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Live cells acquire different fates including apoptosis, necrosis, and senescence in response to stress and stimuli. Rapid and label-free enrichment of live cells from a mixture of cells adopting various cell fates remains a challenge. We developed a ViaChip for high-throughput enrichment of Via ble cells via size-based separation on a multi-stage microfluidic Chip . Our chip takes advantage of the characteristic increase in cell size during cellular senescence and decreases during apoptosis and necrosis, in comparison to their viable and healthy counterparts. The core component of our ViaChip is a slanted and tunable 3D filter array in the vertical direction (z-gap) for rapid and continuous cell sieving. The shape of the 3D filter array is optimized for target cells to prevent clogging during continuous separation. We demonstrated enrichment of live human and mouse mesenchymal stem cells in culture and from live animals, as well as the removal of senescent and necrotic MSCs, respectively, achieving an enrichment efficiency of ~67% with the continuous flow at 1.5 mL/hour. With further improvements in throughput and separation efficiency, our ViaChip could find applications in cell-based drug screening for anti-cancer and anti-aging cell therapies.

Additional file 1. ToF-SIMS characterization of PEGylated biotin-conjugated PLGA nanofibers. Figure S1. Static cell-capture efficiencies of HCT116, MCF7, PC9, HepG2, Huh7, HeLa, and THP1 cell lines on random PLGA nanofiber arrays. HCT116, MCF7: EpCAM-positive cancer cell lines; HeLa, THP1: EpCAM-negative cancer cell lines. Figure S2. Three-dimensional representations of AFM topographic images and root mean square average roughnesses (Rrms) of a random and b aligned PLGA nanofiber arrays. Figure S3. a Cell viability tests for MCF7 cells captured on the control (tissue culture polystyrene, TCPS) and through on-chip (random PLGA nanofiber arrays) and off-chip cell collection (MCF7 cells released from random PLGA nanofiber arrays using the air foam technology). Released cells were washed twice with PBS and incubated for 24 h. Viability was assayed through the fluorescence live/dead staining result, which showed calcein AM (green) for live cells and Eth-1 (red) for dead cells (N = 3). b Live/dead staining image of off-chip cell collection (incubated on TCPS for 3 h).

A poly(dimethylsiloxane) (PDMS)-based functional microfluidic device containing a charged matrix of PDMS pillar arrays grafted with hyperbranched polyglycerols (HPGs) was developed. Samples of PDMS were modified with allylamine plasma to form amine groups on the surface prior to the covalent grafting of succinimdyl ester-functionalized HPGs. The anionic functionality of the PDMS channel matrices was developed by altering the number of carboxyl groups present on the HPGs. The grafting of HPGs onto PDMS plates was investigated via contact angle measurement and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), while the grafting of the inside channel was investigated by electroosmotic flow (EOF) measurements. The charge density on grafted HPG was optimized to minimize the nonspecific protein adsorption and increase the selective capture of positively charged proteins. A proof-of-concept device was fabricated on PDMS and demonstrated that the device selectively captures positively charged protein (avidin) from a mixture of bovine serum albumin (BSA)-avidin at pH 7.4 in phosphate buffered saline (PBS). In order to increase the capture efficiency of the proteins in this PDMS-based device, pillar arrays have been fabricated within the channel. As a demonstration, the new device separated two proteins with an avidin capture efficiency of 100 ± 2.95% per 3 min from a 0.02 mg/ml protein solution (avidin:BSA wt ratio: 1:1). This new microfluidic-based device shows a great deal of promise as a tool for protein capture and analysis.

The reaction kinetics of the formation of LiCoO 2 during solid-state reaction was investigated using a non-isothermal approach at constant heating rates. The conversion ratios of the starting material of LiCoO 2 were calculated from thermogravimetric measurements. Analysis based on the differential method revealed that two diffusion-controlled models described the probable reaction mechanisms. The utilized integral method corroborated the fact that the reaction kinetics of the formation of LiCoO 2 was governed by Ginstling's diffusion-controlled reaction model. The activation energy of the formation of LiCoO 2 was calculated to be 163.6 kJ/mol. A combination of the differential and integral methods was demonstrated to effectively elucidate the reaction kinetics of ceramics and accurately determine the associated kinetic parameters.

A micromachined vibrating membrane is used to remove adsorbed proteins on a surface. A lead zirconate titanate (PZT) composite (3 x 1 x 0.5 mm) is attached to a silicon membrane (2,000 x 500 x 3 microm) and vibrates in a flexural plate wave (FPW) mode with wavelength of 4,000/3 microm at a resonant frequency of 308 kHz. The surface charge on the membrane and fluid shear stress contribute in minimizing the protein adsorption on the SiO(2) surface. In vitro characterization shows that 57 +/- 10% of the adsorbed bovine serum albumin (BSA), 47 +/- 13% of the immunoglobulin G (IgG), and 55.3~59.2 +/- 8% of the proteins from blood plasma are effectively removed from the vibrating surface. A simulation study of the vibration-frequency spectrum and vibrating amplitude distribution matches well with the experimental data. Potentially, a microelectromechanical system (MEMS)-based vibrating membrane could be the tool to minimize biofouling of in vivo MEMS devices.

