PRODUCTION OF BIOCOMPATIBLE AND BIODEGRADA BLE WATER BLOWN POROUS POLYURETHANE SCAFFOLDS FROM PALM OIL-BASED POLYESTER POLYOL FOR TISSUE ENGINEERING

Abstract

Polyurethane is in high demanded in the world, from the range of flexible to rigid, used in industrial and biomedical applications. At present, most of the commercially available polyurethanes are products of petrochemicals. Considering the environmental impact of crude oil and potential carcinogenic effects of petrochemicals, vegetable oil and oleochemicals serves as a candidate to substitute petroleum-based polyols for polyurethane production. In this study, 100% palm oil-based polyester polyol was used to produce biodegradable and biocompatible polyurethane scaffold for tissue engineering applications. The palm oil-based polyester polyols, coded as PPM and PPG, were produced from epoxidised palm olein (EPO) with two different chain length of aliphatic dicarboxylic acids, malonic acid (n= 1) and glutaric acid (n= 3), respectively, under a solvent free and self-catalytic conditions. The optimal reaction conditions were determined through the alteration of molar ratio functionality (epoxy: carboxyl), reaction temperature and reaction time, and monitored by oxirane oxygen content (OOC) and acid value of the reaction mixtures. The optimal conditions for PPM were determined at the functionality molar ratio (epoxy: carboxyl) of 1:1.4, reaction temperature at 140°C and duration of 2 hours to produce PPM with 95% of OOC conversion, low acid value of 1.44 mg KOH/g sample and hydroxyl value of 98.19 mg KOH/g sample. Meanwhile, polyester polyols PPG was optimised at the functionality molar ratio (epoxy: carboxyl) of 1:0.7, reaction temperature at 210°C and duration of 5 hours. The optimised polyester polyols PPG was determined with 86% of OOC conversion, low acid value of 1.33 mg KOH/g sample and hydroxyl value of 60.81 mg KOH/g sample. The physico-chemical properties of the optimised polyester polyols were characterised by viscosity, cloud point and pour point measurements while the chemical structure and molecular weight distribution of the polyols were elucidated by ATR-FTIR, H1-NMR, C13-NMR and GPC. The optimised polyester polyols PPM and PPG were subsequently reacted with isophorone diisocyanate (IPDI) to produce polyurethane scaffolds, coded PU-M and PU-G, respectively, in the presence of glycerol crosslinker, dibutyltin dilaurate catalyst, triethylene diamine catalyst and water as the blowing agent. The effects of water content and isocyanate index were analysed to determine the optimal formulation. All the polyurethane scaffolds produced by PPM and PPG were high in porosity (> 85%) with pore size ranged 35-2165 μm. Polyurethane PU-M produced at isocyanate index 1.2 consisted the highest compression stress of 55 kPa with acceptable tensile strength of 78 kPa and elongation at break of 51%. Meanwhile, polyurethane PU-G produced at isocyanate index of 1.0 exhibited the highest tensile strength of 111 kPa with compression stress of 64 kPa and elongation at break of 45%. The biodegradability of the polyurethane scaffolds was evaluated by in vitro degradation study using porcine lipase solution for 29 days. The polyurethane scaffolds demonstrated controlled degradation rate ranged from 7-59% of mass loss and high water uptake level ranged from 126%-447%. The insignificant changes of pH of the medium used throughout the degradation process had assured the potential of polyurethane scaffolds in biomedical applications. In terms of cytocompatibility, the polyurethane scaffolds were evaluated through MTT assay on MG-63 human osteosarcoma cells via indirect contact method. The polyurethane scaffolds showed the cell viability ranged 42-70% compared to the 102% cell viability of feeding catheter (positive control), 2% cell viability of urinary catheter (negative control) and 9% cell viability of PU-ref after 1 day of incubation. For cell adhesion test, polyurethane allowed MG-63 cells adhesion after 12 hours of incubation and proliferation after 24 hours incubation.