Extended photoacoustic transport model for characterization of red blood cell morphology in microchannel flow

The dynamic response behavior of red blood cells holds the key to understanding red blood cell related diseases. In this regard, an understanding of the physiological functions of erythrocytes is significant before focusing on red blood cell aggregation in the microcirculatory system. In this work, we present a theoretical model for a photoacoustic signal that occurs when deformed red blood cells pass through a microfluidic channel. Using a Green's function approach, the photoacoustic pressure wave is obtained analytically by solving a combined Navier-Stokes and photoacoustic equation system. The photoacoustic wave expression includes determinant parameters for the cell deformability such as plasma viscosity, density, and red blood cell aggregation, as well as involving laser parameters such as beamwidth, pulse duration, and repetition rate. The effects of aggregation on blood rheology are also investigated. The results presented by this study show good agreements with the experimental ones in the literature. The comprehensive analytical solution of the extended photoacoustic transport model including a modified Morse type potential function sheds light on the dynamics of aggregate formation and demonstrates that the profile of a photoacoustic pressure wave has the potential for detecting and characterizing red blood cell aggregation.

Intravital imaging of a pulmonary endothelial surface layer in a murine sepsis model

Direct intravital imaging of an endothelial surface layer (ESL) in pulmonary microcirculation could be a valuable approach to investigate the role of a vascular endothelial barrier in various pathological conditions. Despite its importance as a marker of endothelial cell damage and impairment of the vascular system, in vivo visualization of ESL has remained a challenging technical issue. In this work, we implemented a pulmonary microcirculation imaging system integrated to a custom-design video-rate laser scanning confocal microscopy platform. Using the system, a real-time cellular-level microscopic imaging of the lung was successfully performed, which facilitated a clear identification of individual flowing erythrocytes in pulmonary capillaries. Subcellular level pulmonary ESL was identified in vivo by fluorescence angiography using a dextran conjugated fluorophore to label blood plasma and the red blood cell (RBC) exclusion imaging analysis. Degradation of ESL width was directly evaluated in a murine sepsis model in vivo, suggesting an impairment of pulmonary vascular endothelium and endothelial barrier dysfunction.

L1-norm based nonlinear reconstruction improves quantitative accuracy of spectral diffuse optical tomography

Spectrally constrained diffuse optical tomography (SCDOT) is known to improve reconstruction in diffuse optical imaging; constraining the reconstruction by coupling the optical properties across multiple wavelengths suppresses artefacts in the resulting reconstructed images. In other work, L1-norm regularization has been shown to improve certain types of image reconstruction problems as its sparsity-promoting properties render it robust against noise and enable the preservation of edges in images, but because the L1-norm is non-differentiable, it is not always simple to implement. In this work, we show how to incorporate L1 regularization into SCDOT. Three popular algorithms for L1 regularization are assessed for application in SCDOT: iteratively reweighted least square algorithm (IRLS), alternating directional method of multipliers (ADMM), and fast iterative shrinkage-thresholding algorithm (FISTA). We introduce an objective procedure for determining the regularization parameter in these algorithms and compare their performance in simulated experiments, and in real data acquired from a tissue phantom. Our results show that L1 regularization consistently outperforms Tikhonov regularization in this application, particularly in the presence of noise.

Atorvastatin treatment softens human red blood cells: an optical tweezers study

Optical tweezers are proven indispensable single-cell micro-manipulation and mechanical phenotyping tools. In this study, we have used optical tweezers for measuring the viscoelastic properties of human red blood cells (RBCs). Comparison of the viscoelastic features of the healthy fresh and atorvastatin treated cells revealed that the drug softens the cells. Using a simple modeling approach, we proposed a molecular model that explains the drug-induced softening of the RBC membrane. Our results suggest that direct interactions between the drug and cytoskeletal components underlie the drug-induced softening of the cells.

Diffuse optical monitoring of peripheral tissues during uncontrolled internal hemorrhage in a porcine model

Reliable, continuous and noninvasive blood flow and hemoglobin monitoring in trauma patients remains a critical, but generally unachieved goal. Two optical sensing methods - diffuse correlation spectroscopy (DCS) and diffuse reflectance spectroscopy (DRS) - are used to monitor and detect internal hemorrhage. Specifically, we investigate if cutaneous perfusion measurements acquired using DCS and DRS in peripheral (thighs and ear-lobe) tissues could detect severe hemorrhagic shock in a porcine model. Four animals underwent high-grade hepato-portal injury in a closed abdomen, to induce uncontrolled hemorrhage and were subsequently allowed to bleed for 10 minutes before fluid resuscitation. DRS and DCS measurements of cutaneous blood flow were acquired using fiber optical probes placed on the thigh and earlobe of the animals and were obtained repeatedly starting from 1 to 5 minutes pre-injury, up to several minutes post shock. Clear changes were observed in measured optical spectra across all animals at both sites. DCS-derived cutaneous blood flow decreased sharply during hemorrhage, while DRS-derived vascular saturation and hemoglobin paralleled cardiac output. All derived optical parameters had the steepest changes during the rapid initial hemorrhage unambiguously. This suggests that a combined DCS and DRS based device might provide an easy-to-use, non-invasive, internal-hemorrhage detection system that can be used across a wide array of clinical settings.

