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Graphene-based microfluidic devices can be useful for biosensors and for studying biological systems owing to their comparable length scales and flow characteristics. In sensing and biosensing, the goal in microfluidics research is to develop integrated miniaturized devices capable of achieving high sensitivity and selectivity, rapid response, multiplexing, automation and allow for tests with a small sample volume. In this chapter, a description is presented of fabrication techniques of graphene and derivatives, particularly focused on their possible application in microfluidic devices. A major emphasis is placed on the challenges to reach point-of-care diagnostics, which requires considerably more extensive research as only a few graphene-related studies involving microfluidic devices are available in the literature.

Hemoglobin-containing electrochemical biosensors are useful for detecting hydrogen peroxide through oxidation of the iron ion, but high efficiency can only be reached with appropriate immobilization strategies for hemoglobin. In this work, we combined zein from corn seed with carbon black to immobilize hemoglobin, as proof of concept, and form an electroactive film that could determine hydrogen peroxide within the concentration range from 4.9 × 10−6 to 3.9 × 10−4 mo L−1, and limit of detection of 4.0 × 10−6 mol L−1, using differential pulse voltammetry. The biosensor could also detect hydrogen peroxide in commercial samples of oxygenated water, synthetic serum (physiological and glycoside) and milk. The high performance is ascribed to the large surface area and conductive nature of the porous film that had carbon black and hemoglobin anchored on zein microspheres, according to scanning and transmission electron microscopies. It is significant that a protein from renewable sources (zein) combined with a low-cost carbon material (carbon black) serves as matrix for immobilization of biomolecules.

The controlled assembly of metal nanoparticles into ordered structures interacting with biological molecules is an emerging concept in surface science. Here, bare magnetite nanoparticles (Fe3O4–NPs...

Artepillin C is the major constituent of green propolis, one of the most consumed products in popular medicine owing to its therapeutic effects, including antitumor activity. Artepillin C differs from other cinnamic acid derivatives due to the presence of two prenylated groups in its structure, believed to enhance access to the cell membrane and resulting in pharmacological activity. The membrane outer leaflet of tumor cells is exposed to an acidic extracellular environment, which could modulate the protonation state of antitumor drugs and hence their interaction with the cell membrane. Herein, we investigated the interaction of Artepillin C with Langmuir monolayers and giant unilamellar vesicles (GUVs) of 1,2‑dipalmitoyl‑sn‑glycerol‑3‑phosphocholine (DPPC) used as model membranes, in physiological and acidic environments. We observed that protonation of the carboxyl group of Artepillin C is essential for the interaction, with larger shifts induced in the surface pressure isotherms of DPPC monolayers in comparison with deprotonated Artepillin C. Also observed was a decrease in lipid packing inferred from the compressibility modulus and Brewster angle microscopy (BAM) images for monolayers on acidic subphases. Results with microscopy techniques on GUVs confirmed that. Artepillin C causes a curvature stress of the lipid bilayer only in its neutral state, causing the GUVs to burst. The stronger effects of neutral Artepillin C on both monolayers and GUVs were maintained when the ionic strength was increased. Taken together, the results indicate that Artepillin C may have preferential attachment to a more acidic environment which might be an important feature for its antitumor activity.

Optical devices are today based mainly on glass or synthetic polymers, which hinders their use in biological interfaces owing to the lack of biocompatibility and biodegradability. This is why synthetic plastics are progressively being replaced by their bioplastic counterparts, thus bringing new challenges associated with processability, environmental sustainability, and large-scale fabrication of successful products. Natural polymers or biopolymers are fascinating self-assembled block polymer structures of nearly unlimited and inexpensive renewable resources, now finding applications in various fields, including optics. The ability to control the assembly and conformation of natural polymers into optical quality solutions and films brings the opportunity to revisit their application usually restricted to packaging and medical area. Of particular importance is to combine these polymers with metallic nanoparticles whose tunable localized surface plasmon resonance can be exploited in engineering composite materials with enhanced optical properties. The combined advantages also make them an ideal integration platform to foster biodegradable, bioresorbable, environmentally friendly, and sustainable electronic and optoelectronic devices. This chapter provides comprehensive coverage of advances and trends of how natural polymers and natural polymer-metallic nanoparticle composites have been explored for developing optical devices such as colorimetric sensors, transparent electrodes, optical waveguides, and light amplification devices. Examples will be given of optical composites made of chitin and chitosan, bacterial cellulose, silk fibroin, and DNA, with special emphasis on the challenges and ongoing efforts to fabricate useful devices.

The combination of nanoarchitectonics with microfluidic systems in analytical devices has brought about an innovative platform for sensing and biosensing. This chapter provides a general overview of materials and fabrication techniques in nanoarchitectonics, especially for bridging the gap between proof-of-principle experiments and commercialization. Emphasis is placed on biosensing based on impedance spectroscopy and electrochemical techniques for detecting proteins, genes and biomarkers, where microfluidics offers advantages such as low cost, automation, miniaturization, and high performance in terms of sensitivity and selectivity. Of special importance is the integration of microfluidic systems with diagnostic applications for point-of-care devices, which can also be envisaged with multiplexed detection in a single chip.

This work reports on a low cost microfluidic electronic tongue (e-tongue) made with carbon interdigitated electrodes, printed on paper, and coated with boronic acid-containing hydrogels. Using capacitance measurements, the e-tongue was capable of distinguishing between different types of sugars (e.g. glucose, fructose and sucrose), in addition to distinguishing between commercial brands of apple juice using a small volume of sample (6 μL). The channels of the microfluidic e-tongue were made using a wax printer, and were modified with hydrogels containing acrylamide copolymerized with 5 or 20 mol% 3-(acrylamido) phenyl boronic acid (Am-PBA), or a crosslinked homopolymeric hydrogel based on N-(2-boronobenzyl)-2-hydroxy-N,N-dimethylethan-1-aminium-3-sulfopropyl acrylate (DMA-PBA). Such hydrogels, containing a phenyl boronic acid (PBA) moiety, can bind saccharides. Combining various hydrogels of this nature in an e-tongue device enabled discrimination between apple juices, which are known to contain higher amounts of fructose compared to glucose or sucrose. Changes in capacitance were captured with impedance spectroscopy in the frequency range from 0.1 to 10 MHz for solutions with varying concentrations of glucose, fructose and sucrose (from 0 to 0.056 g mL-1). The capacitance data were treated with Principal Component Analysis (PCA) and Interactive Document Map (IDMAP), which then correlated overall sugar content from different brands of apple juice. This low-cost, easy-to-use, disposable e-tongue offers great potential in the routine analysis of food and beverages, while offering comparative performance to alternatives in the literature.

