levels in drinking water set by the World Health Organization (6 ng∙mL−1) and U.S. Environmental Protection Agency (2 ng∙mL−1). The recoveries of Hg2+ determination in river water by spiking Hg2+ samples ranged from 92 to 106%, which indicated high validity and applicability of the Hg2+ detection system for field measurements. Thus, the developed sensor enables highly selective and efficient real-time monitoring of Hg2+. [ABSTRACT FROM AUTHOR]

Dimethyl sulfoxide (DMSO) and dimethylformamide (DMF) are industrial toxins that need to be sensed. We synthesized 1,8-naphthalimide- m -benzenesulfonamide (NBS)-bearing probes (1 – 5) with different pendant chains for sensitive detection of DMSO and DMF. These probes exhibited aggregation-induced emission enhancement with increasing water concentration in ethanol. Among these, monopod probes with a single NBS unit (1 – 4) selectively showed large fluorescence quenching upon addition of DMSO/DMF in water. Based on this result, we prepared two water-soluble probes (8 and 9) bearing the NBS unit. These probes displayed enhanced sensitivity in detecting DMSO/DMF in water compared to probe 1 , showing an extraordinary low LOD of 0.0025% for DMSO and DMF detection in water. Probe 9 was similarly effective at sensitively sensing DMSO/DMF when tap or lake water was used as the medium, and the LOD of this probe was 0.05% when biological fluids such as diluted human urine and blood plasma were used instead of water. According to DLS, FE-SEM and zeta potential studies as well as DFT calculations, disaggregation of probe aggregates and electron transfer from the photo-excited probe to DMSO/DMF are likely both responsible for the high selectivity and sensitivity of this probe in detecting the organic solvents containing a sulfoxide/amide group. A novel 1,8-naphthalimide-based amphiphile (probe 9) selectively and sensitively detected DMSO and DMF in water, giving very low LODs of 8.30 and 5.90 nM, respectively. [Display omitted] • Eight 1,8-naphathalimide-based probes were prepared for DMSO/DMF detection. • Two probes (8 and 9) were water-soluble and showed AIEE behaviors. • The fluorescence emission of probe 9 was selectively quenched in the presence of DMSO/DMF. • Probe 9 gave an observed LOD of 0.0025% for DMSO/DMF sensing. • Probe 9 was applicable for a sensitive detection of DMSO/DMF in bio-samples. [ABSTRACT FROM AUTHOR]

The combination of Pt with low-cost transition metal is an effective way to diminish the bulk utilization of costly Pt and to design new nanostructured materials with improved enzyme-like activity. In the present work, citric acid-functionalized platinum–nickel hollow nanospheres (CA@PtNi hNS) were synthesized through a simple one-pot wet chemical method, which involves the galvanic replacement reaction between the Ni nanoparticles and the Pt precursor that leads to the formation of hollow nanostructures. Transmission electron spectroscopic images revealed the uniformity of the CA@PtNi hNS, with an average diameter of 10.3 ± 2 nm. Moreover, zeta potential, FTIR, and XPS measurements confirmed the existence of citric acid in the CA@PtNi hNS. During synthesis, the use of citric acid not only facilitates monodispersity but also provides a negative surface charge (−11 mV) to the CA@PtNi hNS that electrostatically attracts the 3,3′,5,5′-Tetramethylbenzidine (TMB) substrate. As-prepared CA@PtNi hNS possessed excellent peroxidase-like activity due to rich Pt surfaces, large surface area, and heterogeneous interaction between Pt and Ni atoms. Furthermore, a nanozyme-linked immunosorbent assay (NLISA) for human serum albumin (HSA) detection was developed by replacing the enzyme in a standard enzyme-linked immunosorbent assay with CA@PtNi hNS. The CA@PtNi hNS based-NLISA showed sensitive detection of HSA concentrations ranging from 0 to 400 ng mL−1 with a LOD of 0.19 ng mL−1 and an average of 112% recovery of HSA from the spiked human plasma samples. The outcomes of the present study confirm the applicability of CA@PtNi hNS as substitutes for natural enzymes. Unlabelled Image • Novel CA@PtNi hNS was used to develop enzyme-free ELISA for monitoring of HSA. • CA@PtNi hNS as peroxidase mimic was synthesized through one-pot wet chemical method. • CA@PtNi hNS showed excellent activity due to rich Pt surfaces and synergistic effect. • NLISA method was developed by replacing the enzyme in the ELISA kit for HSA with CA@PtNi hNS. • NLISA revealed 120% better sensitivity as compared to standard ELISA. [ABSTRACT FROM AUTHOR]

Nanozymes are effective substitutes for natural enzymes and offer multiple advantages. Here, synthesized Prussian blue nanoparticles (PBNPs) exhibited excellent peroxidase-like activity, catalyzing the oxidation of 3,5,3′,5′-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide within 1 min. Oxidized TMB (TMB ox) underwent a color change from transparent to blue and then yellow by a stop solution. Moreover, the TMB ox could be reduced on an indium tin oxide electrode, generating an electrochemical current, indicating that TMB can be used as a colorimetric and electrochemical indicator. The PBNPs modified with 3-aminophenylboronic acid (APBA) captured glycated albumin (GA) with a boronate affinity sandwich assay. As boronic acid binds to glycoproteins using cis -diol bonding, it can be used to detect GA. The APBA-modified PBNPs (PBBA) were involved with a sandwich complex formation and employed as nanozymes for the quantitative analysis of GA using colorimetric and electrochemical methods. Both methods showed strong linearities for different concentrations of GA. The results show that PBBA is a suitable alternative for natural enzymes and can be applied to sensitive determination of GA. Image 1 • Prussian blue nanozymes showed an excellent peroxidase-like activity. • Boronate affinity sandwich assays were developed to detect glycated albumin (GA). • The nanozymes were used in colorimetric and electrochemical assays of GA. • The developed assays were capable of accurate determination of GA in real samples. [ABSTRACT FROM AUTHOR]

