Antibacterial Hydrogels Derived from Poly(γ-glutamic acid) Nanofibers

Biocompatible hydrogels with antibacterial properties derived from gamma-polyglutamic acid (gamma-PGA) were prepared from bulk and electrospun nanofibers. The antibacterial drugs loaded in these hydrogels were triclosan (TCS), chlorhexidine (CHX) and polyhexamethylene biguanide (PHMB); furthermore, bacteriophages were loaded as an alternative antibacterial agent. Continuous and regular gamma-PGA nanofibers were successfully obtained by the electrospinning of trifluoroacetic acid solutions in a narrow polymer concentration range and restricted parameter values of flow rate, voltage and needle-collector distance. Hydrogels were successfully obtained by using cystamine as a crosslinking agent following previous published procedures. A closed pore structure was characteristic of bulk hydrogels, whereas an open but structurally consistent structure was found in the electrospun hydrogels. In this case, the morphology of the electrospun nanofibers was drastically modified after the crosslinking reaction, increasing their diameter and surface roughness according to the amount of the added crosslinker. The release of TCS, CHX, PHMB and bacteriophages was evaluated for the different samples, being results dependent on the hydrophobicity of the selected medium and the percentage of the added cystamine. A high efficiency of hydrogels to load bacteriophages and preserve their bactericide activity was demonstrated too.

Automated summary

Biocompatible hydrogels with antibacterial properties were prepared from gamma-polyglutamic acid (gamma-PGA). The hydrogels loaded with antibacterial drugs and bacteriophages showed efficient drug release and bactericide preservation. Continuous and regular gamma-PGA nanofibers were successfully obtained by electrospinning. The electrospun hydrogels had an open porous structure compared to bulk hydrogels.