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Osteoarthritis (OA) is one of the most common causes of physical disability among older people and its incidence increases with age. Removal of the senescent cells (SNCs) delays OA pathologies, but little is known about the SNCs in OA synovium and their roles in OA pathogenesis. Here, we reported that RCAN1+IL1α+double-positive cells represent a senescent subset of synovial fibroblasts which accelerate cartilage degeneration via saturated fatty acids (SFAs). Using single-cell RNA sequencing and synovial organoids, we found that IL1α+ senescent synovial fibroblasts mainly located at lining layer of human OA synovium and promote cartilage degeneration. We performed genome-wide CRISPR/Cas9 screens to identify novel regulators of cell-surface bounded IL1α in senescent cells. RCAN1, which was a hit as positive regulator of IL1α, governs the cellular senescence and pro-degenerative senescence-associated secretory phenotype (SASP). Mechanistically, we found that RCAN1 mediated the secretion of SFAs from senescent synovial fibroblasts, which promote chondrocytes senescence and cartilage matrix degradation. Intra-articular delivery of synovium-targeted anti-Rcan1 siRNA ameliorates the development of post-traumatic OA in mice, while reducing of SNCs accumulation in synovium and increasing cartilage regeneration. Last, co-culture experiments of human OA cartilage explant with synovial organoids confirmed that RCAN1 silencing in human synovial fibroblasts suppressed chondrocyte senescence and cartilage degradation. Thus, our study revealed a pro-degenerative interaction between RCAN1+IL1α+senescent synovial fibroblasts and chondrocytes through secreted lipid mediators in OA progression. And targeted RCAN1 inhibition in senescent synovium is a promising approach for restore the joint homeostasis.

Conservative treatments are important in lumbar disc herniation (LDH), but predictors for poor outcomes are unclear.Consecutive patients with unilateral single-level LDH at L3-4 or L4-5 were enrolled. Baseline clinical data were collected, and lumbar spine magnetic resonance imaging was evaluated. Foraminal stenosis was evaluated using Lee's approach and further categorized as absence (grade 0 and 1) or presence (grade 2 or 3). Each patient underwent conservative treatments (oral meloxicam and dexamethasone, corset, back extension exercise, physiotherapy, and manual therapy) for 6 weeks. Conservative treatments were defined as failed if a patient underwent surgery within 6 weeks or reported poor recovery at 6-week follow-up. Multivariate logistic regressions were used to examine the associations of failed conservative treatments with baseline characteristics and magnetic resonance imaging findings.The study included 222 patients (mean age 45.5 ± 9.8 years). Of patients, 48 (21.6%) had concurrent ipsilateral foraminal stenosis at the caudal segment, and conservative treatments failed in 39 (17.6%). At baseline, patients with LDH and caudal foraminal stenosis were older (50.79 ± 6.14 years vs. 44.10 ± 10.13 years, P0.001), had greater leg pain (7.06 ± 1.17 vs. 6.39 ± 1.40, P = 0.003), and had a higher rate of positive straight leg raising test (54.2% vs. 33.3%, P = 0.008) than patients without caudal foraminal stenosis. In multivariate regression, failure of conservative treatments was associated with positive straight leg raising test (odds ratio 2.26, P = 0.046), and caudal foraminal stenosis (odds ratio 3.20, P = 0.007).In the presence of caudal foraminal stenosis and positive SLR test, conservative treatments were more likely to fail in patients with LDH.

Although there are standard treatment options for osteosarcoma (OS), the prognoses of patients with OS remain varied. Therefore, it is important to profile OS patients at a high risk of mortality to develop focused interventions. Although tumor biomarkers are closely associated with clinical outcomes, data on prognostic biomarkers for OS remain scarce.We collected RNA expression profiles and clinical data of 90 OS patients from the GEO database (dataset GSE21257 and GSE39055) and 96 patients in the TARGET program. The data were analyzed using univariate Kaplan-Meier survival analysis to screen candidate gene sets that might be associated with OS survival.Our analysis demonstrated that melanoma cell adhesion molecule (MCAM) was associated with overall survival of patients with OS in the three cohorts. The data showed that MCAM was upregulated in OS patients who had metastases within 5 years compared to those without metastases. GO analysis revealed that genes correlated with MCAM were mainly involved in cell migration and wound healing processes. In addition, wound healing assays and gene set enrichment analysis results from RNA sequencing data of small interfering (si)-MCAM-transfected OS cells demonstrated that MCAM modulated tumor cell migration.Our data demonstrate that MCAM may be a novel prognostic biomarker for OS. MCAM is associated with increased cell migration ability and risk of metastasis, thus leading to poor prognoses in OS patients.

