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Abstract Visualizing rapid biological dynamics like neuronal signaling and microvascular flow is crucial yet challenging due to photon noise and motion artifacts. Here we present a deep learning framework for enhancing the spatiotemporal relations of optical microscopy data. Our approach leverages correlations of mirrored perspectives from conjugated scan paths, training a model to suppress noise and motion blur by restoring degraded spatial features. Quantitative validation on vibrational calcium imaging validates significant gains in spatiotemporal correlation (2.2×), signal-to-noise ratio (9–12 dB), structural similarity (6.6×), and motion tolerance compared to raw data. We further apply the framework to diverse in vivo experiments from mouse cerebral hemodynamics to zebrafish cardiac dynamics. This approach enables the clear visualization of the rapid nutrient flow (30 mm/s) in microcirculation and the systolic and diastolic processes of heartbeat (2.7 cycle/s), as well as cellular and vascular structure in deep cortex. Unlike techniques relying on temporal correlations, learning inherent spatial priors avoids motion-induced artifacts. This self-supervised strategy flexibly enhances live microscopy under photon-limited and motion-prone regimes.

Abstract Visualization of axons and dendritic spines is crucial in neuroscience research. However, traditional microscopy is limited by diffraction-limited resolution and shallow imaging depth, making it difficult to study neuronal dynamics. Two-photon multifocal structured illumination microscopy (2P-MSIM) provides super-resolution imaging along with a reasonably good penetration, but it is vulnerable to optical aberrations in deep tissues. Herein we present a novel non-inertial scanning 2P-MSIM system incorporated with adaptive optics (AO) which allows for super-resolution imaging with effective aberration correction. Our strategy is designed to correct both laser and fluorescence paths simultaneously using a spatial light modulator and a deformable mirror respectively, providing better results than the individual path corrections. The successful implementation of adaptive optical two-photon multifocal structured illumination microscopy (AO 2P-MSIM) has allowed for the super-resolution imaging of neuronal structures in a mouse brain slice at great depths and dynamic morphological characteristics of zebrafish motoneurons in vivo.

Abstract Optothermal nanotweezers have emerged as an innovative optical manipulation technique in the past decade, which revolutionized classical optical manipulation by efficiently capturing a broader range of nanoparticles. However, the optothermal temperature field was merely employed for in-situ manipulation of nanoparticles, its potential for identifying bio-nanoparticles remains largely untapped. Hence, based on the synergistic effect of optothermal manipulation and CRIPSR-based bio-detection, we developed CRISPR-powered optothermal nanotweezers (CRONT). Specifically, by harnessing diffusiophoresis and thermo-osmotic flows near the substrate upon optothermal excitation, we successfully trapped and enriched DNA functionalized gold nanoparticles, CRISPR-associated proteins, as well as DNA strands. Remarkably, we built an optothermal scheme for enhancing CRISPR-based single-nucleotide polymorphism (SNP) detection at single molecule level, while also introducing a novel CRISPR methodology for observing nucleotide cleavage. Therefore, this innovative approach has endowed optical tweezers with DNA identification ability in aqueous solution which was unattainable before. With its high specificity and feasibility for in-situ bio-nanoparticle manipulation and identification, CRONT will become a universal tool in point-of-care diagnosis, biophotonics, and bio-nanotechnology.

Abstract Cancer remains a global health challenge, demanding early detection and accurate diagnosis for improved patient outcomes. An intelligent paradigm is introduced that elevates label‐free nonlinear optical imaging with contrastive patch‐wise learning, yielding stain‐free nonlinear optical computational histology (NOCH). NOCH enables swift, precise diagnostic analysis of fresh tissues, reducing patient anxiety and healthcare costs. Nonlinear modalities are evaluated, including stimulated Raman scattering and multiphoton imaging, for their ability to enhance tumor microenvironment sensitivity, pathological analysis, and cancer examination. Quantitative analysis confirmed that NOCH images accurately reproduce nuclear morphometric features across different cancer stages. Key diagnostic features, such as nuclear morphology, size, and nuclear‐cytoplasmic contrast, are well preserved. NOCH models also demonstrate promising generalization when applied to other pathological tissues. The study unites label‐free nonlinear optical imaging with histopathology using contrastive learning to establish stain‐free computational histology. NOCH provides a rapid, non‐invasive, and precise approach to surgical pathology, holding immense potential for revolutionizing cancer diagnosis and surgical interventions.

Fractional‐order vector vortex beams (VVBs) have recently been demonstrated as new carriers of fractional‐strength optical vortices. However, the inherent mechanism of the new vortex beams, formed by the combination of both unstable states, to propagate stably in free space requires clarification. In this study, this scientific problem is solved by revealing the physical essence of propagable fractional‐strength optical vortices in free space. Therefore, three new viewpoints regarding these unique vortex beams are proposed: Abbe's diffraction limit, the phase evolution of the vortex beam, and the binary time vector property of phase. First, due to Abbe's diffraction limit, the inherent polarization modes are intertwined, thereby maintaining the entire unique vortex beam in free space. In the second case, the phase evolution of the vortex beam is the physical cause for the polarization rotation of fractional‐order VVBs. Third, the phase is not merely a scalar attribute of the light beam and demonstrates a binary time vector property. This study provides entirely different physical viewpoints on the phase of the vortex beam and Abbe's diffraction limit, which may deepen the knowledge on the behavior of light beams in classical optics.

