Rapid detection of trace malachite green using a fluorescence probe based on signal amplification through electrostatic self-assembly of CdTe QDs and polystyrene microsphere

Preparation of fluorescent polyurethane microspheres and their applications as reusable sensor for 4-nitrophenol detection and as microplastics model for visualizing polyurethane in cells and zebrafish

Fluorescent microspheres are of significant interests due to their wide applications in biotechnology fields. However, their preparation presents several challenges, such as the need for dye labeling, the complexity of materials and often sophisticated preparation conditions. Here a simple process for hydrophilic and crosslinked polyurethane (CPU) microspheres, with carboxyl groups on the surface via one-step precipitation polymerization in 40 min, is presented. The microsphere size is easily adjusted by varying experimental conditions. CPU microspheres exhibit high thermal and pH stability with good redispersibility in water, and emit fluorescence without any modification or dye labeling. The emission mechanism is discussed. CPU microspheres are used as fluorescent probe to detect 4-nitrophenol (4-NP) based on their emission in UV light region, with excellent selectivity and sensitivity. In addition, they are reusable with detection limit unchanged after 7 cycles of reuses, a significant feature of this work. The mechanism of fluorescence detection is thoroughly explored and ascribed to the internal filtration effect. Based on the emission in visible light region, CPU microspheres are used as a model of PU microplastics (MPs) to visualize their biodistribution in HeLa and macrophage cells, as well as in zebrafish larvae, providing a reliable tracer for the visualization and tracking of PU MPs in organisms.

Dual-color immunochromatographic test strip for simultaneous sensitive detection of malachite green and leucomalachite green residues in fish and shrimp meat samples

A sensitive dual immunochromatographic test strip (dual-ICTS) was developed to detect malachite green (MG) and its metabolite, leucomalachite green (LMG), using two types of gold nanoparticles: round-shaped (red) and star-shaped (blue). The detection limits were determined to be 0.221 μg L-1 for MG and 0.214 μg L-1 for LMG, respectively. The dual-ICTS provided a cut-off value of 1.8 μg L-1 for MG and LMG detection. The dual-ICTS successfully detected MG and LMG in food samples, with recovery rates ranging from 86 % to 116 %. The dual-ICTS was evaluated by correlation analysis between the proposed assay and the well-established enzyme-linked immunosorbent assay in the MG and LMG detection. This is the first report on the development of the ICTS that can detect both MG and LMG at the same time within only 5 min, making it a sensitive and rapid tool for on-site detection.

Simultaneous detection of two subtypes of extracellular vesicles using ultrabright fluorescent nanosphere-based test strips

In recent years, the cargo profiles of extracellular vesicles (EVs), which were inherited from their parent cells, have emerged as a reliable biomarker for liquid biopsy (LB) in disease diagnosis, prognosis, and treatment monitoring. EVs secreted by different cells exhibit distinct characteristics, particularly in terms of disease diagnosis and prediction. However, currently available techniques for the quantitative analysis of EV cargoes, including enzyme-linked immunosorbent assay (ELISA), cannot specifically identify the cellular origin of EVs, thus seriously affecting the accuracy of EV-based liquid biopsy. In light of this, we here developed ultrabright fluorescent nanosphere (FNs)-based test strips which have the unique capability to specifically assess the levels of PD-L1-positive EVs (PD-L1+ EVs) derived from both tumor cells and immune cells in bodily fluids. The levels of PD-L1+ EV subpopulations in human saliva were quantified using the ultrabright fluorescent nanosphere-based test strips with more convenience and higher efficiency (detection time <30 min). Results demonstrated that the fluorescence intensity of the test line exhibited a good linear relationship respectively with the PD-L1 levels of tumor cell- (R2 = 0.993) and immune cell-derived EVs (R2 = 0.982) in human saliva. By assessing the levels of PD-L1+ EV subpopulations, our test strips hold immense potential for advancing the application of PD-L1+ EV subpopulation-based predictions in tumor diagnosis and prognosis evaluation. In summary, by integrating the benefits of FNs and lateral flow chromatography, we here provide a strategy to accurately measure the cargo levels of EVs originating from diverse cell sources in bodily fluids.

Facile fluorescence detection of malachite green in fish using molecularly imprinted polymers doped CdTe quantum dots based system

Malachite green (MG) possesses high toxicity, therefore, the detection of MG in fish tissues is of vital importance. A novel core-shell MIPs doped CdTe quantum dots coated silica nanoparticles (CdTe-MIP/SiO2 NPs) were synthesized via a simple one-pot strategy. The materials were characterized carefully. The resulting CdTe-MIP/SiO2 NPs were coated on the thin layer chromatography plate, and coupled with miniaturized fluorimeter for fluorescence detection of MG in fish samples. The resulting CdTe-MIP/SiO2 NPs based system possessed good linearity (0.01 ∼ 20 μmol/L), high recoveries (98.36 %∼101.45 %) and low detection limit (3.7 nmol/L) for MG. Furthermore, CdTe-MIP/SiO2 NPs based system were employed to measure fish samples spiked with MG, meanwhile, HPLC was utilized to evaluate the accuracy and reliability. And the paired t-test was conducted to evaluate differences between fluorescence method and HPLC, P > 0.05 means no significant difference was observed, the results demonstrated that both fluorescence method and HPLC are suitable for MG analysis.