For ultra-wideband (9 kHz–9 GHz) 2-port impedance spectroscopy of a biological cell, sensitivity analysis was carried out for extracting lumped cell characteristics such as membrane resistance (as large as 1 MΩ) and cytoplasm capacitance (as small as 10 fF) from the scattering parameters. The scattering parameters were measured on a coplanar waveguide with a Jurkat cell trapped by dielectrophoresis either in a series or shunt configuration. The sensitivity analysis validated our previous empirical observation that the insertion loss of a series-trapped cell and the return loss of a shunt-trapped cell were most sensitive to the cell impedance. Additionally, the membrane resistance and cytoplasm capacitance were most sensitive to low- and high-frequency scattering parameters, respectively. In the future, the analysis can be used to optimize the test setup and protocol for fast, compact, and label-free characterization of a cell at the subcelluar level.

Epigenetic regulation is highly correlated with osteoarthritis (OA) development, whereas its role and detailed mechanisms remain elusive. In this study, we explored the expression of EZH2, an H3K27me3 transferase, in human OA cartilages and its roles in regulating OA pathogenesis. Here, we found EZH2 was highly expressed in both mice and human OA cartilage samples by using histological analysis and RNA sequencing (RNA-Seq). The medial meniscectomy (MMx) OA model results indicated the conditional knockout of Ezh2 deteriorated OA pathological conditions. Furthermore, we showed the positive role of Ezh2 in cartilage wound healing and inhibition of hypertrophy through activating TNFSF13B, a member of the tumor necrosis factor superfamily. Further, we also indicated that the effect of TNFSF13B, increased by Ezh2, might boost the healing of chondrocytes through increasing the phosphorylation of Akt. Taken together, our results uncovered an EZH2-positive subpopulation existed in OA patients, and that EZH2-TNFSF13B signaling was responsible for regulating chondrocyte healing and hypertrophy. Thus, EZH2 might act as a new potential target for OA diagnosis and treatment. © 2020 American Society for Bone and Mineral Research.

Adverse events related to surgical mesh implants such as mesh erosion and adhesion are inflammation-related and frequently reported in clinical use; thus, advanced real-time monitoring methods are required to evaluate the interactions between implants and host immune system in order to prevent any unfavorable events. Here, we performed single cell mass cytometry of the blood, characterizing two biomaterial-induced (silk and polypropylene) immune responses in a rodent ventral hernia model to systematically decipher the interactions between the host and implants. Compared to polypropylene, silk mesh induced less immune cell activation with lower proportions of macrophages, monocytes, and neutrophils in the innate system and lower proportions of CD4+ T cells and CD8+ T cells in the adaptive system at 3-week post-implantation. Functional markers (CD115, CD27, and CD62L) involved in the immune cell activation and migration were also downregulated in the silk group. Histological analysis of tissues confirmed that silk mesh implantation led to decreased neutrophils and macrophages recruitment, less fibrosis formation, and better tissue healing, suggesting silk mesh as a superior implant material. Importantly, in patients with abdominal hernia, the ratio of monocytes in blood in the silk group was also significantly lower when compared to the polypropylene group. Our study provides a systematical profile of the material-based foreign body response at single cell resolution, highlighting the impact of biomaterial implants on whole body immune system and introducing an innovative approach to monitor material-based immune response.

