Effect of Tannic Acid Crosslinking on the Mechanical Properties of Collagen Scaffolds and Melanoma Cell Proliferation
Bridgeman, Christopher John
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Metastatic melanoma is responsible for nearly 10,000 deaths in the United States each year. While the prognosis for patients with localized early stage melanoma cancer is good, the chances of survival for patients with late stage metastatic melanoma are only 16%. Matrix stiffness has been shown to have a profound effect on tumor metastasis for breast cancer, but little is known about its role on melanoma metastasis and progression. Similarly, the therapeutic effect of tannic acid (TA) has been extensively characterized for soft breast and leukemia cancers, but not for melanoma. The goal of the current study was to investigate the synergistic effects of TA and collagen matrix stiffness on the proliferation of A375 melanoma cells. We hypothesized that TA will preferentially inhibit the proliferation of A375 melanoma cells compared to non-cancerous NIH 3T3 fibroblasts. Further, we hypothesized that TA will have a differential effect on soft collagen gels vs. stiff collagen gels. Uncompacted (UC) collagen gels (soft) were prepared using a conventional method to induce collagen fibrillogenesis. An electro-compaction method was employed to densify collagen solutions and synthesize electrochemically compacted (ECC) collagen gels (stiff). Different concentrations of TA were used to crosslink UC and ECC collagen gels and assess its effect on gel morphology, mechanical properties and cellular response. SEM imaging showed that TA crosslinking resulted in the merging of collagen fibrils and decrease in pore size of both UC and ECC collagen gels. Tensile test results showed that TA crosslinking significantly (p < 0.05) improved the strength and modulus of ECC collagen gels. Results from Alamar blue assay showed that TA solubilized in the culture medium inhibited the proliferation of both A375 melanoma cells and NIH 3T3 fibroblasts. However, TA more significantly decreased (p < 0.05) the proliferation of A375 cells compared to NIH 3T3 fibroblasts on UC collagen gels. Further, A375 cell proliferation was more significantly reduced (p < 0.05) on TA crosslinked UC collagen gels compared to TA crosslinked ECC collagen gels. On the other hand, TA had a similar effect on both cell types when cultured on ECC collagen gels. In conclusion, results from this study suggest that TA incorporated into UC gels may preferentially affect melanoma cells, and that matrix stiffness is an important driver of tumor proliferation and progression.