• An electrochemical technique for live cell patterning was developed. • Various types of cells were patterned by optimizing electrochemical parameters. • Cell arrays patterned in microfluidic chips were used as drug screening platforms. High-resolution cell patterning technology is a versatile tool for studying tissue engineering and in vitro preclinical research, but simple methods that can be implemented easily are lacking. Here, we demonstrate a simple electrochemical approach for arranging cells into various patterns, enabling rapid and accurate localization for cell array formation. A voltage pulse is applied directly to the pre-patterned conducting substrate, causing cellular damage and rapidly forming live/dead cell arrays. The array platform, which focuses on assay miniaturization, is applicable to cell-based drug screening as well as high-content cell culture experiments. [ABSTRACT FROM AUTHOR]

We developed a new nanozyme-based electrochemical immunoassay method for the monitoring of glycated albumin (GA) known to reflect short-term glycaemic levels. For this study, we synthesized urchin-like Pt nanozymes (uPtNZs) and applied them to colorimetric and electrochemical assays for sensitive determination of GA in total human serum albumin (tHSA) using 3,3′,5,5′-tetramethylbenzidine (TMB) and thionine as substrates, respectively. The uPtNZs showed peroxidase-mimic activity in the presence of hydrogen peroxide. Boronic acid (BA)-agarose bead was used to capture GA through specific cis-diol interactions. uPtNZs were modified with GA antibody (GA-Ab) to form sandwich complexes with GA/BA-agarose bead. The amount of Ab-uPtNZ/GA/BA-agarose bead complex increased with increasing percentage of GA in 50 mg/mL tHSA. The colorimetric assay exhibited linearity from 0.02 to 10% (10 µg/mL – 5 mg/mL) GA with an LOD of 0.02% (9.2 µg/mL). For electrochemical assay, GA was detected from 0.01 to 20% (5 µg/mL – 10 mg/mL) with an LOD of 0.008% (3.8 µg/mL). The recovery values of measured GA in human plasma samples were from 106 to 107%. These results indicate that electrochemical assay using uPtNZs is a promising method for determining GA. [ABSTRACT FROM AUTHOR]

• Fusion protein of exenatide, repeats of elastin-based polypeptide, and His tag, was expressed from a recombinant yeast system. • Fusion protein improves in-serum half-life and maintain in vivo functionality of exenatide. • For a modified protein biobetters, balance between half-life extension and bioactivity maintenance is important. Exenatide (Ex) is a 39-amino acid peptide of glucagon-like peptide-1 (GLP-1) receptor agonist that was approved by the FDA in 2005 as a Type II diabetes treatment. It shows a 53% homology with GLP-1 but has an extended half-life (ca. 2.4 h) relative to GLP-1 (ca. 2–3 min). In this study, to further extend its in vivo half-life, we constructed a fusion protein (Ex-(EBP) 10 -6xHis) using a biocompatible and inert elastin-based polypeptide (EBP) as a fusion partner. Valine was inserted into the guest position of the pentapeptide (VPGXG), no linker sequence was inserted in between the EBPs, and (EBP) 10 -6xHis tag was attached to the C-terminus of exenatide. By using a recombinant Saccharomyces cerevisiae expression system, the fusion protein was expressed and secreted to the broth and purified by Ni-NTA affinity chromatography. Compared with the native exenatide, the physical half-life of the fusion protein was ca. 3.7-fold extended while approximately 72% of the in-vitro insulin secreting activity was maintained. However, the biological half-life measured by a glucose tolerance test (GTT) and the hypoglycemic test in mice was not significantly different from that of the native form. The effects of EBPylation on bioactivity and half-life of the fusion protein are similar to those of PEGylation. The result suggests that the bioactivity and half-life should be carefully balanced to obtain optimal fusion proteins. We expect that EBPylation using an optimal repeat number of EBP can be an alternative to chemical modification for therapeutic biobetters with extended half-life. [ABSTRACT FROM AUTHOR]

Au@PtNP/GO nanozymes were prepared as peroxidase mimics. The nanozymes showed remarkable peroxidase-like activity by the synergistic catalytic effect. For the electrochemical detection of H 2 O 2 , the nanozymes were integrated into POC devices. The developed POC devices were capable of accurate determination of H 2 O 2 in real samples. Nanostructured artificial enzymes, known as nanozymes, have been considered effective alternatives for natural enzymes with the attractive advantages. Herein, bimetallic Au and Pt nanoparticles with graphene oxide (GO) were immobilized chemically on the surface of agarose microbeads. Due to the synergistic effect of the bimetallic nanoparticles and GO (Au@PtNP/GO), this hybrid nanostructure exhibited strong peroxidase-like catalytic activity toward 3,3′,5,5′-tetramethylbenzidine (TMB) substrate in the presence of H 2 O 2. Colorimetric determination of H 2 O 2 , indicated by the blue color of the oxidized TMB within 1 min, was observed using the Au@PtNP/GO nanozymes. To demonstrate practical application of the nanozymes, the Au@PtNP/GO microbeads were packed into a film-based electrochemical point-of-care (POC) device for sensitive and rapid H 2 O 2 detection. Upon introduction of TMB substrate solution containing H 2 O 2 , the catalytically oxidized TMB was electrochemically reduced on the electrode surfaces, resulting in a broader detection range of H 2 O 2 (1 μM – 3 mM) and a lower LOD (1.62 μM) than achievable with the colorimetric detection method. Moreover, the developed POC devices showed the capability of accurate determination of H 2 O 2 with strong repeatability and reproducibility in real sample test using artificial urine. [ABSTRACT FROM AUTHOR]

