A novel molecularly imprinted graphene-graphite conductive paper electrode for selective electrochemical detection of hyaluronic acid in cosmetic formulations.

Hyaluronic acid (HA), a glycosaminoglycan widely used in cosmetic and healthcare formulations, is valued for its moisturizing, viscoelastic, and regenerative properties. Accurate determination of HA in commercial products has therefore been considered essential for quality control and regulatory compliance. Although several chromatographic and spectroscopic techniques have been employed for HA quantification, their use has been restricted by high operational cost, complex operation, and labour-intensive sample preparation. In this work, a low-cost, flexible, and disposable conductive paint-based paper (CPP) electrode modified with an electropolymerized hyaluronic acid-imprinted poly(p-phenylenediamine) film [HA-MI-P(p-PD)@CPP] has been fabricated for the selective detection of HA. The conductive paint was prepared by dispersing polyacrylate with a graphene nanosheet-graphite (GNS-g) composite in chloroform to yield a mechanically stable and highly conductive substrate. After electropolymerization, the template removal and rebinding processes were investigated using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) with the [Fe(CN)6]3-/[Fe(CN)6]4- redox couple. The analytical performance of the imprinted electrode was assessed from DPV signals obtained before and after exposure to varying HA concentrations. The method achieved a low limit of detection (LOD) of 0.009 μM and a limit of quantification (LOQ) of 0.032 μM, exhibiting two linear response ranges (0.1-60 μM and 60-1000 μM). High recoveries (97-104%) and an imprinting factor exceeding 3, confirmed strong selectivity against structurally related interferents. Its affordability, environmental compatibility, and reliable sensing capability highlight its potential for on-site monitoring of HA in cosmetic and healthcare products.