Investigation of albumin-derived perfluorocarbon-based capsules by holographic optical trapping

Albumin-derived perfluorocarbon-based capsules are promising as artificial oxygen carriers with high solubility. However, these capsules have to be studied further to allow initial human clinical tests. The aim of this paper is to provide and characterize a holographic optical tweezer to enable contactless trapping and moving of individual capsules in an environment that mimics physiological (in vivo) conditions most effectively in order to learn more about the artificial oxygen carrier behavior in blood plasma without recourse to animal experiments. Therefore, the motion behavior of capsules in a ring shaped or vortex beam is analyzed and optimized on account of determination of the optical forces in radial and axial direction. In addition, due to the customization and generation of dynamic phase holograms, the optical tweezer is used for first investigations on the aggregation behavior of the capsules and a statistical evaluation of the bonding in dependency of different capsule sizes is performed. The results show that the optical tweezer is sufficient for studying individual perfluorocarbon-based capsules and provide information about the interaction of these capsules for future use as artificial oxygen carriers.

Concurrent measurement of skeletal muscle blood flow during exercise with diffuse correlation spectroscopy and Doppler ultrasound

Noninvasive, direct measurement of local muscle blood flow in humans remains limited. Diffuse correlation spectroscopy (DCS) is an emerging technique to measure regional blood flow at the microvascular level. In order to better understand the strengths and limitations of this novel technique, we performed a validation study by comparing muscle blood flow changes measured with DCS and Doppler ultrasound during exercise. Nine subjects were measured (all males, 27.4 ± 2.9 years of age) for a rhythmic handgrip exercise at 20% and 50% of individual maximum voluntary contraction (MVC), followed by a post-exercise recovery. The results from DCS and Doppler ultrasound were highly correlated (R = 0.99 ± 0.02). DCS was more reliable and less susceptible to motion artifact.

Comparison of four methods of surface roughness assessment of corneal stromal bed after lamellar cutting

Corneal lamellar cutting with a blade or femtosecond laser (FSL) is commonly used during refractive surgery and corneal grafts. Surface roughness of the cutting plane influences postoperative visual acuity but is difficult to assess reliably. For the first time, we compared chromatic confocal microscopy (CCM) with scanning electron microscopy, atomic force microscopy (AFM) and focus-variation microscopy (FVM) to characterize surfaces of variable roughness after FSL cutting. The small area allowed by AFM hinders conclusive roughness analysis, especially with irregular cuts. FVM does not always differentiate between smooth and rough surfaces. Finally, CCM allows analysis of large surfaces and differentiates between surface states.

Rapid adaptive remote focusing microscope for sensing of volumetric neural activity

The ability to record neural activity in the brain of a living organism at cellular resolution is of great importance for defining the neural circuit mechanisms that direct behavior. Here we present an adaptive two-photon microscope optimized for extraction of neural signals over volumes in intact Drosophila brains, even in the presence of specimen motion. High speed volume imaging was made possible through reduction of spatial resolution while maintaining the light collection efficiency of a high resolution, high numerical aperture microscope. This enabled simultaneous recording of odor-evoked calcium transients in a defined volume of mushroom body Kenyon cell bodies in a live fruit fly.

Optical imaging for the assessment of hepatocyte metabolic state in ischemia and reperfusion injuries

Deterioration in mitochondrial function leads to hepatic ischemia and reperfusion injury (IRI) in liver surgery and transplantation. 3D optical cryoimaging was used to measure the levels of mitochondrial coenzymes NADH and FAD, and their redox ratio (NADH/FAD) gave a quantitative marker for hepatocyte oxidative stress during IRI. Using a rat model, five groups were compared: control, ischemia for 60 or 90 minutes (Isc60, Isc90), ischemia for 60 or 90 minutes followed by reperfusion of 24 hours (IRI60, IRI90). Ischemia alone did not cause a significant increase in the redox ratio; however, the redox ratio in both IRI60 and IRI90 groups was significantly decreased by 29% and 71%, respectively. A significant correlation was observed between the redox ratio and other markers of injury such as serum aminotransferase levels and the tissue ATP level. The mitochondrial redox state can be successfully measured using optical cryoimaging as a quantitative marker of hepatic IR injury.

Analysis of poration-induced changes in cells from laser-activated plasmonic substrates

Laser-exposed plasmonic substrates permeabilize the plasma membrane of cells when in close contact to deliver cell-impermeable cargo. While studies have determined the cargo delivery efficiency and viability of laser-exposed plasmonic substrates, morphological changes in a cell have not been quantified. We porated myoblast C2C12 cells on a plasmonic pyramid array using a 532-nm laser with 850-ps pulse length and time-lapse fluorescence imaging to quantify cellular changes. We obtain a poration efficiency of 80%, viability of 90%, and a pore radius of 20 nm. We quantified area changes in the plasma membrane attached to the substrate (10% decrease), nucleus (5 - 10% decrease), and cytoplasm (5 - 10% decrease) over 1 h after laser treatment. Cytoskeleton fibers show a change of 50% in the alignment, or coherency, of fibers, which stabilizes after 10 mins. We investigate structural and morphological changes due to the poration process to enable the safe development of this technique for therapeutic applications.