Lithium cobalt oxide (LiCoO 2 ) powders, utilized as cathode materials in lithium–ion secondary batteries, have been synthesized through the emulsion process. When the emulsion-derived precursors are calcined at elevated temperatures, the amounts of residual Co 3 O 4 and organic species decrease and the crystallinity of LiCoO 2 gradually improves with a rise in the calcination temperature. After calcination at 800 °C for 1 h, monophasic LiCoO 2 powders with a R 3 m structure are successfully obtained. Compared to the traditional solid-state reaction, the emulsion process not only significantly curtails the reaction time to prepare LiCoO 2 , but also reduces the particle size. In the electrochemical test, both the specific discharge/charge capacity and the coulomb efficiency of LiCoO 2 increase with a rise in the calcination temperature. Increasing the calcination temperature results in the formation of pure LiCoO 2 without residual reactants, and also enhances the crystallinity of LiCoO 2 as well as the ordering arrangement of lithium and cobalt cations in the layered structure, thereby facilitating the intercalation and deintercalation of lithium ions. As a result, the combination of the emulsion method with proper calcination processes is highly successful in producing LiCoO 2 powders having large specific capacity and good cyclic stability along with high coulomb efficiency.

The surfactant effects on the microstructure and electrochemical properties of lithium cobalt oxide (LiCoO2) powders prepared from emulsion-derived precursors have been investigated in this study. The single-phase LiCoO2 powders with R 3 m structure are successfully prepared. The crystallinity and particle size of the obtained powders are varied with the amount of the surfactant used for preparing the emulsion solution. Reducing the amount of the surfactant results in improving the crystallinity and slightly decreasing the particle size of LiCoO2 powders. The LiCoO2 powders prepared from the emulsion with a small amount of the surfactant added exhibit high discharge capacity and high coulomb efficiency, as well as good cyclability. The crystallinity of LiCoO2 powders is considered to play an important role in determining the electrochemical properties.

We report a novel nonfouling passivation method using poly(ethylene glycol) (PEG) engraftment on the surfaces of poly(dimethylsiloxane) (PDMS) microfluidic devices sealed with SU-8. To achieve bonding between the PDMS and SU-8 surfaces, the PDMS surface was first functionalized with amines by treatment with 3-aminopropyltrimethoxysilane (APTMS) for subsequent reaction with epoxide functional groups on SU-8 surfaces. To modify the heterogeneous surfaces of the resulting PDMS/SU-8 microfluidic device further, the remaining SU-8 surfaces were amino functionalized using ethylene diamine (EDA), followed by treating both amino-functionalized PDMS and SU-8 surfaces with mPEG-NHS (N-hydroxysuccinimide) through an amine-NHS reaction for facile PEG immobilizations, thus simultaneously modifying both PDMS and SU-8 surfaces in one reaction. Detailed surface analyses such as the water contact angle, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) were conducted to confirm the chemical reactions and characterize the resulting surface properties. To test the efficacy of this surface-modification strategy, we conducted nonspecific protein and particle binding tests using microfluidic devices with and without modifications. The PEG-modified PDMS/SU-8 device surfaces showed a 64.5% reduction in nonspecific bovine serum albumin (BSA) adsorption in comparison to that of the unmodified surfaces and 92.0 and 95.8% reductions in microbead adhesion under both stagnant and flowing conditions, respectively.

An antifouling treatment based on the combined effects of grafted polyethylene glycol (PEG) polymers and the application of vibration is reported. A gold-coated lead zirconate titanate piezoelectric composite was grafted with PEG used as a model substrate. The PEG grafted surfaces were thoroughly characterized by attenuated total reflectance-Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. In vitro protein adsorption onto PEG coated surfaces was studied with and without the application of vibration. Bovine serum albumin (BSA) adsorption onto PEG grafted surfaces followed a similar pattern as reported in literature. However, when piezoelectric vibration was applied on the PEG grafted surface, BSA desorption was observed. At very low graft densities, the vibration significantly reduced the BSA adsorption compared with high PEG graft densities. Theoretical calculations showed that the thickness of PEG layer on the surface was affecting vibration induced protein desorption.

Ultrafine lithium cobalt oxide (LiCoO2) powder with the structure has been successfully prepared by a newly developed water-in-oil emulsion process. This emulsion process not only significantly shortens the reaction time for preparing LiCoO2, but also decreases the particle size of LiCoO2 to submicron order.