The reversible surface redox of polymer dots for the assay of total antioxidant capacity in food samples

A CRISPR/Cas12a-based fluorescence method for the amplified detection of total antioxidant capacity

The CRISPR/Cas12a system is a powerful signal amplification tool that has been widely used in nucleic acid detection. It has also been applied to the assay of non-nucleic acid targets, mainly relying on strategies for converting target determination into nucleic acid detection. Herein, we describe a CRISPR/Cas12a-based fluorescence method for sensitive detection of the total antioxidant capacity (TAC) by utilizing a strategy of converting TAC determination into Mn2+ detection. Specifically, the reduction of MnO2 nanosheets by antioxidants produces plenty of Mn2+, which accelerates the trans-cleavage activity of CRISPR/Cas12a. Thus, a fluorescence enhanced detection method for TAC was established, with a detection limit as low as 0.04 mg L-1 for a typical antioxidant, ascorbic acid. More importantly, this method has been proven to successfully analyze TAC in beverages. The excellent analytical performance of this method demonstrates the great potential of the CRISPR/Cas12a system in simple and sensitive TAC analysis.

Metal ions mediated carbon dots nanoprobe for fluorescent turn-on sensing of N-acetyl-L-cysteine

Carbon dots (CDs) was facilely synthesized from aspartic acid through a pyrolysis method in this work. Based on their favorable fluorescence property, CDs was utilized to design a metal ions-mediated fluorescent probe for N-acetyl-L-cysteine (NAC) detection. The fluorescence intensity of CDs was firstly quenched by manganese ion (Mn²⁺ ) through static quenching effect and subsequently restored by NAC via the combination with Mn²⁺ owing to the coordination effect. Therefore, the fluorescent turn-on sensing of NAC was actuated based on the fluorescence quenching stimulated by Mn²⁺ and recovery induced by coordination. The fluorescence recovery efficiencies showed a proportional range to the concentration of NAC in the range of 0.04-5 mmol L^-1 and the detection limit was 0.03 mmol L^-1 . Further, this metal ions-mediated fluorescent nanoprobe was applied to human urine sample detection and the standard recovery rates were located in the range of 97.62-102.34 %. It was the first time that Mn²⁺ was used to construct fluorescent nanoprobe for NAC. Compared to other heavy metal ions, Mn²⁺ with good biosecurity prevented the risk of application, which made the nanoprobe green and bio-practical. The facile synthesis of CDs and novel metal ions-mediated sensing mode made it a promising method for pharmaceutical analysis.

Fluorescent nanoparticles as tools in ecology and physiology

Fluorescent nanoparticles (FNPs) have been widely used in chemistry and medicine for decades, but their employment in biology is relatively recent. Past reviews on FNPs have focused on chemical, physical or medical uses, making the extrapolation to biological applications difficult. In biology, FNPs have largely been used for biosensing and molecular tracking. However, concerns over toxicity in early types of FNPs, such as cadmium-containing quantum dots (QDs), may have prevented wide adoption. Recent developments, especially in non-Cd-containing FNPs, have alleviated toxicity problems, facilitating the use of FNPs for addressing ecological, physiological and molecule-level processes in biological research. Standardised protocols from synthesis to application and interdisciplinary approaches are critical for establishing FNPs in the biologists' tool kit. Here, we present an introduction to FNPs, summarise their use in biological applications, and discuss technical issues such as data reliability and biocompatibility. We assess whether biological research can benefit from FNPs and suggest ways in which FNPs can be applied to answer questions in biology. We conclude that FNPs have a great potential for studying various biological processes, especially tracking, sensing and imaging in physiology and ecology.