Combined Effect of\nthe Core–Shell Structure\nand Variable Wettability in Polymer Fiber Membranes for Dual and Delayed\nRelease of Active Agents

Developing polymeric membranes capable\nof modulating\nthe release\nof compounds by controlling their surface properties and structure\nrepresents an important challenge for efficient drug and active agent\ndelivery systems. Herein, we combine the two properties of polymeric\nfibers, on the one hand, the core–shell structure and, on the\nother hand, the control of wettability, to manufacture polymeric membranes\nwith dual and delayed release capacity of active agents. Fibers consisted\nof a shell of derivates of poly(styrene-<i>co</i>-maleic\nanhydride) functionalized with amino acids of different hydropathic\nindexes and loaded with silver nanoparticles and a core of poly(vinyl\nalcohol) containing allantoin, both used as antibacterial and healing\nactive agent, respectively. Silver ion release profiles were characterized\nby two regimes that were reminiscent of the core–shell structure\nof the fibers. An initial lag phase governed by diffusion was followed\nby a higher release rate driven by a diffusion front of allantoin\nfrom the center of the fiber until it reached the external environment.\nThe allantoin release profiles were well-fit by a first-order model,\nwhere the saturation value was related to the wettability of the membranes.\nOur results show how the control of wettability and the core–shell\nconfiguration of the fibers may be a strategy for creating a versatile\npolymeric platform for a fine-tuned release of active agents for biomedical\napplications.