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Survival of microorganisms depends to a large extent on environmental conditions and the occupied host. By adopting specific strategies, microorganisms can thrive in the surrounding environment and, at the same time, preserve their viability. Evading the host defenses requires several mechanisms compatible with the host survival which include the production of RNA thermometers to regulate the expression of genes responsible for heat or cold shock as well as of those involved in virulence. Microorganisms have developed a variety of molecules in response to the environmental changes in temperature and even more specifically to the host they invade. Among all, RNA-based regulatory mechanisms are the most common ones, highlighting the importance of such molecules in gene expression control and novel drug development by suitable structure-based alterations. This article is categorized under: RNA Structure and DynamicsRNA Structure, Dynamics and Chemistry RNA in Disease and DevelopmentRNA in Disease RNA Structure and DynamicsInfluence of RNA Structure in Biological Systems.

The contamination of food and potable water with microorganisms may cause food-borne and water-borne diseases. The common contaminants include Escherichia coli (E. coli), Salmonella sp. etc. The conventional methods for monitoring the water quality for the presence of bacterial contaminants are time-consuming, expensive, and not suitable for rapid on-spot detection in field conditions. In the current study, super paramagnetic iron oxide nanoparticles (SPIONs) were synthesized and conjugated with E. coli specific Aptamer I to detect E. coli cells qualitatively as well as quantitatively. The sludge consisting of E. coli- SPION complex was separated via magnetic separation. The presence of E. coli cells was confirmed with the help of standard techniques and confocal laser scanning microscopy (CLSM) employing Aptamer II conjugated CdTe-MPA quantum dots (QDs). Finally, an ATmega 328P prototype biosensor based on Aptamer II conjugated CdTe MPA QDs exhibited quantitative and qualitative abilities to detect E.coli. This prototype biosensor can even detect low bacterial counts (up to 1 × 10

The present study is focused on a simple execution in the applicability of non-toxic lower generation poly amidoamine (PAMAM) dendrimers as effective nano-vectors in targeted gene delivery to the skin. So far the first three lower generation (G1, G2 and G3) PAMAM dendrimers have been overlooked as nucleic acid therapeutics. In this study, we have first carried out a systematic biophysical analysis to analyze their ability for plasmid DNA (pDNA) condensation and subsequent release by ethidium bromide assay to optimize dendrimer to DNA charge ratio for effective pDNA condensation and release. Interestingly, stopped flow fluorescence spectroscopic analysis on pDNA-dendrimer binding kinetics revealed the efficiency of generations G2 and G3 in pDNA condensation in comparison with G1 through four steps. Importantly, it validates aggregation and association of the dendrimer in the vicinity of pDNA. Based on these understanding, successful in vitro cellular uptake of dendriplexes followed by their transfection into CHO−K1 cells was demonstrated at the charge ratio Z+/- 5 and 10. The interesting observations of gene transfection with CHO−K1 cells were extended to HaCaT cell line and efficient pDNA transfections were evidenced with negligible cytotoxicity. In addition to this, the stability of the dendriplexes at the charge ratio Z+/- 5 for G3 and Z+/- 10 for G2 was found even upto 50 % serum concentration suggesting possible future applicability in in vivo. Overall, the current approach promises the use of lower generation dendrimers for pDNA delivery to the skin using only electrostatic nanocomplex formation without any covalent linkage.

Considering the importance of short oligonucleotide packing in dendriplex-mediated gene delivery, a direct insight into the 14-mer oligonucleotide and dendrimer interactions using fluorescence and FRET techniques is the focus of this study. Fluorometric titrations of various fluorophore-tagged oligonucleotides with the first three PAMAM dendrimer generations showed a decrease in the fluorescence intensity with two break points, namely Z1± and Z2±, for each titration. The first break point for each dendrimer was identical to the neutralization point observed by basic biophysical studies for the corresponding dendrimer generations. Additionally, FRET studies on dual tagged oligonucleotide (DFT) molecules revealed a third break point at the charge ratio (Z3±) where there was the highest fluorescence energy transfer from the donor to the acceptor fluorophores. Altogether, dendriplex formation was considered to take place via three steps with an increase in the dendrimer concentration, where initially there was monomeric complexation at the neutralization point (Z1±) followed by loosely held molecular aggregation of the dendrimer (Z2±). In the final step, dendrimer molecular aggregates were held tightly together for the closest possible packing of the oligonucleotide molecules onto their surface. The effective molecular packing is identified by the highest FRET intensity for the dendrimer of generation 2 at a charge ratio of 0.34 (Z±).