Abstract Super-resolution optical imaging is crucial to the study of cellular processes. Current super-resolution fluorescence microscopy is restricted by the need of special fluorophores or sophisticated optical systems, or long acquisition and computational times. In this work, we present a deep-learning-based super-resolution technique of confocal microscopy. We devise a two-channel attention network (TCAN), which takes advantage of both spatial representations and frequency contents to learn a more precise mapping from low-resolution images to high-resolution ones. This scheme is robust against changes in the pixel size and the imaging setup, enabling the optimal model to generalize to different fluorescence microscopy modalities unseen in the training set. Our algorithm is validated on diverse biological structures and dual-color confocal images of actin-microtubules, improving the resolution from ~ 230 nm to ~ 110 nm. Last but not least, we demonstrate live-cell super-resolution imaging by revealing the detailed structures and dynamic instability of microtubules.

Abstract Fast and precise reconstruction algorithm is desired for for multifocal structured illumination microscopy (MSIM) to obtain the super‐resolution image. This work proposes a deep convolutional neural network (CNN) to learn a direct mapping from raw MSIM images to super‐resolution image, which takes advantage of the computational advances of deep learning to accelerate the reconstruction. The method is validated on diverse biological structures and in vivo imaging of zebrafish at a depth of 100 µm. The results show that high‐quality, super‐resolution images can be reconstructed in one‐third of the runtime consumed by conventional MSIM method, without compromising spatial resolution. Last but not least, a fourfold reduction in the number of raw images required for reconstruction is achieved by using the same network architecture, yet with different training data.

Structured illumination microscopy (SIM) is suitable for biological samples because of its relatively low-peak illumination intensity requirement and high imaging speed. The system resolution is affected by two typical detection modes: Point detection and area detection. However, a systematic analysis of the imaging performance of the different detection modes of the system has rarely been conducted. In this study, we compared laser point scanning point detection (PS-PD) and point scanning area detection (PS-AD) imaging in nonconfocal microscopy through theoretical analysis and simulated imaging. The results revealed that the imaging resolutions of PS-PD and PS-AD depend on excitation and emission point spread functions (PSFs), respectively. Especially, we combined the second harmonic generation (SHG) of point detection (P-SHG) and area detection (A-SHG) with SIM to realize a nonlinear SIM-imaging technique that improves the imaging resolution. Moreover, we analytically and experimentally compared the nonlinear SIM performance of P-SHG with that of A-SHG.

Optical tweezers system has emerged as an efficient tool to manipulate tiny particles in a non-invasive way. Trapping stiffness, as an essential parameter of an optical potential well, represents the trapping stability. Additionally, trapping inorganic nanoparticles such as metallic nanoparticles or other functionalized inorganic nanoparticles is important due to their properties of good stability, high conductivity, tolerable toxicity, etc., which makes it an ideal detection strategy for bio-sensing, force calculation, and determination of particle and environmental properties. However, the trapping stiffness measurement (TSM) methods of inorganic nanoparticles have rarely been analyzed and summarized. Here, in this review, the principle and methods of TSM are analyzed. We also systematically summarize the progress in acquiring inorganic particles trapping stiffness and its promising applications. In addition, we provide prospects of the energy and environment applications of optical tweezering technique and TSM. Finally, the challenges and future directions of achieving the nanoparticles trapping stiffness are discussed.

Fourier light-field microscopy (FLFM) uses a microlens array (MLA) to segment the Fourier plane of the microscopic objective lens to generate multiple two-dimensional perspective views, thereby reconstructing the three-dimensional (3D) structure of the sample using 3D deconvolution calculation without scanning. However, the resolution of FLFM is still limited by diffraction, and furthermore, it is dependent on the aperture division. In order to improve its resolution, a super-resolution optical fluctuation Fourier light-field microscopy (SOFFLFM) was proposed here, in which the super-resolution optical fluctuation imaging (SOFI) with the ability of super-resolution was introduced into FLFM. SOFFLFM uses higher-order cumulants statistical analysis on an image sequence collected by FLFM, and then carries out 3D deconvolution calculation to reconstruct the 3D structure of the sample. The theoretical basis of SOFFLFM on improving resolution was explained and then verified with the simulations. Simulation results demonstrated that SOFFLFM improved the lateral and axial resolution by more than [Formula: see text] and 2 times in the second- and fourth-order accumulations, compared with that of FLFM.

The algorithm used for reconstruction or resolution enhancement is one of the factors affecting the quality of super-resolution images obtained by fluorescence microscopy. Deep-learning-based algorithms have achieved state-of-the-art performance in super-resolution fluorescence microscopy and are becoming increasingly attractive. We firstly introduce commonly-used deep learning models, and then review the latest applications in terms of the network architectures, the training data and the loss functions. Additionally, we discuss the challenges and limits when using deep learning to analyze the fluorescence microscopic data, and suggest ways to improve the reliability and robustness of deep learning applications.

