This study investigates the relationship between Pannexin 1 and refractive errors using a custom-made 1310nm OCT system, capable of imaging the whole eye. Prior research reported vision-related issues in Panx1 mutants but lacked insights into underlying mechanisms. Obtained OCT results establish a direct link between Pannexin1 (Pannexin 1a, Pannexin 1b, and Panx1DKO) and eye structure alterations, primarily manifesting as axial length elongation and negative RRE values, indicating myopia. Additionally, whole eye OCT imaging identifies several category of defects in the lens epithelium and aphakia. This research underscores Pannexin1's significance in visual system development and refractive errors, further emphasizing the diagnostic potential of optical coherence tomography in ophthalmology. Leveraging zebrafish as a model organism offers a unique opportunity to investigate genetic and cellular mechanisms influencing eye health, advancing our understanding of genetic factors and paving the way for further research and potential therapeutic interventions in the field of ophthalmology.
While paper-based rapid tests are abundantly used in medicine, their performance is limited by the poor limit of detection and binary response of the test. We have previously shown that interpreting rapid tests based on laser-induced photothermal responses can offer over an order magnitude improvement in test performance. This work reports on miniaturization of our photothermal sensing paradigm in a low-cost handheld device and its field validations. The hand-held device excites assay gold nanoparticles with a modulated, low-power LED while recording their thermal wave responses with low-cost single-element sensors. An Arduino-based processor demodulates thermal wave responses while offering internet-of-things capability. Results from a human study on detection and quantification of Cannabis consumption will also be presented and discussed.
KEYWORDS: Statistical analysis, Gold nanoparticles, Modeling, Data modeling, COVID 19, Surface plasmons, Diseases and disorders, Design and modelling, Demodulation, Control systems
Performance of paper-based rapid tests is limited by their poor limit of detection and binary response. We have developed a low-cost end-user device that overcomes the classic limitations of rapid tests. The Arduino-based hand-held device excites rapid test gold nanoparticles with modulated 532nm LED while recording their thermal wave response with low-cost thermometer ICs. Validation studies on COVID-19 antibodies and THC (psychoactive constituent of cannabis) in saliva demonstrates ability of the innovation in quantifying analyte concentrations and enhancing the limit of detection by over an order of magnitude.
This paper introduces an optimized and affordable optofluidic add-on device for continuous and rapid light sheet imaging of C. elegans. Platform utilizes an optofluidic chip with integrated PDMS microlens to generate a light-sheet and rapidly images worms flowing in a microchannel via a regular microscope. Validation results on control and 6-OHDA-exposed worms demonstrates the ability of platform in qualitative and quantitative imaging of neuronal degenerations at different ages. The developed affordable platform enables a conventional fluorescent microscope to offer high-content and high-throughput light-sheet images of C. elegans populations which is invaluable to aging, neurodegeneration, and drug discovery studies.
Refractive errors, such as myopia and hyperopia, are a major cause of visual impairment worldwide. The genetic basis of refractive errors is becoming increasingly understood, and the zebrafish has emerged as a powerful model organism for studying these disorders. In this study, we present evidence that establishes a connection between the mammalian connexin-36 (Cx36) ortholog gjd2b/Cx35.1, a key component of electrical synapses in zebrafish, as well as connexin-27(Cx27.5), and the occurrence of refractive errors. We investigated the morphological and behavioral changes in adult zebrafish. To assess these changes, we utilized a custom-developed 1310nm optical coherence tomography system for analysis of the entire eye. This analysis revealed development of hyperopic shifts in Cx35.1 knockouts, primarily due to a reduction in eye axial length, while no refractive anomalies were observed in Cx27.5 knockouts.
Antibodies that are produced following infection due to the SARS-CoV-2 virus or vaccination are critical for monitoring the immune response of an individual or the impact of the vaccine over time. As vaccines become available, there is a need for rapid, accurate, and low-cost point-of-care tools for monitoring the effectiveness of the vaccines over time at the population level. Here, we report the efficiency of a handheld point-of-care thermo-photonic device for quantifying anti-SARS-CoV-2 antibodies in humanized control positive solution. Results showed that the imager in conjunction with rapid diagnostic tests (RDT) can detect and quantify antibody levels within clinically relevant range and with a limit of detection of 0.1 µg/ml.
