Microglial activation plays an important role in neurodegenerative diseases. Once activated, they have macrophage-like capabilities, which can be beneficial by phagocytosis and harmful by secretion of neurotoxins. However, the resident microglia always fail to trigger an effective phagocytic response to clear dead cells or Aβ deposits during the progression of neurodegeneration. Therefore, the regulation of microglial phagocytosis is considered a useful strategy in searching for neuroprotective treatments. In this study, our results showed that low-power laser irradiation (LPLI) (20 J/cm²) could enhance microglial phagocytic function in LPS-activated microglia. We found that LPLI-mediated microglial phagocytosis is a Rac-1-dependent actin-based process, that a constitutively activated form of Rac1 (Rac1Q61L) induced a higher level of actin polymerization than cells transfected with wild-type Rac1, whereas a dominant negative form of Rac1 (Rac1T17N) markedly suppressed actin polymerization. In addition, the involvement of Rac1 activation after LPLI treatment was also observed by using a Raichu fluorescence resonance energy transfer (FRET)-based biosensor. We also found that PI3K/Akt pathway was required in the LPLI-induced Rac1 activation. Our research may provide a feasible therapeutic approach to control the progression of neurodegenerative diseases.

Near infrared (NIR) emitting quantum dots (QDs) is a promising candidate for biomedical imaging in living tissues. However, the biomedical application of NIR QDs was not satisfactory due to their toxicity. ₂ QDs was reported to have negligible toxicity in organisms. Therefore, the appropriate narrow bandgap and low toxicity of ₂ QDs facilitated them to be a promising contrast agent for fluorescence imaging. Here, a low toxicity, stable and highly luminescent NIR ₂ QDs were prepared by one-step aqueous method using 2-mercaptopropionic acid (MPA) as the coating layers. Emission wavelength of ₂ QDs could be tuned between 780 and 950 nm. MTT assay results indicated that there was no significant biotoxicty for ₂ QDs. These NIR QDs exhibited excellent biocompatibility in tumor cells. The cellular uptake and localization of ₂ QDs was studied using laser confocal scanning microscopy. ₂ QDs were effectively internalized by the cells. Therefore, ₂ QDs, acting as a novel fluorescence probe, has promising potential in biolabeling, deep tissue imaging, diagnostics and photodynamic therapy.

Insulin resistance is a hallmark of the metabolic syndrome and type 2 diabetes. Dysfunction of PI-3K/Akt signaling was involved in insulin resistance. Glucose transporter 4 (GLUT4) is a key factor for glucose uptake in muscle and adipose tissues, which is closely regulated by PI-3K/Akt signaling in response to insulin treatment. Low-power laser irradiation (LPLI) has been shown to regulate various physiological processes and induce the synthesis or release of multiple molecules such as growth factors, which (especially red and near infrared light) is mainly through the activation of mitochondrial respiratory chain and the initiation of intracellular signaling pathways. Nevertheless, it is unclear whether LPLI could promote glucose uptake through activation of PI-3K/Akt/GLUT4 signaling in 3T3L-1 adipocytes. In this study, we investigated how LPLI promoted glucose uptake through activation of PI-3K/Akt/GLUT4 signaling pathway. Here, we showed that GLUT4 was localized to the Golgi apparatus and translocated from cytoplasm to cytomembrane upon LPLI treatment in 3T3L-1 adipocytes, which enhanced glucose uptake. Moreover, we found that glucose uptake was mediated by the PI3-K/Akt2 signaling, but not Akt1 upon LPLI treatment with Akt isoforms gene silence and PI3-K/Akt inhibitors. Collectively, our results indicate that PI3-K/Akt2/GLUT4 signaling act as the key regulators for improvement of glucose uptake under LPLI treatment in 3T3L-1 adipocytes. More importantly, our findings suggest that activation of PI3-K/Akt2/GLUT4 signaling by LPLI may provide guidance in practical applications for promotion of glucose uptake in insulin-resistant adipose tissue.

Separation of arteries and veins in the cerebral cortex is of significant importance in the studies of cortical hemodynamics, such as the changes of cerebral blood flow, perfusion or oxygen concentration in arteries and veins under different pathological and physiological conditions. Yet the cerebral vessel segmentation and vessel-type separation are challenging due to the complexity of cortical vessel characteristics and low spatial signal-to-noise ratio. In this work, we presented an effective full-field method to differentiate arteries and veins in cerebral cortex using dual-modal optical imaging technology including laser speckle imaging (LSI) and optical intrinsic signals (OIS) imaging. The raw contrast images were acquired by LSI and processed with enhanced laser speckle contrast analysis (eLASCA) algorithm. The vascular pattern was extracted and segmented using region growing algorithm from the eLASCA-based LSI. Meanwhile, OIS images were acquired alternatively with 630 and 870 nm to obtain an oxyhemoglobin concentration map over cerebral cortex. Then the separation of arteries and veins was accomplished by Otsu threshold segmentation algorithm based on the OIS information and segmentation of LSI. Finally, the segmentation and separation performances were assessed using area overlap measure (AOM). The segmentation and separation of cerebral vessels in cortical optical imaging have great potential applications in full-field cerebral hemodynamics monitoring and pathological study of cerebral vascular diseases, as well as in clinical intraoperative monitoring.