Nanostructured capacitive biosensors, combined with inexpensive fabrication technologies, may provide simple, sensitive devices for detecting clinically relevant cancer biomarkers. Herein, we report a novel platform for detecting the pancreatic cancer biomarker CA19-9 using low-cost screen-printed interdigitated electrodes (SPIDEs). The SPIDEs were modified by carbon nano-onions (CNOs) and graphene oxide (GO) films, on which a layer of anti-CA19-9 antibodies was immobilized. The modification with CNOs and GO significantly improved the analytical performance of the biosensor, which displayed superior results to those prepared only with GO. The biossensor exhibited high reproducibility and a relatively low limit of detection of 0.12 U mL-1. Using these devices in combination with information visualization methods we were able to detect CA19-9 in whole cell lysates of colorectal adenocarcinoma. The fabrication of these low-cost, disposable immunosensors is a successful attempt to explore CNOs in capacitive biosensors, which may be extended for detection of different cancer biomarkers., CAPES (001), CNPq, INEO and FAPESP (2012/15543-7, 2013/14262-7, 2015/01770-0, 2016/00991-5 and 2017/12096-3). M.N.C is grateful for the economic support from Vicerrectoria de Investigaciones and the Centro de Excelencia en Nuevos Materiales (CENM) from the Universidad del Valle.

Outbreaks of foodborne diseases demand simple, rapid techniques for detecting pathogenic bacteria beyond the standard methods that are not applicable to routine analysis in the food industry and in the points of food consumption. In this work, we developed a sensitive, rapid and low-cost assay for detecting Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Salmonella typhimurium (S. typhi) in potable water and apple juice. The assay is based on electrical impedance spectroscopy measurements with screen-printed interdigitated electrodes coupled with magnetite nanoparticles functionalized with the antimicrobial peptide melittin (MLT). The data were analyzed with the information visualization methods Sammon's Mapping and Interactive Document Map to distinguish samples at two levels of contamination from food suitable for consumption. With this approach it has been possible to detect E. coli concentration down to 1 CFU mL−1 in potable water and 3.5 CFU mL−1 in apple juice without sample preparation, within only 25 min. This approach may serve as a low-cost, quick screening procedure to detect bacteria-related food poisoning, especially if the impedance data of several sensing units are combined.

Cell membrane models have been used to evaluate the interactions of various imidazolium-based ionic liquids (ILs) with Langmuir monolayers of two types of phospholipids and cholesterol. Data from surface pressure isotherms, Brewster angle microscopy (BAM) and polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) pointed to significant effects on the monolayers of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and cholesterol, used to mimic the membranes of eukaryotic cells, for ILs containing more than 6 carbon atoms in the alkyl chain (i.e. n > 6). For ILs with less hydrophobic tails (n ≤ 6) and low concentrations, the effects were almost negligible, therefore, such ILs should not be toxic to eukaryotic cells. The hydrophobicity of the anion was also proved to be relevant, with larger impact from ILs containing tetrafluoroborate ([BF4]-) than chloride (Cl-). Molecular dynamics simulations for DPPC monolayers at the surface of aqueous solutions of alkylimidazolium chloride ([Cnmim]Cl) confirm the penetration of the IL cations with longer alkyl chains into the phospholid monolayer and provide information on their location and orientation within the monolayer. For monolayers of dipalmitoylphosphatidyl glycerol (DPPG), which is negatively charged like bacteria cell membranes, the ILs induced much larger effects. Similarly to the results for DPPC and cholesterol, effects increased with the number of carbon atoms in the alkyl chain and with a more hydrophobic anion [BF4]-. Overall, the approach used can provide relevant information of molecular-level interactions behind the toxicity mechanisms and support the design of (quantitative) structure-activity relationship models, which may help design more efficient and environmentally friendly ILs. published

The recent development of silver nanostars (Ag-NSs) is promising for improved surface-enhanced sensing and spectroscopy, which may be further exploited if the mechanisms behind the excitation of localized surface plasmon resonances (LSPRs) are identified. Here, we show that LSPRs in Ag-NSs can be obtained with finite-difference time-domain (FDTD) calculations by considering the nanostars as combination of crossed nanorods (Ag-NRs). In particular, we demonstrate that an apparent tail at large wavelengths ( &lambda, ≳ 700 nm) observed in the extinction spectra of Ag-NSs is due to a strong dipolar plasmon resonance, with no need to invoke heterogeneity (different number of arms) effects as is normally done in the literature. Our description also indicates a way to tune the strongest LSPR at desired wavelengths, which is useful for sensing applications.

