Inorganic surfaces modified by TAT peptides: Tuning lithographic strategies, surface science characterization, and biocompatibility assessment

Youngnam Cho, Purdue University

Abstract

The complexation of TAR RNA and the TAT protein is one of the most studied interactions. The basic question that researchers are trying to address is centered on the specificity and strength of binding of the arginine rich region of the TAT protein with the target RNA. The TAT peptide molecules were immobilized on surfaces using three different methodologies: adsorption from solution, microcontact printing, and scanning probe lithography. Features as small as 100 nm were generated by self-assembling approaches on three different inorganic surfaces: Au, Si/SiOx and GaAs. The nanoscopic features generated by scanning probe lithography were compared with monolayers created from adsorption from solution and microcontact printing to understand the structure of the TAT peptide monolayer generated by the different methods. The modified surfaces were characterized by Contact Angle Measurements, Atomic Force Microscopy (AFM), X-ray Photoelectron Spectroscopy (XPS), and Fourier Transform-Infrared Reflection Absorption Spectroscopy (FT-IRRAS). The thesis work also explored the use of chemical force microscopy in order to quantify the interaction between TAR RNA and Tat peptide lithographic features on GaAs. An AFM tip functionalized with TAR RNA was used in order to record adhesion maps. Specific vs. non-specific interactions were investigated under different pH conditions. The findings showed an increased interaction between TAR RNA and the peptide sequence that is rich in arginines. The final portion of this work focused on modifying GaAs in order to make it more biocompatible because the unprotected GaAs surface can release heavy metal compounds such as AsOx which are toxic to living cells. Experiments were performed to compare the cell spreading behavior on the GaAs substrates modified by different chemical approaches. The results suggest that when the toxicity of the GaAs surface is reduced or eliminated, the cells' viability and spreading depend on the chemical and topographical nature of the surface.

Degree

Ph.D.

Advisors

Ivanisevic, Purdue University.

Subject Area

Analytical chemistry

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