Cholestatic liver diseases (CLD) lead to bile accumulation, hepatobiliary dysfunction, and progressive liver damage. Early, accurate evaluation of cholestasis is essential for improving prognosis. In this study, we developed a cross-scale, noninvasive optical imaging platform designed to evaluate both microstructure and metabolic functions in cases of intrahepatic cholestasis, such as primary biliary cholangitis, as well as extrahepatic cholestasis resulting from bile duct ligation. We employed high-resolution photoacoustic microscopy to assess changes in bile duct permeability, hepatic lobular architecture, and blood oxygen saturation following varying degrees of bile duct injury. Meanwhile, we utilized near-infrared-II fluorescence imaging to track the transport of indocyanine green, thereby mapping the absorption and excretion dynamics throughout the liver. Liver function reserve was monitored in situ using contrast-enhanced photoacoustic computed tomography. The imaging manifestations of microstructural alterations and functional impairments associated with cholestasis were quantitatively characterized, demonstrating a correlation with disease progression and validation of our findings. This platform enables dynamic, high-resolution assessment of small bile duct injury and hepatobiliary dysfunction, offering a promising tool for early diagnosis, monitoring, and therapeutic evaluation of CLD.

Wearable sweat sensors that enable non-invasive sampling, efficient and rapid detection, and real-time monitoring capabilities have become an integral and critical component of human health management, with the potential to provide meaningful clinical information related to physiologic diseases in the healthcare field. Here, a flexible nanoplasmonic paper-based sensor based on surface-enhanced Raman scattering (SERS) was developed, in which silver nanoparticles were loaded in the cellulose paper to enhance the Raman signals of targets via the generation of SERS “hotspots.” By incorporating the filter paper channel with a natural core absorbing liquid, the multifunctional chip is formed, which integrates the collection, transmission, and detection of trace sweat. This paper-based chip is soft and stretchable, and fits perfectly onto the human skin surface without causing any damage or irritation. Combined with a hand-held Raman spectrometer, quantitative detection of multiple sweat components can be achieved with the limit of detection of 17 and 1 μmol/L for uric acid and glucose, respectively, and the measurable range is 4–7.5 for pH, enabling wearable and in-situ optical sensing for sweat markers under the condition of human physiology and pathology, within only 5 min for uric acid and glucose detection. This wearable biosensor would provide, to our knowledge, a new way for continuously monitoring the health status by collection and analysis of multiple components in human sweat, contributing to point-of-care testing and personalized medicine applications.

The integration of near-infrared genetically encoded reporters (NIR-GERs) with photoacoustic (PA) imaging enables visualizing deep-seated functions of specific cell populations at high resolution, though the imaging depth is primarily constrained by reporters’ PA response intensity. Directed evolution can optimize NIR-GERs’ performance for PA imaging, yet precise quantifying of PA responses in mutant proteins expressed in E. coli colonies across iterative rounds poses challenges to the imaging speed and quantification capabilities of the screening platforms. Here, we present self-calibrated photoacoustic screening (SCAPAS), an imaging-based platform that can detect samples in parallel within 5 s (equivalent to 50 ms per colony), achieving a considerable quantification accuracy of approximately 2.8% and a quantification precision of about 6.47%. SCAPAS incorporates co-expressed reference proteins in sample preparation and employs a ring transducer array with switchable illumination for rapid, wide-field dual-wavelength PA imaging, enabling precisely calculating the PA response using the self-calibration method. Numerical simulations validated the image optimization strategy, quantification process, and noise robustness. Tests with co-expression samples confirmed SCAPAS’s superior screening speed and quantification capabilities. We believe that SCAPAS will facilitate the development of novel NIR-GERs suitable for PA imaging and has the potential to significantly impact the advancement of PA probes and molecular imaging.

Blood flow is essential for maintaining normal physiological functions of the human body. Endoscopic laser speckle contrast imaging (LSCI) can achieve rapid, high-resolution, label-free, and long-term blood flow perfusion velocity monitoring in minimally invasive surgery. However, conventional endoscopic LSCI uses a low-coherence laser illumination scheme, leading to restricted angles of illumination, compromised laser coherence, uneven laser illumination distribution, and low coupling efficiency, all of which degrade the quality of LSCI in the endoscope. In this paper, we propose that conical fiber (CF)-coupled high-coherence laser can be used to achieve large-angle, high-coherence, high-uniformity, and high coupling efficiency laser illumination in the endoscope. Additionally, we establish an effective model for calculating the divergence angle of CFs. Through phantom and animal experiments, we reveal that laser illumination based on CF markedly enhances endoscopic LSCI performance. This technology broadens the imaging field of view, enhances the signal-to-noise ratio, enables more sensitive detection of minute blood flow changes, expands the detectable flow range, and improves signal-to-background ratio of endoscopic LSCI. Our findings suggest that CF-based laser illumination stands as a highly promising advancement in endoscopic LSCI.

