Fluorescence Probe Based on Hybrid Mesoporous Silica/Quantum Dot/Molecularly Imprinted Polymer for Detection of Tetracycline

A newly designed fluorescence probe made from a hybrid quantum dot/mesoporous silica/molecularly imprinted polymer (QD/MS/MIP) was successfully created, and the probe was used for the detection of tetracycline (TC) in serum sample. QD/MS/MIP was characterized by transmission electron microscope, Fourier transform infrared spectroscopy, UV spectroscopy, X-ray powder diffraction, nitrogen adsorption–desorption experiment and fluorescence spectroscopy. Tetracycline, which is a type of broad-spectrum antibiotic, was selected as the template. The monomer and the template were combined by covalent bonds. After the template was removed to form a binding site, a hydrogen bonding interaction formed between the hole and the target molecule. Moreover, when rebinding TC, a new complex was produced between the amino group of QD/MS/MIP and the hydroxyl group of TC. After that, the energy of the QDs could transfer to the complex, which explains the fluorescence quenching phenomenon. The fluorescent intensity of QD/MS/MIP decreased in 10 min, and an excellent linearity from 50 to 1000 ng mL^–1 was correspondingly obtained. This composite material has a high selectivity with an imprinting factor of 6.71. In addition, the confirmed probe strategy was successfully applied to serum sample analyses, and the recoveries were 90.2%–97.2% with relative standard deviations of 2.2%–5.7%. This current work offers a novel and suitable method to synthesize QD/MS/MIP with a highly selective recognition ability. This composite material will be valuable for use in fluorescence probe applications

Fluorescence Probe Based on an Amino-Functionalized Fluorescent Magnetic Nanocomposite for Detection of Folic Acid in Serum

A new fluorescence probe constructed with a multifunctional nanocomposite, Fe₃O₄–ZnS:Mn²⁺/SiO₂–NH₂, was successfully synthesized and then used to detect folic acid in real serum samples. The nanocomposite was characterized by fluorescence spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray powder diffraction, and physical property measurement system. With the addition of analyte, the Fe₃O₄–ZnS:Mn²⁺/SiO₂–NH₂ composite and folic acid formed a new complex because cross-linking of the amino and carboxyl groups participated in the condensation reaction. Then, the energy of quantum dots was transferred to the complex and led to quenching of the fluorescence. Moreover, the fluorescence intensity decreased significantly as the concentration of folic acid increased, and the fluorescence quenching ratio <i>F</i>₀/<i>F</i> was related to the folic acid concentration in the range from 0.1 to 5 μg mL^–1. This method was used for detecting folic acid in real serum samples and gave recoveries in the range of 89.0%–96.0%, with relative standard deviations of 1.2%–3.9%. The detection limit was 9.6 ng mL^–1 (S/N = 3). These satisfactory and simple results showed the great potential of this fluorescence probe in the field of pharmaceutical analysis

Ag_{2–3<i>x</i>}Bi<i>_x</i>S Quantum Dots as Single-Component Theranostic Agents for Second Near-Infrared Fluorescence Imaging-Guided Photothermal Therapy

Silver sulfide (Ag2S) nanomaterials are being researched increasingly because of their multifunctional potential in the second near-infrared (NIR-II) region (1000–1500 nm). Here, we report Ag2–3xBixS quantum dots (Ag2–3xBixS QDs) as single-component theranostic nanomaterials for NIR-II fluorescence imaging and synchronous photothermal therapy. Bismuth doping in Ag2S QDs leads to a fluorescence red shift to the NIR-II region and simultaneously enhances the photothermal conversion efficiency to 58.9%, which can be ascribed to the altered band gap introduced by bismuth doping. This Ag2S-based NIR-II theranostic agent can be synthesized in a controlled manner by an albumin biomineralization method under mild conditions. The encapsulation of the biomacromolecular albumin endowed Ag2–3xBixS QDs with greatly strengthened biocompatibility and stability. The survival rate of cancer cells was only 13% after irradiation with an 808 nm laser at a density of 1.2 W cm–2 for 10 min. Meanwhile, in vivo experiments have confirmed the desirable NIR-II fluorescence imaging capability of Ag2–3xBixS QDs. Thus, this study provides a highly efficient single-component theranostic agent with great promise for application in the field of precision theranostics

Biocompatible Fluorescent Biosensor Reveals the Level and Distribution of Indole-3-Acetic Acid Signals in Plants