For the first time, both lower and upper crossover frequencies of the real part of the Clausius–Mossotti function were calculated by using cell parameters measured on the same ultrawideband setup as that for single-cell dielectrophoresis. The calculation suggests that the lower crossover frequency can be from 0 to 127 kHz and that the upper crossover frequency can be from 45 to 108 MHz, in the unlikely case when uncertainties in the cell parameters all add up. The calculated lower crossover frequency was found to be in general agreement with the measured values of 28 ± 4 kHz. However, the calculated upper crossover frequency was significantly different from the measured values of 326 ± 35 MHz. The difference can be attributed to the field being highly nonuniform in single-cell dielectrophoresis, especially at higher frequencies. Additionally, with closely spaced electrodes in single-cell dielectrophoresis, adhesive force may have to be considered, even for a relatively nonadherent Jurkat cell. In any case, the difference between the calculated and measured crossover frequency suggests that the classical Clausius–Mossotti function, originally derived from the Maxwell–Wagner mixture model of a cell suspension, may not apply to single-cell dielectrophoresis in a straightforward manner, especially at high frequencies.

Nitrogen, phosphorus, and metals’ pollutants discharged from industrial sources eventually accumulate in lake sediment, hence increasing the difficulty of sediment treatment and disposal. In this work, the water storage ceramsite is prepared from dredged lake sediment and cyano-bacterial powder. The effects of pyrolysis temperature and cyanobacterial sediment on the porosity of ceramsite were investigated. The results showed that the pyrolysis of organic matter and the de-composition of compounds or salts can produce gas, causing a rich pore structure inside the ceramsite. When the temperature increased to 1150 °C, vitrification would collapse the pore structure inside the material. At the cyanobacterial-to-sediment ratio of 3:7, the porosity and water absorption of the material could reach 81.82% and 92.45% when the pyrolysis temperature was 500 and 1050 °C, respectively. The internal macropore structure of ceramsite improved the water absorption performance, and the mesoporous structure was responsible for its long water release time and stable water release structure. The ceramsite exhibited a superior metals’ retention effect. Under different pH and temperature conditions, the consolidation rates of Fe, Ni, Mn, Cr, and Pb in ceramsite were all more than 99%, suggesting the safety of the material in environmental applications. This study demonstrates the feasibility of the resourceful production of water storage ceramsite from lake sediment and cyanobacterial slurry, which helps to reduce the impact of solid waste on the environment. Thus, this work provides a practical basis for guiding water storage ceramsite in the construction of sponge cities.

Oxidative stress (OS) is one of the leading causes of cytotoxicity and is linked to many human physio-pathological conditions. In particular, myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) induced by OS is debilitating to quality of life, while no clear biological markers have been identified for diagnostic measures. Recently, impedance measurements of peripheral blood cells of ME/CFS patients have been shown as a promising approach to diagnose the disease. Inspired by this study and aiming to interrogate muscle cells directly, we investigated if broadband measurements of single muscle cells could differentiate normal and oxidatively stressed cell populations. We first optimized a protocol through H2O2 treatment to introduce oxidative stress to cultured rat L6 skeletal muscle cells. The treated cells were further characterized through broadband impedance spectroscopy of single cells using a microfluidic lab-on-a-chip system. The resulting dielectric properties of cytoplasm permittivity and conductivity are electrically distinct from normally cultured cells. The reflection and transmission coefficients, ΔS11 and ΔS21, of the normal cells are tightly clustered and closely resemble those of the cell-free solution across the frequency range of 9 kHz to 9 GHz. On the other hand, dielectric properties of the oxidized cells have a wide distribution in the GHz range, deviating both in the positive and negative directions from the normally cultured cells. Simulation results guide our hypothesis that the dielectric differences could be linked to ion alterations, while calcium imaging directly supports the contribution of calcium flux to the observed deviation of S parameters. The unique electrical profile associated with oxidized cells in the GHz frequencies provide a framework for future development of technologies to diagnose oxidative-stress related diseases such as ME/CFS.

Live Jurkat cells were trapped by dielectrophoresis on a coplanar waveguide and the resulted changes in its reflection and transmission coefficients were measured from 900 Hz to 40 GHz. The measurement confirms that the decrease of nucleus size in a cell increases its impacts on both the reflection and transmission coefficients. Being fast, compact and label free, broadband electrical sensing may be used to detect other changes of the nucleus morphology and DNA content, which could be useful for cancer diagnosis.

