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So far, poly(L-lactic acid), PLLA nanosheets proved to be promising for wound healing. Such biodegradable materials are easy to prepare, bio-friendly, cost-effective, simple to apply and were shown to protect burn wounds and facilitate their healing. At the same time, certain metal ions are known to be essential for wound healing, which is why this study was motivated by the idea of incorporating PLLA nanosheets with Zn2+ ion containing nanoparticles. Upon being applied on wound, such polymer nanosheets should release Zn2+ ions, which is expected to improve wound healing. The work thus focused on preparing PLLA nanosheets embedded with several kinds of Zn-containing nanoparticles, their characterization and ion-release behavior. ZnCl2 and ZnO nanoparticles were chosen because of their different solubility in water, with the intention to see the dynamics of their Zn2+ ion release in liquid medium with pH around 7.4. Interestingly, the prepared PLLA nanosheets demonstrated quit similar ion release rates, reaching the maximum concentration after about 10 h. This finding implies that such polymer materials can be promising as they are expected to release ions within several hours after their application on skin. [ABSTRACT FROM AUTHOR]

• Nanoparticles of ZnO encapsulated by graphene oxide were prepared by laser ablation in water. • Simple green synthesis method uses only Zn and graphite targets and water. • GO thickness in GO@ZnO nanoparticles was tuned via ablation time. • ZnO surface with O and OH groups acts as nuclei for the growth of GO layer. Core-shell nanoparticles (NPs) have attracted tremendous attention due to their tunable properties and numerous potential applications. However, preparation of uniform and size-controlled core-shell nanomaterials of ZnO with graphene oxide (GO) is still considered as a challenging task even after years of research. In this work, we report on a facile one-pot organics-free method for preparation of GO-wrapped ZnO NPs. Laser ablation of zinc and carbon targets in water medium at ambient atmosphere resulted in formation of spherical ZnO core and GO shell, respectively. According to Raman active modes, the GO shell was layered and the ZnO core was polycrystalline. Both Raman spectra and X-ray diffraction patterns revealed that formation of layered GO increased stress inside the ZnO core. Surface layers reduced the density of defects and disorders in the ZnO crystal lattice and enhanced the phonon lifetime. Also, the minimal interfacial disorder between the layered GO and ZnO core resulted in continuous formation of a GO layer. Thus, laser ablation in liquid is demonstrated to provide stable and uniform core-shell GO@ZnO NPs with controlled GO layer that can find applications in biomedical and sensing fields. [ABSTRACT FROM AUTHOR]

The ζ‐potential and hydrodynamic size (dh) of nanoparticles (NPs) are systematically controlled by capping gold NPs (AuNPs) with polymers having different charges and treating them in NaCl solutions of diverse concentrations. Interactions between AuNPs in hydrogel are caused by chemical reactions induced by 1,4‐dithiothreitol. The effect of ζ‐potential is clear, as negatively charged AuNPs can be aggregated in neutral agarose gel, but the amount of aggregation is significantly affected by the magnitude of the negative surface charge on the AuNPs. However, all positively charged AuNPs show negligible aggregation in agarose gel with slightly negative polarity. The effect of dh on AuNP aggregation is different from that of ζ‐potential. Although AuNPs with small dh generally show more aggregation than those with large dh, the amount of AuNP capping layer is critical. Thus, the amount of polymer present on NP surface needs to be considered to investigate the effect of dh on AuNP aggregation. Through extended Derjaguin, Landau, Verwey, Overbeek (XDLVO) theory, it is shown that the charges of the AuNPs and the hydrogel, as well as the dh of the NPs, are related to electrostatic repulsion and steric hindrance, which affect AuNP aggregation in hydrogel. Chemical interaction of nanoparticles in hydrogel is significantly affected by their ζ‐potential and hydrodynamic size. The charges of nanoparticles and the hydrogel and the hydrodynamic size of the nanoparticles affect the interaction of nanoparticles in hydrogel via electrostatic repulsion and steric hindrance occurring between them. [ABSTRACT FROM AUTHOR]