Electropolymerized Melamine on Electrochemically Reduced Graphene Oxide: Growth Mechanistics, Electrode Processing, and Amperometric Sensing of Acyclovir.

Metal-free, cost-efficient, redox-active electrode materials, combining graphene derivatives with nitrogen-rich polymelamine (PM), are widely explored as an interface layer for electrocatalysis and an electrochemical sensor platform. However, conventional chemical routes often yield derivatives of PM suffering from impaired redox behavior, restricting their electron-transfer kinetics. Herein, an optimal potentiodynamic method has been established to electrodeposit PM on electrochemically reduced graphene oxide (ErGO). A supporting electrolyte, containing Cl-, enhances the formation of intermediates NH3+ and ═NH2+ at the monomeric melamine, eventually interacting with the residual oxygenated functional groups of ErGO to form PM. In situ Raman spectrum analysis revealed the influence of the defective area and the graphitization ratio on the ErGO surface during the course of electropolymerization of melamine. Under optimal electrodeposition conditions (E = 0-1.6 V; ν = 0.1 V/s), the amount of electrodeposited PM on the ErGO surface was determined to be 16.5 µg/(cycle·cm2), using electrochemical quartz crystal microbalance analysis. An ErGO-PM-modified glassy carbon electrode (GCE) and a screen-printed electrode exhibit the direct electrooxidation of acyclovir (ACV). Amperometric analyses of ErGO-PM-modified electrodes exhibited the lowest detection limit of 137.4 pM with analytical robustness, rapid steady state, and reproducibility promising for ACV detection in complex biological matrices.

Peptide-based direct electrochemical detection of receptor binding domains of SARS-CoV-2 spike protein in pristine samples.

RNA isolation and amplification-free user-friendly detection of SARS-CoV-2 is the need of hour especially at resource limited settings. Herein, we devised the peptides of human angiotensin converting enzyme-2 (hACE-2) as bioreceptor at electrode interface for selective targeting of receptor binding domains (RBD) of SARS-CoV-2 spike protein (SP). Disposable carbon-screen printed electrode modified with methylene blue (MB) electroadsorbed graphene oxide (GO) has been constructed as cost-efficient and scalable platform for hACE-2 peptide-based SARS-CoV-2 detection. In silico molecular docking of customized 25 mer peptides with RBD of SARS-CoV-2 SP were validated by AutoDock CrankPep. N-terminal region of ACE-2 showed higher binding affinity of - 20.6 kcal/mol with 15 H-bond, 9 of which were < 3 Å. Electrochemical biosensing of different concentrations of SPs were determined by cyclic voltammetry (CV) and chronoamperometry (CA), enabling a limit of detection (LOD) of 0.58 pg/mL and 0.71 pg/mL, respectively. MB-GO devised hACE-2 peptide platform exert an enhanced current sensitivity of 0.0105 mA/pg mL-1 cm-2 (R2 = 0.9792) (CV) and 0.45 nA/pg mL-1 (R2 = 0.9570) (CA) against SP in the range of 1 pg/mL to 1 µg/mL. For clinical feasibility, nasopharyngeal and oropharyngeal swab specimens in viral transport medium were directly tested with the prepared peptide biosensor and validated with RT-PCR, promising for point-of-need analysis.

Impact of aminated carbon quantum dots as a novel co-reactant for Ru(bpy)32+: resolving specific electrochemiluminescence for butein detection.

