Explore the vast range of titles available.

Measuring certain quantities at the nanoscale is often limited to strict conditions such as low temperature or vacuum. However, the recently developed nanodiamond (ND) quantum sensing technology shows great promise for ultrasensitive diagnosis and probing subcellular parameters at ambient conditions. Atom defects (i.e., N, Si) within the ND lattice provide stable emissions and sometimes spin‐dependent photoluminescence. These unique properties endow ND quantum sensors with the capacity to detect local temperature, magnetic fields, electric fields, or strain. In this review, some of the recent, most exciting developments in the preparation and application of ND sensors to solve current challenges in biology and medicine including ultrasensitive detection of virions and local sensing of pH, radical species, magnetic fields, temperature, and rotational movements, are discussed. The recently developed nanodiamond (ND) quantum sensing technology shows great promise for ultrasensitive diagnosis and probing subcellular parameters within living cells at ambient conditions. In this review, some of the recent, most exciting developments of this technology, its potential, and challenges for solving current issues in biology and medicine are critically discussed.

We report on wide-field optically detected magnetic resonance imaging of nitrogen-vacancy centers (NVs) in type IIa polycrystalline diamond. These studies reveal a heterogeneous crystalline environment that produces a varied density of NV centers, including preferential orientation within some individual crystal grains, but preserves long spin coherence times. Using the native NVs as nanoscale sensors, we introduce a three-dimensional strain imaging technique with high sensitivity ( < 10 − 5 Hz-1/2) and diffraction-limited resolution across a wide field of view.

Temperature is one of the most relevant parameters for the regulation of intracellular processes. Measuring localized subcellular temperature gradients is fundamental for a deeper understanding of cell function, such as the genesis of action potentials, and cell metabolism. Notwithstanding several proposed techniques, at the moment detection of temperature fluctuations at the subcellular level still represents an ongoing challenge. Here, for the first time, temperature variations (1 °C) associated with potentiation and inhibition of neuronal firing is detected, by exploiting a nanoscale thermometer based on optically detected magnetic resonance in nanodiamonds. The results demonstrate that nitrogen‐vacancy centers in nanodiamonds provide a tool for assessing various levels of neuronal spiking activity, since they are suitable for monitoring different temperature variations, respectively, associated with the spontaneous firing of hippocampal neurons, the disinhibition of GABAergic transmission and the silencing of the network. Conjugated with the high sensitivity of this technique (in perspective sensitive to < 0.1 °C variations), nanodiamonds pave the way to a systematic study of the generation of localized temperature gradients under physiological and pathological conditions. Furthermore, they prompt further studies explaining in detail the physiological mechanism originating this effect. Measuring subcellular temperature gradients is fundamental for a deeper understanding of cell function. Here, for the first time, by exploiting a nanoscale thermometer based on optically detected magnetic resonance in nanodiamonds, 1 K temperature variations, associated with neuronal firing potentiation/silencing, are detected. This result in perspective will provide a tool for assessing neuronal spiking activity under physiological and pathological conditions.

Fluorescent nanodiamonds (FNDs) are promising tools to image cells, bioanalytes and physical quantities such as temperature, pressure, and electric or magnetic fields with nanometer resolution. To exploit their potential for intracellular applications, the FNDs have to be brought into contact with cell culture media. The interactions between the medium and the diamonds crucially influence sensitivity as well as the ability to enter cells. The authors demonstrate that certain proteins and salts spontaneously adhere to the FNDs and may cause aggregation. This is a first investigation on the fundamental questions on how (a) FNDs interact with the medium, and (b) which proteins and salts are being attracted. A differentiation between strongly binding and weakly binding proteins is made. Not all proteins participate in the formation of FND aggregates. Surprisingly, some main components in the medium seem to play no role in aggregation. Simple strategies to prevent aggregation are discussed. These include adding the proteins, which are naturally present in the cell culture to the diamonds first and then inserting them in the full medium. Graphical abstract Schematic of the interaction of nanodiamonds with cell culture medium. Certain proteins and salts adhere to the diamond surface and lead to aggregation or to formation of a protein corona.

