This PDF file contains the front matter associated with SPIE Proceedings Volume 11940, including the Title Page, Copyright information, Table of Contents, and Conference Committee listings.

PDT dose is the product of the photosensitizer concentration and the light fluence in the target tissue. For improved dosimetry during plural photodynamic therapy (PDT), an eight-channel PDT dose dosimeter was developed to measure both the light fluence and the photosensitizer concentration simultaneously from eight different sites in the pleural cavity during PDT. An isotropic detector with bifurcated fibers was used for each channel to ensure detected light was split equally to the photodiode and spectrometer. The light fluence rate distribution is monitored using an IR navigation system. The navigation system allows 2D light fluence mapping throughout the whole pleural cavity rather than just the selected points. The fluorescence signal is normalized by the light fluence measured at treatment wavelength. We have shown that the absolute photosensitizer concentration can be obtained by applying optical properties correction and linear spectral fitting to the measured fluorescence data. The detection limit and the optical property correction factor of each channel were determined and validated using tissue-simulating phantoms with known varying concentration of Photofrin. Tissue optical properties are determined using an absorption spectroscopy probe immediately before PDT at the same sites. The combination of 8-channel PDT dosimeter system and IR navigation system, which can calculate light fluence rate in the pleural cavity in real-time, providing a mean to determine the distribution of PDT dose on the entire pleural cavity to investigate the heterogeneity of PDT dose on the pleural cavity.

Efficient site-specific delivery of systemic therapeutic drugs is crucial especially in oncology but has proved to be challenging. Drugs can be encapsulated into liposomes that offer improved therapeutic index and distribution of the drug. The release of the drug can be efficiently achieved by integrating light-sensitive component into liposomes and applying near-infrared light in a time- and site-specific manner. Modulight has designed a cloud-connected ML8500 automated biomedical illumination system to specifically study in vitro drug release. The design is flexible, allowing up to eight Modulight semiconductor lasers of different wavelengths to be installed in one system, as well as the capability to be configured for different well plates, depending on the application requirements. The system includes an enhanced environmental control unit to ensure that the samples are investigated in physiologically relevant conditions. This enables also mimicking pathological conditions since drug release by light can have very different efficacy in these special conditions. Here we present an important case study regarding the utilization of the ML8500 system to investigate light-activated indocyanine green based liposomes which have been previously demonstrated to have great potential as advanced drug delivery systems.

India has one of the highest rates of oral squamous cell carcinoma (OSCC) in the world, with an incidence of 15 per 100,000 and more than 70,000 deaths per year. The problem is exacerbated by lack of medical infrastructure and routine screening, especially in rural areas. This collaboration recently developed, and clinically validated, a low-cost, portable and easy-to-use platform for intraoral photodynamic therapy (PDT) specifically engineered for use in global health settings. Here, we explore the implementation of our low-cost PDT system in conjunction with a small, handheld smartphone-coupled, multichannel fluorescence and white-light oral cancer imaging probe, which was also developed for global health settings. Our study aimed to use this mobile intraoral imaging device for treatment guidance and monitoring PDT using 5-aminolevulinic acid (ALA)-induced protoporphyrin IX (PS; PpIX) fluorescence. A total of 12 patients with 14 lesions having moderately/well-differentiated micro-invasive OSCC lesions (<2 cm diameter, depth <5 mm) were systemically administered with three doses of 20mg/kg ALA (total 60mg/kg). Lesion site PpIX and auto fluorescence was analyzed before/after ALA administration, and again after light delivery (fractionated, total 100 J/cm² of 630nm red LED light). Quantification of relative PpIX fluorescence enables lesion area segmentation to improve guidance of light delivery and reports extent of photobleaching. These results indicate the utility of this approach for image-guided PDT and treatment monitoring while also laying groundwork for an integrated approach, combining cancer screening and treatment with the same hardware.