Transition metal dichalcogenides (TMDs) have gained considerable attention for a broad range of applications, including cancer therapy. Production of TMD nanosheets using liquid exfoliation provides an inexpensive and facile route to achieve high yields. In this study, we developed TMD nanosheets using gum arabic as an exfoliating and stabilizing agent. Different types of TMDs, including MoS 2 , WS 2 , MoSe 2 , and WSe 2 nanosheets, were produced using gum arabic and were characterized physicochemically. The developed gum arabic TMD nanosheets exhibited a remarkable photothermal absorption capacity in the near-infrared (NIR) region (808 nm and 1 W⋅cm−2). The drug doxorubicin was loaded on the gum arabic–MoSe 2 nanosheets (Dox–G–MoSe 2), and the anticancer activity was evaluated using MDA-MB-231 cells and a water-soluble tetrazolium salt (WST-1) assay, live and dead cell assays, and flow cytometry. Dox–G–MoSe 2 significantly inhibited MDA-MB-231 cancer cell proliferation under the illumination of an NIR laser at 808 nm. These results indicate that Dox-G-MoSe 2 is a potentially valuable biomaterial for breast cancer therapy. [Display omitted] • The liquid exfoliation method was used to prepare transition metal dichalcogenide nanosheets (MoS 2 , WS 2 , MoSe 2 , and WSe 2). • Gum arabic was used as the exfoliating and stabilizing agent. • Doxorubicin loaded on gum arabic–MoSe 2 nanosheets (Dox–G–MoSe 2) exhibited photothermal efficiency. • Dox–G–MoSe 2 inhibited MDA-MB-231 cell proliferation and induced apoptosis. [ABSTRACT FROM AUTHOR]

Point-of-care testing has been extensively utilized for in-home diagnosis, customized testing, and pandemic monitoring. The current study aims to develop a nanozyme-mediated dual-readout (colorimetric and photothermal) bioassay for straightforward and sensitive detection of cholesterol. The nanozyme, cauliflower-like platinum nanostructures (CS@Pt NS) were synthesized by chemically reducing the Pt precursor in the chitosan (CS) solution. CS as a stabilizer excels at controlling the surface properties, enhancing peroxidase-like activity, and improving colloidal dispersion, and stability. The dual-readout sensor for cholesterol detection was proposed by combining cholesterol oxidase-catalyzed cholesterol oxidation with CS@Pt NS-catalyzed TMB oxidation. The oxidized TMB (TMBox) acts as a probe for both colorimetric and photothermal readouts because of having excellent absorbance in visible and near-infrared (NIR) regions. The absorption of NIR laser-driven light by the TMBox in the reaction solution generates heat, which is proportional to the concentration of cholesterol. The dual-readout sensor shows a linear detection range of 0–2 mM, with a limit of detection (LOD) of 45 µM for the colorimetric assay and 25 µM for the photothermal assay. Furthermore, the sensor successfully detects cholesterol in spiked human serum with acceptable accuracy. • Surprisingly, CS as a stabilizer enhances the peroxidase-like activity of CS@Pt NS. • Colorimetric & photothermal dual-readout biosensor developed for cholesterol detection. • A portable thermal imaging camera allows quick and accurate measurement of temperature. • Photothermal detection stands out for being more straightforward, convenient, and accurate. • The dual-readout sensor accurately detects cholesterol in spiked human serum. [ABSTRACT FROM AUTHOR]

Highlights • Graphene oxide (GO)-gold nanozymes were prepared as peroxidase mimics. • The nanozymes exhibited more enhanced activity than GO and AuNP alone. • The nanozymes were used for an electrochemical H 2 O 2 sensor. • The detection limit was much lower than that by colorimetric method. Abstract We fabricated a nafion/graphene oxide-gold nanoparticle (GO-AuNP) hybrid modified indium tin oxide (ITO) electrode and proposed an electrochemical method to detect hydrogen peroxide (H 2 O 2) using 3,3,5,5,-tetramethylbenzidine (TMB) as a redox mediator. The GO-AuNP hybrids were employed as nanozymes, which function as peroxidase mimics and show highly effective catalytic activity. Based on the high catalytic activity, enzyme mimics were entrapped on the ITO electrode to construct an electrochemical H 2 O 2 sensor by coating nafion polymer. During the catalytic reaction, the peroxidase substrate TMB was oxidized to form the TMB oxidation product, which not only produces a blue color detected by absorbance change, but also generates an electrochemical current. As a result, both spectrophotometric and electrochemical methods were used to determine H 2 O 2 concentration. The spectrophotometric detection displayed a linearity for H 2 O 2 concentration from 10 μM to 5 mM (r2 = 0.989), with an estimated detection limit of 2 μM. In the electrochemical detection, the TMB peak current had a good linear relationship with H 2 O 2 concentration from 10 nM to 10 mM, with an estimated detection limit of 1.9 nM, which was much lower than that of the spectrophotometric method result. [ABSTRACT FROM AUTHOR]

Abstract We developed a novel micro-patterning technique for single-walled carbon nanotubes (SWCNTs) on nitrocellulose (NC) membranes and characterized the mechanical and electrical properties of the patterned SWCNTs. The SWCNT patterns were successfully fabricated on wax-printed NC membrane by a vacuum filtration method within 15 min. The well-deposited SWCNT layer on the NC membrane exhibited strong adhesion and high conductivity due to the interconnection of the SWCNT layer in the porous structure of the NC membrane. The distinguishable patterns were resolved down to approximately 100 μm. The patterned SWCNT had an average resistivity of less than 100 Ω/sq and showed excellent mechanical properties in repeated bending tests. The suitability of the patterned SWCNT electrodes for electronic devices was demonstrated successfully via a simple light emitting diode array. Moreover, for the application of the patterned SWCNT to electrochemical paper-based analytical devices (ePADs), the gold nanoparticles (AuNPs) were directly deposited on the SWCNT electrode for non-enzymatic glucose determination. The oxidation peak had a linear response with glucose concentration in the range between 0.5 and 10 mM. The ePADs exhibited a sensitivity of 240 μA/mM·cm2 and a detection limit of 148 μM, which was derived from the electro-catalytic property of AuNPs toward glucose. Based on these results, we believe that the developed SWCNT patterning technique on paper substrates has great potential in ePADs. Graphical abstract Unlabelled Image Highlights • Micro-patterns of single-walled carbon nanotubes (SWCNTs) were successfully fabricated on wax-printed papers. • AuNPs were deposited on the SWCNT electrodes for the application to electrochemical paper-based analytical devices. • The developed devices were applied successfully to non-enzymatic glucose determination. [ABSTRACT FROM AUTHOR]

