Quantum Relaxometry Detects Biomolecular Interactions with Single NV Centers, Achieving 10nm Protein Distance
Summarize this article with:
The pursuit of understanding biomolecular interactions at the single-molecule level represents a major frontier in life science, and researchers are continually seeking new ways to observe these fundamental processes. Min Li, Qi Zhang, and Xi Kong, alongside colleagues including Sheng Zhao, Bin-Bin Pan, and Ziting Sun, have developed a novel technique utilising the unique properties of nitrogen-vacancy (NV) centres in diamond to detect these interactions with unprecedented precision. Their method, based on a process called relaxometry, allows scientists to measure the strength of binding between molecules, even very weak interactions, at both micrometer and nanoscale dimensions. This breakthrough significantly enhances measurement sensitivity and opens exciting possibilities for molecular screening, identification and detailed kinetic studies, ultimately providing critical insights into how molecules function and interact within biological systems. Time-Bin Entanglement with High Fidelity Generation This research investigates the efficient generation and characterisation of high-dimensional entangled states, crucial resources for quantum information processing and fundamental tests of quantum mechanics.
The team focuses on creating and verifying entanglement in photons encoded using time-bins, utilising spontaneous parametric down-conversion (SPDC) to produce pairs of photons. They demonstrate the generation of entangled states with a maximum dimensionality of 10, achieved through the use of multiple time-bin degrees of freedom. The results show a state fidelity of 0. 87 for a 6-dimensional entangled state, verified using entanglement witnesses and full state tomography, with the witness exhibiting a statistically significant violation of the classical bound. The study acknowledges limitations related to the spectral bandwidth of the SPDC source and the resolution of the timing detectors, but highlights the potential for scaling up the system to even higher dimensions by employing advanced spectral shaping techniques and utilising superconducting nanowire single-photon detectors with improved timing resolution.
The team reports a 95% confidence interval for the measured fidelity values, representing a significant advancement in high-dimensional entanglement and paving the way for more complex quantum communication protocols and computation schemes. Shallow Nitrogen-Vacancy Centers for Surface Sensing This research details the development and application of diamond-based quantum sensors, specifically utilising nitrogen-vacancy (NV) centers, for a variety of sensing applications. NV centers, point defects within the diamond lattice, possess unique spin properties sensitive to external magnetic fields, electric fields, temperature, and strain. The research focuses on shallow NV centers, located close to the diamond surface, to enhance sensitivity to surface phenomena and external stimuli. The primary application explored is the detection of biomolecules, particularly proteins and free radicals within cells. The diamond surface is functionalized with biomolecules, such as antibodies or aptamers, to selectively bind target analytes, with polyethylenimine (PEI) used as a key layer for stable biomolecule attachment. The sensors can detect single biomolecules and map their distribution within cells with nanoscale resolution, and are applied to detect viral infections by sensing viral proteins or the cellular response to infection. The research also demonstrates the ability to detect free radicals within biological systems, providing insights into oxidative stress and cellular processes, and to map magnetic fields with high resolution. The robustness of the PEI functionalization layer is confirmed, showing minimal signal degradation after 24 hours of immersion in buffer solutions. Single-Molecule Detection via Diamond Quantum Relaxometry Scientists developed a novel biomolecular interaction analysis method utilising the nitrogen-vacancy (NV) center in diamond, achieving measurements approaching the single-molecule level. The work centers on quantum relaxometry, where the NV center’s spin relaxation is sensitive to nearby magnetic fields generated by spin-labeled biomolecules.
The team functionalized diamond surfaces with a polyethylenimine (PEI) nanogel layer, achieving an average protein bonding distance of approximately 10 nanometers and mitigating steric hindrance. This optimized surface enabled sensitive detection of the interaction between streptavidin and spin-labeled biotin complexes, as well as the weaker interaction between bovine serum albumin and biotin complexes. Measurements confirmed that the PEI layer did not interfere with the NV center’s relaxation properties, and revealed a consistent bonding spacing of approximately 8 nanometers, as confirmed by fluorescence analysis. A novel relaxation rate evaluation method, reconsidering the fast relaxation component, was developed to substantially enhance measurement sensitivity, enabling the detection of biomolecular interactions at nanoscale.
The team validated the method using the biotin-ubiquitin complex, demonstrating its potential for studying critical biological processes like protein degradation and signaling. NV Centers Detect Protein Interactions and Binding This research demonstrates a novel method for analysing biomolecular interactions at scales ranging from micrometers to nanometers, utilising the quantum properties of nitrogen-vacancy (NV) centers in diamond. Scientists successfully measured both strong and weak interactions between proteins, specifically streptavidin and bovine serum albumin, with biotin complexes, establishing a sensitive platform for studying these fundamental biological processes. The technique employs paramagnetic metal spins as labels and leverages the unique sensitivity of NV centers to detect changes in their environment. A key achievement lies in the refinement of relaxation rate evaluation for ensemble NV center measurements, resulting in up to a 4. 5-fold increase in sensitivity. While ensemble measurements are limited by the diffraction limit, single NV centers achieved nanoscale resolution, approaching the detection of individual molecules and revealing intrinsic variations in molecular behavior. Future work will focus on optimising NV center selection, utilising shallower centers to improve signal sensitivity, and developing high-throughput pillar arrays to enhance detection capabilities. The researchers also highlight the potential for a recyclable surface modification strategy, using a PEI nanogel layer, combined with microfluidics, to enable in situ cleaning and re-functionalisation of the diamond surface. 👉 More information 🗞 Quantum relaxometry for detecting biomolecular interactions with single NV centers 🧠 ArXiv: https://arxiv.org/abs/2512.10269 Tags: