Journal: Sensors (Basel, Switzerland)

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

doi: 10.3390/s21020650

Figure Lengend Snippet: Illustration of the detection of rabbit IgG by (1) Wab/APTES-SiNWFETs, (2) Fab/APTES-SiNWFETs, (3) Wab/PEG-SiNWFETs, and (4) Fab/PEG-SiNWFETs as well as their corresponding signal enhancement by R18 aptamer in this study. Both of the Wab/APTES-SiNWFETs (sample 1) and Fab/APTES-SiNWFETs (sample 2) were used to detect ( A ) rabbit IgG (blue Y shapes) at concentrations of 100 pg/mL and 1 ng/mL, before binding with ( B ) 3 μg/mL R18 aptamer (green curves) for signal enhancement. The Wab/PEG-SiNWFETs (sample 3) could only determine ( A ) rabbit IgG (blue Y shapes) at concentrations of 10 pg/mL, 100 pg/mL and 1 ng/mL, whereas the Fab/PEG-SiNWFETs (sample 4) could recognize ( A ) rabbit IgG (blue Y shapes) at concentrations of 1 pg/mL, 10 pg/mL, 100 pg/mL, and 1 ng/mL. Both of them were then also incubated in ( B ) 3 μg/mL R18 aptamer (green curves) for signal enhancement. All the biosensing experiments in this Figure were performed in 150 mM BTP.

Article Snippet: 3,3′,5,5′-Tetramethylbenzidine (TMB), acetone, and ethanol (99.9%) was ordered from Thermo Fisher Scientific, while the components of PEG-mSAMs (silane-PEG-NH 2 , 1K and silane-PEG-OH, 1K) were from Biochempeg Scientific Inc. All the antibodies, including rabbit immunoglobulin G (IgG), donkey anti-goat antibody conjugated with horseradish peroxide (HRP), goat anti-rabbit IgG antibody (Wab), and its Fab, were supplied by Abcam plc. (UK), whereas R18 aptamer specifying rabbit IgG (74-mer RNA sequence: 5′-GGGAG AAUUC CGACC AGAAG UUCGA UACGC CGUGG GGUGA CGUUG GCUAC CCUUU CCUCU CUCCU CCUUC UUCU-3′ [ ]) was synthesized by MDBio, Inc.

Techniques: Binding Assay, Incubation

Journal: Sensors (Basel, Switzerland)

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

doi: 10.3390/s21020650

Figure Lengend Snippet: ( A , B ) Representative samples to illustrate the method described in . ( A ) Electrical response of the Wab/APTES-SiNWFETs was initially recorded in 150 mM BTP and plotted as the first curve (the black curve). This immunosensor was then employed to detect rabbit IgG at 1 ng/mL, followed by incubation with 3 μg/mL R18 (IgG and R18 were diluted in 150 mM BTP). Finally, its electrical response was measured again and plotted as the blue curve. The signal change generated by formation of the biocomplex (Wab-IgG-R18) was calculated from the formula ΔV = V d1 − V d0 (1), with V d1 as the gate voltage value at I d = 10 −9 A (LgI = −9) of the blue curve, whereas V d0 is the gate voltage value at I d = 10 −9 A (LgI = −9) of the black curve. ( B ) Electrical response of the Fab/APTES-SiNWFET was initially recorded in 150 mM BTP and plotted as the first curve (the black curve). This immunosensor was then employed to detect rabbit IgG at 1 ng/mL following by incubation with 3 μg/mL R18 (IgG and R18 were all diluted in 150 mM BTP). Finally, its electrical response was measured again and plotted as the blue curve. The signal change generated by formation of the biocomplex (Fab-IgG-R18) was calculated from the formula ΔV = V d1 − V d0 (1), with V d1 is the gate voltage value at I d = 10 −9 A (LgI = −9) of the blue curve, whereas V d0 is the gate voltage value at I d = 10 −9 A (LgI = −9) of the black curve. ( C ) Comparison of the signal amplified by R18 (mV) after determining rabbit IgG at different concentrations (0.1 ng/mL and 1 ng/mL) in 150 mM BTP by Wab/APTES-SiNWFETs (blue bars) and Fab/APTES-SiNWFETs (red bars). The voltage shift (mV) generated by IgG detection of APTES-SiNWFETs without probes (Wab nor Fab) (black bar), and by recognizing R18 without IgG (0 ng/mL) of Fab/APTES-SiNWFETs, was also calculated for analysis.

