Nanostructured Gold-Modified Laser Scribed Graphene Biosensor Based on Molecularly Imprinted Polymers

Abstract

Recently, laser scribed graphene (LSG) technology has shown great potential for the development of a plethora of sensing platforms due to its high sensitivity, 3D porous structure, and flexibility. Molecularly imprinted polymers (MIPs) have shown high potential as recognition elements for many applications such as biosensing. Hence, we report in this thesis a novel biosensing platform that utilizes nanostructured gold to enhance the performance of LSG sensors coupled with a biomimetic MIP biosensor. To the best of our knowledge, this is the first report of a nanostructured gold modified MIP based LSG biosensor to detect HER-2, which is an important breast cancer biomarker. HER-2 positive breast cancer is more aggressive and does not respond to the same treatment as standard breast cancer. As such, a simple and accurate sensing approach is highly needed for early detection of this type of cancer biomarkers. The LSG sensor platform was fabricated by irradiation of polyimide substrates using a CO2 laser under optimized conditions. Nanostructured gold was electrodeposited onto LSG to enhance its sensitivity and active surface area. Deposition parameters such as deposition voltage, deposition time, and gold chloride (HAuCl4) concentration were optimized to yield complete nanostructured gold coverage and enhanced electrical conductivity of LSG-Au electrodes. A deposition voltage of -0.9 V at 50 mM HAuCl4 for 4 minutes proved to be the optimal condition for gold deposition to yield a 150% peak current enhancement. To fabricate our MIP biosensor, 3,4- ethylenedioxythiophene (EDOT) was chosen from several functional monomers to form PEDOT due to its high conductivity and synergy with nanostructured gold. Electropolymerization of EDOT is performed after adsorbing 0.4mg/mL of HER-2 on the LSG-Au electrode for 20 min. The efficiency of LSG-Au-MIP was optimized by choosing an appropriate extraction agent and HER-2 concentration to be adsorbed on gold. The developed sensing strategy could differentiate between three rebinding concentrations of 10 ng/mL, 100ng/mL, and 200 ng/mL, which is sufficient to determine the HER-2 status of breast cancer since the clinical cut-off is 30.5ng/mL. The developed sensing strategy showed a high degree of novelty and could be useful for the non-invasive detection of cancer biomarkers.