Fluorescence polarization is related to the dipole orientation of chromophores, making fluorescence polarization microscopy possible to reveal structures and functions of tagged cellular organelles and biological macromolecules. Several recent super resolution techniques have been applied to fluorescence polarization microscopy, achieving dipole measurement at nanoscale. In this review, we summarize both diffraction limited and super resolution fluorescence polarization microscopy techniques, as well as their applications in biological imaging.

Fluorescence lifetime imaging (FLIM) is an effective noninvasive bioanalytical tool based on measuring fluorescent lifetime of fluorophores. A growing number of FLIM studies utilizes genetically engineered fluorescent proteins targeted to specific subcellular structures to probe local molecular environment, which opens new directions in cell science. This paper highlights the unconventional applications of FLIM for studies of molecular processes in diverse organelles of live cultured cells.

Leeches and earthworms are the main ingredients of Shuxuetong injection compositions, which are natural biomedicines. Near infrared (NIR) diffuse reflection spectroscopy has been used for quality assurance of Chinese medicines. In the present work, NIR spectroscopy was proposed as a rapid and nondestructive technique to assess the moisture content (MC), soluble solid content (SSC) and hypoxanthine content (HXC) of leeches and earthworms. This study goal was to improve NIR models for accurate quality control of leech and earthworm using outlier multiple diagnoses (OMD). OMD was composed of four outlier detection methods: spectrum outlier diagnostic (MD), leverage diagnostic (LD), principal component scores diagnostic (PCSD) and factor loading diagnostic (FLD). Conventional outlier diagnoses (MD, LD) and OMD were compared, and the best NIR models were those based on OMD. The correlation coe±cients (R) for leech were 0.9779, 0.9616 and 0.9406 for MC, SSC and HXC, respectively. The values of relative standard error of prediction (RSEP) for leech were 2.3%, 5.1% and 9.0% for MC, SSC and HXC, respectively. The values of R for earthworm were 0.9478, 0.9991 and 0.9605 for MC, SSC and HXC, respectively. The values of RSEP for earthworm were 8.8%, 2.4% and 12% for MC, SSC and HXC, respectively. The performance of the NIR models was certainly improved by OMD.

Recent studies have suggested a link between executive function (EF) and obesity. Studies often adopt body mass index (BMI), which reflects the distribution of subcutaneous fat, as the sole marker of obesity; however, BMI is inappropriate to distinguish central obesity, which indicates the centralized distribution of visceral fat. Visceral fat compared with subcutaneous fat represents greater relative lipid turnover and may increase the risk of cognitive decline in older adults. However, the relationship between EF and central obesity is largely unknown, particularly in young adults. Therefore, we used waist circumference (WC) as a marker of central obesity and investigated different sensitivities between BMI and WC in the brain function. A total of 26 healthy young adults (aged 18 25 years; 42% female) underwent functional near-infrared spectroscopy assessments. EF was assessed using the Stroop task, which is a classical measurement of EF. A significant Stroop effect was observed in the behavioral and hemodynamic data. In addition, we observed that behavioral interference on the Stroop task varied much more in subjects with higher BMI and WC than those subjects with lower. Elevated BMI and WC were associated with a decreased hemodynamic response during the Stroop task specifically in the prefrontal cortex (PFC). Compared to BMI, WC was more closely connected with inhibitory control and revealed right lateralized PFC activation. Our findings suggest that WC is a reliable indicator of brain function in young adults and propose a relationship between EF and central obesity.

Interstitial laser immunotherapy (ILIT) is designed to use photothermal and immunological interactions for treatment of metastatic cancers. The photothermal effect is crucial in inducing anti-tumor immune responses in the host. Tissue temperature and tissue optical properties are important factors in this process. In this study, a device combining interstitial photoacoustic (PA) technique and interstitial laser photothermal interaction is proposed. Together with computational simulation, this device was designed to determine temperature distributions and tissue optical properties during laser treatment. Experiments were performed using ex-vivo porcine liver tissue. Our results demonstrated that interstitial PA signal amplitude was linearly dependent on tissue temperature in the temperature ranges of 20 600C, as well as 65 800C, with a different slope, due to the change of tissue optical properties. Using the directly measured temperature in the tissue around the interstitial optical fiber diffusion tip for calibration, the theoretical temperature distribution predicted by the bioheat equation was used to extract optical properties of tissue. Finally, the three-dimensional temperature distribution was simulated to guide tumor destruction and immunological stimulation. Thus, this novel device and method could be used for monitoring and controlling ILIT for cancer treatment.

