High-modulus nanocomposite scaffold based on waterborne polyurethane grafted collagen polypeptide/hydroxyapatite for potential bone healing

Abstract

A potential nanocomposite scaffold based on waterborne polyurethane grafted collagen polypeptide/hydroxyapatite (WPU-g-CP/HAp) was investigated in this research. First, a non-solvated WPU-g- CP copolymer emulsion was synthesized via water phase cross-linking copolymerization between waterborne polyurethane (WPU) prepolymer and KH550 modified collagen polypeptide (CP). Then, the WPU-g-CP/HAp was fabricated employing bionic precipitation method of HAp nanocrystals, followed by freeze-drying casting. TEM images of WPU-g-CP/HAp emulsion particles showed an assembly of polymer nano-microspheres with a HAp mineralized area. FT-IR and XRD results confirmed that the large quantities of HAP microcrystalline structures were formed in the WPU-g-CP/HAp nanocomposite. DMA analysis demonstrated that the WPU-g-CP/HAp had extremely high storage modulus (7000 MPa) and mechanical strength, which were very important for mechanical support as an ideal bone healing material. TG/DTG, SEM and EDS indicated that HAp has been uniformly dispersed into the nanocomposite in the form of crystallites, and showed good thermal stability and structural stability. Biodegradation test revealed that the degradation cycle of WPU-g-CP/HAp can meet the requirements of bone healing material. It could be expected that in the process of nanocomposite degradation the HAp will be continuously released into the extracellular environment to achieve bone healing via providing scaffolding for osteoconduction, proliferation, growth factors for osteoinduction, and new bone formation, which is extremely beneficial as a bone tissue healing scaffold.