Optical and Electrical Si-Based Biosensors: Fabrication and Trasduction Issues

Abstract

In this work we discussed feasibility studies and examples of biological molecules integration in Si-based miniaturized devices. We investigated three main issues: (i) device surface functionalization, (ii) biological molecule functionality after immobilization and (iii) biosensor working principle using both electrical and optical transduction mechanisms. In the first case the idea is to fabricate electrolyte-insulator-semiconductor (EIS) and, in the near future, ion-sensitive field effect transistor (ISFET) biosensors. The electrical characterization of MOS-like capacitors with ssDNA anchored on the SiO 2 dielectric, allowed us to conclude that the structures tested are sensitive to DNA immobilization and hybridization, as demonstrated by a positive shift in the flat band voltage after ssDNA immobilization and by a further shift after prefect match hybridization. The optical transduction mechanism, using an approach closer to commercial devices (e.g. DNA-chip) is based on the use of pixelated solid state photon-detectors (Silicon Photomultipliers, SiPM). We showed this new device can be used to replace traditional optical detector in DNA-chip applications and allows designing new optical detection systems based on photon counting operation.

CY5 fluorescence measured with silicon photomultipliers

“…On the other hand, when CY5 is deposited on the sample, the fluorescence behavior is completely different, being roughly constant in the range from 25° to 80° (Fig. 2b), to confirm the emission isotropy [14]. At 80° the detected fluorescence reduces since the detector is about on the same optical axis with the slide lateral interface.…”

Microfluidics: Innovations in Materials and Their Fabrication and Functionalization

“…Some resins do not have absorbers that interfere with visible wavelength measurements; devices made from these optically clear resins have been used to detect bioluminescence related to ATP. 159 A silicon photomultiplier was added to the device to detect the luminescence and determine the concentration of ATP at low nanomolar levels. Analyses in these devices are rapid but extension to clinical or other medically relevant samples still needs to be shown.…”