Ferroptosis, as a promising therapeutic strategy for cancers, has aroused great interest. Quantifying the quick dynamic changes in key parameters during the early course of ferroptosis can provide insights for understanding the underlying mechanisms of ferroptosis and help the development of therapies targeting ferroptosis. However, in situ and quantitatively monitoring the quick responses of living cancer cells to ferroptosis at the single-cell level remains technically challenging. In this work, we selected HuH7 cells (hepatocellular carcinoma (HCC) cells) as a cell model and Erastin as a typical ferroptosis inducer. We utilized scanning electrochemical microscopy (SECM) to quantitatively and in situ monitor the early course of ferroptosis in HuH7 cells by characterizing the three key parameters of cell ferroptosis (i.e., cell membrane permeability, respiratory activity, and the redox state). The SECM results show that the membrane permeability of ferroptotic HuH7 cells continuously increased from 0 to 8.1 × 10 −5 m s −1 , the cellular oxygen consumption was continuously reduced by half, and H 2 O 2 released from the cells exhibited periodic bursts during the early course of ferroptosis, indicating the gradually destroyed cell membrane structure and intensified oxidative stress. Our work realizes, for the first time, the in situ and quantitative monitoring of the cell membrane permeability, respiratory activity, and H 2 O 2 level of the early ferroptosis process of a single living cancer cell with SECM, which can contribute to the understanding of the physiological process and underlying mechanisms of ferroptosis.
In vitro cardiac tissue model holds great potential as a powerful platform for drug screening. Respiratory activity, contraction frequency, and extracellular H2O2 levels are the three key parameters for determining the physiological functions of cardiac tissues, which are technically challenging to be monitored in an in situ and quantitative manner. Herein, we constructed an in vitro cardiac tissue model on polyacrylamide gels and applied a pulsatile electrical field to promote the maturation of the cardiac tissue. Then, we built a scanning electrochemical microscopy (SECM) platform with programmable pulse potentials to in situ characterize the dynamic changes in the respiratory activity, contraction frequency, and extracellular H2O2 level of cardiac tissues under both normal physiological and drug (isoproterenol and propranolol) treatment conditions using oxygen, ferrocenecarboxylic acid (FcCOOH), and H2O2 as the corresponding redox mediators. The SECM results showed that isoproterenol treatment induced enhanced oxygen consumption, accelerated contractile frequency, and increased released H2O2 level, while propranolol treatment induced dynamically decreased oxygen consumption and contractile frequency and no obvious change in H2O2 levels, suggesting the effects of activation and inhibition of β-adrenoceptor on the metabolic and electrophysiological activities of cardiac tissues. Our work realizes the in situ and quantitative monitoring of respiratory activity, contraction frequency, and secreted H2O2 level of living cardiac tissues using SECM for the first time. The programmable SECM methodology can also be used to real-time and quantitatively monitor electrochemical and electrophysiological parameters of cardiac tissues for future drug screening studies.
Due to the inherent disorder and fluidity of water, precise machining of water through laser cutting are challenging. Herein we report a strategy that realizes the laser cutting machining of water through constructing hydrophobic silica nanoparticle-encased water pancakes with sub-millimeter depth. Through theoretical analysis, numerical simulation, and experimental studies, the developed process of nanoparticle-encased water pancake laser cutting and the parameters that affect cutting accuracy are verified and elucidated. We demonstrate that laser-fabricated water patterns can form diverse self-supporting chips (SSCs) with openness, transparency, breathability, liquid morphology, and liquid flow control properties. Applications of laser-fabricated SSCs to various fields, including chemical synthesis, biochemical sensing, liquid metal manipulation, patterned hydrogel synthesis, and drug screening, are also conceptually demonstrated. This work provides a strategy for precisely machining water using laser cutting, addressing existing laser machining challenges and holding significance for widespread fields involving fluid patterning and flow control in biological, chemical, materials and biomedical research.
Cardiac tissue is sensitive to and can be easily damaged by exogenous electric stimulation. However, due to the thermal−electric coeffect and the limitation of in situ and quantitative information on the cardiac tissue function under electric stimulation, the detailed effect and the underlying mechanism of exogenous electric stimulation on the cardiac tissue remain elusive. To address this, in this work, we first constructed an in vitro cardiac tissue model and established a thermal−electric coupled theoretical model for simulating the electric field and temperature distributions around the cardiac tissue, from which we selected the electric field strengths (1.19, 2.37, and 3.39 kV cm −1 ) and electrical energies (0.001, 0.005, and 0.011 J) for electric stimulations without inducing a thermal effect. Then, we applied electric field stimulations on the cardiac tissue using these parameters and scanning electrochemical microscopy (SECM) to in situ and quantitatively monitor the dynamic changes in the key parameters of the cardiac tissue function, including respiratory activity, membrane permeability, and contraction frequency, after electric field stimulations. The SECM results showed that the oxygen consumption, cell membrane permeability coefficient, and contraction frequency of the cardiac tissue were strongly dependent on electrical energy, especially when the electrical energy was higher than 0.001 J. Our work, for the first time, achieves the in situ and quantitative monitoring of the cardiac tissue function under electric stimulation using SECM, which would provide important references for designing an electric stimulation regime for cardiac tissue engineering and clinical application of electrotherapy.
Central nervous system is sensitive and vulnerable to heat. Oxidative state and oxidative damage of neurons under heat stress are vital for understanding early consequences and mechanisms of heat‐related neuronal injury, which remains elusive partly due to the technical challenge of in situ and quantitative monitoring methods. Herein, a temperature‐controlled scanning electrochemical microscopy (SECM) platform with programmable pulse potential and depth scan modes is developed for in situ and quantitatively monitoring of oxygen consumption, extracellular hydrogen peroxide level, and cell membrane permeability of neurons under thermal microenvironment of 37–42 °C. The SECM results show that neuronal oxygen consumption reaches a maximum at 40 °C and then decreases, extracellular H2O2 level increases from 39 °C, and membrane permeability increases from 2.0 ± 0.6 × 10−5 to 7.2 ± 0.8 × 10−5 m s−1 from 39 to 42 °C. The therapeutic effect on oxidative damage of neurons under hyperthermia conditions (40–42 °C) is further evaluated by SECM and fluorescence methods, which can be partially alleviated by the potent antioxidant edaravone. This work realizes in situ and quantitatively observing the heat‐induced oxidative state and oxidative damage of living neurons using SECM for the first time, which results can contribute to a better understanding of the heat‐related cellular injury mechanism.
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