Biomedical optics express最新文献

We report laser wave-mixing spectroscopy as a highly sensitive and rapid absorption-based detection method for pancreatic and breast cancer biomarkers and viruses on surface-mounted micrometer-thin samples. Currently, cancer diagnosis is done mostly by imaging techniques such as magnetic resonance imaging (MRI) and computed tomography (CT), which typically are effective for detecting tumors only at later stages. Similarly, early viral detection, such as HIV, is challenged by the diagnostic window period. These limitations underscore the urgent need for more sensitive, rapid, and minimally invasive biomarker-based diagnostic tools. Our laser wave-mixing detection method offers significant advantages over existing techniques, including ultrasensitive detection, excellent chemical specificity, and high spatial resolution achieved through the use of small probe volumes (nL) and micrometer-thin samples that can be mounted on microscope slides and microarrays that can be reproducibly moved and controlled by piezo actuators. We achieved detection sensitivity for the pancreatic cancer biomarker CA 19-9 at micro-unit levels, and for HIV-1 p24 and HER-2 at zeptomole levels. Laser wave-mixing detection method provides excellent detection limits and high spatial resolution compared to traditional methods, making it an effective microchip-based detector for point-of-care diagnostics.

Post-ischemic microvascular perfusion abnormalities appear in OCTA as regional hypoperfusion and heterogeneous attenuation within pre-existing vascular structures. However, most longitudinal OCTA analyses rely on image- or region-level readouts, making it difficult to assign local signal changes to the same baseline vascular elements or to interpret their spatial and topological context within the original vascular network. Here, we propose a baseline-referenced longitudinal OCTA framework in which vascular topological primitives (VTPs) serve as fixed structural coordinates for post-ischemic perfusion analysis. The pre-ischemic OCTA vascular network was decomposed into a baseline VTP template with explicit topological boundaries, fixed sampling domains, and graph connectivity, allowing follow-up signals to be read from the same vascular elements throughout the longitudinal sequence. In a photothrombotic mouse model of focal cerebral ischemia, this mapping generated VTP-level log-ratio attenuation trajectories and a continuous vascular risk field. VTP-level trajectories revealed heterogeneous attenuation magnitude and temporal evolution across baseline vascular structures. The resulting risk field delineated a core-centered spatial-topological organization, with core-proximal attenuation-risk VTPs located closer to OCTA-defined high-risk core VTPs than stable-background VTPs and risk scores decreasing outward along the baseline VTP graph. This spatial-topological organization was directionally consistent across six animals and was significant by one-sided exact sign test (p = 0.016). Using early-window VTP attenuation and graph-neighborhood features, later OCTA-derived core-proximal attenuation-risk states were identified with a leave-one-animal-out AUC of 0.929, supported by label-permutation testing. These results establish the pre-ischemic vascular network as a structural coordinate system for longitudinal OCTA analysis and support VTP-level mapping, spatial-topological characterization, and early identification of post-ischemic microvascular risk evolution.

Infrared neural stimulation (INS) is a promising neuromodulation tool, yet its clinical translation is hindered by an incomplete understanding of how photothermal dynamics recruit specific physiological mechanisms. This study investigates how varying spatiotemporal thermal gradients influence calcium responses in primary rat cortical neurons by combining calcium imaging with numerical modeling and experimental validation. Laser dosimetry was performed by focusing a 1470 nm laser to a 15 µm diameter and varying the pulse energy for 0.5 ms, 5 ms, and 50 ms laser pulse durations. The thermal dynamics of the stimulus were simulated using a computational model, which was validated against thermal lensing experiments. Our results reveal a bimodal calcium response comprising high-frequency phasic spiking and low-frequency basal increases, which depend on the temporal thermal dynamics of the laser stimulus. This research provides a critical framework for designing spatially precise, effective, and safe INS technologies.