Imaging of surface-enhanced Raman scattering (SERS) nanoparticles (NPs) has been intensively studied for cancer detection due to its high sensitivity, unconstrained low signal-to-noise ratios, and multiplexing detection capability. Furthermore, conjugating SERS NPs with various biomarkers is straightforward, resulting in numerous successful studies on cancer detection and diagnosis. However, Raman spectroscopy only provides spectral data from an imaging area without co-registered anatomic context. This is not practical and suitable for clinical applications. Here, we propose a custom-made Raman spectrometer with computer-vision-based positional tracking and monocular depth estimation using deep learning (DL) for the visualization of 2D and 3D SERS NPs imaging, respectively. In addition, the SERS NPs used in this study (hyaluronic acid-conjugated SERS NPs) showed clear tumor targeting capabilities (target CD44 typically overexpressed in tumors) by an ex vivo experiment and immunohistochemistry. The combination of Raman spectroscopy, image processing, and SERS molecular imaging, therefore, offers a robust and feasible potential for clinical applications.

Photodynamic therapy (PDT) is an innovative approach that utilizes photochemical reactions for non-invasive disease treatment. Conventional PDT is limited by the low penetration depth of visible light required for activation. Herein, we employed upconversion nanoparticles (UCNPs) to extend the activation wavelength of photosensitizers into the infrared range, enabling a treatment depth of over 10 mm. Furthermore, we also used the abundant amino groups of branched polyethyleneimine (PEI) with spatial structure to enhance the loading capacity of protoporphyrin (PPIX), and we ultimately improved skin tumor clearance rates. Moreover, we achieved tumor-specific treatment by utilizing folic acid (FA) targeting and active enrichment of PPIX. According to cellular experimental results, we demonstrated the remarkable reactive oxygen species generation capability of the material and ultra-low dark toxicity. Additionally, we investigated the apoptosis mechanism and demonstrated that the synthesized nanoparticle stimulates the up-regulation of apoptosis-associated proteins Bax/Bcl-2 and Cyto c. During in vivo experiments involving intravenous injection in mouse tails, we investigated the anticancer efficacy of the nanoparticle, confirming its excellent PDT effects. This research provides a promising avenue for future non-invasive treatment of deep-seated tumors, offering a method for the treatment and management of specific cancers.

Just-in-time burn severity assessment plays a vital role in burn treatment and care. However, it is still difficult to quantitatively and promptly evaluate burn severity by existing medical imaging methods via initial burn depth measurement since burn wounds are usually dynamically developed. As an elastic skeleton of skin, the degree of conformational changes of collagen fibers caused by overheating can reflect the burn severity in a timelier manner. Herein, the polarized photoacoustic technique (PPAT) for just-in-time quantitative evaluation of burn severity via collagen fiber anisotropy assessment is proposed. First, phantom experiments demonstrate the ability of PPAT for deep imaging in a transport mean free path and accurately quantify changes in microstructural order by thermal damage. Then, the Pearson correlation coefficient of the PPAT in assessing burn severity is shown to be up to 0.95, validated by burn skin samples. The PPAT provides a just-in-time quantitative strategy for burn severity evaluation.

We introduce two-beam phase correlation spectroscopy (2B-ΦCS) as a label-free technique to measure the dynamics of flowing particles; e.g., in vitro or in vivo blood flow. 2B-ΦCS combines phase imaging with correlation spectroscopy, using the intrinsic refractive index contrast of particles against the fluid background in correlation analysis. This method starts with the acquisition of a time series of phase images of flowing particles using partially coherent point-diffraction digital holographic microscopy. Then, phase fluctuations from two selected circular regions in the image series are correlated to determine the concentration and flow velocity of the particles by fitting pair correlation curves with a physical model. 2B-ΦCS is a facile procedure when using a microfluidic channel, as shown by the measurements on flowing yeast microparticles, polymethyl methacrylate microparticles, and diluted rat blood. In the latter experiment, the concentration and average diameter of rat blood cells were determined to be (4.7±1.9)×106 μL-1 and 4.6±0.4 μm, respectively. We further analyzed the flow of mainly red blood cells in the tail vessels of live zebrafish embryos. Arterial and venous flow velocities were measured as 290±110 μm s-1 and 120±50 μm s-1, respectively. We envision that our technique will find applications in imaging transparent organisms and other areas of the life sciences and biomedicine.

