For decades, physicists have pondered whether electrons could ever behave like an ideal fluid—a state where they collectively move without scattering from impurities or lattice defects, giving rise to frictionless flow properties analogous to superfluids or quark-gluon plasmas. Conventional materials have continually thwarted efforts to observe such behavior due to imperfections that scatter electrons and mask the subtle hydrodynamic effects. However, graphene, with its distinct two-dimensional honeycomb lattice and exceptional electronic properties, has long been regarded as an ideal platform for exploring novel quantum states. Yet, direct evidence of hydrodynamic electron flow behaving as a perfect fluid has remained elusive—until now.

The IISc-led team meticulously prepared and engineered ultra-high-purity graphene samples, eliminating most extrinsic sources of disorder and defects. Using these pristine specimens, they simultaneously measured electrical conductivity—the ease with which electrons carry charge—and thermal conductivity, which reflects the ability of the material to transfer heat via electron motion. Surprisingly, rather than maintaining the well-established proportionality predicted by the Wiedemann-Franz law, their experiments revealed a striking inverse relationship. As the electrical conductivity increased, thermal conductivity decreased dramatically, breaking the long-held principle that heat and charge conductance should scale hand-in-hand in metals.

This profound violation of the Wiedemann-Franz law by more than two hundredfold at low temperatures signals the emergence of a unique quantum liquid regime. At the heart of this behavior is the so-called Dirac point, where graphene’s electronic band structure yields massless charge carriers and where electrons neither conform to metallic nor insulating states. Near this point, electrons abandon their typical particle-like individuality and instead coalesce into a collective “Dirac fluid.” This fluid flows similarly to water but displays quantum effects such as minimal viscosity—far lower than any classical fluid—thus qualifying it as the closest experimental realization of a perfect quantum fluid in a solid.

The researchers explain that, in the Dirac fluid regime, both charge and heat transport depend on a universal quantum of conductance—a fundamental constant describing the minimal resistance electrons experience when flowing across materials. This universality highlights the exotic nature of electron interactions within graphene, governed more by intrinsic quantum critical phenomena than by material-specific imperfections. Consequently, electrical and thermal conduction processes decouple fundamentally, invalidating traditional conductivity models that treat electrons as largely independent carriers.

To characterize the fluidity quantitatively, the team measured the fluid’s viscosity—a parameter indicating internal friction opposing flow. Their results revealed an extraordinarily low viscosity, on par with other strongly correlated quantum systems such as the quark-gluon plasma observed in ultra-high-energy collisions at CERN’s Large Hadron Collider. Such correspondence suggests that the graphene Dirac fluid can serve as a low-energy table-top analog to explore extreme quantum states usually accessible only in particle physics experiments and astrophysical scenarios.

Beyond its fundamental importance, this discovery positions graphene as an unparalleled quantum laboratory for investigating rich phenomena like black-hole thermodynamics and entanglement entropy scaling, concepts that historically belong to the realms of cosmology and quantum information theory. The ability to simulate and probe these exotic states in a controlled laboratory environment will undoubtedly accelerate progress across condensed matter physics and quantum technologies.

Technological implications of this research are equally profound. The emergence of a quantum perfect fluid phase in graphene paves the way for quantum sensors engineered to exploit the decoupling of charge and heat flows, granting these devices heightened sensitivity. Potential applications include amplification of weak electrical signals and detection of minute magnetic fields, advancing fields such as quantum metrology and medical imaging.

Professor Arindam Ghosh of IISc, one of the study’s senior authors, emphasizes the enduring richness of graphene’s physics despite two decades of intense scrutiny. “It is amazing that there is so much to do on just a single layer of graphene even after 20 years of discovery,” he notes, underscoring the material’s continual capacity to surprise and inspire.