We developed electrochemical microfluidic devices containing Au-Ag bimetallic nanoparticles on single-walled carbon nanotube (SWCNT) electrodes for precise, rapid and non-enzymatic electrochemical detection of hydrogen peroxide (H 2 O 2 ). A homogeneous SWCNT layer on a glass substrate was patterned by a standard photolithography method and an O 2 -plasma technique. The patterned SWCNT layers were used as working electrode, counter electrode, and reference electrode in a 1 mm wide and 23 μm deep microchannel. To enhance the electrochemical catalytic properties of the working electrode, Au covered Ag nanoparticles (NPs) were electrochemically deposited on the SWCNT working electrode with current streaming solution into a microfluidic channel. The AgNPs had catalytic activity to improve the reduction of H 2 O 2 combined with AuNPs, which could support catalytic reaction of AgNPs. The reduction in H 2 O 2 in fabricated devices was monitored at an optimized condition and was linear with H 2 O 2 concentration, resulting in a sensitivity of 13.1 μA·cm − 2 ·mM − 1 , a correlation coefficient of r 2 = 0.985, and limit of detection 26.8 μM (S/N = 3). For the analysis of real samples, diluted antiseptic solutions containing 3 wt% H 2 O 2 were used to determine the concentration of H 2 O 2 in the pharmaceutical sample. The recovery values ranged from 97% to 107%, and relative standard deviations were below 5%. We expect that the developed microfluidic sensor is a prospective electrochemical platform for accurate, reproducible non-enzymatic detection of H 2 O 2 . [ABSTRACT FROM AUTHOR]

In the present study, we constructed a functional paper fluidic device and evaluated its electrochemical performance by analyzing acetaminophen in the presence of ascorbic acid. The device was composed of a single-walled carbon nanotube (SWCNT) electrode and nafion-modified nitrocellulose membrane. Negatively-charged nafion was employed to build up a more negative charge on the nitrocellulose membrane, and gold nanoparticles and polyglutamic acid (AuNP-PGA) were deposited on the SWCNT electrode to enhance the electrochemical performance of the device. The device had a vertical flow format in which the sample solution flowed vertically through the paper. Using the nafion-modified nitrocellulose membrane and AuNP-PGA/SWCNT film electrode as a component of the paper fluidic device, we obtained a distinguishable acetaminophen oxidation peak which was distinct from the ascorbic acid oxidation peak. The acetaminophen oxidation peak had a linear response with acetaminophen concentration, varying from 50 μM to 300 μM (r 2 = 0.992), which was broader than the standard drug dose range. The device exhibited a sensitivity of 13.3 mA/M and a detection limit of 15.0 μM. The device was stable with a relative standard deviation of 3.3% (up to 2 weeks), and the reproducibility was 1.2–5.2%. Furthermore, the fabricated device accurately measured the amount of acetaminophen in pharmaceutical samples. [ABSTRACT FROM AUTHOR]

We present a simple method to fabricate flexible, transparent silver nanowire (AgNW) films. Homogenous AgNW networks were formed on a mixed cellulose ester (MCE) membrane by vacuum filtration and were easily transferable to self-adhesive poly(ethylene terephthalate). The opaque, white MCE membrane became transparent after being subjected to hot acetone vapor. The fabricated AgNW films had an average resistivity of 13 Ω/sq and a transmittance of approximately 67%. Moreover, the AgNW films showed excellent mechanical properties in repeated adhesion tests and bending tests. The AgNW films also showed good resistance against heat and NaCl solutions. AgNW films were patterned by a combination of soft lithography and a solution-based chemical etching technique. The area under the photoresist polymer maintained its conductivity and transmittance after etching, whereas increased resistance and transparency were observed in the etched area. The suitability of the patterned AgNW electrodes for electronic devices was demonstrated via a simple LED chip array. After using standard photolithography to define the working area, AgNW films were used as sensor electrodes for the electrochemical detection of hydrogen peroxide (H 2 O 2 ). The AgNW sensors displayed a reasonable detection limit of 46 μM (S/N = 3), a rapid response time (within 2 s), and high sensitivity (749 μA mM −1 cm −2 and 1640 μA mM −1 cm −2 ). Furthermore, the AgNW sensor was resistant to other potential interfering electroactive species commonly present in physiological samples such as l -ascorbic acid, glucose, and sodium oxalate. These results indicate that the AgNW sensor is selective for electroreduction of H 2 O 2 . Additionally, the developed sensor exhibited a stable amperometric response to the reduction of H 2 O 2 even after extended storage. [ABSTRACT FROM AUTHOR]

A novel microfluidic pH-sensing chip was developed based on pH-sensitive single-walled carbon nanotubes (SWCNTs). In this study, the SWCNT thin film acted both as an electrode and a pH-sensitive membrane. The potentiometric pH response was observed by electronic structure changes in the semiconducting SWCNTs in response to the pH level. In a microfluidic chip consisting of a SWCNT pH-sensing working electrode and an Ag/AgCl reference electrode, the calibration plot exhibited promising pH-sensing performance with an ideal Nernstian response of 59.71 mV pH−1 between pH 3 and 11 (standard deviation of the sensitivity is 1.5 mV pH−1, R2 = 0.985). Moreover, the SWCNT electrode in the microfluidic device showed no significant variation at any pH value in the range of the flow rate between 0.1 and 15 μl min−1. The selectivity coefficients of the SWCNT electrode revealed good selectivity against common interfering ions. [ABSTRACT FROM AUTHOR]

