SPR biosensors have been extensively used for investigating protein-protein interactions. However, in conventional surface plasmon resonance (SPR) biosensors, detection is limited by the ...Brownian-motion-governed diffusion process of sample molecules in the sensor chip, which makes it challenging to detect biomolecule interactions at ultra-low concentrations. Here, we propose a highly sensitive SPR imaging biosensor which exploits the coffee ring effect (CRE) for in situ enrichment of molecules on the sensing surface. In addition, we designed a wavelength modulation system utilizing two LEDs to reduce the system cost and enhance the detection speed. Furthermore, a detection limit of 213 fM is achieved, which amounts to an approximately 365 times improvement compared to traditional SPR biosensors. With further development, we believe that this SPR imaging system with high sensitivity, less sample consumption, and faster detection speed can be readily applied to ultra-low-concentration molecular detection and interaction analysis.
Visual perception plays a crucial role in foraging, avoiding predators, mate selection, and communication. The regulation of color vision is largely dependent on opsin, which is the first step in the ...formation of the visual transduction cascade in photoreceptor cells. Short-wave-sensitive 1 (sws1) is a visual pigment that mediates short-wavelength light transduction in vertebrates. The depletion of sws1 resulted in increased M-opsin in mice. However, there is still no report on the visual function of sws1 in teleost fish. Here, we constructed the sws1 knockout medaka using CRISPR/Cas9 technology. The 6 dph (days post-hatching) medaka sws1−/− larvae exhibited significantly decreased food intake and total length at the first feeding stage, and the mRNA levels of orexigenic genes (npy and agrp) were significantly upregulated after feeding. The swimming speed was significantly reduced during the period of dark-light transition stimulation in the sws1-mutant larvae. Histological analysis showed that the thickness of the lens was reduced, whereas the thickness of the ganglion cell layer (GCL) was significantly increased in sws1−/− medaka larvae. Additionally, the deletion of sws1 decreased the mRNA levels of genes involved in phototransduction (gnb3b, grk7a, grk7b, and pde6c). We also observed increased retinal cell apoptosis and oxidative stress in sws1 knockout medaka larvae. Collectively, these results suggest that sws1 deficiency in medaka larvae may impair visual function and cause retinal cell apoptosis, which is associated with the downregulation of photoconduction expression and oxidative stress.
We have demonstrated a high-average-power,high-repetition-rate optical terahertz（THz）source based on difference frequency generation（DFG）in the GaSe crystal by using a near-degenerate 2μm intracavity ...KTP optical parametric oscillator as the pump source.The power of the 2μm dual-wavelength laser was up to 12.33 W with continuous tuning ranges of 1988.0–2196.2 nm/2278.4–2065.6 nm for two waves.Different GaSe cystal lengths have been experimentally investigated for the DFG THz source in order to optimize the THz output power,which was in good agreement with the theoretical analysis.Based on an 8 mm long GaSe crystal,the THz wave was continuously tuned from 0.21 to 3 THz.The maximum THz average power of 1.66μW was obtained at repetition rate of 10 kHz under 1.48 THz.The single pulse energy amounted to 166 pJ and the conversion efficiency from 2 μm laser to THz output was 1.68×10-6.The signal-to-noise ratio of the detected THz voltage was 23 dB.The acceptance angle of DFG in the GaSe crystal was measured to be 0.16°.
A scheme for monochromatic terahertz (THz) generation via cascading enhanced Cherenkov-type difference frequency generation (DFG) in a sandwich-like waveguide is proposed. The novel scheme has the ...potential to overcome the quantum-defect limit and to provide an efficient output coupling. This process is elucidated by developing a coupled-mode theory and taking into account the pump depletion, waveguide mode properties, and THz output coupling. The effect of cascading enhancement is analyzed by comparing with non-cascaded DFG situation. It is predicted that THz power can be boosted by nearly 8-fold with a 400 MW/cm 2 pump in a 40-mm-long Si-LiNbO 3 -Si waveguide.
miRNAs are small non-coding RNA molecules which serve as promising biomarkers due to their important roles in the development and progression of various cancer types. The detection of miRNAs is of ...vital importance to the early-stage diagnostics and prognostics of multiple diseases. However, traditional detection strategies have faced some challenges owing to the intrinsic characteristics of miRNAs including small size, short sequence length, low concentration level and high sequence homology in complex real samples. To overcome these challenges, we proposed a MXene-enhanced plasmonic biosensor for real-time and label-free detection of miRNA. By utilizing MXene nanomaterial which possesses unique characteristics including large surface area and strong carrier confinement abilities, we tuned the absorption of our plasmonic sensing substrate to reach a “zero-reflection” state and induced an extremely sharp phase change at the resonance angle. Combined with the sensing mechanism based on phase-induced lateral displacement measurement, this MXene-enhanced plasmonic biosensor can achieve a much superior sensing performance compared to traditional SPR devices. Based on this biosensing scheme, the ultrasensitive detection of target miRNA with a detection limit down to 10 fM has been successfully demonstrated. More importantly, single-base mismatched miRNA can be easily distinguished from the target miRNA according to the sensing signal. Furthermore, our plasmonic biosensor is capable of detecting miRNA in complex media such as 100 % human serum samples without compromising the detection sensitivity. This MXene-enhanced plasmonic sensing scheme has the ability of detecting miRNAs with extremely low concentration levels in complex surrounding media without the need of introducing extra labels or amplification tags, which holds great potential in various biological applications and clinical diagnostics.
