Synthesis and biological activity of a potent optically pure autoinducer-2 quorum sensing agonist.

Quorum sensing (QS) regulates population-dependent bacterial behaviours, such as toxin production, biofilm formation and virulence. Autoinducer-2 (AI-2) is to date the only signalling molecule known to foster inter-species bacterial communication across distantly related bacterial species. In this work, the synthesis of pure enantiomers of C4-propoxy-HPD and C4-ethoxy-HPD, known AI-2 analogues, has been developed. The optimised synthesis is efficient, reproducible and short. The (4S) enantiomer of C4-propoxy-HPD was the most active compound being approximately twice as efficient as (4S)-DPD and ten-times more potent than the (4R) enantiomer. Additionally, the specificity of this analogue to bacteria with LuxP receptors makes it a good candidate for clinical applications, because it is not susceptible to scavenging by LsrB-containing bacteria that degrade the natural AI-2. All in all, this study provides a new brief and effective synthesis of isomerically pure analogues for QS modulation that include the most active AI-2 agonist described so far.

Synthesis and functionalization of CdSe/ZnS QDs using the successive ion layer adsorption reaction and mercaptopropionic acid phase transfer methods.

Detailed protocols for the preparation of CdSe nanocrystals coated with a multishell structure of ZnS and their surface modification based on the successive ion layer adsorption and reaction method are described. The first phase of the synthesis produces a hydrophobic surface consisting of a TOPO/HDA ligand mixture. This is followed by a surface modification of the quantum dots (QDs) with 3-mercaptopropionic acid by the phase transfer method. The modified QDs become soluble in aqueous systems such as water or buffers for further biological applications.

Evaluation of cytotoxicity of 3-mercaptopropionic acid-modified quantum dots on Medicago sativa cells and tissues.

Like most of the new technologies designed to interact with biological systems, the applications of -nanomaterials needs a proper assessment for their potential impacts. It is only through addressing the issues raised by toxicological studies that nanotechnology will be able to acquire its full potential. Here, we describe the detailed protocols to study the responses of plant cells to their exposure to nanoparticles, including viability, oxidative stress detection, and reactive oxygen species enzymatic detoxification, as well as particle uptake.