Advances in wearable epidermal sensors have revolutionized the way that physiological signals are captured and measured for health monitoring. One major challenge is to convert physiological signals to easily readable signals in a convenient way. One possibility for wearable epidermal sensors is based on visible readouts. There are a range of materials whose optical properties can be tuned by parameters such as temperature, pH, light, and electric fields. Herein, this review covers and highlights a set of materials with tunable optical properties and their integration into wearable epidermal sensors for health monitoring. Specifically, the recent progress, fabrication, and applications of these materials for wearable epidermal sensors are summarized and discussed. Finally, the challenges and perspectives for the next generation wearable devices are proposed.

Given that colorectal cancer stem cells (CCSCs) play key roles in the tumor dormancy, metastasis, and relapse, targeting CCSCs is a promising strategy in cancer therapy. Here, we aimed to identify the new regulators of CCSCs and found that Cullin 4B (CUL4B), which possesses oncogenic properties in multiple solid tumors, drives the development and metastasis of colon cancer by sustaining cancer stem-like features. Elevated expression of CUL4B was confirmed in colon tumors and was associated with poor overall survival. Inhibition of CUL4B in cancer cell lines and patient-derived tumor organoids led to reduced sphere formation, proliferation and metastasis capacity. Mechanistically, CUL4B coordinates with PRC2 complex to repress miR34a expression, thus upregulates oncogenes including MYCN and NOTCH1, which are targeted by miR34a. Furthermore, we found that elevated CUL4B expression is associated with miR34a downregulation and upregulation of miR34a target genes in colon cancer specimens. Collectively, our findings demonstrate that CUL4B functions to repress miR34a in maintaining cancer stemness in CRC and provides a potential therapeutic target.

Hydrogel‐based wearable epidermal sensors (HWESs) have attracted widespread attention in health monitoring, especially considering their colorimetric readout capability. However, it remains challenging for HWESs to work at extreme temperatures with long term stability due to the existence of water. Herein, a wearable transparent epidermal sensor with thermal compatibility and long term stability for smart colorimetric multi‐signals monitoring is developed, based on an anti‐freezing and anti‐drying hydrogel with high transparency (over 90% transmittance), high stretchability (up to 1500%) and desirable adhesiveness to various kinds of substrates. The hydrogel consists of polyacrylic acid, polyacrylamide, and tannic acid‐coated cellulose nanocrystals in glycerin/water binary solvents. When glycerin readily forms strong hydrogen bonds with water, the hydrogel exhibits outstanding thermal compatibility. Furthermore, the hydrogel maintains excellent adhesion, stretchability, and transparency after long term storage (45 days) or at subzero temperatures (−20 °C). For smart colorimetric multi‐signals monitoring, the freestanding smart colorimetric HWESs are utilized for simultaneously monitoring the pH, T and light, where colorimetric signals can be read and stored by artificial intelligence strategies in a real time manner. In summary, the developed wearable transparent epidermal sensor holds great potential for monitoring multi‐signals with visible readouts in long term health monitoring.

Wearable Sensors In article number 2201730 by Feng Xu and co‐workers, freestanding smart colorimetric hydrogel‐based wearable epidermal sensors are utilized for simultaneously monitoring the pH, temperature, and light, where colorimetric signals can be read and stored by artificial intelligence strategies in a real‐time manner. This developed wearable transparent epidermal sensor holds great potential for monitoring multi‐signals with visible readouts in long‐term health monitoring.

The endothelial cell (EC) outgrowth in both vasculogenesis and angiogenesis starts with remodeling surrounding matrix and proceeds with the crosstalk between cells for the multicelluar vasculature formation. Althought the mechanical plasticity of matrix has been recognized to regulate individual cell behaviors through plastic remodeling, it remains elusive how matrix plasticity impacts cell-to-cell interplay during EC outgrowth and the underlying molecular pathways. Here we developed a collagen-hyaluronic acid based hydrogel platform with tunable plasticity independent of stiffness, by using compositing strategy of dynamic and covalent crosslinks. We show that the increasing plasticity of the hydrogel networks facilitates the matrix remodeling by ECs, thus promoting the process of individual sprouting and branching during vasculogenesis. However, the lagest tubular lumens and the longest invading distance from EC spheoid unexpectedly appear in hydrogels with medium plasticity instead of the highest ones. We unravel that althought the high plasticity of the hydrogels promotes stable integrin cluster of ECs and recruitment of focal adhesion kinase (FAK) with an increase in cell contractility, while the overenhanced contractility downregulates the vascular endothelial calmodulin (VE-CAD) expression and destabilizes the adherens junctions between individual ECs in vasculogenesis (or stalk and tip ECs in angiogenesis). Our results, further validated with mathematical simulations and in vivo angiogenic tests, demonstrate that a balance of matrix plasticity facilitates both cell-matrix binding and cell-to-cell adherens, for promoting vascular assembly and invasion.