Red-Shifted Luminescence of Acrylonitrile-Containing Copolymers: A Matter of One Methyl Unit.

Copolymerization provides an effective approach to tune the photophysical properties of non-conventional luminescent polymers (NCLPs). In this study, the controlling of intrinsic emissions of polyacrylonitrile (PAN) copolymers is revealed by a delicate difference of secondary monomers. The introduction of methacrylate comonomers can induce a 70-nm red-shifting in the PL emission of copolymers compared with that of acrylate-containing copolymers. The mechanism of such "copolymerization induced red-shifting" in PAN copolymers is investigated. It is demonstrated that the presence of the α-methyl group in the copolymers can enhance the chain rigidity and through-space conjugation (TSC) of C≡N groups, resulting in the red-shifting of emission.

Gradient gyroid Ti6Al4V scaffolds with TiO2 surface modification: Promising approach for large bone defect repair.

Large bone defects, particularly those exceeding the critical size, present a clinical challenge due to the limited regenerative capacity of bone tissue. Traditional treatments like autografts and allografts are constrained by donor availability, immune rejection, and mechanical performance. This study aimed to develop an effective solution by designing gradient gyroid scaffolds with titania (TiO2) surface modification for the repair of large segmental bone defects. The scaffolds were engineered to balance mechanical strength with the necessary internal space to promote new bone formation and nutrient exchange. A gradient design of the scaffold was optimized through Finite Element Analysis (FEA) and Computational Fluid Dynamics (CFD) simulations to enhance fluid flow and cell adhesion. In vivo studies in rabbits demonstrated that the G@TiO2 scaffold, featuring a gradient structure and TiO2 surface modification, exhibited superior healing capabilities compared to the homogeneous structure and TiO2 surface modification (H@TiO2) and gradient structure (G) scaffolds. At 12 weeks post-operation, in a bone defect representing nearly 30 % of the total length of the radius, the implantation of the G@TiO2 scaffold achieved a 27 % bone volume to tissue volume (BV/TV) ratio, demonstrating excellent osseointegration. The TiO2 surface modification provided photothermal antibacterial effects, enhancing the scaffold's biocompatibility and potential for infection prevention. These findings suggest that the gradient gyroid scaffold with TiO2 surface modification is a promising candidate for treating large segmental bone defects, offering a combination of mechanical strength, bioactivity, and infection resistance.

Molecular dynamics study on the encapsulation and release of anti-cancer drug doxorubicin by chitosan.

Doxorubicin (DOX) is a broad-spectrum anti-tumor drug, but it has certain limitations in its therapeutic effects due to poor tumor selectivity. Chitosan-based pH-sensitive polymers drug delivery systems could improve DOX's activity and selectivity against tumor cells. Understanding the atomic interaction mechanism between chitosan and DOX at different pH levels is important in the design and application of chitosan-based drug delivery systems. In this study, molecular dynamics simulations were performed to investigate the encapsulation and release of DOX by chitosan at different pH levels. Our results show that the protonation state of amine groups of chitosan and the π-π stacking interaction between the conjugated anthraquinone ring of DOX regulate the interaction behavior between chitosan and DOX. Moreover, DOX could gradually release from chitosan at acidic pH environment in tumor tissue. These results revealed the underlying atomic interaction mechanism between DOX and chitosan at various pH levels and may provide novel ideas for the design and application of chitosan-based drug delivery system.