DETERMINATION OF NICKEL ACCUMULATION IN SINGLE BIOLOGICAL CELLS USING PORPHYRINIC MICROSENSORS

Carbon fiber ultramicroelectrodes modified with a conductive polymeric film of tetrakis(3-methoxy-4-hydroxyphenyl)nickel porphyrin (< 1-3-mu-m diameter) were Used for monitoring the concentration of unbound nickel in individual BC3H-1 myocytes and H4-11-C3 rat hepatoma cells. Detection limits of 8 X 10(-6) M and 1 X 10(-6) M, respectively, were obtained. A method is described for fabricating sensors with the length and area of the electroactive surface appropriate for the dimensions of the cells under investigation. The method consists in carefully burning a fiber coated with wax in a controlled temperature gradient obtained with a microburner to sharpen the tip. The length and shape of the electroactive area obtained are controlled by the thickness of the wax coating, which is determined by the temperature of the melted wax. The sharpened tip of the 0.5-1-mu-m fiber was covered electrochemically with 10-90 monolayers of polymeric porphyrin, demetalated, implanted and used for nickel(II) accumulations and current determinations.