Membrane structure is a key factor for the cell`s physiology, pathology, and therapy. Evaluating the importance of lipid species such as N-nervonoyl sphingomyelin (24:1-SM) -able to prevent phase separation- to membrane structuring remains a formidable challenge. This is the first report in which polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS) is applied to investigate the lipid-lipid interactions in 16:0 vs 24:1-SM monolayers and their mixtures with 1,2-Dioleoyl-sn-glycero-3-phosphocholine (DOPC) and cholesterol (Chol) (DOPC/SM/Chol 2:1:1). From the results we inferred that the cis double bond (Δ15) in 24:1-SM molecule diminishes intermolecular H-bonding and chain packing density compared to that of 16:0-SM. In ternary mixtures containing 16:0-SM, the relative intensity of the two components of the Amide I band reflected changes in the H-bonding network due to SM-Chol interactions. In contrast, the contribution of the main components of the Amide I band in DOPC/24:1-SM/Chol remained as in 24:1-SM monolayers, with a larger contribution of the non-H-bonded component. The most interesting feature in these ternary films is that the CO stretching mode of DOPC appeared with an intensity similar to that of SM Amide I band in DOPC/16:0-SM/Chol monolayers (a two-phase [Lo/Le] system), whereas an extremely low intensity of the CO band was detected in DOPC/24:1-SM/Chol monolayers (single Le phase). This is evidence that the unsaturation in 24:1-SM affected not only the conformational properties of acyl chains but also the orientation of the chemical groups at the air/water interface. The physical properties and overall H-bonding ability conferred by 24:1-SM may have implications in cell signaling and binding of biomolecules., Instituto de Investigaciones Bioquímicas de La Plata, Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas

Just Accepted Manuscript, High-risk human papillomavirus (HPV) infection, mainly with HPV16 type, has been increasingly considered as an important etiologic factor in head and neck cancers. Detection of HPV16 is therefore crucial for these types of cancer, but clinical tests are not performed routinely in public health systems owing to the high cost and limitations of the existing tests. In this article, we report on a potentially low-cost genosensor capable of detecting low concentrations of HPV16 in buffer samples and distinguishing, with high accuracy, head and neck cancer cell lines according to their HPV16 status. The genosensor consisted of a microfluidic device that had an active layer of a HPV16 capture DNA probe (cpHPV16) deposited onto a layer-by-layer film of chitosan and chondroitin sulfate. Impedance spectroscopy was the principle of detection utilized, leading to a limit of detection of 10.5 pM for complementary ssDNA HPV16 oligos (ssHPV16). The genosensor was also able to distinguish among HPV16+ and HPV16- cell lines, using the multidimensional projection technique interactive document mapping. Hybridization between the ssHPV16 oligos and cpHPV16 probe was confirmed with polarization-modulated infrared reflection-absorption spectroscopy, where PO2 and amide I and amide II bands from adenine and thymine were monitored. The electrical response could be modeled as resulting from an adsorption process represented in a Freundlich model. Because the fabrication procedures of the microfluidic devices and genosensors and the data collection and analysis can be implemented at low cost, the results presented here amount to a demonstration of possible routine screening for HPV infections., CNPq (150985/2017-7), FAPESP (2013/14262-7) and Barretos Cancer Hospital, info:eu-repo/semantics/publishedVersion

Plasmonic biosensing has been used for fast, real-time, and label-free probing of biologically relevant analytes, where the main challenges are to detect small molecules at ultralow concentrations and produce compact devices for point-of-care (PoC) analysis. This review discusses the most recent, or even emerging, trends in plasmonic biosensing, with novel platforms which exploit unique physicochemical properties and versatility of new materials. In addition to the well-established use of localized surface plasmon resonance (LSPR), three major areas have been identified in these new trends: chiral plasmonics, magnetoplasmonics, and quantum plasmonics. In describing the recent advances, emphasis is placed on the design and manufacture of portable devices working with low loss in different frequency ranges, from the infrared to the visible.

Made available in DSpace on 2018-12-11T17:37:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-07-15 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Disperse Orange 37 (DO37) is an efficient azo dye for dyeing synthetic textile materials owing to its resistance to degradation that may also be harmful to humans as DO37 is not entirely eliminated in wastewater treatment. In this paper, we demonstrate that DO37 is bleached by reduced glutathione (GSH) in a reaction catalyzed by glutathione-s-transferase (GST), a phase II detoxification enzyme. The reaction included a nucleophilic attack involving sulfhydryl groups, confirmed using density functional theory (DFT) calculations. DO37 also induced quenching in the fluorescence of GST through static suppression. The reaction was determined using differential pulse voltammetry (DPV) by monitoring the oxidation peak at 0.65 V of GSH sulfhydryl group. Quantitative estimation of the product reaction could be made by measuring an additional oxidation peak at 0.91 V which increased linearly with DO37 concentration. These electrochemical determinations were made possible by preconcentrating the reaction product on a graphite-epoxy electrode with immobilization of GST onto magnetite nanoparticles. Straightforward biological implications from the results are associated with the known toxicity of azo dyes such as DO37, which has been proven here to interact strongly with both GSH and the liver enzyme GST, and may induce hepatocarcinogenesis or other types of cancer. Institute of Chemistry São Paulo State University (UNESP) São Carlos Institute of Physics University of São Paulo, P.O Box 369 Institute of Chemistry Autonomous University of Barcelona (UAB) Institute of Chemistry São Paulo State University (UNESP) FAPESP: 2012/15543-7 FAPESP: 2013/14262-7 FAPESP: 2016/00991-5

The need for analytical devices for detecting cancer at early stages has motivated research into nanomaterials where synergy is sought to achieve high sensitivity and selectivity in low-cost biosensors. In this study, we developed a film architecture combining self-assembled monolayer (SAM) and layer-by-layer (LbL) films of polysaccharide chitosan and the protein concanavalin A, on which a layer of anti-CA19-9 antibody was adsorbed. Using impedance spectroscopy with this biosensor, we were capable of detecting low concentrations of the antigen CA19-9, an important biomarker for pancreatic cancer. The limit of detection of 0.69U/mL reached is sufficient for detecting pancreatic cancer at very early stages. The selectivity of the biosensor was inferred from a series of control experiments with samples of cell lines that were tested positive (HT29) and negative (SW620) for the biomarker CA19-9, in addition to the lack of changes in the capacitance value for other analytes and antigen that are not related to this type of cancer. The high sensitivity and selectivity are ascribed to the very specific antigen-antibody interaction, which was confirmed with PM-IRRAS and atomic force microscopy. Also significant is that used information visualization methods to show that different cell lines and commercial samples containing distinct concentrations of CA19-9 and other analytes can be easily distinguished from each other. These computational methods are generic and may be used in optimization procedures to tailor biosensors for specific purposes, as we demonstrated here by comparing the performance of two film architectures in which the concentration of chitosan was varied.

