In situ electrostatic assembly of porphyrin as enhanced PEC photosensitizer for bioassay of single HCT-116 cells via competitive reaction

Nowadays, synthesis of novel organic photosensitizer is imperative but challenging for photoelectrochemical (PEC) assay in analytical and biomedical fields. In this work, the PEC responses enhanced about 4.3 folds after in situ electrostatic assembly of 1-butyl-3-methylimidazole tetrafluoroborate ([BIm][BF4]) on meso-tetra (4-carboxyphenyl) porphine (TP), which was first covalently linked with NH2 modified indium tin oxide electrode ([BIm]+-–TP-NH2-ITO). Moreover, the [BIm]+-–TP-NH2-ITO showed a much larger photocurrent in a water/dimethyl sulfoxide (DMSO) binary solvent with a water fraction (fw) of 90%, which displayed 6.7-fold increase over that in pure DMSO, coupled by discussing the PEC enhanced mechanism in detail. Then, the PEC signals were sharply quenched via a competitive reaction between magnetic bead linked dsDNA (i.e., initial hybridization of aptamer DNA with linking DNA) and HCT-116 cells (closely associated with CRC), where the liberated L-DNA stripped the [BIm]+ from [BIm]+-–TP-NH2-ITO. The PEC detection strategy exhibited a wider linear range (30 ∼ 3 × 105 cells mL–1) and a lower limit of detection (6 cells mL–1), achieving single-cell bioanalysis even in diluted human serum sample. The in situ assembly strategy offers a valuable biosensing platform to amplify the PEC signals with advanced organic photosensitizer for early diagnosis of tumors.