Hybrid Silicon-Based Nanomaterials Synthesized Via Femtosecond Laser For Theranostics Applications
Authors: Keshavarz Meysam 
Published: May 2021

Biocompatibility and bio-stability are two very important criteria of the materials being used in biology and biological related applications. Among biocompatible materials, Silicon has been widely used in biomedical applications such as logistic for drug delivery and scaffolds for tissue engineering. Therefore, Silicon is chosen to be further investigated in terms of its potential therapeutic and diagnostic applications. The main objective of this thesis is to explore capabilities
of silicon-based nanomaterials on therapeutic and diagnostic of cancer HeLa and mammalian Fibroblast cell lines. The uniqueness of silicon-based nanomaterials synthesized in this study relies on utilization of femtosecond laser, a versatile yet precise method to generate nanoscale siliconbased materials.

In the initial phase of this study, the need for manufacturing an alternative tool to modulate cells behavior is addressed. During this phase, it is shown that Induced Residual Stress (IRS) onto the Silicon chip via Ultrashort Pulsed Laser (USPL) irradiation is remarkably capable of remotely tuning cellular behavior by which the fate and directionality of seeded cells could be modulated. The second phase is dedicated to synthesis of a novel nanostructure to overcome the limitations of using Silicon-based bio-template for therapeutic applications. Thus far, Nano-scale silicon material has been employed in the form of either nanoparticles (NPs) or 3-D structure for drug delivery and scaffold respectively. Here, a self-assembled Silica Nano-web (SNW) that concurrently exhibits the therapeutic and proliferative attributions of NPs and 3-D structure is introduced. This SNW also demonstrates selective functionality by which mammalian cells and cancer cells are treated differently.

The third phase of this study focuses on diagnostic applications of the silicon-based materials. In this phase, a label-free multiplex photoluminescent silicon nano-probe (PLSN-probe) as a potential substitute for quantum dots (QDs) in bioimaging is synthesized. An inherently nonphotoluminescent silicon substrate is altered to create the PLSN-probe, which overcomes the major drawbacks of presently available QDs. The PLSN-probe not only demonstrates unique optical properties that can be utilized for bioimaging but also exhibits cell-selective uptake that allows the differentiation and diagnosis of HeLa and fibroblast cells. Last but not least, the final study is a unique approach of using polygonal Silicon quantum-probe (polygonal Si-QP) that utilizes a surface-enhanced Raman scattering (SERS) for diagnosis and differentiating of cancerous HeLa and fibroblast cells. It is demonstrated that the polygonal SiQPs could be used for in-situ live cell analysis. Live Raman sensing has also exhibited promising outcome by which tracing of chemical transition in a cell could lead us to a better understanding of cellular changes.

The obtained results indicate multifunctional feasibility of nano/quantum scale silicon based structures for therapeutic, bioimaging and diagnosis. The prospect applications of this thesis could lead to future studies and ultimately, new frontiers for universal cancer cell diagnosis.