Investigations on factors influencing morphology of polypyrrole nanostructures for enzymatic biosensing applications

Abstract

Glucose plays an imperative role in human metabolism and any imbalance in blood glucose level leads to diabetes mellitus which is one of the major causes of death and disability in the world. With the drastic increase in the number of diabetic patients around the world and particularly in India, a pressing need has been felt to develop the point of care handheld testing devices which can provide continuous monitoring of glucose level of such patients. Thus, for the diagnosis and effective management of diabetes, the development of a cost-effective, simple, accurate, portable, and rapid sensor for glucose detection is required. For this aim, electrochemical biosensors, especially amperometric have been proved to be successful for the determination of glucose level in human blood. In this regard, Polypyrrole (PPy) nanostructures have been reported to be viable for the development of these devices due to low oxidation potential, high electrical conductivity, environmental stability, biocompatibility, etc. This work aims to achieve improved performance of amperometric glucose biosensor by enhanced material properties. In this work, we have fabricated enzymatic electrochemical biosensor for glucose detection utilizing PPy nanostructures as a support matrix. Different morphologies of PPy with the incorporation of different dopants viz. LiClO4 and p-TSA were obtained by a simple, single-step, template-free electrochemical polymerization technique. The work can majorly be divided into three parts: (i) Morphology and charge transfer resistance tuned LiClO4 doped PPy nanofibers network fabricated over Pt (Anode) coated glass substrates; (ii) High electroactive surface area PPy electrode with p-TSA as a dopant was fabricated with the aim of achieving higher enzyme loading (a pre-requisite for improved biosensor response) and (iii) Different immobilization techniques viz. physical adsorption and cross-linking were employed and compared. We have systematically studied dopant concentration, type of dopant and enzyme immobilization technique which has influenced the surface area, charge transfer resistance, and enzyme loading and thereby, influencing the performance of glucose biosensor in detail. The best biosensor was developed by crosslinking immobilization of GOx over PPy nanofibers network. The fabricated biosensor device showed a high sensitivity of 25-30 mA-cm􀀀2- M􀀀1 in a linear range of 0.1–2.5 mM with a response time of 30 s. Furthermore,the biosensor retained 92% of its initial sensitivity after storage of 14 days. The observed results show that PPy nanofibers with improved electrochemical properties can pave way to high performance biosensors.