Journal of the mechanical behavior of biomedical materials最新文献

Despite the great potential of Gelatin Methacryloyl (GelMA) microneedles (MNs) for minimally invasive drug delivery and interstitial fluid extraction, their performance under realistic insertion conditions and across diverse geometrical and mechanical parameters has remained uncharacterized. In this study, dynamic and static finite-element analyses were conducted for the first time to compare three types of crosslinked GelMA MNs: conical, pyramidal, and tapered-conical with and without base support. Insertion force, von Mises stress, and safety factors were evaluated at insertion velocities of 2-6 m/s under varying crosslinking times and polymer concentrations. The tapered-conical geometry demonstrated the best overall mechanical reliability, combining moderate insertion forces with exceptional bending and buckling resistance. Adding a minimal base support further reduced peak stresses and smoothened insertion profiles by up to 20%. Rate-dependent simulations identified an optimal insertion speed of 3-4 m/s that minimizes tissue stress by balancing viscoelastic deformation and impact effects. Longer crosslinking and higher polymer concentrations slightly enhanced needle stiffness and reduced skin stress without increasing penetration force. Together, these results establish a comprehensive design approach that integrates needle geometry, mechanical properties, and applicator dynamics to guide the development of GelMA MN arrays with improved safety and efficacy for clinical translation.

Bone fractures require the proper integration of fixation devices to ensure long-term biomechanical performance and accelerated recovery, while allowing for early load-bearing and equitable load-sharing. The primary objective of this research is to elucidate the effect of four different generations of fixation devices on synthetic tibiae with induced comminuted fractures. The fixation devices considered herein comprised an intramedullary nail, as well as various distal interlocking screws and plates. The overall biomechanical response was studied under quasi-static compressive loading, following cyclic testing to evaluate the overall system stiffness. More advanced generations (Gen III and IV) showed increased stiffness, reaching values of 1304.69 ± 2.90 kN/m and 1461.00 ± 2.98 kN/m, respectively. Cyclic compressive tests were performed before load-to-failure studies, with the biomechanical constructs being instrumented with strain gauges affixed to the intramedullary nail distally and full-field digital image correlation proximally at the superior flat part of the tibia, revealing the load-sharing capabilities of each fixation device configuration throughout the cyclic loading scenario. The digital image correlation analysis revealed that the proximal tibia exhibited higher strain levels in fixation configurations with only two medial-to-lateral screws, further substantiating the importance of incorporating additional components into the bone-implant system to provide greater stabilization. The distal strain gauges, which registered the deformation of the intramedullary nails, revealed that Gen IV, the only configuration including a medial plate, proved to reduce instabilities in that area, thereby enhancing load sharing between the bone and the intramedullary nail. Ultimately, this extensive experimental work elucidates the importance of comprehensive distal tibiae fixations, which are paramount for future interventions, providing biomechanical stability and bone-implant load sharing. These outcomes are clinically relevant, potentially accelerating load-bearing after surgery by selecting the optimal fixation configuration based on patient conditions and improving the quality of life thereafter.

The repair of critical bone defects resulting from trauma, infection, tumors, and congenital malformations poses significant clinical challenges. The combination of medical-grade polycaprolactone (PCL) and β-tricalcium phosphate (β-TCP) is widely investigated for developing synthetic bone graft substitutes, attracting considerable interest in regenerative medicine. However, the material's inherent lack of osteogenic capacity remains a bottleneck to its widespread clinical application. This study synthesized a strontium oxide (SrO)-functionalized three-dimensional (3D)-printed polycaprolactone (PCL)/β-tricalcium phosphate (β-TCP) composite scaffold. Gradient SrO-doped (0-2.0 wt %) 3D printed scaffolds (3D PTSr) were fabricated by melt blending and direct ink writing (DIW) technology, and their physicochemical and biological properties were systematically characterized. Scanning electron microscopy (SEM) showed that the 3D PTSr scaffold had a precisely regulated macroscopic pore structure (pore size ∼ 1 mm) and uniformly distributed Sr element. When the doping amount of SrO was 1.5 wt %, the scaffold exhibited the best comprehensive performance: the surface contact angle was reduced to 64.78° ± 0.54°, and the weight loss rate was 42.83 ± 0.02 % after 4 weeks of in vitro degradation. At the same time, it showed the sustained release characteristics of Sr²⁺ for 56 days (cumulative release of 10.42 ppm). Mechanical tests showed that the compressive strength (5.64 ± 0.04 MPa) and tensile strength (2.75 ± 0.16 MPa) were significantly better than the control group (p < 0.05). In vitro biomimetic mineralization experiments confirmed that SrO functionalization facilitated dense calcium-phosphate composite layer formation. In vitro experiments demonstrated that the 3D PTSr1.5 scaffold significantly promoted the proliferation of MC3T3-E1 cells, and its osteogenic differentiation ability was verified by increasing alkaline phosphatase (ALP) activity and calcium nodule formation. Implantation of 3D PTSr1.5 scaffold into rat cranial defects significantly enhanced bone regeneration at 12 weeks versus controls. Histological analysis confirmed substantial regeneration of mature bone tissue and collagen fibers within the defect area. This study reveals the molecular mechanism of SrO functionalization promoting bone regeneration by regulating the synergistic effect of material degradation-ion release-topology, and provides a theoretical basis and technical reserve for the development of next-generation intelligent bone repair materials.