Rapid purification of sub-micrometer particles for enhanced drug release and microvesicles isolation

Efficient separation of sub-micrometer synthetic or biological components is imperative in particle-based drug delivery systems and purification of extracellular vesicles for point-of-care diagnostics. Herein, we report a novel phenomenon in spiral inertial microfluidics, in which the particle transient innermost distance (Dinner) varies with size during Dean vortices-induced migration and can be utilized for small microparticle (MP) separation; aptly termed as high-resolution Dean flow fractionation (HiDFF). The developed technology was optimized using binary bead mixtures (1–3 μm) to achieve ~100- to 1000-fold enrichment of smaller particles. We demonstrated tunable size fractionation of polydispersed drug-loaded poly(lactic-co-glycolic acid) particles for enhanced drug release and anti-tumor effects. As a proof-of-concept for microvesicles studies, circulating extracellular vesicles/MPs were isolated directly from whole blood using HiDFF. Purified MPs exhibited well-preserved surface morphology with efficient isolation within minutes as compared with multi-step centrifugation. In a cohort of type 2 diabetes mellitus subjects, we observed strong associations of immune cell-derived MPs with cardiovascular risk factors including body mass index, carotid intima-media thickness and triglyceride levels (P<0.05). Overall, HiDFF represents a key technological progress toward high-throughput, single-step purification of engineered or cell-derived MPs with the potential for quantitative MP-based health profiling. Particles sorting due to vortex patterns inside microfluidic devices can enhance drug release from polymer agents and aid microvesicles recovery from whole blood. When liquids flowing along a straight tube encounter a bend, the change in pressure generates secondary rotational fluid motion known as Dean vortices. Han Wei Hou at Singapore's Nanyang Technological University and colleagues have exploited this effect to realize high-throughput micro- and nanoparticles separation based on small size differences. The team's technology uses spiral microchannels to sort and enrich smaller microparticles up to 1,000 times. Trials with drug-loaded copolymer microparticles revealed sub-micron delivery agents greatly improved tumor cell growth inhibition due to their quicker release properties. In addition, this approach enabled single-step isolation of membrane-based microvesicles from whole blood directly, within minutes instead of hours with typical centrifugations. In this work, we report a novel Dean vortices-induced particle migration phenomenon in spiral inertial microfluidics, which can be utilized for high throughput size-based separation of sub-micrometer synthetic or biological components, aptly termed as high-resolution Dean flow fractionation (HiDFF). We demonstrated enhanced drug release effects in particle-based drug delivery system, as well as single-step purification of circulating extracellular microvesicles from whole blood for rapid immune and vascular health profiling.