Article Snippet: 3,3′,5,5′-Tetramethylbenzidine (TMB), acetone, and ethanol (99.9%) was ordered from Thermo Fisher Scientific, while the components of PEG-mSAMs (silane-PEG-NH 2 , 1K and silane-PEG-OH, 1K) were from Biochempeg Scientific Inc. All the antibodies, including rabbit immunoglobulin G (IgG), donkey anti-goat antibody conjugated with horseradish peroxide (HRP), goat anti-rabbit IgG antibody (Wab), and its Fab, were supplied by Abcam plc. (UK), whereas R18 aptamer specifying rabbit IgG (74-mer RNA sequence: 5′-GGGAG AAUUC CGACC AGAAG UUCGA UACGC CGUGG GGUGA CGUUG GCUAC CCUUU CCUCU CUCCU CCUUC UUCU-3′ [ ]) was synthesized by MDBio, Inc.

Techniques: Incubation, Generated, Comparison, Amplification

Journal: Sensors (Basel, Switzerland)

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

doi: 10.3390/s21020650

Figure Lengend Snippet: ( A ) Comparison of the signal amplified by R18 (mV) after sensing rabbit IgG at various levels in 150 mM BTP by Wab/PEG-SiNWFETs (blue bars) and Fab/APTES-SiNWFETs (red bars). ( B ) Plot of the voltage shift by R18 versus logarithmic concentrations of rabbit IgG and two respective calibration lines obtained by Wab/PEG-SiNWFETs (blue line) and Fab/APTES-SiNWFETs (red line).

Article Snippet: 3,3′,5,5′-Tetramethylbenzidine (TMB), acetone, and ethanol (99.9%) was ordered from Thermo Fisher Scientific, while the components of PEG-mSAMs (silane-PEG-NH 2 , 1K and silane-PEG-OH, 1K) were from Biochempeg Scientific Inc. All the antibodies, including rabbit immunoglobulin G (IgG), donkey anti-goat antibody conjugated with horseradish peroxide (HRP), goat anti-rabbit IgG antibody (Wab), and its Fab, were supplied by Abcam plc. (UK), whereas R18 aptamer specifying rabbit IgG (74-mer RNA sequence: 5′-GGGAG AAUUC CGACC AGAAG UUCGA UACGC CGUGG GGUGA CGUUG GCUAC CCUUU CCUCU CUCCU CCUUC UUCU-3′ [ ]) was synthesized by MDBio, Inc.

Techniques: Comparison, Amplification

Journal: ACS Omega

Article Title: Free Solution Assay Signal Modulation in Variable-Stem-Length Hairpin Aptamers

doi: 10.1021/acsomega.9b04341

Figure Lengend Snippet: Tenofovir hairpin aptamers. Five hairpin aptamers with varying stem lengths bind to tenofovir with varying FSA signal magnitudes (A) and K D (B) despite identical target binding. (A) Error bars represent the standard deviation of three replicate trials. The dotted line is a fitted slope = −7.5 ± 0.9 mrad/base pair, R 2 = 0.96. (B) K D fitted to single-site saturation isotherm (full data in the Supporting Information Figure S1 ). Error bars represent the standard error of the fitted K D . Thermodynamic calculations show a decrease in the Gibbs free energy (C) and an increase in melting temperature (D) correlating with the increasing stem length.

Article Snippet: Single-stranded DNA aptamers were selected by Base Pair Biotechnologies (Pearland, TX) using a modified SELEX process.

Techniques: Binding Assay, Standard Deviation