Connective tissues are essential building blocks for organ development, repair and regeneration. However, we are at the early stages of understanding connective tissue dynamics. Here, we detail a method that enables in vivo fate mapping of organ extracellular matrix (ECM) by taking advantage of a crosslinking chemical reaction between amine groups and N-hydroxysuccinimide esters. This methodology enables robust labeling of ECM proteins, which complement previous affinity-based single-protein methods. This protocol is intended for entry-level scientists and the labeling step takes between 5 and 10 min. ECM 'tagging' with fluorophores using N-hydroxysuccinimide esters enables visualization of ECM spatial modifications and is particularly useful to study connective tissue dynamics in organ fibrosis, tumor stroma formation, wound healing and regeneration. This in vivo chemical fate mapping methodology is highly versatile, regardless of the tissue/organ system, and complements cellular fate-mapping techniques. Furthermore, as the basic chemistry of proteins is highly conserved between species, this method is also suitable for cross-species comparative studies of ECM dynamics.

On-chip electrocatalytic microdevices (OCEMs) are an emerging electrochemical platform specialized for investigating nanocatalysts at the microscopic level. The OCEM platform allows high-precision electrochemical measurements at the individual nanomaterial level and, more importantly, offers unique perspectives inaccessible with conventional electrochemical methods. This protocol describes the critical concepts, experimental standardization, operational principles and data analysis of OCEMs. Specifically, standard protocols for the measurement of the electrocatalytic hydrogen evolution reaction of individual 2D nanosheets are introduced with data validation, interpretation and benchmarking. A series of factors (e.g., the exposed area of material, the choice of passivation layer and current leakage) that could have effects on the accuracy and reliability of measurement are discussed. In addition, as an example of the high adaptability of OCEMs, the protocol for in situ electrical transport measurement is detailed. We believe that this protocol will promote the general adoption of the OCEM platform and inspire further development in the near future. This protocol requires essential knowledge in chemical synthesis, device fabrication and electrochemistry.

The production of induced neuronal (iN) cells from human embryonic stem cells (ESCs) and induced pluripotent stem cells by the forced expression of proneural transcription factors is rapid, efficient and reproducible. The ability to generate large numbers of human neurons in such a robust manner enables large-scale studies of human neural differentiation and neuropsychiatric diseases. Surprisingly, similar transcription factor-based approaches for converting mouse ESCs into iN cells have been challenging, primarily because of low cell survival. Here, we provide a detailed approach for the efficient and reproducible generation of functional iN cells from mouse ESC cultures by the genetically induced expression of neurogenin-2. The resulting iN cells display mature pre- and postsynaptic specializations and form synaptic networks. Our method provides the basis for studying neuronal development and enables the direct comparison of cellular phenotypes in mouse and human neurons generated in an equivalent way. The procedure requires 14 d and can be carried out by users with expertise in stem cell culture.