Examination of Drosophila eye development with third harmonic generation microscopy

Third harmonic generation (THG) microscopy can exploit endogenous harmonophores such as pigment macromolecules for enhanced image contrast, and therefore can be used without exogenous contrast agents. Previous studies have established that carotenoid compounds are ideal harmonophores for THG microscopy; we therefore sought to determine whether THG from endogenous carotenoid-derived compounds, such as retinal in photoreceptor cells, could serve as a new label-free method for developmental studies. Here we study the development of the pupal eye in Drosophila melanogaster and determine the localization of rhodopsin using THG microscopy technique. Additionally, by altering the chromophore or the opsin protein we were able to detect changes in both the retinal distribution morphology and in THG intensity age-dependent profiles. These results demonstrate that THG microscopy can be used to detect altered photoreceptor development and may be useful in clinically relevant conditions associated with photoreceptor degeneration.

Mitotic tethers connect sister chromosomes and transmit "cross-polar" force during anaphase A of mitosis in PtK2 cells

Originally described in crane-fly spermatocytes, tethers physically link and transmit force between the ends of separating chromosomes. Optical tweezers and laser scissors were used to sever the tether between chromosomes, create chromosome fragments attached to the tether which move toward the opposite pole, and to trap the tethered fragments. Laser microsurgery in the intracellular space between separating telomeres reduced chromosome strain in half of tested chromosome pairs. When the telomere-containing region was severed from the rest of the chromosome body, the resultant fragment either traveled towards the proper pole (poleward), towards the sister pole (cross-polar), or movement ceased. Fragment travel towards the sister pole varied in distance and always ceased following a cut between telomeres, indicating the tether is responsible for transferring a cross-polar force to the fragment. Optical trapping of cross-polar traveling fragments places an upper boundary on the tethering force of ~1.5 pN.

Effect of red light on optically trapped spermatozoa

Successful artificial insemination relies on the use of high quality spermatozoa. One measure of sperm quality is swimming force. Increased swimming force has been correlated with higher sperm swimming speeds and improved reproductive success. It is hypothesized that by increasing sperm swimming speed, one can increase swimming force. Previous studies have shown that red light irradiation causes an increase in sperm swimming speed. In the current study, 633nm red light irradiation is shown to increase mean squared displacement in trapped sperm. The methodology allows for comparison of relative swimming forces between irradiated and non-irradiated samples.

Detection of rotavirus in clinical specimens using an immunosensor prototype based on the photon burst counting technique

In this study, a sensitive fluorescence sensor was developed for the detection of small, fluorescence-labeled particles dispersed in a solution. The prototype system comprises of a laser confocal optical system and a mechanical sample stage to detect photon bursting of fluorescence-labeled small particles in sample volumes less than 5 μL within 3 minutes. To examine the feasibility of the prototype system as a diagnostic tool, assemblages of rotavirus and fluorescence-labeled antibody were analyzed. The detection sensitivity for rotavirus was 1 × 10⁴ pfu/mL. Rotavirus in stool samples from patients with acute gastroenteritis was also detected. The advantages and disadvantages of this immunosensor with respect to ELISA and RT-PCR, the current gold standards for virus detection, are discussed.

Flow-mediated dilatation test using optoacoustic imaging: a proof-of-concept

Label-free multispectral optoacoustic tomography (MSOT) has recently shown superior performance in visualizing the morphology of human vasculature, especially of smaller vessels, compared to ultrasonography. Herein, we extend these observations towards MSOT interrogation of macrovascular endothelial function. We employed a real-time handheld MSOT scanner to assess flow-mediated dilatation (FMD), a technique used to characterize endothelial function. A data processing scheme was developed to quantify the dimensions and diameter changes of arteries in humans and determine wall distensibility parameters. By enabling high-resolution delineation of the blood-vessel wall in a cross-sectional fashion, the findings suggest MSOT as a capable alternative to ultrasonography for clinical FMD measurements.

Visible spectrum extended-focus optical coherence microscopy for label-free sub-cellular tomography

We present a novel extended-focus optical coherence microscope (OCM) attaining 0.7 μm axial and 0.4 μm lateral resolution maintained over a depth of 40 μm, while preserving the advantages of Fourier domain OCM. Our system uses an ultra-broad spectrum from a supercontinuum laser source. As the spectrum spans from near-infrared to visible wavelengths (240 nm in bandwidth), we call the system visOCM. The combination of such a broad spectrum with a high-NA objective creates an almost isotropic 3D submicron resolution. We analyze the imaging performance of visOCM on microbead samples and demonstrate its image quality on cell cultures and ex-vivo brain tissue of both healthy and alzheimeric mice. In addition to neuronal cell bodies, fibers and plaques, visOCM imaging of brain tissue reveals fine vascular structures and sub-cellular features through its high spatial resolution. Sub-cellular structures were also observed in live cells and were further revealed through a protocol traditionally used for OCT angiography.

Study of in vitro RBCs membrane elasticity with AOD scanning optical tweezers

The elasticity of red cell membrane is a critical physiological index for the activity of RBC. Study of the inherent mechanism for RBCs membrane elasticity transformation is attention-getting all along. This paper proposes an optimized measurement method of erythrocytes membrane shear modulus incorporating acousto-optic deflector (AOD) scanning optical tweezers system. By use of this method, both membrane shear moduli and sizes of RBCs with different in vitro times were determined. The experimental results reveal that the RBCs membrane elasticity and size decline with in vitro time extension. In addition, semi quantitative measurements of S-nitrosothiol content in blood using fluorescent spectrometry during in vitro storage show that RBCs membrane elasticity change is positively associated with the S-nitrosylation level of blood. The analysis considered that the diminished activity of the nitric oxide synthase makes the S-nitrosylation of in vitro blood weaker gradually. The main reason for worse elasticity of the in vitro RBCs is that S-nitrosylation effect of spectrin fades. These results will provide a guideline for further study of in vitro cells activity and other clinical applications.

