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 (D inner ) 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 (Po0.05). Overall, HiDFF represents a key technological progress toward highthroughput, single-step purification of engineered or cell-derived MPs with the potential for quantitative MP-based health profiling. NPG Asia Materials (2017) 9, e434; doi:10.1038/am.2017.175; published online 29 September 2017 INTRODUCTIONEnabling technologies for continuous, size-based separation of submicrometer engineered or biological components are highly desirable in clinical applications, such as particle-based drug delivery systems 1 and the purification of extracellular vesicles in clinical diagnostics. 2 In microparticle fabrication, conventional 'bottom-up' self-assembly emulsification techniques yield a broad particle size distribution, which can affect the drug release kinetics and biotransport in blood. 3,4 Although well-controlled and monodisperse particles can be produced by 'top-down' approaches using specific lithographic techniques 5,6 and microfluidics, 7,8 microfabricated particles are prone to damage during mechanical harvesting, a problem further aggravated at the smaller/nanoscale level. Similarly, microfluidic synthesis of drug-loaded polymeric particles requires compatible drug/surfactant chemistry with additional steps to remove solvent prior use. Developing novel tools to achieve tunable size fractionation of polydispersed synthetic particles would enable optimal biodistribution and controlled drug release. Such technologies also facilitate physical isolation of smaller biological targets (o2 μm) including platelets, microbes and extracellular vesicles in a label-free manner for unbiased downstream analysis.

Background: The bio lm way of life is a common strategy for bacteria to adapt and gain tolerance towards antibiotic treatments. Up to 80% of all infections are bio lm-mediated and they are often challenging to treat as the underlying bacterial cells can become 100 -1000-fold more tolerant towards antibiotics. Antibiotic-loaded nanoparticles have gained traction as a potential drug delivery system to treat bio lm infections. Speci cally, lipid-coated hybrid nanoparticles (LCHNPs) were investigated on their capability to deliver antibiotics into bio lms. In this study, LCHNPs composed of a poly(lactic-co-glycolic acid) (PLGA) core and dioleoyl-3-trimethylammonium propane (DOTAP) lipid shell were developed and loaded with vancomycin (Van). In vitro antibacterial and antibio lm tests were performed to evaluate the antimicrobial e cacy of the LCHNPs.Results: LCHNPs were successfully fabricated with high vancomycin encapsulation e ciency of 48.66%and loading e ciency of 72.99 µg/mg. DOTAP was determined to be successfully coated on the PLGA core by measuring the ζ-potential of the nanoparticles. LCHNPs had a positive ζ-potential of +36.13 mV which contrasted signi cantly from the ζ-potential of -36.83 mV of bare PLGA nanoparticles (PLGANPs). LCHNPs exhibited enhanced antibacterial effects against planktonic Staphylococcus aureus USA300 cells, with at least 6-fold reduction in minimum inhibitory concentration when compared against Free-Van and Van-PLGANPs. When used to treat USA300 bio lms, Van-LCHNPs eradicated up to 99.99% of the underlying bio lm cells, an effect which was not observed for Free-Van and Van-PLGANPs. Finally, we showed that by possessing a robust DOTAP shell, LCHNPs were able to penetrate deeply into the bio lms.Conclusion: LCHNPs were shown to display remarkable antimicrobial e cacy towards both planktonic and bio lm cells as the presence of the lipid shell enhanced the interactions with bacterial cells and penetration into bio lms. More work could be done to understand nanoparticle-bio lm interactions; this would help to optimize the LCHNPs further to treat bio lm infections successfully.

Microparticulate systems composed of biodegradable polymers, such as poly(d,l-lactic-co-glycolic acid) (PLGA), are widely used for controlled release of bioactive molecules. However, the acidic microenvironment within these microparticles, as they degrade, has been reported to perturb the configuration of most encapsulated proteins. In addition, these polymer particles are also reported to suffer from unrealistically slow and incomplete release of proteins. To address these drawbacks, hollow PLGA microparticles are fabricated through a novel one-step oil-in-water emulsion solvent evaporation technique, by capitalizing on the osmotic property of an osmogen. The effects of fabrication para-meters on particle size and morphology, i.e., volume space of hollow cavity and shell thickness, are also studied. These hollow microparticles are subsequently loaded with bovine insulin microcrystals. It is shown that insulin release profiles can be tuned by simply changing the amount of osmogen in the formulation. At the same time, these hollow microparticles are shown to be effective in maintaining the bioactivity of the encapsulated protein.

Enterococcus faecalis ( E. faecalis ) biofilms are implicated in endocarditis, urinary tract infections, and biliary tract infections. Coupled with E. faecalis internalization into host cells, this opportunistic pathogen poses great challenges to conventional antibiotic therapy. The inability of ampicillin (Amp) to eradicate bacteria hidden in biofilms and intracellular niches greatly reduces its efficacy against complicated E. faecalis infections. To enhance the potency of Amp against different forms of E. faecalis infections, Amp was loaded into Lipid-Polymer hybrid Nanoparticles (LPNs), a highly efficient nano delivery platform consisting of a unique combination of DOTAP lipid shell and PLGA polymeric core. The antibacterial activity of these nanoparticles (Amp-LPNs) was investigated in a protozoa infection model, achieving a much higher multiplicity of infection (MOI) compared with studies using animal phagocytes. A significant reduction of total E. faecalis was observed in all groups receiving 250 μg/mL Amp-LPNs compared with groups receiving the same concentration of free Amp during three different interventions, simulating acute and chronic infections and prophylaxis. In early intervention, no viable E. faecalis was observed after 3 h LPNs treatment whereas free Amp did not clear E. faecalis after 24 h treatment. Amp-LPNs also greatly enhanced the antibacterial activity of Amp at late intervention and boosted the survival rate of protozoa approaching 400%, where no viable protozoa were identified in the free Amp groups at the 40 h postinfection treatment time point. Prophylactic effectiveness with Amp-LPNs at a concentration of 250 μg/mL was exhibited in both bacteria elimination and protozoa survival toward subsequent infections. Using protozoa as a surrogate model for animal phagocytes to study high MOI infections, this study suggests that LPN-formulated antibiotics hold the potential to significantly improve the therapeutic outcome in highly complicated bacterial infections.

The cumulative release of peptide can be significantly improved, and the bioactivity can be better preserved by simply using h-MPs instead of s-MPs as carriers.