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Hot electron-induced electrochemiluminescence at cellulose derivatives-based composite electrodes
摘要： The possibility of using cellulose derivative films as (i) insulating material on metal electrodes or (ii) in composite electrode films on metal to produce hot electron-induced electrochemiluminescence (HECL) was studied. It was shown that the luminophores known to produce HECL at thin insulating film coated cathodes (e.g. Si/SiO2 and Al2O3 electrodes) produced HECL with the present novel electrodes. In the case of composite films consisting of cellulose material doped with conducting carbon particles, the optimal cellulose/carbon black ratios were investigated by measuring the time-resolved HECL (TR-HECL) of an aromatic Tb(III) chelate. In addition to Tb(III) chelate, other well-known labels, fluorescein and Ru(bpy)3 2+ chelate, were demonstrated to produce strong HECL at the present composite electrodes, which are more environmental friendly in disposable assay cartridges as the plastic-based composites we have studied previously. Thus, it is now possible on the present basis to manufacture biodegradable paper-based assay cartridges with HECL detection of labels at biodegradable electrodes. It was shown that the present composite films are stable over wide pH range, and also time-resolved detection of Ru(bpy)3 2+ chelate is possible although its luminescence lifetime if quite short. The calibration curves were measured for presently used aromatic Tb(III) chelate and for Ru(bpy)3 2+. The detection limit (s/n = 3) was 2 · 10?10 M for the Tb(III)-chelate and 4 · 10?9 M for Ru(bpy)3 2+ in time-resolved detection mode. The relative standard deviation for Tb(III)-L1 (n = 5) emission at 10?5 M concentration was 2%. Wide linear range and low detection limits suggests that cellulose based composite electrodes can be used in HECL bioaffinity assays which was finally demonstrated here by an immunometric immunoassay.
关键词： Bioaffinity assays,Cellulose derivatives,Lanthanide electrochemiluminescence,Immunoassays,Electrochemiluminescence,Hot electron electrochemistry
更新于2025-09-23 15:23:52
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Quantum Dots for F??rster Resonance Energy Transfer (FRET)
摘要： The analysis of biomolecular interactions using quantum dots (QDs) as both FRET donors and acceptors has become an established technique in the life sciences. This development has been driven by the unique properties of QDs, which include large surfaces for the attachment of biomolecules, high brightness and photostability, strong and spectrally broad absorption, and color-tunability via QD size, shape, and material. Applications include molecular rulers for structural analysis, small-molecule sensors, immunoassays, enzyme assays, nucleic acid assays, fluorescence imaging in-vitro and in-vivo, and molecular logic gates. Here, we will explain the theory of QD-based FRET, review some aspects of QD surface functionalization that are important for FRET, and highlight and discuss the advantages and disadvantages of QDs in FRET-biosensing using both spectroscopy and imaging techniques.
关键词： immunoassays,multiplexing,biosensors,FRET,imaging,quantum dots
更新于2025-09-19 17:13:59
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Sensitive and Quantitative Determination of Cardiac Troponin I Based on Silica-Encapsulated CdSe/ZnS Quantum Dots and a Fluorescence Lateral Flow Immunoassay
摘要： Cardiac troponin I is generally used as a biomarker of myocardial infarction or acute myocardial infarction. A timely and rapid diagnosis method for cardiac troponin I is of great importance. In this paper, a novel CdSe/ZnS quantum dot (QD) based fluorescence lateral flow immunoassay (QD-LFIA) is reported for the rapid and quantitative detection of cardiac troponin I in human serum. The water-soluble silica-encapsulated QDs (QDs@SiO2) serve as a new fluorescent probe and an economical, portable, quantitative instrument was used for the first time to detect cardiac troponin I antigen. By using the optimized immunoassay procedure with clinical samples, cardiac troponin I was determined in 10 min with high sensitivity (as low as 5.6 × 10?3 ng/mL), broad linear range (0.8–200 ng/mL), and good precision (the coefficient of variation was less than 10%). The comparison of this new QD-LFIA and a standard direct chemiluminescence assay demonstrated that the former platform was rapid, low-cost, and sensitive. It may be further applied to the quantitative determination and monitoring of cardiac troponin I levels in clinical use.