Fiber-optic biosensors have garnered significant attention and witnessed rapid development in recent years owing to their remarkable attributes such as high sensitivity, immunity to electromagnetic interference, and real-time monitoring. They have emerged as a potential tool in the realm of biomarker detection for low-concentration and small molecules. In this paper, a portable and cost-effective optical fiber biosensor based on surface plasmon resonance for the early detection of breast cancer is demonstrated. By utilizing the aptamer human epidermal growth factor receptor 2 (HER2) as a specific biomarker for breast cancer, the presence of the HER2 protein can be detected through an antigen-antibody binding technique. The detection method was accomplished by modifying a layer of HER2 aptamer on the flat surface of a gold-coated D-shaped polymer optical fiber (core/cladding diameter 120/490 μm), of which the residual thickness after side-polishing was about 245 μm, the thickness of the coated gold layer was 50 nm, and the initial wavelength in pure water was around 1200 nm. For low-concentration detection of the HER2 protein, the device exhibited a wavelength shift of ~1.37 nm with a concentration of 1 μg/mL (e.g., 5.5 nM), which corresponded to a limit of detection of ~5.28 nM. Notably, the response time of the biosensor was measured to be as fast as 5 s. The proposed biosensor exhibits the potential for early detection of HER2 protein in initial cancer serum and offers a pathway to early prevention of breast cancer.

Abstract Background Low-intensity light can decelerate neurodegenerative disease progression and reduce amyloid β (Aβ) levels in the cortex, though the cellular and molecular mechanisms by which photobiomodulation (PBM) protects against neurodegeneration are still in the early stages. Microglia cells play a key role in the pathology of Alzheimer’s disease by causing chronic inflammation. We present new results concerning the PBM of both oxidative stress and microglia metabolism associated with the activation of metabolic processes by 808 nm near-infrared light. Methods The studies were carried out using healthy male mice to obtain the microglial cell suspension from the hippocampus. Oligomeric β-amyloid (1-42) was prepared and used to treat microglia cells. Light irradiation of cells was performed using diode lasers emitting at 808 nm (30 mW/cm2 for 5 min, resulting in a dose of 10 J/cm2). Mitochondrial membrane potential, ROS level studies, cell viability, apoptosis, and necrosis assays were performed using epifluorescence microscopy. Phagocytosis, nitric oxide and H2O2 production, arginase, and glucose 6-phosphate dehydrogenase activities were measured using standard assays. Cytokines, glucose, lactate, and ATP were measurements with ELISA. As our data were normally distributed, two-way ANOVA test was used. Results The light induces a metabolic shift from glycolysis to mitochondrial activity in pro-inflammatory microglia affected by oligomeric Aβ. Thereby, the level of anti-inflammatory microglia increases. This process is accompanied by a decrease in pro-inflammatory cytokines and an activation of phagocytosis. Light exposure decreases the Aβ-induced activity of glucose-6-phosphate dehydrogenase, an enzyme that regulates the rate of the pentose phosphate pathway, which activates nicotinamide adenine dinucleotide phosphate oxidases to further produce ROS. During co-cultivation of neurons with microglia, light prevents the death of neurons, which is caused by ROS produced by Aβ-altered microglia. Conclusions These original data clarify reasons for how PBM protects against neurodegeneration and support the use of light for therapeutic research in the treatment of Alzheimer’s disease. Graphical Abstract

Abstract Flexible organic materials that exhibit dynamic ultralong room temperature phosphorescence (DURTP) via photoactivation have attracted increasing research interest for their fascinating functions of reversibly writing-reading-erasing graphic information in the form of a long afterglow. However, due to the existence of a nonnegligible activation threshold for the initial exposure dose, the display mode of these materials has thus far been limited to binary patterns. By resorting to halogen element doping of carbon dots (CDs) to enhance intersystem crossing and reduce the activation threshold, we were able to produce, for the first time, a transparent, flexible, and fully programmable DURTP composite film with a reliable grayscale display capacity. Examples of promising applications in UV photography and highly confidential steganography were constructed, partially demonstrating the broad future applications of this material as a programmable platform with a high optical information density.

Light beams with optical vortices can propagate in free space only with integer orbital angular momentum. Herein, this scientific consensus theoretically and experimentally is upheaved by proposing light beams carrying natural noninteger orbital angular momentum. These peculiar vortex beams are unique solutions to the Helmholtz equation, which possesses optical vortices with topological charges of l + 0.5, where l is an integer. During propagation in free space, their amplitudes and vortex phases with noninteger topological charges can be maintained stably. The findings of this study provide an alternative state of optical vortices in physics, which can serve as basis for innovations in optics and related scientific fields.

A self-alignment attention-guided residual-in-residual dense generative adversarial networks architecture closes the gap between speed, field of view, and image quality of label-free nonlinear optical microscopes which are notoriously slow.

The properties of mesoporous nanomaterials have been exploited for several applications, including drug delivery and NIR-II photoacoustic imaging. Here, the authors design monodispersed semimetallic mesoporous antimony nanospheres with photothermal conversion efficiency in the second near-infrared range and drug loading capacity, showing their potential for cancer photothermal/chemo therapy.

Rheumatoid arthritis (RA) and osteoarthritis (OA) have a significant impact on the quality of life of patients around the world, causing significant pain and disability. Furthermore, the drugs used to treat these conditions frequently have side effects that add to the patient’s burden. Photobiomodulation (PBM) has emerged as a promising treatment approach in recent years. PBM effectively reduces inflammation by utilizing near-infrared light emitted by lasers or LEDs. In contrast to photothermal effects, PBM causes a photobiological response in cells, which regulates their functional response to light and reduces inflammation. PBM’s anti-inflammatory properties and beneficial effects in arthritis treatment have been reported in numerous studies, including animal experiments and clinical trials. PBM’s effectiveness in arthritis treatment has been extensively researched in arthritis-specific cells. Despite the positive results of PBM treatment, questions about specific parameters such as wavelength, dose, power density, irradiation time, and treatment site remain. The goal of this comprehensive review is to systematically summarize the mechanisms of PBM in arthritis treatment, the development of animal arthritis models, and the anti-inflammatory and joint function recovery effects seen in these models. The review also goes over the evaluation methods used in clinical trials. Overall, this review provides valuable insights for researchers investigating PBM treatment for arthritis, providing important references for parameters, model techniques, and evaluation methods in future studies.

