Bone ingrowth induced by gelatin/chitosan internal matrix of 3DP Ti6Al4V scaffold

Regarding its structural and mechanical adaptability to bone defects, 3D printed (3DP) Ti6Al4V scaffolds are widely used in orthopedics now, purposed to restore the function and mechanical stability of impaired bone. In scaffold fabrication, surface modification is acknowledged as a reliable strategy to enhance the interface interaction between 3DP Ti6Al4V scaffold and bone. Despite its advantage in bone-Ti6Al4V bonding improvement, surface modification lacks the ability to induce bone in-growth efficiently as expected. As an attempt to overcome this challenge, in the current work the inner voids of 3DP Ti6Al4V scaffold were occupied by a gelatin/chitosan porous matrix, purposed to act as a platform for guiding bone ingrowth. Firstly, the gelatin/chitosan matrix was prepared via freeze-drying using genipin as a crosslinker, resulting in a trabecular bone-like interconnected porous network characterized with a gelatin/chitosan ratio dependent swelling capability, degradation and model anti-bacterial drug release behavior. Besides of that, gelatin in the matrix was witnessed to accelerate biomineralization in simulated body fluid. Secondly, a formulated gelatin/chitosan matrix was embedded into 3DP Ti6Al4V scaffold to generate a composite scaffold capable of inducing bone in-growth. The followed studies showed gelatin/chitosan matrix can endow the scaffold with good biological and sustained drug release properties, along with minimal change to the compressive strength of the scaffold. The in vivo experiment results revealed that after 4 weeks of implantation, more new bone formation was witnessed in the inner structure of the composite scaffold than the 3DP Ti6Al4V scaffold, with the average bone volume fraction (BV/TV) value increased from 24.09 % to 46.08 %, the average trabecular bone thickness (Tb. Th) value increased from 0.118 mm to 0.278 mm. Therefore, it was confirmed an inner matrix in 3DP Ti6Al4V scaffold played an essential role in guiding bone in-growth.