Enzyme-Functionalized Silica Nanoparticles as Sensitive Labels in Biosensing

Abstract

A novel strategy for sensitive detection of biomarkers using horseradish peroxidase (HRP)-functionalized silica nanoparticles as the label is presented. The enzyme-functionalized silica nanoparticles were fabricated by coimmobilization of HRP and alpha-fetoprotein antibody (anti-AFP, the secondary antibody, Ab2), a model protein, onto the surface of SiO(2) nanoparticles using gamma-glycidoxypropyltrimethoxysilane (GPMS) as the linkage. Through "sandwiched" immunoreaction, the enzyme-functionalized silica nanoparticle labels were brought close to the surface of gold substrates, as confirmed by the scanning electron microscopy (SEM) images. Enhanced detection sensitivity was achieved where the large surface area of SiO(2) nanoparticle carriers increased the amount of HRP bound per sandwiched immunoreaction. The electrochemical and chemiluminescence measurement showed 29.5- and 61-fold increases in detection signals, respectively, in comparison with the traditional sandwich immunoassay. The improved particle synthesis using a "seed-particle growth" route yielded particles of narrow size distribution, which allowed consistent loading of HRP and anti-AFP on each microsphere and ensured subsequent immunosensing possessed high sensitivity and reproducibility. This strategy was successfully demonstrated as a simple, cost-effective, specific, and potent method to detect AFP in practical samples.

Review: Bioanalytical applications of biomolecule-functionalized nanometer-sized doped silica particles

“…The advantages of covalent conjugation were also demonstrated when anti-CEA antibodies were immobilized onto the surface of core/shell Fe 3 O 4 -SiO 2 nanoparticles using -glycidoxypropyltrimethoxysilane (GPMS) [221], when glucose oxidase was immobilised on multilayer silica nanoparticles (using a layer-by-layer (LbL) covalent technique) [222], and when IgG antigen was bonded to the surface of quartz crystal silica nanoparticles using CNBr [223]. Very recently, a novel strategy for sensitive biomarker detection using horseradish peroxidase (HRP)-functionalized silica nanoparticles was presented [224]. The enzyme-functionalized particles were fabricated by co-immobilization of HRP and anti-human ␣-fetoprotein (AFP) antibodies onto particles surfaces.…”

Fe3O4/Au magnetic nanoparticle amplification strategies for ultrasensitive electrochemical immunoassay of alfa-fetoprotein

“…[16][17][18] In order to meet the increasing demand for early and ultrasensitive detection of tumor markers, three primary signal amplification strategies using nanomaterials have been developed. 19 The f irst method involves the use of metal and semiconductor nanoparticles directly as electroactive labels to amplify the electrochemical detection of proteins. 20,21 The second method uses nanoparticles as carriers for loading a large amount of electroactive species to amplify the detection signal.…”

Organic Modification of Hydroxylated Nanoparticles: Silica, Sepiolite, and Polysaccharides

“…These amino surface groups can be used directly as anchoring points or as intermediate for functional group interconversion [58]. Mercapto [59][60][61][62] and epoxysilanes [63,64] are also common coupling agents. Carboxylic acid, directly introduced with coupling agents bearing this functionality [65] or by chemical reactions on previously grafted amine groups [58], is also frequently used.…”