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Amino acid arrays comprising bioluminescent amino acid auxotrophic Escherichia coli are effective systems to quantitatively determine multiple amino acids. However, there is a need to develop a method for convenient long-term preservation of the array to enable its practical applications. Here, we reported a potential strategy to efficiently maintain cell viability within the portable array. The method involves immobilization of cells within agarose gel supplemented with an appropriate cryoprotectant in individual wells of a 96-well plate, followed by storage under freezing conditions. Six cryoprotectants, namely dimethyl sulfoxide, glycerol, ethylene glycol, polyethylene glycol, sucrose, and trehalose, were tested in the methionine (Met) auxotroph-based array. Carbohydrate-type cryoprotectants (glycerol, sucrose, and trehalose) efficiently preserved the linearity of determination of Met concentration. In particular, the array with 5% trehalose exhibited the best performance. The Met array with 5% trehalose could determine Met concentration with high linearity (R 2 value = approximately 0.99) even after storage at -20 °C for up to 3 months. The clinical utilities of the Met and Leu array, preserved at -20 °C for 3 months, were also verified by successfully quantifying Met and Leu in spiked blood serum samples for the diagnosis of the corresponding metabolic diseases. This long-term preservation protocol enables the development of a ready-to-use bioluminescent E. coli -based amino acid array to quantify multiple amino acids and can replace the currently used laborious analytical methods.

As a non-covalent interaction of a chiral scaffold in catalysis, pnicogen bonding of epi- cinchonidine ( epi-CD ), a cinchona alkaloid, was simulated to consider whether the interaction can have the potential controlling enantiotopic face like hydrogen bonding. Among five reactive functional groups in epi-CD , two stable complexes of the hydroxyl group (X-epi-CD1) at C 17 and of the quinoline ring (X-epi-CD2) at N 16 with pnictide family analytes [X = substituted phosphine (PX), i.e., F, Br, Cl, CF 3 , CN, HO, NO 2 , and CH 3 , and pnictide family analytes, i.e., PBr 3 , BiI 3 , SbI 3 , and AsI 3 ] were predicted with intermolecular interaction energies, charge transfer (Q Mulliken and Q NBO ), and band gap energies of HOMO-LUMO (Eg) at the B3LYP/6-31G(d,p) level of density functional theory. It was found that the dominant site of pnicogen bonding in epi-CD is the quinoline ring (N 16 atom) rather than the hydroxyl group (O 36 atom). In addition, the UV-Vis spectra of the complex were calculated by time-dependent density functional theory (TD-DFT) at the B3LYP/6-31+G(d,p) level and compared with experimental measurements. Through these calculations, two intermolecular interactions (H-bond vs. pnicogen bond) of epi-CD were compared., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Ullah, Kim, Venkanna, Kim, Kim and Kim.)

The use of composites such as hydroxyapatite (HA)/TiO 2 in bioapplications has attracted increasing attention in recent years. Herein, for the enhancement wetting ability and biocompatibility, the HA/TiO 2 composite was subjected to different treatments to improve nanoparticle (NP) distribution and surface energy with an aim of mitigating nanotoxicity concerns. The treatments included ultrasonication, high-temperature annealing, and addition of a dispersant and surfactant, sodium dodecylbenzenesulfonate (SDBS). Contact angle measurement tests revealed the effect of SDBS addition on the distribution of TiO 2 NPs on the HA surface: a decrease in the contact angle and, thus, an increase in the wetting ability of the HA/TiO 2 composite were observed. The combination of annealing and SDBS addition treatments allowed for guest TiO 2 particles to be uniformly distributed on the surface of the host HA particles, showing a rapid conversion from a hydrophobic to superhydrophilic property. In vitro investigation suggested that the cell viabilities of annealed HA/TiO 2 , SDBS-added HA/TiO 2 , and SDBS-added and annealed HA/TiO 2 reached 89.7%, 94.7%, and 95.8%, respectively, while those of HA and untreated HA/TiO 2 were 80.3% and 86.9%, respectively. The modified composites exhibited lower cytotoxicities than the unmodified systems (HA and HA/TiO 2 ). Furthermore, the cell adhesion behavior of the composites was confirmed through actin-4',6-Diamidino-2-phenylindole (DAPI) staining, which showed negligible changes in the cytoskeleton architecture of the cells. This study confirmed that a modified HA/TiO 2 composite has potential for bioapplications., (© 2021 IOP Publishing Ltd.)

This publisher's note contains corrections to Opt. Lett.45, 6767 (2020)OPLEDP0146-959210.1364/OL.409743.

