Enhanced Osteoconductivity and Osseointegration in Calcium Polyphosphate Bioceramic Scaffold via Lithium Doping for Bone Regeneration

Calcium polyphosphate (CPP) is a novel bioceramic bone substitute, which is favored because its composition is highly similar to natural bone. According to previous studies, doping ions into CPP is an effective and convenient method for overcoming the shortcomings, such as poor osteoconductivity of CPP. Lithium (Li) is a fairly new additive to bone substitutes that brought attention due to its role in osteogenesis. The present study was conducted to assess whether doping Li into CPP could influence the microstructure, degradation, and osteoinductivity of CPP. The results found that both CPP and Li-doped CPP (LiCPP) had a single beta-CPP phase, indicating that Li did not affect the crystallized phase. SEM images revealed that both scaffolds were porous, while the surface of LiCPP was rougher and more uneven compared to CPP. Also, a better degradation property of LiCPP was observed via weight loss and ion release tests. In vitro study found that LiCPP extracts had advantages of promoting osteoblasts' proliferation and differentiation over CPP extracts. In vivo study on rabbit's cranial defects was also conducted. Microcomputed tomography and histological staining showed that LiCPP had better osteoconductivity than CPP. This study proved that doping Li into CPP is a feasible modification method, and LiCPP might be a suitable bioceramic for bone tissue engineering.