Abstract
Dextran esters of different amino acids (glycine, -alanine, L-ornithine, L-lysine) are investigated regarding their pKa values by potentiometric titration. The pKa values of the dextran derivatives are generally dependent on the position of the amino group in relation to the ester group, i.e. the nearer they are located in the molecule, the lower the resulting pKa values are, L-ornithine ester being the exception. An influence of the polymer backbone is ruled out. Stability against hydrolysis at different pH values and over longer periods at constant pH value is measured by potentiometric and polyelectrolyte titration. The -alanine ester shows slowest hydrolysis at alkaline pH values, starting at a pH value of 8. The esters investigated are polycations at physiological pH values; thus, the charging properties are essential for using these esters as nonviral vectors in gene delivery.
Highlights
Because of their potential usefulness, polycations bearing a polysaccharide backbone have gained great interest
Dextran L-lysine ester (DLE) c(AA) [mmol/g] 2.71 2.62 2.59 2.47 2.25 2.09 2.46 ± 0.24 1.84 0.06 0 0 groups of these dextran esters were determined. They appear to be independent of the polymer backbone, as comparison with methyl esters showed
At physiological pH values, the dextran esters are not fully protonated, the highest value being found for the dextran β -alanine ester
Summary
Because of their potential usefulness, polycations bearing a polysaccharide backbone have gained great interest. Apart from naturally occurring polycations like chitosan that may be applied in various fields (e.g., in wastewater treatment [1] and as coantibiotics [2]), interest lies in chemically modified polysaccharides, like cationic cellulose [3], starch [4], and dextran derivatives. Polycationic dextran derivatives have gained great interest in the field of gene delivery [5,6] due to the low toxicity and high biodegradability of dextran [7]. Polycations, suited for gene delivery, must form stable polyplexes with the polyanionic biopolymer DNA. The polyplex dissolves and the DNA can enter the cell nucleus, where transfection takes places. The polycation unloaded should be nontoxic and digested by the cell
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
