Yanyan Zheng

Bone-like apatite coating on functionalized poly(etheretherketone) surface via tailored silanization layers technique.

Poly(etheretherketone) (PEEK) is a rigid semi-crystalline polymer with outstanding mechanical properties, bone-like stiffness and suitable biocompatibility that has attracted much interest as a biomaterial for orthopedic and dental implants. However, the bio-inert surface of PEEK limits its biomedical applications when direct osteointegration between the implants and the host tissue is desired. In this work, -PO4H2, -COOH and -OH groups were introduced on the PEEK surface by further chemical treatments of the vinyl-terminated silanization layers formed on the hydroxylation-pretreated PEEK surface. Both the surface-functionalized and pristine specimens were characterized by X-ray photoelectron spectroscopy (XPS), attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and water contact angle measurements. When placed in 1.5 strength simulated body fluid (SBF) solution, apatite was observed to form uniformly on the functionalized PEEK surface and firmly attach to the substrate. The characterized results demonstrated that the coating was constituted by poorly crystallized bone-like apatite and the effect of surface functional groups on coating formation was also discussed in detail. In addition, in vitro biocompatibility of PEEK, in terms of pre-osteoblast cell (MC3T3-E1) attachment, spreading and proliferation, was remarkably enhanced by the bone-like apatite coating. Thus, this study provides a method to enhance the bioactivity of PEEK and expand its applications in orthopedic and dental implants.

Enhanced osteoblast cells adhesion, spreading, and proliferation to surface-carboxylated poly(etheretherketone)

Poly(etheretherketone) is a rigid semicrystalline thermoplastic that combines excellent mechanical properties, broad chemical resistance, and bone-like stiffness, and is widely used in biomedical fields. However, the hydrophobic bio-inert surface of poly(etheretherketone) tends to hinder its biomedical applications when direct osteointegration between the implants and the host tissue is desired. In this investigation, poly(etheretherketone) surface was functionalized by a method with chemistry analogous to the formation of organosilane self-assembled monolayers on glass or silicon. First, poly(etheretherketone) surface activation with selective carbonyl reduction introduces surface hydroxylation. And then treatment of the hydroxylation-pretreated poly(etheretherketone) samples with a substituted organosilane solution forms the carboxyl (–COOH) functional surface layers. The modified surfaces were characterized using X-ray photoelectron spectroscopy, water contact angle measurements, differential scanning calorimetry, X-ray diffraction, and surface profiler. The effect of cell adhesion, spreading, and proliferation on each specimen was investigated. Pre-osteoblast cells (MC3T3-E1) adhesion, spreading, and proliferation were improved remarkably on surface-carboxylated poly(etheretherketone). Poly(etheretherketone) modified with –COOH on its surface has potential use in orthopedic or dental implants.

Enhanced osteogenic activity of phosphorylated polyetheretherketone via surface-initiated grafting polymerization of vinylphosphonic acid

Polyetheretherketone (PEEK) is considered to be a prime candidate with the potential to replace biomedical metallic materials as an orthopedic and dental implant on account of its elastic modulus similar to that of human cortical bone. Unfortunately, its biomedical application is impeded by the bioinert surface property and inferior osteogenic activity. In this work, phosphate groups were incorporated onto the PEEK surface through a single-step UV-initiated graft polymerization of vinylphosphonic acid. Diffuse reflectance Fourier transform infrared spectroscopy (DRFTIR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) revealed that phosphate groups were successfully introduced onto the PEEK surface without apparently altering its surface topographical feature and roughness. Water contact angle measurements diclosed the increasing hydrophilia after surface phosphonation. In vitro cell adhesion, spreading, proliferation, alkaline phosphatase activity, extracellular matrix mineralization, and real-time PCR analyses showed enhanced adhesion, spreading, proliferation and osteogenic differentiation of MC3T3-E1 osteoblast on the surface-phosphorylated PEEK. An in vivo biological evaluation in the rabbit tibiae proximal defect model by means of a histological analysis confirmed that the surface-phosphorylated PEEK had improved bone-implant contact. The obtained results indicate that enhanced osteogenic activity to surface-phosphorylated PEEK, which gives positive information of its potential applications in orthopedic and dental implants.

Fabrication and characterization of PDLLA/pyrite composite bone scaffold for osteoblast culture

A series of highly interconnected porous poly(D,L-lactide acid) (PDLLA)/pyrite (Zi-Ran-Tong, FeS2) scaffold containing 5–20% of pyrite was fabricated by particle leaching combined with the thermal-induced phase separation method. Pyrite (FeS2, named as Zi-Ran-Tong in Chinese medicine), as a traditional Chinese medicine, has been used in the Chinese population to treat bone diseases and to promote bone healing. The mechanical properties of the PDLLA scaffold were significantly enhanced after the addition of pyrite. The osteoblastic ROS17/2.8 cell line was used and seeded on the PDLLA/pyrite scaffold to study its potential to support the growth of osteoblastic cells and to estimate the optimal dose of pyrite for bone tissue engineering. The effects of pyrite on cell proliferation and differentiation were evaluated by 3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide and alkaline phosphatase activity assay. The cells on the porous composite scaffold formed a continuous layer on the outer and inner surface observed by scanning electron microscopy and fluorescence microscope. The results strongly suggested that the PDLLA/pyrite composite scaffold could stimulate the growth of ROS17/2.8 cells in vitro and it could be potentially used as a scaffold for bone tissue engineering.