Gold nanoparticle-attached ITO as a biocompatible matrix for myoglobin immobilization: direct electrochemistry and catalysis to hydrogen peroxide

Disposable biosensors based on metal nanoparticles

The coronavirus disease2019 (COVID-19) pandemic has highlighted the need for disposable biosensors that can detect viruses in infected patients quickly due to fast response and also at a low cost.The present review provides an overview of the applications of disposable biosensors based on metal nanoparticles in enzymatic and non-enzymatic sensors with special reference to glucose and H₂O₂, immunosensors as well as genosensors (DNA biosensors in which the recognized event consists of the hybridization reaction)for point-of-care diagnostics. The disposable biosensors for COVID19 have also been discussed.

Optical Detection of Denatured Ferritin Protein via Plasmonic Gold Nanoparticles Exposure through Aminosilane Solution

The presence of denatured proteins within a therapeutic drug product can create a series of serious adverse effects, such as mild irritation, immunogenicity, anaphylaxis, or instant death to a patient. The detection of protein degradation is complicated and expensive due to current methods associated with expensive instrumentation, reagents, and processing time. We have demonstrated here a platform for visual biosensing of denatured proteins that is fast, low cost, sensitive, and user friendly by exploiting the plasmonic properties of noble metal nanoparticles. In this study we have exposed artificially heat stressed ferritin and gold nanoparticles to 3-aminopropyl triethoxysilane, which degrades the protein by showing a systematic blue shift in the absorbance spectra of the gold nanoparticle/ferritin and aminosilane solution. This blue shift in absorbance produces a detectable visual color transition from a blue color to a purple hue. By studying the Raman spectroscopy of the gold nanoparticle/ferritin and aminosilane solution, the extent of ferritin degradation was quantified. The degradation of ferritin was again confirmed using dynamic light scattering and was attributed to the aggregation of the ferritin due to accelerated heat stress. We have successfully demonstrated a proof of concept for visually detecting ferritin from horse spleen that has experienced various levels of degradation, including due to heat stress.

Improved localized surface plasmon resonance index sensitivity based on chemically-synthesized gold nanoparticles on indium tin oxide surfaces

The results of this reported work indicated that gold nanoparticle arrays self-assembled on indium tin oxide (ITO) glasses can obtain broader localized surface plasmon resonance (LSPR) wavelength range and higher sensitivity than the bare quartz. The results of surface electric field calculated using finite difference time domain showed that the electric field of nanoparticles on ITO glasses is enhanced and the repulsive forces within each particle is weakened. According to the dipolar interaction mechanism, a weakened repulsive forces within each particle lead to a lower resonance frequency and a strong redshift of the LSPR spectra.

Cysteamine-palladium complex ([Pd(μ-OAc)(ppy)]2, ppy:2-phenylpyridine, PhMe)-modified peroxidase biosensor immobilized on a gold electrode

A new peroxidase biosensor was developed using cysteamine-palladium complex-modified gold electrode. The principle of the measurements is based on monitoring increase in the oxidation potential of palladium complex (at + 0.47 V vs Ag/AgCl) using amperometric detection. In the optimization studies of the biosensor, effects of enzyme amount, palladium complex amount, and duration of SAM formation on biosensor responses were investigated to optimize the bioactive layer. The biosensor has a fast response time of less than 10 s to hydrogen peroxide (H2O2), with a linear range of 5.0 × 10(- 6) to 150 × 10(- 6) M and a detection limit of 3.38 × 10(- 6) M.

Long Distance Electron Transfer Across >100 nm Thick Au Nanoparticle/Polyion Films to a Surface Redox Protein

Glutathione-decorated 5 nm gold nanoparticles (AuNPs) and oppositely charged poly(allylamine hydrochloride) (PAH) were assembled into {PAH/AuNP} n films fabricated layer-by-layer (LbL) on pyrolytic graphite (PG) electrodes. These AuNP/polyion films utilized the AuNPs as electron hopping relays to achieve direct electron transfer between underlying electrodes and redox proteins on the outer film surface across unprecedented distances >100 nm for the first time. As film thickness increased, voltammetric peak currents for surface myoglobin (Mb) on these films decreased but the electron transfer rate was relatively constant, consistent with a AuNP-mediated electron hopping mechanism.

