Abstract
In this study, a biosensor was fabricated by growing carbon nanotubes (CNTs) directly on polyimide flexible substrate at low temperatures (400 °C) with chemical vapor deposition (CVD) process. Thereafter, a biocompatible polymer (parylene) was coated on the surface area without CNTs as an insulator for future applications in flexible biosensors for in-vivo sensing. The surface of CNTs was modified with functional groups by utilizing UV-ozone, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC), and N-hydroxysuccinimide (NHS) treatment to improve the biocompatibility for the following conjugation of protein. Following that, the sensing surface was modified with anti-human serum albumin (AHSA), blocked by bovine serum albumin (BSA), and then conjugated with different concentrations of targeted human serum albumin (HSA) for HSA detection. The electrical properties of the biosensors, applied with various HSA concentrations, were measured and quantified by using an electrochemical impedance spectroscopy (EIS) system under AC conditions. Results showed that the impedance change was well correlated to the HSA concentration from 2 * 10^-12 to 2 * 10^-1 mg/ml, and exhibited a detection limit of the 3 * 10^-11 mg/ml. In summary, the feasibility of the CNTs flexible biosensor for HSA detection was demonstrated by utilizing electrochemical impedimetry to quantify human serum albumin concentration. Compared to other CNTs flexible biosensors, because of the employment of CVD process and the 3D structure of the direct-growth CNTs, the biosensor proposed in this work could be fabricated by a simpler process and provide a good detection limit. It shows a great potential for future application of wearable biosensor and implanting detection.