Controlling thermoreversibility and hole conductivity in thermoresponsive ionic biogels using phase morphology for neurohaptics

Science Advances · 2026-05-15

Integrating thermoreversibility with electrical conductivity in a unified hydrogel platform enables long-term, reusable through-hair neural interfaces. However, achieving both simultaneously remains challenging, as thermoreversibility demands network reorganization while conductivity necessitates network percolation. Here, we engineer phase morphology by controlling the components’ viscoelastic state during mixing. Ionically conductive nucleated morphologies illustrated by liquid-liquid phase separation exhibit rapid thermoreversibility, whereas electrically conductive bicontinuous phases demonstrated by viscoelastic phase separation achieve a marginal gel-sol transition and an ultralow storage modulus of ~1.7 kilopascals while simultaneously achieving a conductivity of 7.5 siemens per centimeter or transconductance of 5.1 millisiemens in an organic electrochemical transistor. Below this threshold, systems resemble nucleated behavior, whereas above it, superior semiconducting properties emerge, but phase transition capability is lost. These materials enable reusable through-hair neural interfaces to maintain low skin contact impedance of 1.6 kohm·cm 2 across different hair types for 3 days, facilitating stable event-related desynchronization detection during mechanical and electrical haptic sensation for personalized haptics.

Stability of performance in a hierarchical system during isometric force production and effects of visual feedback

Experimental Brain Research · 2025-11-27 · 2 citations

Abstract We address the underexplored role of visual feedback in ensuring stability of pressing force produced in isometric conditions by the two hands. We considered the task as a two-level hierarchy (total force, F TOT , and hand forces, F HAND ) and used the framework of the uncontrolled manifold hypothesis to quantify synergies stabilizing F TOT and F HAND . Young healthy persons performed steady-state forces with visual feedback and targets for the forces produced by each hand and/or for the total force. We quantified inter-trial and within-a-trial (across time windows) variance components affecting and not affecting F TOT and F HAND . Variables with visual feedback, F TOT or F HAND , showed force-stabilizing synergies reflected in the structure of variance, while variables without visual feedback failed to show such synergies. The synergies were consistently stronger when the feedback was continuous, compared to when the feedback disappeared when the cursor was inside the target. The results showed a strong dependence between variance that did not affect F TOT (within the corresponding solution space) and variance that affected each F HAND across the feedback conditions. Within-a-trial synergy indices were significantly lower than those in the inter-trial analysis. The data are interpreted as reflecting hierarchical control with synergies at both levels of the hierarchy, those that define F TOT and F HAND . These synergies get contributions from inter-trial force sharing variability and sensory feedback-based covariation of forces produced by the elements (fingers or hands) along individual trials. Combining inter-trial and within-a-trial analysis of variance may provide an important toolbox to explore cases of impaired control of action stability.

Metabolic profiling of the Chinese population with extreme longevity identifies Lysophospholipid species as potential biomarkers for the human lifespan

Maturitas · 2025-04-28

BACKGROUND: Metabolic regulation plays a crucial role in extending the healthspan and lifespan across multiple organisms, including humans. Although numerous studies have identified the characteristics of the metabolome and potential biomarkers in long-lived populations worldwide, the metabolome landscape of Chinese centenarians remains largely unknown. This study characterised the plasma metabolic profiles of Chinese centenarians and nonagenarians and identified potential biomarkers of longevity. METHODS: A global untargeted metabolomics approach was used to analyze plasma samples from 65 centenarians (average age 101.72 ± 1.46 years), 53 nonagenarians (average age 98.92 ± 0.27 years), 47 older individuals (average age 64.66 ± 3.31 years), and 35 middle-aged participants (average age 33.91 ± 3.53 years) recruited from the Lishui region, an area of China well known for the longevity of its population. RESULTS: The plasma metabolic profiles of centenarians and nonagenarians differed significantly from those of the two younger populations. Specifically, 211 and 114 differentially abundant metabolites (DAMs) were identified in the centenarian and nonagenarian groups, respectively. The majority of these DAMs were glycerophosphoethanolamines, glycerophosphocholines, fatty esters, fatty alcohols, fatty acyls, and fatty acids and conjugates. For example, the circulating levels of LysoPA (20:2), LysoPA (20:3), LysoPC (16:0), LysoPC (18:2), and LysoPE (20:4) were significantly lower in centenarians than in the older and middle-aged groups. A similar pattern was also observed in the nonagenarian population. Notably, the plasma levels of five DAMs - LysoPA (20:3), LysoPC (18:2), LysoPE (20:4), PG (18:0/18:1), and PG (18:1/18:2) - were significantly and continuously reduced with the ageing process. Pearson correlation analysis revealed that the reduced abundance of LysoPA (20:3), LysoPC (18:2), LysoPE (20:4), LysoPE (24:0), PG (18:0/18:1), and PG (18:1/18:2) was significantly and negatively associated with lifespan, from middle-age to centenarian. ROC analysis indicated that LysoPA (20:3), LysoPC (18:2), LysoPE (20:4), LysoPE (24:0), PG (18:0/18:1), and PG (18:1/18:2), as well as the combination of these six DAMs (AUC = 0.9074), had high predictive power for the human longevity phenotype. CONCLUSION: This study elucidated the plasma metabolic landscape of centenarians and nonagenarians in China and identified several potential biomarkers for predicting human lifespan. Our findings will aid in understanding the metabolic regulation of longevity and may promote the clinical practice of gerontology in the future.

