Planar Junctionless Field-Effect Transistor for Detecting Biomolecular Interactions

Abstract

Label-free field-effect transistor-based immunosensors are promising candidates for proteomics and peptidomics-based diagnostics and therapeutics due to their high multiplexing capability, fast response time, and ability to increase the sensor sensitivity due to the short length of peptides. In this work, planar junctionless field-effect transistor sensors (FETs) were fabricated and characterized for pH sensing. The device with SiO2 gate oxide has shown voltage sensitivity of 41.8 ± 1.4, 39.9 ± 1.4, 39.0 ± 1.1, and 37.6 ± 1.0 mV/pH for constant drain currents of 5, 10, 20, and 50 nA, respectively, with a drain to source voltage of 0.05 V. The drift analysis shows a stability over time of −18 nA/h (pH 7.75), −3.5 nA/h (pH 6.84), −0.5 nA/h (pH 4.91), 0.5 nA/h (pH 3.43), corresponding to a pH drift of −0.45, −0.09, −0.01, and 0.01 per h. Theoretical modeling and simulation resulted in a mean value of the surface states of 3.8 × 1015/cm2 with a standard deviation of 3.6 × 1015/cm2. We have experimentally verified the number of surface sites due to APTES, peptide, and protein immobilization, which is in line with the theoretical calculations for FETs to be used for detecting peptide-protein interactions for future applications.

Functionalized oxide biosensor interfaces for in-situ, acid-modulated peptide synthesis

“…For peptide synthesis, however, conditions are more demanding than for nucleotide synthesis, i.e., acidic conditions required for stepwise deprotection cycles are more extreme, and possible side reactions of amino acid side chains must be averted. We recently described an improved reactor concept for electrochemical acid production, and demonstrated that it affords good yields in the local deprotection of acid-labile groups in organic electrolytes compatible with peptide synthesis [12,13]. To achieve high density microarrays, these electrochemical reactors can be miniaturized and integrated with MOS circuits.…”

“…In tune with this innovation, we have revisited peptide synthesis protocols relying on acid-labile protection schemes, to evaluate the feasibility of obtaining high purity peptides via in-situ synthesis on semiconductor oxide surfaces similar to those used in our FET biosensors [13]. Our goal was to validate a suitable surface capable of simulating the chemical conditions of semiconductors or metal oxides which form the interface of today's commercial FETs.…”

Acid-Modulated Peptide Synthesis for Application on Oxide Biosensor Interfaces

“…In tune with this innovation, we have revisited peptide synthesis protocols relying on acid-labile protection schemes, to evaluate the feasibility of obtaining high purity peptides via in situ synthesis on semiconductor oxide surfaces similar to those used in our FET biosensors [16,17]. Our goal was to validate a suitable surface capable of simulating the chemical conditions of semiconductors or metal oxides which form the interface of today's commercial FETs.…”