Development of nanoparticles-based biosensing assay for identification of enzyme activities

Abstract

Nanoparticles provide a useful platform for wide range of applications in the fields of biochemistry and biomedicine. They have greatly attracted considerable attentions and have been widely used for biosensing, bioimaging and drug delivery systems. This research dissertation focuses on developing novel and convenient biosensing assays for detecting enzyme activities using metallic nanoparticles. Metallic nanoparticles exhibit unique optical and physical features. Taking advantage of their excellent optical properties, we developed a gold nanoparticles and silver nanoparticles-based colorimetric assay for rapidly sensing β-lactamase activities and screening β-lactamase inhibitors. This simple and applicable method is efficient for screening class A and class C β-lactamases inhibitors in vitro. Moreover, this approach is also practicable for screening β-lactamases inhibitors in living bacterial strains. The detailed studies were presented in chapter two, three, and four. This easily operated method possesses the potential of wide applications for drug development and medicinal diagnosis. Programming nanostructures of gold nanoparticles by enzyme activities were described in chapter five of this dissertation. Self-assembly and disassembly of gold nanoparticles were controlled by various enzyme activities. The designed peptide conjugate as enzyme substrate is responsive to esterase and protease. In the presence of esterase and substrate, gold nanoparticles were triggered to assembly by the peptide linker released from the hydrolyzed substrate. After further treatment with protease, the peptide linker was specifically cleaved, which results in the disassembly of gold nanoparticles. Therefore, the nanostructures of gold nanoparticles were sequentially triggered to assembly and disassembly by enzymes. This method provides a new chemical tool for precisely controlling the nanostructures. In addition, a controlled drug delivery system was also developed with mesoporous nanoparticles. The mesoporous silica nanoparticles with iron oxide core as drug carrier and capped by the oligonucleotides/oligonucleotides functionalized gold nanoparticles was studied in chapter six. Upon the treatment of enzyme with the oligonucleotides, the capped pores of mesoporous particles were opened to release the anticancer drugs. This system is multifunctional including controlled drug delivery and magnetic imaging. The multifunctional nanoparticles could serve as a new kind of stimuli-responsive drug delivery carrier and possess promising possibilities for biomedical applications.