Surface modification of nanodiamond: Toward the dispersion of reinforced phase in poly-l-lactic acid scaffolds.

The agglomeration of nanodiamond severely reduces the reinforcement in matrix of composites although it is often used as a reinforcing phase. In this study, nanodiamond was modified by phospholipid to promote its dispersion in Poly-l-lactic acid (PLLA) scaffolds fabricated via selective laser sintering. Concretely, phospholipid was an amphiphilic substance with hydrophilic head and hydrophobic tails. The hydrophilic head could adsorb on nanodiamond surface through hydrogen bonding between the OH of head and the COOH of nanodiamond. The hydrophobic tails were forced arrange toward the PLLA matrix. As a result, nanodiamond particles were covered with a layer of phospholipid. They are compelled far away from each other due to the exclusion between the hydrophobic tails. This promoted the dispersion of nanodiamond in PLLA scaffolds. Consequently, the compressive strength, compressive modulus and Vickers hardness of the scaffolds modified by phospholipid increased by 162.8%, 163.2% and 88.2% compared with those of unmodified scaffolds, respectively. Meanwhile, the scaffolds could provide a suitable environment that enabled cells to adhere, grow and migrate, indicating good cytocompatibility. This study suggested the PLLA/nanodiamond scaffolds modified by phospholipid could be a potential candidate for bone tissue engineering applications.