Abstract: In this article, urchin-like palladium (Pd) nanostructures were electrochemically deposited onto pre-patterned single-walled carbon nanotube (SWCNT) thin films. X-ray photoelectron spectroscopy and X-ray diffraction techniques were used to characterize the properties of Pd nanostructures on SWCNT thin films. The spherical Pd particles and urchin-like Pd particles were synthesized at −0.5V and +0.1V, respectively. Scanning electron microscope images indicated that the diameters of spherical Pd particles and urchin-like Pd particles were in the range of 50–100nm and 300–400nm, respectively. Cyclic voltammetry was applied to investigate the urchin-like Pd/SWCNT electrode with nitrite oxidation. Results showed that the current response of urchin-like Pd/SWCNT was 1.5 times greater than that of spherical Pd/SWCNT electrodes. The effects of precursor concentration, accumulated charges, pattern size on the morphology of urchin-like Pd structures were also investigated. The urchin-like Pd NPs/SWCNT electrode displayed a suitable detection limit of 0.25μM (S/N =3) under the controlled condition (de-oxygenated buffer solution at pH 4.0) and two linear ranges with respect to nitrite concentration: one from 2μM to 238μM (R 2 =0.995) and the other from 283μM to 1230μM (R 2 =0.998). The corresponding sensitivities were 417μAmM−1 cm−2 and 192μAmM−1 cm−2, respectively. The presence of K+, Na+, Cl−, PO4 3−, NH4 +, CH3COO−, Zn2+, Mg2+, Ca2+, Cd2+, CO3 2−, NO3 −, and SO4 2− showed a negligible effect on the current response of nitrite determination, suggesting that developed sensors have a suitable degree of tolerance to common ions that can cause interference. [Copyright &y& Elsevier]

Abstract: We developed the versatile microfluidic device for on-chip electrochemical analysis in a single integrated platform. Gold nanostructures were fabricated at defined positions within microchannels by electrochemical deposition, and used as electrocatalytic materials for glucose detection and suitable sensing surfaces for ultratrace arsenic(III) detection. The continuous streaming solution in microfluidic devices allowed for enhanced mass transport to the electrodes and elimination of fouling effects, resulting in increased currents and high sensitivities. As a result, the current response showed a strong linear dependence (R 2 =0.995) in the glucose concentration range of 0.1–9mM with an excellent sensitivity of 1.10±0.07mAcm−2 mM−1. Furthermore, in ultratrace arsenic(III) analysis, the calibration plot corresponding to peak current shows good linearity (R 2 =0.998) up to the concentration of 30ppb and remarkable sensitivity of 4.49±1.01μAcm−2 ppb−1 in a short accumulation time of 60s. We believe that the proposed device is a promising approach for various microfluidic applications with the extensibility of functional nanostructures and possibility of biomolecule self-assembly. [Copyright &y& Elsevier]

Abstract: Pt/TiO2 nanohybrids modified single-walled carbon nanotube (SWCNT) electrodes were fabricated using photoinduced deposition coupling with electrochemical deposition, and the fabricated electrodes were then used for the detection of hydrogen peroxide (H2O2). TiO2 particles were deposited electrochemically on SWCNT films and used as supports for photoinduced platinum particles. The morphological and chemical characterizations of the resulting Pt/TiO2/SWCNT nanohybrid structures were examined using scanning electron microscopy, transmission electron microscopy, high-angle annular dark-field scanning transmission electron microscopy, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The electrocatalytic performances of the Pt/TiO2/SWCNT nanohybrid structures toward H2O2 were characterized using cyclic voltammetry and amperometry methods. During photodeposition, pH and Cl− ions in the platinum precursor solution strongly influenced the formation of platinum particles due to the hydrolytic changes of the platinum complexes and the driving force for platinum reduction. These changes affected the chemical compositions and the oxidation states of platinum particles, resulting in different electrocatalytic properties for H2O2. The Pt/TiO2/SWCNT nanohybrid structures with high PtO content ratio provided excellent electrocatalytic performance with high sensitivity (571.7±23.2μAmM−1 cm−2) and a low detection limit (0.73±0.04μM) for H2O2 detection. [Copyright &y& Elsevier]

Abstract: We developed an electrochemical sensor to detect acetaminophen by electrochemically co-depositing glutamic acid and gold nanoparticles on a single-walled carbon nanotube film (AuNP-PGA/SWCNT). Cyclic voltammetry indicated that the electrochemical oxidation of acetaminophen at the AuNP-PGA/SWCNT film electrode involved a two-electron, one-proton process and was pH dependent. Different pulse voltammograms of acetaminophen oxidation on the AuNP-PGA/SWCNT film electrode yielded a well-defined oxidation peak at 360mV in 0.1M phosphate buffered saline buffer (pH 7.2) with linear calibration from 8.3 to 145.6μM (R 2 =0.997). The detection limit was estimated to be 1.18μM. The proposed sensor is stable and reproducible from 1.15 to 5.21% with a relative standard deviation of 3.56%. The AuNP-PGA/SWCNT film electrode was able to detect acetaminophen in the presence of interfering ascorbic acid; two well-defined oxidation peaks, one for ascorbic acid at 0.15V and the other for acetaminophen at 0.39V, were detected. Furthermore, the fabricated sensor accurately measured the amount of acetaminophen in pharmaceutical samples. Together, these results indicate that our AuNP-PGA/SWCNT film is a promising platform for accurate and reproducible detection of acetaminophen. [Copyright &y& Elsevier]

Abstract: Phage display was performed against human IgG (hIgG) through five rounds of ‘biopanning’. Each round consisted of: (1) incubating a library of phage-displayed 12-mer peptides sequences on hIgG-coated magnetic beads, (2) washing the unbound phages, and (3) eluting the bound phages. The eluted phages were either amplified to enrich the pool of positive clones or subjected to the next round without amplification. Through ELISA, four clones (F9, D1, G5, and A10) showing specific binding affinity to hIgG were identified. Among these, F9 had the highest affinity (K d =6.2nM), only one order of magnitude lower than the native anti-hIgG antibody (0.66nM). Following the DNA sequences of the selected clones, four 12-mer peptides were chemically synthesized. Among them, D1 peptide showed the highest binding affinity to hIgG via SPR biosensor measurements. This peptide was conjugated to biofunctionalized magnetic beads, and its immuno-binding ability was compared with that of the native antibody immobilized to magnetic beads. The mol-to-mol binding efficacy of the peptide-coated magnetic beads was approximately 1000-fold lower than that of the antibody-coated magnetic beads. Our results suggest a feasibility of using antibody-mimicking peptides identified by phage display technique for immuno-magnetic separation of an antigen. [Copyright &y& Elsevier]