Modulation of cardiomyocyte activity using pulsed laser irradiated gold nanoparticles

Can photothermal gold nanoparticle mediated laser manipulation be applied to induce cardiac contraction? Based on our previous work, we present a novel concept of cell stimulation. A 532 nm picosecond laser was employed to heat gold nanoparticles on cardiomyocytes. This leads to calcium oscillations in the HL-1 cardiomyocyte cell line. As calcium is connected to the contractility, we aimed to alter the contraction rate of native and stem cell derived cardiomyocytes. A contraction rate increase was particularly observed in calcium containing buffer with neonatal rat cardiomyocytes. Consequently, the study provides conceptual ideas for a light based, nanoparticle mediated stimulation system.

Supra-organization and optical anisotropies of the extracellular matrix in the amniotic membrane and limbal stroma before and after explant culture

In this research we evaluated the supramolecular organizations and the optical anisotropical properties of the de-epithelialized human amniotic membrane and rabbit limbal stroma, before and after explant culture. Birefringence, monochromatic light spectral absorption and linear dichroism of the main extracellular matrix biopolymers, that is, the fibrillar collagens and proteoglycans, were investigated by polarized light microscopy combined with image analysis. Our results demonstrated that the culture procedure-induced stimuli altered the supra-organizational characteristics (in terms of collagens/proteoglycans spatial orientation and ordered-aggregational state) of the amniotic and limbal extracellular matrix, which led to changes in optical anisotropical properties.

Using electron microscopy to calculate optical properties of biological samples

The microscopic structural origins of optical properties in biological media are still not fully understood. Better understanding these origins can serve to improve the utility of existing techniques and facilitate the discovery of other novel techniques. We propose a novel analysis technique using electron microscopy (EM) to calculate optical properties of specific biological structures. This method is demonstrated with images of human epithelial colon cell nuclei. The spectrum of anisotropy factor g, the phase function and the shape factor D of the nuclei are calculated. The results show strong agreement with an independent study. This method provides a new way to extract the true phase function of biological samples and provides an independent validation for optical property measurement techniques.

Monitoring cerebral oxygenation and local field potential with a variation of isoflurane concentration in a rat model

We aimed to investigate experimentally how anesthetic levels affect cerebral metabolism measured by near-infrared spectroscopy (NIRS) and to identify a robust marker among NIRS parameters to discriminate various stages of anesthetic depth in rats under isoflurane anesthesia. In order to record the hemodynamic changes and local field potential (LFP) in the brain, fiber-optic cannulae and custom-made microelectrodes were implanted in the frontal cortex of the skull. The NIRS and LFP signals were continuously monitored before, during and after isoflurane anesthesia. As isoflurane concentration is reduced, the level of oxyhemoglobin and total hemoglobin concentrations of the frontal cortex decreased gradually, while deoxyhemoglobin increased. The reflectance ratio between 730nm and 850nm and burst suppression ratio (BSR) correspond similarly with the change of oxyhemoglobin during the variation of isoflurane concentration. These results suggest that NIRS signals in addition to EEG may provide a possibility of developing a new anesthetic depth index.

3D imaging in CUBIC-cleared mouse heart tissue: going deeper

The ability to acquire high resolution 3D images of the heart enables to study heart diseases more in detail. In this work, the CUBIC (clear, unobstructed brain imaging cocktails and computational analysis) clearing protocol was optimized for thick mouse heart sections to enhance the penetration depth of the confocal microscope lasers into the tissue. In addition, the optimized CUBIC clearing of the heart enhances antibody penetration into the tissue by a factor of five. The present protocol enables deep 3D high-quality image acquisition in the heart allowing a much more accurate assessment of the cellular and structural changes that underlie heart diseases.

Lowering photosensitizer doses and increasing fluences induce apoptosis in tumor bearing mice

The objective of this study was to determine an optimal dose of photodynamic therapy (PDT) for inducing apoptotic tumor cells in vivo. In this context, mice bearing human tongue-squamous epithelium carcinomas were treated with various photosensitizer concentrations and fluences. Tumor apoptosis was imaged after 2 days via a self-designed DY-734-annexin V probe using near-infrared fluorescence (NIRF) optical imaging. Apoptosis was verified ex vivo via TUNEL staining. Apoptotic tumor cells were detected in vivo at a dose of 40 µg photosensitizer and a fluency of 100 J/cm(2). This is the lowest photosensitizer dose reported so far.

