Continuous Light Source Research Articles

Development of a Self-Luminescent Living Bioreactor for Enhancing Photodynamic Therapy in Breast Cancer.

The penetration ability of visible light (<2 mm) and near-infrared (NIR) light (∼1 cm) remarkably impairs the therapeutic efficacy and clinical applications of photodynamic therapy (PDT). To address the limitation of light penetration depth, a novel self-luminescent bacterium, teLuc.FP-EcN, has been engineered through transfection of a fusion expression plasmid containing the luciferase gene teLuc and bright red fluorescent protein mScarlet-I into Escherichia coli Nissle 1917 (EcN). The engineered teLuc.FP-EcN can specifically target and colonize tumors without significant toxicity to the host. Acting as a continuous internal light source, teLuc.FP-EcN can activate the photosensitizer chlorin e6 (Ce6) to generate reactive oxygen species (ROS) and then effectively destroy tumor tissue from the inside. As a result, a significant reduction in tumor proliferation and extension of the overall survival in mouse tumor models has been observed. Furthermore, teLuc.FP-EcN-boosted PDT amplified its therapeutic effect by activating antitumor immune response, including the conversion of M2 macrophages into pro-inflammatory M1 macrophages, as well as an increase in the proportion of CD3+ T cells and a decrease in T-cell exhaustion. In conclusion, teLuc.FP-EcN can be used as an implantable light source for tumor phototherapy, which simultaneously possesses ROS generation and immune regulation.

Effect of 460 nm blue light PBM on human MeWo melanoma cells.

Photobiomodulation (PBM) using 460 nm blue light has been shown to have an inhibitory effect on skin cancer cells. In this study, we used a continuous LED light source with a wavelength of 460 nm and designed various combinations of power density (ranging from 6.4 to 25.6 mW) and dose (ranging from 0.96 to 30.72 J/cm2) to conduct treatment experiments on MeWo cells to investigate the effects of blue light on MeWo melanoma cells. We are focusing on cell viability, cytotoxicity, mitochondrial function, oxidative stress, and apoptosis. We found that blue light inhibits these melanoma cells through oxidative stress and DNA damage, and this inhibition intensifies at higher irradiance levels. Although the cells initially attempt to resist the stress induced by the treatment, they eventually undergo apoptosis over time. These findings contribute to understanding melanoma's molecular response to blue light PBM, lay the groundwork for future clinical applications.

Development of Laryngeal Stroboscopic Effect With Continuous Light Source

Background and Objectives Most laryngeal imaging modalities used continuous light source. However, videostroboscopy adopted the unique stroboscopic flashing light triggered externally and is consistent with fundamental voice frequencies. If laryngeal stroboscopic effect could be obtained in the field of continuous illumination, it woud be more compatible with conventional video. In this study, we established the mathematical algorithm for stroboscopic effect with continuous light and tried to determine the feasibility of laryngeal stroboscopic effect with conventional laryngoscopy using continuous light in the mechanical model.Materials and Method The mechanical model of fan motor system was used to validate to the present study. Rotational images of the fan motor were captured using conventional laryngoscope with continuous light source.Results On the basis of the mathematical model, the optimal ranges of the frequency for stroboscopic effect were expected as (multiples of sampling rate [S])±(S/5). In the fan motor model, the stroboscopic effects could be confirmed on the basis of the mathematical model using conventional videolaryngoscopy with continuous light source.Conclusion Laryngeal stroboscopic effect with continuous light source might be feasible. The stroboscopic effect with continuous light would be expected to provide greater compatibility to integrate with the other imaging modalities for the vocal folds.

Photodynamic therapy with redaporfin activated by pulsed laser light

SignificanceRedaporfin is a photosensitizer under clinical trials for head and neck cancer. In previous work, a continuous light source was used in several tumor models, either in vitro or in vivo. However, the use of pulsed light (PL) sources can bring advantages to photodynamic therapy, such as higher penetration depths. ApproachTo study the influence of the light source in the efficacy of redaporfin-PDT, balb/c mice were inoculated with subcutaneous CT26 tumors. Redaporfin was activated using a PL source at 750 nm, with a repetition rate of 20 Hz and an energy per pulse of 24 mJ/cm2. Illumination time ranged from 5 to 15 min. ResultsThe results show an acute inflammatory response followed by a fast shrinkage and necrosis of the tumors and no significant side effects. ConclusionsThe activation of redaporfin with PL leads to good response of the tumors and further studies are being held to optimize the treatment conditions.