Development of novel nanomaterial-based co-reactant is highly desired for enhancing ECL intensity and widespread analytical applications. Herein, we report the distinct role of amine-functionalized carbon quantum dots (f-CQDs) as a co-reactant, for the first time, augmenting the ECL property of Ru(bpy)32+ and demonstrating for biopharmaceutical (butein) detection. Unlike conventional co-reactants like tripropylamine (TPrA), 2-(dibutylamino)ethanol (DBAE), and pristine CQDs, the f-CQDs as a co-reactant yield superior ECL of Ru(bpy)32+. More importantly, the ECL intensity is independent of types of noble metals, metal oxide surfaces, and dissolved oxygen. Notably, the ECL intensity of Ru(bpy)32+-f-CQDs is linearly quenched with an increased concentration of butein, whereas no changes were observed with conventional co-reactants. ECL functionality of Ru(bpy)32+-f-CQDs has no interference with other similar phytochemicals and antioxidants. Enhanced selectivity is observed due to the formation of polyaminoquinone-like structures, which is confirmed by in situ spectroelectrochemical (UV-vis) and FT-IR studies. The present result envisaged that f-CQDs could be an alternative co-reactant for TPrA/DBAE, raising the ECL of Ru(bpy)32+ suitable for analytical studies. Graphical abstract.

Amperometric determination of As(III) and Cd(II) using a platinum electrode modified with acetylcholinesterase, ruthenium(II)-tris(bipyridine) and graphene oxide.

The authors describe an amperometric biosensor for the determination As(III) and Cd(II) based on the inhibition of the enzyme acetylcholineesterase (AChE). A platinum electrode was modified with ruthenium(II)-tris(bipyridyl), graphene oxide and AChE and then showed redox peaks at 0.06 and 0.2 V vs Ag/AgCl in the presence of acetylthiocholine chloride (ATChCl). Amperometry unveiled a steady-state turnover rate with the release of thiocholine. In the presence of arsenic(III) and cadmium(II), AChE showed an inhibitive response at 0.214 and 0.233 V vs Ag/AgCl, respectively. The electrode exhibits a detection limit and linear range of 0.03 µM and 0.05-0.8 µM for As(III) and 0.07 µM and 0.02-0.7 µM for Cd(II), respectively. Type of inhibition and inhibition constants induced by As(III) and Cd(II) on the catalytic sites of AChE were determined from Dixon and Lineweaver-Burk plots. The modified electrode was applied to the determination of As3+ and Cd2+ in river, tap and waste water, and the results proved that the method is sensitive and can be an alternative to chromatographic and spectroscopic techniques. Graphical abstract Schematic presentation of Pt/Ru(II)-tris(bipy)-GO/AChE electrode in absence and presence of metal ions (As3+/Cd2+).

Nanostructured molybdenum oxide-based antibacterial paint: effective growth inhibition of various pathogenic bacteria.

The prevention of bacterial infections in the health care environment is paramount to providing better treatment. Covering a susceptible environment with an antimicrobial coating is a successful way to avoid bacterial growth. Research on the preparation of durable antimicrobial coatings is promising for both fundamental surface care and clinical care applications. Herein, we report a facile, efficient, and scalable preparation of MoO3 paint using a cost-effective ball-milling approach. The MoO3 nanoplates (synthesized by thermal decomposition of ammonium heptamolybdate) are used as a pigment and antibacterial activity moiety in alkyd resin binders and other suitable eco-friendly additives in the preparation of paint. Surface morphology, chemical states, bonding nature, and intermolecular interaction between the MoO3 and the alkyd resin were studied using Raman and x-ray photoelectron spectroscopic analysis. The antibacterial properties of a prepared MoO3 nanoplate against various bacterial strains (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Klebsiella pneumoniae) was determined using the microdilution method. Bacterial strains exposed to an MoO3 paint coated surface exhibit a significant loss of viability in a time-dependent manner. Fundamental modes of antibacterial activities ascribed from a biocompatible and durable MoO3 nanostructure incorporated into an alkyd resin complex are discussed. The obtained experimental findings suggest the potential utility of prepared MoO3-based paint coating for the prevention of health care associated infections.

ß-Cyclodextrin-Tethered Butein, a Greener Redox-Active Biomaterial for Electrochemical Enzymatic Sensing of Sialic Acid.

