Rapid photosensitive cell membrane damage process of novel thiophene for microelectrode

We report a new aspect of rapid (< 30 seconds) light-induced cell membrane damage photosensitized by 5,5″-bis(aminomethyl)-2,2′:5′,2″-terthiophene dihydrochloride (BAT), which is a water-soluble α-terthienyl analogue and a monomer of conducting polymer, using a high-power laser (light intensity 1.6 W cm^-2). A microelectrode insertion process to cell could be improved by pinpoint use of the photosensitizing (PS) effect to degenerate cell membranes prior to insertion. This avoids mechanical perforation of the membrane when the pipette tip makes contact with the cell. Three toxic processes of the cells by BAT can be identified: the first is a non-light-mediated toxicity dependent on BAT exposure time; the second is a phototoxicity independent of BAT exposure time when the BAT concentration is 2 - 10 μM range; and the third is a phototoxicity dependent on BAT exposure time with 20 μM of BAT concentration in case that cytotoxicity decreases when α-tocopherol, an anti-oxidant, is added to a cell membrane. This is the typical phototoxicity that the phospholipid peroxidation chain reaction triggered by a reactive oxygen species generated by a triplet state of BAT.