Abstract Optical imaging is a most useful and widespread technique for the investigation of the structure and function of the cellular genomes. However, an analysis of immensely convoluted and irregularly compacted DNA polymer is highly challenging even by modern super-resolution microscopy approaches. Here we propose fluorescence lifetime imaging (FLIM) for the advancement of studies of genomic structure including DNA compaction, replication as well as monitoring of gene expression. The proposed FLIM assay employs two independent mechanisms for DNA compaction sensing. One mechanism relies on the inverse quadratic relation between the fluorescence lifetimes of fluorescence probes incorporated into DNA and their local refractive index, variable due to DNA compaction density. Another mechanism is based on the Förster resonance energy transfer (FRET) process between the donor and the acceptor fluorophores, both incorporated into DNA. Both these proposed mechanisms were validated in cultured cells. The obtained data unravel a significant difference in compaction of the gene-rich and gene-poor pools of genomic DNA. We show that the gene-rich DNA is loosely compacted compared to the dense DNA domains devoid of active genes.

This special issue collects 20 excellent papers, spanning NIR II imaging, high-speed imaging, adaptive wavefront shaping, label-free imaging, ultrasensitive detection, polarization optics, photodynamic therapy, and preclinical applications.

Vector polarization induced by a change in the scalar phase is far beyond our understanding of the relationship between polarization and phase in classical optics due to the entanglement of the inherent polarized modes of light beams. To overcome this limitation, we establish this miraculous relationship by the principle of phase vectorization, which can transform three particular phases into linear, circular and elliptical polarizations. A polarized-spatial light modulator based on the principle of phase vectorization can be achieved using a phase-only spatial light modulator, which not only enables pixel-level polarization manipulation of light beams in a real-time dynamic way but also simultaneously retains complete phase control. This work demonstrates the phase-to-polarization link and reports the creation of a polarized-spatial light modulator, which will transform our view of the natural properties of light beams and pave the way for the era of vector optics.

Abstract Background Acute kidney injury (AKI) with high mortality rates is associated with an excess of reactive oxygen/nitrogen species (RONS) within kidney tissues. Recently, nanomedicine antioxidant therapy has been used to alleviate AKI. Herein, we synthesized ultrasmall Prussian blue nanozymes (PB NZs, 4.5 nm) as theranostic agents for magnetic resonance (MR)/photoacoustic (PA) dual-modal imaging guided AKI treatment. Results PB NZs exhibited multi-enzyme mimetic abilities, promoting the effective elimination of RONS both in vitro and in vivo. Moreover, benefiting from their imaging contrast properties, the rapid renal accumulation of PB NZs was verified by in vivo PA/MR dual-modal imaging. Due to their excellent enrichment in the kidney and unique multi-enzyme mimetic abilities, ultrasmall PB NZs displayed superior AKI treatment efficacy compared with that of amifostine in two clinically relevant types of AKI induced murine models (either by rhabdomyolysis or cisplatin). Conclusion Our findings suggested ultrasmall PB NZs, as nanozyme theranostics, have great potential for AKI management. Graphic abstract

Volumetric imaging of a mouse brain in vivo with one-photon and two-photon ultralong anti-diffracting (UAD) beam illumination was performed. The three-dimensional (3D) structure of blood vessels in the mouse brain were mapped to a two-dimensional (2D) image. The speed of volumetric imaging was significantly improved due to the long focal length of the UAD beam. Comparing one-photon and two-photon UAD beam volumetric imaging, we found that the imaging depth of two-photon volumetric imaging (80 μm) is better than that of one-photon volumetric imaging (60 μm), and the signal-to-background ratio (SBR) of two-photon volumetric imaging is two times that of one-photon volumetric imaging. Therefore, we used two-photon UAD volumetric imaging to perform dynamic volumetric imaging of mouse brain blood vessels in vivo, and obtained the blood flow velocity.

ReS2, as a new member of transition metal dichalcogenides (TMDCs), has emerged as a promising substrate for semiconductor surface-enhanced Raman spectroscopy (SERS) due to its unique optoelectronic properties. Nevertheless, the sensitivity of the ReS2 SERS substrate poses a significant challenge to its widespread application in trace detection. In this work, we present a reliable approach for constructing a novel ReS2/AuNPs SERS composite substrate, enabling ultrasensitive detection of trace amounts of organic pesticides. We demonstrate that the porous structures of ReS2 nanoflowers can effectively confine the growth of AuNPs. By precisely controlling the size and distribution of AuNPs, numerous efficient and densely packed “hot spots” were created on the surface of ReS2 nanoflowers. As a result of the synergistic enhancement of the chemical and electromagnetic mechanisms, the ReS2/AuNPs SERS substrate demonstrates high sensitivity, good reproducibility, and superior stability in detecting typical organic dyes such as rhodamine 6G and crystalline violet. The ReS2/AuNPs SERS substrate shows an ultralow detection limit of 10−10 M and a linear detection of organic pesticide molecules within 10−6–10−10 M, which is significantly lower than the EU Environmental Protection Agency regulation standards. The strategy of constructing ReS2/AuNPs composites would contribute to the development of highly sensitive and reliable SERS sensing platforms for food safety monitoring.

