Minimizing the negative charge of Alginate facilitates the delivery of negatively charged molecules inside cells

Alginate is a negatively charged, biocompatible polysaccharide obtained naturally. The presence of deprotonated carboxylic groups imparts a negative charge on Alginate which hinders its interaction with other negatively charged molecules including the cell membrane. Despite this challenge, Alginate presents several advantages as it is structurally similar to the extracellular matrices of living tissues and is FDA approved for oral consumption. Motivated by this, we contemplated the utilization of amine grafted Alginate (Alginate+) as a transfection agent for negatively charged molecules like DNA, protein and siRNA. The net negative charge of Alginate was reduced by the reaction with epichlorohydrin and ammonia which lead to grafting of an amine group. Alginate+ was characterized by zetasizer, proton nuclear magnetic resonance, fourier transform infrared spectroscopy, and liquid-chromatography mass spectrometry, followed by visualization under scanning electron microscope. Different concentrations of Alginate+ were assessed for its loading capacity by agarose gel electrophoresis and DNA retardation assay. Further, in-vitro and in-vivo transfection studies suggested that the Alginate+ particles could successfully transfect mammalian cells carrying negatively charged peptides, siRNAs, and DNA (plasmid); furthermore in BALB/c mice significant expression of transfected plasmid was observed in various organs. The probable mode of cell entry and toxicity were predicted through in-silico studies. Finally, the biodegradation of Alginate+ was evaluated in human serum with the addition of ascorbic acid and sodium citrate. Overall, this study provides an easy fabrication method to turn Alginate into an effective delivery carrier with additional properties such as, degradability and reduced toxicity.

Automated summary

This study investigates the use of amine grafted Alginate (Alginate+) as a transfection agent for negatively charged molecules. The results show that Alginate+ particles can successfully transfect mammalian cells carrying negatively charged molecules, and in vivo studies demonstrate significant expression of transfected plasmid in various organs of mice. In addition, in-silico studies predict the mode of cell entry and toxicity, while biodegradation of Alginate+ is evaluated in human serum. Overall, this study provides a simple method to fabricate an effective delivery carrier with added properties such as degradability and reduced toxicity.