In vitro degradation of fibrous bilayer poly-L-lactic acid scaffolds.

Polymer degradation and mechanical properties are of paramount importance in tissue engineering. The degradation rate of polymeric scaffolds is influenced by several important material and environmental factors. In particular, the mechanical support provided by the scaffold to the surrounding tissue during tissue regeneration is critical for that it directly impacts the cell behavior through mechanical signals sensed by mechanoreceptors on the cell surface. Consequently, the principal objective of the present study was to investigate the degradation behavior of electrospun poly-L-lactic acid (PLLA) bilayer microfibrous scaffolds in pH-neutral medium. Changes in the morphology, molecular weight, crystallinity, mass loss, and thermomechanical properties of the scaffolds over an extended period were studied by scanning electron microscopy, differential scanning calorimetry, gel permeation chromatography, and tensile testing. An interplay between chain scission and orderly chain rearrangement in the polymer scaffold commenced during degradation, leading to the decrease of the molecular weight and stiffness, a constant mass loss, and an increase in crystallinity, tensile strength, and glass transition temperature, with virtually constant yield strength and melting temperature. The unchanged structure morphology and adequate matrix stiffness after prolonged degradation illuminated the potential of the bilayer PLLA scaffolds for tissue engineering and drug delivery applications. Nonetheless, modifications to the scaffold structure or surface may be required to accordingly tune the degradation rate in these applications. The experimental methodology introduced in this study can be extended to potentially investigate material degradation in other fields, such as agriculture, packaging, and disposable products.

An overview of the tribological and mechanical properties of PEEK and CFR-PEEK for use in total joint replacements.

Poly-ether-ether-ketone (PEEK) and PEEK composites are outstanding candidates for biomedical applications, such as orthopedic devices, where biocompatibility and modulus match with surrounding tissue are requisite for long-term success. The mechanical properties can be optimized by incorporating fillers such as continuous and chopped carbon fibers. While much is known about the mechanical and tribological behavior of PEEK composites, there are few articles that summarize the viability of using PEEK reinforced with carbon fibers in orthopedic implants. This paper reviews biocompatibility, tribological, and mechanical studies on PEEK and their composites with carbon fibers, notably PEEK reinforced with polyacrylonitrile (PAN)-based carbon fibers and PEEK reinforced with pitch-based carbon fibers, for application in orthopedics and total joint replacements (TJRs). The main objectives of this review are two-fold. Firstly, this paper aims to assist designers in making informed decisions on the suitability of using PEEK and PEEK composites in orthopedic applications; as it is not well understood how these materials perform on the whole in orthopedics and TJRs. Secondly, this paper aims to serve as a centralized paper in which researchers can gain information on the tribological and mechanical advancements of PEEK and PEEK composites.