Dynamic fabrication of microfluidic systems for particles separation based on optical projection lithography.

Microfluidic systems are widely used for applications in biology, medicine and chemistry. Particles separation by microfluidics is a scientific subject that requires ongoing research efforts. In this article, we demonstrate a micropillar-based particles separator fabricated using digital micromirror device (DMD)-based optical projection lithography from the perspectives of theory, design, simulation and experiments. Micropillars can be fabricated with customized shapes and sizes which shows high flexible and efficient. The particles separator employs the physical separation of a cylindrical array, a rectangular array, or a triangular array to separate particles. The simulation and experiment results indicate that the device with different micropillars could achieve separation of 20 and 200 µm polystyrene microspheres. Furthermore, the separation efficiency depended on flow rate and the shape of micropillars. All the results can be used to support the redesign of microfluidic structures to address particles separation needs.

Recent advances in microfluidic technologies for separation of biological cells.

Cell separation has always been a key topic in academic research, especially in the fields of medicine and biology, due to its significance in diagnosis and treatment. Accurate, high-throughput and non-invasive separation of individual cells is key to driving the development of biomedicine and cellular biology. In recent years, a series of researches on the use of microfluidic technologies for cell separation have been conducted to solve bio-related problems. Hence, we present here a comprehensive review on the recent developments of microfluidic technologies for cell separation. In this review, we discuss several cell separation methods, mainly including: physical and biochemical method, their working principles as well as their practical applications. We also analyze the advantages and disadvantages of each method in detail. In addition, the current challenges and future prospects of microfluidic-based cell separation were discussed.

Hydrogen sulfide alleviates myocardial collagen remodeling in association with inhibition of TGF-ß/Smad signaling pathway in spontaneously hypertensive rats.

The study was designed to explore the role and possible mechanisms of hydrogen sulfide (H2S) in the regulation of myocardial collagen remodeling in spontaneously hypertensive rats (SHRs). We treated nine-week-old male SHRs and age- and sex-matched Wistar-Kyoto rats (WKYs) with NaHS (90 µmol/kg(-1)·day(-1)) for 9 wks. At 18 wks, plasma H2S, tail arterial pressure, morphology of the heart, myocardial ultrastructure and collagen volume fraction (CVF), myocardial expressions of collagen I and III protein and procollagen I and III mRNA, transforming growth factor-ß1 (TGF-ß1), TGF-ß type I receptor (TßR-I), type II receptor (TßR-II), p-Smad2 and 3, matrix metalloproteinase (MMP)-13 and tissue inhibitors of MMP (TIMP)-1 proteins were determined. TGF-ß1-stimulated cultured cardiac fibroblasts (CFs) were used to further study the mechanisms. The results showed that compared with WKYs, SHRs showed a reduced plasma H2S, elevated tail artery pressure and increased myocardial collagen, TGF-ß1, TßR-II, p-Smad2 and p-Smad3 expressions. However, NaHS markedly decreased tail artery pressure and inhibited myocardial collagen, TGF-ß1, TßR-II, p-Smad2 and p-Smad3 protein expressions, but H2S had no effect on the expressions of MMP-13 and TIMP-1. Hydralazine reduced blood pressure but had no effect on myocardial collagen, MMP-13 and TIMP-1 expressions and TGF-ß1/Smad signaling pathway. H2S prevented activation of the TGF-ß1/Smad signaling pathway and abnormal collagen synthesis in CFs. In conclusion, the results suggested that H2S could prevent myocardial collagen remodeling in SHR. The mechanism might be associated with inhibition of collagen synthesis via TGF-ß1/Smad signaling pathway.

Flexible Patterned Electrohydrodynamic Jet Printing Using Orthogonal Deflection Electrodes.

Electrohydrodynamic jet (E-Jet) printing technology provides unmatched advantages in the fabrication of patterned micro/nanostructures. However, the rapid jets generated during printing can lead to localized droplet accumulation on complex structures due to the relatively slow motion control achieved with motorized translation stages, resulting in distorted patterns. To address this challenge, we introduce two jet-deflecting electrodes orthogonally placed on each other, which can rapidly change the electric field in the vicinity of the jet and thus flexibly adjust the flight trajectory of the fast jet to avoid the region where droplets have been deposited. In this way, the jet droplets are precisely controlled to generate high-fidelity microstructures with arbitrary predefined patterns on the stationary substrate. The maximum deflection distance of the jet droplets reaches several hundred microns. Furthermore, the positioning error of the printed structure is less than 3%. Moreover, we successfully obtained a diverse range of complex patterns by combining this technique with stage motion. This innovative printing technology not only enables the fabrication of complex patterned structures with high fidelity but also opens up exciting possibilities for new applications that require complete control of fast droplet positioning.

