Electrochemical properties of hydroxyapatite immobilization material for potential cytosensor fabrication

Abstract

Aim: The biorecognition unit of an electrochemical biosensor requires molecules that are immobilised to serve as a bridge between the recognition unit and the transducing surface. Unique materials that enhance immobilisation of biorecognition molecules and improve electrochemical signal transduction are important in overcoming challenges based on the sensitivity of biosensors. In this regard, the electrochemical properties (EPs) of hydroxyapatite (HAp) material for the direct immobilisation of cells was investigated. Methods: Snail shell HAp (SHAp) material was synthesised from Achatina achatina snail shells and phosphate-containing solutions. The SHAp material was characterised using X-ray diffractometry (XRD), Fourier transform infrared (FTIR) spectroscopy, and Raman spectroscopy to determine the structural configuration, after which it was blended with a conductive polymer [poly(3,4-ethylenedioxythiophene): poly-4-styrene sulfonate (PEDOT: PSS)] to improve the electrochemical responses. The SHAp/PEDOT: PSS blend was used to modify a screen-printed carbon electrode (SPCE) by drop-casting, followed by seeding of pheochromocytoma (PC 12) and human embryonic kidney (HEK)-293T cells on the modified SPCE to record the EP using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Red blood cells (RBCs) were used as a control. Results: The CV analysis showed lower peak currents for HEK 293T (50 µA) and PC 12 (120 µA) compared to the RBC (230 µA). Also, the EIS showed impedance values of 0.70 for HEK 293T, 0.62 for PC 12, and 0.52 mΩ for RBC. The findings indicate that SHAp/PEDOT: PSS enables the differentiation of cell proliferation signals through voltammetric and impedimetric measurements. Conclusions: The unique current and impedance differences among the cells could serve as potential markers for rapid cell detection.