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The linkage between the self-reproduction of compartments and the replication of DNA in a compartment is a crucial requirement for cellular life. In our giant vesicle (GV)-based model protocell, this linkage is achieved through the action of a supramolecular catalyst composed of membrane-intruded DNA and amphiphilic acid catalysts (C@DNA) in a GV membrane. In this study, we examined colocalization analysis for the formation of the supramolecular catalyst using a confocal laser scanning fluorescence microscope with high sensitivity and resolution. Red fluorescence spots emitted from DNA tagged with Texas Red (Texas Red-DNA) were observed in a GV membrane stained with phospholipid tagged with BODIPY (BODIPY-HPC). To our knowledge, this is the first direct observation of DNA embedded in a GV-based model protocellular membrane containing cationic lipids. Colocalization analysis based on a histogram of frequencies of “normalized mean deviation product” revealed that the frequencies of positively correlated [lipophilic catalyst tagged with BODIPY (BODIPY-C) and Texas Red-DNA] were significantly higher than those of [BODIPY-HPC and Texas Red-DNA]. This result demonstrates the spontaneous formation of C@DNA in the GV membrane, which serves as a lipo-deoxyribozyme for producing membrane lipids from its precursor.

A novel magnetic polysaccharide composite hydrogel was successfully constructed by using sodium alginate (SA) and carboxymethyl cellulose (CMC) as the backbone and filled with in situ Fe3O4 nanoparticles, which was then employed for removal of heavy metal ion from aqueous solution. The obtained magnetic SA/CMC composite hydrogel was characterized by Fourier transform infrared spectroscopy, fluorescence microscope, thermogravimetric and vibrating sample magnetometer. Effect of contact time, pH and adsorbent dosage on the adsorption of heavy metal ions by the magnetic SA/CMC hydrogel have also been studied. The results show that the prepared magnetic SA/CMC hydrogel can be effectively utilized in the removal of heavy metal ions from aqueous solution. The maximal adsorption capacity of Mn(II), Pb(II), and Cu(II) as calculated from the Langmuir model were 71.83, 89.49, and 105.93 mg/g, respectively. The adsorption process of the magnetic SA/CMC hydrogel on the heavy metal ions can be attributed to ion exchange and chemical adsorption. What’s more, the magnetic hydrogel exhibited high efficiency after four cycles, which indicating it offers great potential for practical application in the removal of heavy metal ions from aqueous solution.

A variety of methods concerning the identification of microplastics in environmental samples exist. While visual identification is often used, implemented easily, and cost-efficient but implying biased results, spectroscopic or chromatographic approaches are reliable but time-consuming and need specific equipment. Nile red staining is an available alternative and complement method for identifying microplastics. In this study, Nile red staining and subsequent photographing in a UV light photobox was tested on its reliability and feasibility. The approach was compared with a second identification process using again staining but a fluorescence microscope. Selected identified microplastic particles were analyzed by μ-Raman spectroscopy to prove their polymeric origin. The results show that the presented approach is faster compared with the use of a fluorescence microscope or μ-Raman spectroscopy. Furthermore, it is cost-effective as well as accurate for large microplastics > 0.63 mm and, therefore, may be applied when large sample volumes need to be analyzed. Graphical abstract

* Fluorescence staining provides a fast and easy method to quantify microplastics. * Factors that influence staining are summarized to obtain an optimum staining effect. * Natural organic matter can be stained by dye and interfere with quantification. * Fluorescence staining is applied in both field and laboratory studies. * Future work involves developing new dyes and automated image-analysis methods. Understanding the fate and toxicity of microplastics (MPs,<5 mm plastic particles) is limited by quantification methods. This paper summarizes the methods in use and presents new ones. First, sampling and pretreatment processes of MPs, including sample collection, digestion, density separation, and quality control are reviewed. Then the promising and convenient staining procedures and quantification methods for MPs using fluorescence dyes are reviewed. The factors that influence the staining of MPs, including their physicochemical properties, are summarized to provide an optimal operation procedure. In general, the digestion step is crucial to eliminate natural organic matter (NOM) to avoid interference in quantification. Chloroform was reported to be the most appropriate solvent, and 10-20 μg/mL are recommended as optimal dye concentrations. In addition, a heating and cooling procedure is recommended to maintain the fluorescence intensity of MPs for two months. After staining, a fluorescence microscope is usually used to characterize the morphology, mass, or number of MPs, but compositional analysis cannot be determined with it. These fluorescence staining methods have been implemented to study MP abundance, transport, and toxicity and have been combined with other chemical characterization techniques, such as Fourier transform infrared spectroscopy and Raman spectroscopy. More studies are needed to focus on the synthesis of novel dyes to avoid NOM's interference. They need to be combined with other spectroscopic techniques to characterize plastic composition and to develop image-analysis methods. The stability of stained MPs needs to be improved.