Abstract: Encapsulation of active proteins in the hydrophilic core of vesicular liposomes is important for developing a therapeutic protein carrier system. The efficiency of liposomal encapsulation of proteins is generally low. A better understanding of the fundamental mechanisms of encapsulation is needed to increase this efficiency. In this study we investigated the effects of operating parameters such as phospholipid concentration, buffer pH and ionic strength, protein size and surface charge, and liposome size on the enzyme encapsulation yield. Four model enzymes of different molecular weights and isoelectric points (trypsin, horseradish peroxidase, enterokinase and hyaluronidase) were encapsulated into three different sized liposomes (125nm, 194nm, and 314nm in mean diameter). Relatively inert and neutral DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) was used as the main phospholipid in the liposomes. Size exclusion chromatography was used to separate the enzyme-encapsulated liposomes from the free enzyme, and the encapsulation yield was determined from the peak area. The encapsulation yield was generally low ranging from ca. 5% to 20%, and did not depend much on the molecular weight of the enzyme encapsulated. Larger liposomes had higher encapsulation yields. The electrostatic interaction between the phospholipid and enzyme was the most significant parameter in determining the encapsulation yield. Thus adjusting buffer pH and ionic strength and adding charged phospholipids to the liposome preparation to impart electric charge to the lipid bilayer could significantly improve the yield. This approach can be used to optimize the liposomal encapsulation of clinically significant proteins. [Copyright &y& Elsevier]

Abstract: Tungsten oxide nanofibers were successfully prepared via thermal treatment of electrospun composite nanofibers consisting of polyvinylpyrrolidone (PVP) and tungstic acid at 500°C in air. The morphology, crystal structure, and chemical composition of the nanofibers were characterized by SEM, EDX, TEM, XRD, and FT-IR before and after the thermal treatment. It was confirmed that the calcination process was responsible for the removal of PVP component and the growth of crystalline WO3. The resulting tungsten oxide nanofibers, which had a rough surface morphology and an average diameter of around 40nm, were found to be formed by the axial agglomeration of prolate spheroid-like WO3 nanoparticles with monoclinic crystalline phases. Gas-sensing measurements of the polycrystalline WO3 nanofiber mats were performed upon exposure to ammonia gas. They demonstrated n-type sensing response and sensitive NH3 detection up to 10ppm with a well-defined relationship between the concentration and detection response at an operating temperature of 300°C. These results were interpreted by applying the space-charge layer model used in the semiconducting metal-oxide sensor systems. [Copyright &y& Elsevier]

Abstract: Platinum nanoparticles (Pt NPs) were grown directly on multiwall carbon nanotubes (MWNTs) using a wet chemical reduction process. Gas permeable Pt NP-supported MWNT (Pt/MWNT) electrodes were then formed on microporous PTFE membranes through the vacuum-filtration of a Pt/MWNT solution. The potential use of these electrodes in amperometric hydrogen sensor applications was assessed. Various material analysis methods such as SEM, TEM and XRD were employed in order to characterize the morphologies and microstructures of the Pt/MWNT nanocomposites. The electrodes exhibited a nanoporous interwoven surface morphology as a result of Pt agglomerates attached to the MWNTs. From the XRD and TEM measurements, individual polygonal Pt NPs were confirmed to have polycrystalline face-centered cubic (fcc) structures and very small particle sizes of 2–7nm. The electrode fabrication process was sequentially optimized by adjusting the MWNT content, H2PtCl6 concentration, NaBH4 concentration, and the drying temperature. At optimized conditions, the Pt/MWNT electrode displayed a high sensitivity greater than 200μA/ppm, a fairly good selectivity to interfering CO species, and an excellent linear response over the wide concentration range of 5–1000ppm. Furthermore, the performances of the electrodes were found to be better than those of binary NP-supported MWNT systems (Pt–Pd/MWNT, Pt–Zn/MWNT, Pt–Ni/MWNT and Pt–ZnO/MWNT). [Copyright &y& Elsevier]

Abstract: This paper reports a highly reproducible immunoassay of cancer markers using surface-enhanced Raman scattering (SERS) imaging. SERS is a highly sensitive detection method but it is limited in its ability to achieve reproducible signal enhancement because of the difficulty with precisely controlling the uniform distribution of hot junctions. Consequently, inconsistent enhancement prevents the wide exploitation of SERS detection as a bio-detection tool for quantitative analysis. To resolve this problem, we explored the use of a SERS imaging-based immunoassay. For this purpose, Raman reporter-labeled hollow gold nanospheres (HGNs), were manufactured and antibodies were immobilized onto their surfaces for targeting specific antigens. After the formation of sandwich immunocomplexes using these functional HGNs on the surfaces of gold patterned wells, the SERS mapping images were measured. For target protein markers, 12×9 pixels were imaged using a Raman mapping technique in the 0–10−4 g/mL concentration range, and the SERS signals for 66 pixels were averaged. Here, the SERS imaging-based assay shows much better correlations between concentration and intensity than does the conventional point-based assay. The limits of detection were determined to be 0.1pg/mL and 1.0pg/mL for angiogenin (ANG) and alpha-fetoprotein (AFP), respectively. This detection sensitivity is increased by three or four orders of magnitude over that of conventional ELISA method. The detectable dynamic range for SERS imaging (10−4–10−12 g/mL) is also much wider than that for ELISA (10−6–10−9 g/mL). [ABSTRACT FROM AUTHOR]

