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Introduction of PVA can improve the compliance of bacterial nano-cellulose hydrogel, which has been suggested as a promising biomaterial for artificial blood vessels especially for small-caliber vessels.

While various porous scaffolds have been developed, the focused study about which structure leads to better mechanics is rare. In this study, we designed porous scaffolds with tetragonal, hexagonal and wheel-like structures under a given porosity, and fabricated corresponding poly(lactic acid) (PLA) scaffolds with three-dimensional printing. High-resolution micro-computed tomography was carried out to calculate their experimental porosity and confirm their high interconnectivity. The theoretical and experimental compressive properties in the longitudinal direction were characterized by finite element analysis method and electromechanical universal testing system, respectively. Thereinto, the scaffold with the tetragonal structure exhibited higher mechanical strength both theoretically and experimentally. Creep and stress relaxation behaviors of the scaffolds revealed that the tetragonal scaffold had less significant viscoelasticity. Immersion dynamic mechanical analysis was performed to test their cycle-loading fatigue behaviors in the simulated body fluid at 37 °C; the tetragonal scaffold exhibited the latest fatigue beginning point at 4400 cycles, which indicated a better anti-fatigue performance; the hexagonal and wheel-like ones exhibited the middle and earliest fatigue beginning points at 3200 and 2500 cycles, respectively. What is more, cytocompatibility and histocompatibility of the scaffolds with all of the structures were confirmed by cell counting kit-8 assay in vitro and three-month subcutaneous implantation in rats in vivo. Hence, the key property difference of the three examined structures comes from their mechanics; the tetragonal structure exhibited better mechanics in the longitudinal direction examined in this study, which could be taken into consideration in design of a porous scaffold for tissue engineering and regeneration.

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Aqueous solutions of some amphiphilic block copolymers undergo a sol-gel transition upon heating and are thus called thermogels. In the thermogel family, some systems also exhibit a gel-sol (suspension) transition at higher temperatures following the sol-gel transition, which is usually ignored in biomedical applications. Herein, for the first time, a case is reported employing both the sol-gel transition and the gel-sol (suspension) transition, which is found in the development of a transdermal hydrogel formulation containing 5-aminolevulinic acid for photodynamic therapy (PDT) of skin disease. Two poly(d,l-lactide-co-glycolide)-b-poly(ethylene glycol)-b-poly(d,l-lactide-coglycolide) triblock copolymers of different block lengths are synthesized. The transition temperatures of the formulation can be easily adjusted to meet the condition of sol-gel transition temperature (T gel ) < room temperature (T air ) < gel-sol (suspension) temperature (T sol (suspension) ) < body temperature (T body ) via changing the blending ratio. Therefore, after applying to skin, formulation of spontaneous asymmetry with a hydrogel outside and a sol (suspension) inside can avoid free flowing and achieve rapid release to ensure an efficient PDT. This study demonstrates such a concept via characterizations of the "block blend" biomaterials and drug release profiles, and also via cell experiments, in vitro permeation, and in vivo transdermal delivery studies.