The ease of the molecular orientation of a chromophore has an important effect on the electro-optical (EO) properties of polymeric photorefractive (PR) composites. A derivative of 4-piperidinobenzylidene-malononitrile (PDCST) with an alkoxy group added as a side branch was synthesized to improve the molecular orientation characteristics. Electrophoresis was performed on the polymeric PR composite to which the improved PDCST had been added. The optical properties and response times were examined to evaluate the effects of the substitution of the alkoxy group. PDCST substituted with the alkoxy group showed enhanced EO properties and a PR grating formation rate.

Nanozymes have drawn significant scientific interest due to their high practical importance in terms of overcoming the instability, complicated synthesis, and high cost of protein enzymes. However, their activity is generally limited to particular pHs, especially acidic ones. Herein, we report that luminescent N, S, and P-co-doped carbon quantum dots (NSP-CQDs) act as attractive peroxidase mimetics in a wide pH range, even at neutral pH, for the peroxidase substrate 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) in the presence of H 2 O 2 . The synergistic effects of multiple heteroatoms doping in CQDs boost the catalytic activity in a wide pH range attributed to the presence of high density of active sites for enzymatic-like catalysis and accelerated electron transfer during the peroxidase-like reactions. A possible reaction mechanism for the peroxidase-like activity of CQDs is investigated based on the radical trapping experiments. Moreover, the multifunctional activity of NSP-CQDs was further utilized for antibacterial assays for both Gram-negative and Gram-positive model species, including Escherichia coli ( E. coli ) and Staphylococcus aureus ( S. aureus ), respectively. The growths of the employed E. coli and S. aureus were found to be significantly inhibited due to the peroxidase-mediated perturbation of cell walls. The present work signifies the current advance in the rational design of N, S, and P-co-doped CQDs as highly active peroxidase mimics for novel applications in diverse fields, including catalysis, medical diagnostics, environmental chemistry, and biotechnology.

Paper-based test strip consisting of cerium oxide nanoparticles (nanoceria) as hydrogen peroxide (H 2 O 2 )-dependent color-changing nanozymes and cholesterol oxidase (ChOx) has been developed for convenient colorimetric determination of cholesterol without the need for chromogenic substrate. The construction of the cholesterol strip begins with physical adsorption of nanoceria on the paper surface, followed by covalent immobilization of ChOx via silanization, chitosan-mediated activation, and glutaraldehyde treatment of the nanoceria-embedded paper matrices. In the presence of cholesterol, ChOx catalyzes its oxidation to produce H 2 O 2 , which forms peroxide complex on the nanoceria surface and induces visual color change of the nanoceria-embedded paper from white/light yellow into intense yellow/orange, which was conveniently quantified with an image acquired by a conventional smartphone with the ImageJ software. Using this strategy, target cholesterol was specifically determined down to 40 μM with a dynamic linear concentration range of 0.1-1.5 mM under neutral pH condition, which is suitable to measure the serum cholesterol, with excellent stability during 20 days and reusability by recovering its original color-changing activity for 4 consecutive cycles. Furthermore, the practical utility of this strategy was successfully demonstrated by reliably determining cholesterol in human blood serum samples. This study demonstrates the potential of self color-changing nanozymes for developing colorimetric paper strip sensor, which is particularly useful in instrumentation-free point-of-care environments., (Copyright © 2020 Nguyen, Kim and Kim.)

We have developed hydrogel nanoparticles made of poly- γ -glutamic acid (PGA) and chitosan, which entraps both glucose oxidase (GOx) and magnetic nanoparticles (MNPs) within the hydrogel matrix. The preparation of poly- γ -glutamic acid/chitosan hydrogel nanoparticles (PGA/CS NPs) entrapping GOx and MNPs begins with the mixing of GOx and MNPs with PGA solution followed by their dropwise addition into chitosan solution to induce rapid ionic gelation. The glucose sensing relies on the generation of H2O2 through the entrapped GOx-mediated catalysis in the presence of glucose, which consequently activates the peroxidase-like activity of MNPs to convert an employed chromogenic substrate, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS), into a green colored product. Using this strategy, the target glucose was successfully detected over a wide linear range, from 5 to 100 μ M with a lower detection limit of 3 μ M, which is sufficient to diagnose high level of glucose (hyperglycemia) in human blood. The hydrogel nanoparticle-based glucose biosensor also showed high stability with magnetic reusability. Since any oxidative enzymes could be incorporated within the PGA/CS NPs, we expect that the hydrogelbased biosensor would be highly beneficial for the detection of various other clinically important target molecules.

