Real-time monitoring of intracellular biochemical response in locally stretched single cell by a nanosensor.

Mechanotransduction is the essential process that cells convert mechanical force into biochemical responses, and electrochemical sensor stands out from existing techniques by providing quantitative and real-time information about the biochemical signals during cellular mechanotransduction. However, the intracellular biochemical response evoked by mechanical force has been poorly monitored. In this paper, we report a method to apply local stretch on single cell and simultaneously monitor the ensuing intracellular biochemical signals. Specifically, a ferromagnetic micropipette was fabricated to locally stretch a single cell labeled with Fe3O4 nanoparticles under the external magnetic field, and the SiC@Pt nanowire electrode (SiC@Pt NWE) was inserted into the cell to monitor the intracellular hydrogen peroxide (H2O2) production induced by the local stretch. As a proof of concept, this work quantitatively investigated the elevated amount of H2O2 levels in single endothelial cell under different stretching amplitudes. This work puts forward a new research modality to manipulate and monitor the mechanotransduction at the single-cell level.

Fast Antioxidation Kinetics of Glutathione Intracellularly Monitored by a Dual-Wire Nanosensor.

The glutathione (GSH) system is one of the most powerful intracellular antioxidant systems for the elimination of reactive oxygen species (ROS) and maintaining cellular redox homeostasis. However, the rapid kinetics information (at the millisecond to the second level) during the dynamic antioxidation process of the GSH system remains unclear. As such, we specifically developed a novel dual-wire nanosensor (DWNS) that can selectively and synchronously measure the levels of GSH and ROS with high temporal resolution, and applied it to monitor the transient ROS generation as well as the rapid antioxidation process of the GSH system in individual cancer cells. These measurements revealed that the glutathione peroxidase (GPx) in the GSH system is rapidly initiated against ROS burst in a sub-second time scale, but the elimination process is short-lived, ending after a few seconds, while some ROS are still present in the cells. This study is expected to open new perspectives for understanding the GSH antioxidant system and studying some redox imbalance-related physiological.

Soft Electrodes for Electrochemical and Electrophysiological Monitoring of Beating Cardiomyocytes.

Many cells in vivo have their inherent motions, which involve numerous biochemical and biophysical signals synergistically regulating cell behavior and function. However, existing methods offer little information about the concurrently chemical and physical responses of dynamically pulsing cells. Here, we report a soft electrode with an electrospun poly(3,4-ethylenedioxythiophene) (PEDOT)-based nanomesh to fully comply with spontaneous motions of cells. Moreover, this electrode demonstrated excellent electrical conductivity, electrochemical performance and cellular biocompatibility. Cardiomyocytes cultured thereon exhibited autonomous and rhythmic contractility, and synchronously induced mechanical deformation of the underlying electrode, which allowed real-time monitoring of nitric oxide release and electrophysiological activity of cardiomyocytes. This work provides a promising way toward recording chemical and electrical signals of biological systems with their natural motions.

Dual-channel nanoelectrochemical sensor for monitoring intracellular ROS and NADH kinetic variations of their concentrations.

Reactive oxygen species (ROS) and nicotinamide adenine dinucleotide (NADH) are important intracellular redox-active molecules involved in various pathological processes including inflammation, neurodegenerative diseases, and cancer. However, the fast dynamic changes and mutual regulatory kinetic relationship between intracellular ROS and NADH in these biological processes are still hard to simultaneously investigate. A dual-channel nanowire electrode (DC-NWE) integrating two conductive nanowires, one functionalized with platinum nanoparticles and the other with conductive polymer, was nanofabricated for the selective and simultaneous real-time monitoring of intracellular ROS and NADH release by mitochondria in single living MCF-7 tumoral cells stimulated by resveratrol. The production of ROS was observed to occur tenths of a second before the release of NADH, a significant new piece of information suggesting a mechanism of action of resveratrol. Beyond the importance of the specific data gathered in this study, this work established the feasibility of simultaneously monitoring multiple species and analyzing their kinetics relationships over sub-second time scales thanks to dual-channel nanowire electrodes. It is believed that this concept and its associated nanoelectrochemical tools might benefit to a deeper understanding of mutual regulatory relationship between intracellular crucial molecular markers during physiological and pathological processes as well as for evaluating medical treatments.

Intracellular monitoring of NADH release from mitochondria using a single functionalized nanowire electrode.

Mitochondria are the powerhouse of cells, and also their suicidal weapon store. Mitochondrial dysfunction can cause the opening of the mitochondrial permeability transition pore (mPTP) and nicotinamide adenine dinucleotide (NADH) release from mitochondria, eventually leading to the disruption of energy metabolism and even cell death. Hence, NADH is often considered a marker of mitochondrial function, but in situ monitoring of NADH release from mitochondria in single living cells remains a great challenge. Herein, we develop a functionalized single nanowire electrode (NWE) for electrochemical detection of NADH release from intracellular mitochondria by modifying conductive polymer (poly(3,4-ethylendioxythiophene), PEDOT)-coated carbon nanotubes (CNTs) on the surface of a SiC@C nanowire. The positively charged PEDOT facilitates the accumulation of negatively charged NADH at the electrode surface and CNTs promote electron transfer, thus endowing the NWE with high sensitivity and selectivity. Further studies show that resveratrol, a natural product, specifically induced NADH release from mitochondria of MCF-7 cancer cells rather than non-cancerous MCF-10 A cells, indicating the potential therapeutic effects of resveratrol in cancer treatment. This work provides an efficient method to monitor mitochondrial function by in situ electrochemical measurement of NADH release, which will be of great benefit for physiological and pathological studies.