Emergency Microscope Light Modification by External Source in Absence of Power Supply

Introduction: Microscope is an instrument for visualizing fine detail of an object so that observer can observe the object being examined in detail. The object of examination vary from cells (normal or pathologic), microorganism (such as parasite and bacterium), and even non biological part. There are several types of microscope, one of the oldest forms and still used today is the light microscope. A light microscope relied on continuous light source to operate. The most common source for today's microscopes is an incandescent tungsten-halogen bulb, which is solely electric dependent, positioned in a reflective housing that projects light through the collector lens and into the sub-stage condenser. Current situations sometimes require readiness for conducting microscopic examination anytime, anywhere. Unfortunately, problem occur if the electricity goes out, most people will not be able to continue their microscopic observations. This problem raises the question of what if in an emergency it is necessary to carry out a microscopic examination but unfortunately there is no power source. Below we propose emergency modification efforts so that the microscope can still be used even in conditions without a power source.&#x0D; Aims: to modify an electric light microscope in such a way that it can continue to be used in the absence of an electrical power source using external source of light.&#x0D; Discussion: Adding an external source of light is a brilliant approach in order to make the electric dependent light microscope still useable in emergency condition.&#x0D; Conclusion: it is possible to modify an electric light microscope in the condition of no electric source available and make it operable.

Re-entry Fiber Optic Current Sensor Based on Continuous Light Source

Re-entry Fiber Optic Current Sensor Based on Continuous Light Source

High Sensitivity Singlet Oxygen Luminescence Sensor Using Computational Spectroscopy and Solid-State Detector.

This paper presents a technique for high sensitivity measurement of singlet oxygen luminescence generated during photodynamic therapy (PDT) and ultraviolet (UV) irradiation on skin. The high measurement sensitivity is achieved by using a computational spectroscopy (CS) approach that provides improved photon detection efficiency compared to spectral filtering methodology. A solid-state InGaAs photodiode is used as the CS detector, which significantly reduces system cost and improves robustness compared to photomultiplier tubes. The spectral resolution enables high-accuracy determination and subtraction of photosensitizer fluorescence baseline without the need for time-gating. This allows for high sensitivity detection of singlet oxygen luminescence emission generated by continuous wave light sources, such as solar simulator sources and those commonly used in PDT clinics. The value of the technology is demonstrated during in vivo and ex vivo experiments that show the correlation of measured singlet oxygen with PDT treatment efficacy and the illumination intensity on the skin. These results demonstrate the potential use of the technology as a dosimeter to guide PDT treatment and as an analytical tool supporting the development of improved sunscreen products for skin cancer prevention.

Analyzing 3D fields of refractive index, emission and temperature in spray-flame nanoparticle synthesis via tomographic imaging using multi-simultaneous measurements (TIMes)

Turbulent spray flames issuing from the SpraySyn 2.0 burner were investigated in the present work by means of tomographic imaging using multi-simultaneous measurements (TIMes). This small-scale standard burner is designed to study flame-spray synthesis of tailored nanoparticle systems. The applied measurement technique combined background-oriented schlieren tomography, computed tomography of light emission and two-color tomographic salt emission thermometry to reveal single-shot and time-averaged 3D fields of refractive index (linked to temperature, pressure and species concentration), CH* chemiluminescence (flame front indicator), SrOH emission from synthesized trace amount of Sr(NO3)2 dissolved in the liquid precursor solution (marker of the hot spray-flame products), and temperature of the hot spray-flame products, respectively. The salt emission thermometry technique was extended to tomographic measurements for the first time. Its implementation was based on the voxel-wise intensity ratio of reconstructed thermally-excited SrOH signals at two different regions in the visible spectrum that was converted to temperature using a single calibration curve based on multi-line OH planar laser-induced fluorescence measurements. The cost-effective setup for TIMes was composed of 43 machine-vision cameras equipped with bandpass spectrum filters, an innovative continuous semi-circular background pattern and LED light sources. The combined reconstructed fields provided information on the 3D flame structure in detail, showing the interaction between the flame front and spray stream, and the hot temperature regions. Spray-flame features were quantitatively analyzed, namely temperature, height, width, 3D tilt angle, and spreading half-angle of the flame plume. The temperature measurements proved to be robust against variations in the fuel/oxidizer equivalence ratio for the four investigated operating conditions. The spray flame issuing from the SpraySyn 2.0 burner at the standard operating condition was more stable than that in the previous burner generation, although more asymmetric near the nozzle exit and tilted, which might still cause heterogeneity of the synthesized nanoparticle system.

