Investigations into poly(3-hydroxybutyrate-co-3-hydroxyvalerate) surface properties causing delayed osteoblast growth

Osteoblast proliferation is sensitive to material surface properties. In this study, the proliferation of MC3T3 E1-S14 osteoblastic cells on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) films with different surface characteristics was investigated with the aim of evaluating the cause of a lag in cell growth previously observed. The solvent-cast films were prepared using three different solvents/solvent mixtures which produced PHBV films with both a rough (at the air interface) and smooth (at the glass interface) surface. Investigation of the surface roughness by scanning electron and scanning probe microscopy revealed that the surfaces had features that were different in both average lateral size and average amplitude (Ra 20-200 nm). Water contact angles showed that all surfaces were hydrophobic in nature (thetaA in the range 69-82 degrees ). The lateral distribution of surface crystallinity of the films was evaluated by use of micro-attenuated total reflectance Fourier transform infrared (ATR-FT-IR) by determining the surface crystallinity index (CI) which was found to differ between samples. MC3T3-E1-S14 osteoblasts were cultured on the six surfaces and proliferation was determined. After 2 days, cell proliferation on all surfaces was significantly less than on the control substrate; however, after 4 days cell proliferation was optimal on three surfaces. It was concluded that the initial lag on all substrates was due to the hydrophobic nature of the substrates. The ability of the cells to recover on the materials was attributed to the degree of heterogeneity of the crystallinity and surface roughness: samples with a roughness of 80 nm were found to support cell proliferation. In addition, the lateral surface features influenced the proliferation of osteoblasts on the PHBV film surface.