Pancreatic ductal adenocarcinoma (PDAC) is among the most lethal of human malignancies. PDAC is characterized by dense fibrous stroma which obstructs drug delivery and plays complex tumor-promoting roles through paracrine crosstalk. Photodynamic Therapy (PDT) is a light-based modality which has been demonstrated to be clinically feasible and effective for tumors of the pancreas. Here, we use in vitro heterocellular 3D co-culture models in conjunction with imaging, bulk rheology and microrheology methods to investigate the impact of verteporfin-based PDT on non-cellular (ECM) components of PDAC stroma. By measuring the rheology of ECM before and after PDT we find that softening of ECM is concomitant with an increase in transport of nanoparticles (NPs). At the same time, as shown previously, photodestruction of stromal fibroblasts, leads to enhanced tumor response to PDT. Collectively these results in 3D tumor models suggest that photodynamic stromal depletion (PSD) could be used to enhance subsequent drug delivery and improve tumor response to treatment.

In photothermal therapy, heat generated from absorbed light energy is used to treat cancerous tissue. Thus, determining laser parameters that control temperature elevation prior to therapy is crucial for an effective outcome. These parameters can be defined by modeling the expected temperature increase via numerical simulations. The quality of these simulations highly depends on the accurate knowledge of optical properties of the treated tissue. Multi-wavelength Photo Magnetic Imaging (PMI) utilizes four laser wavelengths from the near infrared (NIR) window to induce a relatively low temperature increase, while measuring the laser-induced temperature increase using Magnetic Resonance Thermometry. These measured temperature maps are then used by the PMI image reconstruction algorithm to provide high spatial resolution absorption maps at these wavelengths. These absorption maps are then processed to recover the concentration of the main chromophores of the tissue, and consequently obtain its total optical absorption spectrum at any wavelength in the NIR region based on the Beer-Lambert law. In this paper, PMI was used to recover the absorption coefficient of a gelatin tissuesimulating phantom at four wavelengths. These spatially-resolved absorption values were used to successfully recover the concentration of the chromophores of the phantom and calculate its total absorption spectrum in the NIR spectral window with an error as low as ∼ 2.3%. Therefore, applications of photothermal therapy applied in NIR window can benefit from the absorption spectrum recovered by PMI to achieve accurate simulations and determine important laser parameters, which are key for accurate therapy planning.

Photodynamic therapy (PDT) is an established modality for cancer treatment and reactive oxygen species explicit dosimetry (ROSED), based on direct measurements of in-vivo light fluence (rate), in-vivo photofrin concentration, and tissue oxygenation concentration, has been proved to be an effective dosimetric quantity which can be used to predict PDT outcome. In this study, ROSED was performed for photofrin-mediated PDT for mice bearing radiation-induced fibrosacorma (RIF) tumor. PDT treatments were performed using single or fractionated illumination to a same total fluence of 135 Jcm^-2. The effects of light fractionation on the total reacted [ROS]_rx and treatment outcomes were evaluated.

Photosensitizing agents play an essential role in deactivation process of multidrug resistant pathogens and tumor treatments. In this work, methylene blue (MB) functionalized silver nanoparticles (Ag NPs) are used as an effective photodynamic therapy (PDT) agent for deactivating different strains of bacteria. Ag NPs were synthesized by pulsed laser ablation technique in different aqueous solutions like polyvinylpyrrolidone (PVP), citrate and polyvinyl alcohol (PVA) at different wavelength and power. With 1064nm wavelength, Ag NPs average size distribution in citrate, PVP, and PVA were found to be 6nm, 10nm, and 12nm respectively. Further, when 532nm wavelength is used, the average size was found to be 4nm, 7nm, and 10nm respectively. The synthesized Ag NPs were characterized using a transmission electron microscopy (TEM), UV–vis, and photoluminescence (PL) spectra. These Ag NPs were combined with MB and used to deactivate the Gram-negative bacteria, Escherichia coli (E. coli), and Gram-positive bacteria, Staphylococcus aureus (S. aureus). MB and Ag NPs combination was found to possess higher antimicrobial activity in comparison to MB and Ag NPs alone. Within 6 min of irradiation time with 660 nm LED, the MB/Ag NPs deactivated entire ~10⁸ CFU/mL concentrated S. aureus and E. coli, bacteria. MB/Ag NPs used in PDT could be effective in killing bacterial pathogens in open wounds, prosthetic joint infections, in vivo cancer and tumor treatments.