We report on a phenomenological, theoretical model to calculate the rate constants and activation energies for the thermal conversion reactions from poly(xylylidene tetrahydrothiophenium chloride) (PTHT) into poly(p-phenylenevinylene) (PPV) using the optical absorption spectra of spin-coated films. The probabilities of electron transitions were calculated considering Franck-Condon states with a Gaussian distribution of conjugated segments and molecular excitons. The dependence on the conjugation degree (n) for the energy gap, transition dipole moment, and electron-phonon coupling were obtained semiempirically using published data for PPV. Fitting was performed for the C-C stretching of the aromatic ring 1550 cm(-1), for it is considered the most optically active. The isotherms for consumption and formation of PPV segments were fitted using a first-order and consecutive reactions, respectively. With this modeling we could identify the most probable reactions, where the formation of longer PPV segments n ≥ 3 occurs only via reactions from smaller conjugated segments (i.e., n = 1 and 2). The activation energies tend to decrease with longer conjugation lengths. Significantly, the modeling allows us to predict the conversion temperature and chemical composition yielding a predefined distribution of conjugated segments, which can be applied to any polymer undergoing thermal conversion, decomposition, or photo-oxidation.

The disinfectant activity of poly(hexamethylene biguanide) (PHMB) has been explored in industrial applications, in agriculture and in food manipulation, but this biocide action is not completely understood. It is believed to arise from electrostatic interactions between the polyhexanide group and phosphatidylglycerol, which is the main phospholipid on the bacterial membrane. In this study, we investigated the molecular-level interactions between PHMB and dipalmitoyl phosphatidylglycerol (DPPG) in Langmuir monolayers that served as cell membrane models. PHMB at a concentration of 2 × 10 −4 g L −1 in a Theorell–Stenhagen at pH 3.0 and in a phosphate at pH 7.4 was used as a subphase to prepare the DPPG monolayers. Surface pressure–area isotherms showed that PHMB adsorbs and penetrates into the DPPG monolayers, expanding them and increasing their elasticity under both conditions examined. Results from polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) indicated that PHMB induces disorder in the DPPG chains and dehydrates their C O groups, especially for the physiological medium. Overall, these findings point to hydrophobic interactions and dehydration being as relevant as electrostatic interactions to explain changes in membrane fluidity and permeability, believed to be responsible for the biocide action of PHMB.

The need for early detection of various diseases, including breast cancer, has motivated research into nanomaterials that can be assembled in organized films which serve as biosensors. Owing to the variety of possible materials and film architectures, procedures are required to design optimized biosensors. In this study, we combine surface-specific methods to monitor the assembly of antibodies on nanostructured films with two distinct architectures. In the first, a layer of the antibody type mouse anti-HER2 (clone tab250) was immobilized on a self-assembled monolayer (SAM) of 11-mercaptoundecanoic acid modified with N-hydroxysuccinimide (NHS) and 1-ethyl-3-(3-(dimethylamino)propyl)carbodiimide (EDC). In the second approach, a SAM of cysteamine was coated with a biotin/spreptavidin bilayer on which a layer of biotinylated antibody type MSx2HUp185/her biotin was adsorbed. The rougher, less passivating coating with cysteamine determined from cyclic voltammetry and scanning electron microscopy led to biosensors that are more sensitive to detect the breast cancer ERBB2 (HER2) biomarker in impedance spectroscopy measurements. This higher distinguishing ability of the cysteamine-containing film architecture was proven with information visualization methods to treat the impedance data. Polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) confirmed that biosensing resulted from the antibody-ERBB2 antigen affinity.

The use of nanomaterials as an electroactive medium has improved the performance of bio/chemical sensors, particularly when synergy is reached upon combining distinct materials. In this paper, we report on a novel architecture comprising electrospun polyamide 6/poly(allylamine hydrochloride) (PA6/PAH) nanofibers functionalized with multiwalled carbon nanotubes, used to detect the neurotransmitter dopamine (DA). Miscibility of PA6 and PAH was sufficient to form a single phase material, as indicated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), leading to nanofibers with no beads onto which the nanotubes could adsorb strongly. Differential pulse voltammetry was employed with indium tin oxide (ITO) electrodes coated with the functionalized nanofibers for the selective electrochemical detection of dopamine (DA), with no interference from uric acid (UA) and ascorbic acid (AA) that are normally present in biological fluids. The response was linear for a DA concentration range from 1 to 70 μmol L(-1), with detection limit of 0.15 μmol L(-1) (S/N = 3). The concepts behind the novel architecture to modify electrodes can be potentially harnessed in other electrochemical sensors and biosensors.

Fast, simple inspection of liquids such as coffee, wine and body fluids is highly desirable for food, beverage and clinical analysis. Electronic tongues are sensors capable of performing quantitative and qualitative measurements in liquid substances using multivariate analysis tools. Earlier attempts to fulfil this task using only a few drops (microliters) of sample did not yield rational results with non-electrolytes e.g. sucrose (sweetness). We report here the fabrication and testing of a microfluidic e-tongue able to distinguish electrolytes from non-electrolytes, covering also the basic tastes relevant to human gustative perception. The sensitivity of our device is mainly attributed to the ultrathin nature of an array formed by non-selective sensing units. The electronic tongue is composed of an array of sensing units designed with a microchannel stamped in a poly(dimethylsiloxane) (PDMS) matrix and sealed onto gold interdigitated electrodes (IDEs). The IDEs are then coated in situ with a 5-bilayer film deposited by the layer-by-layer (LbL) technique. The cationic layer is derived from polyallylamine chloride (PAH). The anionic layer is either poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) PEDOT:PSS, polypyrrole or nickel tetrasulfonated phthalocyanine. When compared to a conventional electronic tongue our system is three times faster and requires only microliters of sample. Applying Principal Component Analysis to the data yields a high correlation for all substances tested. This microfluidic e-tongue has the potential for producing low-cost, easily integrated, multi-functional sensor for food, beverages, in addition to clinical and environmental applications.