Continuous wave light sources with various optical modulators for signal quality optical fiber systems enhancement

Abstract This study clarified the simulation study of the continuous wave light sources with various optical modulators for signal quality optical fiber systems enhancement. The lighted signal power spectrum is measured and tested with various optical modulators after fiber media system. Also the lighted base band modulated signal power value is demonstrated with different light modulators after fiber media system of the reach up to 10 km. The electrical modulated base band signal power value is clarified with various light modulators after receiver PIN system. Moreover, the electrical modulated signal base band power amplitude spectrum quality and data error system rate values are numerically clarified and measured with different light modulators after receiver PIN system. The electro-light modulators that are used namely amplitude, phase, frequency modulators and Mach–Zehnder modulator (MZM).

Electronic Preresonance Stimulated Raman Scattering Spectromicroscopy Using Multiple-Plate Continuum.

Stimulated Raman scattering (SRS) spectromicroscopy is a powerful technique that enables label-free detection of chemical bonds with high specificity. However, the low Raman cross section due to typical far-electronic resonance excitation seriously restricts the sensitivity and undermines its application to bio-imaging. To address this bottleneck, the electronic preresonance (EPR) SRS technique has been developed to enhance the Raman signals by shifting the excitation frequency toward the molecular absorption. A fundamental weakness of the previous demonstration is the lack of dual-wavelength tunability, making EPR-SRS only applicable to a limited number of species in the proof-of-concept experiment. Here, we demonstrate the EPR-SRS spectromicroscopy using a multiple-plate continuum (MPC) light source able to examine a single vibration mode with independently adjustable pump and Stokes wavelengths. In our experiments, the C═C vibration mode of Alexa 635 is interrogated by continuously scanning the pump-to-absorption frequency detuning throughout the entire EPR region enabled by MPC. The results exhibit 150-fold SRS signal enhancement and good agreement with the Albrecht A-term preresonance model. Signal enhancement is also observed in EPR-SRS images of the whole Drosophila brain stained with Alexa 635. With the improved sensitivity and potential to implement hyperspectral measurement, we envision that MPC-EPR-SRS spectromicroscopy can bring the Raman techniques closer to a routine in bio-imaging.

A Monte Carlo simulation for Moving Light Source in Intracavity PDT.

We developed a simulation method for modeling the light fluence delivery in intracavity Photodynamic Therapy (icav-PDT) for pleural lung cancer using a moving light source. Due to the large surface area of the pleural lung cavity, the light source needs to be moved to deliver a uniform dose around the entire cavity. While multiple fixed detectors are used for dosimetry at a few locations, an accurate simulation of light fluence and fluence rate is still needed for the rest of the cavity. We extended an existing Monte Carlo (MC) based light propagation solver to support moving light sources by densely sampling the continuous light source trajectory and assigning the proper number of photon packages launched along the way. The performance of Simphotek GPU CUDA-based implementation of the method - PEDSy-MC - has been demonstrated on a life-size lung-shaped phantom, custom printed for testing icav-PDT navigation system at the Perlman School of Medicine (PSM) - calculations completed under a minute (for some cases) and within minutes have been achieved. We demonstrate results within a 5% error of the analytic solution for multiple detectors in the phantom. PEDSy-MC is accompanied by a dose-cavity visualization tool that allows real-time inspection of dose values of the treated cavity in 2D and 3D, which will be expanded to ongoing clinical trials at PSM. PSM has developed a technology to measure 8-detectors in a pleural cavity phantom using Photofrin-mediated PDT that has been used during validation.

Evaluation of Vaporizing Diesel Spray with High-Speed Laser Absorption Scattering Technique for Measuring Vapor and Liquid Phase Concentration Distributions

The Conventional Laser Absorption Scattering (C-LAS) technique is used to measure the mixture concentration and visualize the vapor phase. The former is determined by the attenuation of visible and ultraviolet light whereas the latter is achieved via light absorption and scattering theory. The C-LAS uses the Nd: YAG pulsed laser and CCD cameras to provide one spray shot at a particular instance which requires time and effort. However, the temporal measurement of a single spray shot is not possible. To record the distribution of the whole vapor phase in an injection event and measure liquid and vapor concentrations inside the spray, a High-Speed Laser Absorption Scattering (HS-LAS) technique was developed. The HS-LAS consists of continuous diode light sources, high-speed video cameras, and an image intensifier for UV light, which can provide the temporal variation of a single-shot spray. In the experiment, a commercial seven-hole injector with a hole diameter of 0.123 mm allowing high injection pressure of up to 100 MPa was used to avoid the potential inconsistencies with a single-hole test injector. The diesel surrogate fuel which consists of 97.5% n-tridecane and 2.5% of volume-based 1-methylnaphthalene was used. The injection amount of 5.0 mg/hole was selected to investigate the structure and mixture formation process of the spray. The findings of the experiments show that this imaging approach is a promising diagnostic technique for concurrently obtaining quantitative information on the quantity of vapor and droplets in a fuel spray. Furthermore, the turbulent/vortex fluid dynamics’ temporal development/variation can be investigated.