Abstract: In this study, the development of polyethylene glycol (PEG) hydrogel microstructures led to the micropatterning of single-walled carbon nanotube (SWCNT) films. Polyethylene glycol was patterned in a process analogous to photolithography in order to manufacture high-density arrays of micrometer-scale hydrogel wells on SWCNT film surfaces. These microwells were composed of hydrophobic SWCNT films surrounded by hydrophilic PEG hydrogel walls. Effects of PEG hydrogel microstructures on the micropatterning of SWCNT films were systematically investigated under different substrates prepared with 3-(trichlorosilyl)propyl methacrylate or octadecyltrichlorosilane solution. A characterization of protein adsorption and an electrochemiluminescence (ECL) reaction were performed to evaluate the biocompatible and electrical efficiency of the patterned SWCNT films in various applications. The proteins selectively adhered to the SWCNT surface inside the microwells, while adherent proteins were absent from the hydrogel walls. In the ECL reaction, the SWCNT films patterned with PEG hydrogel exhibited good, stable ECL behavior, a sign that patterned SWCNT films can be used as flexible and transparent electrodes. [Copyright &y& Elsevier]

Abstract: Silver particles were patterned on flexible and transparent single-walled carbon nanotube (SWCNT) films using the electrochemical deposition method, and these patterned silver particles were then used as electrodes to detect hydrogen peroxide (H2O2). The sizes and densities of silver particles were tuned by varying the patterned design and the preparation conditions. Field emission-scanning electron microscopy revealed that the patterned silver particles were homogeneously distributed on the single-walled carbon nanotube films (AgPs-SWCNT), with an average size of 150–200nm. X-ray diffraction patterns revealed four peaks, corresponding to a face-centered cubic silver crystal nanostructure. The AgPs-SWCNT sensor displayed a linear electrical response to H2O2 concentrations ranging from 0.016mM to 18.085mM. The detection limit and the sensitivity of the sensor were 2.76μM and 10.92μAmM−1 mm−2, respectively. Furthermore, the AgPs-SWCNT sensor was resistant to l-ascorbic acid as an interferent, indicating that it was selective for the electro-reduction of H2O2. In addition, the developed sensor showed a stable amperometric response to the reduction of H2O2 over an extended period of time. [Copyright &y& Elsevier]

Abstract: We developed glucose biosensing electrodes using single-walled carbon nanotube (SWCNT) films on flexible, transparent poly(ethylene terephthalate). The homogeneous SWCNT films were fabricated by a vacuum filtration method, and the averaged resistivity and transparency of the fabricated flexible SWCNT films were 400Ωsq−1 and 80%, respectively. The glucose sensing electrodes were constructed by encapsulating glucose oxidase (GOx) by Nafion binder into the SWCNT film, and the variation in current response as a function of enzyme loading amount, Nafion thickness were investigated. 30mgmL−1 GOx and 2% Nafion was optimal for the detection of glucose. When ferrocene monocarboxylic acid (FMCA) was introduced as diffusional electron mediator, the current responses toward glucose of the Nafion/GOx/SWCNT electrodes in glucose solution containing FMCA were dramatically improved, and the developed sensor was independent of oxygen. In the application of GOx immobilized SWCNT films for glucose detection, a linear electrical response was observed for concentrations ranging from 0.25 to 3.0mM, and the detection limit and the sensitivity were assessed to be 97μM and 9.32μAmM−1 cm−2, respectively. Moreover, according to the Lineweaver–Burk plot, the apparent Michaelis–Menten constant was calculated to be 23.8mM, and the current responses did not interfere with coexisting electroactive species, indicating that Nafion is an effective permselective polymer barrier. [Copyright &y& Elsevier]

Abstract: The arrays of gold nanoparticles (AuNPs) were fabricated on flexible and transparent single-walled carbon nanotube (SWCNT) films using the electrochemical deposition method, and the patterned nanotubes were then used as electrodes for hydroxylamine detection. The sizes and densities of the AuNPs could easily be controlled by varying the amount of charge deposited, and the gold-deposited area showed a homogeneous distribution on the exposed SWCNT film surface. X-ray diffraction analysis of the AuNPs shows a face-centered cubic structure that is dominated by the lowest energy {111} facets. The oxidation of the hydroxylamine on the AuNP-deposited SWCNT films depended strongly on the solution pH, and the maximum catalytic current was observed at a pH of 9.0. A linear electrical response was observed for concentrations ranging from 0.016 to 0.210mM, and the detection limit and the sensitivity were 0.72μM and 165.90μAmM−1 cm−2, respectively. Moreover, the amperometric response in hydroxylamine showed a stable response for a long time (300s), during which time it retained 94% of its initial value. In the long-term storage stability test, the current response to hydroxylamine decreased slightly, with only 17% leakage after 30days. [Copyright &y& Elsevier]

Abstract: Liposomes were used as templates to prepare size-controlled and monodisperse poly(ethylene glycol) (PEG) hydrogel nanoparticles. The procedure for the preparation of PEG nanoparticles using liposomes consists of encapsulation of photopolymerizable PEG hydrogel solution into the cavity of the liposomes, extrusion through a membrane with a specific pore size, and photopolymerization of the contents inside the liposomes by UV irradiation. The size distributions of the prepared particles were (12%), (14%), and (13%) after extrusion through membrane filters with pore sizes of 1 μm, 400 nm, and 100 nm, respectively. With this approach, it is also possible to modify the surface of the hydrogel nanoparticles with various functional groups in a one-step procedure. To functionalize the surface of a PEG nanoparticle, methoxy poly(ethylene glycol)–aldehyde was added as copolymer to the hydrogel-forming components and aldehyde-functionalized PEG nanoparticles could be obtained easily by UV-induced photopolymerization, following conjugation with poly-l-lysine-FITC through amine–aldehyde coupling. The prepared PEG particles showed strong fluorescence from FITC on the edge of the particles using confocal microscopy. The immobilization of biomaterials such as enzymes in hydrogel particles could be performed with loading β-galactosidases during the hydration step for liposome preparation without additional procedures. The resorufin produced by applying resorufin β-d-galactopyranoside as the substrate showed the fluorescence under the confocal microscopy. [Copyright &y& Elsevier]