The envisaged ubiquitous sensing and biosensing for varied applications has motivated materials development toward low cost, biocompatible platforms. In this paper, we demonstrate that carbon nanodiamonds (NDs) can be combined with potato starch (PS) and be deposited on a glassy carbon electrode (GCE) in the form of a homogeneous, rough film, with electroanalytical performance tuned by varying the relative ND-PS concentration. As a proof of concept, the ND/PS film served as matrix to immobilize tyrosinase (Tyr) and the resulting Tyr-ND-PS/GCE biosensor was suitable to detect catechol using differential pulse voltammetry with detection limit of 3.9 × 10−7 mol L−1 in the range between 5.0 × 10−6 and 7.4 × 10−4 mol L−1. Catechol could also be detected in river and tap water samples. This high sensitivity, competitive with biosensors made with more sophisticated procedures and materials in the literature, is attributed to the large surface area and conductivity imparted by the small NDs (

Made available in DSpace on 2018-12-11T16:54:53Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-11-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Photodynamic therapy (PDT) efficiency depends on many factors including the incorporation of the photosensitizer (PS) in cell membranes and possible lipid hydroperoxidation. In this study, we show that hydroperoxidation may be photoinduced when eosin Y is incorporated into Langmuir monolayers that serve as cell membrane models. This occurs for Langmuir monolayers of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), which have unsaturation in their hydrophobic chains. In contrast, light irradiation had no effect on monolayers of saturated 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC). Evidence of hydroperoxidation was obtained from the area increase in eosin-containing DOPC and POPC monolayers upon irradiation, which was accompanied by a decrease in monolayer thickness according to grazing incidence X-ray off-specular scattering (GIXOS) data. Furthermore, the changes in polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) induced by irradiation were consistent with hydroperoxide migration toward the lipid hydrophilic heads. In summary, this combination of experimental methods allowed us to determine the effects of eosin Y interaction with cell membrane models under irradiation, which may be associated with the underlying mechanisms of eosin Y as photosensitizer in PDT. School of Sciences Humanities and Languages São Paulo State University (UNESP) Brazilian Synchrotron Light Laboratory-LNLS CNPEM, Rua Giuseppe Maximo Scolfaro, 10000 IFSC São Carlos Institute of Physics University of São Paulo (USP) School of Sciences Humanities and Languages São Paulo State University (UNESP) FAPESP: 2013/14262-7 FAPESP: 2016/13280-0 FAPESP: 2017/13404-3 CNPq: 403713/2016-1

In this paper, we discuss the relevance of sensing and biosensing for the ongoing revolution in science and technology as a product of the merging of machine learning and Big Data into affordable technologies and accessible everyday products. Possible scenarios for the next decades are described with examples of intelligent systems for various areas, most of which will rely on ubiquitous sensing. The technological and societal challenges for developing the full potential of such intelligent systems are also addressed.

Advances in nanomaterials have led to tremendous progress in different areas with the development of high performance and multifunctional platforms. However, a relevant gap remains in providing the mass-production of these nanomaterials with reproducible surfaces. Accordingly, the monitoring of such materials across their entire life cycle becomes mandatory to both industry and academy. In this paper, we use a microfluidic electronic tongue (e-tongue) as a user-friendly and cost-effective method to classify nanomaterials according to their surface chemistry. The chip relies on a new single response e-tongue with association of capacitors in parallel, which consisted of stainless steel microwires coated with SiO2, NiO2, Al2O3, and Fe2O3 thin films. Utilizing impedance spectroscopy and a multidimensional projection technique, the chip was sufficiently sensitive to distinguish silica nanoparticles and multiwalled carbon nanotubes dispersed in water in spite of the very small surface modifications induced by ...

We present a nonlinear transfer matrix method for studying the second-harmonic generation (SHG) in nonperiodic metamaterial photonic superlattices. A large enhancement of up to 5 orders of magnitude in SHG efficiency was observed for superlattices made with a Cantor-like quasiperiodic assembly of a nonlinear material and a metamaterial. The enhancement was found to depend much more on the electric field amplitude along the structure because of self-similarity effects than on the amount of nonlinear material, which opens the way to design superlattices for tailored applications in broad-band tunable lasers.

We demonstrate that the excitation of magnetic bulk plasmon-like resonances in μ-near-zero double-negative metamaterial slabs is suitable for the design of new sensing platforms, where light-to-plasmon coupling is reached without requiring a prism or grating coupler. This allows for excitation with light coming directly from the air and for dielectric substrates with any refractive index. In the microwave region this architecture is able to detect changes as small as 10 − 2 in the refractive index of the superstrate. If the metamaterial slab is backed by a metallic substrate, on the other hand, the system can be used as a light-absorber for light harvesting applications.

Accepted Manuscript, The challenge of the early diagnosis of pancreatic cancer in routine clinical practice requires low-cost means of detection, and this may be achieved with immunosensors based on electrical or electrochemical principles. In this paper, we report a potentially low-cost immunosensor built with interdigitated gold electrodes coated with a self-assembled monolayer and a layer of anti-CA19-9 antibodies, which is capable of detecting the pancreatic cancer biomarker CA19-9 using electrical impedance spectroscopy. Due to specific, irreversible adsorption of CA19-9 onto its corresponding antibody, according to data from polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS), the immunosensor is highly sensitive and selective. It could detect CA19-9 in commercial samples with a limit of detection of 0.68 U mL−1, in addition to distinguishing between blood serum samples from patients with different concentrations of CA19-9. Furthermore, by treating the capacitance data with information visualization methods, we were able to verify the selectivity and robustness of the immunosensor with regard to false positives, as the samples containing higher CA19-9 concentrations, including those from tumor cells, could be distinguished from those with possible interferents., CAPES, FAPESP (Grant 2013/14262-7 and 2012/15543-7), CNPq (150985/2017-7), nBioNet network and Barretos Cancer Hospital for financial support, info:eu-repo/semantics/publishedVersion

