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The development of a simple, portable, and cost-effective plasma separation platform for blood biochemical analysis is of great interest in clinical diagnostics. We represent a plasma separation microfluidic device using microspheres with different sizes as the separation barrier. This plasma separation device, with 18 capillary microchannels, can extract about 3 μL of plasma from a 50 μL blood sample in about 55 min. The effects of evaporation and the microsphere barrier on the plasma biochemical analysis results were studied. Correction factors were applied to compensate for these two effects. The feasibility of the device in plasma biochemical analysis was validated with clinical blood samples. [ABSTRACT FROM AUTHOR]

Janus droplets can function as excellent templates for fabricating physically and chemically anisotropic particles. Here, we report new surfactant-laden Janus droplets with curvature controllability and enhanced stability against coalescence, suitable for fabricating shape-anisotropic polymer microparticles. Using a microfluidic flow-focusing device on a glass chip, nanoliter-sized biphasic droplets, comprising an acrylate monomer segment and a silicone-oil (SO) segment containing a surfactant, were produced in a co-flowing aqueous polyvinyl alcohol (PVA) solution. At equilibrium, the droplets formed a Janus geometry based on the minimization of interfacial energy, and each of the two Janus segments were uniform in size with coefficient-of-variation values below 3%. By varying the concentration of the surfactant in the SO phase, the curvature of the interface between the two lobes could be shifted among concave, planar, and convex shapes. In addition, the Janus droplets exhibited significantly improved stability against coalescence compared with previously reported Janus droplets carrying no surfactant that coalesced rapidly. Finally, via off-chip photopolymerization, concave-convex, planar-convex, and biconvex lens-shaped particles were fabricated. [ABSTRACT FROM AUTHOR]

Spherical biosamples such as immunobeads, cells, and cell aggregates have been widely used in bioapplications. The bioactivity of individual spherical biosamples in highly sensitive assays and individual analyses must be evaluated in a high-throughput manner. Electrochemiluminescence (ECL) imaging was recently proposed for the high-throughput analysis of diffusive molecules from spherical biosamples. ECL imaging involves the placing of spherical biosamples on a flat electrode filled with a solution. The biosamples produce (or consume) biological/chemical molecules such as H 2 O 2 and O 2 , which diffuse to form a concentration gradient at the electrode. The ECL signals from the molecules are then measured to obtain the concentration profile, which allows the flux to be estimated, from which their bioactivities can be successfully calculated. However, no studies on theoretical approaches for spherical biosamples on flat surfaces have been conducted using ECL imaging. Therefore, this paper presents a novel spherical diffusion theory for spherical biosamples on a flat surface, which is based on the common spherical diffusion theory and was designated as the extended spherical diffusion theory. First, the concepts behind this theory are discussed. The theory is then validated by comparison with a simulated analysis. The resulting equation successfully expresses the concentration profile for the entire area. The glucose oxidase activity in the hydrogel beads is subsequently visualized using ECL imaging, and the enzymatic product flux is calculated using the proof-of-concept theory. Finally, a time-dependent simulation is conducted to fill the gap between the theoretical and experimental data. This paper presents novel guidelines for this analysis.

Micro- and nanoparticles are of great interest because of their potential for trafficking into the body for applications such as low-fouling coatings on medical devices, drug delivery in pharmaceutics and cell carriers in regenerative medicine strategies. Particle production often relies on the use of surfactants to promote stable droplet formation. However, the presence of residual surfactant has been shown to complicate the surface chemistry and resultant properties. When forming particles from polymerizable monomer droplets, these polymeric surfactant chains can become physically entangled in the particle surface. Due to the key role of the outermost layers of the surface in biomaterial interactions, the surface chemistry and its influence on cells needs to be characterized. This is the first study to assess surfactant retention on microfluidic produced particles and its effect on bacterial attachment; surfactant contaminated microparticles are compared with flat films which are surfactant-free. Polymeric microparticles with an average diameter of 76 ± 1.7 μm were produced by using a T-junction microfluidic system to form monomer droplets which were subsequently photopolymerized. Acrylate based monomer solutions were found to require 2 wt% PVA to stabilize droplet formation. ToF-SIMS was employed to assess the surface chemistry revealing the presence of PVA in a discontinuous layer on the surface of microparticles which was reduced but not removed by solvent washing. The effect of PVA on bacterial ( Pseudomonas aeruginosa ) attachment was quantified and showed reduction as a function of the amount of PVA retained at the surface. The insights gained in this study help define the structure-function relationships of the particulate biomaterial architecture, supporting materials design with biofilm control., Competing Interests: The authors declare no competing financial interest., (This journal is © The Royal Society of Chemistry.)