Method for identifying and/or analyzing biological substances, present in a conductive liquid, device and affinity sensor used for implementing said method

A method of identifying and/or quantifying a charged biological substance in a conductive liquid medium using an apparatus comprising:

• a chamber for the conductive liquid medium;
• a affinity sensor disposed in said chamber;
• said affinity sensor comprising
• a semiconductor having an upper and a lower surface;
• said semiconductor having an ohmic contact disposed on its lower surface;
• an insulator layer disposed on the upper surface of said semiconductor;
• a plurality of probes in contact with said conductive liquid medium;
• said
• plurality of probes being disposed on the surface of said insulator layer;
• said
• plurality of probes comprising a recognition biological substance which is able to specifically hybridize with a charged biological substance present in the conductive liquid medium, whereby specific pairings of charged biological substances with their complementary recognition biological substances are formed;
• means for biasing the semiconductor with respect to the conductive liquid medium;
• means for illuminating the semiconductor;
• means for measuring a photopotential Vph at the terminals of the affinity sensor;
• means for converting the detected signals into Vfb variations which are induced by a charge-effect phenomenon associated with said pairings modifying the surface electric charge of the affinity sensor;
• and
• means for calculating and interpreting the ΔVfb variations in terms of the identification and/or quantitative determination of the charged biological substances;
• wherein the method comprises
• providing an unlabeled recognition biological substance as a probe;
• contacting the charged biological substance with the unlabeled recognition biological substance, whereby specific pairings of charged biological substances with their complementary recognition biological substances are formed;
• said specific pairings modifying the surface electric charge of the affinity sensor;
• biasing the semiconductor to ensure that the Fermi level corresponds approximately to, or exceeds, the intrinsic Fermi level at the surface of the semiconductor;
• exposing the semiconductor to periodic illumination comprising photons having an energy greater than or equal to the band gap energy of the semiconductor;
• measuring the photopotential Vph at the terminals of the affinity sensor;
• determining the complex impedance of the affinity sensor from the photopotential Vph, determining the variations ΔVfb of the semiconductor which are induced by a charge-effect phenomenon associated with said specific pairings of the charged biological substances with their complementary recognition biological substances;
• to the exclusion:
• (i) of the variations resulting from possible charge and/or charge-transfer effects caused by enzyme-catalyzed chemical reactions in which some of the substances to be detected are consumed;
• and
• (ii) and of the variations in the photoresponse which are associated with the appearance in the conductive medium of at least one tracer product capable of being revealed through pH variations or redox potential variations and/or through radiation-absorbing or radiation emitting labels;
• and
• identifying and/or quantifying the charged biological substances in the conductive liquid medium by interpreting the received signals.