Dielectrophoretic Micro-Organization of Chondrocytes to Regenerate Mechanically Anisotropic Cartilaginous Tissue

OpenDEP: An Open-Source Platform for Dielectrophoresis Spectra Acquisition and Analysis

Dielectrophoretic (DEP) cell separation, which utilizes electric fields to selectively manipulate and separate cells based on their electrical properties, has emerged as a cutting-edge label-free technique. DEP separation techniques rely on differences in the electrical and morphological properties of cells, which can be obtained by a thorough analysis of DEP spectra. This article presents a novel platform, named OpenDEP, for acquiring and processing DEP spectra of suspended cells. The platform consists of lab-on-a-chip and open-source software that enables the determination of DEP spectra and electric parameters. The performance of OpenDEP was validated by comparing the results obtained using this platform with the results obtained using a commercially available device, 3DEP from DEPtech. The lab-on-a-chip design features two indium tin oxide-coated slides with a specific geometry, forming a chamber where cells are exposed to an inhomogeneous alternating electric field with different frequencies, and microscopic images of cell distributions are acquired. A custom-built software written in the Python programing language was developed to convert the acquired images into DEP spectra, allowing for the estimation of membrane and cytoplasm conductivities and permittivities. The platform was validated using two cell lines, DC3F and NIH 3T3. The OpenDEP platform offers several advantages, including easy manufacturing, statistically robust computations due to large cell population analysis, and a closed environment for sterile work. Furthermore, continuous observation using any microscope allows for integration with other techniques.

Editorial for the Special Issue on Micromachines for Dielectrophoresis, Volume II

Dielectrophoresis (DEP) remains an effective technique for the label-free identification and manipulation of targeted particles ranging from sizes from nano to micrometers and from inert particles to biomolecules and cells [...].

Efficient Cell Impedance Measurement by Dielectrophoretic Cell Accumulation and Evaluation of Chondrogenic Phenotypes

The quantitative and functional analyses of cells are important for cell-based therapies. In this study, to establish the quantitative cell analysis method, we propose an impedance measurement method supported by dielectrophoretic cell accumulation. An impedance measurement and dielectrophoresis device was constructed using opposing comb-shaped electrodes. Using dielectrophoresis, cells were accumulated to form chain-like aggregates on the electrodes to improve the measurement sensitivity of the electrical impedance device. To validate the proposed method, the electrical impedance and capacitance of primary and de-differentiated chondrocytes were measured. As a result, the impedance of the chondrocytes decreased with an increase in the passage number, whereas the capacitance increased. Therefore, the impedance measurement method proposed in this study has the potential to identify chondrocyte phenotypes.

Efficient Decellularization by Application of Moderate High Hydrostatic Pressure with Supercooling Pretreatment

Decellularized tissues are considered superior scaffolds for cell cultures, preserving the microstructure of native tissues and delivering many kinds of cytokines. High hydrostatic pressure (HHP) treatment could remove cells physically from biological tissues rather than chemical methods. However, there are some risks of inducing destruction or denaturation of extracellular matrices (ECMs) at an ultrahigh level of HHP. Therefore, efficient decellularization using moderate HHP is required to remove almost all cells simultaneously to suppress tissue damage. In this study, we proposed a novel decellularization method using a moderate HHP with supercooling pretreatment. To validate the decellularization method, a supercooling device was developed to incubate human dermal fibroblasts or collagen gels in a supercooled state. The cell suspension and collagen gels were subjected to 100, 150, and 200 MPa of HHP after supercooling pretreatment, respectively. After applying HHP, the viability and morphology of the cells and the collagen network structure of the gels were evaluated. The viability of cells decreased dramatically after HHP application with supercooling pretreatment, whereas the microstructures of collagen gels were preserved and cell adhesivity was retained after HHP application. In conclusion, it was revealed that supercooling pretreatment promoted the denaturation of the cell membrane to improve the efficacy of decellularization using static application of moderate HHP. Furthermore, it was demonstrated that the HHP with supercooling pretreatment did not degenerate and damage the microstructure in collagen gels.