- 标题
- 摘要
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- 实验方案
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Tannic acid-derivatized graphitic carbon nitride quantum dots as an “on-off-on” fluorescent nanoprobe for ascorbic acid via copper(II) mediation
摘要： A microwave-assisted hydrothermal route was employed to prepare fluorescent tannic acid (TA)-derivatized graphitic carbon nitride quantum dots. The resulting dots display blue fluorescence (best measured at excitation/emission wavelengths of 350/452 nm) with a quantum yield as high as ~44%. The incorporated TA imparts a fluorescence switching behavior in that very low concentrations of Cu(II) can quench the fluorescence, while (AA) can restore it. It is presumed that AA causes Cu(II) to be transformed to Cu(I). Based on these findings, a fluorometric method was designed for AA detection. The probe allows AA to be detected with a 50 pM limit of detection and a linear analytical range that extends from 0.1 to 200 nM of AA. Real and spiked samples were successfully assayed by the probe to demonstrate its analytical applicability.
关键词： Fluorescence recovery,Metal ions,Graphitic nanosheets,Biomolecules,Polyphenolic compounds,Optical probe,Quantum dots
更新于2025-10-22 19:40:53
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Microfluidics Integrated Lithography-Free Nanophotonic Biosensor for the Detection of Small Molecules
摘要： Currently, labeling techniques are mostly used to study the binding kinetics of small molecules and their detection (molecular weights <500 Daltons) at low analyte concentrations. However, the fluorescent tags used in this method for conjugation may modify or prevent the functionality of the targeted molecules. Although label-free techniques provide more accurate quantitative and kinetic measurements by monitoring the binding of analytes in their usual forms, the monitoring of small molecule binding at lower concentrations is still impossible using conventional refractometric sensing devices. Here, a label-free and cost-effective technique is demonstrated for the detection of ultralow molecular weight biomolecules such as biotin (244 Daltons) at very low concentrations. This extreme sensitivity is realized by utilizing the phase singularity feature of lithography-free nanophotonic cavities. The proposed four-layered metal-dielectric-dielectric-metal asymmetric Fabry–Perot cavity exhibits point-of-darkness and phase singularity at the Brewster angle. Since the singular phase behavior depends on the topology of the cavity surface, it is very challenging to realize singular phase in reflection mode for a microfluidics integrated nanophotonic cavity. To overcome this issue, a specially designed polymethylmethacrylate microfluidic channel is integrated with the cavity.
关键词： flat-optics,small biomolecules,Fabry–Perot cavities,lithography-free,label-free optical biosensors,biosensors
更新于2025-09-23 15:23:52
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[Methods in Molecular Biology] Microfluidic Electrophoresis Volume 1906 (Methods and Protocols) || Paper-Based Electrophoresis Microchip as a Powerful Tool for Bioanalytical Applications
摘要： This chapter describes the development of paper-based microchip electrophoresis (pME) devices for the separation of clinically relevant compounds. pME were fabricated by laser cut and thermal lamination process using polyester pouches. In addition, hand-drawn pencil electrodes were integrated to the device to perform capacitively coupled contactless conductivity detection (C4D). Finished device costs less than US$ 0.10 and did not require either sophisticated instrumentation or clean room facilities. Furthermore, pME is lightweight, easy to handle, ?exible, and robust. pME-C4D device revealed an excellent capacity to separate BSA and creatinine in less than 150 s with baseline resolution. The device proposed in this chapter has proven to be a good alternative as a platform for the diagnosis of diseases from renal disorders such as diabetes mellitus and heart disease.
