A magnetically enabled simulation of microgravity represses the auxin response during early seed germination on a microfluidic platform

For plants on Earth, the phytohormone auxin is essential for gravitropism-regulated seedling establishment and plant growth. However, little is known about auxin responses under microgravity conditions due to the lack of a tool that can provide an alteration of gravity. In this paper, a microfluidic negative magnetophoretic platform is developed to levitate Arabidopsis seeds in an equilibrium plane where the applied magnetic force compensates for gravitational acceleration. With the benefit of the microfluidic platform to simulate a microgravity environment on-chip, it is found that the auxin response is significantly repressed in levitated seeds. Simulated microgravity statistically interrupts auxin responses in embryos, even after chemical-mediated auxin alterations, illustrating that auxin is a critical factor that mediates the plant response to gravity alteration. Furthermore, pretreatment with an auxin transportation inhibitor (N-1-naphthylphthalamic acid) enables a decrease in the auxin response, which is no longer affected by simulated microgravity, demonstrating that polar auxin transportation plays a vital role in gravity-regulated auxin responses. The presented microfluidic platform provides simulated microgravity conditions in an easy-to-implement manner, helping to study and elucidate how plants correspond to diverse gravity conditions; in the future, this may be developed into a versatile tool for biological study on a variety of samples.

Multilayer microfluidic platform for the study of luminal, transmural, and interstitial flow

Efficient delivery of oxygen and nutrients to tissues requires an intricate balance of blood, lymphatic, and interstitial fluid pressures, and gradients in fluid pressure drive the flow of blood, lymph, and interstitial fluid through tissues. While specific fluid mechanical stimuli, such as wall shear stress, have been shown to modulate cellular signaling pathways along with gene and protein expression patterns, an understanding of the key signals imparted by flowing fluid and how these signals are integrated across multiple cells and cell types in native tissues is incomplete due to limitations with current assays. Here, we introduce a multi-layer microfluidic platform (MLTI-Flow) that enables the culture of engineered blood and lymphatic microvessels and independent control of blood, lymphatic, and interstitial fluid pressures. Using optical microscopy methods to measure fluid velocity for applied input pressures, we demonstrate varying rates of interstitial fluid flow as a function of blood, lymphatic, and interstitial pressure, consistent with computational fluid dynamics models. The resulting microfluidic and computational platforms will provide for analysis of key fluid mechanical parameters and cellular mechanisms that contribute to diseases in which fluid imbalances play a role in progression, including lymphedema and solid cancer.

Droplet-assisted electrospray phase separation using an integrated silicon microfluidic platform

We report on a silicon microfluidic platform that enables integration of transparent μm-scale microfluidic channels, an on-chip pL-volume droplet generator, and a nano-electrospray ionization emitter that enables spatial and temporal phase separation for mass spectrometry analysis.