Aim Large tumor suppressor 1 (LATS1) is a Ser/Thr kinase to mediate Hippo signaling pathway and plays a pivotal role in tumor suppression. By searching the COSMIC database, we found a somatic missense mutation (NM_004690.4:c.2552C>T) of human LATS1 (NP_004681.1:p.851T>I) in two colorectal cancer cell lines, and investigated the role and underlying mechanism of this mutation in the colorectal tumorigenesis. Main methods We performed structural and biochemistry analyses to investigate the role of LATS1 T851I mutation in Hippo signaling activation and used the mouse xenograft model to assess the role of this mutation in the colorectal tumorigenesis. Key findings By structural and biochemistry approaches, we propose that T851 is an active residue other than Ser909 on the activation loop and is essential for LATS1 phosphorylation and kinase activity. We then reveal that T851I mutation in LATS1 not only destabilizes the phospho-Thr1079-LATS1, a prerequisite of LATS1 kinase activity, but also reduces its binding to the downstream effectors, YAP and TAZ. As a result, T851I mutation in LATS1 attenuates Hippo signaling and decreases its tumor-suppressor functions in the colorectal cancer. Significance The present study identifies the T851 as an essential residue for LATS1 kinase activity and uncovers the T851I mutation of LATS1 and consequent Hippo signaling suppression as a hitherto uncharacterized mechanism controlling colorectal tumorigenesis.

For the first time, the impedance spectrum of a live Jurkat T-lymphocytes human cell was characterized in a single sweep, spanning six decades of frequency from 9 kHz to 9 GHz. The ultra-wide bandwidth bridged the traditional impedance spectroscopy at kilohertz–megahertz frequencies with the recently developed microwave dielectric spectroscopy, which can probe the cell interior without being hindered by the cell membrane. Based on the measured scattering parameters and a simple cell model, an equivalent circuit of four nondispersive elements, including membrane resistance, membrane capacitance, cytoplasm resistance, and cytoplasm capacitance, was extracted and found sufficient to explain the so-called $\beta $ relaxation over the frequencies measured. These extracted cell parameters are in general agreement with the literature but are believed to be more accurate, giving the relatively small standard deviations, the configuration with a cell in intimate contact with the measurement electrodes, and the ultra-wide bandwidth of the measurement.

The detection of bacteria cells and their viability in food, water and clinical samples is critical to bioscience research and biomedical practice. In this work, we present a microfluidic device encapsulating a coplanar waveguide for differentiation of live and heat-killed Escherichia coli cells suspended in culture media using microwave signals over the frequency range of 0.5–20 GHz. From small populations of ∼15 E. coli cells, both the transmitted (|S21|) and reflected (|S11|) microwave signals show a difference between live and dead populations, with the difference especially significant for |S21| below 10 GHz. Analysis based on an equivalent circuit suggests that the difference is due to a reduction of the cytoplasm conductance and permittivity upon cell death. The electrical measurement is confirmed by off-chip biochemical analysis: the conductivity of cell lysate from heat-killed E. coli is 8.22% lower than that from viable cells. Furthermore, protein diffusivity increases in the cytoplasm of dead cells, suggesting the loss of cytoplasmic compactness. These changes are results of intact cell membrane of live cells acting as a semipermeable barrier, within which ion concentration and macromolecule species are tightly regulated. On the other hand, the cell membrane of dead cells is compromised, allowing ions and molecules to leak out of the cytoplasm. The loss of cytoplasmic content as well as membrane integrity is measurable by microwave impedance sensors. Since our approach allows detection of bacterial viability in the native growth environment, it is a promising strategy for rapid point-of-care diagnostics of microorganisms as well as sensing biological agents in bioterrorism and food safety threats.