4D Printing: A Review on Recent Progresses.

Since the late 1980s, additive manufacturing (AM), commonly known as three-dimensional (3D) printing, has been gradually popularized. However, the microstructures fabricated using 3D printing is static. To overcome this challenge, four-dimensional (4D) printing which defined as fabricating a complex spontaneous structure that changes with time respond in an intended manner to external stimuli. 4D printing originates in 3D printing, but beyond 3D printing. Although 4D printing is mainly based on 3D printing and become an branch of additive manufacturing, the fabricated objects are no longer static and can be transformed into complex structures by changing the size, shape, property and functionality under external stimuli, which makes 3D printing alive. Herein, recent major progresses in 4D printing are reviewed, including AM technologies for 4D printing, stimulation method, materials and applications. In addition, the current challenges and future prospects of 4D printing were highlighted.

Dynamically directing cell organization via micro-hump structure patterned cell-adhered interfaces.

Cell adhesion plays an important role in cell communication, organ formation and tissue maintenance. Spatial microstructure patterning has the capability to regulate cell functions such as cell adhesion and cell proliferation as well as cellular mechanical properties. In this study, we present a simple method to fabricate micro-hump patterned interfaces based on electrohydrodynamic jet (E-jet) printing to control and direct cell organization. Micro-hump structures were rapidly fabricated by E-jet printing and arbitrary cell patterns can be achieved by selective cell adhesion induced by this surface topography. Furthermore, cellular mechanical properties were regulated by changing the density of microstructures. The technique we proposed could dynamically direct cell organization in a controlled manner, providing help for exploring the fundamental mechanism of cell adhesion and sensing.

Iron(III) minerals and anthraquinone-2,6-disulfonate (AQDS) synergistically enhance bioreduction of hexavalent chromium by Shewanella oneidensis MR-1.

Bioreduction of hexavalent chromium (Cr(VI)) to sparingly soluble trivalent chromium (Cr(III)) is a strategy for the remediation of Cr(VI) contaminated sites. However, its application is limited due to the slow bioreduction process. Here we explored the potential synergistic enhancement of iron(III) minerals (nontronite NAu-2, ferrihydrite, and goethite) and electron shuttle anthraquinone-2,6-disulfonate (AQDS) on the bioreduction of Cr(VI) by Shewanella oneidensis MR-1. AQDS alone increased the bioreduction rate of Cr(VI) by accelerating electron transfer from MR-1 to Cr(VI). Iron minerals alone did not increase the bioreduction rate of Cr(VI), where the electron transfer from MR-1 to Fe(III) minerals was inhibited due to the toxicity of Cr(VI) to MR-1. AQDS plus NAu-2 or ferrihydrite significantly enhanced the bioreduction rate of Cr(VI) as compared to AQDS or NAu-2/ferrihydrite alone, demonstrating that AQDS plus NAu-2/ferrihydrite had the synergistic effect on bioreduction of Cr(VI). Synergy factor (kcells+Fe+AQDS/(kcells+Fe + kcells+AQDS)) was used to quantify the synergistic effect of AQDS and iron minerals on the bioreduction of Cr(VI). The synergy factors of AQDS plus NAu-2 were 2.09-4.63 (three Cr(VI) spikes), and the synergy factors of AQDS plus ferrihydrite were 1.89-4.61 (two Cr(VI) spikes). In the presence of Cr(VI), AQDS served as the electron shuttle between MR-1 and iron minerals, facilitating the reduction of Fe(III) minerals to Fe(II). The synergistic enhancement of AQDS and NAu-2/ferrihydrite was attributed to the generated Fe(II), which could quickly reduce Cr(VI) to Cr(III). Our results provide an attractive strategy to strengthen the bio-immobilization of Cr(VI) at iron-rich contaminated sites through the synergistic enhancement of iron(III) minerals and electron shuttle.