Dual stimuli-responsive polyurethane-based hydrogels as smart drug delivery carriers for the advanced treatment of chronic skin wounds

The design of multi-stimuli-responsive vehicles for the controlled and localized release of drugs is a challenging issue increasingly catching the attention of many research groups working on the advanced treatment of hard-to-close wounds.In this work,a thermo-and pH-responsive hydrogel(P-CHP407)was prepared from an ad hoc synthesized amphiphilic poly(ether urethane)(CHP407)exposing a significant amount of-COOH groups(8.8±0.9 nmol/g_(polymer)).The exposure of acid moieties in P-CHP407 hydrogel led to slightly lower initial gelation temperature(12.1◦C vs.14.6◦C,respectively)and gelation rate than CHP407 hydrogel,as rheologically assessed.Nanoscale hydrogel characterization by Low Field NMR(LF-NMR)spectroscopy suggested that the presence of carboxylic groups in P-CHP407 caused the formation of bigger micelles with a thicker hydrated shell than CHP407 hydrogels,as further proved by Dynamic Light Scattering analyses.In addition,P-CHP407 hydrogel showed improved capability to change its internal pH compared to CHP407 one when incubated with an alkaline buffer(pH 8)(e.g.,pH_(change_5min)=3.76 and 1.32,respectively).Moreover,LF-NMR characterization suggested a stronger alkaline-pH-induced interaction of water molecules with micelles exposing-COOH groups.Lastly,the hydrogels were found biocompatible according to ISO 10993 and able to load and release Ibuprofen:delivery kinetics of Ibuprofen was enhanced by P-CHP407 hydrogels at alkaline pH,suggesting their potential use as smart delivery systems in the treatment of chronic infected wounds.

Custom-design of intrinsically antimicrobial polyurethane hydrogels as multifunctional injectable delivery systems for mini-invasive wound treatment

Effective management of hard-to-close skin wounds is a challenging issue due to several co-morbidities in affected patients.Particularly,infections represent a major obstacle in wound healing.The design of efficient wound treatments thus represents an urgent need.Injectable drug delivery hydrogels with intrinsic antimicrobial and antifungal properties were herein designed for perspective application in the mini-invasive treatment of hard-to-close wounds.First,an amphiphilic polyurethane was synthesized from Poloxamer■407 macrodiol and N-Boc diethanolamine chain extender(DHP407,M_(w)=33 kDa).Chain-extension reaction step was optimized to maximize the formation of-NH groups along the polymer chains(4.5×10^(20)±1.8×10^(19)-NH groups/g polymer),after Boc-caging group removal(D-DHP407).DHP407 and D-DHP407 water-based solutions were thermosensitive with slightly different Critical Micellar Concentration(17.5μg/mL vs.19.7μg/mL)and cluster hydrodynamic diameter(235.6±19.9 nm vs.260.1±20.5 nm),and similar Critical Micellar Temperature(22.5℃ vs.23.1℃).A polyurethane solution concentration(15%w/V)was selected by tube-inverting test and rheological analysis showing injectability,as evidenced by sol-to-gel transition at 27.7±0.6℃ for DHP407 and 29.7±0.6℃ for D-DHP407,within few minutes,at similar gelation kinetics.DHP407 and D-DHP407 hydrogels showed controlled release of Bovine Serum Albumin(BSA)model protein(1 mg/mL),with no burst phenomena.BSA released from DHP407 and D-DHP407 hydrogels at 24 h was 33.7±5.0% and 24.6±1.2%,respectively.D-DHP407 hydrogel was biocompatible and able to support NIH-3T3 cell proliferation.Furthermore,D-DHP407 hydrogel showed intrinsic antifungal and antibacterial activity against C.albicans and Gram-positive S.aureus and Gram-negative E.coli bacteria,injectability and capability to retain shape post-injection,making it promising for future use in the management of hard-to-close skin wounds.