Alzheimer's disease (AD) is a chronic neurodegenerative disease. The symptoms include memory and spatial learning di±culties, language disorders, and loss of motivation, which get worse over time, eventually ending in death. No effective treatments are available for AD, currently. Current treatments only attenuate symptoms temporarily and are associated with severe side effects. Near infra-red (NIR) light has been studied for a long time. We investigated the effect of NIR on AD using a transgenic mouse model, which was obtained by co-injecting two vectors carrying AD mutations in amyloid precursor protein (APP) and presenilin-1 (PSEN1) into C57BL/6J mice. The irradiation equipment consisted of an accommodating box and an LED array. The wavelength of NIR light emitted from LED was between 1040 nm and 1090 nm. The power density delivered at the level of the mice was approximately 15mW/cm2. Firstly, we treated the mice with NIR for 40 days. Then, the irradiation was suspended for 28 days. Finally, another 15 days treatment was brought to mice. We conducted Morris water maze and immunofluorescence analysis to evaluate the effects of treatment. Immunofluorescence analysis was based on measuring the quantity of plaques in mouse brain slices. Our results show that NIR light improves memory and spatial learning ability and reduces plaques moderately. NIR light represents a potential treatment for AD.

The evaluation of the microcirculatory bed functional state and the identification of angiospastic disorders with related complications, when the pathological changes are reversible, have an important role in medical practice. The aim of this study was to evaluate the possibility of using optical noninvasive methods and the cold pressor test to solve this problem. A total of 33 patients with rheumatological diseases and 32 healthy volunteers were included in the study. Laser Doppler flowmetry, tissue reflectance oximetry and pulse oximetry were used as optical noninvasive methods. The parameters were recorded before, immediately after and 20 min after the cold pressor test. Based on the measured parameters, the complex parameters of the microcirculatory bed were calculated. A detailed statistical analysis of the parameter changes for each individual in the two groups displayed diverse microcirculatory bed parameter responses upon cold exposure, with differing recovery of parameters after CPT. New diagnostic criteria were proposed for the identification of angiospastic disorders. According to the proposed criteria, 27 people of the volunteers group were confirmed to not display any disorders. In the patient group, however, 18 people were observed to have a relatively normal functional state of the microcirculatory bed, while 15 people were observed to have a possible tendency to angiospasm. To highlight the differences between a relatively normal state and presence of angiospastic disorders, statistical analysis of experimental data was carried out, which revealed significant differences. Further analysis of data with angiospastic disorders identified a relationship between their diagnoses and the results of laboratory studies. Thus, the evaluation of combined noninvasive optical diagnostic method use, the cold pressor test and proposed diagnostic criteria showed a positive result. This approach can be used to detect the presence of possible angiospastic disorders and related complications, as well as microcirculatory bed disorders against the background of other diseases.

Monte Carlo simulation of light propagation in turbid medium has been studied for years. A number of software packages have been developed to handle with such issue. However, it is hard to compare these simulation packages, especially for tissues with complex heterogeneous structures. Here, we first designed a group of mesh datasets generated by Iso2Mesh software, and used them to cross-validate the accuracy and to evaluate the performance of four Monte Carlobased simulation packages, including Monte Carlo model of steady-state light transport in multilayered tissues (MCML), tetrahedron-based inhomogeneous Monte Carlo optical simulator (TIMOS), Molecular Optical Simulation Environment (MOSE), and Mesh-based Monte Carlo (MMC). The performance of each package was evaluated based on the designed mesh datasets. The merits and demerits of each package were also discussed. Comparative results showed that the TIMOS package provided the best performance, which proved to be a reliable, e±cient, and stable MC simulation package for users.