Characterization of femtosecond-laser pulse induced cell membrane nanosurgical attachment

This article provides insight into the mechanism of femtosecond laser nanosurgical attachment of cells. We have demonstrated that during the attachment of two retinoblastoma cells using sub-10 femtosecond laser pulses, with 800 nm central wavelength, the phospholipid molecules of both cells hemifuse and form one shared phospholipid bilayer, at the attachment location. In order to verify the hypothesis that hemifusion takes place, transmission electron microscope images of the cell membranes of retinoblastoma cells were taken. It is shown that at the attachment interface, the two cell membranes coalesce and form one single membrane shared by both cells. Thus, further evidence is provided to support the hypothesis that laser-induced ionization process led to an ultrafast reversible destabilization of the phospholipid layer of the cellular membrane, which resulted in cross-linking of the phospholipid molecules in each membrane. This process of hemifusion occurs throughout the entire penetration depth of the femtosecond laser pulse train. Thus, the attachment between the cells takes place across a large surface area, which affirms our findings of strong physical attachment between the cells. The femtosecond laser pulse hemifusion technique can potentially provide a platform for precise molecular manipulation of cellular membranes. Manipulation of the cellular membrane is an important procedure that could aid in studying diseases such as cancer; where the expression level of plasma proteins on the cell membrane is altered.

Fluorescence properties of several chemotherapy drugs: doxorubicin, paclitaxel and bleomycin

Several chemo-drugs act as the biocompatible fluorophores. Here, the laser induced fluorescence (LIF) properties of doxorubicin, paclitaxel and bleomycin are investigated. The absorption lines mostly lie over UV range according to the UV-VIS spectra. Therefore, a single XeCl laser provokes the desired transitions of the chemo-drugs of interest at 308 nm. It is shown that LIF spectra are strongly dependent on the fluorophore concentration giving rise to the sensible red shift. This happens when large overlapping area appears between absorption and emission spectra accordingly. The red shift is taken into account as a characteristic parameter of a certain chemo-drug. The fluorescence extinction (α) and self-quenching (k) coefficients are determined based on the best fitting of the adopted Lambert-Beer equation over experimental data. The quantum yield of each chemo-drug is also measured using the linearity of the absorption and emission rates.

Changes in autofluorescence based organoid model of muscle invasive urinary bladder cancer

Muscle invasive urinary bladder cancer is one of the most lethal cancers and its detection at the time of transurethral resection remains limited and diagnostic methods are urgently needed. We have developed a muscle invasive transitional cell carcinoma (TCC) model of the bladder using porcine bladder scaffold and the human bladder cancer cell line 5637. The progression of implanted cancer cells to muscle invasion can be monitored by measuring changes in the spectrum of endogenous fluorophores such as reduced nicotinamide dinucleotide (NADH) and flavins. We believe this could act as a useful tool for the study of fluorescence dynamics of developing muscle invasive bladder cancer in patients. Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Optically trapping tumor cells to assess differentiation and prognosis of cancers

We report an optical trapping method that may enable assessment of the differentiation status of cancerous cells by determining the minimum time required for cell-cell adhesion to occur. A single, live cell is trapped and brought into close proximity of another; the minimum contact time required for cell-cell adhesion to occur is measured using transformed cells from neural tumor cell lines: the human neuroblastoma SK-N-SH and rat C6 glioma cells. Earlier work on live adult rat hippocampal neural progenitors/stem cells had shown that a contact minimum of ~5 s was required for cells to adhere to each other. We now find the average minimum time for adhesion of cells from both tumor cell lines to substantially increase to ~20-25 s, in some cases up to 45 s. Upon in vitro differentiation of these cells with all-trans retinoic acid the average minimum time reverts to ~5-7 s. This proof-of-concept study indicates that optical trapping may be a quick, sensitive, and specific method for determining differentiation status and, thereby, the prognosis of cancer cells.

Avian embryo monitoring during incubation using multi-channel diffuse speckle contrast analysis

Determining the survival rate of avian embryos during incubation is essential for cost-saving in the poultry industry. A multi-channel diffuse speckle contrast analysis (DSCA) system, comprising four optical fiber channels, is proposed to achieve noninvasive in vivo measurements of deep tissue flow. The system was able to monitor chick embryo vital signs over the entire incubation period. Moreover, it proved useful in distinguishing between chick embryos in healthy and weakened conditions.

Non-invasive manipulation of Drosophila behavior by two-photon excited red-activatable channelrhodopsin

Scattering and absorption limit light penetration through inhomogeneous tissue. To reduce scattering, biochemists have shifted the wavelengths of excitation light for optogenetic actuators and fluorescent proteins to the orange-red range, while physicists have developed multiphoton technologies for deep tissue stimulation. We have built a rapid multiphoton spectroscopic screening system of genetically encoded red-activatable channelrhodopsin (ReaChR), and considered specific behaviors in transgenic Drosophila melanogaster as readouts to optimize the laser parameters for two-photon optogenetic activation. A wavelength-tunable optical parametric amplifier was adopted as the major light source for widefield two-photon excitation (TPE) of ReaChR. Our assays suggest that the optimized TPE wavelength of ReaChR is 1250 nm. Exploiting its capacity for optogenetic manipulation to induce macroscopic behavioral change, we realized rapid spectroscopic screening of genetically encoded effectors or indicators in vivo, and used modulation of ReaChR in the fly as a successful demonstration of such a system.