The effective medium theory (EMT) provides a simplified framework to calculate the electromagnetic responses and is generally considered exact in the all-dielectric system with deep-subwavelength constituents. In this work, we perform the Goos–Hänchen (GH) shift that invalidates the EMT on the multilayered dielectric structures under the common conditions. This breakdown of the EMT arises from the high sensitivity of the GH shift on the phase and magnitude of Fresnel reflection coefficient. The degree of such breakdown shows strong dependence on the polarization angle of incidence and the layer and filling fraction of the structures. Notably, we find that the GH shift is potentially applicable to nano-meter scale thickness sensing, which cannot be displayed based on EMT in some cases. Our findings will provide useful guidance to reduce the calculation errors of the electromagnetic responses and promote the design of precise metrology devices.

Bio-membranes exhibit complex but unique mechanical properties as communicative regulators in various physiological and pathological processes. Exposed to a dynamic micro-environment, bio-membranes can be seen as an intricate and delicate system. The systematical modeling and detection of their local physical properties are often difficult to achieve, both quantitatively and precisely. The recent emerging diamonds hosting quantum defects (i.e., nitrogen-vacancy (NV) center) demonstrate intriguing optical and spin properties, together with their outstanding photostability and biocompatibility, rendering them ideal candidates for biological applications. Notably, the extraordinary spin-based sensing enable the measurements of localized nanoscale physical quantities such as magnetic fields, electrical fields, temperature, and strain. These nanoscale signals can be optically read out precisely by simple optical microscopy systems. Given these exclusive properties, NV-center-based quantum sensors can be widely applied in exploring bio-membrane-related features and the communicative chemical reaction processes. This review mainly focuses on NV-based quantum sensing in bio-membrane fields. The attempts of applying NV-based quantum sensors in bio-membranes to investigate diverse physical and chemical events such as membrane elasticity, phase change, nanoscale bio-physical signals, and free radical formation are fully overviewed. We also discuss the challenges and future directions of this novel technology to be utilized in bio-membranes.

Biophotonics has advanced through many discoveries, yet challenges remain, including label-free biomolecular specificity, quantitative imaging, and single-molecule detection. Progress is further constrained by the need for cheaper, lighter, miniaturized materials that still meet strict optical, electrical, and mechanical specifications. This limitation can be overcome if bioinspired structures are developed. One of the developed areas in which solutions in nature are used is micro and nanostructures including nanosurfaces. It offers a way to increase biomolecular specificity and develop lightweight, low-cost devices for biomedicine. However, it requires measuring phenomena in materials and testing these materials in applications, e.g., sensing systems. We offer a concise, authoritative overview of biophotonics-from nanoscale light-biomolecule interactions to bioinspired materials, phantoms, test methods, and sensor development. A coherent and comprehensive analysis of the crucial problems related to the development of bioinspired materials and devices was carried out. Recent advances in light scattering by biological surfaces enable structure characterization, disease diagnosis, red-blood-cell analysis, drug discovery, and optical imaging and sensing. Structural and genetic bases of biological photonic surfaces were examined, alongside key performance factors in bio-inspired materials-biocompatibility, biodegradability, structure-optics coupling (e.g., dynamic color change), and scalability limits. We survey chiral nanomaterials, silica frustules, and artificial surfaces that emulate peacock feathers, butterfly wings, iridescent fruits, plant petals, and beetle cuticles, highlighting complementary diagnostics-omics, hyperspectral, and terahertz imaging-for structural analysis and material innovation. We examine bio-inspired phantoms for medical calibration, recent advances in Monte Carlo tissue light-transport modeling, and the resulting applications of these materials and diagnostic tools. Results confirm a broad set of tunable bio-inspired materials: key optical phenomena were mapped, structures fabricated and modeled, phantoms validated, and strong sensor potential demonstrated. We survey emerging biophotonics, review material and system requirements, and emphasize simplifying and miniaturizing sensors for biomedical use.

