Biomedical optics express最新文献

As dynamic organelles reflecting cellular physiological states, lipid droplets not only provide essential substances for cellular life activities, but also their quantitative analysis is crucial for evaluating drug efficacy. Coherent anti-Stokes Raman scattering (CARS) microscopy, with imaging advantages including label-free, non-invasive, high sensitivity, and submicron resolution, is an ideal tool for drug efficacy assessment. However, traditional CARS microscopy excited by Gaussian beams requires prolonged focusing for 3D tomography, which is time-consuming, causes significant photodamage, and easily alters the cellular microenvironment, affecting the accuracy of quantitative analysis of lipid droplet proportion. We adopted dual Bessel beams to excite CARS signals, increasing the depth of field by 5 times and resolution by 1.17 times, enabling 3D information and volumetric Raman spectra acquisition with a single 2D scan. Detecting HeLa cells treated with gradient concentrations of doxorubicin hydrochloride via spectral phasor segmentation revealed reduced lipid droplet accumulation correlated with drug effect, supporting rapid quantitative visualization of lipid droplets and research on drug-cell interactions.

Off-axis holography enables single-shot phase retrieval but reduces spatial bandwidth, while in-line phase-shifting interferometry preserves bandwidth yet requires reference-path stepping and is sensitive to drift, limiting dynamic measurements. Moreover, viscoelastic mapping is rarely available from the same holographic measurement. We propose vibration-encoded in-line Mach-Zehnder holography for simultaneous thickness and viscoelasticity mapping of soft samples. Twelve holograms acquired over one vibration cycle are analyzed using Bessel-based harmonic inversion and robust regression to recover the static phase, modulation depth, and phase lag, yielding thickness and Kelvin-Voigt storage and loss modulus maps (E', E″). Simulations recover E' and E'' to within ∼2% across a wide E''/E' range and achieve sub-micron thickness error over 20-45 μm beads. Experiments on calibrated polyacrylamide beads show sub-micron thickness repeatability (median ∼0.57 μm over 40 repeats) and stiffness estimates typically within 10% of ground truth, and we further demonstrate the approach on adherent MCF-7 cells.

Recently, it has become widely recognized that culturing cancer cells in vitro in small, 3D aggregates known as tumor spheroids provides a more physiologically relevant model of in vivo tumor behavior compared to 2D monolayer cultures. Dynamic optical coherence tomography (dOCT) is a non-invasive imaging modality that, by analyzing temporal fluctuations in the light scattered from biological tissue, does not require exogenous contrast agents to visualize and quantify cellular activity within 3D cell cultures. However, recent volumetric dOCT studies have encountered challenges due to low acquisition speeds. In this study, we present morphological and dynamic analyses of prostate tumor spheroid growth over a two-week longitudinal period, utilizing a line-field dOCT platform. Volumetric dOCT data were acquired for each spheroid in 16 seconds. Our method clearly differentiated between active cellular metabolism in live spheroids and the lack of activity in spheroids fixed with formaldehyde. Quantitative validation of the dynamic signal was conducted using the Alamar Blue proliferation assay, while qualitative validation was provided by live/dead fluorescence microscopy.

We present a high-speed, wide-field, fiber-based polarization-sensitive optical coherence tomography (PS-OCT) system that enables reliable in vivo birefringence imaging of tissue beds. To address the inherent instability of the input state of polarization (SOP) in single-input fiber systems, particularly in handheld configurations, we introduce a real-time sample surface Stokes vector feedback mechanism that dynamically stabilizes the incident circular polarization prior to scanning. The system integrates a 600 kHz swept-source laser with a relatively narrow 20 nm bandwidth to balance axial resolution (∼37.8 μm in air) and mitigate polarization mode dispersion (PMD), achieving an extinction ratio exceeding 200. Phantom studies validated the repeatability of the SOP feedback strategy, with a median angular standard deviation of 6.52° across repeated local axis measurements. In vivo imaging of the anterior human oral cavity demonstrated detailed structural and polarization-resolved contrasts across a 42 × 42 mm² field of view, enabling simultaneous assessment of enamel orientation, gingival birefringence, and early-stage tissue abnormalities. This approach enables a streamlined and robust PS-OCT operation, facilitating the clinical translation of wide-field polarization-sensitive imaging in dentistry and soft tissue diagnostics.

Otoconia and corpuscles dissected from the inner ear of mice were investigated using polarization-resolved second harmonic generation microscopy (PSHG) to extract ultrastructural parameters. The PSHG parameter, ρ, typically related to helical tilt in collagen, was calculated for each image pixel, and the average ρ values were found to be 4.6 for corpuscles and -3.3 for otoconia. The negative ρ from otoconia was measured unambiguously, indicating that the symmetry of SHG emitters is not predominantly uniaxial, in contrast to typical biological SHG emitters such as collagen, myosin, or starch. The internal distribution of ρ values of corpuscles was radial and resembled the average ρ values of starch. Simulating otoconia structure as consisting of a biaxial system with two similar emitters > 90° apart predicts that disorder alters the measured ρ values, making them increasingly negative. An SHG measurement of otoconia during degradation was performed, revealing that the ρ values of otoconia significantly decrease with degradation in agreement with this model.

