Electrostimulation Cell Culture Assembly Incorporated with Chemically Modified Coiled Carbon Nanotube Yarn-Based Twistron Harvesters

Electrical stimulation (ES) systems have gained significant attention due to their potential in biomedical applications such as neuromodulation, neuroprosthetics, cardiac pacing, wound healing, arrhythmia management, muscle stimulation, and tissue engineering. Especially, enhancing cells’ proliferation and differentiation by using ES provides a promising strategy to overcome the challenges related to regenerative medicine, disease modeling, and drug delivery.
Conventional power supplies like batteries, electromagnetic field generators, and electrical grids have been connected to biomedical applications to transport the ES to the target cells. However, such conventional ES systems require periodic charging and replacement of batteries and external lines for connecting, presenting the ES system's bulky volume and high complexity. Considering the limitations of conventional ES systems, mechanical energy harvesting technologies are alternative ES providers due to their sustainability, lightweight, and user-friendliness. Mechanical energy harvesters, such as triboelectric and piezoelectric nanogenerators, have already paved the way as ES providers. They provide the ES for enhancing cells' biological response by converting mechanical energy (e.g., motion, vibration, and flow) to electrical energy.
When mechanical energy harvesters are integrated into the cell culture system, it is crucial to consider the generated ES range. For example, currents in the 5–15 μA cm⁻² range have been reported to promote proliferation and differentiation for chondrocytes, while lower values (0.1–5 μA cm^-1) may be more suitable for neural stem cells. In the case of fibroblasts, a slightly more comprehensive current range (0.1–17 μA cm^-2) may be required to stimulate proliferation and differentiation. Compared to this ES range, the mechanical energy harvesters offer a narrow range from a few nanoamperes to several microamperes, indicating the limited type of cell application. Thus, it is desirable to generate a broad electrical current range to satisfy the cell type's specific ES.
In this work, we present an integrated cell culture system that harnesses the chemically modified twistron harvester as a novel strategy for ES. Our cell culture system, called a fully integrated ES assembly (FESA), introduces an electrostimulation cell culture assembly using a coiled polydopamine (PDA)-incorporated carbon nanotube (CNT) yarn harvester as an ES generator and poly(3,4-ethylenedioxythiophene)-coated CNT (PEDOT/CNT) sheets as conductive scaffolds. The novel PDA-incorporated CNT yarn harvester achieved enhanced capacitance (8.4 F g^-1) and current generation (466.35 A kg^-1) due to PDA's hydrophilicity and high conductivity, which led to successful ES generation within aqueous cell culture medium. Furthermore, the handmade conductive scaffold showed suitable surface properties for cell culture: 1) suitable surface roughness and hydrophilicity for cell adhesion, and 2) homogeneous conductivity for ES transmission to cell. As a result, FESA showed the most comprehensive ES range ≈ , 75.4 µA cm^-2, compared to the reported cell culture system integrated mechanical energy harvesters, indicating the remarkably high applicability in various cell types. The FESA demonstrated positive biological responses in meniscal primary cells, highlighting its potential for self-powered cell culture applications.