We present analytical equations for time-resolved signals in diffuse optics and their sensitivity factors in homogeneous media, derived from perturbation-based equations valid for infinitesimal changes and then extended to finite changes in optical properties. Time-resolved optical measurements are becoming increasingly available due to technological advancements, expanding their use in various techniques such as near-infrared spectroscopy (NIRS). These measurements acquire distributions of times of flight (DTOF) of photons, and the measurands considered in this study are attenuation (A), mean time of flight (m ₁), and variance (V) of the DTOF. Established methods for recovering changes in the absorption coefficient (Δμ _a) from ΔA, Δm ₁, or ΔV use perturbation-based sensitivity factors, which are valid for infinitesimal changes. We derived sensitivity factor equations that relate ΔA, Δm ₁, and ΔV to finite (including large) changes in absorption (Δμ _a), reduced scattering coefficient $\left(\Delta {\mu }_s^{\text{'}}\right)$ , and source-detector distance (Δr). The derivations rely on solutions of the diffusion equation (DE) for homogeneous infinite (IM) and semi-infinite (SM) media within the diffusion approximation $({\mu }_s^{\text{'}}\gg {\mu }_a)$ , without introducing additional assumptions. We also present analytical equations for the modified Beer-Lambert law (MBLL) that are valid for finite Δμ _a in IM and SM, which can be directly applied in continuous-wave NIRS data analysis. Sensitivity factors and the MBLL require knowledge of the baseline optical properties and the differential pathlength factor (DPF), and we assessed how errors in these parameters affect the recovered Δμ _a. We also assessed cross-talk, in which scattering changes $\Delta {\mu }_s^{\text{'}}$ lead to spuriously recovered absorption changes Δμ _a, and vice versa. The proposed framework can be used to improve the accuracy of methods for estimating changes in optical properties.

As final products of the Maillard reaction, the formation of advanced glycation end products (AGEs) is associated with pathological complications of diabetes mellitus (DM) and aging. Since some AGEs are fluorescent, fluorescent advanced glycation end products (fAGEs) have been used as biomarkers for characterizing the degree of tissue glycation. While many studies focus on using 370 nm as the excitation source and 440 nm as the detection wavelength for fAGE, there is an advantage to consider other spectral ranges, especially for in vivo detection, where longer wavelengths allow detection at greater depths. In this study, we attempt to obtain a full spectral characterization of fAGEs in the visible range by using artificially glycated human blood samples of serum albumin, hemoglobin, and erythrocytes, from the treatment of ribose, fructose, galactose, and glucose. For the case of D-ribose, we found that monosaccharide-treated sample solutions have a broad absorption spectrum spanning from 420 nm to 680 nm. Moreover, by varying the excitation wavelengths of 373, 405, 473, 532, and 644 nm, we found the fAGE spectral range to be in the 380-700 nm range, with the peaks of fluorescence emission changing as a function of excitation wavelength. This observation suggests the existence of multiple-fAGE species. Detailed spectral analysis suggests that there are multiple fAGE species in the above spectral range. Our results suggest that, due to reduced scattering, longer wavelengths should be used in developing clinical diagnostic tools for fAGEs in tissues.

Multicolor fluorescence imaging enables simultaneous visualization of multiple cellular components through specific labeling. However, an increase in the number of fluorophores leads to severe spectral overlap, necessitating spectral unmixing to eliminate crosstalk between channels. Because reference spectra are difficult to accurately acquire and multicolor mixed images inherently contain noise, the difficulty of spectral unmixing is substantially increased. Here, we propose a deep unfolding blind source unmixing method, termed DuBsUnmix. The optimization problem is first decomposed via non-negative matrix factorization into sub-problems for the spectral matrix and the abundance matrix. These two sub-problems are then alternately unrolled into a deep unfolding network, where projected gradient descent is employed for the spectral learning module, and proximal gradient descent combined with residual network components is used for the abundance learning module. By this design, DuBsUnmix effectively overcomes the challenges of spectral distortion and image noise in spectral unmixing. The method achieves superior unmixing performance across various simulated scenarios. In experiments on real samples, including eight-color fluorescent beads, seven-color mouse brain sections, and six-color live-cell dynamic imaging, DuBsUnmix demonstrates high accuracy, robust performance, and strong morphological generalization capability. This work provides an accurate and robust solution for blind source unmixing in multicolor fluorescence imaging, offering significant value for biomedical research.

