Quantification of non-alcoholic fatty liver disease progression in 3D liver microtissues using impedance spectroscopy

Non-Invasive Detection of Early-Stage Fatty Liver Disease via an On-Skin Impedance Sensor and Attention-Based Deep Learning

Early-stage nonalcoholic fatty liver disease (NAFLD) is a silent condition, with most cases going undiagnosed, potentially progressing to liver cirrhosis and cancer. A non-invasive and cost-effective detection method for early-stage NAFLD detection is a public health priority but challenging. In this study, an adhesive, soft on-skin sensor with low electrode-skin contact impedance for early-stage NAFLD detection is fabricated. A method is developed to synthesize platinum nanoparticles and reduced graphene quantum dots onto the on-skin sensor to reduce electrode-skin contact impedance by increasing double-layer capacitance, thereby enhancing detection accuracy. Furthermore, an attention-based deep learning algorithm is introduced to differentiate impedance signals associated with early-stage NAFLD in high-fat-diet-fed low-density lipoprotein receptor knockout (Ldlr-/-) mice compared to healthy controls. The integration of an adhesive, soft on-skin sensor with low electrode-skin contact impedance and the attention-based deep learning algorithm significantly enhances the detection accuracy for early-stage NAFLD, achieving a rate above 97.5% with an area under the receiver operating characteristic curve (AUC) of 1.0. The findings present a non-invasive approach for early-stage NAFLD detection and display a strategy for improved early detection through on-skin electronics and deep learning.

Impedance Imaging of Cells and Tissues: Design and Applications

Due to their label-free and noninvasive nature, impedance measurements have attracted increasing interest in biological research. Advances in microfabrication and integrated-circuit technology have opened a route to using large-scale microelectrode arrays for real-time, high-spatiotemporal-resolution impedance measurements of biological samples. In this review, we discuss different methods and applications of measuring impedance for cell and tissue analysis with a focus on impedance imaging with microelectrode arrays in in vitro applications. We first introduce how electrode configurations and the frequency range of the impedance analysis determine the information that can be extracted. We then delve into relevant circuit topologies that can be used to implement impedance measurements and their characteristic features, such as resolution and data-acquisition time. Afterwards, we detail design considerations for the implementation of new impedance-imaging devices. We conclude by discussing future fields of application of impedance imaging in biomedical research, in particular applications where optical imaging is not possible, such as monitoring of ex vivo tissue slices or microelectrode-based brain implants.

Impedance Measurement System for Assessing the Barrier Integrity of Three-Dimensional Human Intestinal Organoids

Human pluripotent stem cell (hPSC)-derived intestinal organoids (HIOs) hold unprecedented promise for basic biology and translational applications. However, developing a quantitative method to evaluate the epithelial cell membrane integrity of HIOs as an in vitro intestinal barrier model is a major challenge because of their complex three-dimensional (3D) structure. In this study, we developed an impedance system to measure the change in electrical resistance of 3D HIOs depending on the integrity of the intestinal epithelial cell membrane, which can reflect functionality and maturity. The expression of intestinal maturation- and tight junction-related markers was significantly higher in HIOs matured in vitro by treatment with IL-2 than in control HIOs. Analysis of gap junction size indicated that mature HIOs have greater integrity, with approximately 30% more compact gaps than immature HIOs. We designed a multi-microchannel system controlled by the inhalation pressure where the HIO is loaded, which enhances the stability and sensitivity of the impedance signal. We demonstrated the applicability of the impedance system by showing the difference in resistance between control and mature HIOs, reflecting the expression of tight junction proteins and their maturation status. We also validated the impedance system by monitoring its resistance in real time during junctional damage to HIOs induced by a digestive agent. In summary, we suggest a quantitative method to directly quantify the physiological changes in complex 3D organoid structures based on impedance spectroscopy, which can be applied to noninvasively monitor live cells and therefore enable their use in subsequent experiments.

Association of impedance ratio with corrected Geriatric Nutritional Risk Index in older patients with nondialysis chronic kidney disease stage 5

BACKGROUND

The usual calculation of body mass index (BMI) can be misleading in patients with advanced chronic kidney disease (CKD) because their altered fluid balances may not be reflected. We obtained corrected BMI (cBMI) and corrected Geriatric Nutritional Risk Index (cGNRI) values and investigated whether the impedance ratio (IR) of 200/5 kHz, measured using bioimpedance spectroscopy, was associated with cGNRI in older patients with nondialysis CKD stage 5 (CKD5-ND).

METHODS

Patients over 65 years old (n = 118) were divided into groups by cGNRI tertiles. The differences between the correlations were tested using Steiger's z-test. The IR and cBMI were used as both continuous and categorical variables in the regression analyses to determine the factors that were independently associated with the cGNRI.

RESULTS

Patients in the third cGNRI tertile had a significantly lower mean IR than those in the other 2 tertiles (P < .001). Across the 3 cGNRI tertile groups, the IR was incrementally lower in the higher cGNRI tertiles (P for trend < .001). The Steiger's z-test showed that the IR had a significantly stronger correlation with cGNRI than cBMI had with cGNRI. In the multivariable linear regression analyses, the IR was independently associated with the cGNRI, after adjusting for various confounders.

CONCLUSION

The current results revealed that the IR was a more sensitive indicator of nutrition risk than BMI and was independently associated with cGNRI in older patients with CKD5-ND. Our study suggests that the IR is an appropriate tool for nutrition risk screening.