High-Efficient Vacuum Ultraviolet-Ozone Assist-Deposited Polydopamine for Poly(lactic-co-glycolic acid)-Coated Pure Zn toward Biodegradable Cardiovascular Stent Applications.

Zinc is a prospective metal for biodegradable cardiovascular stent applications, but the excessively released Zn2+ during degradation remains a huge challenge in biocompatibility. Considerable efforts have been made to develop a high-efficient surface modification method, while maintaining adhesion strength, mechanical support, and vascular compatibility. Biomimetic polydopamine (PDA) can adhere to Zn tightly, subsequently achieving robust chemical bonds with poly(lactic-co-glycolic acid) (PLGA) coating. However, the deposition of PDA on Zn depends on the controlled conditions such as a sensitive pH and a long period of time. Herein, we introduce vacuum ultraviolet-ozone (VUV/O3) assist-deposition technology to accelerate the polymerization of PDA on pure Zn, which shortens the process to 40 min at a moderate pH of 8.5 and improves the deposition rate by 1-2 orders of magnitude under sufficient active oxygen species (ROS). Additionally, PLGA/PDA coating enhances the corrosion resistance, and their effective protection maintains the mechanical properties after long-term corrosion. Moreover, the controlled Zn2+ release contributes to the superior in vitro biocompatibility, which inhibits the hemolysis rate and smooth muscle cell (SMC) proliferation. The enhanced endothelial cell (EC) proliferation is promising to promote the re-endothelialization, avoiding in-stent restenosis and neointimal hyperplasia. Such modified Zn might be a viable candidate for the treatment of cardiovascular diseases.

Thermosensitive vancomycin@PLGA-PEG-PLGA/HA hydrogel as an all-in-one treatment for osteomyelitis.

Osteomyelitis is a difficult-to-treat infectious disease. Treatment, which includes controlling the infection and removing necrotic tissues, is challenging. Considering the side effects and drug resistance of systemic antibiotics, local drug delivery systems are being explored. Antibiotic-loaded bone cement is the main treatment strategy; however, it has several disadvantages. Thus, based on its thermosensitive gelation properties, poly(D, L-lactide-co-glycolide)-poly(ethylene glycol)-poly(D, L-lactide-co-glycolide) (PLGA-PEG-PLGA) copolymer was used as a sustained-release drug carrier by calibrating its synthesis parameters. We prepared and characterized vancomycin@PLGA-PEG-PLGA/hydroxyapatite (HA) thermosensitive hydrogel with an LA/GA ratio of 15:1. The rheological characteristics, sol-gel phase-transition properties, and critical micelle concentration value of the PLGA-PEG-PLGA/HA complex confirmed that it undergoes a temperature-sensitive sol-gel phase transition. Furthermore, the HA in the composite increased the storage modulus of the system. FT-IR, XRD, and TEM findings showed that HA could be dispersed uniformly in the PLGA-PEG-PLGA polymer. Moreover, HA neutralized acidity during polymer degradation, improving in vitro cytocompatibility. In vitro and in vivo antibacterial experiments showed that the composite sustained-release system exhibited good bone repair characteristics owing to its efficacy in infection treatment. Therefore, vancomycin@PLGA-PEG-PLGA/HA allows sustained release of antibiotics and promotes bone tissue repair, showing potential for wide clinical applicability.

Mechanical analysis of femoral stress-riser fractures.

BACKGROUND: A stress-riser fracture develops when stress in an object is higher than that in the surrounding material. The aim of this retrospective study was to evaluate all consecutive femoral stress-riser fractures during a period of >10 years and to verify high-risk factors by using mechanical analysis. METHODS: Forty clinical fractures caused by local stress concentration in the femoral cortical bone were included. Risk factors were analyzed, and Sawbones models were used to verify their effect. One hundred thirty-six models were divided into 6 groups to simulate clinical cases of stress-riser fractures. A dynamic test instrument was used to simulate weight-bearing on the femoral head by continuous application of increasing axial force; the lever arm was applied at a constant speed of 0.1 mm/s until a fracture developed. RESULTS: Female gender (57.5%), subtrochanteric area (40%), osteoporosis (40%), and technical or surgical errors (50%) were risk factors for stress-riser fractures in clinical analysis. Cortical perforation, tiny cracks, sharp corners, and changes in hardness were the main risk factors in biomechanical aspects. Mechanical analysis identified that these factors contributed to stress-riser fractures (P = 0.000), especially cortical perforations and sharp corners. CONCLUSION: A cortical perforation (screw hole), tiny crack (fracture line), sharp corner (bone cut), and change in hardness (tip of an implant or cement) can act as a stress riser. Screw holes are the most common and critical contributor to femoral stress-riser fractures.