Preparation And Property Of Polyurethane Microcapsules Based On A Template-removal Method

The microcapsules based on a sacrificial-template method has attracted considerable attention because of their high surface areas, unique pore structures, tunable particle morphology and well controllable size and shape. Such method has been widely used to fabricate multifunctional microcapsules and other micro-structured materials. However, the diameter of microcapsules (about several micrometers) is relatively big compared with the size of blood capillary (about 3 μm for the smallest) in the body, leading to a barrier to their potential applications in vivo. One of the solutions is to fabricate elastic microcapsules which may possess shape deformation properties like red blood cells.Polyurethane (PU) is widely used in biomaterials and shape memory fields due to its good elasticity and blood compatibility, which is a potential material for the fabrication of elastic microcapsules which possess good deformation and recovery property. So we combine the advantages of template method to fabricate PU microcapsules with well controllable size and shape, and further characterize the deformation and recovery property. This kind of PU capsules may find potential applications in biomedical field.When the microcapsules are used in the body, they’re inevitable to interact with the cells inside. As we all know, the bacteria in nature have diverse shapes like cylinder, rod, spiral and so on which endow them with special functions. Recently, it has been reported that the physical properties like shape, size and mechanical property of capsules have great influences on their interaction with cells. Among them, the influence of shapes has received much more attention, and people started to fabricate microcapsules with different shapes for further experiments. While the influence of shape on the biological process is still not clear and some results are inconsistent.In this work, porous CaCO3 particles were used as the template to adsorb PU in N,N-dimethylformamide (DMF) solution, followed by hexamethylenene diisocyanate (HDI) crosslinking and removing the core to obtain the PU microcapsules. The results showed that the PU capsules could be well dispersed in water, and the hydrophobic interiors facilitate the loading of hydrophobic substances such as drugs and dyes. Their deformation and recovery behaviors were investigated after being forced to flow through a microchannel. Due to their good elasticity, more than 82% squeezed PU capsules could recover their original spherical shape even at a high deformation ratio of 32%.Furthermore, the PU microcapsules with different shapes were fabricated by using the templates of corresponding shapes. The scanning electron microscope (SEM) results showed that the PU capsules could remain their original shapes and size after the cores were removed, which are consistent with the confocal laser scanning microscope (CLSM) results. Then the capsules were incubated with HepG2 cells and RAW 246.7 cells to characterize the influence of shapes on the cell uptake. It was found that the uptake amount and rate of discal capsules were larger and faster than those of the spherical ones. Compared with the HepG2 cells, the RAW 246.7 cells could intermediate the same type of capsule with a larger amount and faster rate.