First author Aniket Majumdar explains that this work marks a key milestone in realizing a Dirac fluid state experimentally. He points out that this unique electronic phase is “an exotic state of matter which mimics the quark-gluon plasma,” highlighting its importance in bridging condensed matter and high-energy physics. The study’s observation that electron flow near the Dirac point mimics such a nearly perfect fluid feeds into longstanding theoretical predictions regarding quantum criticality and hydrodynamic transport in two-dimensional materials.

The team’s approach involved precise tuning of graphene’s carrier density to reach the Dirac point through electrostatic gating techniques, enabling unprecedented control over the electron fluid’s properties. By cooling the samples to cryogenic temperatures, they suppressed extrinsic thermal scattering and unveiled intrinsic collective electron phenomena that remain hidden at higher energies.

Their findings demonstrate a new universality class of quantum critical flow, distinct from classical or previously known quantum transport regimes. This universality is characterized by the reliance on fundamental constants governing conductance rather than sample-specific parameters, reinforcing graphene’s status as a model system to study quantum fluids with direct experimental accessibility.

As a result, the IISc team’s breakthrough establishes a vibrant new frontier in quantum materials research. By taking quantum fluid dynamics out of particle accelerators and astrophysics labs and placing it squarely in a table-top graphene device, this study promises to reshape fundamental physics paradigms and to spark technological innovations exploiting quantum hydrodynamics in future nanoelectronic systems.

The research is published in the prestigious journal Nature Physics, amplifying its impact and signaling global recognition for this milestone achievement. This advance in understanding electron behavior at the quantum critical point in graphene not only enriches our fundamental knowledge of quantum many-body systems but also energizes diverse areas of physics—ranging from condensed matter to quantum information and high-energy theory.

As materials science continues to push boundaries, discoveries such as this spotlight the profound possibilities emerging from atomically thin materials. Graphene’s exceptional electron fluidity offers a glimpse into an extraordinary quantum world, where electrons flow as a near-perfect liquid, setting the stage for innovations that transcend conventional electronics and unveil unexplored quantum frontiers.

Subject of Research: Quantum fluid behavior of electrons in ultraclean graphene

Article Title: Universality in quantum critical flow of charge and heat in ultraclean graphene

News Publication Date: 13-Aug-2025

Web References:
https://www.nature.com/articles/s41567-025-02972-z
http://dx.doi.org/10.1038/s41567-025-02972-z

Image Credits: Aniket Majumdar

Keywords

Graphene, quantum fluid, Dirac fluid, electron hydrodynamics, quantum criticality, Wiedemann-Franz law violation, quantum conductance, minimal viscosity, quantum transport, graphene electronics, ultraclean graphene, quantum sensors

Recent groundbreaking research spearheaded by the Department of Developmental Biology and Genetics (DBG) at the Indian Institute of Science (IISc) has unveiled critical insights into how this molecular traffic management falters in Type 2 diabetes (T2D). The study, conducted under the guidance of Assistant Professor Nikhil Gandasi, presents a detailed investigation into glucose transporter (GLUT) dynamics within β-cells, highlighting a process heretofore overlooked that could revolutionize therapeutic strategies for diabetes management. This research is published in the prestigious Proceedings of the National Academy of Sciences (PNAS).

At the heart of glucose uptake in pancreatic β-cells are glucose transporters, integral membrane proteins that facilitate the passage of glucose into the cell. In human β-cells, GLUT1 predominates as the principal mediator of glucose entry, whereas in murine models, GLUT2 assumes this role. The IISc team meticulously tracked the behavior of these transporters using advanced live-cell imaging techniques, employing super-resolution microscopy under the Zeiss-Elyra system to observe GLUT1 and GLUT2’s dynamic trafficking in response to fluctuating glucose concentrations.

Their observations reveal that in healthy pancreatic β-cells, the rise in blood glucose triggers a rapid mobilization of GLUT transporters to the cell membrane. This trafficking is a tightly regulated cycle involving clathrin-mediated endocytosis—a process where cell surface proteins are internalized via vesicles coated with the protein clathrin, allowing for the recycling and replenishment of GLUTs at the membrane. This molecular shuttle ensures a consistent supply of glucose transporters available for efficient glucose uptake, effectively kickstarting the cellular metabolism that culminates in insulin secretion.

