Hydrogel structures equipped with internal microchannels offer more in vivo‐relevant models for construction of tissues and organs in vitro. However, currently used microfabrication methods of constructing microfluidic devices are not suitable for the handling of hydrogel. This study presents a novel method of fabricating hydrogel‐based microfluidic chips by combining the casting and bonding processes. A twice cross‐linking strategy is designed to obtain a bonding interface that has the same strength with the hydrogel bulk, which can be applied to arbitrary combinations of hydrogels. It is convenient to achieve the construction of hydrogel structures with channels in branched, spiral, serpentine, and multilayer forms. The experimental results show that the combination of gelatin and gelatin methacrylate (GelMA) owns the best biocompatibility and can promote cell functionalization. Based on these, a vessel‐on‐a‐chip system with vascular function in both physiological and pathological situations is established, providing a promising model for further investigations such as vascularization, vascular inflammation, tissue engineering, and drug development. Taken together, a facile and cytocompatible approach is developed for engineering a user‐defined hydrogel‐based chip that can be potentially useful in developing vascularized tissue or organ models.

BackgroundHistone deacetylases (HDACs) function as key epigenetic factors in repressing the expression of genes in multiple aspects of plant growth, development and plant response to abiotic or biotic stresses. To date, the molecular function of HDACs is well described in Arabidopsis thaliana, but no systematic analysis of this gene family in soybean (Glycine max) has been reported.ResultsIn this study, 28 HDAC genes from soybean genome were identified, which were asymmetrically distributed on 12 chromosomes. Phylogenetic analysis demonstrated that GmHDACs fall into three major groups previously named RPD3/HDA1, SIR2, and HD2. Subcellular localization analysis revealed that YFP-tagged GmSRT4, GmHDT2 and GmHDT4 were predominantly localized in the nucleus, whereas GmHDA6, GmHDA13, GmHDA14 and GmHDA16 were found in both the cytoplasm and nucleus. Real-time quantitative PCR showed that GmHDA6, GmHDA13, GmHDA14, GmHDA16 and GmHDT4 were broadly expressed across plant tissues, while GmHDA8, GmSRT2, GmSRT4 and GmHDT2 showed differential expression across various tissues. Interestingly, we measured differential changes in GmHDACs transcripts accumulation in response to several abiotic cues, indicating that these epigenetic modifiers could potentially be part of a dynamic transcriptional response to stress in soybean. Finally, we show that the levels of histone marks previously reported to be associated with plant HDACs are modulated by cold and heat in this legume.ConclusionWe have identified and classified 28 HDAC genes in soybean. Our data provides insights into the evolution of the HDAC gene family and further support the hypothesis that these genes are important for the plant responses to environmental stress.Electronic supplementary materialThe online version of this article (10.1186/s12870-018-1454-7) contains supplementary material, which is available to authorized users.

The laser-induced breakdown spectroscopy (LIBS) technique coupled with machine learning was proposed to perform four metal elements quantitative analysis and pollution source discrimination in atmospheric sedimentation.

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