Norbornene-chitosan spray-dried microspheres for peptide conjugation using thiol-ene “photoclick” chemistry

The action of bioactive peptides, such as antimicrobial peptides (AMP), in the human body is often compromised by limited residence time and stability in the target site. Bioconjugation of peptides to biomaterial surfaces is one of the strategies that may overcome these limitations. Herein, norbornene-chitosan (NorChit) microspheres were engineered to react with thiolated peptides by thiol- ene “photoclick” chemistry. NorChit microspheres were produced by spray drying and crosslinked with dithiothreitol (DTT) to prevent their solubilization. Microspheres with a diameter of 5 ± 2 μm showed round and smooth morphology with pockets over the surface that could be related with hydrophobic interactions between internal norbornene groups. Thiol-ene bioconjugation carried out using a fluorescent model peptide, showed a yield of 45%, whereas using the peptide but without UV exposure indicated a maximum of peptide adsorption of 30%. Altogether, NorChit microspheres show the potential for carrying bioactive peptides, which may open avenues for AMP activity onto harsh environments in the body.