Degradation and biocompatibility studies of PLA-PHEA and PCL-PHEA gels for bone tissue regeneration

FERNANDEZ JM; VIKINGSON L; OBERTI TAMARA; GÓMEZ RIBELLES JL; CORTIZO AM

Rosario

Congreso; VIII Congreso Latinoamericano de Órganos Artificiales y Biomateriales, COLAOB 2014; 2014

Bone tissue engineering is born from the need to replace existing therapies for the repair of extensive bone lesions, using different types of materials such as polymers that can guide tissue repair, after which they are broken down and eliminated from the body. Therefore, a necessary condition for the use of these materials is that their degradation rate must be in line with the time needed for tissue repair, among other requirements. The overall objective of this work was the development, characterization and evaluation of the capacity of matrices based on synthetic polymers to stimulate bone formation mediated by osteoblasts. To this end, we developed networks of poly--caprolactone polymer (PCL), poly 2-hydroxyethyl acrylate (PHEA) and poly lactic acid (PLA). The polymeric networks of PCL, PLA and PHEA generate crosslinked hydrogels with different water retention capacity, thus affecting both their degradation kinetics and their potential ability to regenerate bone tissue. This work presents the results of degradation studies of a network of PCL-PHEA and PLA-PHEA polymers that we have previously characterized. Degradation was evaluated after 42 days incubation in phosphate buffered saline and in DMEM culture medium with lipase enzyme (25 IU/ml), and after 14 days in DMEM supplemented with 1% fetal calf serum (FCS) with or without RAW264.7 macrophages in culture. All conditions were carried at 37°C in a humidified atmosphere containing 5% CO2. Samples were cut, weighed (Wo) and incubated for different times and conditions. After each time-point, the samples were washed exhaustively with distilled water, dried under vacuum and weighed (Wt). The samples were placed in acetone for 24 hours to determine swellability. Samples were then removed and weighed (Wht). Degradation was evaluated by calculating the percentage weight loss (%W=(Wo-Wt)x100/Wo) and percent swelling (%Swell=(Wht -W0)x100/W0). These tests demonstrated that degradation by RAW264.7 cells (14 days) produced a greater weight loss to PLA-PHEA (120 vs. 8) compared to enzymatic degradation (42 days). However, enzymatic treatment produced greater swellability (316 vs. 252) than degradation by macrophages. A similar behavior was used PCL-PHEA. Our results demonstrate that the network developed for use in BTE is capable of being degraded by different mechanisms. We also evaluated the hydrophobicity of polymeric membranes by performing surface tension-dependent water contact angle (WCA) measurements. These results demonstrate significant differences between PCL and PLA, and between PLA-PHEA and PLC-PHEA. Biocompatibility of the membranes was also examined by culturing rat bone marrow progenitor cells on the different gels for 14 days, and determining the induction of alkaline phosphatase enzymatic activity (ALP) as a marker of osteoblastic differentiation. After this culture period, good biocompatibility (PLA-PHEA: 153% respect to PLA; PCL-PHEA: 126% respect to PCL) was observed for all matrices. In conclusion, various materials have been obtained showing different rates of enzymatic and macrophagic degradation as well as biocompatibility for bone-derived cells.