Made available in DSpace on 2018-11-26T22:40:49Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-10-01. Added 1 bitstream(s) on 2019-10-09T18:27:55Z : No. of bitstreams: 1 S0103-50532018001002054.pdf: 1875083 bytes, checksum: d412309b2dfc7b515b1a8e8b893b7ce1 (MD5) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) LMF/LNNano, Brazil Immunosensors based on impedance spectroscopy for diagnosing hepatitis C are reported where the sensing units were made with the antigenic peptide PPLLESWKDPDYVPPWHG (NS5A-1) derived from the NS5A protein of the hepatitis C virus (HCV) immobilized in layer-by-layer (LbL) films with silk fibroin (SF) and deposited on gold interdigitated electrodes. The electrical response of the sensing units varied upon immersion into solutions containing the antibody anti-HCV owing to the biomolecular recognition of NS5A-1. This was associated with morphological changes on the LbL films caused by adsorption of NS5A-1 and inferred from atomic force microscopy images. Buffer solutions with different anti-HCV concentrations down to 2 ng mL(-1) could be clearly distinguished by analyzing the impedance spectroscopy data with a multidimensional projection technique. The specificity toward anti-HCV antibodies was confirmed in control experiments where no significant changes in the electrical response were measured by exposing the sensing units to solutions containing an anti-human immunodeficiency virus (HIV) antibody. The high sensitivity and selectivity of the units made with LbL films demonstrate the feasibility of measuring electrical impedance as an immunosensing strategy to detect hepatitis C. Univ Estadual Paulista, Inst Quim, BR-14800060 Araraquara, SP, Brazil Univ Fed Mato Grosso do Sul, Inst Fis, CP-549, BR-79070900 Campo Grande, MS, Brazil Univ Sao Paulo, Inst Ciencias Matemat & Comp, BR-13566590 Sao Carlos, SP, Brazil Univ Sao Paulo, Inst Fis Sao Carlos, BR-13566590 Sao Carlos, SP, Brazil Univ Fed Sao Paulo, Inst Ciencia & Tecnol, BR-12231280 Sao Jose Dos Campos, SP, Brazil Univ Estadual Paulista, Inst Quim, BR-14800060 Araraquara, SP, Brazil CAPES: 26 LMF/LNNano, Brazil: LMF 12298

Taste masking is an important strategy for improving adherence of patients, especially children, who have to take pharmaceutical drugs with a bitter taste, as is the case of praziquantel (PZQ) used to treat schistosomiasis. In this work, a modified interfacial polymer deposition method was used to prepare polymer microcapsules and microspheres to encapsulate PZQ, where formulations were optimized to fulfill the stringent requirements for controlled drug release. In vitro release tests confirmed the suitability of the formulation with microcapsules of the anionic copolymer L30D, in which the loading of PZQ was larger than 90% in solutions that were stable at low pH but released PZQ under enteric conditions. We also show that the encapsulation was effective in terms of masking PZQ taste through the analysis with an electronic tongue.

Immunosensors made with nanostructured films are promising for detecting cancer biomarkers, even at early stages of the disease, but this requires control of film architecture to preserve the biological activity of immobilized antibodies. In this study, we used electrochemical impedance spectroscopy (EIS) to detect Prostate Specific Antigen (PSA) with immunosensors produced with layer-by-layer (LbL) films containing anti-PSA antibodies in two distinct film architectures. The antibodies were either adsorbed from solutions in which they were free, or from solutions where they were incorporated into liposomes of dipalmitoyl phosphatidyl glycerol (DPPG). Incorporation into DPPG liposomes was confirmed with surface plasmon resonance experiments, while the importance of electrostatic interactions on the electrical response was highlighted using the Finite Difference Time-Domain Method (FDTD). The sensitivity of both architectures was sufficient to detect the threshold value to diagnose prostate cancer (ca. 4 ng mL−1). In contrast to expectation, the sensor with the antibodies incorporated into DPPG liposomes had lower sensitivity, though the range of concentrations amenable to detection increased, according to the fitting of the EIS data using the Langmuir-Freundlich adsorption model. The performance of the two film architectures was compared qualitatively by plotting the data with a multidimensional projection technique, which constitutes a generic approach for optimizing immunosensors and other types of sensors.

In this paper, we describe a new microfluidic cell to perform naked-eye electrochemical detection (NEED) through the oxidation of Ag-based auxiliary electrodes (AEs) in the presence of a cathodic current on the working electrode (WE). The chips were fabricated in polydimethylsiloxane by a simple, cost-effective, and cleanroom-free prototyping that allows reuse of each AE up to 60 times. Stainless steel microwires coated with Ag film and in electric contact to each other acted as AEs, whereas single microwires coated with Au and Ag films operated as WE and quasi-reference electrode, respectively. All the electrodes were reversibly introduced into the devices. The high contrast among nonoxidized and oxidized (black Ag2O nanostructures of up to 400 nm) Ag ensures the naked-eye monitoring of the AE oxidation extent. The number of oxidized AEs was taken as the analytical signal for semi-quantitative assays of p-benzoquinone as proof-of-concept. In addition to the low cost, a key advantage within the point-of-use testing philosophy, further contributions from our work include: i) simultaneous semi-quantitative naked-eye tests for the same analyte from a single WE to speed up electroanalytical assays and ii) the use of the time needed to oxidize one AE as the signal, which led to quantitative assays with enhanced sensitivity for hydrogen peroxide. To attain a fully portable and user-friendly NEED method, the sensor was integrated into a handheld platform that consisted of a homemade potentiostat and gravity-assisted pumping, with which on-site tests can be performed by nontrained personnel anywhere. The portable potentiostat has the lowest cost (US$7.72) reported in the literature compared with setups to measure electric current.

Room-temperature (RT) gas sensing is desirable for battery-powered or self-powered instrumentation that can monitor emissions associated with pollution and industrial processes. This review (with 171 references) discusses recent advances in three types of porous nanostructures that have shown remarkable potential for RT gas sensing. The first group comprises hierarchical oxide nanostructures (mainly oxides of Sn, Ni, Zn, W, In, La, Fe, Co). The second group comprises graphene and its derivatives (graphene, graphene oxides, reduced graphene oxides, and their composites with metal oxides and noble metals). The third group comprises 2D transition metal dichalcogenides (mainly sulfides of Mo, W, Sn, Ni, also in combination with metal oxides). They all have been found to enable RT sensing of gases such as NOx, NH3, H2, SO2, CO, and of vapors such as of acetone, formaldehyde or methanol. Attractive features also include high selectivity and sensitivity, long-term stability and affordable costs. Strengths and limitations of these materials are highlighted, and prospects with respect to the development of new materials to overcome existing limitations are discussed.