Sickle cell disease causes alterations in cerebral blood flow (CBF) and a high risk of stroke. Monitoring CBF in these patients may provide valuable information about neurovascular compromise. Diffuse correlation spectroscopy (DCS) is a promising approach for non-invasively estimating an index of regional CBF; however, foundational studies are needed to validate DCS against clinical standards for estimating CBF in this clinical population. Here, we demonstrate that DCS significantly correlates with transcranial Doppler ultrasound-measured blood flow velocity in the anterior cerebral artery in 16 children with sickle cell disease (r = 0.82, p < 0.001). Correction for the influence of hematocrit on BFI did not significantly change this correction.

Hemodynamic-based neuroimaging and non-neuroimaging techniques are widely used in neuroscience and functional studies. Probing spontaneous or induced hemodynamic oscillations by light, such as coherent hemodynamics spectroscopy (CHS), has emerged as an effective approach for quantifying cerebral microcirculation and vascular autoregulation. We introduce dynamic Windkessel autoregulation, which enables noninvasive quantification of microcirculation, oxygen diffusion rates, and vascular autoregulation from low-frequency oscillations (LFOs). The model incorporates arteriole vasomotor responses to blood pressure variations and quantifies autoregulatory capacity using a dimensionless autoregulation gain index n, which decreases with impaired autoregulation. The model accurately reproduced observed microcirculation and arterial blood flow and volume LFO responses, enabling straightforward quantification of vascular autoregulation. Furthermore, we integrate the model into WK-PIPE CHS and demonstrate recovery of key hemodynamic parameters, including the local tissue oxygen diffusion rate (α=0.179 ± 0.049s^-1) and vascular autoregulation (n = 4.68 ± 0.59) on five healthy human subjects imaged with visible structured light under paced breathing. Dynamic Windkessel autoregulation, as a mechanistic framework for vascular autoregulation, offers potential applications in monitoring cerebrovascular and cardiovascular health and early detection of their dysfunction using optical hemodynamic imaging.

This study introduces a terahertz (THz) biosensor for detecting blood Fe³⁺, addressing the limitations of conventional methods such as spectrophotometry, atomic absorption spectrometry, and electrochemical assays, which often suffer from matrix interference, high cost, and electrode fouling. The core innovation of our approach lies in the synergistic integration of a rotatable cross-shaped metasurface with a tungsten ditelluride (WTe₂) coating. This design distinctively enhances sensitivity through polarization-dependent resonant absorption at 0.1 THz, a frequency specifically matched to the ligand-field vibrational modes of Fe³⁺-containing complexes (e.g., transferrin-bound Fe³⁺). The WTe₂ layer, a type-II Weyl semimetal, transduces the enhanced THz absorption into measurable photocurrent changes with high efficiency due to its ultrahigh carrier mobility (>10,000 cm²V^-1s^-1). Experimental results provide concrete evidence of superior performance: a wide linear detection range from 0.1 to 1000 μg/L (with ΔI/I₀ showing excellent linearity against log(concentration), R²=0.994), an ultra-low detection limit of 0.05 μg/L, and minimal interference from common blood components like glucose and Ca²⁺, which exhibit negligible absorption at 0.1 THz. These specific metrics demonstrate a significant advancement over traditional techniques, particularly in sensitivity and compatibility with complex biological matrices. Furthermore, the THz-based method enables non-destructive detection. This work establishes a highly accurate, label-free strategy for quantifying blood Fe³⁺, offering substantial potential for clinical monitoring applications.

Retinal hyperspectral imaging holds significant promise for early disease diagnosis by quantifying the spectral signatures of metabolic and hemodynamic biomarkers. However, conventional hyperspectral imaging systems typically require extensive scanning, leading to prolonged acquisition times and rendering images susceptible to motion artifacts caused by involuntary eye movements. To address this limitation, we present a snapshot hyperspectral fundus camera employing a microlens array. The system features a streamlined optical architecture and compatibility with a standard commercial fundus camera across various field-of-view (FOV) configurations (20°, 35°, and 50°). Furthermore, the system allows a tunable balance between spectral resolution versus light throughput, enabling adaptation to a wide range of applications.

Fluorescence lifetime imaging microscopy (FLIM) is a sensitive technique that provides insight into molecular interactions, making it a powerful tool for understanding protein dynamics in neurodegenerative diseases. However, longitudinal FLIM studies over a number of days aimed at capturing complex protein behavior in live samples with high spatial granularity are limited by the need for rapid acquisition, implying few signal photons and high noise. Microscopy studies are further challenged by the complex lifetime mixtures present in many samples, leading to a more challenging extraction problem and the prospect of obscuring insight into the underlying molecular interactions. To enable accurate recovery in such situations, we present a noise estimation method that allows precise, pixel-wise determination of fluorescence lifetime parameters in such high-noise environments. In addition, we introduce a multi-exponential constrained fitting approach that enables robust multiparameter extraction from measured data with noisy data typical of neuron studies. The approach is validated using reference dyes and is further illustrated for neuronal imaging of the aggregation of alpha-synuclein, a key protein related to the onset and progression of Parkinson's disease. More broadly, reliable studies of protein dynamics become possible, thereby providing a means to advance our understanding of neurodegenerative disease etiology and offering applications across diverse molecular systems and in various disciplines.