Combination of Aptamer Amplifier and Antigen-Binding Fragment Probe as a Novel Strategy to Improve Detection Limit of Silicon Nanowire Field-Effect Transistor Immunosensors

Abstract

Detecting proteins at low concentrations in high-ionic-strength conditions by silicon nanowire field-effect transistors (SiNWFETs) is severely hindered due to the weakened signal, primarily caused by screening effects. In this study, aptamer as a signal amplifier, which has already been reported by our group, is integrated into SiNWFET immunosensors employing antigen-binding fragments (Fab) as the receptors to improve its detection limit for the first time. The Fab-SiNWFET immunosensors were developed by immobilizing Fab onto Si surfaces modified with either 3-aminopropyltriethoxysilane (APTES) and glutaraldehyde (GA) (Fab/APTES-SiNWFETs), or mixed self-assembled monolayers (mSAMs) of polyethylene glycol (PEG) and GA (Fab/PEG-SiNWFETs), to detect the rabbit IgG at different concentrations in a high-ionic-strength environment (150 mM Bis-Tris Propane) followed by incubation with R18, an aptamer which can specifically target rabbit IgG, for signal enhancement. Empirical results revealed that the signal produced by the sensors with Fab probes was greatly enhanced compared to the ones with whole antibody (Wab) after detecting similar concentrations of rabbit IgG. The Fab/PEG-SiNWFET immunosensors exhibited an especially improved limit of detection to determine the IgG level down to 1 pg/mL, which has not been achieved by the Wab/PEG-SiNWFET immunosensors.

Graphene-based hybrid electrical-electrochemical point-of-care device for serologic COVID-19 diagnosis

“…The reached LOD value by G-PNR-AuNP/RBD, as well as its sensitivity were compared to the values obtained for general immunoglobulin detections by FETs. For example, G-PNR-AuNP/RBD LOD was comparable to the obtained by Vu and co-authors using a GFET (1.0 pg mL -1 ) ( Vu et al, 2021 ), and remarkably lower than the reached by Minamiki and co-authors applying an OFET (0.62 μg mL -1 ) ( Minamiki et al, 2014 ). The sensitivity of G-PNR-AuNP/RBD obtained by the slope of the calibration curve could not be compared to the values reported by different serological assays due to incompatibility of units.…”

Electrochemical Affinity Sensors Using Field Effect Transducer Devices for Chemical Analysis

“…Since 2015, twelve papers were published on SiNW FET for the detection of biomarkers for different diseases (Table 4): bladder cancer [83], oral cancer [84], lung cancer [85,87], prostate cancer [86], neurological disorder [88], heart disease [89,90], parasitic infections [91,93], Alzheimer disease [92], influenza [94]. Except one paper that presents a bottom-up approach for the VLS-CVD preparation of Si NWs [90], in the other papers, Si NWs were prepared through a top-down approach in a CMOS technology.…”

“…Voltage shift in presence 0 ng/ml, 0.1 ng/mL, and 1 ng/mL of rabbit IgG, in 150 mM BTP (Bis-Tris propane). From [93].…”

“…A modification of a Si NW surface with a porous and biomolecule-permeable polymer layer (PEG) was used to increase the effective Debye screening length and then the sensitivity of detection [93]. The different scheme of the modified Si NW surface is presented in Figure 10.…”