Design and performance of an ultra-flexible two-photon microscope for in vivo research

We present a cost-effective in vivo two-photon microscope with a highly flexible frontend for in vivo research. Our design ensures fast and reproducible access to the area of interest, including rotation of imaging plane, and maximizes space for auxiliary experimental equipment in the vicinity of the animal. Mechanical flexibility is achieved with large motorized linear stages that move the objective in the X, Y, and Z directions up to 130 mm. 360° rotation of the frontend (rotational freedom for one axis) is achieved with the combination of a motorized high precision bearing and gearing. Additionally, the modular design of the frontend, based on commercially available optomechanical parts, allows straightforward updates to future scanning technologies. The design exceeds the mobility of previous movable microscope designs while maintaining high optical performance.

Longitudinal far red gene-reporter imaging of cancer metastasis in preclinical models: a tool for accelerating drug discovery

In this short communication, we demonstrate for the first time, the use of far red fluorescent gene reporter, iRFP to longitudinally and non-invasively track the in vivo process of lymphatic metastases from an orthotopic site of mammary implantation through lymphatic vessels and to draining lymph nodes. Potentially useful to accelerate cancer drug discovery as an in vivo screening tool to monitor the pharmacological arrest of metastasis, we show that the custom as well as commercial small animal imaging devices have adequate performance to detect the gene reporter in stably expressing metastatic cancer cells.

In vivo imaging of activated microglia in a mouse model of focal cerebral ischemia by two-photon microscopy

Microglia are brain resident macrophages rapidly responding to various stimuli to exert appropriate inflammatory responses. Although they have recently been exploited as an attractive candidate for imaging neuroinflammation, it is still difficult to visualize them at the cellular and molecular levels. Here we imaged activated microglia by establishing intracranial window chamber (ICW) in a mouse model of focal cerebral ischemia by using two-photon microscopy (TPM), in vivo. Intravenous injection of fluorescent antibodies allowed us to detect significantly elevated levels of Iba-1 and CD68 positive activated microglia in the ipsilateral compared to the contralateral side of the infarct. We further observed that indomethacin, a non-steroidal anti-inflammatory drug significantly attenuated CD68-positive microglial activation in ICW, which was further confirmed by qRT-PCR biochemical analyses. In conclusion, we believe that in vivo TPM imaging of ICW would be a useful tool to screen for therapeutic interventions lowering microglial activation hence neuroinflammation.

In vivo quantitation of injected circulating tumor cells from great saphenous vein based on video-rate confocal microscopy

The number of circulating tumor cell (CTC) in the peripheral blood of cancer patients can be a valuable biomarker for cancer diagnosis and treatment monitoring. In this study, we implemented a custom-design video-rate confocal microscopy system in capable of direct visualization of fast flowing CTC at great saphenous vein (GSV) of a live animal model in vivo. Continuous acquisition of video-rate images at GSV revealed the highly dynamic time-dependent changes in the number of intravenously injected circulating tumor cells. By extracting a calibration factor through the hemocytometric analysis of intravenously injected long-circulating red blood cells, we established a novel quantitation method for CTC in whole body blood in vivo.

Blind source separation of ex-vivo aorta tissue multispectral images

Blind Source Separation methods (BSS) aim for the decomposition of a given signal in its main components or source signals. Those techniques have been widely used in the literature for the analysis of biomedical images, in order to extract the main components of an organ or tissue under study. The analysis of skin images for the extraction of melanin and hemoglobin is an example of the use of BSS. This paper presents a proof of concept of the use of source separation of ex-vivo aorta tissue multispectral Images. The images are acquired with an interference filter-based imaging system. The images are processed by means of two algorithms: Independent Components analysis and Non-negative Matrix Factorization. In both cases, it is possible to obtain maps that quantify the concentration of the main chromophores present in aortic tissue. Also, the algorithms allow for spectral absorbance of the main tissue components. Those spectral signatures were compared against the theoretical ones by using correlation coefficients. Those coefficients report values close to 0.9, which is a good estimator of the method's performance. Also, correlation coefficients lead to the identification of the concentration maps according to the evaluated chromophore. The results suggest that Multi/hyper-spectral systems together with image processing techniques is a potential tool for the analysis of cardiovascular tissue.

Decrease in fluorescence lifetime by glycation of collagen and its application in determining advanced glycation end-products in human dentin

Advanced Glycation End-products (AGEs) are produced by the Maillard reaction, which causes cross-linking of collagen and results in changes in the mechanical properties of collagen tissues. Several types of AGE fluoresce, and measurement of this fluorescence is effective for determining the presence of AGEs. Because fluorescence intensity by steady-state fluorometry is affected by sample surface condition and light source, we focused on fluorescence lifetime measurement (FLM). We found that fluorescence lifetime of collagen gel decreased with glycation progress. In vivo application of FLM for determination of AGEs was confirmed in human dentin.

A new strategy for label-free detection of lymphoma cancer cells

In this paper, a new strategy for highly selective and sensitive direct detection of lymphoma cells by exploiting the interaction between a peptide and its B-cell receptor, has been evaluated. In particular, an idiotype peptide, able to specifically bind the B-cell receptor of A20 cells in mice engrafted with A20 lymphoma, has been used as molecular probe. The new detection technique has been demonstrated on a planar crystalline silicon chip. Coverage of 85% of silicon surface and detection efficiency of 8.5 × 10(-3) cells/μm(2) were obtained. The recognition strategy promises to extend its application in studying the interaction between ligands and their cell-surface receptors.