Multi-photon polymerization using upconversion nanoparticles for tunable feature-size printing

Abstract The recent development of light-based 3D printing technologies has marked a turning point in additive manufacturing. Through photopolymerization, liquid resins can be solidified into complex objects. Usually, the polymerization is triggered by exciting a photoinitiator with ultraviolet (UV) or blue light. In two-photon printing (TPP), the excitation is done through the non-linear absorption of two photons; it enables printing 100-nm voxels but requires expensive femtosecond lasers which strongly limit their broad dissemination. Upconversion nanoparticles (UCNPs) have recently been proposed as an alternative to TPP for photopolymerization but using continuous-wave lasers. UCNPs convert near-infrared (NIR) into visible/UV light to initiate the polymerization locally as in TPP. Here we provide a study of this multi-photon mechanism and demonstrate how the non-linearity impacts the printing process. In particular, we report on the possibility of fine-tuning the size of the printed voxel by adjusting the NIR excitation intensity. Using gelatin-based hydrogel, we are able to vary the transverse voxel size from 1.3 to 2.8 μm and the axial size from 7.7 to 59 μm by adjusting the NIR power without changing the degree of polymerization. This work opens up new opportunities to construct 3D structures with micrometer feature size by direct laser writing with continuous wave inexpensive light sources.

Photostability Enhancement of Dual-Luminophore Pressure-Sensitive Paint by Adding Antioxidants

Antioxidants were applied to a dual-luminophore pressure-sensitive paint (PSP), and the effects on photodegradation caused by exposure to excitation light were studied. Three types of antioxidants that are commonly used for the photostability enhancement of polymers were added to a dual-luminophore PSP, and degradation rates and pressure/temperature sensitivities were investigated by coupon-based tests. One-hour-long aging tests were performed in a pressure chamber with a continuous excitation light source under dry air and argon atmospheres at 100 kPa and 20 °C. As a result of the aging tests, a singlet oxygen quencher type antioxidant was found to reduce the degradation rate by 91% when compared with the dual-luminophore PSP without antioxidants. This implies that singlet oxygen has a dominant role in the photodegradation mechanism of the dual-luminophore PSP.

The Effects of Glare on the Perception of Visual Motion as a Function of Age.

PurposeThe purpose of this study was to determine the impact of glare, that simulated the effects of oncoming vehicle headlights, and age on different aspects of motion perception in central and peripheral vision.MethodsTwenty younger (mean age = 25 years, range = 20–32 years) and 20 older (mean age = 70 years, range = 60–79 years) visually healthy adults completed four visual motion tasks. Stimuli were presented centrally and at 15 degrees horizontal eccentricity for 2 viewing conditions: glare (continuous, off-axis) versus no glare. Motion tasks included minimum Gabor contrast required to discriminate direction of motion, translational global motion coherence, minimum duration of a Gabor to determine direction of motion (2 different size Gabors to determine spatial surround suppression), and biological motion detection in noise. Intraocular straylight was also measured (C-Quant).ResultsOlder adults had increased intraocular straylight compared with younger adults (P < 0.001). There was no significant effect of glare on motion thresholds in either group for motion contrast (P = 0.47), translational global motion (P = 0.13), biological motion (P = 0.18), or spatial surround suppression of motion (P = 0.29). Older adults had elevated thresholds for motion contrast (P < 0.001), biological motion (P < 0.001), and differences in surround suppression of motion (P = 0.04), relative to the younger group, for both the glare and no-glare conditions.ConclusionsAlthough older adults had elevated thresholds for some motion perception tasks, glare from a continuous off-axis light source did not further elevate these thresholds either in central or peripheral vision.Translational RelevanceA glare source that simulated the effect of oncoming headlights, did not impact motion perception measures relevant to driving.

Spiral wave drift under optical feedback in cardiac tissue.