关键词： Cardiac troponin I,quantum dots,QD-based lateral flow immunoassays
更新于2025-09-16 10:30:52
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Core–Shell‐Heterostructured Magnetic–Plasmonic Nanoassemblies with Highly Retained Magnetic–Plasmonic Activities for Ultrasensitive Bioanalysis in Complex Matrix
摘要： Herein, a facile self-assembly strategy for coassembling oleic acid-coated iron oxide nanoparticles (OC-IONPs) with oleylamine-coated gold nanoparticles (OA-AuNPs) to form colloidal magnetic–plasmonic nanoassemblies (MPNAs) is reported. The resultant MPNAs exhibit a typical core–shell heterostructure comprising aggregated OA-AuNPs as a plasmonic core surrounded by an assembled magnetic shell of OC-IONPs. Owing to the high loading of OA-AuNPs and reasonable spatial distribution of OC-IONPs, the resultant MPNAs exhibit highly retained magnetic–plasmonic activities simultaneously. Using the intrinsic dual functionality of MPNAs as a magnetic separator and a plasmonic signal transducer, it is demonstrated that the assembled MPNAs can achieve the simultaneous magnetic manipulation and optical detection on the lateral flow immunoassay platform after surface functionalization with recognition molecules. In conclusion, the core–shell-heterostructured MPNAs can serve as a nanoanalytical platform for the separation and concentration of target compounds from complex biological samples using magnetic properties and simultaneous optical sensing using plasmonic properties.
关键词： magnetic–plasmonic nanoassemblies,highly retained magnetic-plasmonic activities,core–shell heterostructures,lateral flow,self-assembly,immunoassays
更新于2025-09-12 10:27:22
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A New Device Based on Interferometric Optical Detection Method for Label-Free Screening of C-Reactive Protein
摘要： In previous work, the performance of a compact and cost-effective point-of-care (PoC) device based on the increase relative optical power (IROP) methodology is reported and it is determined the enhancement in comparison with standard high-resolution spectrometry in terms of limit of detection. This paper describes a new label-free IROP-based biomedical device capable of working with low concentration of reagents and low sample volume per measurement in order to be used for screening different steps necessary in immunoassay optimization. This new approach significantly improves the sensing performance in terms of read-out signal (ΔIROP) per nanometer of biofilm in comparison with our previous work. This improvement is achieved due to the implementation of a laser as light source of the optical read-out system and the redesign of Fabry–Perot transducers by optimizing their reflectivity response and reducing their sensing area. For demonstrating the screening capability of this new PoC device in several immunoassays steps and methodologies, a C-reactive protein detection assay was carried out as a potential application and assay model. It is remarkable that only 10 μL of sample was used per measurement. This label-free IROP-based device complies an easy-to-use and cost-effective tool for immunoassays optimization in terms of performance, reagents cost, and measuring time.
关键词： C-reactive protein (CRP),label-free optical screening,immunoassays,point-of-care (PoC) devices,biosensors
更新于2025-09-10 09:29:36
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A Fluidic Biosensor Based on a Phase-Sensitive Low-Coherence Spectral-Domain Interferometer
摘要： A phase-sensitive fluidic biosensor based on a spectral-domain low-coherence interferometer is presented in this paper. With a fiber optic probe employing the common-path interferometric configuration, subnanometric changes in thickness of the molecular layers can be detected through phase analysis of the acquired interference signal from the sensor surface. Advantages of this biosensor include its picometer-scale thickness sensitivity, 13.9-ms time response, and tolerance to the fluctuation in concentration of the target solution. The capabilities of this biosensor in monitoring specific molecular binding and recognizing specific molecular was successfully demonstrated by using the reactions between the molecules of protein A and IgG. The calculated minimum detectable concentration of IgG is 0.11 μg/mL.
关键词： low-coherence spectral-domain interferometer,phase-sensitive,fluidic,immunoassays
更新于2025-09-10 09:29:36