The self-assembly of biomacromolecules is an extremely important process. It is potentially useful in the fields of life science and materials science. To carry out the study on the self-assembly of proteins, it is necessary to find out the suitable self-assembly conditions, which have always been a challenging task in practice. Inspired by the screening technique in the field of protein crystallization, we proposed using the same screening technique for seeking suitable protein self-assembly conditions. Based on this consideration, we selected 5 proteins (β-lactoglobulin, hemoglobin, pepsin, lysozyme, α-chymotrypsinogen (II) A) together with 5 screening kits (IndexTM, BML, Morpheus, JCSG, PEG/Ion ScreenTM) to investigate the performance of these crystallization screening techniques in order to discover new optimized conditions of protein self-assembly. The screens were all kept at 293 K for certain days, and were analyzed using optical microscope, scanning electron microscope, transmission electron microscope, atomic force microscope, fluorescence microscope, and atomic absorption spectroscope. The results demonstrated that the method of protein crystallization screening can be successfully applied in the screening of self-assembly conditions. This method is fast, high throughput, and easily implemented in an automated system, with a low protein consumption feature. These results suggested that such strategy can be applied to finding new conditions or forms in routine research of protein self-assembly.Key points• Protein crystallization screening method is successfully applied in the screening of self-assembly conditions.• This screening method can be applied on various kinds of proteins and possess a feature of low protein consumption.• This screening method is fast, high throughput, and easily implemented in an automated system.

Osteoarthritis (OA) is the most common chronic joint disease worldwide. Chondrocyte, as the only resident cell type in cartilage, its apoptosis is of pathogenetic significance in OA. Mesenchymal stem cell (MSC)-based-therapy has been proved effective in OA in animals and clinical studies. Nowadays, the regenerative potential of MSC-based therapy is mostly attributed to its paracrine secretion, in which exosomes may play an important role. In the present study, we aimed to find out the significance of MSC-derived exosomes (MSC-Exos) on the viability of chondrocytes under normal and inflammatory conditions. Bone marrow MSCs (BMSCs) and chondrocytes from rabbits were cultured in vitro. BMSC-Exos were isolated by an ultracentrifugation method. Transmission electron microscopy and Western blot were used to identify exosomes. The internalization of BMSC-Exos into chondrocytes was observed by fluorescent microscope. The viability and apoptosis of chondrocytes induced by IL-1β were tested through MTT method, Hoechst33324 dying, and mitochondrial damage measurement. Phosphorylation of p38, ERK, and Akt were evaluated by Western blot. The results showed that BMSC-Exos were round-shaped. Co-culturing BMSC-Exos with chondrocytes could observe the uptake of BMSC-Exos by chondrocytes. The viability decreased, apoptosis occurred, and the mitochondrial membrane potential of chondrocytes changed a lot when IL-1β were given, but all the changes were almost abolished when BMSC-Exos was added. Furthermore, the phosphorylation of p38 and ERK were inhibited, and phosphorylation of Akt was promoted by BMSC-Exos compared with IL-1β group. The present study demonstrated that BMSC-Exos inhibited mitochondrial-induced apoptosis in response to IL-1β, and p38, ERK, and Akt pathways were involved. BMSC-Exo might represent a novel cell-free therapeutic approach for the treatment of OA.