Spiral waves occur in various types of excitable media and their dynamics determine the spatial excitation patterns. An important type of spiral wave dynamics is drift, as it can control the position of a spiral wave or eliminate a spiral wave by forcing it to the boundary. In theoretical and experimental studies of the Belousov-Zhabotinsky reaction, it was shown that the most direct way to induce the controlled drift of spiral waves is by application of an external electric field. Mathematically such drift occurs due to the onset of additional gradient terms in the Laplacian operator describing excitable media. However, this approach does not work for cardiac excitable tissue, where an external electric field does not result in gradient terms. In this paper, we propose a method of how to induce a directed linear drift of spiral waves in cardiac tissue, which can be realized as an optical feedback control in tissue where photosensitive ion channels are expressed. We illustrate our method by using the FitzHugh-Nagumo model for cardiac tissue and the generic model of photosensitive ion channels. We show that our method works for continuous and discrete light sources and can effectively move spiral waves in cardiac tissue, or eliminate them by collisions with the boundary or with another spiral wave. We finally implement our method by using a biophysically motivated photosensitive ion channel model included to the Luo-Rudy model for cardiac cells and show that the proposed feedback control also induces directed linear drift of spiral waves in a wide range of light intensities.

Event-based imaging velocimetry applied to a cylinder wake flow in air

Event-based vision is a new upcoming field within the field of computer vision. Unlike conventional frame-based imaging, event-based vision (or dynamic vision sensing) asynchronously records binary signals of contrast changes at the pixel level with microsecond resolution. Event-based imaging of small particles illuminated by a laser or other continuous light source generates streaks of events in a space-time domain. From this data the particles’ position in both space and time can be inferred. The present work explores the possibilities of harnessing the potentials of event- based vision for fluid flow measurement with focus on two-dimensional, two-component velocity field estimation at particle image densities corresponding to that of conventional PIV. Three different motion detection schemes are implemented. Measurements of a cylinder wake flow demonstrate that EBIV provides time resolved velocity data that is suitable for the retrieval of flow statistics as well as spectral and modal analysis. The present work is an extension of the recently published Exp. Fluids article by the authors on event-based imaging velocimetry and provides further details on current limitations related to event-based imaging.

Triplet-Triplet Annihilation Photopolymerization for High-Resolution 3D Printing.

Two-photon polymerization (TPP) currently offers the highest resolution available in 3D printing (∼100 nm) but requires femtosecond laser pulses at very high peak intensity (∼1 TW/cm2). Here, we demonstrate 3D printing based on triplet-triplet-annihilation photopolymerization (TTAP), which achieves submicron resolution while using a continuous visible LED light source with comparatively low light intensity (∼10 W/cm2). TTAP enables submicrometer feature sizes with exposure times of ∼0.1 s/voxel without requiring a coherent or pulsed light source, opening the door to low-cost fabrication with submicron resolution. This approach enables 3D printing of a diverse array of designs with high resolution and is amenable to future parallelization efforts.

Past Forward: The Nobelist’s First Laser

When George Porter arrived at the University of Cambridge in 1945 as a Ph.D. student, he found the equipment remarkably primitive. Students had to build their own oscilloscopes! To conduct his research—detecting the short-lived molecules known as free radicals—Porter pieced together a setup that included a surplus army searchlight powered by a surplus diesel engine. After seeing flash lamps at a Siemens factory, he decided to modify his approach, replacing the continuous light source with short, intense pulses of light. With his flash photolysis technique, Porter was able to capture reactions lasting mere milliseconds. To study even faster reactions, though, he needed a faster light source, for which he’d have to wait. The ruby laser, invented in 1960, was the ideal solution. Porter used this one to record nanosecond-scale reactions. Flash photolysis is still used to study semiconductors, nanoparticles, and photosynthesis, among other things. For their work on high-speed, lightdriven chemical reactions, Porter; his Ph.D. adviser, Ronald G.W. Norrish; and Manfred Eigen shared the 1967 Nobel Prize in Chemistry.

Boosting Continuous-Wave Laser-Driven Nonlinear Photothermal White Light Generation by Nanoscale Porosity.

The irradiation of an optically absorptive medium by a continuous-wave (CW) near-infrared (NIR) laser can result in a spectral continuum emission covering both the visible and NIR regions, which is attractive for applications as continuum light sources in diverse fields. It is shown here that this NIR-laser-driven light emission can be effectively modulated with nanoscale architecture in the medium. By using porous silica as the model matrix and Yb3+ ions as the photothermally active centers, up to 100 folds increment in NIR-laser-induced emission intensity and dramatic decrease in threshold excitation density are demonstrated. It is observed that the emission intensity exhibits a strong nonlinear dependence on the power of the NIR excitation laser, featuring clear excitation power thresholds. Based on combined numerical simulation and spectral and temperature measurements, the improved broadband emission and photothermal nonlinearity are interpreted by enhanced optical energy localization around the laser spot that results in boosting the photon-to-photon conversion efficiency. The use of the nonlinear photothermal emission process as a broadband NIR light source, which could be exploited for applications including NIR spectroscopy, imaging, and sensing, is further demonstrated as a proof-of-concept.