Reactive oxygen species (ROS) play a vital role in cell signaling and redox regulation, but when present in excess, lead to numerous pathologies. Detailed quantitative characterization of mitochondrial superoxide anion (O;-2 production in fetal pulmonary artery endothelia cells (PAECs) has never been reported. The aim of this study is to assess mitochondrial O;-2 production in cultured PAECs over time using a novel quantitative optical approach. The rate, the sources, and the dynamics of O;-2 production were assessed using targeted metabolic modulators of the mitochondrial electron transport chain (ETC) complexes, specifically an uncoupler and inhibitors of the various ETC complexes, and inhibitors of extra-mitochondrial sources of O;-2. After stabilization, the cells were loaded with nanomolar mitochondrial-targeted hydroethidine (Mito-HE, MitoSOX) online during the experiment without washout of the residual dye. Timelapse fluorescence microscopy was used to monitor the dynamic changes in O;-2 fluorescence intensity over time in PAECs. The transient behaviors of the fluorescence time course showed exponential increases in the rate of O;-2 production in the presence of the ETC uncoupler or inhibitors. The most dramatic and the fastest increase in O;-2 production was observed when the cells were treated with the uncoupling agent, PCP. We also showed that only the complex IV inhibitor, KCN, attenuated the marked surge in O;-2 production induced by PCP. The results showed that mitochondrial respiratory complexes I, III and IV are sources of O;-2 production in PAECs, and a new observation that ROS production during uncoupling of mitochondrial respiration is mediated in part via complex IV. This novel method can be applied in other studies that examine ROS production under stress condition and during ROS-mediated injuries in vitro.

Fluorescence lifetime is not only associated with the molecular structure of fluorophores, but also strongly depends on the environment around them, which allows fluorescence lifetime imaging microscopy (FLIM) to be used as a tool for precise measurement of the cell or tissue microenvironment. This review introduces the basic principle of fluorescence lifetime imaging technology and its application in clinical medicine, including research and diagnosis of diseases in skin, brain, eyes, mouth, bone, blood vessels and cavity organs, and drug evaluation. As a noninvasive, nontoxic and nonionizing radiation technique, FLIM demonstrates excellent performance with high sensitivity and specificity, which allows to determine precise position of the lesion and, thus, has good potential for application in biomedical research and clinical diagnosis.

Purpose: The aim of this paper was to examine the distribution of macular, retinal nerve fiber layer (RNFL) thickness and optic disc parameters of myopic and hyperopic eyes in comparison with emmetropic control eyes and to investigate their variation according to axial length (AL) and spherical equivalent (SE) in healthy children. Methods: This study included 293 pairs of eyes of 293 children (145 boys and 148 girls), ranging in age from 6 to 17 years. Subjects were divided according to SE in control (emmetropia, 99 children), myopia (100 children) and hyperopia (94 children) groups and according to axial AL in 68 short (<22.00mm, 68), medium (from >=22.00mm to 25.00mm, 189) and long eyes (>25.00mm, 36). Macular parameters, RNFL thickness and optic disc morphology were assessed by the CirrusTM HD-OCT. AL was measured using the IOL-Master system. Littmann's formula was used for calculating the corrected AL-related ocular magnification. Results: Mean age (土SD) was 10.84土3.05 years; mean (±SD) SE was +0.14±0.51 D (range from 8.75 to +8.25 D) and mean AL (±SD) was 23.12±1.49. Average RNFL thickness, average macular thickness and macular volume decreased as AL and myopia increased. No correlations between AL/SE and optic disc parameters were found after correcting for magnification effect. Conclusions: AL and refractive error affect measurements of macular and RNFL thickness in healthy children. To make a correct interpretation of OCT measurements, ocular magnification effect should be taken into account by clinicians or OCT manufacturers.

Traditionally, optical microscopy is used to visualize the morphological features of pathogenic bacteria, of which the features are further used for the detection and identification of the bacteria. However, due to the resolution limitation of conventional optical microscopy as well as the lack of standard pattern library for bacteria identification, the effectiveness of this optical microscopybased method is limited. Here, we reported a pilot study on a combined use of Structured Illumination Microscopy (SIM) with machine learning for rapid bacteria identification. After applying machine learning to the SIM image datasets from three model bacteria (including Escherichia coli, Mycobacterium smegmatis, and Pseudomonas aeruginosa), we obtained a classification accuracy of up to 98%. This study points out a promising possibility for rapid bacterial identification by morphological features.