Haptenation of skin sensitizers with cysteine and gold nanoparticles modified screen printed carbon electrode analyzed using impedance technique

Abstract

Skin sensitization is defined as an allergic response to a skin sensitizer upon contact with the skin. Skin sensitization is induced through covalent binding of a skin sensitizer to skin proteins (haptenation process). In this research work, the working electrodes of screen printed carbon electrodes (SPCEs) were modified by electrodepositing gold nanoparticles (AuNPs), addition of thiourea and then followed by self–assembly of AuNPs and cysteine (designated as ETSC). The main purpose of this research was to study the interaction of skin sensitizers with the cysteine and gold nanoparticles modified screen printed carbon electrode (SPCE) analyzed using impedance technique. The interaction of maleic anhydride (as extreme/strong skin sensitizer) with the cysteine modified SPCE was found to result in high changes in the value of charge transfer resistance of skin sensitizer (ΔRCTskinsensitizer) compared to moderate sensitizer (isoeugenol) and weak/non skin sensitizer (glycerol). The ETSC modified SPCE with skin sensitizers were characterised using Fourier–Transform infrared spectroscopy–attenuated total reflectance (FTIR–ATR), atomic force microscopy (AFM) and electrochemical impedance spectroscopy (EIS). The presence of skin sensitizers on the working electrode of ETSC modified electrode was detected by FTIR–ATR. AFM images indicated different patterns with different surface roughness for extreme/strong, moderate and weak/non skin sensitizers. Using EIS, the estimation for fractional surface coverage (θIS) of ETSC modified SPCE when contacted with maleic anhydride was higher than isoeugenol and glycerol. Other than that, the active site radius (ra), and the distance between two adjacent sites (2rb) for ETSC modified SPCE when contacted with maleic anhydride were shorter than the ra and 2rb obtained for isoeugenol and glycerol, indicating higher surface average roughness for ETSC modified SPCE that was contacted with maleic anhydride. Data obtained from EIS agreed with images obtained using AFM. The adsorption kinetic studies for ETSC modified SPCE with skin sensitizers showed that the skin sensitizers displayed Langmuir isotherm adsorption. This work showed that the ETSC modified SPCE has the potential to be employed for the screening of potential skin sensitizers during the early stage of cosmetic and personal care products development.