Background: Hypoxia signaling plays a critical role in the development of lung adenocarcinoma (LUAD). We herein aimed to explore the prognostic value of hypoxia-related genes and construct the hypoxia-related prognostic signature for LUAD patients. Methods: A total of 26 hypoxia-related genes were collected. Five hundred thirteen and 246 LUAD samples were obtained from the Cancer Genome Atlas and Gene Expression Omnibus databases, respectively. Univariate Cox regression and LASSO Cox regression analyses were conducted to screen the hypoxia-related genes associated with the prognosis of LUAD patients, which would be used for constructing prognosis predictive model for LUAD patients. Multivariate Cox regression analysis was done to determine the independent prognostic factors. The Nomogram model was constructed to predict the prognosis of LUAD patients. Results: Based on 26 hypoxia-related genes, LUAD samples could be divided into 4 clusters with different prognoses. Among which, 6 genes were included to construct the Risk Score and the LUAD patients with higher Risk Score had worse prognosis. Besides, the Nomogram based on all the independent risk factors could relatively reliably predict the survival probability. And 9 types of immune cells’ infiltration was significantly differential between high and low risk LUAD patients. Conclusion: The Risk Score model based on the 6 crucial hypoxia-related genes could relatively reliably predict the prognosis of LUAD patients.

Electroporation of Jurkat T-lymphoma human cells was investigated using 10-MHz continuous waves and benchmarked against that at 100 kHz. Both cell poration and cell death were simultaneously monitored by fluorescence microscopy, and found to occur under approximately four times higher voltages at 10 MHz than that at 100 kHz. This weaker-than-expected increase in poration threshold could be explained by detailed analysis of the distributed effect often ignored in electroporation studies.

Osteoarthritis is the most common degenerative cartilage disease. A large number of studies have shown the close association between epigenetics and osteoarthritis. Histone methylation is a type of epigenetic modification, and the link between histone methylation and osteoarthritis has also been revealed. In this article, we summarize the correlation between methylation levels of different histones and osteoarthritis in an attempt to explore the changes and regulation mechanisms of histone methylation in osteoarthritis. It has been shown that there are possible relations between the methylation levels of different amino acids on histone H3 and the pathological development of osteoarthritis; specifically, the rise of methylation level at the lysine 4 would aggravate the pathological development of osteoarthritis, while the the pattern of lysine 9 and 27 would be the opposite. These results indicate the possible existence of a complex network of histone methylation modifications. And the specific regulation of histone methylation levels in different positions may delay or prevent the occurrence and development of osteoarthritis.

Bone tissue is essential for supporting and protecting our bodies. When bone fracture occurs, the loss of local conditions may cause a delay in healing, nonunion of the bone, or a persistent bone defect. Mesenchymal stem cell (MSC)-based cell therapy is a promising approach for fracture repair. MSCs are cultured, alone or on biomaterials, combined with cytokines, and supplied to the injury site. This chapter covers current understanding of MSC function in bone fracture healing, including the source of MSCs for fracture repair, internal (cytokines and chemokines) and external (physical stimulation) factors that affect MSC homing, and tissue-engineering applications of MSCs (immunogenicity, isolation/treatment approach, genetic modification, materials/growth factors, and clinical results). Here we aim to summarize clues to MSC application in fracture repair, to lay a foundation of stem cell–based therapy for future bone regeneration.

We present an ultra-wideband technique, based on a coplanar waveguide, for single-cell sensing. Numerical analysis carried out on the modeled system shows that variations of the scattering parameter S 21 , in the presence and in the absence of a spherical cell, are such that the cell can be sensed by means of scattering parameters measurements.

Recently, ultra-wideband electrical sensing has been developed as a fast, compact, and label-free technique to characterize a biological cell noninvasively and to extract its intracellular properties. This paper presents, for the first time, the use of the technique to sense the change in the nucleus size of a live Jurkat cell. The experiment is based on trapping and detrapping the cell by dielectrophoresis on a coplanar waveguide and measuring the return and insertion losses due to the presence of the cell from 9 kHz to 9 GHz. The results have been validated by traditional fluorescence microscopy. In the future, by extending the technique to detect changes in nucleus shape and DNA content, it could be used to distinguish cancerous cells from normal cells, for example.

