ABSTRACT
Hydroxypropyl starch-based composite system has high potential for many applications such as food packaging and biomedical fields. Here, how the incorporation of curdlan, a thermo-irreversible heating-set gel, tailors the processability, structure, and film performance of hydroxypropyl starch, a cooling-set gel, has been systematically investigated, aiming to achieve enhanced material properties favorable for edible packaging applications. Curdlan incorporation increased the shear-thinning behavior and viscosity of hydroxypropyl starch solution, which was also strongly affected by temperature. The miscibility and comparability between the two polymers with distinct gelation behaviors is a practical and interesting scientific topic. Scanning electron microscopy, dynamic mechanical analysis, and thermogravimetric analysis all indicated good compatibility between hydroxypropyl starch and curdlan. There was no observable phase boundary between the two materials, and all composite films showed only a single relaxation peak and only one polymer thermal decomposition peak. This resulted in improved structural density and overall performance. Compared with pure HPS film, the 7:3 HPS/CD film showed increases in tensile strength by 66.12 % and thermal decomposition temperature by 3 °C, and a reduction in water solubility by 11.72 %. This knowledge gained here may facilitate the development of edible films based on hydroxypropyl starch with satisfying film performance and processability.
ABSTRACT
Infection and aseptic loosening caused by bacteria and poor osseointegration remain serious challenges for orthopedic implants. The advanced surface modification of implants is an effective strategy for addressing these challenges. This study presents a "pneumatic nanocannon" coating for titanium orthopedic implants to achieve on-demand release of antibacterial and sustained release of osteogenic agents. SrTiO3 nanotubes (SrNT) were constructed on the surface of Ti implants as "cannon barrel," the "cannonball" (antibiotic) and "propellant" (NH4HCO3) were codeposited into SrNT with assistance of mussel-inspired copolymerization of dopamine and subsequently sealed by a layer of polydopamine. The encapsulated NH4HCO3 within the nanotubes could be thermally decomposed into gases under near-infrared irradiation, propelling the on-demand delivery of antibiotics. This coating demonstrated significant efficacy in eliminating typical pathogenic bacteria both in planktonic and biofilm forms. Additionally, this coating exhibited a continuous release of strontium ions, which significantly enhanced the osteogenic differentiation of preosteoblasts. In an implant-associated infection rat model, this coating demonstrated substantial antibacterial efficiency (>99%) and significant promotion of osseointegration, along with alleviated postoperative inflammation. This pneumatic nanocannon coating presents a promising approach to achieving on-demand infection inhibition and sustained osseointegration enhancement for titanium orthopedic implants.
