In-situ chemical modification of printed conducting polymer films for specific glucose biosensing

Conductive polymers, such as poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), can be used for specific biosensing after its surface is modified with functional groups. Herein, we report a simple two-step surface modification method for commercially available PEDOT:PSS films printed on a flexible substrate. The derivatization process involves: (1) the introduction of an ethylenediamine linker for conjugation with the biorecognition element by activating the sulfonate group in PSS with an acid chloride reaction; and (2) the introduction of FPBA into the ethylenediamine linker. As a proof of concept, 4-carboxy-3-fluorophenylboronic acid (carboxy FPBA) is covalently introduced to the side chain of the PSS dopant in the conductive layer. FPBA serves as a selective molecular recognition element for diol compounds, including glucose, at neutral pH. Continuous glucose monitoring is achieved by label-free potentiometry using FPBA-functionalized commercial PEDOT:PSS films. Negative potential responses with glucose are successfully achieved in ideal and realistic buffer solutions with or without 1% fetal bovine serum (FBS) because of the complexation of FPBA. The dynamic range of the enzyme-free sensor covered physiologically relevant blood glucose levels of 70–140 mg/dL. The developed method is suitable and cost effective for the mass production of biosensors as it can be applied to a large surface area at once. Furthermore, various ligands and receptors can be introduced onto commercial PEDOT:PSS films using this technique. Hence, the proposed method has potential applications in wearable and implantable biosensors.