Fundamental studies on chemical sensing based on receptor-incorporated bilayer lipid membranes

The present paper describes analytical aspects of receptor-incorporated bilayer lipid membranes (BLMs) sensors based on transmembrane signaling: (i) membrane potential change, (ii) membrane permeability change and (iii) active transport. The receptors used in the present study included synthetic and natural ionophores as well as bioreceptors, such as Na⁺, K⁺ -ATPase, glutamate receptor ion channel and Na⁺/D-glucose cotransporter. The receptors were incorporated into planar BLMs formed by the folding and tip-dip methods. The membrane capacitance and current noise of the BLMs formed by both methods were also investigated. By comparing the conductance of BLMs with and without receptors, an experimental criterion for judging the successful incorporation of receptors into the BLMs was achieved. The response characteristics of the constructed BLM sensors were considered in terms of their principles, sensitivity, selectivity and amplification ability. The potentiometric responses of BLM sensors based on synthetic ionophores were significantly improved by the simultaneous incorporation of anionic sites, providing a basis for quantitative BLM sensors. The highly sensitive detection of agonists with glutamate receptor-based BLM sensors was also demonstrated. Synthetic ionophore-incorporated BLM sensors were constructed that induce analyte-triggered membrane permeability changes, attributed to permeation of primary ions as well as counter anions. The future prospects of receptor-incorporated BLM sensors were also considered.