Cell-to-cell scanning in capillary electrophoresis

A widespread limitation in using cell-based biosensors for repetitive chemical analysis is loss of agonist-induced response caused by receptor desensitization. We overcome this problem by scanning an array of immobilized cells underneath a capillary electrophoresis column outlet. In this way, electrophoretically fractionated components that exit the separation capillary are always directed onto cells previously unexposed to receptor agonists. To demonstrate this concept of response recovery using a scanning format, we have chosen the bradykinin B-2 receptor system in the NG108-15 cell line, which is known to undergo desensitization. Whereas four subsequent injections of 250 mu M bradykinin separated by 120 s are found to reduce the NG108-15 cell response markedly, scanning to new cells can fully restore the response during the separation, Furthermore, by pretesting individual NG108-15 cells for an agonist response and then later scanning back to the same cell, we achieved a 100% success rate in detecting bradykinin in subsequent electrophoretic separations.