Bioinspired Water-soluble Polymers with Grafted Polyamine Chains: Synthesis and Complexation with Oligonucleotides

Acrylamide derivatives: A dynamic nuclear magnetic resonance study

Substituted acrylamides have found an extensive application in organic and medical chemistry; therefore, it is very important to get insight into their features such as electronic structure, spectral properties, and stereochemical transformations. A correct interpretation of the chemical behavior and biological activity of these heteroatomic systems is impossible without knowledge of the structure of stereodynamic forms and factors determining their relative stability. The structure and peculiarities of stereodynamic behavior of substituted acrylamides and their model compounds were studied by dynamic and multinuclear ¹ H, ¹³ C, and ¹⁵ N nuclear magnetic resonance (NMR) spectroscopy in CDCl₃ and DMSO-d₆ solution. It has been established that acrylamides in solution are realized as Z- and E-isomers, with the E-rotamer being somewhat predominant. The obtained experimental values of the free activation energy of rotamers vary within 15-17 kcal/mol, depending on the stereochemical structure of the molecule. ¹⁵ N NMR spectroscopy is the most reliable and fastest method for determining the structural and stereochemical features of nitrogen-containing compounds.

Single-step dynamic dewatering of microalgae from dilute suspensions using flocculant assisted filtration

Background

Dewatering constitutes a major challenge to the production of microalgae, accounting for 20–30% of the product cost. This presents a setback for the applicability of microalgae in the development of several sustainable products. This study presents an investigation into the dynamic dewatering of microalgae in a combined flocculation-filtration process. The effect of process conditions on the performance of 12 flocculants and their mixtures was assessed.

Results

The mechanism of flocculation via the electrostatic path was dominated by charge neutralization and subsequently followed bridging in a ‘sweep flocculation’ process. Cationic polyacrylamide (CPAM) based flocculants recorded the highest biomass retention with PAM1 and PAM2 attaining 99 and 98% retention with flocculant dosages of 10 and 15 mg/L respectively. Polyvinylamine (PVAM) was also found to improve system stability across the pH range 4–10. Alum was observed to be only effective in charge neutralization, bringing the system close to its isoelectric point (IEP). Chemometric analysis using the multi-criteria decision methods, PROMETHEE and GAIA, was applied to provide a sequential performance ranking based on the net outranking flow (ф) from 207 observations. A graphical exploration of the flocculant performance pattern, grouping the observations into clusters in relation to the decision axis (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pi$$\end{document}π), which indicated the weighted resultant of most favorable performance for all criteria was explored.

Conclusion

CPAM based flocculants and their mixtures demonstrated superior performance due to their viscoelastic behaviour under turbulence. The use of PVAM or alum in mixtures with CPAM reduced the required doses of both flocculants, which will provide beneficial financial impact for largescale microalgae dewatering in a flocculant assisted dynamic filtration process. Chemometric analysis based on the physico-chemical properties of the system provides a time saving assessment of performance across several criteria. The study findings provide an important foundation for flocculant assisted dynamic filtration processes.

Grafting multi-maleimides on antisense oligonucleotide to enhance its cellular uptake and gene silencing capability

A multitude of maleimides are grafted onto the backbone of a phosphorothioate antisense oligonucleotide (ASO) to generate the construct of maleimide-grafted ASO (Mal-g-ASO). Through click conjugation with cell membrane thiols that triggers endocytosis-independent cellular internalization, Mal-g-ASO exhibited enhanced cellular uptake efficiency, resulting in a remarkable improvement of ASO-based gene silencing.

Design of Oligonucleotide Carriers: Importance of Polyamine Chain Length

Amine containing polymers are extensively studied as special carriers for short-chain RNA (13⁻25 nucleotides), which are applied as gene silencing agents in gene therapy of various diseases including cancer. Elaboration of the oligonucleotide carriers requires knowledge about peculiarities of the oligonucleotide⁻polymeric amine interaction. The critical length of the interacting chains is an important parameter which allows us to design sophisticated constructions containing oligonucleotide binding segments, solubilizing, protective and aiming parts. We studied interactions of (TCAG)n, n = 1⁻6 DNA oligonucleotides with polyethylenimine and poly(N-(3-((3-(dimethylamino)propyl)(methyl)amino)propyl)-N-methylacrylamide). The critical length for oligonucleotides in interaction with polymeric amines is 8⁻12 units and complexation at these length can be accompanied by "all-or-nothing" effects. New dimethylacrylamide based polymers with grafted polyamine chains were obtained and studied in complexation with DNA and RNA oligonucleotides. The most effective interaction and transfection activity into A549 cancer cells and silencing efficiency against vascular endothelial growth factor (VEGF) was found for a sample with average number of nitrogens in polyamine chain equal to 27, i.e., for a sample in which all grafted chains are longer than the critical length for polymeric amine⁻oligonucleotide complexation.