Two-photon optogenetics has become an indispensable technology in neuroscience, due to its capability in precise and specific manipulation of neural activities. A scanless holographic approach is generally adopted to meet the requirement of stimulating neural ensembles simultaneously. However, the commonly used disk patterns fail in achieving single-neuron resolution, especially in axial dimension, and their inherent speckles decrease stimulation efficiency. Here, we propose a novel speckle-free, beaded-ring pattern for high-axial-resolution optical stimulation of neurons in vivo. Using a dye pool and a fluorescent thin film as samples, we verify that, compared to those with disk patterns, higher axial resolution and better localization ability can be achieved with beaded-ring patterns. Furthermore, we perform two-photon based all-optical physiology with neurons in mouse S1 cortex in vivo, and demonstrate that the axial resolution obtained by beaded-ring patterns can be improved by 24% when stimulating multiple neurons, compared to that of disk patterns.

Cancer is one of the most common diseases to threaten human health. If individuals are diagnosed with malignant tumors via a single cell, medical workers are greatly advantageous to early diagnose and intervene in malignant tumors therapy. In this paper, we propose a fluorescence detection map to rapidly distinguish whether the chromosomes of a cell are normal or abnormal by detecting the fluorescent intensity of a single cell. Herein, we draw a map from a single cell with an abnormal number of chromosomes that is monitored in real time. Moreover, this way offers precise and prompt detection of the surviving of cancer cells at or near the site of the tumor after treatments for cancer, which can achieve personalized cancer diagnosis and therapy. Therefore, cancer recurrences and metastasis can be effectively identified, utilizing this ultrasensitive detection method of an abnormal chromosome number.

Opto-conveyors have attracted widespread interest in various fields because of their non-invasive and non-contact delivery of micro/nanoparticles. However, the flexible control of the delivery distance and the dynamic steering of the delivery direction, although very desirable in all-optical manipulation, have not yet been achieved by opto-conveyors. Here, using a simple and cost-effective scheme of an elliptically focused laser beam obliquely irradiated on a substrate, a direction-steerable and distance-controllable opto-conveyor for the targeting delivery of microparticles is implemented. Theoretically, in the proposed scheme of the opto-conveyor, the transverse and longitudinal resultant forces of the optical gradient force and the optical scattering force result in the transverse confinement and the longitudinal transportation of microparticles, respectively. In this study, it is experimentally shown that the proposed opto-conveyor is capable of realizing the targeting delivery for microparticles. Additionally, the delivery distance of microparticles can be flexibly and precisely controlled by simply adjusting the irradiation time. By simply rotating the cylindrical lens, the proposed opto-conveyor is capable of steering the delivery direction flexibly within a large range of azimuthal angles, from ?75° to 75°. This study also successfully demonstrated the real-time dynamic steering of the delivery direction from ?45° to 45° with the dynamical rotation of the cylindrical lens. Owing to its simplicity, flexibility, and controllability, the proposed method is capable of creating new opportunities in bioassays as well as in drug delivery.

Scattering is a huge challenge for microscopic imaging. Indeed, it is difficult to observe target chemicals in scattering media by means of the current Gaussian beam-based stimulated Raman scattering (SRS) microscopy, since the tight focus of the Gaussian beam is destroyed after propagating through a certain distance. Bessel beams, featuring self-reconstructing property, may bring a solution to this problem. By combining Bessel beams with SRS microscopy, we can probe the SRS signal from a scattering medium. In this paper, using the beam propagation method, we first simulate the propagation of the Bessel beam as well as the generation and self-reconstruction of SRS signals. By adding glass beads along the beam propagation path in order to simulate scattering, the propagation of the Bessel beams and the generation of the SRS signals will change. Then, we design a series of simulations to investigate the influence of the size, position, number, and distribution of the added glass beads on the generation of the SRS signals. A preliminary experiment is also carried out to confirm the simulation predictions. Results demonstrate that the SRS signals can be generated or be recovered at a certain depth in scattering media, and that such signals are greatly affected by the parameters of the scatters.