Quantitative phase imaging (QPI) can acquire dynamic data from living cells without the need for physical contact. We presented a real-time and stable dynamic imaging system for recording complex fields of transparent samples by using Fourier transform based on off-axis interferometry. We calculated and removed the system phase without sample to obtain the real phase of the sample, so as to ensure that the system has the ability to accurately measure the phase. The temporal and spatial phase sensitivity of the system was evaluated. Benefit from the ability to record the dynamic phase and phase profile of a specimen, a standard sample (polystyrene microspheres) is investigated to demonstrate the efficiency of this imaging system and we have observed the variation of erythrocyte membrane during Red Blood Cells (RBCs) spontaneous hemolysis with different mediums. Experimental results indicate that the phase of non-anticoagulant RBC changed apparently than anticoagulant RBC and the system could be applied to real-time noninvasive and label-free identification of living cells.

Apoptosis is very important for the maintenance of cellular homeostasis and is closely related to the occurrence and treatment of many diseases. Mitochondria in cells play a crucial role in programmed cell death and redox processes. Nicotinamide adenine dinucleotide (NAD(P)H) is the primary producer of energy in mitochondria, changing NAD(P)H can directly reflect the physiological state of mitochondria. Therefore, NAD(P)H can be used to evaluate metabolic response. In this paper, we propose a noninvasive detection method that uses two-photon fluorescence lifetime imaging microscopy (TP-FLIM) to characterize apoptosis by observing the binding kinetics of cellular endogenous NAD(P)H. The result shows that the average fluorescence lifetime of NAD(P)H and the fluorescence lifetime of protein-bound NAD(P)H will be affected by the changing pH, serum content, and oxygen concentration in the cell culture environment, and by the treatment with reagents such as H2O2 and paclitaxel. Taxol (PTX). This noninvasive detection method realized the dynamic detection of cellular endogenous substances and the assessment of apoptosis.

Abstract Background The aim to develop a highly stable near-infrared (NIR) photoinduced tumor therapy agent stems from its considerable potential for biological application. Due to its long wavelength, biological imaging exhibits a high signal-to-background ratio, deep tissue penetration and maximum permissible light power, which can minimize damage to an organism during photoinduced tumor therapy. Results A class of stable NIR-II fluorophores (NIR998, NIR1028, NIR980, NIR1030, and NIR1028-S) based on aza–boron–dipyrromethene (aza-BODIPY) dyes with donor–acceptor-donor structures have been rationally designed and synthesized by harnessing the steric relaxation effect and intramolecular photoinduced electron transfer (IPET). These fluorophores exhibit an intense range of NIR-II emission, large Stokes shift (≥ 100 nm), excellent photothermal conversion performance, and superior stability against photobleaching. Among the NIR-II fluorophores, NIR998 possesses better NIR-II emission and photothermal conversion performance. NIR998 nanoparticles (NIR998 NPs) can be encapsulated by liposomes. NIR998 NPs show superior stability in the presence of light, heat, and reactive oxygen nitrogen species than that of indocyanine green NPs, as well as a higher photothermal conversion ability (η = 50.5%) compared to other photothermal agents. Finally, under the guidance of photothermal imaging, NIR998 NPs have been proven to effectively eliminate tumors via their excellent photothermal conversion performance while presenting negligible cytotoxicity. Conclusions Utilizing IPET and the steric relaxation effect can effectively induce NIR-II emission of aza-BODIPY dyes. Stable NIR998 NPs have excellent photothermal conversion performance and negligible dark cytotoxicity, so they have the potential to act as photothermal agents in biological applications.

Surface plasmon resonance microscopy (SPRM) has been widely employed in biological fields because of its high spatial resolution and label-free detection modality. In this study, SPRM based on total internal reflection (TIR) is studied via a home-built SPRM system, and the principle of imaging of a single nanoparticle is analyzed as well. By designing a ring filter and combining it with the deconvolution algorithm in Fourier space, the parabolic tail of the nanoparticle image is removed, in which a spatial resolution of 248 nm is obtained. In addition, we also measured the specific binding between the human IgG antigen and goat anti-human IgG antibody using the TIR-based SPRM. The experimental results have proved that the system can image sparse nanoparticles and monitor biomolecular interactions.

Optical fibers are typically used in telecommunications services for data transmission, where the use of fiber tags is essential to distinguish between the different transmission fibers or channels and thus ensure the working functionality of the communication system. Traditional physical entity marking methods for fiber labeling are bulky, easily confused, and, most importantly, the label information can be accessed easily by all potential users. This work proposes an encrypted optical fiber tag based on an encoded fiber Bragg grating (FBG) array that is fabricated using a point-by-point femtosecond laser pulse chain inscription method. Gratings with different resonant wavelengths and reflectivities are realized by adjusting the grating period and the refractive index modulations. It is demonstrated that a binary data sequence carried by a fiber tag can be inscribed into the fiber core in the form of an FBG array, and the tag data can be encrypted through appropriate design of the spatial distributions of the FBGs with various reflection wavelengths and reflectivities. The proposed fiber tag technology can be used for applications in port identification, encrypted data storage, and transmission in fiber networks.

