In vivo osteogenesis induced by differently treated SF films. Immunohistochemical staining of Col I, OPN and OCN in the subcutaneously implanted SF, A-SF, SF-nHAp and A-SF-nHAp films seeded with MSCs. Blue and red arrows indicated the positive expression of OPN and OCN, respectively. Immunohistochemical staining showed that more bone matrix proteins were deposited around the A-SF and A-SF-nHAp films than around the SF and SF-HAp films. Moreover, more OPN was deposited around the A-SF-nHAp than around A-SF films. SF: pristine SF film; A-SF: air-plasma-treated SF film; SF-nHAp: SF film with mineralized nHAp; A-SF-nHAp: A-SF film with mineralized nHAp; M: implanted materials.