The fundamental transverse mode (TEM00 T is preferable for experimental and theoretical study on the laser-induced retinal injury effect, for it can produce the minimal retinal image and establish the most strict laser safety standards. But actually lasers with higher order mode were frequently used in both earlier and recent studies. Generally higher order mode leads to larger retinal spot size and so higher damage threshold, but there are few quantitative analyses on this problem. In this paper, a four-surface schematic eye model is established for human and macaque. The propagation of 532-nm laser in schematic eye is analyzed by the ABCD law of Gaussian optics. It is shown that retinal spot size increases with laser transverse mode order. For relative lower mode order, the retinal spot diameter will not exceed the minimum laser-induced retinal lesion (25 ~ 30 μm in diameter), and so has little effect on retinal damage threshold. While for higher order mode, the larger retinal spot requires more energy to induce injury and so the damage threshold increases. When beam divergence is lowered, the retinal spot size decreases correspondingly, so the effect of mode order can be compensated. The retinal spot size of macaque is slightly smaller than that of human and the ratio between them is independent of mode order. We conclude that the laser mode order has significant influence on retinal spot size but limited influence on the retinal injury effect.

In the present paper, we describe the first complex multifocal noninvasive morphological and functional study that enabled us to define specific qualitative and quantitative features of neonatal skin. A complex morphofunctional examination of 10 infants aging from 1 to 28 days was performed by optical coherence tomography (OCT) device with a flexible probe at the wavelength of 920 nm with longitudinal resolution of 20 μm and transverse resolution of 25 μm with simultaneous measurement of skin functional parameters. The OCT images of neonatal thin skin have organized layered structure with four horizontally oriented layers. Thick skin of newborns has no structure typical for adult skin and no clear transition from the papillary to the cellular dermis. Thus, we show for the first time to our knowledge that neonatal thick skin differs structurally and functionally from adult skin. Structurally, it differs by a loose arrangement of stratum corneum squamae and thinner epidermis and papillary layer of dermis. The functional differences are lower transepidermal water loss, localization-dependent humidity, higher erythema level, and lower pigmentation. The principal structural differences between neonatal and adult skin show that skin structure formation is not completed by the moment of birth.

Fluorescence molecular tomography (FMT) is a fast-developing optical imaging modality that has great potential in early diagnosis of disease and drugs development. However, reconstruction algorithms have to address a highly ill-posed problem to fulfill 3D reconstruction in FMT. In this contribution, we propose an efficient iterative algorithm to solve the large-scale reconstruction problem, in which the sparsity of fluorescent targets is taken as useful a priori information in designing the reconstruction algorithm. In the implementation, a fast sparse approximation scheme combined with a stage-wise learning strategy enable the algorithm to deal with the ill-posed inverse problem at reduced computational costs. We validate the proposed fast iterative method with numerical simulation on a digital mouse model. Experimental results demonstrate that our method is robust for different finite element meshes and different Poisson noise levels.

The contrast mechanism of different polarization imaging techniques for melanoma in mouse skin is studied using both experiments and Monte Carlo simulations. Total intensity, linear polarization difference imaging (DPI), degree of polarization imaging (DOPI) and rotating linear polarization imaging (RLPI) are applied and the relative contrasts of these polarization imaging methods between the normal and cancerous tissues are compared. A two-layer absorption-scattering model is proposed to explain the contrast mechanism of the polarization imaging for melanoma. By taking into account of both scattering of symmetrical and asymmetrical scatterers and absorption of inter-scatterer medium, the two-layer model reproduces the relative contrasts for polarization images observed in experiments. The simulation results also show that, the parameters of polarization imaging change more dramatically with the variation of absorption in the bottom layer than the top layer.

A multi-GPU system designed for high-speed, real-time signal processing of optical coherence tomography (OCT) is described herein. For the OCT data sampled in linear wave numbers, the maximum processing rates reached 2.95 MHz for 1024-OCT and 1.96 MHz for 2048-OCT. Data sampled using linear wavelengths were re-sampled using a time-domain interpolation method and zero-padding interpolation method to improve image quality. The maximum processing rates for 1024-OCT reached 2.16MHz for the time-domain method and 1.26MHz for the zero-padding method. The maximum processing rates for 2048-OCT reached 1.58 MHz, and 0.68MHz, respectively. This method is capable of high-speed, real-time processing for OCT systems.