Transient-mode photothermal optical coherence tomography (TM-PT-OCT) is introduced as a high-speed and video rate implementation of PT-OCT. Here, the transient thermal response of samples to a low power PT laser pulsed excitation is interrogated through temperature-induced variations in the OCT phase signals. Results suggest that the proposed method enhances the PT-OCT imaging speed by more than two orders of magnitude compared to conventional PT-OCT with lockin detection. This enhancement not only enables video rate visualization of molecules of interest (MOI), but also opens the door for use of multiple PT lasers to perform spectroscopic PT-OCT for detection and differentiation of multiple MOI’s with distinct absorption spectra. To demonstrate feasibility, experimental results on detection and differentiation of lipid and collagen are presented and discussed.
This work reports on the development of a low-cost and compact optofluidic add-on device for converting a conventional wide-field microscope to a light sheet fluorescence microscope for immobilization-free imaging of the C. elegans model organism. The developed Polydimethylsiloxane (PDMS)-based optofluidic device consists of an integrated PDMS cylindrical lens for light-sheet generation and a microfluidics channel for flow-based translation of samples through the light sheet. Validation experiments on several strains of C. elegans demonstrate the ability of the device in volumetric imaging of the fluorescence expressions of entire worms in a few seconds, at the single-neuron resolution, and with high contrast.
Significance: Selective plane illumination microscopy (SPIM) is an emerging fluorescent imaging technique suitable for noninvasive volumetric imaging of C. elegans. These promising microscopy systems, however, are scarce in academic and research institutions due to their high cost and technical complexities. Simple and low-cost solutions that enable conversion of commonplace wide-field microscopes to rapid SPIM platforms promote widespread adoption of SPIM by biologist for studying neuronal expressions of C. elegans.
Aim: We sought to develop a simple and low-cost optofluidic add-on device that enables rapid and immobilization-free volumetric SPIM imaging of C. elegans with conventional fluorescent microscopes.
Approach: A polydimethylsiloxane (PDMS)-based device with integrated optical and fluidic elements was developed as a low-cost and miniaturized SPIM add-on for the conventional wide-field microscope. The developed optofluidic chip contained an integrated PDMS cylindrical lens for on-chip generation of the light-sheet across a microchannel. Cross-sectional SPIM images of C. elegans were continuously acquired by the native objective of microscope as worms flowed in an L-shape microchannel and through the light sheet.
Results: On-chip SPIM imaging of C. elegans strains demonstrated possibility of visualizing the entire neuronal system in few seconds at single-neuron resolution, with high contrast and without worm immobilization. Volumetric visualization of neuronal system from the acquired cross-sectional two-dimensional images is also demonstrated, enabling the standard microscope to acquire three-dimensional fluorescent images of C. elegans. The full-width at half-maximum width of the point spread function was measured as 1.1 and 2.4 μm in the lateral and axial directions, respectively.
Conclusion: The developed low-cost optofluidic device is capable of continuous SPIM imaging of C. elegans model organism with a conventional fluorescent microscope, at high speed, and with single neuron resolution.
A comprehensive theoretical model for photothermal optical coherence tomography (PT-OCT) has been developed considering opto-thermo-mechanical properties of sample and illumination conditions. Parametric studies show developed model, unlike previous models, can predict characteristic PT-OCT signal behaviours.
Photothermal optical coherence tomography (PT-OCT) is an extension of OCT that forms images based on both scattering and absorption of light. Conventional OCT measures the path length of elastically back-scattered light. Variation of the tissue’s local refractive index due to photothermal modulation results in a modulated OCT phase signal that relates to the absorption of light. Detailed understanding of the PT-OCT signal has the potential to provide insight into the chemical composition of tissue, and may pave a way to detecting and characterizing lipid-rich atherosclerotic plaques with intracoronary imaging in patients. Here, we investigated the dependence of the PT-OCT signal on concentration of a specific tissue component. We modeled the generated thermal wave field and the resulting PT-OCT signal as a function of concentration of this component using the bio-heat equation. We found that the significant parameters in determining the amplitude of the PT-OCT signals are the density, the absorption coefficient and the specific heat of the sample. All these parameters vary as a function of the sample composition, leading to a non-linear relation between PT-OCT signal and the concentration of the component of interest. Only in special cases, e.g. the oxygenation level of blood, when the absorption coefficient is the only varying parameter does a linear dependence arise. PT-OCT experiments on tissue-like samples, prepared by mixing mayonnaise (<80% lipid) and agar gel (<90% water) to mimic lipid-rich atherosclerotic plaques, confirmed the non-linear relation predicted by our model.
