Osteoconductive potential of barrier nanoSiO2 PLGA membranes functionalized by plasma enhanced chemical vapour deposition

Abstract

The possibility of tailoring membrane surfaces with osteoconductive potential, in particular in biodegradable devices, to create modified biomaterials that stimulate osteoblast response should make them more suitable for clinical use, hopefully enhancing bone regeneration. Bioactive inorganic materials, such as silica, have been suggested to improve the bioactivity of synthetic biopolymers. An in vitro study on HOB human osteoblasts was performed to assess biocompatibility and bioactivity of SiO2 functionalized poly(lactide-co-glycolide) (PLGA) membranes, prior to clinical use. A 15 nm SiO2 layer was deposited by plasma enhanced chemical vapour deposition (PECVD), onto a resorbable PLGA membrane. Samples were characterized by X-ray photoelectron spectroscopy, atomic force microscopy, scanning electron microscopy, and infrared spectroscopy (FT-IR). HOB cells were seeded on sterilized test surfaces where cell morphology, spreading, actin cytoskeletal organization, and focal adhesion expression were assessed. As proved by the FT-IR analysis of samples, the deposition by PECVD of the SiO2 onto the PLGA membrane did not alter the composition and other characteristics of the organic membrane. A temporal and spatial reorganization of cytoskeleton and focal adhesions and morphological changes in response to SiO2 nanolayer were identified in our model. The novedous SiO2 deposition method is compatible with the standard sterilization protocols and reveals as a valuable tool to increase bioactivity of resorbable PLGA membranes.

Figure 1

AFM images of PLGA (left) and SiO₂/PLGA (right).

Figure 2

From left to right, C1s, O1s, and Si2p photoelectron spectra of PLGA and SiO₂/PLGA as indicated.

Figure 3

FT-IR spectra of the PLGA and SiO₂/PLGA films measured in ATR mode.

Figure 4

HOB cells distribution and spreading after 24 (a, b) and 48 (c, d) hours in culture. Both (b) and (d) represent osteoblasts grown on silica treated PLGA membranes and (a) and (c) represent osteoblasts grown on bare PLGA. All images were obtained in the phase contrast microscope, magnification 40x.

Figure 5

HOB cells grown on bare PLGA and imunolabelled, 48 hours (a, b) and 72 hours (c, d) after seeding, with rhodamine-phalloidin for actin cytoskeleton (red) and antivinculin antibody (green) for focal adhesion sites.

Figure 6

HOB cells grown on SiO₂ functionalized membranes, immunolabelled with rhodamine-phalloidin for actin cytoskeleton (red) and antivinculin antibody (green) for focal adhesion sites, 48 hours after seeding. Representative images of cytoskeletal features and focal adhesions, showing in detail (a, b) stress fibers development, (c, d) cell clustering, and (e, f) lamellipodial and (g, h) filopodial emissions.

Figure 7

HOB cells grown on SiO₂ functionalized membranes, immunolabelled with rhodamine-phalloidin for actin cytoskeleton (red) and antivinculin antibody (green) for focal adhesion sites, 72 hours after seeding. Representative images for (a, b, e, f) cell clustering, (c, d) stress fibers distribution, and (e, f) lamellipodial emissions.

Figure 8

Box-Whisker graphics reporting the variable number of contacts among cells on each sample.