Swelling Performance Evaluation for Microspheres & Microneedles

Swelling test is one of the basic testing methods for microneedles and microspheres material properties. The purpose is to test the ability of microneedles and microspheres materials to absorb or release drugs as substrates for sustained drug release systems. The swelling tests of microspheres and microneedles are provided by CD Formulation, and the morphological changes during drug release can be reflected back. This test will help our customers effectively develop drug formulations, as well as formulations of microspheres and microneedles. In the process of product development, the swelling rate and swelling degree of microspheres and microneedles should be strictly controlled, so as to effectively achieve the purpose of effective drug release.

Fig.1 MN swelling and drug release. (Yadav et al., 2022)

How to Perform Swelling Test

Microneedle swelling test

The microneedle swelling test method is to test the swelling rate of microneedle materials in solution or deionized water required by the experiment by controlling different temperature or pH values and different time lengths and other conditions.

The designed microneedles have swelling properties and can achieve slow drug release. In order to evaluate the swelling characteristics of the micronedles, the dry micronedles were first weighed (m₀) using an electronic balance, and then placed in PBS buffer (pH=7.4) at 37℃ for swelling experiments. Remove the microneedles from the solution at regular intervals, drain excess water from the surface with filter paper, and weigh the mass. Calculate the swelling rate Q of microneedles at each moment.

Q=(m_t-m₀)/ m₀*100%

Where, m_t -- quality of microneedle patch at different times;

m₀ -- Dry microneedle patch quality.

With time as the X-axis and weight growth rate of the microneedles at each time point as the Y-axis, the swelling degree and swelling rate of the microneedles were investigated by plotting.

Microsphere swelling test

The swelling rate of microspheres was measured by gravimetric method: a certain amount of microsphere powder was weighed, and the pH buffer solution was slowly added to the microsphere powder until the water was no longer absorbed. The excess water was carefully absorbed with filter paper and then weighed. Swelling rate is calculated according to the following formula:

Swelling rate S=(W_s-W_d)/Wdx100%

Where :W_s- wet weight of microsphere (g)

W_d- microsphere dry weight (g)

Factors affecting the swelling of microspheres & microneedles

To investigate the effect of the proportion of supplementary materials on the swelling degree and swelling rate of microspheres and microneedles in the preparation process, so as to help customers better carry out drug loading of microspheres and microneedles.

Morphology test for microspheres & microneedles

In the process of swelling test, the morphology of microspheres and microneedles can be measured by CD Formulation, and the morphology changes of products after swelling at different times can be studied. These tests provide intuitive feedback on swelling conditions, and according to swelling conditions, product formulation can be adjusted.

Features of Swelling Performance Evaluation

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