| Layer-by-layer self-assembly (LbL) technique is a simple method to assemblemultilayer films with precious control of structure and functionality. Based on thefacile preparation, tunable properties and potential biomedical applications, LbLassembled films have been widely studied for the applications to separationmembranes, sensors, biological templates, controlled drug delivery and so forth. Thefunctionality of films has immerged as one of the most interesting research topicsthese years. On the one side, the stimuli-responsive multilayer films with controlledloading and release properties could be used as ideal drug delivery systems. On theother side, the films were exposed to damage during their usage, and the mechanicaland protection properties would be decreased. Thus the multilayer films with selfhealing abilities that could extend their lifetimes, improve safety, and ensuresustainability would show their potential application.Polyurethanes (PUs) are known as one of the most popular segmented polymerswith a wide range of versatility in terms of their exceptional biocompatibility,biodegradation and versatility. Based on the above properties, PU based films wereassembled via LbL technique, and the drug delivery properties and self-healingabilities were studied.(1) LbL is a technique which has shown potential applications in drug deliverysystem for its simplicity, low cost and controllability. Here, multilayer films wereprepared via LbL technique with oppositely charged outer layer, PU andcarboxymethyl cellulose sodium (CMC) were chosen as the film components andmethylene blue (MB) was used as a model drug to investigate the loading and releasecharacteristics of the prepared PU/CMC multilayer films. The effect of pH values andionic strength were also studied in detail. The results indicated that pH values andionic strength would influence the loading and release properties of multilayer films. Italso suggested that the PU/CMC multilayer films demonstrated fine reversible property which would show the potential application in drug delivery system.(2) Here described a new design route to fabricate self-healing biocompatiblefilms. We found that LbL assembled PU/CMC multilayer films exhibited limiteddefects healing abilities. After precoating slides with poly(diallyldimethylammoniumchloride)(PDDA), the assembled PDDA(CMC/PU)nfilms showed enhancedsaline-enabled self-healing ability, and could autonomically repair cuts of several tensof micrometers wide in several seconds. It suggests that the healing ability of certainfilms could be largely enhanced by introducing a third polyelectrolyte as innermostlayer, and also significantly affected by the flowability of the polymer of outmost layer.The result shows promise for application as protective films with self-healingproperties under the physiological environment. We expect that our finding will serveas a helpful template for others to design new coating of implanted organs.(3) In our previous study, PU based multilayer films assembled with weakpolyelectrolytes exhibited controllable loading and release properties, but would bedecomposed in high salt solution. Herein, a strong polyelectrolyte, poly(styrenesulfonic acid) sodium (PSS), was introduced to fabricate multilayer films. The salttolerance of the film was investigated by evaluating the loading and release profilestowards model drug in salt solution with different concentrations. Results showed thatthe release behavior of the film, as well as its loading capacity, can be tuned byvarying the salt concentrations. And the film showed a good salt tolerance that canremain integrity even after6cycles of drug loading and release in600mM NaClsolution. The PU/PSS multilayer film would be an ideal candidate for controlled drugdelivery formulations, especially in some special tissues or organs (like kidney) withhigh salt concentration for sustained drug release. This work provided a new methodfor fabricating salt tolerant drug delivery system. |
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