Medical examination of human tissue is preferably performed by imaging the tissue surface. Optical imaging techniques are limited by low penetration depth due to high tissue scattering, whereas sensing techniques can detect changes deeper inside the tissue. Near-infrared sensing methods such as oximetry and fNIRS are already used clinically but have not yet been applied in endoscopy. We investigate the existence of iso-pathlength (IPL) points in endoscopic geometry, with the goal of extending the concept of IPL points from cylindrical and half-infinite geometries into hollow cylindrical tissue relevant to endoscopy. In addition, we demonstrate the ability to extract the absorption properties of a tissue at this structure by the IPL and demonstrate it by experiment. The IPL point is a unique position in the full scattering profile, independent of tissue scattering and dependent only on the tissue absorption and geometry. We studied two directions in cylindrical endoscopic geometry: azimuthal and longitudinal. First, diffusion theory with extrapolated zero-boundary conditions was applied to predict IPL positions. These predictions were then tested using Monte Carlo simulations of photon distribution and validated experimentally using phantoms with cylindrical air holes measured by endoscopy. Finally, using the experimentally identified IPL point and applying the same procedure to a standard phantom, a hemoglobin-agar phantom, and chicken breast tissue, we were able to estimate the absorption coefficient of the chicken tissue. Both azimuthal and longitudinal IPL points were identified. The experimental azimuthal IPL point was found at an angle of , whereas the longitudinal IPL point appeared at a distance of from the laser spot center. These findings confirm the theoretical and simulation predictions. Moreover, from the experiment of a chicken breast, the IPL point enables us to calculate the absorption coefficient and get , within the range of . The demonstration of IPL points in endoscopic geometry provides a new framework for depth-resolved optical sensing in hollow cylindrical tissues. This approach may enable self-calibrated absorption measurements and open the way for improved diagnostic tools in the digestive system, esophagus, and other hollow organs where conventional endoscopy lacks depth information.

The editorial provides an overview of the JBO Special Section Nanoscale Imaging, Sensing, and Actuation and reflects on the future of nanoscale biophotonics.The editorial provides an overview of the JBO Special Section Nanoscale Imaging, Sensing, and Actuation and reflects on the future of nanoscale biophotonics.

Fluorescent nanodiamonds (NDs) are carbon‐based nanoparticles with various outstanding magneto−optical properties. After preparation, NDs have a variety of different surface groups that determine their physicochemical properties. For biological applications, surface modifications are crucial to impart a new interface for controlled interactions with biomolecules or cells. Herein, a straightforward synthesis concept denoted “adsorption−crosslinking” is applied for the efficient modification of NDs, which sequentially combines fast noncovalent adsorption based on electrostatic interactions and subsequent covalent crosslinking. As a result, a very thin and uniform nanogel (NG) coating surrounding the NDs is obtained, which imparts reactive groups as well as high colloidal stability. The impact of the reaction time, monomer concentration, molecular weight, structure of the crosslinker on the resulting NG shell, the availability of reactive chemical surface functions, and the quantum sensing properties of the coated NDs are assessed and optimized. Postmodification of the NG‐coated NDs is achieved with phototoxic ruthenium complexes yielding ND‐based probes suitable for photodynamic applications. The adsorption−crosslinking ND functionalization reported herein provides new avenues toward functional probes and traceable nanocarriers for high‐resolution bioimaging, nanoscale sensing, and photodynamic applications. A straightforward synthesis concept called “adsorption−crosslinking” is applied for the modification of ND surfaces, which sequentially combines noncovalent adsorption and subsequent covalent crosslinking. As a result, a thin and uniform nanogel coating surrounding the NDs is obtained, which imparts high colloidal stability and is used for ion and metal protein sensing. After postfunctionalization, it is used for photodynamic therapy.