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Abstract
Porous silicon (PSi) is an ideal platform for label-free biosensing, and the development of PSi patterning will open a pathway to the development of highly parallel PSi biosensors. The primary aim of this research is to develop a PSi photonic crystal based microarray to monitor molecule secreted from cells by the optical reflectivity properties. In order to achieve the research aim, a number of works must be achieved: 1) to provide a reference for monitoring the analyte of interest from cell microarrays, real-time monitoring of the analyte of interest in multiple spots must be achieved. 2) A suitable microfabrication technique must be developed, so that different chemical functionalities can be introduced to discrete PSi surface and can be used to mediate special control of the cell adhesion to form microarrays. 3) The fabricated PSi microarrays must be applied to monitor and read out the cellular response from different numbers of cells and even single-cell level. In relation to the research aims, Chapter 3 presents the work of using PSi chip modified with gelatin to detect protease from both free protease solution and live cells. The monitoring is carried out continuously and read out from multiple locations over the surface. Chapter 4 introduces a photolithographic strategy for chemically patterning the PSi with Ti hard mask, and characterization methods including IR microscopy and reflectivity scanning are explored to obtain the spatial information from the patterned PSi chip. Chapter 5 presents a work based a photolithographic strategy with photoresist mask instead of Ti mask. Fluorescence labelled BSA and RGD peptide are conjugated to PSi surface to demonstrate the ability of patterning biological species. Detection of protease from different array elements on the patterned PSi chip was demonstrated by monitoring blue-shifts in the reflectivity resulted from gelatin cleavage by protease. In Chapter 6, cell microarray is achieved on PEG hydrogel patterned PSi surface using direct photopatterning method. Optical monitoring of live cells from the cell microarray is carried out by measuring the optical shift during cell osmotic lysis. A preliminary result of monitoring stimulated cells using the cell microarray is also carried out. Chapter 7 concludes the work with a discussion of lessons learned and the perspectives for future progress with PSi as a microarray platform for further biomedical applications.