Cover: SEM image of composite material nHA/PCL with 30 wt.% nHA. [H. Yang, J. Li, Q. Liao, H. Guo, H. Chen, Y. Zhu, M. Cai, H. Lv: In vitro evaluation of a novel multi-walled carbon nanotube/nano-hydroxyapatite/polycaprolactone composite for bone tissue engineering. p. 532].