Purifying nanoparticles into monodisperse fractions is a crucial step in understanding their physical properties and minimizing variability in biological applications. The lack of uniformity in nanoparticle samples can lead to inconsistent results, making it challenging to draw meaningful conclusions. While various methods have been explored for purifying "hard" nanoparticles, few studies have focused on "soft" nanoparticles like polymersomes.
Polymersomes, with their unique physico-chemical and mechanical properties, are attractive for biological and medical applications. However, their self-assembly process inherently leads to broad size distributions and high variability in morphology. This heterogeneity can result in a mixture of spherical vesicles, tubes, and genus structures, as well as non-vesicular structures like micelles. To address this challenge, we compared four complementary techniques for separating polymersomes by size and shape: cross-flow filtration (CFF), differential centrifugation (DC), size exclusion chromatography (SEC), and density gradient centrifugation (DGC).
the results show that each technique has its advantages and disadvantages. CFF efficiently separates micelles from polymersomes, possibly due to a combination of size exclusion and differential fluid dynamics. However, it cannot be used to separate sub-populations of polymersomes by size. DC and SEC enable separation of polymersomes into distinct size fractions, but result in sample concentration loss. DGC, on the other hand, achieves shape-based separation by exploiting differences in membrane packing density.
they found that the different shape of polymersomes corresponds to changes in the density of membrane packing, providing the means for their separation by the DGC-based method. This approach allows for the separation of polymersomes into distinct fractions based on their shape, which is essential for understanding their physical properties and biological behavior.
By combining these techniques, we can develop efficient purification protocols for polymersomes and other nanoparticles. This study demonstrates the importance of purification in producing consistent and reproducible results in biological experiments and improving application development in medicine and drug delivery. The ability to purify nanoparticles into monodisperse fractions will enable researchers to better understand their physical properties and behavior, ultimately leading to the development of more effective nanoparticle-based therapies.
