In this study, we report the development of a hyaluronic acid (HA)-based composite hydrogel containing calcium fluoride (CaF2) with good biocompatibility and antibacterial properties for multifunctional wound dressing applications. CaF2 was newly selected for incorporation within HA because it can release both Ca2+ and F– ions, which are well-known ions for affecting cell proliferation and inhibiting bacterial growth, respectively. In particular, an in situ precipitation process enables easy control over the released amount of F– ions by simply adjusting the precursor solutions (calcium chloride (CaCl2) and ammonium fluoride (NH4F)) used for the CaF2 precipitation. CaF2 particles were uniformly embedded within a HA-based pure hydrogel using an in situ precipitation process. Through variation of the CaCl2 and NH4F concentrations used in the precipitation as well as the precipitation time, composite hydrogels with different ion-release profiles were obtained. By controlling the precipitation time, especially for 10 min and after 30 min, large differences in the ion-release profiles as a function of CaF2 concentration were observed. A shorter precipitation time resulted in faster release of fluoride, whereas for the 30 min and 1 h samples, sustained ion release was achieved. Colony tests and live/dead assays using Escherichia coli and Staphylococcus aureus revealed a lower density of bacteria on the CaF2 composite hydrogels than on the pure hydrogel for both strains. In addition, improved cellular responses such as cell attachment and proliferation were also observed for the CaF2 composite hydrogels compared to those for the pure hydrogel. Furthermore, the composite hydrogels exhibited excellent wound healing efficiency, as evidenced by an in vitro cell migration assay. Finally, monitoring of the wound closure changes using a full-thickness wound in a rat model revealed the accelerated wound healing capability of the CaF2 composite hydrogels compared with that of the pure hydrogel. Based on our findings, these CaF2 composite hydrogels show great potential for application as advanced hydrogel wound dressings with antibacterial properties and accelerated wound-healing capabilities.

No abstract

In the present study, we examine the thermal stability of TiO2-x (TiO) and Nb:TiO2-x (TNO) films at different exposing temperatures for the as-deposited and oxygen-atmosphere annealed samples. In order to attain the good thermal stability characteristics, lower resistance of the TiO and TNO samples were annealed in oxygen gas atmosphere at a high flow rate (5 lit/min) of oxygen gas and annealing time (25 min). From the structural studies, it can be confirmed that the annealing process gives the incorporation of oxygen atoms to its vacant sites and the phase transition improvement from the amorphous to rutile structure. The annealed samples reveal the high resistivity and temperature coefficient of resistance (TCR) values than as-deposited samples. Furthermore, it was confirmed that the annealed samples exhibits a significant improvement of thermal stability compared to the as-deposited samples. As a result, the annealed TNO sample exhibits outstanding thermal stability as well as better bolometric performance. Consequently, this study reveals that the annealed TNO sample is appropriate for shutter-less infrared image sensor devices.