Electrochemical behavior of Azure A/gold nanoclusters modified electrode and its application as non-enzymatic hydrogen peroxide sensor

A novel non-enzymatic hydrogen peroxide sensor was developed using Azure A/gold nanoclusters modified graphite electrode. The method of preparation of Azure A/gold nanoclusters was simple and it was characterized by UV-visible spectroscopy, field emission scanning electron microscopy (FESEM) and confocal Raman microscopy. The electrochemical properties of Azure A/gold nanoclusters modified graphite electrode was characterized by cyclic voltammetry. In 0.1M H(2)SO(4) the modified electrode showed redox peaks which correspond to the redox behavior of gold nanoparticle. In 0.1M PBS the modified electrode exhibited well defined redox peaks with the formal potential of -0.253 V which is analogous to the redox reaction of Azure A. The results have shown that the gold nanoclusters has reduced the formal potential of Azure A and enhanced the current due to the fast charge transfer kinetics. Also the modified electrode showed an enhanced electrocatalytic activity towards the reduction of H(2)O(2) in the concentration range of 3.26×10(-6)M to 3.2×10(-3)M with a detection limit of 1.08×10(-6)M (S/N=3). The proposed electrode exhibited good stability and reproducibility, and it has the potential application as a sensor for other biologically significant compounds.

Layer-by-layer assembled multilayers using catalase-encapsulated gold nanoparticles

We introduce a novel and versatile approach for the preparation of multilayers, based on catalase-encapsulated gold nanoparticles (CAT-Au(NP)), allowing electrostatic charge reversal and structural transformation through pH adjustment. CAT-Au(NP), which are synthesized directly from CAT stabilizer, can be electrostatically assembled with anionic and cationic PEs as a result of the charge reversal of the catalase stabilizers through pH control. In particular, at pH 5.2, near the pI of catalase, dispersed CAT-Au(NP) are structurally transformed into colloidal or network CAT-Au(NP) nanocomposites. Furthermore, we demonstrate that the layer-by-layer assembled multilayers composed of PEs and CAT-Au(NP) induce an effective electron transfer between CAT and the electrode as well as a high loading of CAT and Au(NP), and resultantly exhibit a highly catalytic activity toward H(2)O(2).

Gold nanoparticle-modified ultramicroelectrode arrays for biosensing: a comparative assessment

Gold ultramicroelectrode arrays (UMEAs) modified with gold nanoparticles (GNP) are shown to be a highly suitable transducer platform for the fabrication of biosensors. Comparative studies were carried out with microelectrodes and UMEAs, the latter being either bare or modified with GNPs. GNPs could be electrodeposited on to the UMEA surface, thereby increasing its active area up to one hundred times but without affecting its inherent electrodic properties. Horseradish peroxidase enzyme (HRP) was covalently immobilized over the three different transducer platforms by means of a thiol self-assembled monolayer (SAM). The resulting biosensors were applied to the amperometric detection of catechol, selected as a target analyte, at a set potential of -0.1 V vs. Ag/AgCl. The use of GNP-modified UMEAs increased the sensitivity of the developed biosensor 3-fold and 80-fold compared with the values achieved with bare UMEA and microelectrode based biosensors, respectively. The GNP-modified UMEA based biosensor showed a linear response to catechol in the concentration range from 0.1 mM to 0.4 mM, with a limit of detection of 0.05 mM.

Surface observation for seed-mediated growth attachment of gold nanoparticles on a glassy carbon substrate

A seed-mediated growth method for surface modification was applied to the attachment of gold nanoparticles (AuNPs) to glassy carbon (GC) surfaces. By simply immersing a GC plate at first into a seed solution containing 4 nm Au nano-seed particles and then into a growth solution containing HAuCl(4), ascorbic acid and cetyltrimethyammonium bromide, AuNPs could be successfully attached to the GC surface via the growth of nanoparticles. A possible control of the size and density of AuNPs on GC was examined by observing surface images with a field-emission scanning electron microscope (FE-SEM) after several preparations with different immersion times. Compared with previous results on the growth of AuNPs on indium tin oxide (ITO) surfaces, it was characteristic that the AuNPs attached to GC surfaces exhibited smaller size and higher density as well as a flatter and non-crystal-like morphology. In addition, for performing the dense attachment of regular nano-sized AuNPs on GC surfaces, immersion for 2 h into the growth solution was sufficient. Longer immersion for 24 h caused an irregular growth of bold Au micro-crystals, while 24 h was necessary in the case of AuNPs on ITO surfaces. Shorter seeding and growth times were found to be effective for a sparse attachment of smaller Au nanoparticles whose size was ca. 20 nm. It was clarified that the seed-mediated growth method for surface modification was valid for fabricating a nanointerface composed of AuNPs on GC surfaces.