Biocompatible, industrially scalable, and opto/electrochemically active biomaterials are promising for biosensor platform design and application. Herein, cyclic oligosaccharide, ß-cyclodextrin (BCD), is conjugated with Butein, a chalcone-type polyphenol, via dehydration reaction of the hydroxyl groups of BCD and the benzoyl ring of Butein. Functional group changes in the conjugated BCD-Butein were comprehensively studied using UV-visible absorbance, Fourier transform-infrared, and X-ray photoelectron spectroscopic techniques. The electrochemical characteristics of BCD-Butein were explored using cyclic voltammetry, showing the reversible redox behavior (2e-/2H+) attributed to the catecholic OH group of Butein. The BCD-Butein-modified electrode exhibits a surface-confined redox process (R2 = 0.99, Ipa and Ipc) at the interface, suitable for external mediatorless sensor studies. An enzymatic biomolecular sensor has been constructed using BCD-Butein-modified glassy carbon and a screen-printed electrode targeting sialic acid as the model clinical biomarker. With the enzyme sialic acid aldolase, BCD-Butein-modified substrate exhibited a selective conversion of sialic acid to N-acetyl-d-mannosamine and pyruvate, with a wide linear detection range (1-100 nM), the lowest detection limit of 0.2 nM, and a quantification limit of 0.69 nM, convenient for clinical threshold diagnosis.

Surface activation of graphene oxide nanosheets by ultraviolet irradiation for highly efficient anti-bacterials.

A comprehensive investigation of anti-bacterial properties of graphene oxide (GO) and ultraviolet (UV) irradiated GO nanosheets was carried out. Microscopic characterization revealed that the GO nanosheet-like structures had wavy features and wrinkles or thin grooves. Fundamental surface chemical states of GO nanosheets (before and after UV irradiation) were investigated using x-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. Minimum inhibitory concentration (MIC) results revealed that UV irradiated GO nanosheets have more pronounced anti-bacterial behavior than GO nanosheets and standard antibiotic, kanamycin. The MIC of UV irradiated GO nanosheets was 0.125 µg ml⁻¹ for Escherichia coli and Salmonella typhimurium, 0.25 µg ml⁻¹ for Bacillus subtilis and 0.5 µg ml⁻¹ for Enterococcus faecalis, ensuring its potential as an anti-infective agent for controlling the growth of pathogenic bacteria. The minimum bactericidal concentration of normal GO nanosheets was determined to be two-fold higher than its corresponding MIC value, indicating promising bactericidal activity. The mechanism of anti-bacterial action was evaluated by measuring the enzymatic activity of ß-D-galactosidase for the hydrolysis of o-nitrophenol-ß-D-galactopyranoside.

Buteinylated-hafnium oxide bionanoparticles for electrochemical sensing of wogonin.

Hybridizing biomolecules with metal oxide nanostructures possessing inherent optical emission and electrochemical functionality is advantageous for external mediator-free analytical applications. This work demonstrates the ultrasonochemical synthesis of hafnium oxide (HfO2) nanoparticles and their combination with butein, a chalcone type polyphenol, for the direct electrochemical detection of active herbaceuticals. The underlying hybridization chemistry between HfO2 and butein within the bio-nano interface is comprehensively investigated using ultraviolet diffuse reflectance, X-ray diffraction, Fourier-transform infrared, and X-ray photoelectron spectroscopic techniques. Electron micrographs suggest the formation of elongated nano spherical particles of HfO2 with the incorporation of butein (average particle size of 17.6 ± 2.9 nm). The catecholic OH group of butein existing on the surface of hybridized HfO2 exhibits reversible redox behavior convenient for probing the selected target analyte at physiological pH. The electron diffusion kinetics, electron transfer coefficient and rate constant parameters of the prepared HfO2-butein electrode material have been studied in detail for further application in biomolecular sensing of wogonin. The as-developed sensor platform exhibits a linear detection range of 20-100 µM with a current density of 60 µA cm-2 and a detection limit of 0.63 µM, which is promising for herbaceutical analysis.

Emerging trends in point-of-care biosensing strategies for molecular architectures and antibodies of SARS-CoV-2.