However, this finely tuned mechanism exhibits significant defects in β-cells derived from individuals with T2D. The study uncovers a marked reduction in the number of GLUT transporters reaching the β-cell surface, accompanied by disrupted cycling dynamics. The impaired trafficking results in a decreased glucose influx, undermining the cell’s capacity to trigger insulin release adequately. Crucially, this inefficiency extends to the docking process of insulin granules—particularly those primed for swift secretion in postprandial states—undermining the cell’s responsiveness to metabolic demands.

This revelation pivots the scientific community’s focus to an earlier stage of glucose regulation within β-cells—a step preceding intracellular glucose metabolism that has been relatively understudied. “Most research has concentrated on intracellular signalling cascades activated post-glucose entry,” notes Anuma Pallavi, PhD student and first author of the study. “We zeroed in on the dynamics governing glucose transporter trafficking, illuminating a pivotal dysfunction unique to diabetic β-cells. This presents an opportunity to develop targeted interventions that restore β-cell function by correcting transporter mismanagement.”

The implications of this discovery are far-reaching. Existing diabetes therapies predominantly target insulin sensitivity in peripheral tissues such as muscle and adipose cells, striving to improve glucose uptake and utilization outside the pancreas. By contrast, the new findings highlight the intrinsic deficiency within β-cells themselves—specifically in glucose uptake machinery—as an equally critical, yet underexploited therapeutic target.

Emblematic of this paradigm shift is previous work from the Gandasi laboratory identifying Pheophorbide A, a plant-derived bioactive molecule capable of enhancing insulin release via interaction with glucose transporters. Such compounds, designed to modulate GLUT trafficking and enhance plasma membrane transporter density, could potentially arrest or even reverse β-cell dysfunction in diabetic patients. This new approach embodies a precision medicine strategy, envisaging treatments tailored to an individual’s metabolic and molecular profile.

Molecularly, the process of GLUT trafficking is a complex regulatory network involving multiple signalling proteins and endocytic pathways. The role of clathrin-mediated endocytosis, detailed extensively in this study, is crucial for maintaining transporter homeostasis on the β-cell surface. Disruptions in this pathway can precipitate diminished transporter availability, leading to attenuated glucose entry and a cascade of metabolic insufficiencies culminating in reduced insulin secretion.

Furthermore, the study’s systematic approach involved comparative analyses of human and mouse β-cells, validating the conserved and divergent aspects of GLUT isoforms across species. This cross-species perspective enhances translational relevance, paving the way for preclinical testing and potential clinical applications.

The visualization of β-cells with super-resolution microscopy provided unprecedented spatial and temporal resolution of GLUT transporter puncta at the cell membrane and within intracellular compartments. Through these imaging studies, researchers discerned the kinetics of transporter recruitment and retrieval, elucidating how pathological states alter transporter distribution.

This transformative research heralds a new era in diabetes biology, spotlighting the intersection of cellular trafficking dynamics and metabolic regulation. By restoring the delicate balance of GLUT transporter cycling, it may become feasible to enhance insulin secretion capacity in T2D patients, potentially mitigating the progression of the disease and improving glycemic control.

As the prevalence of T2D continues to escalate globally, particularly fueled by lifestyle changes and aging populations, novel insights into β-cell physiology and pathology are urgently needed. The IISc team’s contribution offers a fertile ground for future investigations aimed at deciphering the molecular players involved in GLUT trafficking and their modulation by pharmacological agents.

Looking forward, unraveling the signaling mechanisms that regulate GLUT transporter cycling and their perturbations in diabetes could identify additional therapeutic targets. Combined with advances in molecular imaging and bioinformatics, these insights promise to refine our understanding of β-cell biology and foster the development of innovative, cell-centric diabetes treatments.