关键词： Biomolecules,Paper electrophoresis,Kidney failure,Pencil electrodes,Bovine serum albumin,Creatinine,Clinical diagnosis,Contactless conductivity detection
更新于2025-09-23 15:21:01
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Facile Preparation of MnO <sub/>2</sub> Quantum Dots with Enhanced Fluorescence via the Micro-environment Engineering with the Assistance of Some Reductive Biomolecules
摘要： MnO2 nanomaterials have been aroused wide attention because of their nano-enzyme activity, redox property, good biocompatibility and therapy-related activities. However, not any report about self-luminescent MnO2 materials are concerned to date, which greatly hampered their further development in various fields. In this paper, luminescent MnO2 quantum dots (MnO2 QDs) has been firstly prepared via a facile one-step ultrasonic method. With the assistant of bovine serum albumin (BSA) or cysteine (Cys), the synthesized MnO2 QDs (BSA-MnO2 QDs or Cys-MnO2 QDs) display strongly enhanced fluorescence (FL). The prepared BSA-MnO2 QDs with the particles size of about 1-2 nm show the maximum excitation and emission peaks at 320 and 410 nm with excellent salt stability, anti-photo bleaching ability and time stability. It is confirmed that BSA play the dual function as the exfoliating agent to promote the exfoliation of bulk MnO2 nanosheets and as the capping agent to provide a friendly micro-environment for MnO2 QDs. Ag ions can destroy the micro-environment of BSA-MnO2 QDs owing to the in-situ formation of Ag nanoparticles (Ag NPs) mediated by the BSA on the surface of the QDs. Then these Ag NPs can quench the FL intensity of the QDs by fluorescence resonance energy transfer. However, the FL strength of BSA-MnO2 QDs is recovered after adding H2O2 and NaHS since they may react with Ag NPs to produce Ag+ and Ag2S, which further confirmed the role of BSA. This work not only opens a facile and universal avenue to synthesize luminescent MnO2 QDs with enhanced FL, but provide a possible sensing platform through tuning the micro-environment of MnO2 QDs. The MnO2 QDs with outstanding performance may show great potential as promising fluorescent probes in the fields of biological imaging, optical sensing, drug delivery and therapy.
关键词： micro-environment engineering,reductive biomolecules,MnO2 QDs,enhanced fluorescence,Ag ions
更新于2025-09-19 17:13:59
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Germanium nanoparticles: intrinsic peroxidase-like catalytic activity and its biosensing application
摘要： In recent years, germanium nanoparticles (Ge NPs) have attracted considerable research attention because of its excellent electrical and optical properties. However, it is mainly applied in the field of solar cells, photodetectors and photothermal therapy. Actually, Ge NPs have the advantages of low toxicity and excellent biocompatibility, which means that they have great potential in biosensing applications. However, there are few related reports. In this paper, we discovered that Ge NPs have the intrinsic peroxidase-like catalytic activity and can significantly accelerate the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) by H2O2 for the first time. Compared with natural enzyme (horseradish peroxidase, HRP), Ge NPs maintain higher catalytic stability after treatment at different pH, temperature and ionic strength. Furthermore, a Ge NPs-based colorimetric platform was established for the first time to detect biomolecules with favourable sensitivity and selectivity, such as uric acid, glucose and choline. This work finds the new property of Ge NPs and extends its application in biosensing.
关键词： peroxidase-like activity,kinetics study,biomolecules detection,colorimetric platform,germanium nanoparticles
更新于2025-09-10 09:29:36
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Chiral Analysis || Raman Optical Activity
摘要： Raman optical activity (ROA) has many advantages over conventional Raman spectroscopy for investigation of chiral molecules, in general, and biological molecules, in particular, on account of their homochirality. Since it is a manifestation of vibrational optical activity [1], being complementary to vibrational circular dichroism (VCD), ROA is more sensitive to the 3D structures of chiral molecules through its dependence on their absolute handedness, which has led to its development as an incisive probe of the structure and behavior of biomolecules in aqueous solution. For example, ROA spectra obtained from proteins can provide detailed information on the secondary and tertiary structures adopted by polypeptide backbones. Additionally, ROA can probe the tautomers of side chains. In common with other vibrational spectroscopies, there is no restriction on the size of molecules, or in their type, that can be investigated by ROA, broadening its application to unfolded proteins, viruses, and carbohydrates.
关键词： vibrational circular dichroism,proteins,Raman optical activity,aqueous solution,carbohydrates,vibrational optical activity,biological molecules,biomolecules,viruses,chiral molecules
更新于2025-09-09 09:28:46