Rapid and sensitive visual detection of avian leukosis virus by reverse transcription loop-mediated isothermal amplification combined with a lateral flow immunochromatographic strip assay.

Considering that avian leukosis virus (ALV) infection has inflicted massive economic losses on the poultry breeding industry in most countries, its early diagnosis remains an important measure for timely treatment and control of the disease, for which a rapid and sensitive point-of-care test is required. We established a user-friendly, economical, and rapid visualization method for ALV amplification products based on reverse transcription loop-mediated isothermal amplification (RT-LAMP) combined with an immunochromatographic strip in a lateral flow device (LFD). Using the ALVp27 gene as the target, five RT-LAMP primers and one fluorescein-isothiocyanate-labeled probe were designed. After 60 min of RT-LAMP amplification at 64 °C, the products could be visualized directly using the LFD. The detection limit of this assay for ALV detection was 102 RNA copies/µL, and the sensitivity was 100 times that of reverse transcription polymerase chain reaction (RT-PCR), showing high specificity and sensitivity. To verify the clinical practicality of this assay for detecting ALV, the gold standard RT-PCR method was used for comparison, and consistent results were obtained with both assays. Thus, the assay described here can be used for rapid detection of ALV in resource-limited environments.

Carbon dots@noble metal nanoparticle composites: research progress report.

Carbon dots@noble metal nanoparticle composites are formed by combining carbon dots and metal nanoparticles using various strategies. Carbon dots exhibit a reducing ability and function as stabilisers; consequently, metal-ion solutions can be directly reduced by them to synthesise gold, silver, and gold-silver alloy particles. Carbon dots@gold/silver/gold-silver particle composites have demonstrated the potential for several practical applications owing to their superior properties and simple preparation process. Until now, several review articles have been published to summarise fluorescent carbon dots or noble metal nanomaterials. Compared with metal-free carbon dots, carbon dots@noble metal nanoparticles have a unique morphology and structure, resulting in new physicochemical properties, which allow for sensing, bioimaging, and bacteriostasis applications. Therefore, to promote the effective development of carbon dots@noble metal nanoparticle composites, this paper primarily reviews carbon dots@gold/silver/gold-silver alloy nanoparticle composites for the first time in terms of the following aspects. (1) The synthesis strategies of carbon dots@noble metal nanoparticle composites are outlined. The principle and function of carbon dots in the synthesis strategies are examined. The advantages and disadvantages of these methods and composites are analysed. (2) The characteristics and properties of such composites are described. (3) The applications of these composite materials are summarised. Finally, the potentials and limitations of carbon dots@noble metal nanoparticle composites are discussed, thus laying the foundation for their further development.

Determination of the Catalytic Activity of a Peroxidase-like Nanozyme and Differences among Layered Double Hydroxides with Different Anions and Cations.

Nanomaterials with enzyme-like activity, namely, nanozymes, have been widely used as substitutes for natural enzymes, and they show excellent potential for application in many fields, such as biotechnology, environmental chemistry, and medicine. Layered double hydroxides (LDHs) are inorganic nanomaterials with adjustable compositions, simple preparation methods, and low costs and are some of the most promising candidate materials for the preparation of nanozymes. Here, we studied the syntheses and peroxidase-like activities of LDHs with four anions and four cations. First, LDHs prepared by the coprecipitation-hydrothermal method adopted hexagonal lamellar structures with good dispersion and uniform particle sizes. The Lambert-Beer law showed that the prepared LDHs exhibited good enzymatic activity. Later, the Km and Vmax values of the LDHs with different anionic/cationic materials intercalated into their structures were compared. Under the optimum conditions, the Vmax of Mg2Al-NO3-LDH was 7.35 × 10-2, which is 2-4 times higher than that of the LDHs containing other anions; the Vmax values of NiFe-LDH and FeAl-LDH were 0.152 and 0.284, respectively, which are 10 times higher than those of the LDHs with other cations. Importantly, according to kinetic analyses of the enzymatic reactions, the effects of Fe2+ and Fe3+ on the LDH enzyme activity were greater than those of the intercalated anions. This study showed that NiFe-LDH and FeAl-LDH with high catalytic activities are candidate materials for peroxidase simulations, which may provide new strategies for the application of LDHs in biosensors, antioxidants, biotechnology, and other nanozyme applications.

One-step facile preparation of carbon dots with high fluorescence quantum yield and application in rapid latent fingerprint detection.

The development of luminescent materials greatly affects the development of fluorescence imaging technology. The preparation of carbon dots (CDs) with high photoluminescence quantum yield (PLQY) in the solid-state is challenging due to excessive resonance energy transfer (RET) and direct π-π interactions. In this study, we synthesized carbon dots that exhibit green fluorescence (GCDs) with absolute PLQYs up to 35.65% in one step by a microwave-assisted method. In the solid-state, the absolute PLQY reached 19.25%. Then, the GCDs were mixed with soluble starch in appropriate proportions, which improved the adsorption and dispersion of the GCDs and greatly reduced the cost of the fingerprint powder, and increased the absolute PLQY of the fingerprint powder to 41.75%. Finally, we prepared GCDs for preliminary fabrication of luminescent films, and the GCD-starch powder was successfully applied to high-quality latent fingerprint (LFP) imaging. The related properties of GCDs and the LFP detection performance of fingerprint detection powders prepared by GCDs were studied in detail. The results showed that the LFP system developed with GCDs-starch powder visualized LFPs with high definition and contrast under different conditions, and GCDs had potential for application in light-emitting devices. This study developed a new type of solid-state luminescent CDs and demonstrated that these GCDs have great application potential for LFP detection. This study may also provide inspiration for other applications based on efficient solid-state fluorescence.

Synthesis of Eco-Friendly Silver Nanoparticles Using Glycyrrhizin and Evaluation of Their Antibacterial Ability.

In the present study, the biosynthesis of silver nanoparticles (AgNPs) and their antibacterial activity against gram-positive and gram-negative bacteria were investigated. Glycyrrhizin (GL) was used as a reducing agent and stabilizer to rapidly prepare the AgNPs. The distinctive absorption peak at 419 nm confirmed the formation of GL-reduced AgNPs. The TEM and particle size analysis shows that the prepared GL-reduced AgNPs were mostly circular with good dispersion and a relatively uniform particle size of 35 nm on average. Fourier transform infrared spectroscopy analysis was performed to identify the possible biomolecules in the capping and active stabilization of the GL-reduced AgNPs. The antibacterial activity of the GL-reduced AgNPs was analyzed with the Oxford cup diffusion method and filter paper diffusion method. The experimental results show that these properties endowed the GL-reduced AgNPs with high antibacterial activity against Escherichia coli and Staphylococcus aureus and lay a foundation for the use of colloidal silver in antibacterial applications. The GL-reduced AgNPs also had stronger antibacterial activity than sodium citrate-reduced AgNPs, which indicates the advantages of GL-reduced AgNPs compared with sodium citrate-reduced AgNPs in inducing bacteriostasis. The cytotoxicity of GL-reduced AgNPs on human kidney epithelial 293A (HEK293) cells was evaluated via the MTT assay. The results show that GL-reduced AgNPs had lower toxicity to HEK293 cells than sodium citrate-AgNPs, which indicates that the as-prepared GL-reduced AgNPs are environmentally friendly.