Bio-inspired liquid crystal gel induction via nano-hydroxyapatite mesogens: Viscoelastic and hemostasis regulation under bone remodeling pH and temperature control

In this work, a liquid crystal mesophase as a potential bone-repairing booster has been induced from a polyacrylic acid (PAAc) gel loaded with synthetic hydroxyapatite nanoparticles (nHA) under physiological conditions of pH and temperature that resemble the early stages of bone formation. Dynamic processes at the microscale in biological systems require a material capable of behaving following a specific order and fluency. Besides, they must fulfill conditions such as biocompatibility and good mechanical properties. Our study aimed to obtain new data about the safety, hemostasis, biocompatibility (activated partial thromboplastin time (APTT) test, prothrombin time (PT) test, lactate dehydrogenase (LDH) test, red blood cell morphology observation, hemolysis percentage) and physicochemical/mechanical behavior (Attenuated Total Reflection (ATR), Infrared spectroscopy and rheological assays) of nanoparticles, and materials built with them. Both systems have shown biocompatibility with red blood cells and adequate flow properties, demonstrating promising qualities for applicability. The formation of lyotropic liquid crystals at physiological conditions was evaluated with crossed polaroids microscope with a temperature control plate. The formation of these structures under bone remodeling conditions shows the potential application of PAAc-nHA materials. In literature, the study of materials applied as bone fillers is mainly focused on mechanical and osteoblasts compatibility assays. However, the hematological effect, consequences on the coagulation cascade, the integrity of cell membranes, and hemolysis percentage have not been addressed thoroughly. The strength of our work is focused on considering these aspects when tridimensional arrangements essential for bone formation are formed.