The correlation of haptenation of gold nanoparticles and cysteine modified screen printed carbon electrode by impedance technique with local lymph node assay data

Skin sensitization occurs when a skin sensitizer binds covalently to skin proteins through the haptenation process. The objective of this study was to correlate the electrochemical impedance spectroscopy (EIS) data of a screen printed carbon electrode (SPCE) modified with cysteine and gold nanoparticles (AuNPs) with local lymph node assay (LLNA) data as a potential skin sensitizer biosensor. The EIS was used to quantify variations in charge transfer resistance of skin sensitizers (Delta R-CT(skin sensitizer)) due to different binding rates of skin sensitizers to cysteine. SPCE was modified through electrodeposition of AuNPs/thiourea/self-assembly of AuNPs/cysteine (assigned as ETSC) for the detection of skin sensitizers. Surface analysis of modified SPCEs using FESEM and EDX revealed a smooth surface with an uneven distribution of cysteine with AuNPs molecules. The ETSC modified SPCE showed a significant skin sensitizer biosensor since the Delta R-CT(skin sensitizer) readings were increased proportionally to the strength of the skin sensitizers, with strong/extreme skin sensitizers displaying higher Delta R-CT(skin sensitizer) readings compared to moderate and weak/non-skin sensitizers. The skin sensitization analysis from this work was compared to LLNA (animal study), human cell line activation (h-CLAT), direct peptide reactivity assay (DPRA), and KeratinoSens (TM), surface plasmon resonance (SPR) matched the categorization of LLNA in the following descending order: 96%, 92%, 82%, 70%, 70%, and 12%. With just an 8% mismatch with LLNA data, the EIS approach used in this study could be used as a screening tool for skin sensitizers.