The effects induced by antibiotics on the bacterial membrane may be correlated with their bactericidal activity, and such molecular-level interactions can be probed with Langmuir monolayers representing the cell membrane. In this study, we investigated the interaction between [Ru(mcbtz)2(PPh3)2] (RuBTZ, mcbtz = 2-mercaptobenzothiazoline) and [Ru(mctz)2(PPh3)2] (RuCTZ, mctz = 2-mercaptothiazoline) with Langmuir monolayers of a lipid extract of Escherichia coli, an extract of lipopolysaccharides (LPSs), and a zwitterionic phospholipid, dioleoylphosphatidyl choline (DOPC). RuBTZ and RuCTZ had little effects on DOPC, which is consistent with their negligible toxicity toward mammalian cells that may be approximated by a zwitterionic monolayer. Also little were their effects on LPSs. In contrast, RuBTZ and RuCTZ induced expansion in the surface pressure isotherms and decreased the compressional modulus of the E. coli lipid extract. While the more hydrophobic RuBTZ seemed to affect the hydrophobic tails of the E...

We report the fabrication of immunosensors based on nanostructured mats of electrospun nanofibers of polyamide 6 and poly(allylamine hydrochloride) coated either with multiwalled carbon nanotubes (MWCNTs) or gold nanoparticles (AuNPs), whose three-dimensional structure was suitable for the immobilization of anti-CA19-9 antibodies to detect the pancreatic cancer biomarker CA19-9. Using impedance spectroscopy, the sensing platform was able to detect CA19-9 with a detection limit of 1.84 and 1.57 U mL-1 for the nanostructured architectures containing MWCNTs and AuNPs, respectively. The high sensitivity achieved can be attributed to the irreversible adsorption between antibodies and antigens, as confirmed with polarization-modulated infrared reflection absorption spectroscopy. The adsorption mechanism was typical Langmuir-Freundlich processes. The high sensitivity and selectivity of the immunosensors were also explored in tests with blood serum from patients with distinct concentrations of CA19-9, for which the impedance spectra data were processed with a multidimensional projection technique. The robustness of the immunosensors in dealing with patient samples without suffering interference from analytes present in biological fluids is promising for a simple, effective diagnosis of pancreatic cancer at early stages., This work was supported by FAPESP (Grant 2013/14262-7), CNPq, and CAPES (Brazil). D.S.C. also thanks FAPESP (Grant 2014/16789-5), Embrapa−Rede Agronano, and MCTI SisNano for financial support., info:eu-repo/semantics/publishedVersion

We demonstrate that the defect mode in the bulk plasmon-polariton gap of one-dimensional defective metamaterial photonic crystals can be used to achieve a giant enhancement of more than four orders of magnitude in the second harmonic (SH) conversion efficiency only by changing the incidence angle. Furthermore, the one-dimensional photonic crystal may be designed in order for the SH wave to coincide with the edge of the Bragg gap or with the defect mode inside this gap, in which case the enhancement is even higher. Because of the robustness of the bulk plasmon-polariton gap to scaling effects, the present proposal may inspire different routes for frequency upconversion, signal filtering, and switching photonic devices.

We demonstrate a concept for the giant enhancement of the transverse magneto-optical Kerr effect (TMOKE), with amplitudes reaching the maximum theoretical values of $\ifmmode\pm\else\textpm\fi{}1$. The concept exploits the strong electromagnetic field localization in $\ensuremath{\varepsilon}$-near-zero metamaterials to excite surface plasmon resonances with no need of a prism or grating coupler, thus opening routes for magneto-optical devices amenable to miniaturization. A demonstration of the capability of the enhancement mechanism is presented in which giant TMOKE values can be used for sensing and biosensing.

Well-established automatic analyses of texts mainly consider frequencies of linguistic units, e.g. letters, words, and bigrams. In a recent, alternative approach, medium and large-scale text structures were used in opposition to the belief that text structure is dominated by the language features. In this paper, we introduce a generalized similarity measure to compare texts which accounts for both the network structure of texts and the role of individual words in the networks. The similarity measure is used for authorship attribution of three collections of books, each composed of 8 authors and 10 books per author. High accuracy rates were obtained with typical values between 90 % and 98 . 75 % , much higher than with the traditional term frequency-inverse document frequency (tf-idf) approach for the same collections. These accuracies are also higher than those obtained solely with the topology of networks. We conclude that the different properties of specific words on the macroscopic scale structure of a whole text are as relevant as their frequency of appearance; conversely, considering the identity of nodes brings further knowledge about a piece of text represented as a network.

Herein we present a novel sensor for the detection of monosaccharides (e.g. glucose, fructose) in solution, using electrical impedance spectroscopy. The sensor is based on carbon interdigitated electrodes, printed on paper using screen printing. The surface of the electrodes was modified with a thin layer of hydrogel containing acrylamide copolymerised with 20 mol% 3-(Acrylamido)phenylboronic acid (PBA). It was observed that the hydrogel layers containing 20 mol% PBA swell considerably in the presence of glucose and fructose. This in turn changes the measured impedance across the electrodes, making it a suitable sensor for the quantitative detection of saccharides. We investigated the impedance and capacitance variations with different concentrations of glucose and fructose (0–5 mM) in aqueous phosphate buffer solutions. Variations in impedance were attributed to changes in the dielectric properties of the hydrogel under an applied electric field, due to swelling of the hydrogel layer induced by uptake and binding of sugar molecules to the boronate species within the gel. Impedance measurements at 1 kHz demonstrated that hydrogel swelling leads to an increased mobility of ions within the swollen hydrogel layer. The impedance decreased with increasing sugar concentration and the relative capacitance curves are markedly different for fructose and glucose, as the hydrogel exhibits greater swelling in the presence of fructose than glucose over the same concentration range. As the proposed sensor was shown to be suitable for the detection of glucose at concentration levels found in human sweat, future work will focus on the incorporation of these modified paper-based electrodes into wearable skin patches for non-invasive sugar monitoring in sweat.