A reagent-free colorimetric detection method using mesoporous cerium oxide with a large pore size trapping an oxidative enzyme has been developed and glucose is sensitively detected with a limit of detection of 10 μM by supporting glucose oxidase on mesoporous cerium oxide.

Introduction: Hair growth-promoting herbal extract mixtures (4HGF) exhibits significant anti-inflammatory activities relevant to promoting hair growth; however, its efficacy in patients with hair loss has been limited majorly due to its low penetration ability into hair follicles. Herein, we prepared hydrogels via dropwise addition of poly(γ-glutamic acid) (PGA) solution containing 4HGF into chitosan (CS) solution, resulting in quick formation of ~400 nm-sized hydrogel particles through electrostatic interaction-derived ionic gelation with over 50% encapsulation efficiency of 4HGF (PGA-4HGF)., Methods: The size and morphology of PGA-4HGF were characterized by TEM, SEM, and dynamic light scattering analyses. Encapsulation efficiency and loading capacity of 4HGF within PGA-4HGF, as well as in vitro release profiles were determined by simply measuring the characteristic absorbance of 4HGF. Penetrating efficiency of PGA-4HGF was evaluated by tracking the respective fluorescence through model porcine skin with confocal laser microscope system. By treating PGA-4HGF on telogenic mice and dermal papilla cells (DPCs), we evaluated the size of hair bulbs in mice, as well as morphological changes in DPCs., Results: Negligible and sustained release of entrapped 4HGF from the hydrogel nanoparticles were observed under acidic and physiological pH conditions, respectively, which is quite advantageous to control their release and prolong their hair growth-promoting effect. The hydrogel nanoparticles were penetrable through the porcine skin after incubation with or without shaking. After treating telogenic mice and DPCs with PGA-4HGF, we detected enlargement of hair bulbs and remarkable shape changes, respectively, thereby showing its potential in induction of hair growth., Conclusion: These results suggest that the hydrogel nanoparticle formulation developed in this study can be employed as a potential approach for the preservation of hair growth-promoting compounds, their delivery of into hair follicles, and enhancing hair growth., Competing Interests: The authors report no conflicts of interest in this work., (© 2019 Kim et al.)

We herein describe novel amine-grafted metal-organic frameworks (MOFs) as a promising alternative to natural peroxidase enzyme and their applications for a fluorescent assay of choline (Cho) and acetylcholine (ACh). Among diverse amine-functionalized MOFs, N,N,N',N'-tetramethyl-1,4-butanediamine (TMBDA)-functionalized MIL-100(Fe) (TMBDA-MIL-100(Fe)) exhibited the highest peroxidase activity by developing intense fluorescence from Amplex UltraRed (AUR) in the presence of H 2 O 2 , which was presumably due to the synergetic effect of the enhanced negative potential and precisely controlled molecular size of the grafted diamine. Based on the excellent peroxidase-like activity of TMBDA-MIL-100(Fe), choline and ACh were reliably determined down to 0.027 and 0.036µM, respectively. Furthermore, practical applicability of this strategy was successfully demonstrated by detecting choline and ACh in spiked samples of milk and serum, respectively. This work highlights the advantages of amine-grafted MOFs for the preparation of biomimetic catalysts, extending their scope to biosensor applications., (Copyright © 2017 Elsevier B.V. All rights reserved.)

A label-free colorimetric method for the detection of biological thiols (biothiols) was developed. This method is based on prevention of the photoinduced reduction of auric ions (Au(III)) in the presence of amino acids (acting as a reducing agent) by biothiols; the photoinduced reduction is inhibited due to the strong interaction of the biothiols with Au(III). In this method, the sample was first incubated in an assay solution containing Au(III) and threonine; the sample solution was then exposed to 254 nm UV light. For samples without biothiols, this process led to the photoreduction of Au(III) followed by growth of gold nanoparticles accompanied by the visually detectable development of a red coloration typified by an absorption peak at ca 530 nm. Conversely, in the presence of biothiols, reduction of Au(III) to Au(0) was prevented by entrapment of Au(III) within the biothiols via the thiol group. The solution thus remained colorless even after UV irradiation, which was used as an indicator of the presence of biothiols. Using this strategy, biothiols were very conveniently analyzed by monitoring color changes of the samples with the naked eye or a UV-vis spectrometer. The strategy based on this interesting phenomenon exhibited high selectivity toward biothiols over common amino acids and was successfully employed for reliable quantification of biothiols present in human plasma, demonstrating its great potential for clinical applications.