Lateral flow immunoassays (LFAs) are widely used platforms for point-of-care detection of target analytes; however, these rapid tests are not very sensitive and offer only binary results. In this study, highly sensitive thermo-photonic LFA readers were developed for the sensitive detection and quantification of tetrahydrocannabinol (THC) in oral fluids and the antibodies (IgM and IgG) developed against SARS-CoV-2 virus in human blood/plasma. Our results suggest developed readers not only improved the detection limit by more than an order of magnitude, but also enables reliable quantification of target analytes.
Significance: Photothermal optical coherence tomography (PT-OCT) has the promise to offer structural images coregistered with chemical composition information, which can offer a significant impact in early detection of diseases such as atherosclerosis.
Aim: We take the first step in understanding the relation between PT-OCT signals and the endogenous tissue composition by considering the interplay between the opto-thermo-physical properties of tissue as a function of its lipid composition and the ensuing effects on the PT-OCT signals.
Approach: Multiparameter theoretical estimates for PT-OCT signal as a function of composition in a two-component lipid–water model are derived and discussed. Experimental data from various concentrations of lipid in the form of droplets and injections under bovine cardiac muscle align with theoretical predictions.
Results: Theoretical and experimental results suggest that the variations of heat capacity and mass density with tissue composition significantly contribute to the amount of optical path length difference measured by OCT phase.
Conclusion: PT-OCT has the potential to offer key insights into the chemical composition of the subsurface lipid pools in tissue; however, the interpretation of results needs to be carried out by keeping the nonlinear interplay between the tissue of opto-thermo-physical properties and PT-OCT signals in mind.
Lock-in thermography (LIT) is a non-destructive testing technique with a broad spectrum of applications, spanning from detection of manufacturing defects in industrial samples to early diagnosis of diseases in hard and soft tissues. Nevertheless, commercialization and wide-spread adaption of LIT has long been impeded by the cost (usually $10k-$100k) and size of infrared cameras. In this paper, we demonstrate that this cost and size limitation can be overcome using cell-phone attachment infrared cameras/sensors. Developed low-cost and portable LIT systems use an intensity-modulated near infrared light for illumination while detecting thermal signatures by the low-cost cellphone attachment infrared camera (Seek thermal compact; Android). While the nominal frame rate of camera is less than 9fps, we have deciphered the communication protocol and frame information structure of the camera and set up packets of information and send them to the camera’s default endpoint address and, subsequently, acquire frame data from camera through a corresponding pipe. As such, the developed platform can control camera attributes through a simple USB interface while achieving a stable high frame rate of 33fps. To demonstrate performance of developed low-cost and portable system, two types of LIT experiments were conducted: (i) in response to the recent legalizations of marijuana in Canada, we interrogated photothermal responses of commercially available oral fluid latral flow immunoassays (LFAs), demonstrating reliable detection of THC (the psychoactive substance of cannabis) at concentrations as low as 2 ng/ml. (ii) To demonstrate ability of the system in early detection of dental caries, artificially induced early caries were created on healthy enamel surfaces and imaged with the low cost and portable system at different stages of formation. Results, suggest ability of the system in detection of caries at very early stages when neither x-ray nor visual-tactile inspection can detect them. Both sets of experiments clearly demonstrate the promise of the developed low-cost and portable LIT system in producing reliable LIT images, paving the way for translation of this technology to industry.
Lateral flow immunoassays (LFAs) have received much attention in recent years for detecting THC (a psychoactive ingredient of the cannabis plant) in oral fluids for point-of-care (POC) diagnostics. Specific advantages of screening oral fluids for THC include ease of sample collection in public and correlation of presence of THC in oral fluid with recent use of cannabis. However, despite their popularity, the detection limit of LFA is normally limited to greater than 25 ng/ml of THC in oral fluid which impedes the implementation of per se regulations in many jurisdictions (i.e., 1-5 ng/ml). To address this shortcoming, several LFA reader technologies have been developed in recent years but none of them have satisfied the required performance criteria of <80% sensitivity, specificity, and accuracy at per se limit, set by Driving Under the Influence of Drugs, Alcohol, and Medicines (DRUID). In this work, we explore Lock-In thermography (LIT) method for detecting THC in saliva-based LFA strips, utilizing thermal signatures of gold nanoparticles (GNPs) for interpretation of LFAs. Our results suggest that LIT enhances the limit of detection of the commercially available LFA by over an order of magnitude and promises an affordable solution that allows for proper enforcement of per se regulations worldwide.
