Biomaterials used in tissue regeneration processes represent a promising option for the versatility of its physical and chemical characteristics, allowing for assisting or speeding up the repair process stages. This research has characterized a polyurethane produced from castor oil monoacylglyceride (Ricinus communis L) and tested its effect on reconstructing bone defects in rat calvaria, comparing it with commercial castor oil polyurethane. The characterizations of the synthesized polyurethane have been performed by spectroscopy in the infrared region with Fourier transform (FTIR); thermogravimetric analysis (TG/DTG); X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). For the in vivo test, 24 animals have been used, divided into 3 groups: untreated group (UG); control group treated with Poliquil® castor polyurethane (PCP) and another group treated with castor polyurethane from the Federal University of Piauí - UFPI (CPU). Sixteen weeks after surgery, samples of the defects were collected for histological and histomorphometric analysis. FTIR analysis has shown the formation of monoacylglyceride and polyurethane. TG and DTG have indicated thermal stability of around 125 °C. XRD has determined the semi-crystallinity of the material. The polyurethane SEM has shown a smooth morphology with areas of recesses. Histological and histomorphometric analyzes have indicated that neither CPU nor PCP induced a significant inflammatory process, and CPU has shown, statistically, better performance in bone formation. The data obtained shows that CPU can be used in the future for bone reconstruction in the medical field.

The development of ‘smart’ scaffolds has achieved notoriety among current prospects for bone repair, especially for chronic osteopathy, such as osteoporosis. Millions of individuals in the world suffer from poor bone healing due to osteoporosis. The objective of this work was to produce and characterize castor polyurethane (PU) scaffolds (Ricinus communis L.) and evaluate its in vitro biocompatibility with stem cells and osteoinductive effect in vivo on bone failures in a leporid model of osteoporosis. The material was characterized using Fourier-transform infrared spectroscopy, thermogravimetric analysis, SEM, and porosity analysis. Then, the biocompatibility was assessed by adhesion using SEM and cytotoxicity in a 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2H-tetrazolium assay. The osteoinductive effect in vivo was determined in bone defects in rabbit tibias (Oryctolagus cuniculus) submitted to castor PU scaffold, castor PU scaffold associated with stem cells, and negative control, after four and eight weeks, evaluated by computed microtomography and histopathology. The scaffolds were porous, with an average pore size of 209.5 ± 98.2 µm, absence of cytotoxicity, and positive cell adhesiveness in vitro. All the animals presented osteoporosis, characterized by multifocal osteoblastic inactivity and areas of mild fibrosis. There were no statistical differences between these treatments in the fourth week of treatment. In the eighth week, the treatment with castor PU scaffold alone induced more significant bone formation when compared to the other groups, followed by treatment with an association between castor PU scaffold and stem cells. The castor PU scaffold was harmless to cell culture, favoring cell adhesiveness and proliferation, in addition to inducing bone neoformation in osteoporotic rabbits.

To analyze the biocompatibility of the scaffold produced from a natural polymer derived from castor oil through hemolytic activity and antimicrobial activity, to enable the clinical application. Three in vitro tests were performed: Hemolytic activity test -Polymer partially dissolved in contact with blood agar; Hemolytic activity test in sheep's blood -Polymer extract with red blood cells solution; Antimicrobial activity test -Solid polymer in direct contact with E. Coli and S. Aureus. For hemolytic tests, none of the samples showed hemolysis. Negative hemolytic activity is a good indicator, as the maintenance of the blood clot in the area of the lesion is essential for the formation of new tissue. For the antimicrobial activity test, no significant activity was observed against the bacteria used. The polymer is not toxic to red blood cells, being viable for clinical application as a matrix for tissue regeneration.

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