Summary Articular cartilage injury and degeneration causing pain and loss of quality-of-life has become a serious problem for increasingly aged populations. Given the poor self-renewal of adult human chondrocytes, alternative functional cell sources are needed. Direct reprogramming by small molecules potentially offers an oncogene-free and cost-effective approach to generate chondrocytes, but has yet to be investigated. Here, we directly reprogrammed mouse embryonic fibroblasts into PRG4+ chondrocytes using a 3D system with a chemical cocktail, VCRTc (valproic acid, CHIR98014, Repsox, TTNPB, and celecoxib). Using single-cell transcriptomics, we revealed the inhibition of fibroblast features and activation of chondrogenesis pathways in early reprograming, and the intermediate cellular process resembling cartilage development. The in vivo implantation of chemical-induced chondrocytes at defective articular surfaces promoted defect healing and rescued 63.4% of mechanical function loss. Our approach directly converts fibroblasts into functional cartilaginous cells, and also provides insights into potential pharmacological strategies for future cartilage regeneration., Graphical Abstract, Highlights • A chemical method to derive functional murine articular chondrocytes from fibroblasts • Chemical-induced chondrocytes promote in vivo regeneration of articular defects • In single-cell analysis, intermediate reprogramming events resemble cartilage development, In this article, Ouyang and colleagues develop a chemical-driven direct reprogramming of mouse embryonic fibroblasts into PRG4+ chondrocytes, with a screen-defined cocktail VCRTc. Their induced chondrocytes promote in vivo cartilage functional regeneration. The dynamical cellular phenotypes were analyzed by single-cell RNA sequencing, illustrating the inhibition of fibroblast features and activation of chondrogenesis pathways in early reprogramming.

Objective: Multimodal characterization of a mammalian cell by optical and microwave techniques simultaneously during electroporation. Methods: Using a coplanar waveguide with a Jurkat cell trapped in the middle of its center conductor, continuous waves at 100 kHz of different amplitudes were applied for 20 s, while microwave transmission coefficients at 9 GHz were measured every 0.4 s. Results: The onset of electroporation was indicated by abrupt changes in both fluorescence intensity and transmission coefficient. Additionally, in measurements that lasted 300 s, the transmission coefficient was found to recover to the pre-poration level, while the fluorescence intensity remained different. Since the cells were confirmed viable through post-poration staining, the recovery of the transmission coefficient suggested reversible electroporation. Conclusion: These experimental results showed that the transmission coefficient could serve as a label-free indicator of cell membrane permeability during and after electroporation. Furthermore, it could be used to expeditiously differentiate reversible electroporation from the irreversible one. Significance: This study should aid fundamental analysis of cell physiology, as well as molecular delivery, in cell engineering and electrotherapy.

The crossover frequency around 50 kHz from positive force to negative force predicted by the Clausius-Mossotti function was experimentally validated in single-cell dielectropho-resis, despite the highly nonuniform electric field distribution between small and narrowly spaced electrodes, with the field distribution greatly disturbed by the cell. The validation was based on live Jurkat human T -lymphocyte cells that were resuspended in isotonic sucrose solution. With further validation on different cells in different solutions, better understanding can be obtained on how the Clausius-Mossotti function can be applied to a cell in an electrode gap comparable to the cell diameter. The understanding can then be used to help optimize the dielectrophoresis configuration and alaorlthm for more efficient sinale-cell maneuver.

For the first time, single-cell trapping, characterization, electroporation, and de-trapping were demonstrated by conveniently programming the frequency and power of the same ultra-wideband vector network analyzer (VNA). For example, trapping and de-trapping of a cell were accomplished by applying to a coplanar waveguide (CPW) a CW signal of 3 dBm and 5 MHz and 10 kHz, respectively, corresponding to attractive and repulsive dielectrophoresis. After a cell is trapped on the CPW, the VNA was switched to 9 dBm and 100 kHz for electroporation. Before and after electroporation, the cell was characterized from 9 kHz to 9 GHz by setting the VNA at −18 dBm to assess the effect of electroporation. This breakthrough can improve not only the accuracy, but also the throughput of single-cell wideband electrical characterization.

