Injectable and Thermosensitive Hydrogel and PDLLA Electrospun Nanofiber Membrane Composites for Guided Spinal Fusion

Spinal fusion is the classic treatment to achieve spinal stability for the treatment of the spinal disease. Generally, spinal fusion still has to combine a certain of bone matrix for promoting bone formation to achieve the desired fusion effect based on the surgery, including the traditional bone matrix, such as the autologous bone, allografts and xenografts. Nevertheless, some problems still existed such as the immunogenic problems, the secondary wound, and pathogenic transfer and so on. Here the injectable thermosensitive hydrogel could substitute to avoid the problems as a potential biological scaffold for tissue engineering. Once injected, they could fill in the irregular-shaped cavity and change to a gel state at physiological temperature. We wanted to design the collagen/n-HA/BMP-2@PCEC/PECE hydrogel composites based on previous work about collagen/n-HA/PECE hydrogel to exhibit better performance in guiding spinal fusion because of the addition of BMP-2@PCEC nanoparticles (PCEC, PCL-PEG-PCL). However, when the hydrogels were injected, one of the surfaces was in contact with the spine, but others were in contact with soft tissue like muscles and fascia. The release behavior was the same at the different surfaces, so the factors could be released into the soft tissue, and it may then be consumed or lead to ectopic bone formation. The hydrogel composites should be improved to adjust the direction of the releaser behavior. In consequence, we wrapped an electrostatic spinning nanofiber membrane possessing hydrophobicity around the hydrogels. In this study, we developed a system that the collagen/n-HA/BMP-2@PCEC/PECE hydrogels were wrapped with the hydrophobicity PDLLA electrospun nanofiber membrane, setting up a barrier between the hydrogels and the soft tissue. The system could exhibit biocompatibility, preventing the factors from escaping to keep their retention in the needed places of osteogenesis; the results demonstrated that it showed an excellent effect on spinal fusion.