Dukho Do, DongKyun Kang, Nima Tabatabaei, Catriona Grant, Norman Nishioka, Mireille Rosenberg, Paul Hesterberg, Qian Yuan, John Garber, Aubrey Katz, Wayne Shreffler, Guillermo Tearney
Eosinophilic Esophagitis (EoE) is an inflammatory disease caused by inhaled or ingested food allergies, and characterized by the infiltration of eosinophils in the esophagus. The gold standard for diagnosing EoE is to conduct endoscopy and obtain multiple biopsy specimens from different portions of the esophagus; an exam is considered positive if more than 15 eosinophils per high power field (HPF) in any of the biopsies. This method of diagnosis is problematic because endoscopic biopsy is expensive and poorly tolerated and the esophageal eosinophil burden needs to be monitored frequently during the course of the disease. Spectrally encoded confocal microscopy (SECM) is a high-speed confocal microscopy technology that can visualize individual eosinophils in large microscopic images of the human esophagus, equivalent to more than 30,000 HPF. Previously, we have demonstrated that tethered capsule SECM can be conducted in unsedated subjects with diagnosed EoE. However, speckle noise and the relatively low resolution in images obtained with the first capsule prototypes made it challenging to distinguish eosinophils from other cells. In this work, we present a next-generation tethered SECM capsule, which has been modified to significantly improve image quality. First, we substituted the single mode fiber with a dual-clad fiber to reduce speckle noise. A gradient-index multimode fiber was fusion spliced at the tip of the dual-clad fiber to increase the effective numerical aperture of the fiber from 0.09 to 0.15, expanding the beam more rapidly to increase the illumination aperture at the objective. These modifications enabled the new SECM capsule to achieve a lateral resolution of 1.8 µm and an axial resolution of 16.1 µm, which substantially improves the capacity of this probe to visualize cellular features in human tissue. The total size of the SECM capsule remained 6.75 mm in diameter and 31 mm in length. We are now in the process of testing this new SECM capsule in humans. Early results using this new SECM capsule suggest that this technology has the potential to be an effective tool for the diagnosis of EoE.
Photothermal optical coherence tomography (PT-OCT) employs a secondary intensity-modulated photothermal laser to create modulated thermal strains that cause variations of the refractive index in the proximity of absorbing chromophores. These variations are directly detected with phase-sensitive OCT and offer insight to the molecular composition and thermo-elastic properties of the sample. Here, we define optimal PT laser modulation parameters by investigating the effect of PT laser power and modulation frequency on the ensuing thermal waves and thermal waves’ impact on the spatial resolution of PT-OCT imaging based on numerical simulations of PT-OCT and samples containing point absorbers.
Early detection of the most prevalent oral disease worldwide, i.e., dental caries, still remains as one of the major challenges in dentistry. The current dental standard of care relies on caries detection methods, such as visual inspection and x-ray radiography, which lack the sufficient specificity and sensitivity to detect caries at early stages of formation when they can be healed. We report on the feasibility of early caries detection in a clinically and commercially viable thermophotonic imaging system. The system incorporates intensity-modulated laser light along with a low-cost long-wavelength infrared (LWIR; 8 to 14 μm) camera, providing diagnostic contrast based on the enhanced light absorption of early caries. The LWIR camera is highly suitable for integration into clinical platforms because of its low weight and cost. In addition, through theoretical modeling, we show that LWIR detection enhances the diagnostic contrast due to the minimal LWIR transmittance of enamel and suppression of the masking effect of the direct thermal Planck emission. Diagnostic performance of the system and its detection threshold are experimentally evaluated by monitoring the inception and progression of artificially induced occlusal and smooth surface caries. The results are suggestive of the suitability of the developed LWIR system for detecting early dental caries.
Eosinophilic Esophagitis (EoE) is caused by food allergies, and defined by histological presence of eosinophil cells in the esophagus. The current gold standard for EoE diagnosis is endoscopy with pinch biopsy to detect more than 15 eosinophils/ High power field (HPF). Biopsy examinations are expensive, time consuming and are difficult to tolerate for patients. Spectrally encoded confocal microscopy (SECM) is a high-speed reflectance confocal microscopy technology capable of imaging individual eosinophils as highly scattering cells (diameter between 8 µm to 15 µm) in the epithelium. Our lab has developed a tethered SECM capsule that can be swallowed by unsedated patients. The capsule acquires large area confocal images, equivalent to more than 30,000 HPFs, as it traverses through the esophagus. In this paper, we present the outcome of a clinical study using the tethered SECM capsule for diagnosing EoE. To date, 32 subjects have been enrolled in this study. 88% of the subjects swallowed the capsules without difficulty and of those who swallowed the capsule, 95% preferred the tethered capsule imaging procedure to sedated endoscopic biopsy. Each imaging session took about 12 ± 2.4 minutes during which 8 images each spanning of 24 ± 5 cm2 of the esophagus were acquired. SECM images acquired from EoE patients showed abundant eosinophils as highly scattering cells in squamous epithelium. Results from this study suggest that the SECM capsule has the potential to become a less-invasive, cost-effective tool for diagnosing EoE and monitoring the response of this disease to therapy.