Accepted 15 November 2013 Published 2 January 2014 While the laser speckle imaging (LSI) is a powerful tool for multiple biomedical applications, such as monitoring of the blood flow, in many cases it can provide additional information when combined with spatio-temporal rhythm analysis. We demonstrate the application of Graphics Processing Units (GPU)-based rhythm analysis for the post processing of LSI data, discuss the relevant structure of GPU-based computations, test the proposed technique on surrogate 3D data, and apply this approach to kidney blood flow autoregulation. Experiments with surrogate data demonstrate the ability of the method to extract information about oscillation patterns from noisy data, as well as to detect the moving source of the rhythm. The analysis of kidney data allow us to detect and to localize the dynamics arising from autoregulation processes at the level of individual nephrons (tubuloglomerular feedback (TGF) rhythm), as well as to distinguish between the TGF-active and the TGF-silent zones.

Au–Ft, as a green synthesized nanoparticle, is composed of a ferritin nanocage enclosing a pair of Au nanoclusters inside. Our previous study has demonstrated that Au–Ft can be an excellent fluorescent probe for whole body imaging of mice with kidney specific targeting. But, the accurate localization of Au–Ft in kidney is still absent. In the current study, we detected and assessed the cellular and subcellular localization of Au–Ft in renal cortex and medulla of nu/nu mice after tail vein injection by using Nuance optical system (CRi, Woburn, USA) and inForm intelligent image analysis software based on single cell segmentation. We obtained the fluorescence intensity and cellular location of kidney-targeting Au–Ft probe in particular cell of renal glomerulus or renal tubules, which provided valuable proofs to clarify the mechanism of Au–Ft selective enrichment in kidney and the associated metabolic processes.

Treatment of malignant brain tumors continues to challenge scientists and clinicians alike. Location of these tumors within the central nervous system (CNS), which is considered a \privileged" organ, can prevent the penetration of chemotherapeutic agents through the blood– brain barrier (BBB). To overcome this limitation, nanoparticles are taken up and transported by macrophage and then delivered directly into the CNS. In this study, we used macrophage to uptake the folate-targeted bifunctional micelles loaded with near-infrared (NIR) dye ICG-Der-01 and investigate the dynamic bio-distributions of macrophage after intravenous injection into tumor-bearing mice. In vitro cellular experiments by confocal microscopy indicated that the uptake of micelles in macrophage was greatly enhanced due to the folate receptor overexpression. Dynamic bio-distributions of macrophage showed a rapid clearing rate through the liver intestine pathway. In conclusion, macrophage could potentially be used as nanoparticle drug carriers and require further investigation.

This research presents the results of investigation of laser polarization fluorescence of biological layers (histological sections, cytological smears) in the task of diagnostics and differentiation of early stages of cancer: Dysplasia — cervical microinvasive carcinoma of cervix uteri. The analytical conditions of polarization-optimal probing of biological layers were determined basing on the model of linear birefringence and dichroism of birefringent (fibrillar, porphyrin) networks. The technique of polarization-variable laser autofluorescence was developed and experimentally tested. The objective criteria (statistical moments) of differentiation of histological sections autofluorescent images of endometrium biopsy and cytological smears of it mucous coat were defined. The operational characteristics (sensitivity, specificity, accuracy) of this technique were determined concerning the positions of probative medicine, and clinical efficiency.

Accepted 6 December 2013 Published 5 February 2014 This work presents the use of extended Modified Lambert Beer (MLB) model for accurate and continuous monitoring of percent blood carboxyhemoglobin (COHb) (SCO) and oxyhemoglobin (OxyHb) saturation (SO₂) via a fitting procedure. This quantification technique is based on the absorption characteristics of hemoglobin derivatives in the wavelength range of 520–600 nm to give the best estimates of the required parameters. A comparison of the performance of the developed model and MLB law is made using attenuation data from Monte Carlo simulations for a two-layered skin model. The results revealed a lower mean absolute error of 0:4% in the values estimated by the developed model as compared to 10% that is given by the MLB law. This study showed that the discussed approach is able to provide consistent and accurate measurement of blood SO₂ and SCO across different skin pigmentations suggesting that it may potentially be used as an alternative means for clinical diagnosis of carbon monoxide (CO) poisoning.

Molecules such as water, proteins and lipids that are contained in biological tissue absorb midinfrared (MIR) light, which allows such light to be used in laser surgical treatment. Esters, amides and water exhibit strong absorption bands in the 5–7 μm wavelength range, but at present there are no lasers in clinical use that can emit in this range. Therefore, the present study focused on the quantum cascade laser (QCL), which is a new type of semiconductor laser that can emit at MIR wavelengths and has recently achieved high output power. A high-power QCL with a peak wavelength of 5.7 μm was evaluated for use as a laser scalpel for ablating biological soft tissue. The interaction of the laser beam with chicken breast tissue was compared to a conventional CO₂ laser, based on surface and cross-sectional images. The QCL was found to have sufficient power to ablate soft tissue, and its coagulation, carbonization and ablation effects were similar to those for the CO₂ laser. The QCL also induced comparable photothermal effects because it acted as a pseudo-continuous wave laser due to its low peak power. A QCL can therefore be used as an effective laser scalpel, and also offers the possibility of less invasive treatment by targeting specific absorption bands in the MIR region.