Abstract. Luminescence (mostly fluorescence and phosphorescence) probes are a powerful tool widely used in the life sciences research. They can be used, for example, in the quantitative analysis of physiological parameters, visualization of different cell organelles, and measurement of drug transportation. The luminescence intensity and lifetime of these probes are among the main signals recorded and evaluated in these applications. Other reviews have discussed optical probes from the perspective of their luminescence intensity. However, the luminescence lifetime, which depends on the molecular microenvironment but not the probe concentration, is another promising metric for biological sensing and imaging applications. In this review, we aim to introduce the basic strategies of FLIM probe design. We also present applications of these probes, including sensing of intracellular pH, cation/anion concentrations, oxygen levels, biomolecule contents, and physiological parameters, as well as live-cell imaging based on luminescence lifetime. Studies based on FLIM imaging of cells or tissues with endogenous organic molecules are not included in this mini review. With the rapid development of microscopy technology for fluorescence lifetime imaging, fluorescence lifetime-based probes have shown great potential in a variety of biological applications.

Abstract Label‐free nonlinear optical imaging (NLOI) has made tremendous inroads toward unscrambling the microcosmic complexity of cancers. However, harmonic and Raman microscopy offers throughput without redox information to reveal metabolic differentiation, and fluorescence lifetime microscopy lacks the vibrational response of molecules to visualize specific molecular constituents such as lipid. Here, a flexible, robust simultaneous multi‐nonlinear imaging and cross‐modality system that combines complementary imaging contrast mechanisms is demonstrated. This system, utilizing multiplexed ultrashort pulses, ingeniously integrates typical nonlinear processes, and high‐dimension lifetime extension in a single setup to enhance the imaging dimensions and quality. Using this system, the authors perform label‐free comprehensive evaluation of clinicopathological tissues of ovarian carcinoma due to its statistical complexity. The results show that the technology provides statistically rich, insightful information with high accuracy, sensitivity, and specificity, in contrast to standard histopathology, and can potentially be a powerful tool for fundamental cancer research and clinical applications.

Live cell imaging of mitochondrial cristae is challenged by the unsuitability of current fluorescent probes and high phototoxicity. Here the authors develop a squarine variant probe (MitoESq-635) that is capable of longitudinal imaging of cristae with STED with minimal phototoxicity.

Intensity interrogation surface plasmon resonance (ISPR) sensing has a simple schematic design and is the most widely used surface plasmon resonance technology at present. However, it has relatively low sensitivity, especially for ISPR imaging (ISPRi). In this paper, a new technique for the real-time monitoring of biomolecule binding on sensor surfaces via ISPRi detection is described. The technique is based on the interrogation of the differential value of two intensities at two specific wavelengths from the reflected light spectrum. In addition, we also optimized the selection of dual-wavelength parameters under different circumstances to achieve the highest sensitivity. The new technique achieved a refractive index resolution (RIR) of 2.24 × 10–6 RIU, which is far beyond that of traditional ISPRi technique. Moreover, our new ISPRi technique also realized the real-time detection of high-throughput biomolecular binding. This study is expected to promote the development of faster and more accurate SPRi technologies.

Abstract Inorganic nanomaterials with intrinsic singlet oxygen (1O2) generation capacity, are emerged yet dynamically developing materials as nano‐photosensitizers (NPSs) for photodynamic therapy (PDT). Compared to previously reported nanomaterials that have been used as either carriers to load organic PSs or energy donors to excite the attached organic PSs through a Foster resonance energy transfer process, these NPSs possess intrinsic 1O2 generation capacity with extremely high 1O2 quantum yield (e.g., 1.56, 1.3, 1.26, and 1.09) than any classical organic PS reported to date, and thus are facilitating to make a revolution in PDT. In this review, the recent advances in the development of various inorganic nanomaterials as NPSs, including metal‐based (gold, silver, and tungsten), metal oxide‐based (titanium dioxide, tungsten oxide, and bismuth oxyhalide), metal sulfide‐based (copper and molybdenum sulfide), carbon‐based (graphene, fullerene, and graphitic carbon nitride), phosphorus‐based, and others (hybrids and MXenes‐based NPSs) are summarized, with an emphasis on the design principle and 1O2 generation mechanism, and the photodynamic therapeutic performance against different types of cancers. Finally, the current challenges and an outlook of future research are also discussed. This review may provide a comprehensive account capable of explaining recent progress as well as future research of this emerging paradigm.

Surface plasmon resonance microscopy (SPRM) is a versatile technique for biosensing and imaging that facilitates high-sensitivity, label-free, real-time characterization. To date, SPR technology has been successfully commercialized and its performance has continued to improve. However, this method is inhibited by low spatial resolution and the inability to achieve single-molecule detection. In this report, we present an overview of SPRM research progress in the field of plasma imaging and sensing. A brief review of the technological advances in SPRM is outlined, as well as research progress in important applications. The combination of various new techniques with SPRM is emphasized. Finally, the current challenges and outlook of this technique are discussed.

Nanomechanical resonators made from suspended graphene combine the properties of ultracompactness and ultrahigh detection sensitivity, making them interesting devices for sensing applications. However, nanomechanical systems can be affected by membrane stress. The present work developed an optomechanical resonator for thermal stress sensing. The proposed resonator consists of a section of hollow core fiber (HCF) and a trampoline graphene–Au membrane. An all-optical system that integrated optical excitation and optical detection was applied. Then, the resonance frequency of the resonator was obtained through this all-optical system. In addition, this system and the resonator were used to detect the membrane’s built-in stress, which depended on the ambient temperature, by monitoring the resonance frequency shift. The results verified that the temperature-induced thermal effect had a significant impact on membrane stress. Temperature sensitivities of 2.2646 kHz/°C and 2.3212 kHz/°C were obtained when the temperature rose and fell, respectively. As such, we believe that this device will be beneficial for the quality monitoring of graphene mechanical resonators.