COVID-19, a highly contagious viral infection caused by the occurrence of severe acute respiratory syndrome coronavirus (SARS-CoV-2), has turned out to be a viral pandemic then ravaged many countries worldwide. In the recent years, point-of-care (POC) biosensors combined with state-of-the-art bioreceptors, and transducing systems enabled the development of novel diagnostic tools for rapid and reliable detection of biomarkers associated with SARS-CoV-2. The present review thoroughly summarises and discusses various biosensing strategies developed for probing SARS-CoV-2 molecular architectures (viral genome, S Protein, M protein, E protein, N protein and non-structural proteins) and antibodies as a potential diagnostic tool for COVID-19. This review discusses the various structural components of SARS-CoV-2, their binding regions and the bioreceptors used for recognizing the structural components. The various types of clinical specimens investigated for rapid and POC detection of SARS-CoV-2 is also highlighted. The importance of nanotechnology and artificial intelligence (AI) approaches in improving the biosensor performance for real-time and reagent-free monitoring the biomarkers of SARS-CoV-2 is also summarized. This review also encompasses existing practical challenges and prospects for developing new POC biosensors for clinical monitoring of COVID-19.

Label-free genosensing of dengue serotypes with an electrodeposited reduced graphene oxide-tris(bipyridine)ruthenium(II).

Constructing a label-free electrochemical transducer platform without compromising inherent biocompatibility against specific bioreceptor remains challenging, particularly probing nucleic acid hybridization at electrode interface without external redox-mediator. Here, we show that electrochemically reduced graphene oxide-tris(bipyridine)ruthenium(II) (ErGO-TBR) nanosheets electrodeposited on carbon screen printed electrode can quantify hybridization of clinically important target sequences specific to serotypes of dengue virus (DENV) non-structural 1 (NS1) protein. Different variables including deposition potential, time, and electrolytic composition were optimized for fabrication of label-free transducer platform. Structural and electrochemical properties of ErGO-TBR/SPE were comprehensively elucidated using microscopic and spectroscopic techniques. Electrochemical quartz crystal microbalance (EQCM) analysis reveals the growth of electrodeposited redox-active species on the electrode interface. Surface functional group investigations suggested that TBR deposited on the basal and edges of ErGO substrate via electrostatic and π-π interactions. Functionalization of bio-affinity layer (B) on ErGO-TBR/SPE enables better loading of probe DNA (PDNA) toward specific detection of DENV target DNA (TDNA) with an ultralow detection limit promising for clinical diagnosis. Scalable chronoamperometry-based redox-active surface growth, customizable bioactivation strategy and external mediator-less probing of nucleic acid hybridization make the present system suitable for other translational application in healthcare diagnosis.

DNA-functionalized carbon quantum dots for electrochemical detection of pyocyanin: A quorum sensing molecule in Pseudomonas aeruginosa.

The electrochemical biosensing strategy for pyocyanin (PYO), a virulent quorum-sensing molecule responsible for Pseudomonas aeruginosa infections, was developed by mimicking its extracellular DNA interaction. Calf thymus DNA (ct-DNA) functionalized amine-containing carbon quantum dots (CQDs) were used as a biomimetic receptor for electrochemical sensing of PYO as low as 37 nM in real urine sample. The ct-DNA-based biosensor enabled the selective measurement of PYO in the presence of other interfering species. Calibration and validation of the PYO sensor platform were demonstrated in buffer solution (0-100 µM), microbial culture media (0-100 µM), artificial urine (0-400 µM), and real urine sample (0-250 µM). The sensor capability was successfully implemented for point-of-care (POC) detection of PYO release from Pseudomonas aeruginosa strains during lag and stationary phases. Cross-reactivity of the sensing platform was also tested in other bacterial species such as Bacillus subtilis, Escherichia coli, Klebsiella pneumoniae, Shigella dysenteriae, Staphylococcus aureus, and Streptococcus pneumoniae. Potential clinical implementation of the ct-DNA-based sensor was manifested in detecting the PYO in P. aeruginosa cultured baby diaper and sanitary napkin. Our results highlight that the newly developed ct-DNA-based sensing platform can be used as a potential candidate for real-time POC diagnosis of Pseudomonas aeruginosa infection in clinical samples.

