Layer-by-layer coated porous 3D printed hydroxyapatite composite scaffolds for controlled drug delivery.

Interconnected porous scaffolds are widely used in the applications of tissue repair and regeneration. Sustained local delivery of drugs and growth factors around the implanted scaffolds could accelerate the growth of cells and contribute to the regeneration of damaged tissues. In this study, porous hydroxyapatite composite scaffolds were prepared through 3D bio-printing for bone tissue engineering and were subsequently coated with chitosan and sodium hyaluronate by layer-by-layer (LBL) deposition. It was found that the LBL coating on the porous scaffolds could reduce the swelling ratio of scaffolds in size and increase the compressive strength by about 70%. The degradation rate of the scaffolds slowed down due to the LBL coating. Rhodamine B (RHB) and bovine serum albumin (BSA) were chosen as model drugs in order to understand the loading and release behaviors of the scaffolds. Small RHB molecules could penetrate deep into the LBL coated scaffolds and released a little slower than that without coating. Meanwhile, large BSA molecules showed faster release rate compared to that without coating. In addition, there was no significant cytotoxicity effect of these composite scaffolds towards MC-3T3E1 cells and the scaffolds provided proper conditions for cell adhesion and proliferation, indicating that the printed hydroxyapatite composite scaffolds exhibit a great potential in hard tissue engineering as a sustained delivery system.