The impact of varying dextran oxidation levels on the inhibitory activity of a bacteriocin loaded injectable hydrogel

In the design of injectable antimicrobial dextran-alginate hydrogels, the impact of dextran oxidation and its subsequent  changes in molecular weight and the incorporation of glycol chitosan on (i) gel mechanical strength and (ii) the inhibitory profle of an encapsulated bacteriocin, nisin A, are explored. As the degree of oxidation increases, the weight average  molecular mass of the dextran decreases, resulting in a reduction in elastic modulus of the gels made. Upon encapsulation  of the bacteriocin nisin into the gels, varying the dextran mass/oxidation level allowed the antimicrobial activity against  S. aureus to be controlled. Gels made with a higher molecular weight (less oxidised) dextran show a higher initial degree  of inhibition while those made with a lower molecular weight (more oxidised) dextran exhibit a more sustained inhibition.  Incorporating glycol chitosan into gels composed of dextran with higher masses signifcantly increased their storage modulus  and the gels’ initial degree of inhibition.