The possibilities of chemical and physical modification of cortical bone grafts′ surface in order to increase their adhesive attractiveness to human cells

Introduction. The ability of cells to adhere on bone graft increases its reparative and regenerative properties. The native cortical bone has a very low biological conductivity, which greatly impedes cell migration and adhesion. Various methods of bone surface modification can be used to enhance the bioconductive properties of bone grafts.

Objective. To evaluate the adhesion and proliferative activity of human cells on the surface of cortical bone grafts modified by various methods.

Material and methods. Fragments of cortical bone grafts (CBGs) were used in the study. For physical modification the outer surface of the bone fragments was processed with a flat file with high or low density of grinding teeth. A 2N hydrochloric acid (HCl) solution, 0.005% collagenase I solution, and the collagenolytic enzyme preparation Fermenkol (0.05 mg/mL) were used for chemical modification. In vitro studies of the CBG adhesion were performed in culture of human fibroblasts M-22 line. Untreated CBGs (control) and modified CBGs were placed in the wells of culture vials; a cell suspension containing 10,000 cells was added to each well. Cells were cultured for 7 days.

Results. After 3 days of cultivation, the cells were completely absent or detected in very small numbers on the control CBG samples and CBG samples subjected to mechanical processing. On CBGs treated with 2N hydrochloric acid solution for 3 and 6 hours, the average cell density on the CBG surface estimated 1.0–1.2 thousand/cm²; on CBGs treated with 2N hydrochloric acid solution for 12 hours, the CBG adhesiveness acutely decreased. The highest cell density was observed on CBGs, treated with 0.005% collagenase 1 or Fermencol for 24 hours and amounted to 2.0–2.5 thousand/cm². After 7 days of cultivation, the cell growth was completely absent on the control CBGs, on CBGs processed with a file with a high grinding tooth density, and CBGs treated with 2N hydrochloric acid solution for 12 hours. In experiments with collagenase 1 and Fermencol, as well as in experiments with the treatment with a 2N hydrochloric acid solution for 3 hours, an intensive cell growth was observed on the CBG surface, density of human fibroblasts of the M-22 line and their total number on CBGs increased 3–5-fold without affecting their viability.

Conclusion. Physical modification did not effectively increase the adhesiveness of cortical bone grafts. Effectiveness of chemical modification depends on the duration of exposure to the chemical agent. To increase the adhesion, the cortical bone graft should be optimally treated either with 2N hydrochloric acid solution for 3 hours, or 0.005% collagenase 1 solution for 24 hours, or with Fermencol (0.05 mg/mL) for 24 hours.

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