Long-term, repeatable monitoring of the appearance and progress of Alzheimer’s disease (AD) in real time can be extremely beneficial to acquire highly reliable diagnostic insights, which is crucial for devising apt strategies towards effective AD treatment. Herein, we present an optimized innovative cranial window imaging method for the long-term repeatable imaging of amyloid-β (Aβ) plaques and vessels in an AD mouse model. Basically, two-photon excitation fluorescence (TPEF) microscopy was used to monitor the fluorescently labeled Aβ plaques, whereas the label-free blood vessels were studied using coherent anti-Stokes Raman scattering (CARS) microscopy in the live in vivo AD mouse model. It was possible to clearly observe the Aβ deposition and vascular structure in the target cortex localization for 31 weeks in the AD mouse model using this method. The combined TPEF/CARS imaging studies were also instrumental in realizing the relationship between the tendency of Aβ deposition and ageing. Essentially, the progression of cerebral amyloid angiopathy (CAA) in the AD mouse model was quantitatively characterized, which revealed that the proportion Aβ deposition in the unit vessel can increase from 13.63% to 28.80% upon increasing the age of mice from 8 months old to 14 months old. The proposed imaging method provided an efficient, safe, repeatable platform with simple target localization aptitude towards monitoring the brain tissues, which is an integral part of studying any brain-related physiological or disease conditions to extract crucial structural and functional information.

Structured illumination microscopy (SIM) is an essential super-resolution microscopy technique that enhances resolution. Several images are required to reconstruct a super-resolution image. However, linear SIM resolution enhancement can only increase the spatial resolution of microscopy by a factor of two at most because the frequency of the structured illumination pattern is limited by the cutoff frequency of the excitation point spread function. The frequency of the pattern generated by the nonlinear response in samples is not limited; therefore, nonlinear SIM (NL-SIM), in theory, has no inherent limit to the resolution. In the present study, we describe a two-photon nonlinear SIM (2P-SIM) technique using a multiple harmonics scanning pattern that employs a composite structured illumination pattern, which can produce a higher order harmonic pattern based on the fluorescence nonlinear response in a 2P process. The theoretical models of super-resolution imaging were established through our simulation, which describes the working mechanism of the multi-frequency structure of the nonsinusoidal function to improve the resolution. The simulation results predict that a 5-fold improvement in resolution in the 2P-SIM is possible.

Over the past two decades, super-resolution microscopy (SRM), which offered a significant improvement in resolution over conventional light microscopy, has become a powerful tool to visualize biological activities in both fixed and living cells. However, completely understanding biological processes requires studying cells in a physiological context at high spatiotemporal resolution. Recently, SRM has showcased its ability to observe the detailed structures and dynamics in living species. Here we summarized recent technical advancements in SRM that have been successfully applied to in vivo imaging. Then, improvements in the labeling strategies are discussed together with the spectroscopic and chemical demands of the fluorophores. Finally, we broadly reviewed the current applications for super-resolution techniques in living species and highlighted some inherent challenges faced in this emerging field. We hope that this review could serve as an ideal reference for researchers as well as beginners in the relevant field of in vivo super resolution imaging.

Skin cancer, a common type of cancer, is generally divided into basal cell carcinoma (BCC), squamous cell carcinoma (SCC) and malignant melanoma (MM). The incidence of skin cancer has continued to increase worldwide in recent years. Early detection can greatly reduce its morbidity and mortality. Hyperspectral microscopic imaging (HMI) technology can be used as a powerful tool for skin cancer diagnosis by reflecting the changes in the physical structure and microenvironment of the sample through the differences in the HMI data cube. Based on spectral data, this work studied the staging identification of SCC and the influence of the selected region of interest (ROI) on the staging results. In the SCC staging identification process, the optimal result corresponded to the standard normal variate transformation (SNV) for spectra preprocessing, the partial least squares (PLS) for dimensionality reduction, the hold-out method for dataset partition and the random forest (RF) model for staging identification, with the highest staging accuracy of 0.952 ± 0.014, and a kappa value of 0.928 ± 0.022. By comparing the staging results based on spectral characteristics from the nuclear compartments and peripheral regions, the spectral data of the nuclear compartments were found to contribute more to the accurate staging of SCC.

High-quality fluorescent probes based on carbon dots (CDs) have promising applications in many fields owing to their good stability, low toxicity, high quantum yield, and low raw material price. The fluorine- and nitrogen-doped fluorescent CDs (NFCDs) with blue fluorescence was successfully synthesized using 3-aminophenol and 2,4-difluorobenzoic acid as the raw material by the hydrothermal method. The NFCDs as probe can be used to directly and indirectly detect Fe3+ (detection range: 0.1–150 μM and detection limit: 0.14 μM) and ascorbic acid (AA) (detection range: 10–80 μM and detection limit: 0.11 μM). The NFCDs-based probe shows exceptional selectivity and strong anti-interference for Fe3+ and ascorbic acid (AA). In addition, we examined the response of NFCDs to Fe3+ and AA in living cells, which showed that the timely use of AA can reduce the effects of iron poisoning. This has important biological significance. This means that using NFCDs as fluorescent probes is beneficial for Fe3+ and AA detection and observing their dynamic changes in living cells. Thus, this work may contribute to the study of Fe3+- and AA-related diseases.