To fully understand the function of the phytohormone indole-3-acetic acid (IAA) in regulating plant growth and development, we need to monitor their levels and distribution with high spatial and temporal resolution. In this work, an anthracene-based fluorescent biosensor for IAA was prepared using bovine serum albumin (BSA) as a bio-template. The single linear oxygen (1O2) specifically produced by IAA catalyzed with horseradish peroxidase (HRP) turns on the fluorescence of the probe, enabling specific trace sensing of IAA in the presence of multiple structural analogues. The presence of the bio-template BSA extends the biocompatibility of the probe, enabling visual monitoring of the level and distribution signal of endogenous IAA of plants in the field of bioimaging. In addition, the strategy has shown potential for application in portable paper-based sensors and in vivo fluorescent flower culture. This work provides a technical and theoretical basis for exploring the growth regulatory mechanisms of IAA in plants at the molecular level

Additional file 3 of Perfusion CT detects alterations in local cerebral flow of glioma related to IDH, MGMT and TERT status

Additional file 3: Supplementary Fig. 2. Comparisons of OS in the four molecular groups divided by the combined MGMT/TERT status in GBM

Additional file 1 of Perfusion CT detects alterations in local cerebral flow of glioma related to IDH, MGMT and TERT status

Additional file 1: Supplementary Table 1. Patient background and molecular status. Supplementary Table 2. Patient background of four molecular groups divided by the combined IDH/TERT status in WHO II-IV diffuse glioma. Supplementary Table 3. Comparisons of perfusion parameters in the four molecular groups divided by the combined MGMT/TERT status in GBM

Additional file 2 of Perfusion CT detects alterations in local cerebral flow of glioma related to IDH, MGMT and TERT status

Additional file 2: Supplementary Fig. 1. Comparisons of PFS in the four molecular groups divided by the combined MGMT/TERT status in GBM

DataSheet1_Terahertz time-domain attenuated total reflection spectroscopy integrated with a microfluidic chip.pdf

The integration of a microfluidic chip into terahertz time-domain attenuated total reflection (THz TD-ATR) spectroscopy is highly demanded for the accurate measurement of aqueous samples. Hitherto, however little work has been reported on this regard. Here, we demonstrate a strategy of fabricating a polydimethylsiloxane microfluidic chip (M-chip) suitable for the measurement of aqueous samples, and investigate the effects of its configuration, particularly the cavity depth of the M-chip on THz spectra. By measuring pure water, we find that the Fresnel formulae of two-interface model should be applied to analyze the THz spectral data when the depth is smaller than 210 μm, but the Fresnel formula of one-interface model can be applied when the depth is no less than 210 μm. We further validate this by measuring physiological solution and protein solution. This work can help promote the application of THz TD-ATR spectroscopy in the study of aqueous biological samples.</p

Mo Single-Atom Nanozyme Anchored to the 2D N‑Doped Carbon Film: Catalytic Mechanism, Visual Monitoring of Choline, and Evaluation of Intracellular ROS Generation

Single-atom nanozymes (SANs) have attracted great attention in constructing devices for instant biosensing due to their excellent stability and atom utilization. Here, Mo atoms were immobilized in 2D nitrogen-doped carbon films by cascade-anchored one-pot pyrolysis to obtain Mo single-atom nanozyme (Mo-SAN) with high atomic loading (4.79 wt %) and peroxidase-like activity. The coordination environment and enzyme-like activity mechanism of Mo-SAN were studied by combining synchrotron radiation and density functional theory. The strong oxophilicity of single-atom Mo makes the catalytic center more capable of transferring electrons to free radicals to selectively generate •OH in the presence of H2O2. Choline oxidase and Mo-SAN were used as signal opening unit and signal amplification unit, respectively. Combining the portability and visualization functions of smartphone and test strips, a paper-based visual sensing platform was constructed, which can accurately identify choline at a concentration of 0.5–35 μM with a limit of detection as low as 0.12 μM. The recovery of human serum samples was 96.4–102.2%, with an error of less than 5%. Furthermore, the potential of Mo-SAN to efficiently generate toxic •OH in tumor cells was intuitively confirmed. This work provides a technical and theoretical basis for designing highly active SANs and detecting neurological markers

Photoactive Control of Surface-Enhanced Raman Scattering with Reduced Graphene Oxide in Gas Atmosphere

Surface-enhanced Raman scattering (SERS) is an ultrahigh sensitive detection technique for a variety of research fields. Both electromagnetic and chemical enhancement mechanisms are generally considered to contribute simultaneously to SERS signals. However, it is difficult to actively control the enhancement of SERS signals after the substrate is fabricated, since tuning one or both of the aforementioned enhancement mechanisms remains an experimental challenge. Here, we propose a method for actively implementing the photoinduced modulation of SERS signals, which is that under UV irradiation, the Fermi level of graphene can be dynamically modulated due to the adsorption and desorption of gas molecules. The method is validated in gas atmospheres of O2, CO2, N2, and air and also demonstrate its generality by different analytes. In addition, the method was successfully applied to the trace detection of pesticides on fruit peels in air environment, which show its practical implications in sensing