Label-free amperometric immunosensor based on antibody immobilized on a positively charged gold nanoparticle/l-cysteine-modified gold electrode

Nanomaterials: Electrochemical Properties and Application in Sensors

The unique properties of nanoparticles make them an extremely valuable modifying material, being used in electrochemical sensors. The features of nanoparticles affect the kinetics and thermodynamics of electrode processes of both nanoparticles and redox reactions occurring on their surface. The paper describes theoretical background and experimental studies of these processes. During the transition from macro- to micro- and nanostructures, the analytical characteristics of sensors modify. These features of metal nanoparticles are related to their size and energy effects, which affects the analytical characteristics of developed sensors. Modification of the macroelectrode with nanoparticles and other nanomaterials reduces the detection limit and improves the degree of sensitivity and selectivity of measurements. The use of nanoparticles as transducers, catalytic constituents, parts of electrochemical sensors for antioxidant detection, adsorbents, analyte transporters, and labels in electrochemical immunosensors and signal-generating elements is described.

Highly stable positively charged dendron-encapsulated gold nanoparticles

We report the development of a novel cationic dendron (TAG1-PCD) and a positively charged gold nanoparticle-dendron conjugate (PCD-AuNP). TAG1-PCD was designed by considering the reactivity, hydrophilicity, and cationic nature that is required to yield a stable gold conjugate in aqueous media. The PCD-AuNPs, nominally 10 nm in size, were synthesized by reduction of chloroauric acid in the presence of TAG1-PCD. The physicochemical properties of PCD-AuNPs were characterized by dynamic light scattering, transmission electron microscopy, UV-vis absorbance, and X-ray photoelectron spectroscopy for investigation of size distribution, shape uniformity, surface plasmon resonance bands, and Au-dendron bonding. Asymmetric-flow field flow fractionation was employed to confirm the in situ size, purity, and surface properties of the PCD-AuNPs. Additionally, the stability of PCD-AuNPs was systematically evaluated with respect to shelf life determination, stability in biological media and a wide range of pH values, chemical resistance against cyanide, redispersibility from lyophilized state, and stability at temperatures relevant to biological systems. Dose dependent cell viability was evaluated in vitro using the human lung epithelial cell line A549 and a monkey kidney Vero cell line. Observations from in vitro studies are discussed. Overall, the investigation confirmed the successful development of stable PCD-AuNPs with excellent stability in biologically relevant test media containing proteins and electrolytes, and with a shelf life exceeding 6 months. The excellent aqueous stability and apparent lack of toxicity for this conjugate enhances its potential use as a test material for investigating interactions between positively charged NPs and biocellular and biomolecular systems, or as a vehicle for drug delivery.