BIOFUNCTIONALIZATION ON HYDROGEN-TERMINATED SILICON(111) SURFACES
Liu, Kai 1985-
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This thesis describes our attempt to develop a versatile bioelectrical platform based on our understanding of both surface chemical and physical processes. We envisioned the fine tuning of such platform through modification strategies such as “Click” chemistry, which allows us to control its electrochemical property. Such an endeavor would greatly benefit the study of neurological disorder diseases by providing an ideal neural culture platform, which currently presents a great challenge in interfering with neural system in vivo. Several major tasks involved in our research were: 1) improvement of organic film passivation apparatus for high quality film formation to prevent oxidation of underlying bulk silicon; 2) development of easily reproducible acetylenylated base layer on silicon surfaces for convenient introduction of organic moieties; and 3) development of novel redox biomolecule which allows attachment to acetylenylated monolayer via step-wise procedure, as well as direct electron transfer between the redox biomolecule and underlying silicon substrate. To realize our vision, we built a film passivation apparatus that provides near ideal ultra-high vacuum (UHV) condition for adsorbate grafting. The hypothesis is that by removing reactive oxygen species, a densely packed monolayer can be formed, which protects underlying bulk silicon from oxidation in both aqueous and organic electrolytes. We demonstrated monolayers presenting oligo(ethylene glycol) (OEG) prepared using this apparatus remained resistant to model protein fibrinogen after 56 days in phosphate buffer saline (PBS). In order to incorporate new moieties to our platform, we optimized the design of trimethylgermanyl protected acetylenylated self-assembling molecule (SAM). Subsequently, we grafted OEG onto acetylenylated base layer via a step-wise strategy to incorporate the ability to block nonspecific bindings. The anti-biofouling property of the grafted film was tested to be similar to that of the OEG-presenting film formed by pre-assembled strategy. To develop a versatile method to tune the electrochemical property of the films, we immobilized electrochemical active ferrocene moiety onto the acetylenylated silicon substrates. Cyclic voltammetry was employed to study the electrochemical property of the ferrocene grafted films. By optimizing the design of the biocompatible acetylenylated base layer, we established a simple modular approach to produce SAMs to study the electrochemical behavior of a well-studied model redox molecule.