Utilization of DNA and 2D metal oxide interaction for an optical biosensor.

The efficient monitoring and early detection of viruses may provide essential information about diseases. In this work, we have highlighted the interaction between DNA and a two-dimensional (2D) metal oxide for developing biosensors for further detection of viral infections. Spectroscopic measurements have been used to probe the efficient interactions between single-stranded DNA (ssDNA) and the 2D metal oxide and make them ideal candidates for detecting viral infections. We have also used fully atomistic molecular dynamics (MD) simulation to give a microscopic understanding of the experimentally observed ssDNA-metal oxide interaction. The adsorption of ssDNA on the inorganic surface was found to be driven by favourable enthalpy change, and 5'-guanine was identified as the interacting nucleotide base. Additionally, the in silico assessment of the conformational changes of the ssDNA chain during the adsorption process was also performed in a quantitative manner. Finally, we comment on the practical implications of these developments for sensing that could help design advanced systems for preventing virus-related pandemics.

pH-induced fluorescent active sodium alginate-based ionically conjugated and REDOX responsive multi-functional microgels for the anticancer drug delivery.

A sodium alginate (Alg) based REDOX (reduction and oxidation)-responsive and fluorescent active microgel was prepared via water in oil (w/o) mini-emulsion polymerization technique. Here, we initially synthesized sodium alginate-based disulfide cross linked microgels and after that those microgels were tagged with rhodamine amine derivative (RhB-NH2) by ionic interaction to get the pH-responsive fluorescent property. Functionalized microgels were characterized using 1H NMR, FTIR, DLS, HRTEM, FESEM, UV-vis, and fluorescence spectroscopy analyses. Presence of the REDOX-responsive disulfide-containing crosslinkers in the microgels enhances the release of doxorubicin (DOX), an anti-cancer drug in the reducing environment of the cancer-cells (simulated). Existence of the rhodamine-amine derivative in the microgels triggers the pH-dependent fluorescence property by showing fluorescence emission at 560-580 nm at pH 5.5 (cancer cell pH). The cytotoxicity of the biopolymer based microgel was assessed over both cancerous HeLa (IC50 100 µg/mL) and non-cancerous MDCK (IC50 200 µg/mL) cells by MTT assay which showed the synthesized microgel is non-toxic whereas DOX-loaded microgels showed significant toxicity. FACS and cell uptake (in vitro) analyses were conducted to understand the cell apoptosis cycle and behavior of the cancer cells in presence of the DOX-loaded microgels. This pH-responsive fluorescent active alginate-based biomaterial could be a promising material for the anti-cancer drug delivery and other medical fields.

SELEX based aptamers with diagnostic and entry inhibitor therapeutic potential for SARS-CoV-2.

Frequent mutation and variable immunological protection against vaccination is a common feature for COVID-19 pandemic. Early detection and confinement remain key to controlling further spread of infection. In response, we have developed an aptamer-based system that possesses both diagnostic and therapeutic potential towards the virus. A random aptamer library (~ 1017 molecules) was screened using systematic evolution of ligands by exponential enrichment (SELEX) and aptamer R was identified as a potent binder for the SARS-CoV-2 spike receptor binding domain (RBD) using in vitro binding assay. Using a pseudotyped viral entry assay we have shown that aptamer R specifically inhibited the entry of a SARS-CoV-2 pseudotyped virus in HEK293T-ACE2 cells but did not inhibit the entry of a Vesicular Stomatitis Virus (VSV) glycoprotein (G) pseudotyped virus, hence establishing its specificity towards SARS-CoV-2 spike protein. The antiviral potential of aptamers R and J (same central sequence as R but lacking flanked primer regions) was tested and showed 95.4% and 82.5% inhibition, respectively, against the SARS-CoV-2 virus. Finally, intermolecular interactions between the aptamers and the RBD domain were analyzed using in silico docking and molecular dynamics simulations that provided additional insight into the binding and inhibitory action of aptamers R and J.