Plasma-functionalized isotactic polypropylene assembled with conducting polymers for bacterial quantification by NADH sensing

Abstract

Rapid detection of bacterial presence on implantable medical devices is essential to prevent biofilm formation, which consists of densely packed bacteria colonies able to withstand antibiotic-mediated killing. In this work, a smart approach is presented to integrate electrochemical sensors for detecting bacterial infections in biomedical implants made of isotactic polypropylene (i-PP) using chemical assembly. The electrochemical detection is based on the capacity of conducting polymers (CPs) to detect extracellular nicotinamide adenine dinucleotide (NADH) released from cellular respiration of bacteria, which allows distinguishing prokaryotic from eukaryotic cells. Oxygen plasma-functionalized free-standing i-PP, coated with a layer (˜1.1 µm in thickness) of CP nanoparticles obtained by oxidative polymerization, is used as working electrode for the anodic polymerization of a second CP layer (˜8.2 µm in thickness), which provides very high electrochemical activity and stability. The resulting layered material, i-PPf/CP2, detects the electro-oxidation of NADH in physiological media with a sensitivity 417 µA cm-2 and a detection limit up to 0.14 × 10-3 m, which is below the concentration of extracellular NADH found for bacterial cultures of biofilm-positive and biofilm-negative strains.