Abstract
The effect of dynamic compressive stimulation on MG-63 cell proliferation on an auxetic PLGA scaffold was investigated. The estimated Poisson ratio of the prepared auxetic scaffold specimens was approximately (−)0.07, while the Poisson ratio estimated for conventional scaffold specimens was (+)0.12 under 10% strain compression on average. Three stimulus groups were examined: control (no stimulation), static compression, and dynamic compression. In preparation for proliferation testing, cells were seeded at 2.2 × 105 cells/80 μL on each scaffold specimen. The average proliferation rates of the static and dynamic groups were higher than those of the control group: 13.4% and 25.5% higher at culture day 1, 34.7% and 56.2% at culture day 3, and 17.5% and 43.0% at culture day 5, respectively. The static and dynamic group results at culture day 5 were significantly different (p<0.01). Moreover, proliferation rate of the dynamic stimulation group was 1.22 times higher than that of the static group (p<0.01). Conclusively, proliferation of osteoblast-like cells was enhanced through compressive stimulation, but the enhancement was maximal with dynamic compressive stimulation of auxetic scaffolds.
Highlights
A scaffold or three-dimensional structure can provide the support necessary for new cell growth by providing a porous structure, an adequate degradation rate, and an architectural structure that provide an appropriate shape for new bone and cartilage [1, 2]
The first mechanical model of a structure exhibiting negative Poisson’s ratio (NPR) was described by Almgren (1985) [8], and the first thermodynamic model of a system forming a phase with NPR, which means that the auxetic structure phase was built spontaneously by the model’s molecules, was studied by performing computer simulations [9, 10]
The results of this study indicate that the positive Poisson ratio of the conventional scaffold was (+)0.12 ± 0.035 under 10% strain compression, whereas the experimental specimen had NPR of (−)0.07 ± 0.036 under 10% strain compression (Figure 4)
Summary
A scaffold or three-dimensional structure can provide the support necessary for new cell growth by providing a porous structure, an adequate degradation rate, and an architectural structure that provide an appropriate shape for new bone and cartilage [1, 2]. Materials with negative Poisson’s ratio (NPR) are called auxetic materials [4,5,6,7]. Fabrication of auxetic structural scaffolds can be achieved by transforming the cell structure from a convex polyhedral shape to a concave or reentrant shape in which cell ribs protrude inward. Such structures have a characteristic inverted manner that is similar to that of a honeycomb [15,16,17]. A natural auxetic material that has been studied and predicted to have NPR is the load-bearing cancellous bone present in human shins.
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