Parallel Recording of Single Ion Channels: A Heterogeneous System Approach

The convergence of integrated electronic devices with nanotechnology structures on heterogeneous systems presents promising opportunities for the development of new classes of rapid, sensitive, and reliable sensors. The main advantage of em- bedding microelectronic readout structures with sensing elements is twofold. On the one hand, the SNR is increased as a result of scal- ing. On the other, readout miniaturization allows organization of sensors into arrays. The latter point will improve sensing accuracy by using statistical methods. However, accurate interface design is required to establish efficient communication between ionic-based and electronic-based signals. This paper shows a first example of a concurrent readout system with single-ion channel resolution, using a compact and scalable architecture. An array of biological nanosensors is organized on different layers stacked together in a mixed structure: fluidics, printed circuit board, and microelec- tronic readout. More specifically, an array of microholes machined into a polyoxymethylene homopolymer (POMH or Delrin) device coupled with ultralow noise sigma–delta converters current ampli- fiers, is used to form bilayer membranes within which ion channels are embedded. It is shown how formation of multiple artificial bi- layer lipid membranes (BLMs) is automatically monitored by the interface. The system is used to detect current signals in the pA range, from noncovalent binding between single, BLM-embedded α-hemolysin pores and β-cyclodextrin molecules. The current sig- nals are concurrently processed by the readout structure.