Biogenic synthesis of multidimensional gold nanoparticles assisted by Streptomyces hygroscopicus and its electrochemical and antibacterial properties.

The fabrication of reliable, green chemistry processes for nanomaterial synthesis is an important aspect of nanotechnology. The biosynthesis of single-pot room-temperature reduction of aqueous chloroaurate ions by Streptomyces hygroscopicus cells has been reported to facilitate the development of an industrially viable greener methodology for the synthesis of technologically important gold nanoparticles (AuNPs). Multidimensional AuNPs are generated via the manipulation of key growth parameters, including solution pH and reaction time. The synthesized nanostructures are characterized by UV/Vis and energy dispersive X-ray analysis studies. Particle morphology is characterized by HRTEM, FE-SEM and BioAFM. Additionally, we have demonstrated the electrochemical and antibacterial properties of AuNPs via cyclic voltammetry analysis and a minimal inhibitory concentration assay. Owing to the drawbacks of chemical synthesis, a biological synthesis method has been developed to generate biocompatible, inexpensive and eco-friendly size-controlled nanoparticles.

Functional nanoparticles translocation into cell and adhesion force curve analysis.

The aim of this research is to investigate the cell translocation of two functional nanoparticles (barium sulfate (BaSO4NPs), europium (III) doped gadolinium oxide nanoparticles (Gd2O3@EuNPs)) into A549 cells by Bio-Atomic Force Microscopy (Bio-AFM). Successful cell translocation of these two nanoparticles are ensured from the measurement of changes in the cell surface roughness and interaction (extension), retraction forces from the vertical deflection of tip towards substrate surfaces through force-distance curve slope analysis. Measurement of typical adhesion forces (i.e., extension and retraction) between the tip-substrate (0.0963 and 1.155 nN), tip-A549 cell substrate (0.1177 and 2.468 nN), tip-Gd2O3@EuNPs/A549 substrate (0.0785 and 0.4276 nN) and tip-BaSO4NPs/A549 substrate (0.518 and 6.838 nN) confirms the successful cell translocation of functional nanoparticles into A549 cells. Further the nanoscale resolution of topographical height and 3D images evinces the surface characteristics of normal A549 cells and nanoparticles translocated A549 cells.

NMR studies of artificial double-crossover DNA tiles.

This report documents the design and characterization of DNA molecular nanoarchitectures consisting of artificial double crossover DNA tiles with different geometry and chemistry. The Structural characterization of the unit tiles, including normal, biotinylated and hairpin loop structures, are morphologically studied by atomic force microscopy. The specific proton resonance of the individual tiles and their intra/inter nucleotide relationships are verified by proton nuclear magnetic resonance spectroscopy and 2-dimensional correlation spectral studies, respectively. Significant up-field and down-field shifts in the resonance signals of the individual residues at various temperatures are discussed. The results suggest that with artificially designed DNA tiles it is feasible to obtain structural information of the relative base sequences. These tiles were later fabricated into 2D DNA lattice structures for specific applications such as protein arrangement by biotinylated bulged loops or pattern generation using a hairpin structure.

Electrochemical and DFT studies of andrographolide on electrochemically reduced graphene oxide for anti-viral herbaceutical sensor.

Herbal extracts are re-emerging as potential remedies for various vector-borne diseases. Amongst several phytochemicals, active ingredients of Andrographis paniculata extract is regarded as promising for dengue fever, caused by Aedes species. However, fingerprinting the active phytochemicals from herbal extracts are often relies on sophisticated analytical techniques which are not universally accessible. Herein, an electrochemically reduced graphene oxide on glassy carbon electrode (ErGO/GCE) has been devised as user-friendly and cost-effective sensor platform for fingerprinting of andrographolide (AG) in anti-dengue polyherbal formulation, i.e., Nilavembu kudineer powder. Confocal laser Raman and X-ray photoelectron spectral analyses revealed that the ErGO surfaces exert structural defects augmenting the conductivity at the electrode interface. DFT investigations enabled that C-3 and C-18 OH groups in AG is involved in the electrooxidation and adsorption-diffusion at the ErGO interface, respectively. Complementary electrochemical studies revealed that the diffusion-controlled process follows 1e-/1H+ transfer. Under optimal experimental conditions, ErGO sensor platform exhibit an amplified current sensitivity of 13.3 µA µM-1. cm-2 in the studied analyte concentration range of 10-400 µM. From the polyherbal extract and clinical sample analysis, the proposed sensor system offers selective, and sensitive detection of target AG regardless of common interferents.

