Drug stability and sustained release issues are important areas in drug-delivery research. The sustained release of proteins can be achieved by their encapsulation with a hydrophobic polymer, but this requires the proteins to be protected from the harsh processing environments of organic solvents and mechanical force. Preencapsulation with poly(vinyl alcohol) (PVA) using a freeze/thaw method has been shown to allow successful protection and sustained release. This study examined the effects of freezing/thawing on PVA encapsulation in the preparation of PVA-PLGA composite particles. Freezing/thawing slightly improved the crystalline peaks and the heat of fusion of PVA, but more distinct differences were observed when the properties of the surface layers were probed by AFM. The hardness of particles' surfaces increased with increasing number of freezing/thawing cycles, whereas the adhesion force with an AFM cantilever tip decreased. The mean particle size and entrapment efficiency decreased. These results suggest that surface hardening is the major mechanism responsible for the sustained release characteristics.
Background: College students are known to struggle with a number of difficulties, such as their future careers and interpersonal relationships, as well as job-seeking stress. This study aimed to develop and test a structural model for undergraduate student college adjustment. Methods: The data collection period ranged from November 2019 to January 2020. A questionnaire was distributed to a total of 300 college students; a total of 290 copies were ultimately used for analysis. Result: The model fit indexes of the final model were χ2 = 427.707 (p < 0.001), DF = 173, χ2/DF = 2.47, GFI = 0.88, Adjusted Goodness of Fit Index (AGFI) = 0.84, Comparative Fit Index (CFI) = 0.91, Incremental Fit Index (IFI) = 0.92, Standardized Root Mean-square Residual (SRMR) = 0.07, and Root Mean-Square Error of Approximation (RMSEA) = 0.07. All of the model fit indexes were acceptable, and seven of the thirteen paths in the final model were significant. The factors that influenced college adjustment were social support (r = 0.39) and ego-identity (β = 0.73), explaining 57.1% of the variance. Conclusions: To increase college adjustment, it is necessary to consider the relationship of adjustment with college students’ surrounding environments, such as their family, friends, and professors, and how students can improve their ego-identity.
Vascular embolization is a minimally invasive nonsurgical technique obstructing a blood vessel by lodgment of embolic materials to treat cancers and vascular lesions. In this paper, we have carried out a parametric study of generation of monodisperse clay-poly(N-isopropylacrylamide) (clay-PNIPAAm) embolic microspheres of which size is comparable to a blood vessel (about 400 m). To achieve monodisperse water-phase clay/ NIPAAm microdroplets, we have designed and fabricated a poly(dimethylsiloxane) (PDMS) hydrodynamic focusing microfluidic device (HFMD) for the generation of microdroplets with the affinity of continuous oil-phase fluid to the hydrophobic PDMS taken into account. We have investigated the influence of process-related flow conditions on the microdroplet generation to determine a proper processing window for obtaining monodisperse microdroplets with the fabricated HFMD. A parametric study of generation of monodisperse microdroplets was carried out by changing volumetric flow rates of two immiscible fluids within the determined processing window. For the suggested condition, the fabricated clay-PNIPAAm microspheres of about 400 m in diameter showed an extremely narrow size distribution with a coefficient of variation of 0.41%. We have also showed the floatability of the fabricated clay-PNIPAAm microspheres in saline and the smooth passage of the microspheres through a commercially available microcatheter as in vitro characterization for embolization. #
Recently, anisometric structures, which are popular in nature but uncommon in artificial materials, have been actively investigated for the development of novel materials designed for sensors, optical systems, scaffolds, etc. In this study we investigated the hypothesis that the symmetry of two-compartment hydrogels influences their temperature responsive behavior and drug diffusivity. Composite hydrogels with isometric and anisometric compartments were prepared using poly(N-isopropylacrylamide), poly(acrylamide), and nanoclay. The anisometric hydrogel showed a markedly smaller volume transition and equilibrium swelling ratio than its isometric counterpart, possibly because of more restriction from the two-compartment structure. Furthermore, water retention and the release of cilostazol were significantly sustained in the case of the anisometric hydrogel. By incorporating Ag nanoparticles into one compartment, an IR responsive transition was achieved, which showed the consistent effect of the anisometric structure. Finite element analysis further confirmed the difference found in the experimental results by presenting a prevailing von Mises stress in the anisometric case. This study provides a novel engineering strategy for hydrogel properties and a fundamental understanding valuable for designing anisometric hydrogel materials.
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