Cross-person decomposition of surface electromyogram for efficient motor unit activity predictions

Journal of Neural Engineering · 2025-08-01 · 3 citations

Abstract Objective. Accurate prediction of motor unit (MU) discharge activity from surface electromyogram (sEMG) signals is critical for understanding neuromuscular control and for enabling practical neural interface applications. However, current MU decomposition approaches rely on person-specific data, limiting their generalizability. Approach. We developed a cross-person decomposition framework and validated the algorithm using synthesized high-density sEMG data by convoluting simulated MU firing spike trains with action potential templates derived from human experimental data. We first obtained separation matrix from multiple training subjects and applied them to decompose sEMG signals from unseen test subjects. This allowed us to obtain MU spike trains. The predicted outcomes were then compared with the ground truth across multiple metrics, including spike detection accuracy, MU firing rate (FR), waveform similarity of MU action potentials (MUAPs), and MU recruitment thresholds. Main results . Our results demonstrated strong agreement between predicted and true MU activity. Specifically, we found high <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mrow> <mml:msup> <mml:mi>R</mml:mi> <mml:mn>2</mml:mn> </mml:msup> </mml:mrow> </mml:mrow> </mml:math> values (⩾0.95) for the populational FR, and the coefficient of variation of FR remained stable across different MU retention thresholds. The MU similarity analyzes revealed that the predicted MUAPs closely matched ground truth counterparts both in waveform shape and spatial distribution. Furthermore, recruitment thresholds exhibited strong linear relation ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mrow> <mml:msup> <mml:mi>R</mml:mi> <mml:mn>2</mml:mn> </mml:msup> </mml:mrow> </mml:mrow> </mml:math> = 0.98 ± 0.006) with minimal error. Significance . These findings demonstrate the feasibility of efficient cross-person MU decomposition with minimal accuracy loss, laying the groundwork for generalized, plug-and-play myoelectric systems in neurophysiology, neuroprosthetic, and rehabilitation applications.

Ultrasoft Porous 3D Conductive Dry Electrodes for Electrophysiological Sensing and Myoelectric Control

UNC Libraries · 2025-07-26

Biopotential electrodes have found broad applications in health monitoring, human-machine interactions, and rehabilitation. Here, we report the fabrication and applications of ultrasoft breathable dry electrodes that can address several challenges for their long-term wearable applications - skin compatibility, wearability, and long-term stability. The proposed electrodes rely on porous and conductive silver nanowire based nanocomposites as the robust mechanical and electrical interface. The highly conductive and conformable structure eliminates the necessity of conductive gel while establishing a sufficiently low electrode-skin impedance for high-fidelity electrophysiological sensing. The introduction of gas-permeable structures via a simple and scalable method based on sacrificial templates improves breathability and skin compatibility for applications requiring long-term skin contact. Such conformable and breathable dry electrodes allow for efficient and unobtrusive monitoring of heart, muscle, and brain activities. In addition, based on the muscle activities captured by the electrodes and a musculoskeletal model, electromyogram-based neural-machine interfaces were realized, illustrating the great potential for prosthesis control, neurorehabilitation, and virtual reality.

From Gene to Enzyme: Multidimensional Decoding of the <scp>GGT</scp> Molecular Family and Its Clinical Tumor Diagnosis