Rational design of effective solid-state electrochemiluminescence platform of Gold@Polyluminol nanocomposite as an ultrasensitive immuno-probe for selective detection of prostate specific antigen.

An electrodeposited gold@poly-luminol nanocomposite on glassy carbon electrode (Au@PL-NC/GCE) has been developed and demonstrated as solid-state electrochemiluminescence (ECL) immunosensor platform for prostate specific antigen (PSA) sensing. In-situ electro-generated reactive oxygen species (ROS) from oxygen reduction reaction in oxygen saturated PBS (pH 7.4) acts as sole co-reactant augmenting the signal transduction. Protein-G bio-affinity layer interfaced with Au@PL-NC/GCE (Protein-G/Au@PL-NC/GCE) to support the effective localization of Fc region of the monoclonal antibodies of PSA (mAb-PSA). As-developed ECL probe exhibit selective recognition of target analyte, PSA, enabling wide linearity of 1 fg mL-1 to 10 µg mL-1 with a calculated limit of detection (LOD) and limit of quantification (LOQ) of 0.45 fg mL-1 and 1.37 fg mL-1, respectively. The selectivity and specificity of the ECL probe was tested using human serum albumin, immunoglobulin G and mixtures of the same with target analyte. Fabricated ECL probe not only exhibit high sensitivity and specificity against commercial PSA samples but also enable clinical detection in real human serum and urine samples with acceptable recovery range from 97% to 103%. Our results suggest that the fabricated reagent-less solid-state ECL platform holds promising application in the field of prostate oncological screening and its point-of-care applications.

Bioadhesive Gauze Embedded with Chitosan-Butein Bioconjugate: A Redox-Active pH Sensor Platform.

With the ever-growing global wound care market, demand for robust redox-active healthcare material is obvious for the construction of wearable sensor platforms. Surface reactive functional group-rich material like chitosan holds huge potential for electrochemical biosensor application. Herein, a metal-free redox-active chitosan-butein (CSB) bioconjugate is processed into epidermal bioadhesive electrode material useful for pH sensors promising toward wound site analysis. A two-electrode system devised for conducting carbon-reinforced silver chloride paste and CSB-modified carbon/silver chloride matrix was used as a reference and working electrodes, respectively. Dimensions of working and reference electrodes (4 mm) were designed by 2D cutter plotter-assisted stenciling. The cross-sectional topology of the constructed adhesive CSB-sensor platform exhibits an average surface thickness of 183 ± 2 µm. Cyclic voltammetric analysis revealed the inherent 2e-/2H+ transfer attributed to the catechol OH groups of graft polymerized CSB modified on adhesive gauze. As-fabricated modified electrode substrates exhibit distinguishable potential differences with respect to electrolytes of varied pH (between 5 to 9), promising for wound site analysis.

A machine learning-based approach to determine infection status in recipients of BBV152 (Covaxin) whole-virion inactivated SARS-CoV-2 vaccine for serological surveys.