Whispering gallery mode (WGM) microtoroid optical resonators have been effectively used to sense low concentrations of biomolecules down to the single molecule limit. Optical WGM biochemical sensors such as the microtoroid operate by tracking changes in resonant frequency as particles enter the evanescent near field of the resonator. Previously, gold nanoparticles have been coupled to WGM resonators to increase the magnitude of resonance shifts via plasmonic enhancement of the electric field. However, this approach results in increased scattering from the WGM, which degrades its quality (Q) factor, making it less sensitive to extremely small frequency shifts caused by small molecules or protein conformational changes. Here, we show using simulation that precisely positioned trimer gold nanostructures generate dark modes that suppress radiation loss and can achieve high (>106) Q with an electric-field intensity enhancement of 4300, which far exceeds that of a single rod (～2500 times). Through an overall evaluation of a combined enhancement factor, which includes the Q factor of the system, the sensitivity of the trimer system was improved 105× versus 84× for a single rod. Further simulations demonstrate that unlike a single rod system, the trimer is robust to orientation changes and has increased capture area. We also conduct stability tests to show that small positioning errors do not greatly impact the result.

The optical memory effect is an interesting phenomenon that has attracted considerable attention in recent decades. Here, we present a new physical picture of the optical memory effect, in which the memory effect and the conventional spatial shift invariance are united. Based on this picture we depict the role of thickness, scattering times, and anisotropy factor and derive equations to calculate the ranges of the angular memory effect (AME) of different scattering components (ballistic light, singly scattered, doubly scattered, etc.), and hence a more accurate equation for the real AME ranges of volumetric turbid media. A conventional random phase mask model is modified according to the new picture. The self-consistency of the simulation model and its agreement with the experiment demonstrate the rationality of the model and the physical picture, which provide powerful tools for more sophisticated studies of the memory-effect-related phenomena and wavefront-sensitive techniques, such as wavefront shaping, optical phase conjugation, and optical trapping in/through scattering media.

The denaturation of double-stranded deoxyribonucleic acid (ds-DNA) has been well known to break nucleobase bonds, resulting in single-stranded deoxyribonucleic acid (ss-DNA) in solutions, which can recombine to form ds-DNA in a reversible manner. We developed an efficient process to irreversibly maintain various DNA denaturation levels in thin solid films in order to investigate the impacts of the denaturation on the optical properties of DNA films. By adding NaOH in an aqueous solution of salmon testis DNA, we flexibly controlled the level of denaturation in the solution, which was then spin-coated on Si and silica substrates to irreversibly bind ss-DNAs in a thin solid film. The denaturation of DNA in thin solid films was experimentally confirmed by ultraviolet-visible and Fourier transform infrared spectroscopic investigations, whose level could be controlled by the NaOH content in the aqueous solution precursor. By this irreversible denaturation process, we developed a new method to flexibly vary the refractive index of DNA thin solid films in a wide range of Δn>0.02 in the visible to near-infrared range. Thermo-optic coefficients dn/dT of the films were also experimentally measured in the temperature range from 40°C to 90°C to confirm the significant impacts of denaturation. Detailed thin film processes and optical characterizations are discussed.

Stimulated emission depletion (STED) microscopy is one of far-field optical microscopy techniques that can provide sub-diffraction spatial resolution. The spatial resolution of the STED microscopy is determined by the specially engineered beam profile of the depletion beam and its power. However, the beam profile of the depletion beam may be distorted due to aberrations of optical systems and inhomogeneity of a specimen’s optical properties, resulting in a compromised spatial resolution. The situation gets deteriorated when thick samples are imaged. In the worst case, the severe distortion of the depletion beam profile may cause complete loss of the super-resolution effect no matter how much depletion power is applied to specimens. Previously several adaptive optics approaches have been explored to compensate aberrations of systems and specimens. However, it is difficult to correct the complicated high-order optical aberrations of specimens. In this report, we demonstrate that the complicated distorted wavefront from a thick phantom sample can be measured by using the coherent optical adaptive technique. The full correction can effectively maintain and improve spatial resolution in imaging thick samples.