Influence of Surface Treatments on Urea Detection Using Si Electrolyte-Gated Transistors with Different Gate Electrodes.

We investigated the impact of surface treatments on Si-based electrolyte-gated transistors (EGTs) for detecting urea. Three types of EGTs were fabricated with distinct gate electrodes (Ag, Au, Pt) using a top-down method. These EGTs exhibited exceptional intrinsic electrical properties, including a low subthreshold swing of 80 mV/dec, a high on/off current ratio of 106, and negligible hysteresis. Three surface treatment methods ((3-amino-propyl) triethoxysilane (APTES) and glutaraldehyde (GA), 11-mercaptoundecanoic acid (11-MUA), 3-mercaptopropionic acid (3-MPA)) were individually applied to the EGTs with different gate electrodes (Ag, Au, Pt). Gold nanoparticle binding tests were performed to validate the surface functionalization. We compared their detection performance of urea and found that APTES and GA exhibited the most superior detection characteristics, followed by 11-MUA and 3-MPA, regardless of the gate metal. APTES and GA, with the highest pKa among the three surface treatment methods, did not compromise the activity of urease, making it the most suitable surface treatment method for urea sensing.

Sensing Characteristics of SARS-CoV-2 Spike Protein Using Aptamer-Functionalized Si-Based Electrolyte-Gated Field-Effect Transistor (EGT).

The sensing responses of SARS-CoV-2 spike protein using top-down-fabricated Si-based electrolyte-gated transistors (EGTs) have been investigated. An aptamer was employed as a receptor for the SARS-CoV-2 spike protein. The EGT demonstrated excellent intrinsic characteristics and higher sensitivity in the subthreshold regime compared to the linear regime. The limit of detection (LOD) was achieved as low as 0.94 pg/mL and 20 pg/mL for the current and voltage sensitivity, respectively. To analyze the sensing responses of EGT in detecting the aptamer-SARS-CoV-2 spike protein conjugate, a lumped-capacitive model with the presence of an effective dipole potential and an effective capacitance of the functionalized layer component was employed. The aptamer-functionalized EGT showed high sensitivity even in 10 mM phosphate-buffered saline (PBS) solution. These results suggest that Si-based EGTs are a highly promising method for detecting SARS-CoV-2 spike proteins.

Sybodies as Novel Bioreceptors toward Field-Effect Transistor-Based Detection of SARS-CoV-2 Antigens.

The SARS-CoV-2 pandemic has increased the demand for low-cost, portable, and rapid biosensors, driving huge research efforts toward new nanomaterial-based approaches with high sensitivity. Many of them employ antibodies as bioreceptors, which have a costly development process that requires animal facilities. Recently, sybodies emerged as a new alternative class of synthetic binders and receptors with high antigen binding efficiency, improved chemical stability, and lower production costs via animal-free methods. Their smaller size is an important asset to consider in combination with ultrasensitive field-effect transistors (FETs) as transducers, which respond more intensely when biorecognition occurs near their surface. This work demonstrates the immobilization of sybodies against the spike protein of the virus on silicon surfaces, which are often integral parts of the semiconducting channel of FETs. Immobilized sybodies maintain the capability to capture antigens, even at low concentrations in the femtomolar range, as observed by fluorescence microscopy. Finally, the first proof of concept of sybody-modified FET sensing is provided using a nanoscopic silicon net as the sensitive area where the sybodies are immobilized. The future development of further sybodies against other biomarkers and their generalization in biosensors could be critical to decrease the cost of biodetection platforms in future pandemics.

Highly Sensitive Detection of Urea Using Si Electrolyte-Gated Transistor with Low Power Consumption.

We experimentally demonstrate Si-based electrolyte-gated transistors (EGTs) for detecting urea. The top-down-fabricated device exhibited excellent intrinsic characteristics, including a low subthreshold swing (SS) (~80 mV/dec) and a high on/off current ratio (~107). The sensitivity, which varied depending on the operation regime, was analyzed with the urea concentrations ranging from 0.1 to 316 mM. The current-related response could be enhanced by reducing the SS of the devices, whereas the voltage-related response remained relatively constant. The urea sensitivity in the subthreshold regime was as high as 1.9 dec/pUrea, four times higher than the reported value. The extracted power consumption of 0.3 nW was extremely low compared to other FET-type sensors.

An Ultrasensitive Silicon-Based Electrolyte-Gated Transistor for the Detection of Peanut Allergens.

The highly sensitive detection of peanut allergens (PAs) using silicon-based electrolyte-gated transistors (Si-EGTs) was demonstrated. The Si-EGT was made using a top-down technique. The fabricated Si-EGT showed excellent intrinsic electrical characteristics, including a low threshold voltage of 0.7 V, low subthreshold swing of <70 mV/dec, and low gate leakage of <10 pA. Surface functionalization and immobilization of antibodies were performed for the selective detection of PAs. The voltage-related sensitivity (SV) showed a constant behavior from the subthreshold regime to the linear regime. The current-related sensitivity (SI) was high in the subthreshold regime and then significantly decreased as the drain current increased. The limit of detection (LOD) was calculated to be as low as 25 pg/mL based on SI characteristics, which is the lowest value reported to date in the literature for various sensor methodologies. The Si-EGT showed selective detection of PA through a non-specific control test. These results confirm that Si-EGT is a high-sensitivity and low-power biosensor for PA detection.

Prophylactic endoscopic coagulation to prevent delayed post-EMR bleeding in the colorectum: a prospective randomized controlled trial (with videos).

BACKGROUND AND AIMS: Post-EMR bleeding (PEB) is the most common adverse event after EMR. However, there are no established endoscopic methods for the prevention of PEB. This study aimed to investigate whether prophylactic endoscopic coagulation (PEC) using coagulation probes reduces the incidence of overall delayed PEB. METHODS: We performed a randomized controlled study of patients undergoing EMR for large (≥10 mm) sessile lesions and laterally spreading tumors. Patients were randomized 1:1 to the EMR with coagulation group (n = 285) or EMR (control) group (n = 285). Immediate bleeding during colon EMR or clean-based ulcer after EMR was excluded. Clinically significant PEB was defined as bleeding requiring endoscopic hemostasis, hospitalization, or a decrease in the hemoglobin level >2 g/dL. RESULTS: A total of 569 patients were analyzed. The incidence of overall PEB was significantly lower in the EMR with coagulation group than in the control group (12.6% [36/285] vs 18.7% [53/284], P = .048). However, this was largely because of a reduction in minor bleeding. There was no difference in clinically significant PEB (1.8% [5/285] vs 3.2% [9/284], P = .276). Rectal location was a risk factor associated with overall PEB (odds ratio, 1.256; 95% confidence interval, 1.12-1.41; P < .001). CONCLUSIONS: Although this study found reduced PEB with prophylactic cautery of visible vessels, this was largely because of a reduction in minor bleeding with no benefit observed for clinically significant bleeding. Overall, PEB was more frequent with rectal lesions. (Clinical trial registration number: KCT0000779.).