Surface modification of chitin nanocrystals with hydroxyapatite deposition and polymer grafting for poly(lactic...

Rod-like chitin nanocrystals (ChNC) were modified through a sequential process involving hydroxyapatite (HA) deposition and poly(lactic acid) grafting, yielding ChNC@HA-PLLA nanohybrids. These functionalized nanocrystals were incorporated as reinforcing fillers into a PLA matrix to fabricate composite films. Comprehensive characterization confirmed the successful modification and the uniform dispersion of nanocrystals within the matrix at an optimal loading of 10 wt%. This composite exhibited significantly enhanced mechanical properties (108.80% increase in Young's modulus and 44.75% increase in tensile strength), improved hydrophilicity, and effective neutralization of acidic degradation products due to the buffering capacity of deposited HA. In vitro assessments demonstrated excellent cytocompatibility and a pronounced ability to promote osteogenic differentiation of MC3T3-E1 cells, as evidenced by upregulated osteogenic markers (RUNX2, OCN) and enhanced mineralization. Most importantly, in a rat calvarial defect model, the composite film significantly accelerated new bone formation over 4 and 12 weeks, as validated by micro-CT and histomorphometric analyses. These findings collectively indicated that the ChNC@HA-PLLA reinforced PLA composite was a promising biomaterial for applications in periodontal bone regeneration and other orthopedic fields.