Zwitterionic nanocapsule-based wound dressing with the function of gradient release of multi-drugs for efficient wound healing.

Efficient wound healing has attracted great interest due to the prevalence of skin damage. It is still highly desired yet challenging to construct a multi-drug loaded wound dressing that can release different drugs at different times to meet specific requirements towards different healing stages. Herein, a wound dressing was developed based on thermoresponsive zwitterionic nanocapsules (ZNs) that were sandwiched between two double-layered fabrics to regulate the multiple drug release pathway. The salt-response of the obtained ZNs was greatly suppressed while its transition temperature was regulated to be ∼37 °C to fit the needs of the physiological environment. Two bioactive substances, human basic fibroblast growth factor (bFGF) for tissue regeneration and norfloxacin for anti-inflammation, were loaded in the ZNs and on the surface of fabrics, respectively, to achieve separative gradient release. The in vitro drug release tests revealed that norfloxacin could be released relatively fast (∼24 h) while the release rate of bFGF was much slower (∼168 h), matching the specific time requirements of inflammation and proliferation stages very well. The in vivo wound healing experiment also confirmed the high wound healing efficiency of the wound dressing developed here, compared to the wound dressings without gradient release characteristics. We believe the strategy illustrated here will provide new insights into the design and biomedical applications of zwitterionic nanocapsules.