The use of biodegradable materials have received great attention in biomedical applications including coronary stent. Biodegradable stents were developed to overcome the limitations of current metallic stents such as late in-stent restenosis and permanently caging the vessel. Most of the materials used in the fabrication of biodegradable stents are synthetic polymers and bio-corrodible metals. However, concern related to synthetic polymers include their long term effects in the body. Thus, natural polymers have been introduced to overcome the limitations of synthetic polymers. Upholding promises, naturally renewable starch based polymers have shown great potential as biodegradable materials. Besides, starch having unique properties such as biodegradable, non-toxic and biocompatible makes them useful for a wide variety of biomedical applications. This study is motivated by a gap in the current knowledge in starch biomaterials. Although starch has been widely researched in various biomedical applications, in general their applications in coronary stent is still in early development that requires further study. Therefore, this study aimed to fabricate potato starch composites film through solution casting technique utilizing hybrid bentonite and hydroxyapatite (HA) nanofillers to enhance mechanical and biocompatibility properties. The potato starch composites films were prepared by mixing two different solutions which is bentonite/HA and starch solutions. The bentonite/HA solution was first prepared by mechanical mixing at 1000 rpm for 30 minutes followed by sonication mixing for 30 minutes prior to mixing with starch solution. Starch solution preparation involved mixing potato starch and glycerol together with bentonite/HA solution in water bath by mechanical stirrer for 30 minutes followed by drying the mixture in an oven overnight to form starch composites film. Prior to potato starch hybrid composites film fabrication, starch/glycerol film at different mixing temperature and starch/bentonite composites film were initially fabricated to find the optimum glycerol, mixing temperature and bentonite content. The effect of glycerol addition, mixing temperature, bentonite and HA addition in potato starch films were evaluated through tensile, physical, morphology and functional group analyses. An in vitro test using simulated body fluid (SBF) and biocompatibility assessment were also performed to evaluate the bioactivity and biocompatibility properties of potato starch composites film. The tensile test results showed that starch film with 30 wt% glycerol and 15 wt% bentonite at 85 °C mixing temperature exhibited the highest tensile strength, thus were chosen in fabrication of starch hybrid composites with various content of HA (1, 5, 10, 15 and 20 wt%). Results showed that, starch hybrid composites film with 5 wt% HA demonstrated the highest tensile strength value of 4.36 MPa compared to neat starch and starch/bentonite composites. Furthermore, the evidence from SEM and TEM studies showed better dispersion and sufficient reinforcement obtained from starch hybrid composites containing 5 wt% HA which supported the tensile test result. Meanwhile, the in vitro test shows that the incorporation of HA into starch/bentonite composites improves the bioactivity of the starch hybrid composites. Besides, it was also found that starch film containing bentonite and HA exposed to human umbilical vein endothelial cells (HUVEC) may promote HUVEC growth on its surface compared to neat starch film which showed lack of cell viability. Among the hybrid combination composites, the film with 5 wt% HA substitution shows biocompatibility and able to stimulate cell proliferation, which suggests suitability and promise to be used in coronary stent applications.
