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Up to date, tissue regeneration of large bone defects is a clinical challenge under exhaustive study. Nowadays, the most common clinical solutions concerning bone regeneration involve systems based on human or bovine tissues, which suffer from drawbacks like antigenicity, complex processing, low osteoinductivity, rapid resorption and minimal acceleration of tissue regeneration. This work thus addresses the development of nanofibrous synthetic scaffolds of polycaprolactone (PCL)-a long-term degradation polyester-compounded with hydroxyapatite (HA) and variable concentrations of ZnO as alternative solutions for accelerated bone tissue regeneration in applications requiring mid-and long-term resorption. In vitro cell response of human fetal osteoblasts as well as antibacterial activity against Staphylococcus aureus of PCL:HA:ZnO and PCL:ZnO scaffolds were here evaluated. Furthermore, the effect of ZnO nanostructures at different concentrations on in vitro degradation of PCL electrospun scaffolds was analyzed. The results proved that higher concentrations ZnO may induce early mineralization, as indicated by high alkaline phosphatase activity levels, cell proliferation assays and positive Alizarin-RedS stained calcium deposits. Moreover, all PCL:ZnO scaffolds particularly showed antibacterial activity against S. aureus which may be attributed to release of Zn 2+ ions. Additionally, results here obtained showed a variable PCL degradation rate as a function of ZnO concentration. Therefore, this work suggests that our PCL:ZnO scaffolds may be promising and competitive short-, mid-and long-term resorption systems against current clinical solutions for bone tissue regeneration.

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Control and reduction of microorganism infections in high-risk environments is up to date a challenge. Traditional techniques imply several limitations including development of antibiotics resistance and ecotoxicity. Then, polymers functionalized with photocatalyts arise as a promising solution against a broad spectrum of microorganisms found at, e.g. sanitary, food, and medical environments. Here, we present silicone rubber–TiO2 composites as novel antibacterial polymers. Four different types of composites with different TiO2 contents were produced and analyzed under UV irradiation and dark conditions in terms of particle distribution, chemical composition, photocatalytic activity, wettability, and antibacterial efficacy against Escherichia coli. Under UV irradiation, antibacterial sensitivity assay showed a 1000 times reduction of colony forming units after 2 h of light exposure so that the antibacterial ability of silicone–TiO2 composites was proved. Photocatalytic activity assessment suggested that reactive oxygen species induced by photocatalytic reaction at TiO2 particles are the main cause of the observed antibacterial effect. Scanning electron microscopy indicated no topographical damage after UV exposure. In addition, chemical analysis through Raman and X-Ray photoelectron spectroscopies demonstrated the stability of the silicone matrix under UV irradiation. Hence, the current work presents silicone–TiO2 composites as stable nonspecific antibacterial polymers for prevention of infections at multiple high-risk environments.

Encapsulation of bioactive molecules within polymeric particles is a challenge because of several limitations, including low drug-loading efficiency, unwanted release profile, polydispersity and batch-to-batch variation in reproducibility, along with the limitations of scaling up the process. It is essential to control the morphology of pure polymer particles in the first instance, in order to obtain the desired release profile of drugs from the particles during a later stage. Here we report the preparation of electrosprayed particles from a water-soluble US Food and Drug Administration-recognized polymer, namely poly(vinyl alcohol) (PVA), as an approach towards a short-term drug delivery vehicle. Through electrospraying and varying the solvent ratios, three different sizes of particles were prepared, with sizes ranging from 500 to 2000 nm. Insulin was chosen as a model bioactive molecule, and the release profile of the drug was studied after its incorporation in the PVA particles. Fractional release plots obtained showed short-term release of insulin within the first 60 min. Release curves were analyzed according to the Ritger-Peppas model, suggesting Fickian diffusion as the predominant insulin release mechanism from the PVA particles. This work suggests electrosprayed PVA particles as an innovative drug delivery system for short-term administration of drugs.

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