Significant correlation between refractive index and activity of mitochondria: single mitochondrion study

Measurements of refractive indices (RIs) of intracellular components can provide useful information on the structure and function of cells. The present study reports, for the first time, determination of the RI of an isolated mitochondrion in isotonic solution using retardation-modulated differential interference contrast microscopy. The value was 1.41 ± 0.01, indicating that mitochondria are densely packed with molecules having high RIs. Further, the RIs of each mitochondrion were significantly correlated with the mitochondrial membrane potential, an index of mitochondrial activity. These results will provide useful information on the structures and functions of cells based on the intracellular distribution of RIs.

Automated method for the segmentation and morphometry of nerve fibers in large-scale CARS images of spinal cord tissue

A fully automated method for large-scale segmentation of nerve fibers from coherent anti-Stokes Raman scattering (CARS) microscopy images is presented. The method is specifically designed for CARS images of transverse cross sections of nervous tissue but is also suitable for use with standard light microscopy images. After a detailed description of the two-part segmentation algorithm, its accuracy is quantified by comparing the resulting binary images to manually segmented images. We then demonstrate the ability of our method to retrieve morphological data from CARS images of nerve tissue. Finally, we present the segmentation of a large mosaic of CARS images covering more than half the area of a mouse spinal cord cross section and show evidence of clusters of neurons with similar g-ratios throughout the spinal cord.

Ex vivo 4D visualization of aortic valve dynamics in a murine model with optical coherence tomography

The heart and its mechanical components, especially the heart valves and leaflets, are under enormous strain and undergo fatigue, which impinge upon cardiac output. The knowledge about changes of the dynamic behavior and the possibility of early stage diagnosis could lead to the development of new treatment strategies. Animal models are suited for the development and evaluation of new experimental approaches and therefor innovative imaging techniques are necessary. In this study, we present the time resolved visualization of healthy and calcified aortic valves in an ex vivo artificially stimulated heart model with 4D optical coherence tomography and high-speed video microscopy.

Wide field intravital imaging by two-photon-excitation digital-scanned light-sheet microscopy (2p-DSLM) with a high-pulse energy laser

Digital-scanned light-sheet microscopy (DSLM) illuminates a sample in a plane and captures single-photon-excitation fluorescence images with a camera from a direction perpendicular to the light sheet. This method is potentially useful for observing biological specimens, because image acquisition is relatively fast, resulting in reduction of phototoxicity. However, DSLM cannot be effectively applied to high-scattering materials due to the image blur resulting from thickening of the light sheet by scattered photons. However, two-photon-excitation DSLM (2p-DSLM) enables collection of high-contrast image with near infrared (NIR) excitation. In conventional 2p-DSLM, the minimal excitation volume for two-photon excitation restricts the field of view. In this study, we achieved wide-field 2p-DSLM by using a high-pulse energy fiber laser, and then used this technique to perform intravital imaging of a small model fish species, medaka (Oryzias latipes). Wide fields of view (>700 μm) were achieved by using a low-numerical aperture (NA) objective lens and high-peak energy NIR excitation at 1040 nm. We also performed high-speed imaging at near-video rate and successfully captured the heartbeat movements of a living medaka fish at 20 frames/sec.

Surface modification of silica particles with gold nanoparticles as an augmentation of gold nanoparticle mediated laser perforation

Gold nanoparticle mediated (GNOME) laser transfection/perforation fulfills the demands of a reliable transfection technique. It provides efficient delivery and has a negligible impact on cell viability. Furthermore, it reaches high-throughput applicability. However, currently only large gold particles (> 80 nm) allow successful GNOME laser perforation, probably due to insufficient sedimentation of smaller gold nanoparticles. The objective of this study is to determine whether this aspect can be addressed by a modification of silica particles with gold nanoparticles. Throughout the analysis, we show that after the attachment of gold nanoparticles to silica particles, comparable or better efficiencies to GNOME laser perforation are reached. In combination with 1 µm silica particles, we report laser perforation with gold nanoparticles with sizes down to 4 nm. Therefore, our investigations have great importance for the future research in and the fields of laser transfection combined with plasmonics.

In vivo quantitative photoacoustic microscopy of gold nanostar kinetics in mouse organs

We developed a high-resolution photoacoustic microscopy (PAM) system with a near-infrared (NIR) laser to noninvasively monitor the distribution of gold nanostar (GNS) in blood vessels, liver and spleen in mice. Photoacoustic images of organs at deep depths were continuously acquired in vivo every 30 minutes after a single dose of GNS by tail vein injection. The experimental results showed that GNS accumulated significantly in both liver and spleen from blood circulation after administration, which was qualitatively validated by fluorescence imaging. Our studies demonstrate that PAM might be potentially used for noninvasive tracing the kinetics of exogenous nanoparticles in biological system.

A quantitative method for measurement of HL-60 cell apoptosis based on diffraction imaging flow cytometry technique

A quantitative method for measurement of apoptosis in HL-60 cells based on polarization diffraction imaging flow cytometry technique is presented in this paper. Through comparative study with existing methods and the analysis of diffraction images by a gray level co-occurrence matrix algorithm (GLCM), we found 4 GLCM parameters of contrast (CON), cluster shade (CLS), correlation (COR) and dissimilarity (DIS) exhibit high sensitivities as the apoptotic rates. It was further demonstrated that the CLS parameter correlates significantly (R(2) = 0.899) with the degree of nuclear fragmentation and other three parameters showed a very good correlations (R(2) ranges from 0.69 to 0.90). These results demonstrated that the new method has the capability for rapid and accurate extraction of morphological features to quantify cellular apoptosis without the need for cell staining.

