Osteochondral tissue is hard to regenerate after injuries or degenerative diseases. Traditional treatments still have disadvantages, such as donor tissue availability, donor site morbidity, implant loss, and limited durability of prosthetics. Thus, recent studies have focused on tissue engineering strategies to regenerate osteochondral defects with different scaffold designs. Scaffolds have been developed from monolayer structures to bilayer scaffolds to repair the cartilage-bone interface and to support each tissue separately. In this study, Si-substituted nanohydroxyapatite particles (Si-nHap) and silica-based POSS nanocages were used as reinforcements in different polymer layers to mimic a cartilage-bone tissue interface. Chitosan and zein, which are widely used biopolymers, are used as polymer layers to mimic the structure. This study reports the development of a bilayer scaffold produced via fabrication of two different nanocomposite layers with different polymer-inorganic composites in order to satisfy the complex and diverse regenerative requirements of osteochondral tissue. The chitosan/Si-nHap microporous layer and the zein/POSS nanofiber layer were designed to mimic a bone-cartilage tissue interface. Bilayer scaffolds were characterized with SEM, compression, swelling, and biodegradation tests to determine morphological, physical, and mechanical properties. The results showed that the bilayer scaffold had a structure composed of microporous and nanofiber layers joined at a continuous interface with appropriate mechanical properties. Furthermore, in vitro cell culture studies have been performed with LDH, proliferation, fluorescence imaging, and ALP activity assays using osteosarcoma and chondrosarcoma cell lines. ALP expression levels provide a good illustration of the improved osteogenic potential of a porous chitosan/Si-nHap layer due to the Si-doped nHap incorporation. Histological data showed that both fiber and porous layers that mimic the cartilage and bone sections exhibit homogeneous cell distribution and matrix formation. Histochemical staining was used to determine the cell proliferation and ECM formation on each layer. In vitro studies indicated that zein-POSS/chitosan/Si-nHap nanocomposite bilayer scaffolds showed promising results for osteochondral regeneration.
Keywords: POSS; bilayer scaffold; chitosan; osteochondral tissue; zein.