RESUMO
Hydrogels are perfectly suited to support cell and tissue growth in advanced tissue engineering applications as well as classical wound treatment scenarios. Ideal hydrogel materials for these applications should be easy to produce, biocompatible, resorbable and antimicrobial. Here we report the fabrication of degradable covalent antimicrobial lysine and tryptophan containing copolypeptide hydrogels, whereby the hydrogel properties can be independently modulated by the copolypeptide monomer ratio and chiral composition. Well-defined statistical copolypeptides comprising different overall molecular weights as well as ratios of l- and d-lysine and tryptophan at ratios of 35 : 15, 70 : 30 and 80 : 20 were obtained by N-carboxyanhydride (NCA) polymerisation and subsequently crosslinked by the selective reaction of bifunctional triazolinedione (TAD) with tryptophan. Real-time rheology was used to monitor the crosslinking reaction recording the fastest increase and overall modulus for copolypeptides with the higher tryptophan ratio. Water uptake of cylindrical hydrogel samples was dependent on crosslinking ratio but found independent of chiral composition, while enzymatic degradation proceeded significantly faster for samples containing more l-amino acids. Antimicrobial activity on a range of hydrogels containing different polypeptide chain lengths, lysine/tryptophan composition and l/d enantiomers was tested against reference laboratory strains of Gram-negative Escherichia coli (E. coli; ATCC25922) and Gram-positive, Staphylococcus aureus (S. aureus; ATCC25923). log reductions of 2.8-3.4 were recorded for the most potent hydrogels. In vitro leachable cytotoxicity tests confirmed non-cytotoxicity as per ISO guidelines.
Assuntos
Antibacterianos/farmacologia , Materiais Biocompatíveis/farmacologia , Reagentes de Ligações Cruzadas/farmacologia , Hidrogéis/farmacologia , Peptídeos/farmacologia , Triazóis/farmacologia , Antibacterianos/química , Antibacterianos/metabolismo , Materiais Biocompatíveis/química , Materiais Biocompatíveis/metabolismo , Reagentes de Ligações Cruzadas/química , Reagentes de Ligações Cruzadas/metabolismo , Escherichia coli/efeitos dos fármacos , Humanos , Hidrogéis/química , Hidrogéis/metabolismo , Testes de Sensibilidade Microbiana , Peptídeos/química , Peptídeos/metabolismo , Staphylococcus aureus/efeitos dos fármacos , Triazóis/química , Triazóis/metabolismoRESUMO
Crosslinking of an unsaturated aliphatic polyester poly(globalide) (PGl) by bistriazolinediones (bisTADs) is reported. First, a monofunctional model compound, phenyl-TAD (PTAD), was tested for PGl functionalisation. 1H-NMR showed that PTAD-ene reaction was highly efficient with conversions up to 97%. Subsequently, hexamethylene bisTAD (HM-bisTAD) and methylene diphenyl bisTAD (MDP-bisTAD) were used to crosslink electrospun PGl fibres via one- and two-step approaches. In the one-step approach, PGl fibres were collected in a bisTAD solution for in situ crosslinking, which resulted in incomplete crosslinking. In the two-step approach, a light crosslinking of fibres was first achieved in a PGl non-solvent. Subsequent incubation in a fibre swelling bisTAD solution resulted in fully amorphous crosslinked fibres. SEM analysis revealed that the fibres' morphology was uncompromised by the crosslinking. A significant increase of tensile strength from 0.3 ± 0.08 MPa to 2.7 ± 0.8 MPa and 3.9 ± 0.5 MPa was observed when PGI fibres were crosslinked by HM-bisTAD and MDP-bisTAD, respectively. The reported methodology allows the design of electrospun fibres from biocompatible polyesters and the modulation of their mechanical and thermal properties. It also opens future opportunities for drug delivery applications by selected drug loading.