In this study, a microscale well-plate colorimetric assay for the multiplexed detection of glucose and cholesterol in clinical human blood samples has been developed. This system utilized one-pot nanocomposite entrapping Fe3O4 magnetic nanoparticles (MNPs) as peroxidase mimetics and glucose oxidase (GOx)/cholesterol oxidase (ChOx) in mesoporous silica to detect glucose and cholesterol in blood samples. The sensing mechanism involves the generation of H2O2 by the catalytic action of an immobilized oxidase on the target molecules in the sample. This subsequently activates the MNPs in the mesopores, thereby leading to the conversion of the substrate into a colored end product. This strategy is used to detect the target glucose or cholesterol molecules in the concentration range of 15-250 mg/dL. The response is highly linear and the lower detection limit is 7.5 mg/dL. The aforementioned colorimetric assay is extremely convenient, and it exhibits a high degree of linearity, precision, and reproducibility when employing real human blood samples. Therefore, this assay can be used in clinical practice for the multiplexed and reliable quantification of glucose and cholesterol.

From the synergistic integration and the multidisciplinary strengths of the BioNano Sensor Research Center, Gachon Bionano Research Institute, and Lee Gil Ya Cancer and Diabetes Institute, researchers, students, and faculties at Gachon University in collaboration with other institutions in Korea, Australia, France, America, and Japan have come together to produce a special issue on the diverse applications of nano-theranostics in nanomedicine. This special issue will showcase new research conducted by various scientific groups in Gyonggi-do and Songdo/Incheon, South Korea. The objectives of this special issue are as follows: 1) to bring together and demonstrate some of the latest research results in the field, 2) to introduce new multifunctional nanomaterials and their applications in imaging and detection methods, and 3) to stimulate collaborative interdisciplinary research at both national and international levels in nanomedicine.

An enzyme-mimetic nanoparticle-based point of care bioassay device is developed for rapid and sensitive detection of analytes. Digital images acquired by smart cellular phones allow quantifying the amounts of analytes. Using this new device, quantitative analysis of liquid sample is performed within 15 min with an order of magnitude enhancement of sensitivity compared with conventional Au nanoparticle-based devices., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Nanocomposite to achieve ultrafast immunoassay: a new synergistically integrated nanocomposite consisting of magnetic and platinum nanoparticles, simultaneously entrapped in mesoporous carbon, is developed as a promising enzyme mimetic candidate to achieve ultrafast colorimetric immunoassays. Using new assay system, clinically important target molecules, such as human epidermal growth factor receptor 2 (HER2) and diarrhea-causing rotavirus, can be detected in only 3 min at room temperature with high specificity and sensitivity., (Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A novel, label-free, fluorescent, turn-on sensor for biological thiol detection that uses highly fluorescent gold nanoclusters (AuNCs), prepared by a bovine serum albumin (BSA)-templated green synthetic route, has been developed. The assay relies on blocking Hg(2+)-induced quenching of the fluorescence of AuNCs, caused by metallophilic Hg(2+)-Au(+) interactions, through selective coordination of biological thiols with Hg(2+) ions. Biological thiols entrap added Hg(2+) ions via a robust Hg-S interaction. This phenomenon prevents Hg(2+)-induced quenching and results in fluorescence from AuNCs. By employing this turn-on sensor, biological thiols, such as cysteine (Cys), glutathione (GSH) and homocysteine (Hcy), are successfully detected at concentrations as low as 8.3 nM for Cys, 9.4 nM for GSH, and 14.9 nM for Hcy. The diagnostic capability and potential in practical applications of this method have been demonstrated by detecting biological thiols in human blood serum., (Crown Copyright © 2013. Published by Elsevier B.V. All rights reserved.)

A simple colorimetric immunoassay system, based on the peroxidase mimicking activity of Fe3O4 magnetic nanoparticles (MNPs), has been developed to detect clinically important antigenic molecules. MNPs with ca. 10 nm in diameter were synthesized and conjugated with specific antibodies against target molecules, such as rotaviruses and breast cancer cells. Conjugation of the MNPs with antibodies (MNP-Abs) enabled specific recognition of the corresponding target antigenic molecules through the generation of color signals arising from the colorimetric reaction between the selected peroxidase substrate, 3,3',5,5'-tetramethylbenzidine (TMB) and H2O2. Based on the MNP-promoted colorimetric reaction, the target molecules were detected and quantified by measuring absorbance intensities corresponding to the oxidized form of TMB. Owing to the higher stabilities and economic feasibilities of MNPs as compared to horseradish peroxidase (HRP), the new colorimetric system employing MNP-Abs has the potential of serving as a potent immunoassay that should substitute for conventional HRP-based immunoassays. The strategy employed to develop the new methodology has the potential of being extended to the construction of simple diagnostic systems for a variety of biomolecules related to human cancers and infectious diseases, particularly in the realm of point-of-care applications.