In conclusion, this study transcends traditional paradigms by situating glucose uptake dynamics as a pivotal determinant of insulin secretion efficacy. The elucidation of GLUT trafficking deficits in diabetic β-cells opens promising avenues for intervention, emphasizing the need for continued research in molecular traffic regulation within endocrine cells. Such endeavors hold the potential to transform diabetes management, steering it towards more personalized and efficacious therapeutic strategies.

Subject of Research: Pancreatic β-cell glucose transporter dynamics and their role in insulin secretion regulation and dysfunction in Type 2 diabetes.

Article Title: Dynamic GLUT trafficking at high glucose levels enhances insulin secretion: Dysregulation leads to decreased insulin secretion during type 2 diabetes.

News Publication Date: 14-Aug-2025

Web References:

• Proceedings of the National Academy of Sciences (PNAS)
• DOI Link

Image Credits: Anuma Pallavi, Indian Institute of Science (IISc)

β-glucuronidase is an evolutionarily conserved enzyme, omnipresent in a diverse array of life forms from microbes to mammals. Biochemically, its primary function involves hydrolyzing glucuronic acid conjugates, acting on glycosidic bonds within various substrates. Clinically, its elevated expression serves as a biomarker indicating the presence of several diseases. Notably, increased β-glucuronidase levels correlate with liver cancer progression, as well as other malignancies such as colon, breast, and renal cancers. The enzyme’s activity is also heightened in infectious states like urinary tract infections and immunodeficiency syndromes including AIDS, reinforcing its medical significance as a diagnostic target.

Traditional enzyme detection methodologies, such as colorimetric assays and conventional fluorescence techniques, have long been hindered by limitations in sensitivity and susceptibility to background interference. Fluorescent probes typically suffer from short-lived excited states, which overlap with endogenous autofluorescence, complicating signal interpretation. The research team ingeniously circumvents these issues by employing terbium ions, known for their exceptionally long-lived luminescent excited states. This unique trait enables temporal separation of the desired luminescent signal from the background noise, vastly improving detection clarity and accuracy.

The conceptual foundation of this sensor lies in the chemistry of rare earth metal luminescence combined with targeted enzymatic activation. Terbium ions are embedded within a specially formulated gel matrix derived from bile salts, creating a stable fluorescent environment. The gel serves both as a scaffold to hold terbium ions in proximity and as a medium facilitating efficient energy transfer processes. An organic molecule, 2,3-Dihydroxynaphthalene (2,3-DHN), chemically masked with glucuronic acid, is incorporated into this matrix. When β-glucuronidase enzymatically cleaves the glucuronic acid moiety, free 2,3-DHN is released and acts as an antenna to sensitize terbium luminescence.

The operational mechanism is elegantly straightforward yet sophisticated. Upon UV light excitation, free 2,3-DHN absorbs energy and transfers it efficiently to the terbium ions, resulting in intensified green luminescence. This energy transfer process relies on the Förster resonance energy transfer (FRET) principle, wherein the close spatial arrangement of antenna molecules and lanthanide ions within the gel matrix ensures efficient excitation of terbium’s characteristic emission. Hence, enzyme activity directly modulates luminescence intensity, providing a measurable and reliable signal for β-glucuronidase presence.

For real-world applicability, the system was adapted into a paper-based format by immobilizing the terbium-gel matrix onto paper discs. This innovation allows the sensor to be easily handled, stored, and deployed without elaborate laboratory infrastructure. Samples containing β-glucuronidase treated with the masked 2,3-DHN are applied onto the paper sensor. Subsequent exposure to UV light reveals a pronounced green luminescent signal proportional to enzyme concentration. This visual “turn-on” response is both striking and quantifiable, representing a significant advancement over complex instrumentation typically required for such assays.