Surface plasmon resonance (SPR) biosensing is based on the detection of small changes in the refractive index on a gold surface modified with molecular recognition materials, thus being mostly limited to detecting large molecules. In this paper, we report on a SPR biosensing platform suitable to detect small molecules by making use of the mediator-type enzyme microperoxidase-11 (MP11) in layer-by-layer films. By depositing a top layer of glucose oxidase or uricase, we were able to detect glucose or uric acid with limits of detection of 3.4 and 0.27 μmol l-1, respectively. Measurable SPR signals could be achieved because of the changes in polarizability of MP11, as it is oxidized upon interaction with the analyte. Confirmation of this hypothesis was obtained with finite difference time domain simulations, which also allowed us to discard the possible effects from film roughness changes observed in atomic force microscopy images. The main advantage of this mediator-type enzyme approach is in the simplicity of the experimental method that does not require an external potential, unlike similar approaches for SPR biosensing of small molecules. The detection limits reported here were achieved without optimizing the film architecture, and therefore the performance can in principle be further enhanced, while the proposed SPR platform may be extended to any system where hydrogen peroxide is generated in enzymatic reactions.

Sphingomyelins (SM) and phosphatidylcholines (PC) are major lipid classes in the external plasma membrane leaflet of mammalian cells. A preferential interaction between SM and cholesterol (Cho) in both cell and model membranes has been proposed as central for the formation of Cho- and SM-rich domains in membranes. In this context, the relevance of the SM hydrophobic moiety on its interaction with Cho for domain stabilization has been investigated by our group (1-2). We report here on the effects of sphingomyelin structure on the orientational and conformational properties of monolayers of pure lipids and of two ternary lipid mixtures (DOPC/16:0SM/Cho and DOPC/24:1SM/Cho), which are relevant as mammalian cell membrane models. We investigated interchain interactions, hydrogen bonding, conformational and structural properties using in situ polarization modulated infrared reflection absorption spectroscopy (PM-IRRAS). Our results indicate that the particular properties conferred on sphingolipids by unsaturation have profound implications on membrane organization.Finally, we also explored the orientational and conformational changes in lipid monolayers of DOPC/16:0SM/Cho 2:1:1 after the adsorption/insertion of the active toxin HlyA and its unacylated nonhemolytic precursor ProHlyA, so as to complement our knowledge on the action mechanism of both proteins., Instituto de Investigaciones Bioquímicas de La Plata, Comisión de Investigaciones Científicas de la provincia de Buenos Aires, Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas, Centro de Investigación de Proteínas Vegetales

A stochastic simulation of adsorption processes was developed to simulate the coverage of an atomic force microscope (AFM) tip with enzymes represented as rigid polyhedrons. From geometric considerations of the enzyme structure and AFM tip, we could estimate the average number of active sites available to interact with substrate molecules in the bulk. The procedure was exploited to determine the interaction force between acetyl-CoA carboxylase enzyme (ACC enzyme) and its substrate diclofop, for which steered molecular dynamics (SMD) was used. The theoretical force of (1.6 ± 0.5) nN per enzyme led to a total force in remarkable agreement with the experimentally measured force with AFM, thus demonstrating the usefulness of the procedure proposed here to assist in the interpretation of nanobiosensors experiments.

One of the major challenges in drug design is to identify compounds with potential toxicity toward target cells, preferably with molecular-level understanding of their mode of action. In this study, the antitumor property of a ruthenium complex, mer-[RuCl3(dppb)(VPy)] (dppb = 1,4-bis(diphenylphosphine)butane and VPy = 4-vinylpyridine) (RuVPy), was analyzed. Results showed that this compound led to a mortality rate of 50% of HEp-2 cell with 120 ± 10 μmol L(-1), indicating its high toxicity. Then, to prove if its mode of action is associated with its interaction with cell membranes, Langmuir monolayers were used as a membrane model. RuVPy had a strong effect on the surface pressure isotherms, especially on the elastic properties of both the zwitterionic dipalmitoylphosphatidylcholine (DPPC) and the negatively charged dipalmitoylphosphatidylglycerol (DPPG) phospholipids. These data were confirmed by polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS). In addition, interactions between the positive group from RuVPy and the phosphate group from the phospholipids were corroborated by density functional theory (DFT) calculations, allowing the determination of the Ru complex orientation at the air-water interface. Although possible contributions from receptors or other cell components cannot be discarded, the results reported here represent evidence for significant effects on the cell membranes which are probably associated with the high toxicity of RuVPy.

Investigation into nanostructured organic films has served many purposes, including the design of functionalized surfaces that may be applied in biomedical devices and tissue engineering and for studying physiological processes depending on the interaction with cell membranes. Of particular relevance are Langmuir monolayers, Langmuir-Blodgett (LB) and layer-by-layer (LbL) films used to simulate biological interfaces. In this review, we shall focus on the use of vibrational spectroscopy methods to probe molecular-level interactions at biomimetic interfaces, with special emphasis on three surface-specific techniques, namely sum frequency generation (SFG), polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) and surface-enhanced Raman scattering (SERS). The two types of systems selected for exemplifying the potential of the methods are the cell membrane models and the functionalized surfaces with biomolecules. Examples will be given on how SFG and PM-IRRAS can be combined to determine the effects from biomolecules on cell membrane models, which include determination of the orientation and preservation of secondary structure. Crucial information for the action of biomolecules on model membranes has also been obtained with PM-IRRAS, as is the case of chitosan removing proteins from the membrane. SERS will be shown as promising for enabling detection limits down to the single-molecule level. The strengths and limitations of these methods will also be discussed, in addition to the prospects for the near future.