In this study, we developed a colorimetric sensor for the determination of the peroxidase-like activity of Fe-aminoclay, which was used as a novel way of immunoassay for lung cancer was examined. Fe-aminoclay was synthesized by a facile sol-gel reaction under ambient conditions, with both amino sites and Fe surface exposed outside. This Fe-aminoclay, which exhibits strong peroxidase-like activity particularly over a wide pH range, was explored as a robust and rugged replacement of peroxidase enzymes. The peroxidase-like activity of Fe-aminoclay was proved by means of the production of a blue-colored product by 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H₂O₂). This unique activity, in a folic acid-conjugated form, was evaluated for its ability to specifically detect folate receptor-positive A549 cell, which was compared to a human lung normal cell line with lack of the expression of the folate receptor. The chromatic response, which was even detectable by naked eyes, displayed gradational variation, proportional to the number of cells (up to 20,000 cells)., (Copyright © 2012 Elsevier B.V. All rights reserved.)

A nanostructured multicatalyst system consisting of Fe(3)O(4) magnetic nanoparticles (MNPs) as peroxidase mimetics and an oxidative enzyme entrapped in large-pore-sized mesoporous silica has been developed for convenient colorimetric detection of biologically important target molecules. The construction of the nanocomposites begins with the incorporation of MNPs on the walls of mesocellular silica pores by impregnating Fe(NO(3))(3)·9H(2)O, followed by the immobilization of oxidative enzymes. Glutaraldehyde crosslinking was employed to prevent enzymes leaching from the pores and led to over 20 wt% loading of the enzyme. The oxidase in the nanocomposite generates H(2)O(2) through its catalytic action for target molecules and subsequently activates MNPs to convert selected substrates into colored products. Using this strategy, two different biosensing systems were constructed employing glucose oxidase and cholesterol oxidase and their analytical capabilities were successfully verified by colorimetrically detecting the corresponding target molecules with excellent selectivity, sensitivity, reusability, and stability. Future potential applications of this technology range from biosensors to multicatalyst reactors., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Fed-batch cultures of Hansenula polymorpha were studied to develop an efficient biosystem to produce recombinant human serum albumin (HSA). To comply with this purpose, we used high purity oxygen supplying strategy to increase viable cell density in a bioreactor and enhance the production of target protein. A mutant strain, H. polymorpha GOT7 was utilized in this study as a host strain in both 5-L and 30-L scale fermentors. To supply high purity oxygen into a bioreactor, nearly 100 % high purity oxygen from commercial bomb or higher than 93 % oxygen available in-situ from a pressure swing adsorption oxygen generator (PSA) was employed. Under the optimal fermentation of H. polymorpha with high purity oxygen, the final cell densities and produced HSA concentrations were 24.6 g/L and 5.1 g/L in the 5-L fermentor, and 24.8 g/L and 4.5 g/L in the 30-L fermentor, respectively. These were about 2-10 times higher than those obtained in air-based fed-batch fermentations. The discrepancies between the 5-L and 30-L fermentors with air supply were presumably due to the higher contribution of surface aeration over submerged aeration in the 5-L fermentor. This study, therefore, proved the positive effect of high purity oxygen to enhance viable cell density as well as target recombinant protein production in microbial fermentations.

We describe a novel multiplex "amino acid array" for simultaneously quantifying different amino acids based on the rapid growth of amino acid auxotrophic E. coli. First, we constructed genetically engineered amino acid auxotrophs of E. coli containing a bioluminescence reporter gene, yielding concomitant luminescence as a response to cell growth, and then immobilized the reporter cells within individual agarose of respective wells in a 96-well plate serving as a mimic of a biochip. Using the amino acid array, we were able to determine quantitatively the concentrations of 16 amino acids in biological fluid by simply measuring bioluminescent signals from the immobilized cells within 4 h without pre- and post-treatment. The clinical utility of this method was verified by quantifying different amino acids in dried blood spot specimens from clinical samples for the diagnosis of metabolic diseases of newborn babies. This method serves as a convenient route to the rapid and simultaneous analysis of multiple amino acids from complex biological fluids and represents a new analytical paradigm that can replace conventional, yet laborious methods currently in use.