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Utility of surface plasmon resonance response of silver nanoparticles for assay of Teicoplanin in human plasma using spectrofluorimetric technique
摘要： Teicoplanin (TEIC) is a glycopeptide antimicrobial medication for management of several bacterial infectious diseases caused by gram-positive bacteria including methicillin-resistant Staphylococcus aureus and Enterococcus faecalis. Novel, very simple, fast and cost-effective two spectrofluorimetric methods were developed for the ultra-trace determination of TEIC in pharmaceutical vials and human plasma. The investigated methods based on measuring the fluorescence of TEIC in methanol (method A) and enhancing its fluorescence by 10 folds using silver nanoparticles (AgNPs) without any solvent extraction (method B). The fluorescence of TEIC was investigated at 385nm (excitation at 335 nm) with calibration ranged from 1 to 25 ng mL?1 and from 0.6 to 30 ng mL?1 with Limit of detection (LOD) of 280 and 160 pg mL?1 for method A and B respectively. The established methods were optimized, validated and bio-analytically validated via ICH and US-FDA guidelines. The performed methods were used to determine TEIC in human plasma with high percentage recovery of 98.8 ± 1.75. Further, the proposed methods were applied to study the stability of TEIC after exposure to various degradation stress conditions and kinetic degradations.
关键词： Spectrofluorimetry,Teicoplanin,Silver nanoparticles,Metal-enhanced fluorescence,Human plasma analysis
更新于2025-09-23 15:23:52
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Biosensor for point-of-care analysis of immunoglobulins in urine by metal enhanced fluorescence from gold nanoparticles
摘要： Biosensors are easy-to-use and cost-effective devices that are emerging as an attracting tool not only in settling diagnosis or in disease monitoring, but also in mass screening tests, a timely topic that impacts on daily life of the whole society. Nanotechnologies lend themselves to the development of highly sensitive device whose realization has become a very interdisciplinary topic. Relying on the enhancement of the fluorescence signal detected at the surface of patterned gold nanoparticles, we report the behavior of an analytical device in detecting immunoglobulins in real urine samples that shows a limit of detection of approximately 8 μg/L and a linear range of 10-100 μg/L well below the detection limit of nephelometric method, which is the reference method for this analysis. These performances have been reached thanks to an effective surface functionalization technique and can be improved even more if superhydrophobic features of the substrate we produce will be exploited. Since the analyte recognition is realized by antibodies the specificity is very high and, in fact, no interference has been detected by other compounds also present in the real urine samples. The device has been assessed on serum samples by comparing IgG concentrations values obtained by the biosensor with those provided by a nephelometer. In this step we found that our approach allows the analysis of the whole blood without any pretreatment; moreover, it is inherently extendable to the analysis of most biochemical markers in biological fluids.
关键词： antibody,point-of-care device,nanostructured gold surface,photochemical immobilization technique,gold nanoparticles,metal enhanced fluorescence,biosensors
更新于2025-09-23 15:22:29
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Aluminum foil as a substrate for metal enhanced fluorescence of bacteria labelled with quantum dots, shows very large enhancement and high contrast
摘要： Very high surface/metal enhanced fluorescence was observed for E. coli single bacteria cells labeled with composite CdSeS/ZnS quantum dots (QDs) on three substrates: aluminum foil, aluminum film and gold film. The enhancement factors relative to maximum fluorescence intensity on glass for those substrates were in the range of several hundred (up to 500) for two-excitation wavelengths 532 and 633 nm. Contrast as a ratio of signals from QD labeled to signals of QD unlabeled (control) cells was also in the range of 100 s for those substrates and the highest contrast of 370 was observed on Al film. When CdTe QDs were used for labelling cells on all substrates or when fluorescence from cells with both QDs was measured on silver film, low or no enhancement was observed. Overall, untreated aluminum foil demonstrated great potential as low-cost substrate for surface/metal enhanced fluorescence, which delivers even more reproducible signal than gold film.
关键词： E. coli,Bacteria,Enhancement facor,Quantum dots,Single bacterial cell detection,Metal enhanced fluorescence,Contrast,Surface enhanced fluorescence,Aluminum foil,QD toxicity
更新于2025-09-23 15:21:01
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Metal enhanced fluorescence biosensing: from ultra-violet towards second near-infrared window
摘要： To increase disease survival rates, there is a vital need for diagnosis at very preliminary stages. Then, low concentrations of biomarkers are present which must be effectively detected and quantified for reliable diagnosis. Fluorescent biosensing is commonly enabled through the labelling of these biomarkers with nanostructures and fluorophores. Metal Enhanced Fluorescence (MEF) is a phenomenon whereby the intensity of a fluorescent biosensor signal can be considerably enhanced by placing a metallic nanostructure and fluorophore in close proximity. Importantly, this allows for an even lower detection limit and thus earlier diagnosis. In recent years, extraordinary efforts have been made in the understanding of how the chemical and physical properties of nanomaterials may be exploited advantageously. Via precise nanoscale engineering, it is possible to optimize the optical properties of plasmonic nanomaterials, which now need to be refined and applied in diagnostics. Through MEF, the intensity of this signal can be related in direct proportion to analyte concentration, allowing for diagnosis of disease at an earlier stage than previously. This review paper outlines the potential and recent progress of applied MEF biosensors, highlighting their substantial clinical potential. MEF biosensors are presented both upon assay-based platforms and in solution, with comments on the various metallic nanoparticle morphologies available. This is explored across various emission wavelengths from ultra-violet to the second near infrared window (NIR-II), emphasising their wide applicability. Further to this, the importance of near infrared (NIR-I and NIR-II) biosensing is made clear as it allows for higher penetration in biological media. Finally, by developing multiplexing techniques, multiple and simultaneous analyses of analytes can be achieved. Through the incorporation of metal enhanced fluorescence into biosensing, it will be possible to diagnose disease more rapidly and more reliably than before, with the potential to save countless lives.
