A programmable DNA nanodevice for colorimetric detection of DNA methyltransferase activity using functionalized hemin/G-quadruplex DNAzyme.

The measurement of DNA methyltransferase (MTase) activity and screening of DNA MTase inhibitors holds significant importance for the diagnosis and therapy of methylation-related illness. Herein, we developed a colorimetric biosensor (PER-FHGD nanodevice) to detect DNA MTase activity by integrating the primer exchange reaction (PER) amplification and functionalized hemin/G-quadruplex DNAzyme (FHGD). By replacing the native hemin cofactor into the functionalized cofactor mimics, FHGD has exhibited significantly improved catalytic efficiency, thereby enhancing the detection performance of the FHGD-based system. The proposed PER-FHGD system is capable of detecting Dam MTase with excellent sensitivity, exhibiting a limit of detection (LOD) as low as 0.3 U/mL. Additionally, this assay demonstrates remarkable selectivity and ability for Dam MTase inhibitors screening. Furthermore, using this assay, we successfully detect the Dam MTase activity both in serum and in E. coli cell extracts. Importantly, this system has the potential to serve as a universal strategy for FHGD-based diagnosis in point-of-care (POC) tests, by simply altering the recognition sequence of the substrate for other analytes.

A vaccine delivery system promotes strong immune responses against SARS-CoV-2 variants.

Global coronavirus disease 2019 (COVID-19) pandemics highlight the need of developing vaccines with universal and durable protection against emerging SARS-CoV-2 variants. Here we developed an extended-release vaccine delivery system (GP-diABZI-RBD), consisting the original SARS-CoV-2 WA1 strain receptor-binding domain (RBD) as the antigen and diABZI stimulator of interferon genes (STING) agonist in conjunction with yeast ß-glucan particles (GP-diABZI) as the platform. GP-diABZI-RBD could activate STING pathway and inhibit SARS-CoV-2 replication. Compared to diABZI-RBD, intraperitoneal injection of GP-diABZI-RBD elicited robust cellular and humoral immune responses in mice. Using SARS-CoV-2 GFP/ΔN transcription and replication-competent virus-like particle system (trVLP), we demonstrated that GP-diABZI-RBD-prototype vaccine exhibited the strongest and durable humoral immune responses and antiviral protection; whereas GP-diABZI-RBD-Omicron displayed minimum neutralization responses against trVLP. By using pseudotype virus (PsVs) neutralization assay, we found that GP-diABZI-RBD-Prototype, GP-diABZI-RBD-Delta, and GP-diABZI-RBD-Gamma immunized mice sera could efficiently neutralize Delta and Gamma PsVs, but had weak protection against Omicron PsVs. In contrast, GP-diABZI-RBD-Omicron immunized mice sera displayed the strongest neutralization response to Omicron PsVs. Taken together, the results suggest that GP-diABZI can serve as a promising vaccine delivery system for enhancing durable humoral and cellular immunity against broad SARS-CoV-2 variants. Our study provides important scientific basis for developing SARS-CoV-2 VOC-specific vaccines.

Sizes and ligands tuned gold nanocluster acting as a new type of monoamine oxidase B inhibitor.

Monoamine oxidase inhibitors (MAOIs) are a class of drugs that can be used in the treatment of Parkinson's disease, clinical depression, and anxiety by targeting monoamine oxidase B (MAO). However, the side effects of MAOIs drive the requirement of a new framework of enzyme inhibitors development. In this context, a new type of MAOI has been built on the framework of gold nanoclusters (AuNCs), realizing the transformation from no function of small molecules to MAOI function of ligand-modified AuNCs. The MAOI activity of fabricated AuNCs can be achieved by size control and specific ligands modification. In this work, AuNCs modified with cysteamine or 4-aminothiophenol, about 1-3 nm in size, were found to have MAOI activity (MAOI-like AuNCs) and their characterization has been extensively described. Meanwhile, the possible mechanism behind this MAOI activity has been explored and it is believed that the proper size of AuNCs with ligands containing amino groups can bind tightly with the entrance to active sites of MAO, blocking the enzyme interacting with its substrates, thereby realizing the function of MAOI. Last, the antimicrobial activity and the performance of the MAOI-like AuNCs in the human blood sample were explored and suggested that MAOI-like AuNCs do not possess strong antimicrobial activity and have no visualized side effect on blood cells, although the by-product peroxide of MAO reaction may reshape the white blood cells. The research in this work may shed some light on the development of a new type of enzyme inhibitor based on the framework of nanomaterials.