Recent Advances in and Application of Fluorescent Microspheres for Multiple Nucleic Acid Detection

Traditional single nucleic acid assays can only detect one target while multiple nucleic acid assays can detect multiple targets simultaneously, providing comprehensive and accurate information. Fluorescent microspheres in multiplexed nucleic acid detection offer high sensitivity, specificity, multiplexing, flexibility, and scalability advantages, enabling precise, real-time results and supporting clinical diagnosis and research. However, multiplexed assays face challenges like complexity, costs, and sample handling issues. The review explores the recent advancements and applications of fluorescent microspheres in multiple nucleic acid detection. It discusses the versatility of fluorescent microspheres in various fields, such as disease diagnosis, drug screening, and personalized medicine. The review highlights the possibility of adjusting the performance of fluorescent microspheres by modifying concentrations and carrier forms, allowing for tailored applications. It emphasizes the potential of fluorescent microsphere technology in revolutionizing nucleic acid detection and advancing health, disease treatment, and medical research.

A recyclable Eu3+-functionalized dual-emissive metal-organic framework for portable, rapid detection and efficient removal of malachite green

A europium-functionalized, dual-emissive, metal-organic framework-based fluorescence sensor (EuUCNDA) was constructed via post-synthetic modification of an UiO-66-type precursor through coordination interactions. EuUCNDA exhibited extremely high selectivity and sensitivity for malachite green (MG) with a low detection limit of 13.01 nM, a wide linear concentration range (0.05-50 μM), excellent anti-interference properties, a rapid response (<1 min), and the possibility of recycling. The good sensing performance of EuUCNDA enables the practical detection of MG in fish pond water and grass carp with good recoveries. Moreover, EuUCNDA can be reused for sensing MG and over 90% of fluorescence intensity can be restored after 7 cycles. Furthermore, EuUCNDA-embedded paper-based sensors combined with smartphone imaging afford portable and visual monitoring of MG in real samples. Notably, besides good sensing performance, EuUCNDA could efficiently remove MG from water. Hence, this work provides a recyclable and sensitive fluorescence sensor for portable, visual, rapid detection and efficient removal of MG.

Simple synthesis of green luminescent N-doped carbon dots for malachite green determination

In this paper, novel N-doped carbon dots (N-CDs) were prepared from fuchsin basic and ethylenediamine tetraacetic acid-disodium salt (EDTA-2Na). The N-CDs were characterized by a series of techniques and it was found that the average particle size was 2.75 nm, and the surface had functional groups such as -NH₂ and -COOH. Interestingly, N-CDs exhibited a fast and sensitive response to malachite green (MG), which may be due to the inner filter effect (IFE). A method for the detection of MG in water samples from Jinyang Lake was developed using N-CDs, with a limit of detection (LOD) as low as 27.28 nM. Furthermore, N-CDs were utilized in the biological imaging of Arabidopsis thaliana.

Immunoprofiling of Severity and Stage of Bacterial Infectious Diseases by Ultrabright Fluorescent Nanosphere-Based Dyad Test Strips

Bacterial infectious diseases are common clinical diseases that seriously threaten human health, especially in countries and regions with poor environmental hygiene. Due to the lack of characteristic clinical symptoms and signs, it is a challenge to distinguish a bacterial infection from other infections, leading to misdiagnosis and antibiotic overuse. Therefore, there is an urgent need to develop a specific method for detection of bacterial infections. Herein, utilizing ultrabright fluorescent nanospheres (FNs) as reporters, immunochromatographic dyad test strips are developed for the early detection of bacterial infections and distinction of different stages of bacterial infectious diseases in clinical samples. C-reactive protein (CRP) and heparin-binding protein (HBP) are quantified and assayed because their levels in plasma are varied dynamically and asynchronously during the progression of the disease. The detection limits of CRP and HBP can reach as low as 0.51 and 0.65 ng/mL, respectively, due to the superior fluorescence intensity of each FN, which is 570 times stronger than that of a single quantum dot. The assay procedure can be achieved in 22 min, fully meeting the needs of rapid and ultrasensitive detection in the field. This constructed strip has been successfully used to profile the stage and severity of bacterial infections by monitoring the levels of CRP and HBP in human plasma samples, showing great potential as a point-of-care biosensor for clinical diagnosis. In addition to bacterial infections, the developed ultrabright FN-based point-of-care testing can be readily expanded for rapid, quantitative, and ultrasensitive detection of other trace substances in complex systems.

PVP–gold–copper nanocluster based NIR fluorescence probe for sensitive detection of malachite green

A novel NIR fluorescent probe based on PVP–Au/CuNCs has been developed, exhibiting good selectivity and stability for detecting malachite green (MG).

A review of the incorporation of QDs and imprinting technology in optical sensors – imprinting methods and sensing responses

This review aims to cover the simultaneous method of using molecularly imprinted technology and quantum dots (QDs) as well as its application in the field of optical sensors.

The Recent Advances of Fluorescent Sensors Based on Molecularly Imprinted Fluorescent Nanoparticles for Pharmaceutical Analysis

Fluorescent nanoparticles have good chemical stability and photostability, controllable optical properties and larger stokes shift. In light of their designability and functionability, the fluorescent nanoparticles are widely used as the fluorescent probes for diverse applications. To enhance the sensitivity and selectivity, the combination of the fluorescent nanoparticles with the molecularly imprinted polymer, i.e. molecularly imprinted fluorescent nanoparticles (MIFN), was an effective way. The sensor based on MIFN (the MIFN sensor) could be more compatible with the complex sample matrix, which was especially widely adopted in medical and biological analysis. In this mini-review, the construction method, detective mechanism and types of MIFN sensors are elaborated. The current applications of MIFN sensors in pharmaceutical analysis, including pesticides/herbicide, veterinary drugs/drugs residues and human related proteins, are highlighted based on the literature in the recent three years. Finally, the research prospect and development trend of the MIFN sensor are forecasted.