Detection of swelling of single isolated mitochondrion with optical microscopy

Volume regulation under osmotic loading is one of the most fundamental functions in cells and organelles. However, the effective method to detect volume changes of a single organelle has not been developed. Here, we present a novel technique for detecting volume changes of a single isolated mitochondrion in aqueous solution based on the transmittance of the light through the mitochondrion. We found that 70% and 21% of mitochondria swelled upon addition of a hypotonic solution and Ca(2+), respectively. These results show the potential of the present technique to detect the physiological volume changes of individual small organelles such as mitochondria.

Thermoelastic displacement measured by DP-OCT for detecting vulnerable plaques

The detection of thermoelastic displacement by differential phase optical coherence tomography (DP-OCT) was analytically evaluated for identifying atherosclerotic plaques. Analytical solutions were developed to understand the dynamics of physical distribution of point hear sources during/after laser irradiation on thermoelastic responses of MION-injected tissue. Both analytical and experimental results demonstrated a delayed peak displacement along with slow decay after laser pulse due to heterogeneous distribution of the point heat sources. Detailed description of the heat sources in tissue as well as integration of a scanning mirror can improve computational accuracy as well as clinical applicability of DP-OCT for diagnosing vulnerable plaque.

High-resolution visualization of mouse cardiac microvasculature using optical histology

Cardiovascular disease typically is associated with dysfunction of the coronary vasculature and microvasculature. The study of cardiovascular disease typically involves imaging of the large coronary vessels and quantification of cardiac blood perfusion. These methods, however, are not well suited for imaging of the cardiac microvasculature. We used the optical histology method, which combines chemical optical clearing and optical imaging, to create high-resolution, wide-field maps of the cardiac microvasculature in ventral slices of mouse heart. We have demonstrated the ability of the optical histology method to enable wide-field visualization of the cardiac microvasculature in high-resolution and anticipate that optical histology may have significant impact in studying cardiovascular disease.

Two-peaked 5-ALA-induced PpIX fluorescence emission spectrum distinguishes glioblastomas from low grade gliomas and infiltrative component of glioblastomas

5-ALA-induced protoporphyrin IX (PpIX) fluorescence enables to guiding in intra-operative surgical glioma resection. However at present, it has yet to be shown that this method is able to identify infiltrative component of glioma. In extracted tumor tissues we measured a two-peaked emission in low grade gliomas and in the infiltrative component of glioblastomas due to multiple photochemical states of PpIX. The second emission peak appearing at 620 nm (shifted by 14 nm from the main peak at 634 nm) limits the sensibility of current methods to measured PpIX concentration. We propose new measured parameters, by taking into consideration the two-peaked emission, to overcome these limitations in sensitivity. These parameters clearly distinguish the solid component of glioblastomas from low grade gliomas and infiltrative component of glioblastomas.

Noninvasive vasculature detection using laser speckle imaging in avian embryos through intact egg in early incubation stage

Monitoring the vital signs of a developing embryo is very useful in avian breeding programs, especially during early days of incubation, so that dead or unfertilized eggs can be timely removed from incubator and new eggs can be placed in. A noninvasive system for detecting the vital signs of avian embryo through intact egg in early stage of incubation has been developed using laser speckle imaging (LSI). The system was based on the measurement of intensity fluctuations of speckle caused by the embryo's blood flow in the intact egg under laser light illumination. This system was found to be feasible in imaging the vasculature in the egg as well as confirming its fertilization or survival from the second day to fifth day of incubation while other reported noninvasive methods cannot detect vital signs of the embryo until the sixth day of incubation.

In vitro characterization of genetically expressed absorbing proteins using photoacoustic spectroscopy

Genetically expressed fluorescent proteins have been shown to provide photoacoustic contrast. However, they can be limited by low photoacoustic generation efficiency and low optical absorption at red and near infrared wavelengths, thus limiting their usefulness in mammalian small animal models. In addition, many fluorescent proteins exhibit low photostability due to photobleaching and transient absorption effects. In this study, we explore these issues by synthesizing and characterizing a range of commonly used fluorescent proteins (dsRed, mCherry, mNeptune, mRaspberry, AQ143, E2 Crimson) and novel non-fluorescent chromoproteins (aeCP597 and cjBlue and a non-fluorescent mutant of E2 Crimson). The photoacoustic spectra, photoacoustic generation efficiency and photostability of each fluorescent protein and chromoprotein were measured. Compared to the fluorescent proteins, the chromoproteins were found to exhibit higher photoacoustic generation efficiency due to the absence of radiative relaxation and ground state depopulation, and significantly higher photostability. The feasibility of converting an existing fluorescent protein into a non-fluorescent chromoprotein via mutagenesis was also demonstrated. The chromoprotein mutant exhibited greater photoacoustic signal generation efficiency and better agreement between the photoacoustic and the specific extinction coefficient spectra than the original fluorescent protein. Lastly, the genetic expression of a chromoprotein in mammalian cells was demonstrated. This study suggests that chromoproteins may have potential for providing genetically encoded photoacoustic contrast.