Toward the Ultimate Limit of Analyte Detection, in Graphene-Based Field-Effect Transistors.

The ultimate sensitivity of field-effect-transistor (FET)-based devices for ionic species detection is of great interest, given that such devices are capable of monitoring single-electron-level modulations. It is shown here, from both theoretical and experimental perspectives, that for such ultimate limits to be approached the thermodynamic as well as kinetic characteristics of the (FET surface)-(linker)-(ion-receptor) ensemble must be considered. The sensitivity was probed in terms of optimal packing of the ensemble, through a minimal charge state/capacitance point of view and atomic force microscopy. Through the fine-tuning of the linker and receptor interaction with the sensing surface, a record limit of detection as well as specificity in the femtomolar range, orders of magnitude better than previously obtained and in excellent accord with prediction, was observed.

A regenerable electrochemical sensor for electro-inactive cyclovirobuxine D detection in biological samples.

Based on the pKa determination of cyclovirobuxine D (CVB-D) using the method of potentiometry, we predicted the ionization state of CVB-D at physiological pH. Thus, by taking advantage of the ionization state and consequent non-covalent interactions between protonated CVB-D and deprotonated polymerized bromothymol blue (poly-BTB) under physiological conditions, we developed a simple and reusable electrochemical sensor that contains a poly-BTB/SWNT-modified electrode for electro-inactive CVB-D detection in biological fluids using poly-BTB as both the recognition unit and the electrochemical probe. Upon being immersed in the solution of CVB-D, the poly BTB-based electrode shows a current decrease due to the interaction-driven binding of CVB-D on the electrode surface. The current decrease in the electrochemical sensor toward CVB-D concentration shows a linear relationship in the dynamic ranges of 0.01-1 µM and 1-50 µM with a detection limit of 1.65 nM based on 3σ. The sensor can be easily regenerated through the removal of the binding of CVB-D from the electrode surface by highly negatively charged heparin, and it presents high repeatability with an RSD of less than 4.0% for seven measurements. In animal experiments, the electrochemical sensor was selective and sensitive for CVB-D determination in plasma and liver homogenates. The electrochemical sensor is readily accessible, robust, and cost-effective and holds good promise for more applications in biological and clinical fields associated with CVB-D using less technically demanding and simple operating procedures.

Enhanced graphene surface plasmonics through incorporation into metallic nanostructures.

A methodology for enhancing the surface plasmon polariton (SPP) resonance associated with graphene, through nanoscale metal-dielectric-metal (MDM) gaps, is proposed. The modulation of the resonances, in the range of 0.7 µm to 1 µm was done through tuning the carrier density in graphene and has been shown to be of potential utility for surface analyte sensing. It was shown, from finite element simulations in the frequency domain, that the related hybrid SPP modes could be clearly delineated in far field spectroscopy.

Rapid self-test of unprocessed viruses of SARS-CoV-2 and its variants in saliva by portable wireless graphene biosensor.

We have developed a DNA aptamer-conjugated graphene field-effect transistor (GFET) biosensor platform to detect receptor-binding domain (RBD), nucleocapsid (N), and spike (S) proteins, as well as viral particles of original Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) coronavirus and its variants in saliva samples. The GFET biosensor is a label-free, rapid (≤20 min), ultrasensitive handheld wireless readout device. The limit of detection (LoD) and the limit of quantitation (LoQ) of the sensor are 1.28 and 3.89 plaque-forming units (PFU)/mL for S protein and 1.45 and 4.39 PFU/mL for N protein, respectively. Cognate spike proteins of major variants of concern (N501Y, D614G, Y453F, Omicron-B1.1.529) showed sensor response ≥40 mV from the control (aptamer alone) for fM to nM concentration range. The sensor response was significantly lower for viral particles and cognate proteins of Middle East Respiratory Syndrome (MERS) compared to SARS-CoV-2, indicating the specificity of the diagnostic platform for SARS-CoV-2 vs. MERS viral proteins. During the early phase of the pandemic, the GFET sensor response agreed with RT-PCR data for oral human samples, as determined by the negative percent agreement (NPA) and positive percent agreement (PPA). During the recent Delta/Omicron wave, the GFET sensor also reliably distinguished positive and negative clinical saliva samples. Although the sensitivity is lower during the later pandemic phase, the GFET-defined positivity rate is in statistically close alignment with the epidemiological population-scale data. Thus, the aptamer-based GFET biosensor has a high level of precision in clinically and epidemiologically significant SARS-CoV-2 variant detection. This universal pathogen-sensing platform is amenable for a broad range of public health applications and real-time environmental monitoring.

An indicator displacement assay-based optical chemosensor for heparin with a dual-readout and a reversible molecular logic gate operation based on the pyranine/methyl viologen.

