MG-63 cells proliferation following various types of mechanical stimulation on cells by auxetic hybrid scaffolds

Background: Mechanical properties and cyto-compatibility of a composite scaffold which possessed negative (-) Poisson's ratio (NPR) was investigated for effective load transfer from auxetic scaffold to cell. Methods: Organic/inorganic composite scaffolds were prepared by mixing hydroxyapatite (HA) to poly(lactide-co-glycolide) (PLGA). To induce NPR in composite scaffold, 3-directional volumetric compression was applied during the scaffold fabrication at adequate temperature($60^{\circ}C$). The pore size of scaffold ranged between $355-400{\mu}m$. Results: Poisson's ratios of NPR scaffolds and control scaffolds were -0.07 and 0.16 at 10 % strain. For stable physical stimulating to loaded cells, ceramic/polymer composite scaffold was prepared by incorporating HA in PLGA to increase mechanical strength. Compressive strength of the HA/PLGA composite scaffold (15 wt. % HA to PLGA) was about 21.7 % higher than that of PLGA-only scaffold. The recovery rates of the NPR composite scaffold after applying compression in the dry and wet states were 90 % and 60 %, respectively. Also the composite scaffold was shown to have better hydrophilicity ($61.9^{\circ}$) compared to the PLGA-only scaffolds ($65.3^{\circ}$). Cell proliferation of osteoblast-like cell line (MG-63) in the composite scaffold was 20 % higher than in PLGA-only scaffold at static compressive stimulation. For dynamic compressive stimulation (15 min cyclic interval), cell proliferation in the composite scaffold was 2 times higher than that of in PLGA-only scaffold. In conclusion, NPR composite (HA/PLGA) scaffold was effective in isotropic compressive load delivery for osteogenic cell proliferation. Conclusion: This composite scaffold with stimulation can be used as tissue engineered scaffold and dynamic cell culture system for bone tissue regeneration.