One of the most compelling aspects of this technology is its capacity for straightforward analysis. The enhanced luminescence can be detected using a standard UV lamp, and image analysis software such as ImageJ — an open-source and freely available tool — can quantify emission intensity. This approach eliminates the need for expensive fluorescence spectrometers or high-end diagnostic devices, democratizing access to important biomarker detection. The sensor exhibits a limit of detection (LOD) of approximately 185 ng/mL for β-glucuronidase, a remarkable threshold nearing clinical relevance.

To contextualize this sensitivity, β-glucuronidase concentrations in biological fluids exceeding around 1,000 ng/mL are often indicative of severe liver conditions, including decompensated cirrhosis, a common precursor to liver cancer. Detecting enzyme levels well below this pathological range enables early intervention opportunities, potentially improving patient outcomes through timely diagnosis. Moreover, the sensor’s responsiveness to a broad spectrum of related diseases could extend its utility beyond oncology, encompassing neonatal jaundice diagnostics and monitoring drug-induced toxicities.

The broader implications of this research extend to global health and disease management. Liver cancer remains a leading cause of cancer mortality worldwide, frequently diagnosed at advanced stages where treatment options are limited. The advent of an affordable, sensitive, and easy-to-use diagnostic tool aligns with urgent calls for improved screening methods, particularly in low- and middle-income countries where access to medical facilities is constrained. Additionally, the paper-based sensor’s portability and rapid response time position it as a viable candidate for point-of-care testing.

Before this innovation can enter clinical practice, further validation through extensive clinical trials is essential. The research team acknowledges this need and remains optimistic about the sensor’s translational potential. Efforts will likely focus on evaluating sensor performance across diverse patient populations, investigating long-term stability, and determining compatibility with complex biological samples such as blood or urine. Should these studies affirm initial findings, the terbium-based sensor could significantly reduce the cost and complexity of liver cancer biomarker detection.

This research also underscores the expanding utility of rare earth luminescent materials in biomedical applications. Terbium’s unique photophysical features, including narrow emission bands and prolonged excited state lifetimes, are harnessed here to strike a balance between sensitivity and operational simplicity. The researchers’ novel approach marries inorganic chemistry, materials science, and enzymology, exemplifying interdisciplinary innovation aimed at solving pressing healthcare challenges.

In summary, the terbium-based paper sensor developed at IISc represents a paradigm shift in enzyme detection and cancer biomarker diagnostics. Its clever design exploits enzymatic specificity and photophysical synergy to produce a highly sensitive but user-friendly assay. By enabling rapid and reliable detection of β-glucuronidase without the need for costly instrumentation, this technology holds promise to democratize early cancer detection, ultimately saving lives through early diagnosis and improved disease management.

Subject of Research: Detection of liver cancer biomarker β-glucuronidase using a terbium-based luminescent sensor.

Article Title: Turn-On Luminescent Detection of Liver Cancer Biomarker β-Glucuronidase Using a Terbium-Based Paper Sensor

News Publication Date: 10-Jun-2025

Web References:
https://aces.onlinelibrary.wiley.com/doi/10.1002/asia.202401975
http://dx.doi.org/10.1002/asia.202401975

Image Credits: UM Group

Keywords: β-glucuronidase detection, liver cancer biomarker, terbium luminescence, paper-based sensor, rare earth metals, enzyme assay, fluorescence energy transfer, point-of-care diagnostics, bioluminescent probe, low-cost cancer screening, 2,3-Dihydroxynaphthalene, gel matrix

In light of these challenges, recent research spearheaded by experts from the Department of Instrumentation and Applied Physics (IAP) at the Indian Institute of Science (IISc) provides a promising alternative. Their innovative technique, known as photoacoustic sensing, offers a non-invasive approach to glucose measurement, marking a significant evolution in diabetic self-care. Harnessing the interactions between light and biological tissue, this method transforms how we understand glucose detection.

