Metal-Free Molecular Magnet Dissolves in the Body While Tracking the Heart

A team of researchers from the University of North Carolina at Chapel Hill, Columbia University, Nanjing University and collaborating institutions has introduced a magnetic material that challenges a long-standing assumption in biomedical engineering: that useful magnets must be made of metal. In a study published in Nature Materials, the group describes a bioresorbable, metal-free molecular magnet derived from graphitic carbon nitride, a carbon- and nitrogen-based polymer better known from photocatalysis research than from the clinic. The material, which the authors call BioMFM, combines ferromagnetic strength comparable to metallic magnets with the ability to degrade harmlessly inside the body after its work is done.

The motivation is straightforward. Implantable sensors that monitor organs continuously are increasingly seen as a way to catch disease before symptoms appear, but the devices that could enable such monitoring face a fundamental materials problem. Conventional magnetic implants rely on metals such as iron, cobalt or nickel, which raise concerns about long-term toxicity, corrosion, interference with magnetic resonance imaging, and the need for a second surgery to remove them. Metal-free molecular magnets, by contrast, promise biocompatibility and resorbability, yet until now they have lacked the ferromagnetic strength needed for high-fidelity sensing at clinically relevant tissue depths.

The key to the new material lies in a chemical transformation called de-nitrogenation. By removing nitrogen atoms from the graphitic carbon nitride framework, the researchers create unpaired electron spin centres that become coupled through a reconstructed network of alternating pi and sigma conjugated bonds. This coupling confers robust spontaneous magnetization, meaning the material is ferromagnetic at room temperature without any external field, and that magnetization remains stable under physiological conditions. The authors verified the origin of the ferromagnetism theoretically, using first-principles calculations including crystal orbital Hamilton population analysis, and confirmed experimentally that the magnetism is strong enough to produce visible, macroscopic magnetic responses in bulk powder form.

To turn the material into a practical medical platform, the team embedded it in two well-established biodegradable polymers: poly(lactic-co-glycolic acid), or PLGA, and silk fibroin, the protein that gives silk its strength. The resulting composites can be fabricated as flexible epicardial patches that are foldable for catheter delivery. Supplementary videos accompanying the paper show a pre-folded, rose-petal-shaped patch held in a sheath mimicking a catheter lumen; when the sheath retracts, the patch blooms open within seconds, unfolding radially to enlarge its contact area against tissue. This bloomable design allows minimally invasive deployment and conformal attachment to organ surfaces without sutures.

The sensing architecture works in pairs. The internal implant, driven by the mechanical deformation of the organ it sits on, generates a time-varying magnetic flux that passes through the closed chest wall. Outside the body, a skin-interfaced array of Hall-effect sensors captures that flux and converts it into continuous readouts of organ motion. The signals are transmitted wirelessly to a smartphone-linked reader and a cloud-based analytics platform. Because the approach relies on magnetic coupling rather than acoustic, optical or electrical transduction, it requires no coupling gel, no vascular access and no optical alignment, and the authors report that it is robust against motion artifacts and variations in tissue impedance.

The team tested the system in porcine models, the standard large-animal platform for cardiovascular research. Epicardial patches deployed on the heart enabled continuous, untethered monitoring of myocardial dynamics over four weeks, during which the researchers tracked ejection fraction, a key clinical measure of how much blood the heart pumps with each beat. When benchmarked against standard-of-care echocardiography, the magnetic sensing approach delivered trajectories of clinical grade, suggesting it could support longitudinal physiological monitoring outside hospital infrastructure. Cardiac magnetic resonance imaging at day 28 confirmed that the patch remained conformally attached to the epicardium throughout repeated cycles of systolic contraction and diastolic relaxation, without detachment or migration.

Beyond the heart, the researchers showed that the material can be dispersed into injectable hydrogels for organ-scale sensing. Under ultrasound guidance, a BioMFM-integrated sodium alginate hydrogel was injected percutaneously onto the surface of a porcine liver, where the bolus appeared as a distinct hyperechoic region against the liver parenchyma, allowing precise minimally invasive placement. The hydrogel preserved the shear-thinning behaviour needed to flow through narrow-gauge clinical syringes even at loadings up to ten percent by weight, extruding smoothly without clogging. In the liver experiments, the magnetic markers enabled three-dimensional reconstruction of localized hepatic pathologies, pointing toward a future in which injected tracers map disease geometry inside solid organs.

What happens after the monitoring period is arguably the most distinctive feature. The material is designed to bioresorb, degrading benignly once its sensing mission is complete, which eliminates the retrieval surgery that metallic implants require and avoids the chronic foreign-body burden of permanent devices. The authors frame this as part of a broader degradation-by-design strategy in two-dimensional materials, in which chemical functionalization is used to tune biodegradability and safety. In the porcine studies, four weeks of continuous cardiac assessment were followed by benign bioresorption, closing the loop between function and disappearance.

The theoretical foundation of the work draws on a decade of research into metal-free magnetism in carbon nitride. Earlier studies predicted intrinsic half-metallicity and defect-related ferromagnetism in graphitic carbon nitride nanosheets, and recent work achieved strong ferromagnetism through atomic manipulation. The new study extends this line by engineering a molecular magnet whose spontaneous magnetization survives integration into polymer composites and physiological environments, a step that earlier radical-based organic magnets had not reached at clinically useful strength. The authors also employed machine-learning tools from cheminformatics, including ChemBERTa-style pretrained models, in their analysis workflow, and released their analysis code, firmware for an ESP32-S3 microcontroller and installation instructions on GitHub.

The clinical implications reach beyond cardiology. Acute heart failure and post-discharge follow-up after acute coronary syndrome remain areas where continuous, infrastructure-independent monitoring could change outcomes, and existing tools such as pulmonary artery catheters and periodic echocardiography offer only snapshots or require invasive access. A resorbable magnetic patch that reports ejection fraction continuously, read through the skin by a wearable sensor array, could in principle bring intensive-care-grade hemodynamic tracking to ordinary wards or even to patients at home. The injectable hydrogel variant extends the same logic to the liver, where elastography-based stiffness measurements are currently the dominant non-invasive tool but offer limited spatial resolution. The researchers caution that the work is at the large-animal stage, and human translation will require further safety and accuracy studies. Still, the demonstration that a metal-free, fully resorbable molecular magnet can deliver clinical-grade physiological trajectories over weeks marks a notable convergence of molecular magnetism, biodegradable electronics and wireless sensing, and suggests that the next generation of implantable diagnostics may be designed to vanish rather than endure.

Subject of Research: A bioresorbable metal-free molecular magnet for wireless deep-tissue and cardiac monitoring

Article Title: Bioresorbable metal-free molecular magnets enable untethered organ monitoring

Article References: Wu, Y., Yue, Z., Xing, S., Yang, D., Wang, J., Liu, Y., Cohen, H., Liu, L., Jiao, Q., Li, Z., Ali, H., Perera, C., Vahl, T. P., Ranard, L. S., Zhang, Z., Einstein, A. J., Zhang, A., Dashnaw, S., Huang, Y., … Bai, W. (2026). Bioresorbable metal-free molecular magnets enable untethered organ monitoring. Nature Materials. https://doi.org/10.1038/s41563-026-02759-4

Image Credits: AI Generated

DOI: 10.1038/s41563-026-02759-4

Keywords: molecular magnets, graphitic carbon nitride, bioresorbable materials, cardiac monitoring, implantable sensors, Hall effect sensing, ferromagnetism, PLGA, silk fibroin, injectable hydrogels, ejection fraction, Nature Materials