In-situ growth of silica nano-protrusions on halloysite nanotubes for interfacial reinforcement in polymer/halloysite scaffolds

Abstract The mechanical reinforcing effects of halloysite nanotubes (HNT) on polymer scaffolds were restricted due to poor interfacial adhesion and dispersion. In this study, silica (SiO2) nano-protrusions were in-situ grown on HNT via the hydrolysis of tetraethoxysilane (TEOS) and the polycondensation of its intermediates with the surface O–H groups of HNT. Then, HNT@SiO2 was introduced to poly (L-lactide) (PLLA) scaffolds for better mechanical reinforcing, which were prepared by laser additive manufacturing. The results indicated many irregularly shaped SiO2 nano-protrusions were in-situ grown on HNT with Si-O bonding under a low (L) and medium (M) concentration of TEOS, while there formed many free SiO2 particles under a high (H) concentration. The in-situ grown organosilane-derived SiO2 nano-protrusions effectively strengthened the interaction of HNT@SiO2 with PLLA, contributing to strong interfacial adhesion between HNT@SiO2 and the PLLA matrix as well as good dispersion of HNT@SiO2. As a result, PLLA/HNT@SiO2-L and M scaffolds showed much higher tensile strength and modulus than those of PLLA and PLLA/HNT. Besides, PLLA/HNT@SiO2 scaffolds supported the responses of stem cells, and showed improved apatite-forming ability and hydrophilicity. This study suggested the potential application of HNT@SiO2 in reinforcing polymer-based bone tissue engineering scaffolds.