A tunable and compact mid-infrared optical parametric oscillator (OPO) based on BaGa4Se7 (BGSe) crystal with a repetition rate up to 250 Hz was demonstrated. A high energy and more approachable ...side-pumped Q-switched Nd:YAG laser was employed as the pump for the BGSe OPO. Due to the pump double-pass single-resonant oscillator (DP-SRO) configuration, the maximum average power of 250 mW and the maximum pulse energy of 1.28 mJ at 4.06 μm was achieved with the repetition rate of 250 Hz and 100 Hz, respectively. The tunable mid-infrared output from 3.42–4.73 μm was obtained. The influence of repetition rate and cavity length was studied and the thermal effect was analyzed.
With the unique advantages of mineral TCMs gradually emerging in clinical treatment, health care, and precaution, it has played an important role in the international medical market. Commonly, ...mineral TCMs with similar appearance and different processing methods have different effects, but they are easy to be confused in preparation, storage, transportation, and other links, which affects the use and causes related problems. In this paper, six kinds of easily confused mineral TCMs, including coral skeleton, ophicalcitum, calamine, matrii sulfas exsiccatus, gypsum, and alumen, are rapidly characterized using Raman spectroscopy, which can be distinguished with different Raman peaks at 0–300 cm−1 due to the different lattice structure. The THz spectra of these mineral TCMs show that different mineral TCMs have different THz absorption coefficients at 0.3–2.0 THz. Furthermore, compared with the ineffectiveness of the Raman spectrum for differentiating mineral TCMs prepared with disparate processing methods, the terahertz absorption spectrum plays an active role in making up the limitation of low-wavenumber Raman spectroscopy. The combination of low-wavenumber Raman and THz spectroscopy provides a simple and feasible scheme for the identification of mineral TCMs, which could play an important role in the quality control of mineral TCMs.
Exosomes have shown great potential in serving as a cancer biomarker over these years since they carry crucial information of their parent cells. Therefore, detection of exosomes is of vital ...importance to the early-stage diagnostics of multiple major diseases. In this paper, we have proposed a real-time and label-free sensing technique based on 2D Ge 2 Sb 2 Te 5 (GST) nanomaterial enhanced plasmonic substrate. We have achieved a detection limit down to 10 4 exosomes/mL based on Goos-Hänchen (GH) shift measurement, which is more than two orders of magnitude superior to conventional SPR sensing techniques. Moreover, the detection of unpurified exosomes directly in cell culture supernatant (CCS) has been successfully demonstrated with a significant experimental GH shift signal of more than 120 μm been detected. Multiple control experiments using exosome-free solutions and control antibody coated substrates have also been performed, which validates the specificity of our device. The proposed plasmonic sensing scheme with enhanced sensing performance has the capability of detecting exosomes at low concentration levels. It also possesses the ability of direct detection of exosomes in CCS, which offers a convenient and efficient platform for exosome detection and analysis. We envision that this technique can serve as a promising tool in early-stage clinical diagnostics and treatment.
► Ultrahigh sensitive terahertz detectors based on asymmetric dual-grating-gate HEMT. ► A record responsivity of 2.2kV/W at 1THz with a superior low noise equivalent power of 15pW/√ãHz. ► Strong THz ...photocurrent is first generated by the nonlinearity of the plasmon modes. ► The THz photovoltaic response is read out at high-impedance parts of 2D channel. ► Asymmetry of the cavity boundaries enhances the responsivity by more than two orders of magnitude.
We report on ultrahigh sensitive, broadband terahertz (THz) detectors based on asymmetric dual-grating-gate (A-DGG) high electron mobility transistors, demonstrating a record responsivity of 2.2kV/W at 1THz with a superior low noise equivalent power of 15pW/√Hz using InGaAs/InAlAs/InP material systems. When THz radiation is absorbed strong THz photocurrent is first generated by the nonlinearity of the plasmon modes resonantly excited in undepleted portions of the 2D electron channel under the high-biased sub-grating of the A-DGG (as a quadratic nature of the product of local carrier density and velocity perturbations), then the THz photovoltaic response is read out at high-impedance parts of 2D channel under the other sub-grating biased at the level close to the threshold. Extraordinary enhancement by more than two orders of magnitude of the responsivity is verified with respect to that for a symmetric DGG structure.
Psychoactive substances are a class of chemical substances which could cause public health threats. Cognitive disorders are a category of mental health disorders that primarily affect cognitive ...abilities. Tau protein could maintain neuronal cytoskeleton stabilization. Post-translational modification of tau, especially phosphorylation, is an important way to regulate the structure and function of tau and phosphorylated tau is closely related to cognitive function. Lots of studies have reported the phenomenon that psychoactive substances can cause cognitive function impairment. We reviewed recent related studies and discussed them by drug classification. We mainly focused on cognitive disorders caused by acute or chronic exposure of each drugs, animal experiments and the mechanisms associated with tau phosphorylation, then compared the similarities and differences among them, trying to find out the common rules. The results suggested that tau phosphorylation is involved in psychoactive substance-induced cognitive disorder and different psychoactive substances may act by affecting amount or activity of different kinases and phosphatases in the metabolic pathway of tau. We demonstrated that tau protein is a potential target for psychoactive substances induced cognitive disorder treatments.
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