Bio-functionalization of silicon and its applications in mammalian and cancer cell manipulation and proliferation

Currently fabricated bio-matrices lack important characteristics such as nanometer scale, ‘bumpy’ morphology and an interlinked structure. Therefore, cells cultured on such matrices may not truly represent phenotypes of cells grown in the natural environment. This thesis deals with the synthesis of a three dimensional nanofibrous silicon matrix that is interlinked and possesses a ‘bumpy’ structure that mimics the natural extra cellular matrix. This silicon matrix can be tailored to suit applications of cell proliferation and manipulation. Cell-biomaterial studies show that osteoblasts and fibroblasts proliferated by 300% on three dimensional nanofibrous matrix compared to virgin silicon. To induce controlled cell proliferation, the addition of gold to the silicon matrix was perceived. The phase of gold was altered and combined with silicon forming a unique hybrid structure that prevented the growth of cells in areas of increased gold concentration. Increased gold concentration indicated lower adhesion forces and reduced zeta potentials which consequently lead to decreased cell growth. In addition, the interaction of cancer cells with the three dimensional silicon and gold-silicon hybrid nanofibrous network was studied. Results indicate a 96% reduction in cancer cells compared to virgin silicon. The reduction in cells is attributed to- different phases of silicon and silicon oxides in nanoparticle form, the encapsulation of cells by the nanofibers and apoptosis of cells owing to nanoparticles entering cells passively. To control the growth of cells, silicon surface bio-functionalization was performed to study manipulation of mammalian cells such as fibroblasts as well as cervical and breast cancer cells. The manipulative property is attributed to a mixture of phases of silicon and silicon oxides as well as varied crystal orientations of silicon. It is hypothesized that the mixtures of phases on the substrate alter its surface morphology and consequently induce cell manipulation. Therefore, laser irradiated bio functionalized silicon and its nanostructures are a versatile material for biomedical applications. Based on the process of bio functionalization, both proliferation and cell control and manipulation was achieved in this thesis.