Copper ions (Cu2+) and sulfur ions (S2−) are important elements widely used in industry. However, these ions have the risk of polluting the water environment. Therefore, rapid and quantitative detection methods for Cu2+ and S2− are urgently required. Using 2,4-difluorobenzoic acid and L-lysine as precursors, nitrogen and fluorine co-doped dots (N, F-CDs) were synthesized in this study via a hydrothermal method. The aqueous N, F-CDs showed excellent stability, exhibited satisfactory selectivity and excellent anti-interference ability for Cu2+ detection. The N, F-CDs, based on the redox reactions for selective and quantitative detection of Cu2+, showed a wide linear range (0–200 μM) with a detection limit (215 nM). By forming the N, F-CDs@Cu2+ sensing platform and based on the high affinity of S2− to Cu2+, the N, F-CDs@Cu2+ can specifically detect S2− over a linear range of 0–200 μM with a detection limit of 347 nM. In addition, these fluorescent probes achieved good results when used for Cu2+ and S2− detection in environmental water samples, implying the good potential for applications.

The resolution of optical microscopes is limited by the optical diffraction limit; in particular, the axial resolution is much lower than the lateral resolution, which hinders the clear distinction of the three-dimensional (3D) structure of cells. Although stimulated emission depletion (STED) superresolution microscopy can break through the optical diffraction limit to achieve 3D superresolution imaging, traditional 3D STED requires high depletion laser power to acquire high-resolution images, which can cause irreversible light damage to biological samples and probes. Therefore, we developed an ultralow laser power 3D STED superresolution imaging method. On the basis of this method, we obtained lateral and axial resolutions of 71 nm and 144 nm, respectively, in fixed cells with 0.65 mW depletion laser power. This method will have broad application prospects in 3D superresolution imaging of living cells.

The strong nonlinear optical behavior of low-dimensional materials, such as quantum dots and core-shell quantum dots, has been a topic of intense research in recent years. As quantum dots have tunable emission via changes in their sizes, they are potentially useful in photo-electronics, photovoltaic nonlinear optics, light-emitting diode fabrication, and laser protections. Variation among core and shell shape and size, along with the chemical composition of quantum dots, define their enhanced nonlinear optical properties. Some specific nonlinear optical properties, such as nonlinear refraction, optical limiting, saturable absorption, reverse saturable absorption of CdTe and CdSe quantum dots (QDs), as well as core-shell QDs and their applications, were assessed in this paper.

First reported in 1994, stimulated emission depletion (STED) microscopy has long been regarded as a powerful tool for real-time superresolved bioimaging . However, high STED light power (101∼3 MW/cm2) is often required to achieve significant resolution improvement, which inevitably introduces phototoxicity and severe photobleaching, damaging the imaging quality, especially for long-term cases. Recently, the employment of nanoprobes (quantum dots, upconversion nanoparticles, carbon dots, polymer dots, AIE dots, etc.) in STED imaging has brought opportunities to overcoming such long-existing issues. These nanomaterials designed for STED imaging show not only lower STED power requirements but also more efficient photoluminescence (PL) and enhanced photostability than organic molecular probes. Herein, we review the recent progress in the development of nanoprobes for STED imaging, to highlight their potential in improving the long-term imaging quality of STED microscopy and broadening its application scope. We also discuss the pros and cons for specific classes of nanoprobes for STED bioimaging in detail to provide practical references for biological researchers seeking suitable imaging kits, promoting the development of relative research field.

Rare-earth doped nanoparticles (RENPs) have been widely used for anti-counterfeiting and security applications due to their light frequency conversion features: they are excited at one wavelength, and they display spectrally narrow and distinguished luminescence peaks either at shorter wavelengths (i.e., frequency/energy upconversion) or at longer wavelengths (frequency/energy downconversion). RENPs with a downconversion (DC) photoluminescence (PL) in short-wave infrared (SWIR) spectral range (~1,000–1,700 nm) have recently been introduced to anti-counterfeiting applications, allowing for multilevel protection based on PL imaging through opaque layers, due to a lesser scattering of SWIR PL emission. However, as the number and spectral positions of the discrete PL bands exhibited by rare-earth ions are well-known, it is feasible to replicate luminescence spectra from RENPs, which results in a limited anti-counterfeiting security. Alternatively, lifetime of PL from RENPs can be used for encoding, as it can be finely tuned in broad temporal range (i.e., from microseconds to milliseconds) by varying type of dopants and their content in RENPs, along with the nanoparticle morphology and size. Nevertheless, the current approach to decoding and imaging the RENP luminescence lifetimes requires multiple steps and is highly time-consuming, precluding practical applications of PL lifetime encoding for anti-counterfeiting. Herein, we report the use of a rapid lifetime determination (RLD) technique to overcome this issue and introduce real-time imaging of SWIR PL lifetime for anti-counterfeiting applications. NaYF4:20% Yb, x% Er (x = 0, 2, 20, 80)@NaYF4 core@shell RENPs were synthesized and characterized, revealing DC PL in SWIR region, with maximum at ~1,530 nm and PL lifetimes ranging from 3.2 to 6 ms. Imaging of the nanoparticles with different lifetimes was performed by the developed time-gated imaging system engaging RLD method and the precise manipulation of the delay between the excitation pulses and camera gating windows. Moreover, it is shown that imaging and decrypting can be performed at a high rate (3–4 fps) in a cyclic manner, thus allowing for real-time temporal decoding. We believe that the demonstrated RLD-based fast PL lifetime imaging approach can be employed in other applications of photoluminescent RENPs.