This study introduces a novel enhancement method for latent fingerprint visualization in forensic investigations, featuring two key advancements: the use of UVITEX OB, a fluorescent compound traditionally found as an optical brightener in textiles, and the utility of a modified fluorescence microscope for fingerprint documentation. UVITEX OB's lipophilic nature, ability to be ground into an ultra-fine powder, its high fluorescence properties (quantum yield ∼ 0.9, excitation spectrum 350–450 nm), and high photostability make it an ideal compound for fingerprint visualization on both non-porous and porous surfaces. By replacing the high-power objective with a low-magnification lens assembly of longer focal length and increased working distance, the field of view was extended, enabling full-fingerprint fluorescence imaging. Additionally, genetic analysis of UVITEX OB - treated fingerprints confirms the compound’s ability to preserve sufficient DNA for a complete genetic profile, without interfering with critical DNA analysis techniques such as polymerase chain reaction (PCR) and short tandem repeat (STR) analysis. These findings support the potential forensic applicability of UVITEX OB in casework scenarios that require both latent fingerprint visualization and subsequent DNA profiling from the same trace evidence. •UVITEX OB fluorescent powder visualizes latent fingerprints under UV light and preserves DNA for profiling.•The modified fluorescence microscope captures entire fingerprints at high resolution for documentation.•UVITEX OB enables fluorescent detection of latent fingerprints on porous and non-porous surfaces.

Microplastics (MPs) are physical anthropogenic pollutants and their ability to act as contaminant vectors in biological matrices is of serious ecosystem and human health concern. In the present study, we have, for the first time, screened and detected MPs in the stomach of a select group of commonly consumed fish species from a municipal water supply lake (Eleyele) in Nigeria. A total of 109 fish samples consisting of eight (8) species: Coptodon zillii (CZ: n  = 38), Oreochromis niloticus (ON: n  = 43), Sarotheron melanotheron (SM: n  = 19), Chrysicthys nigrodigitatus (CN: n  = 3), Lates niloticus (LN: n  = 3), Paranchanna obscura (PO: n  = 1), Hemichromis fasiatus (HF: n  = 1), and Hepsetus odoe (HO: n  = 1) were collected between February–April, 2018. Fish stomach content was screened for the presence of MPs using the density gradient separation technique (NaCl hypersaline solution) and examined using a fluorescence microscope. MPs were present in all the species screened (except H. fasciatus ) with a frequency of 69.7% positive individuals in the examined species. MP prevalence was highest in ON (34%) > CZ (32%) > SM ( 13%) > CN (6%) and 5% each, for PO HO, and LN. On average, 1–6 MPs with sizes ranging between 124 μm and 1.53 mm were detected per individual. However, the highest number (34) of MPs was detected in the stomach of SM . Principal coordinate analysis (PCA) identified ecological variables such as habitat, feeding mode, and trophic levels as critical factors that may determine and influence MP uptake in fish population. The PCA showed stronger association between fish habitat, feeding mode, and trophic level with MP size and number in the benthopelagic species (ON CZ and SM), compared to demersal species (PO CN HO and LN). Given that MPs can act as vectors for the transfer of pathogens and environmental contaminants (both legacy and emerging), in addition to direct health risks to aquatic organisms, our findings raise concerns on the potential human/wildlife health effects of MPs in these economically and ecologically important food fishes.

Research on adeno-associated virus (AAV) and its recombinant vectors as well as on fluorescence microscopy imaging is rapidly progressing driven by clinical applications and new technologies, respectively. The topics converge, since high and super-resolution microscopes facilitate the study of spatial and temporal aspects of cellular virus biology. Labeling methods also evolve and diversify. We review these interdisciplinary developments and provide information on the technologies used and the biological knowledge gained. The emphasis lies on the visualization of AAV proteins by chemical fluorophores, protein fusions and antibodies as well as on methods for the detection of adeno-associated viral DNA. We add a short overview of fluorescent microscope techniques and their advantages and challenges in detecting AAV.

This study has been designed to examine incorporation of 7, 10 and 15% olive oil in milk-based media by using ultrasound (US) at 24 kHz, for 3 min in order to form new dairy-based, emulsifier-free emulsions. The prepared emulsions were characterized in terms of the emulsion capacity and stability, creaming index, zeta potential, droplet size, color and rheological analysis. The morphology of the emulsions was examined under the fluorescence microscope to evaluate the changes caused by US. The peroxide value and fatty acid composition were determined. After the treatment, application of the US increased the stability of emulsions. A decrease in the creaming index and droplet size and an increase in the zeta potential were observed. All the emulsions exhibited a weak gel structure. The fluorescence microscope images showed that the US decreased the size of oil droplet.