Microspheres are particulate dispersions of drugs dispersed or adsorbed in polymeric matrixes. There are many carrier materials for the preparation of microspheres, mainly divided into natural polymer microspheres and synthetic polymer microspheres. In the process of application, the mechanical properties of microspheres are the key factors affecting their effectiveness, so the mechanical properties of microspheres need to be tested.
CD Formulation can test the mechanical property indexes of microspheres, such as: determination of force-displacement curve, microsphere rupture strength, rigidity of microspheres, microsphere extrusion test, microsphere pressure resistance test, etc. In the process of microsphere development, the mechanical properties of microspheres in use can be analyzed by using the high-precision mechanical analysis instrument of microsphere strength tester.
CD Formulation can provide different types of mechanical property tests according to the different applications of microspheres, including extrusion, rupture strength, internal pressure, etc., to help customers analyze the strength of external forces that the microspheres can withstand and optimize the formulation of microspheres based on these data.
For the determination of force-displacement curve, silicon thermal oxide sheet was chosen as the rigid substrate. The silicon thermal oxides were hydrophilized with concentrated sulfuric acid/hydrogen peroxide solution, and the microspheres were dispersed on the surface of the substrate by spin coating method. The two-dimensional morphology of the samples was measured by AFM, and the force-displacement curves of the samples were recorded. The data of the fitted force-displacement curves were analyzed by software and the compressive Young's modulus of the samples was calculated according to the elastomechanical contact model.
In order to avoid the influence of different particle sizes on the mechanical properties of the microspheres, the microspheres were screened before the test, and those with particle sizes around 200-300 μm were selected for the extrusion test. In order to avoid the chance of microsphere samples, 30 samples were randomly selected for the test and the force changes of the obtained microspheres were plotted.
In characterizing the mechanical properties of microspheres, the rupture force of microspheres reflects the limit of force that the microspheres can withstand. The rigidity of microspheres of different structures is investigated by quantifying the statistical analysis of the deformation of microspheres when they are ruptured by external forces. The ratio of the deformation of the microsphere to the intact microsphere at the time of rupture is called the rupture deformation rate.
The microsphere internal pressure measurement device uses a microsphere high-temperature and high-pressure inflation system. The device is mainly composed of vacuum system, high pressure gas source, control part, inflation chamber and gas circuit. The microspheres to be measured are put into the inflating chamber in order, and under vacuum conditions, the procedure is warmed up to a certain temperature and then charged with H2, which is kept under constant temperature and external pressure for a certain time. After natural cooling down to room temperature, the microspheres are removed to observe whether the microspheres are ruptured, and the gas pressure inside the intact microspheres is measured, then the pressure is increased and then inflated and measured until all the microspheres are ruptured. Record the gas pressure inside the sphere measured before the microspheres rupture.
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