Cancer Medicine · 2025-11-28

BACKGROUND: Gamma-glutamyltransferase (GGT) is a membrane-bound enzyme involved in glutathione metabolism and oxidative stress regulation. Although it is traditionally viewed as a liver function marker, emerging evidence suggests that its aberrant expression is closely associated with tumorigenesis, progression, and therapeutic resistance across multiple solid tumors. However, the comprehensive landscape of the GGT gene family and its clinical value in tumor diagnosis and prognosis remain unclear. OBJECTIVE: To systematically review the multidimensional roles of the GGT molecular family-including gene variants, mRNA isoforms, enzyme activity, and protein isoforms-in tumor biology and clinical oncology and to evaluate their potential as diagnostic and prognostic biomarkers. METHODS: We conducted a comprehensive literature review (PubMed, CNKI; inception-August 2025) focusing on (1) GGT family gene structure, expression patterns, and regulatory mechanisms; (2) GGT mRNA splice variants and isoforms; (3) GGT enzymatic activity and posttranslational modifications; and (4) clinical studies evaluating GGT as a biomarker in solid tumors. Data were synthesized narratively, emphasizing molecular mechanisms and clinical significance. RESULTS: The human GGT family comprises 13 homologous genes (e.g., GGT1-7 and GGTLC1-3) localized on chromosomes 20 and 22, which exhibit tissue-specific expression and functional diversity. GGT1 (22q11.23), which is the most extensively studied gene, is highly expressed in renal cell carcinoma (RCC), hepatocellular carcinoma (HCC), gastric cancer (GC), and breast cancer (BRC) and is correlated with poor prognosis and metastasis. GGT5 acts as a tumor suppressor in HCC but promotes progression in gastric cancer via PI3K/AKT pathway activation. GGT7 overexpression predicts poor survival in patients with HCC and glioblastoma. The GGT-II isoform demonstrated 78.7% sensitivity and 92.3% specificity for HCC diagnosis, outperforming AFP (AUC: 0.89 vs. 0.67). Serum GGT activity ≥ 50 U/L independently predicts poor overall survival (OS) in patients with HCC (HR: 1.78, 95% CI: 1.26-2.50). GGT mRNA splice variants (e.g., the GGT-I mRNA-B subtype) enhance early HCC detection when combined with AFP (sensitivity: 98%). CONCLUSIONS: The GGT molecular family plays pleiotropic roles in tumor biology via redox homeostasis, EMT, and immune modulation. The GGT1/5/7 and GGT-II isoforms represent promising biomarkers for early diagnosis, prognosis, and therapeutic targeting in multiple cancers. Future multicenter studies should validate GGT-based biomarker panels and elucidate the mechanisms underlying tissue-specific GGT functions.

Transcutaneous Nerve Stimulation Uncovers Spinal Reflex Contributions to Finger Force Coupling Patterns

2025-07-14

Understanding how spinal reflex pathways interact with biomechanical constraints to govern finger force control is critical for advancing neuroprosthetic design and neurorehabilitation. This study combined transcutaneous stimulation of the ulnar/median nerves with high-density electromyography (HD-EMG) and multi-digit force measurements to investigate how spinal reflex engagement (via H-reflex activation), electrode placement, and neuroanatomical variability shape finger interdependence. We evoked H-reflexes in the extrinsic finger flexors and quantified spinal excitability using H-reflex/M-wave (HM) ratios while recording force outputs across individual fingers and pairs. The index and middle fingers naturally generate more force than the ring and pinky fingers. When plotted, spinal reflex strength exhibited a slight upward trend, suggesting a potential relationship with greater force production and emphasizing the significance of individual neuromuscular strategies. The middle finger showed the strongest influence over neighboring finger movements, demonstrating how biomechanical coupling and neural crosstalk between fingers dominate the coordination of multi-finger actions. Different stimulation electrode configurations produced varying patterns of force distribution across the fingers, with some pairs enabling selective single-finger activation, while others triggered broader multi-finger responses. These results demonstrate that multi-digit force coupling during nerve stimulation arises from spinal excitability, electrode-dependent nerve recruitment, and individual anatomical differences. By isolating reflex-mediated force dynamics, this study advances hierarchical motor control models and underscores the need for personalized stimulation protocols to optimize neuroprosthetic interfaces and post-stroke rehabilitation.

Adaptive motor unit decomposition using a cross-validation-based update policy

Computers in Biology and Medicine · 2025-05-30 · 4 citations

Reduced Muscle Fatigue Using Continuous Subthreshold Kilohertz Stimulation of Peripheral Nerves

ArXiv.org · 2025-05-19

Functional electrical stimulation (FES) is a prevalent technique commonly used to activate muscles in individuals with neurological disorders. Traditional FES strategies predominantly utilize low-frequency (LF) stimulation, which evokes synchronous action potentials, leading to rapid muscle fatigue. To address these limitations, we introduced a subthreshold high-frequency (HF) stimulation method that employed continuous, charge-balanced subthreshold current pulses at kilohertz frequencies, designed to evoke motor unit (MU) activation similar to voluntary activation. We evaluated the effectiveness of HF stimulation on the reduction of muscle fatigue across different force levels (10 %, 25 %, and 40 % of maximum force). The HF stimulation utilized continuous charge-balanced, short pulses of 80 μs (at a 10 kHz frequency) targeted the ulnar/median nerve bundles. We compared the fatigue effects with conventional LF stimulation and voluntary muscle contractions. Our results indicated that HF stimulation maintained more sustained force outputs and muscle activation over a prolonged time compared with LF stimulation. The HF stimulation also evoked a more dispersed muscle activation pattern, similar to voluntary muscle contractions. These findings suggest that HF stimulation can significantly enhance the sustainability of muscle contractions and reduce muscle fatigue, potentially improving the efficacy and applicability of FES in clinical and home-based settings for individuals with neurological impairments.

Adaptive and Robust Motor Intent Decoding for Cross-Day Dexterous Finger Force Predictions

SSRN Electronic Journal · 2025-01-01