Data science has been an invaluable part of the COVID-19 pandemic response with multiple applications, ranging from tracking viral evolution to understanding the vaccine effectiveness. Asymptomatic breakthrough infections have been a major problem in assessing vaccine effectiveness in populations globally. Serological discrimination of vaccine response from infection has so far been limited to Spike protein vaccines since whole virion vaccines generate antibodies against all the viral proteins. Here, we show how a statistical and machine learning (ML) based approach can be used to discriminate between SARS-CoV-2 infection and immune response to an inactivated whole virion vaccine (BBV152, Covaxin). For this, we assessed serial data on antibodies against Spike and Nucleocapsid antigens, along with age, sex, number of doses taken, and days since last dose, for 1823 Covaxin recipients. An ensemble ML model, incorporating a consensus clustering approach alongside the support vector machine model, was built on 1063 samples where reliable qualifying data existed, and then applied to the entire dataset. Of 1448 self-reported negative subjects, our ensemble ML model classified 724 to be infected. For method validation, we determined the relative ability of a random subset of samples to neutralize Delta versus wild-type strain using a surrogate neutralization assay. We worked on the premise that antibodies generated by a whole virion vaccine would neutralize wild type more efficiently than delta strain. In 100 of 156 samples, where ML prediction differed from self-reported uninfected status, neutralization against Delta strain was more effective, indicating infection. We found 71.8% subjects predicted to be infected during the surge, which is concordant with the percentage of sequences classified as Delta (75.6%-80.2%) over the same period. Our approach will help in real-world vaccine effectiveness assessments where whole virion vaccines are commonly used.

Copper-glucosamine microcubes: synthesis, characterization, and C-reactive protein detection.

Cubelike microstructures of glucosamine-functionalized copper (GlcN-CuMC's) have been fabricated by the integration of injection pump and ultrasonochemistry. Although bulk microstructures and the nanostructure of metallic copper exhibit distinct applications, the amino sugar surface-functionalized copper is almost biocompatible and exhibits advanced features such as more crystallinity, high thermal stability, and electrochemical feasibility toward biomolecule (C-reactive protein, CRP) detection. An electrochemical test of this GlcN-CuMC's was demonstrated by immobilization on a conventional gold-PCB (Au-PCB) electrode. The combination of a biointerface membrane, from glucosamine functionalization, and electroactive sites of metallic copper provides a very efficient electrochemical response against various concentration of CRP. A perfect scaling of steady-state currents with r(2) values of 0.9862 (I(pa)) and 0.9972 (I(pc)) indicate the promise of this kind of biofunctionalized microstructure electrode for many surface and interface applications.

PEGylated polyethyleneimine grafted silica nanoparticles: enhanced cellular uptake and efficient siRNA delivery.

The present paper reports the utilization of hybrid nanocomposite particles consisting of PEI25k-PEG5k copolymer grafted silica nanoparticles (SiO(2)NPs) for enhanced cellular uptake and siRNA delivery. High-resolution transmission electron microscopy and dynamic light scattering measurements ensured the average particle size of the final hybrid component as 45 nm (core SiO(2), 28-30 nm and shell PEI25k-PEG5k, 12-15 nm). Surface morphology from atomic force microscopy analysis showed the significant relationship between the particle size and shape. (29)Si and (13)C cross-polarization-magic angle spinning solid state nuclear magnetic resonance (NMR), (1)H-NMR, and Fourier transform infrared spectroscopy were used to obtain the relevant structural information (such as Q3, silanol; Q4, siloxane functional groups of SiO(2)NPs; resonance shifts and bending vibrations of PEI25k, -CH(2)-CH(2)-NH-; and PEG5k, -CH(2)-CH(2)-O-) from copolymer nanoparticle. Stable complexation of siRNA and nanocomposite particle (wt.%:wt.%) was achieved from 1:5 to 1:15 ratio. Nanocomposite particle (N/P) ratio and siRNA concentration determine the stability and knockdown efficiency of the PEI25k-PEG5k-graft-SiO(2)NPs-siRNA complexes. It was shown that highly positively charged (zeta potential, +66 mV) PEI25k-PEG5k-graft-SiO(2)NPs result in strong affinity with negatively charged siRNA. Confocal microscopy showed intensified cellular uptake of siRNA into cytoplasm of A549 cancer cell utilized for in vitro study. In conclusion, the coherence, graft density of copolymer-SiO(2)NPs, and siRNA concentration were found to strongly influence the stability, and hence determine the knockdown efficiency, of PEI25k-PEG5k-graft-SiO(2)NPs-siRNA complexes.