Fabrication of porous silicon photonic crystal microparticles: towards single cell sensing

摘要

This thesis presents research results obtained on developing novel porous silicon microparticle biosensors for the applications in cell biology. A primary aim of this research was to build up microbiosensors based on porous silicon rugate filters to show the potential for sensing single cell activity. Porous silicon is an ideal biomaterial due to its biocompatibility, tunable optical properties and metastability for chemical modification on surfaces. For a typical porous silicon biosensor, it requires 1) a sensitive transducer which transforms biological changes to easily read-out optical signals; 2) a robust chemical modification strategy to stabilize rugate structures and prevent porous silicon from degradation, and importantly facilitate further functionalization; 3) a bio-interface for recognizing targeted cells and even capturing sensing targets. Porous silicon rugate filters were chosen as it features a high reflectance stop-band in reflectivity spectrum. A robust chemical route based on hydrosilylation and copper(I)-catalyzed alkyne azide cycloaddition (CuAAC, also known as “click”) reaction is introduced to selectively decorate hydride-terminated porous silicon external surfaces and inner pores. Hence, a porous silicon biosensor whose external surfaces are grafted with cell-capture peptides for interacting with sensing targets while its hydrophobic internal surfaces to stop hydrophilic biomolecules from penetrating the pores is realized. The stability of these modified porous silicon particles in different biological media, including cell culture medium and human blood sample, is reported and shown to meet the sensing requirement in real bio-systems. Towards single cell sensing, covalently antibodies-immobilized porous silicon particles are prepared for specifically interacting with cells. The surface-bound antibodies are shown to be active in capturing appointed biomolecules and even antigen-presenting cells. Cell monitoring based on antibodies-coupled porous silicon particles is therefore demonstrated to be possible in this thesis.