The process begins when a laser beam is directed onto biological tissue. The interactions that follow are fascinating. As the tissue absorbs the laser light, even a slight increase in temperature occurs, typically less than one degree Celsius. This minute temperature change prompts the tissue to expand and contract, creating vibrations that manifest as ultrasonic sound waves. These waves are subsequently captured by sensitive detectors, revealing critical information about the tissue’s composition without causing any damage.

The team took this foundational concept a step further by specifically targeting glucose measurement. By employing polarised light—light waves oscillating in a single direction—they unlocked a unique characteristic of glucose, a chiral molecule. This characteristic means glucose’s structure can affect how light interacts with it, a property that the researchers exploited to track glucose concentration.

Interestingly, glucose has the ability to rotate the orientation of polarised light. The degree of this rotation bears a direct relationship to the concentration of glucose present. The researchers discovered a correlation between the intensity of the emitted sound waves and the level of glucose present. According to Jaya Prakash, an Assistant Professor at the IAP and the corresponding author of the study published in the esteemed journal "Science Advances," this relationship is profound.

The implications of this research are far-reaching. The team demonstrated that by accurately measuring the intensity of the acoustic signal, they could estimate glucose concentrations with remarkable precision. In their experiments, they not only tested glucose in water but also in serum solutions and even slices of animal tissue. The accuracy of these measurements at varying tissue depths indicates a potential for real-world applications far beyond laboratory settings.

Further diving into the technical intricacies, the researchers explained that sound waves have a unique property—they do not scatter much when traversing through tissue. Given this trait, they could map acoustic signals to their originating depths within the tissue, providing a level of detail that traditional methods simply cannot offer. This advancement suggests a future where continuous glucose monitoring could become both non-invasive and extremely accurate, fundamentally transforming diabetes management.

A compelling pilot study was conducted to showcase the practical application of this technology. During this study, researchers monitored the blood glucose levels of a healthy participant across three days, documenting fluctuations in glucose concentration before and after meals. Swathi Padmanabhan, a PhD student and first author of the paper, revealed the challenges the team faced in creating an effective setup for their experiments. Currently, the laser source they utilized for these measurements is quite specialized, generating small nanosecond pulses that are both expensive and bulky.

This leads to the ongoing pursuit of refining this technology further. As Padmanabhan noted, creating a more compact version of the laser source is paramount for this innovation to transition from the lab to clinical practice. Collaborative efforts in the lab are already underway to streamline this setup for wider applicability in everyday healthcare.

The implications of this technology extend beyond glucose measurement. The researchers are optimistic that this technique can be adapted for a wide array of chiral molecules, simply by altering the wavelength of the light used. In their study, they also succeeded in estimating the concentration of naproxen, a commonly used analgesic, in an ethanol solution, thus highlighting the versatility of their photonic method. With many pharmaceutical drugs exhibiting chiral properties, the potential applications in healthcare and diagnostics are vast and varied.

Overall, the researchers’ findings paint a promising picture for the future of disease management. As healthcare increasingly seeks non-invasive techniques that minimize discomfort while maximizing accuracy, technologies like photoacoustic sensing become crucial. The path they have paved not only addresses the pressing need for easier glucose monitoring for diabetes patients but also opens up avenues for real-time monitoring of various other substances, enhancing the landscape of diagnostics considerably.

The journey from traditional invasive techniques to cutting-edge non-invasive technologies like photoacoustic sensing exemplifies the advancements in biomedical engineering. As the scientific community continues to explore the potential of this innovative method, patient care may soon become more efficient, less invasive, and ultimately more effective, allowing those living with chronic conditions to manage their health with unprecedented ease.

Subject of Research: Non-invasive glucose monitoring using photoacoustic sensing.
Article Title: Deep Tissue Sensing of Chiral Molecules using Polarization Enhanced Photoacoustics.
News Publication Date: 19-Mar-2025.
Web References: Science Advances.
References: N/A.
Image Credits: G Puneeth.

Keywords

Diabetes, non-invasive monitoring, glucose sensing, photoacoustic sensing, polarised light, chiral molecules, biomedical engineering, diagnostics.