We have reported an optical indicator displacement assay (IDA) for heparin with a UV-vis absorbance and fluorescence dual-readout based on pyranine/methyl viologen (MV2+). Upon introducing heparin, pyranine/MV2+ shows a clearly observable increase in UV-vis absorbance and a turn-on of the fluorescence signal. We have demonstrated that the ionic nature of buffers significantly affects the pyranine displacement and the zwitterionic HEPES was most suitable for heparin sensing. After careful screening of experimental conditions, the pyranine/MV2+-based optical chemosensor exhibits a fast, sensitive, and selective response toward heparin. It shows dynamic linear concentration of heparin in the ranges of 0.1-40 U·mL-1 and 0.01-20 U·mL-1 for the absorptive and fluorescent measurements, respectively, which both cover the clinically relevant levels of heparin. As with the animal experiments, the optical chemosensor has been demonstrated to be selective and effective for heparin level qualification in rat plasma. The chemosensor is readily accessible, cost-effective, and reliable, which holds a great promise for potential application on clinical and biological studies. Furthermore, this IDA system can serve as an IMPLICATION logic gate with a reversible and switchable logical manner.

Interaction and hybridization of orthogonal Fabry-Pérot like surface plasmon modes in metal-dielectric grating structures.

The interaction of specific surface plasmon modes in metal-dielectric-metal arrangements is investigated, motivated by their relevance to device-based configurations. The absorption spectra of the relevant nanostructures considering geometrical variation, such as the width and height of the metal or dielectric, are probed considering such interactions. Frequency domain simulations are used to study related multiple surface plasmon polariton resonance modes. It is indicated that the resonant energy level interaction due to the coupling between modes in a horizontal dielectric layer and those in a vertical groove can be engineered and understood in terms of energy level hybridization.

Complete mitochondrial genome sequence and mutations of the prostate cancer model inbred Sprague-Dawley strain.

In the present work we undertook the complete mitochondrial genome sequencing of a important prostate cancer model inbred Sprague-Dawley strain for the first time. The total length of the mitogenome was 16,308 bp. It harbored 13 protein-coding genes, two ribosomal RNA genes, 22 transfer RNA genes and one non-coding control region (D-loop region). The mutation events were also reported.

[Diagnosis and differential diagnosis value of ultrasound in epididymal mass].

OBJECTIVE: To elevate the diagnosis and differential diagnosis levels of epididymal mass by sonography. METHODS: This was a retrospective study of 179 cases of epididymal mass treated by surgery in our hospital between 1990 and 2005. The analysis was focused on pathological and sonographic features. RESULTS: 179 patients with mean age of 51.4 +/- 14.7 were enrolled. The epididymal mass was classified into four groups: epididymal cyst (n = 98), nonspecific epididymitis (n = 27), tuberculous epididymitis (n = 33) , and epididymal tumor (n = 21). Epididymal cyst could be easily diagnosed by ultrasound, the diagnostic rate was 93.8%, but nonspecific epididymitis and tuberculous epididymitis were hard to differentiate, complicating with multiple organs lesions may distinguish tuberculous from nonspecific epididymitis. Tuberculous epididymitis could be easily diagnosed when cold abscess, calcification and sinus tract emerged. The majority epididymal tumors were benign, and malignant cases were rarely seen. Patient's history, physical examination and sonographic features were all essential to make a right diagnosis. CONCLUSION: Ultrasound features may be helpful to the differential diagnosis of epididymal mass and ultrasound should be the first choice of image detection in epididymal lesions.

[Ultrasound guided percutaneous puncture and sclerotherapy with alcohol for peripelvic cysts].

OBJECTIVE: To summarize the experience of ultrasound guided percutaneous aspiration and sclerotherapy for peripelvic cysts and investigate the clinical effect. METHODS: A total of 169 cases of peripelvic cyst patients were evaluated, of whom 36 cases (21.3%) had hydronephrosis secondary to peripelvic cysts, 8 cases (4.7%) had renal calculus. All patients underwent ultrasound and intravenous phelography (IVP) examination, 59 patients also had CT scan. Hydatid fluid was analyzed by amine test. Percutaneous aspiration was guided by ultrasound, 95% alcohol was used to sclerosis the peripelvic cysts when amine test was negative or positive but did not have communication with pelvis through opacification. Ultrasound were done at 1, 3, 6 months and every 1 year thereafter, follow-up period were 6 months to 5 years. RESULTS: One hundred and sixty-five peripelvic cysts (97.6%) were cured by once sclerotherapy, the diameter of another 4 cases (2.4%) diminished to less than 1.5 cm by once sclerotherapy. Thirty-six cases of hydronephrosis were all resolved after sclerotherapy. Eight cases had renal calculus, of whom 4 cases underwent extracorporeal shockwave lithotripsy, 2 cases underwent percutaneous nephrolithotomy, and 2 cases did not treat the stone. Five patients had gross hematuria after aspiration, but all diminished in 3-5 d. CONCLUSION: Ultrasound guided percutaneous aspiration and sclerotherapy for peripelvic cysts had the superiority of safety, effectiveness micro-invasion and low complication.