Based on a simple three-layer model, a network of three lumped elements of membrane capacitance, cytoplasm resistance, and cytoplasm capacitance was used to explain the so-called β dispersion in the dielectric properties of biological cells hypothesized six decades ago. Using the simple network and without resorting to frequency-dependent permittivity, nondispersive membrane capacitance, cytoplasm resistance, and cytoplasm capacitance were extracted from microwave scattering parameters measured on single cells without the complication of electrode polarization or boundary layer. The extracted values, as small as 1 pF for the membrane capacitance, as large as 0.1 M for the cytoplasm resistance, and as small as 10 fF for the cytoplasm capacitance, agreed with the hypothesized values, as well as order-of-magnitude estimates from physical properties of cells.

Traditionally, electromagnetic detection of biological cells was conducted at either radio or microwave frequencies, which was sensitive to either cellular or subcellular properties, respectively. This paper reports for the first time a single sweep from megahertz to gigahertz frequencies so that cell viability, membrane capacitance, cytoplasm resistance, and cytoplasm capacitance could be determined simultaneously. These parameters were determined with the aid of simple cell model and equivalent circuit, despite great challenges in ultra-wideband measurement and analysis. Although the extracted parameter values for Jurkat T-lymphocytes human cells, live or dead, were consistent with that reported in the literature, more careful measurement and analysis are required in the future, especially for electromagnetic detection over an even wider bandwidth. In any case, the present analysis confirmed that it was easier to assess cell viability around 100 MHz but cytoplasm characteristics around 10 GHz.

For the first time, broadband (0.5–20 GHz) electrical detection of live bacteria was successfully demonstrated on E. coli, despite their being small and adherent compared to mammalian cells such as Jurkat T-lymphoma human cells that had been detected by using a similar coplanar waveguide in conjunction with a microfluidic channel. Critical to the success was in suppressing the background drift of the insertion and return losses to the order of 0.01 dB. Presently, it is estimated that approximately 104 E. coli were required to yield a statistically significant signal in the insertion/return losses. Therefore, to detect a single bacterium, the measurement sensitivity and the background stability need to be further improved by orders of magnitude in the future.

Using a coplanar waveguide with a series gap in conjunction with dielectrophoresis trapping, consecutive S-parameter measurements between 0.5 and 20 GHz were quickly performed with and without a Jurkat cell trapped to compensate for a relatively noisy and drifting background. Based on sixteen measurements repeated on eight live cells and eight dead cells, differences in both return and insertion losses show two distinct distributions indicating either return loss or insertion loss alone can be used to distinguish a live cell from a dead one. Further, since the frequency dependence is generally linear or absent, discrete-frequency measurement (as opposed to sweep-frequency measurement) of return or insertion loss may suffice. If proven statistically by a much larger number of cells, this should greatly speed up the measurement to facilitate its eventual field use.

Electroporation of Jurkat human lymphoma cells were investigated under 10-MHz continuous waves and benchmarked against that at 100 kHz. Both cell poration and cell death were monitored in real time by fluorescence microscopy and found to occur at approximately three times higher voltages at 10 MHz than that at 100 kHz. This difference in voltage could not be completely accounted for by order-of-magnitude estimate of cytoplasm resistance and membrane capacitance. Better modeling and simulation of the cell structure and property are required to accurately predict the frequency dependence of electroporation.

Using a coplanar waveguide with a series gap in conjunction with dielectrophoresis trapping, consecutive S-parameter measurements between 0.5 and 20 GHz were quickly performed with and without a Jurkat cell trapped to compensate for a relatively noisy and drifting background. This allowed the small cytoplasm capacitance, on the order of 10 fF, to be reliably extracted. The extracted cytoplasm capacitance is within a factor of 2 of the previously reported value by using a shunt trap but is believed to be more accurate. The present technique can complement previously developed microwave and RF techniques in characterizing the capacitances and resistances of plasma and membrane for complete characterization of the electrical properties of a simple cell.