关键词： nanomaterials,biosensing,Metal Enhanced Fluorescence,fluorophores,multiplexing,near-infrared
更新于2025-09-19 17:15:36
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Plasmonic Silver Nanoprism-Induced Emissive Mode Control between Fluorescence and Phosphorescence of a Phosphorescent Palladium Porphyrin Derivative
摘要： We have succeeded in significantly enhancing fluorescence from intrinsically phosphorescent palladium octaethylporphyrin (Pd-porphyrin) that has an intersystem crossing efficiency of ~1 by using silver nanoprisms (AgPRs). This was achieved by controlling the wavelength of localized surface plasmon (LSP) resonance of AgPRs and the distance between the Pd-porphyrin molecules and the AgPR surfaces. In addition to enhancing phosphorescence by spectrally overlapping the phosphorescence band with the LSP resonance band, tuning the LSP wavelength to approximately 520 nm led to the appearance of a new emission band around the wavelength corresponding to the fluorescent radiation. The appearance of fluorescence suggests that the nonradiative energy transfer from the singlet excited state of Pd-porphyrin to the LSP of AgPRs overcame the ultrafast intramolecular intersystem crossing to the triplet excited state, manifesting the spectral properties of the singlet excited state of Pd-porphyrin. The fluorescence nature of this radiation was strongly supported by lifetime measurements of the hybrids of Pd-porphyrin and AgPRs. Furthermore, the dependence of the emissive intensities on the distance between the Pd-porphyrin molecules and the AgPR surfaces showed interesting opposite trends. The fluorescence intensity was increased as the distance between the molecules and the AgPRs was decreased from 10.5 nm to 1 nm, while the phosphorescence intensity was decreased, which indicates that the LSP-induced fluorescence radiation process from Pd-porphyrin near the AgPRs outweighed the quenching by the AgPRs, even though the phosphorescence significantly suffered quenching.
关键词： silver nanoprisms,localized surface plasmon resonance,palladium porphyrin,phosphorescence,metal-enhanced fluorescence,fluorescence,intersystem crossing
更新于2025-09-19 17:13:59
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Metal-Enhanced Fluorescence of Gold Nanoclusters as a Sensing Platform for Multi-component Detection
摘要： Metal-enhanced fluorescence (MEF) has been applied to construct biosensing systems in the recent decades owing to its favorable optical properties. Herein, silver nanoparticles (AgNPs) are used to enhance fluorescence of gold nanoclusters (AuNCs), by fabricating a core-shell composite nanostructure Ag@SiO2-AuNCs consisting of a silver core, a silica shell and an outer conjugated layer of AuNCs. The core-shell MEF-capable nanoparticles possess water dispersibility, high stability and good biocompatibility. The interaction between AuNCs on the surface of the outer silica shell and the silver core, significantly improves the excitation efficiency, and thus enhances the fluorescence emission, photostability and quantum yield of the AuNCs. The composite nanoparticle Ag@SiO2-AuNCs provides a fluorescence enhancement of up to 3.21-fold when the separation distance (the thickness of the silica shell) is about 10 nm. Finally, the composite nanostructures have further been applied to develop a sensing platform for multi-component detection based on the MEF capability and the OFF-ON-OFF switching nature of the fluorescence signal, and the detection limits for Cu2+, inorganic pyrophosphate (PPi) and pyrophosphatase (PPase) are 39 nM, 78.7 nM and 0.976 mU, respectively. This platform has been applied to detect Cu2+, PPi and PPase with satisfactory results in living cells.
关键词： Metal-enhanced fluorescence (MEF),Fluorescence sensor,Core-shell composite nanostructure,Gold nanoclusters (AuNCs)
更新于2025-09-10 09:29:36
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Visualization of Endogenous Hydrogen Sulfide in Living Cells based on Au Nanorods@Silica Enhanced Fluorescence
摘要： Hydrogen sulfide as a gas indicator molecule plays an important role in various human physiological processes. However, due to the high volatility and diffusivity of H2S in biological systems, it is very difficult to implement a precise assay for H2S detection. Compared with the destructive instrumental methods, assays based on fluorescence probes provide noninvasive and real-time detections of H2S in living cells. In this work, we presented a fluorescent nanoprobe based on dye-functionalized Au nanorods (NRs)@silica for sensitive and selective detection of H2S in vitro and living cells. With the metal enhanced fluorescence effect, the fluorescence turn-on and turn-off were controlled by the formation and disassembly of coordination compound between dyes and copper ions. Silica matrix was used to coat the Au NRs to prevent them from the biological cytotoxicity. The effects of the different distances between Au NRs and fluorophores on fluorescent enhancement were explored and approximately 5-fold fluorescence enhancement was obtained with a distance of 22 nm. A detection of limit of 17 nM was achieved. In addition, visualization of exogenous and endogenous H2S in living cells was validated.
关键词： nanoprobes,Au nanorods@silica,metal enhanced fluorescence,living cells,endogenous H2S
更新于2025-09-04 15:30:14