April 29, 2026 -- Researchers at the National Institutes for Quantum Science and Technology (QST), Japan, and The University of Tokyo, Japan, in collaboration with Kyushu University, Japan, have developed a new class of biocompatible molecular quantum nanosensors (MoQNs) that operate inside living cells. The study demonstrates that these nanosensors enable absolute temperature measurements with subcellular spatial resolution and detect radical-related spin signals in both the cytoplasm and nucleus of living cancer cells. The study finding was published in the journal Science Advances on April 29, 2026.

Quantitatively mapping physical and chemical states inside living cells remains a major challenge in modern biology. Existing intracellular quantum sensors, including nanodiamonds, quantum dots, and fluorescent proteins, can be powerful but often face limitations in material heterogeneity, thermometric specificity, or biocompatibility.

To overcome these issues, the research team developed MoQNs based on pentacene molecular spin qubits embedded in para-terphenyl nanocrystals and coated with the biocompatible surfactant Pluronic F127. This design provides molecular-level uniformity while preserving quantum coherence under physiological conditions.

Unlike conventional solid-state quantum sensors that rely on defect formation inside hard crystals, MoQNs are built by introducing molecular qubits into host nanocrystals without creating vacancies. This markedly reduced spectral variability from particle to particle and improved the reliability of single-particle absolute temperature measurements inside cells. The team first confirmed that MoQNs can be introduced into living cells while preserving viability. Across multiple assays, cells containing MoQNs maintained plasma membrane integrity, metabolic activity, and cell-cycle progression, indicating that the particles are compatible with live-cell measurements.

The researchers then demonstrated that MoQNs retain quantum functionality inside cells, including continuous-wave optically detected magnetic resonance (ODMR) detection, Rabi oscillations, spin-echo measurements, and T1 relaxometry. To improve thermometric precision, they further engineered the ODMR spectrum of the quantum sensors at the molecular level by tuning electron–nuclear interactions through the incorporation of fully deuterated pentacene, thereby creating dMoQNs.

Using dMoQNs, the team achieved absolute temperature sensing inside the cytoplasm of living cancer cells with high precision. They also found that intracellular temperature was consistently higher than the surrounding medium in a location-dependent manner. The researchers next extended the method to organelle-specific measurements. By delivering dMoQNs into the nuclei of living cancer cells, they were able to map absolute temperature at multiple intranuclear positions and observed localized thermal heterogeneity within the nucleus.

Beyond temperature sensing, the MoQN platform also enabled detection of radical-related external spins inside living cells. After inducing radical-generating conditions with hydrogen peroxide, the researchers observed spot-dependent changes in spin relaxation and coherence in both the cytoplasm and nucleus, indicating that the sensors can report on intracellular redox-associated environments as well as temperature.

Together, these findings establish MoQNs as a chemically versatile platform for quantum sensing in living cells.  

“This work shows that MoQNs can operate directly inside living cells while maintaining the precision needed for absolute thermometry,” said Dr. Ishiwata, Team Leader of the Quantum Bioengineering Team at QST. “We believe this opens a new route toward quantitative quantum measurement of intracellular environments.”

By combining molecular-level tunability, biocompatibility, and robust spin readout under physiological conditions, MoQNs open new opportunities for nanoscale thermometry, intracellular biochemical sensing, and future quantum-enabled biological and medical measurements.