Dental caries is one of the most prevailing oral diseases which can be healed if detected in early stages of formation. In this paper, we present a clinically and commercially viable thermophotonic imaging technology for detection of early enamel caries using an inexpensive long-wavelength infrared (LWIR) camera. The efficacy of the system is verified through theoretical simulations as well as experiments carried out on extracted teeth with natural and artificially-induced caries.
Dental caries is the leading cause of tooth loss, which can promptly be prevented if detected in early stages of progression. Unfortunately, conventional diagnostic modalities currently used in dentistry lack the sensitivity to detect early caries. The authors' intention is to compare the ability of polarized Raman spectroscopy and thermophotonic imaging to make early caries diagnosis. Extracted human teeth with no visible stain or defects were artificially demineralized in accordance to a well-known protocol in dentistry for simulated early caries development at several demineralization stages. Samples were then inspected using polarized Raman spectroscopy and thermophotonic imaging. The sensitivities of these two diagnostic modalities are compared, and the results are verified using transverse micro-radiography. It was found that compared to polarized Raman spectroscopy, thermophotonic imaging exhibits superior sensitivity to very early stages of demineralization.
Energy transport in diffusion-wave fields is gradient driven and therefore diffuse, yielding depth-integrated responses
with poor axial resolution. Using matched-filter principles, we propose a methodology enabling these parabolic
diffusion-wave energy fields to exhibit energy localization akin to propagating hyperbolic wave-fields. This not only
improves the axial resolution, but also allows for deconvolution of individual responses of superposed axially discrete
sources, opening a new field of depth-resolved subsurface thermal coherence tomography using diffusion waves. The
depth resolved nature of the developed methodology is verified through experiments carried out on phantoms and
biological samples. The results suggest that thermal coherence tomography can resolve deep structural changes in hard
dental and bone tissues. The sensitivity of the developed diagnostic imaging system is compared to that of polarized
Raman spectroscopy.
As an extension of frequency-domain photothermal radiometry, a novel dental-imaging modality, thermophotonic lock-in imaging (TPLI), is introduced. This methodology uses photothermal wave principles and is capable of detecting early carious lesions and cracks on occlusal and approximal surfaces as well as early caries induced by artificial demineralizing solutions. The increased light scattering and absorption within early carious lesions increases the thermal-wave amplitude and shifts the thermal-wave centroid, producing contrast between the carious lesion and the intact enamel in both amplitude and phase images. Samples with artificial and natural occlusal and approximal caries were examined in this study. Thermophotonic effective detection depth is controlled by the modulation frequency according to the well-known concept of thermal diffusion length. TPLI phase images are emissivity normalized and therefore insensitive to the presence of stains. Amplitude images, on the other hand, provide integrated information from deeper enamel regions. It is concluded that the results of our noninvasive, noncontacting imaging methodology exhibit higher sensitivity to very early demineralization than dental radiographs and are in agreement with the destructive transverse microradiography mineral density profiles.
Using photothermal wave principles and as an extension to the frequency-domain photothermal radiometry, a novel
dental imaging modality, thermophotonic lock-in imaging (TPLI), is introduced. In order to assess the capabilities of the
proposed methodology samples with natural and artificially-generated caries were examined and the results were
compared with the destructive transverse microradiography density profiles. It was found that the increased light
scattering and absorption within early carious lesions increases the thermal-wave amplitude and shifts the thermal-wave
centroid, producing contrast between the carious lesion and the intact enamel in both amplitude and phase images. Phase
images are emissivity normalized and therefore insensitive to the presence of stain. Amplitude images provide integrated
information from deeper enamel regions. It was concluded that the results of our non-invasive, non-contacting imaging
methodology exhibit significantly higher sensitivity to very early demineralization than dental radiographs and are in
agreement with the destructive transverse microradiography mineral density profiles.
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