Silica nanoparticles as a carrier for signal amplification

Abstract

Owing to the small size, high surface-to-volume ratio, and good biocompatibility, silica nanoparticles (SiNPs) have become the normally used carrier for bio-molecule immobilization. Label-based detection techniques have been used extensively for a wide range of applications in biological analysis. Organic dye, enzyme, electroactive species, and quantum dots (QDs) with unique optical and electrochemical performances have been used as probes for chemical and biological analysis. The common problem is that only a limited amount of probes can be linked to a biomolecule, which limited the extensive use of these probes in trace amounts of analyte detection. New technologies can provide efficient means to carry them with SiNPs, which possess a three-dimensional network suitable for load or encapsulating a large amount of probes. As a result, composite SiNPs can improve the detection sensitivity significantly because they carry a large amount of probes, which is beneficial for trace analysis. Also, SiNPs are nontoxic, highly water soluble, suitable for many biomolecules to conjugate, and increase the chemical and physical stability of the probes, which is very important for biological analysis. The goal of this review is to describe recent progress in the methods that SiNPs are used as a carrier of dyes, QDs, and enzyme and their application in biological analysis. Among these, SiNPs as a biolabel reagent for signal amplification in immunoassay, DNA, protein, and small molecule detection are the main topic in this review. We focus on two types of methods of carrying signal probes with SiNPs. One is to modify probes on the outer surface of the SiNPs and another is to encapsulate signal probes into the SiNPs. Particular attention is paid to update reported advances since 2009.