Abstract: Single-chain Fv antibody (scFv) having 2 types of polypeptide linkers with or without rare codons, namely scFv (G4S)3 R and scFv No.10 (with rare codons) and scFv (G4S)3 and scFv No.10NR (without rare codon), were expressed under controllable conditions in batch and fed-batch fermentation, in order to compare volumetric productivity and specific productivity levels of scFvs as a soluble form. In batch fermentation, volumetric productivity levels of scFv (G4S)3 R and scFv No.10, namely scFvs having the rare codon linkers were 3–5 times higher than those of scFvs that had linkers without the rare codon. In fed-batch fermentation controlled by an exponential feeding system, the cell concentrations of the transformants increased with similar specific growth rates (0.1 h−1), while the specific productivity levels of scFvs with the rare codon linkers were 1.6 times higher than those of scFvs without the rare codon linkers. These results indicate that the presence of several rare codons in the gene of a polypeptide linker increases soluble amount of scFvs. This might be caused by a temporary decrease in translation speed at the position of the polypeptide linker allowing time for the folding of the VH domain and avoiding unfavorable interactions between amino acid residues at the unfolded VH and VL domains. Higher specific productivity levels of both scFv No. 10 and scFv No. 10NR than those of scFv (G4S)3 R and (G4S)3 might be caused by difference in stability of the polypeptide linkers on the basis of amino acid sequences. Thus, the rare codon linkers tested in this study will be considerably useful for large-scale production of soluble and active scFvs in fed-batch or continuous fermentations, in which high cell activity can be maintained. [Copyright &y& Elsevier]

[Display omitted] • Polyvinylpyrrolidone (PVP) was used to enhance the dispersity and homogeneity of bimetallic nanozymes. • PVP-stabilized PtRu nanozymes (PVP/PtRu NZs) exhibited excellent peroxidase-mimic activity. • Cascade reaction of glucose oxidase and PVP/PtRu NZs was used for colorimetric and fluorometric glucose detection. • Glucose recovery test using human serum and artificial urine showed excellent recovery values. Nanozymes have significant advantages over natural enzymes. The intrinsic peroxidase-like activity of Pt-based nanomaterials can be enhanced by alloying with other transition metals, such as Ru, that have great catalytic activity. In this study, we used polyvinylpyrrolidone (PVP) to synthesize well-dispersed and homogeneous nanostructures. PVP-stabilized Pt-Ru nanozymes (PVP/PtRu NZs) were synthesized and characterized. The PVP/PtRu NZs had an average size of 3.54 ± 0.84 nm and exhibited an intense peroxidase-like activity. The PVP/PtRu NZs were used as peroxidase mimics for colorimetric and fluorometric glucose determination by the glucose oxidase and PVP/PtRu NZs cascade reaction. In the colorimetric assay, the linearly detectable range was 0.25–3.0 mM, with an R2 and limit of detection (LOD) of 0.988 and 138 μM, respectively. In the fluorometric assay, a linear relationship was found when the glucose concentration was between 5.0 and 300 μM (R2 = 0.997), with an LOD of 1.11 μM. Compared to the colorimetric assay, the fluorometric assay had greater sensitivity and a lower detection limit for the determination of glucose. Moreover, the PVP/PtRu NZs had high storage stability over a month and great recovery values in human serum and artificial urine, with a range of 94–106 %. From these results, PVP/PtRu NZs are expected to be used as promising peroxidase mimics in various fields such as biosensing, pharmaceutical processing, and the food industry. [ABSTRACT FROM AUTHOR]

[Display omitted] • An electrochemical cytosensor was developed for SK-MEL 28 cancer cell detection. • The electrical signal intensity of the cancer cell was used to monitor cell viability. • The cytosensor could detect the cancer cells from 2,880 to 40,000 cells per device. • The cytosensor enabled a sensitive and fast assessment of the anticancer effect of saponin. Discovering new anticancer agents and analyzing their activities is a vital part of drug development, but it requires a huge amount of time and resources, leading to the increasing demands for more-effective techniques. Herein, a novel and simple cell-based electrochemical biosensor, referred to as a cytosensor, was proposed to investigate the electrochemical behavior of human skin malignant melanoma (SK-MEL28) cells and the anticancer effect of saponin on cell viability. To enhance both electrocatalytic properties and biocompatibility, gold nanoparticles were electrochemically deposited onto a conductive substrate, and poly-L-lysine was further added to the electrode surface. Electric signals from SK-MEL28 cells on the electrodes were obtained from cyclic voltammetry and differential pulse voltammetry. The cathodic peak current was proportional to the cell viability and showed a detection range of 2,880–40,000 cells per device with an excellent linear cell number-intensity relationship ( R 2 = 0.9952). Furthermore, the anticancer effect of saponin on SK-MEL28 cells was clearly established at concentrations higher than 20 μM , which was highly consistent with conventional assays. Moreover, the developed electrochemical cytosensor for evaluating anticancer effects enabled rapid (<2 min), sensitive (LOQ: 2,880 cells/device), and non-invasive measurements, thus providing a new avenue for assessing the anticancer drugs in vitro. [ABSTRACT FROM AUTHOR]

Abstract: A rapid and highly sensitive trace analysis technique for determining malachite green (MG) in a polydimethylsiloxane (PDMS) microfluidic sensor was investigated using surface-enhanced Raman spectroscopy (SERS). A zigzag-shaped PDMS microfluidic channel was fabricated for efficient mixing between MG analytes and aggregated silver colloids. Under the optimal condition of flow velocity, MG molecules were effectively adsorbed onto silver nanoparticles while flowing along the upper and lower zigzag-shaped PDMS channel. A quantitative analysis of MG was performed based on the measured peak height at 1615cm−1 in its SERS spectrum. The limit of detection, using the SERS microfluidic sensor, was found to be below the 1–2ppb level and this low detection limit is comparable to the result of the LC-Mass detection method. In the present study, we introduce a new conceptual detection technology, using a SERS microfluidic sensor, for the highly sensitive trace analysis of MG in water. [Copyright &y& Elsevier]