Beam engineering effectively overcomes the resolution-depth of focus trade-off in high-NA optical coherence microscopy (OCM). Conventional OCM is limited by this constraint, hindering stable volumetric acquisition. To overcome this, we present an intrinsically registered imaging platform based on Bessel beam-enabled extended-depth-of-focus OCM for quantitative, label-free volumetric phenotyping of three-dimensional cell models. Annular illumination extends the focal range to 193 µm, enabling stable scattering contrast in dense spheroids. By exploiting structural scattering signatures associated with cellular disintegration, we demonstrate volumetric viability mapping with 94.57 ± 2.69% aggregate viability concordance relative to fluorescence references. The platform differentiates drug-specific responses and captures pathological transitions in spheroids and organoids, establishing a quantitative paradigm for volumetric biological phenotyping.

Here we present an adaptive optics scanning light ophthalmoscope with a square 1.5° full field of view, steerable within a 4° window. When imaging through a 7.72 mm diameter pupil, the instrument provides nominal diffraction-limited performance at the retinal conjugate over a 20 diopter (D) focus range centered at 1D of myopia and supports a 3 D source-detector vergence range for any combination of wavelengths between 450 and 1300 nm. The optical setup also provides nominal diffraction-limited imaging between the pupil conjugates of the wavefront sensor, deformable mirror, and eye, with distortion below 0.5% across the 3 D source-detector vergence range. The optical setup includes four pupil relays. The first three are telescopes formed by pairs of concave spherical mirrors tilted in a non-planar configuration. In these relays, the mirror-to-mirror spacing was held fixed, while the distances to the entrance and exit pupil planes were varied to mitigate aberrations in both pupil and retinal conjugates. The fourth relay comprises four spherical mirrors, two concave and two convex, tilted in a planar configuration. As-built instrument performance is demonstrated by imaging a telecentric model eye over a -6 to +8 D range (limited by deformable mirror stroke) and human photoreceptor mosaic imaging at 680 and 795 nm. The proposed relay forms are broadly applicable to adaptive optics ophthalmoscopes and imaging modalities, including fluorescence, spectroscopy, and optical coherence tomography.

Optical microscopy provides sub-cellular and high-speed imaging to capture neuron dynamics in a living brain, but its penetration depth is limited by tissue scattering. Multiphoton excitation improves the depth to over 1 mm, while combining with a gradient refractive index (GRIN) lens enables centimeter penetration with minimal invasiveness. However, the system performance is compromised due to the intrinsic optical aberrations of GRIN lenses, which severely reduce the contrast, spatial resolution, and effective field of view (FoV). To address this issue, we developed a 3D aberration correction approach for GRIN lenses by combining spiral scanning with cylindrical deconvolution. This method leverages the cylindrical symmetry of GRIN-induced aberrations and incorporates the spatially varying point-spread function (PSF) across the imaging volume. Radially adaptive excitation implemented through spiral scanning expanded the usable FoV diameter by nearly 2-fold and achieved 30- and 10-fold improvement, respectively, in peripheral signal intensity and signal-to-noise ratio (SNR) compared to conventional raster scanning with uniform excitation, while cylindrical deconvolution improved spatial resolution by up to 3.5-fold. We further validated this method through 3D imaging of neuronal structures, demonstrating enhanced effective volume size and a 2-fold improvement in neuronal SNR. These results indicate that the spiral scanning and algorithm-augmented GRIN 2PF system is promising toward resolving structure/functional connectomics in deep brain regions.

Although second near-infrared (NIR-II) photoacoustic (PA) imaging affords deep tissue penetration, developing efficient contrast agents remains challenging due to a lack of suitable optical absorbers. Herein, we report semiconducting polymer nanoparticles (SPNs) for dual-modal PA and NIR fluorescence imaging, featuring a high optical absorption coefficient at 1064 nm that facilitates excitation via high-power Nd:YAG lasers. Phantom evaluations revealed a linear PA signal correlation, with a low detection limit of 0.05 cm^-1. In vivo studies in tumor-bearing mice demonstrated passive SPN accumulation in tumor tissue, successfully visualized by both PA and NIR fluorescence imaging. These results indicate that SPNs are promising contrast agents for dual-modal imaging.