Flexible Triboelectric Nanogenerator for Promoting the Proliferation and Migration of Human Fibroblast Cells.

Chronic wound healing is often a prolonged process with the migration and proliferation of fibroblast cells playing crucial roles. Electrical stimulation (ES) has emerged as a promising physical therapy modality to promote these key events. In this study, we address this issue by employing a triboelectric nanogenerator (TENG) as an electrical stimulator for both drug release and the stimulation of fibroblast cells. The flexible TENG with a sandwich structure was fabricated using a PCL nanofibrous layer, Kapton, and silicon rubber. The TENG could be folded to any degree and twisted, and it could return to its original shape when the force was removed. Cultured cells received ES twice and three times daily for 8 days, with a 30 min interval between sessions. By applying current in a safe range and appropriate time (twice daily), fibroblasts demonstrate an accelerated proliferation and migration rate. These observations were confirmed through cell staining. Additionally, in vitro tests demonstrated the TENG's ability to simultaneously provide ES and release vitamin C from the patch. After 2 h, the amount of released drug increased 2 times in comparison to the control group. These findings provide support for the development of a TENG for the treatment of wounds, which underlines the promise of this new technique for developing portable electric stimulation devices.

Facilitating long-term cell examinations and time-lapse recordings in cell biology research with CO2 mini-incubators.

In recent years, microscopy has revolutionized the study of dynamic living cells. However, performing long-term live cell imaging requires stable environmental conditions such as temperature, pH, and humidity. While standard incubators have traditionally provided these conditions, other solutions, like stagetop incubators are available. To further enhance the accessibility of stable cell culture environments for live cell imaging, we developed a portable CO2 cell culture mini-incubator that can be easily adapted to any x-y inverted microscope stage, enabling long-term live cell imaging. This mini-incubator provides and maintains stable environmental conditions and supports cell viability comparable to standard incubators. Moreover, it allows for parallel experiments in the same environment, saving both time and resources. To demonstrate its functionality, different cell lines (VERO and MDA-MB-231) were cultured and evaluated using various assays, including crystal violet staining, MTT, and flow cytometry tests to assess cell adhesion, viability, and apoptosis, respectively. Time-lapse imaging was performed over an 85-h period with MDA-MB-231 cells cultured in the mini-incubator. The results indicate that this device is a viable solution for long-term imaging and can be applied in developmental biology, cell biology, and cancer biology research where long-term time-lapse recording is required.

Enhanced proliferation and migration of fibroblast cells by skin-attachable and self-cleaning triboelectric nanogenerator.

Skin wounds are common in accidental injuries, surgical operations, and chronic diseases. The migration and proliferation of fibroblast cells are fundamental to wound healing, which can be promoted by electrical stimulation as a physical therapy modality. Therefore, the development of portable electrical stimulation devices that can be used by patients on-site is an essential need. In the present study, a self-cleaning triboelectric nanogenerator (TENG) has been fabricated for enhancing cell proliferation and migration. The polycaprolactone­titanium dioxide (PCL/TiO2) and polydimethylsiloxane (PDMS) layers were fabricated via a facile method and used as the electropositive and electronegative pair, respectively. The effect of stimulation time on proliferation and migration of fibroblast cells was investigated. The results demonstrated that when the cells were stimulated once-a-day for 40 min, the cell viability was increased, while a long daily stimulation time has an inhibitory effect. Under electrical stimulation, the cells move toward the middle of the scratch, making the scratch almost invisible. During repeated movements, the prepared TENG connected to a rat skin generated an open-circuit voltage and a short-circuit current around 4 V and 0.2 µA, respectively. The proposed self-powered device can pave the way for a promising therapeutic strategy for patients with chronic wounds.

CNT-PDMS foams as self-powered humidity sensors based on triboelectric nanogenerators driven by finger tapping.

An increasing number of frequently applied portable electronics has raised the significance of self-powered systems. In this regard, triboelectric nanogenerators (TENGs) have drawn considerable attention due to their diversity of design and high power output. As a widely used material in TENG electrodes, polydimethylsiloxane (PDMS) shows attractive characteristics, such as electron affinity, flexibility, and facile fabrication. To achieve active TENG-based humidity sensing, we proposed a straightforward method to enhance the hydrophilicity of PDMS by two parallel approaches: 1. Porosity induction, 2. Carbon nanotube (CNT) compositing. Both of the mentioned processes have been performed by water addition during the synthesis procedure, which is not only totally safe (in contrast with the similar foaming/compositing routes), but also applicable for a wide range of nanomaterials. Applying the modified electrode as a single-electrode TENG-based humidity sensor, demonstrated an impressive enhancement of sensing response from 56% up to 108%, compared to the bare electrodes. Moreover, the detecting range of ambient humidity was broadened to higher values of 80% in a linear behavior. The fabricated humidity sensor based on a CNT-PDMS foam not only provides superior sensing characteristics but also is satisfactory for portable applications, due to being lightweight and desirably self-powered.

Carbon Nanotube Modified Microelectrode Array for Neural Interface.

Carbon nanotubes (CNTs) coatings have been shown over the past few years as a promising material for neural interface applications. In particular, in the field of nerve implants, CNTs have fundamental advantages due to their unique mechanical and electrical properties. In this study, carbon nanotubes multi-electrode arrays (CNT-modified-Au MEAs) were fabricated based on gold multi-electrode arrays (Au-MEAs). The electrochemical impedance spectra of CNT-modified-Au MEA and Au-MEA were compared employing equivalent circuit models. In comparison with Au-MEA (17 Ω), CNT-modified-Au MEA (8 Ω) lowered the overall impedance of the electrode at 1 kHz by 50%. The results showed that CNT-modified-Au MEAs have good properties such as low impedance, high stability and durability, as well as scratch resistance, which makes them appropriate for long-term application in neural interfaces.

Gold-Plated Electrode with High Scratch Strength for Electrophysiological Recordings.

Multi electrode arrays (MEA) have been exploited in different electrophysiological applications. In neurological applications, MEAs are the vital interfaces between neurons and the electronic circuits with dual role; transmitting electric signal to the neurons and converting neural activity to the electric signal. Since the performance of the electrodes has a direct effect on the quality of the recorded neuronal signal, as well as the stimulation, the true choice of electrode material for MEA is crucial. Gold is one of the best candidates for fabrication of MEAs due to its high electrical conductivity, biocompatibility and good chemical stability. However, noble metals such as gold do not adhere well to the glass substrate. Consequently while exposing to the water, gold films are damaged, which impose limitations in the exploiting of gold thin films as the electrode. In this paper, a simple and cost effective method for the fabrication of gold electrode arrays is proposed. Using various mechanical (adhesion test and scratch strength), morphological (AFM and SEM) and electrochemical methods, the fabricated electrodes are characterized. The results show that the fabricated electrode arrays have significantly high scratch strength and stability within the aqueous medium. In addition, the electrical properties of the electrodes have been improved. The proposed electrodes have the potential to be exploited in other applications including electronics, electrochemistry, and biosensors.