This Monte Carlo (MC) simulation study provides an evaluation of dose uniformity in a patient and the difference between dose and Cherenkov distributions, which is invaluable in developing conversion factors to relate observed Cherenkov images to actual dose distributions for TSET patients. This MC simulations with TOPAS is performed using realistic patient geometries obtained with a 3D scanner during total skin electron treatments (TSET) at UPenn. For each treatment posture in the Stanford technique, the differences between Cherenkov photon distributions and dose distributions produced in MC are consistent with the differences observed between a Cherenkov imaging camera and in-vivo dose measurement with OSLD on patient skin. According to MC studies of a flat rectangular PVC board, the difference between Cherenkov and dose is mostly due to the spoiler. This is confirmed by observing consistent dose and Cherenkov distributions in clinical measurements on a PVC board without the spoiler. The accumulated dose and Cherenkov distributions for each patient are obtained by projecting the MC output of the 6 postures of the TSET treatment together onto a finite element model of the patient.

Homogeneous drug delivery to solid tumors is difficult to achieve because of biological barriers in the tumor and of its elevated interstitial fluid pressure. We investigated the distribution of a photosensitizer (redaporfin) in orthotopic 4T1 and subcutaneous CT26 tumors using photoacoustic tomography. Redaporfin has a distinct photoacoustic spectrum that allows for its localization and relative quantification. Whereas CT26 tumors uptake a large amount of redaporfin, 4T1 tumors have redaporfin mostly in their periphery. We exposed 4T1 tumors to high-intensity, broadband photoacoustic waves and show that the amount of redaporfin in 4T1 tumors increases after 5 minutes of exposure. Photoacoustic waves are a promising non-invasive method to increase drug delivery to solid tumors.

Photobiomodulation (PBM) therapy using red and near infrared light has been reported effective for reduction of pain, reduction of inflammation, wound healing, skin rejuvenation, hair growth, fat loss, slowing or stopping and even reversing progress of neurodegenerative diseases such as Alzheimer’s disease (AD) and Parkinson’s disease (PD). Most of the clinical trial results of PBM therapy have been reported effective depending on the light pulsing frequencies and wavelengths of light of PBM therapy devices. Many PBM therapy devices for personal and home use have been introduced for PBM therapy, but the optical and electrical parameters of the PBM devices have not been clearly specified, which makes it difficult and confused for users to select PBM devices suitable for their applications. In this paper, the most frequently used PBM therapy conditions including wavelengths, light pulsing frequencies, and applications of the PBM therapy devices in the clinical papers were analyzed.

Photobiomodulation therapy (PBMT) is a promising but poorly understood technique utilizing low irradiance LED or laser light to induce positive biological effects. Though the use of PBMT in clinical settings is increasingly accepted, the molecular mechanisms underlying these effects remain poorly characterized. The most commonly postulated mechanism is via light absorption at cytochrome c oxidase, also known as complex IV (C-IV) of the mitochondrial electron transport chain. It is hypothesized that light absorption at C-IV initiates a cascade of events subsequently resulting in increased ATP generation, and improved mitochondrial/cellular fitness. However, surprisingly little is known about the mechanisms by which these pathways are initiated, and how they establish the observed beneficial outcomes. Other work from our group has demonstrated that the kinetics of C-IV enzyme activity can be positively modulated by lowirradiance NIR laser exposure. However, the nature of those assays limits them to a single post-exposure measurement of one enzyme complex. To extend this observation we have developed a novel method allowing us to conduct real-time measurements of mitochondrial respiration while simultaneously applying low irradiance laser exposures consistent with those used in photobiomodulation. This technique utilized a polarographic oxygen sensor to make continuous in vitro measurements of oxygen consumption, before, during, and after laser irradiation. Using an integrated optical port, laser irradiation was applied to the sample accurately and reliably, allowing for precision dosimetry. This novel technique was then used to probe effects of light exposure at a number of wavelengths and irradiances on mitochondrial respiration.

Photobiomodulation (PBM) is the use of visible or near infrared (NIR) light to induce positive biological/therapeutic effects. It is generally believed that the chromophore for these effects is cytochrome c oxidase, a.k.a. complex IV (C-IV) of the mitochondrial electron transport chain. However, the mechanisms by which these pathways are initiated and how they establish observed beneficial outcomes are still unclear. We have found that C-IV enzyme kinetics can be enhanced by exposure to 808 nm NIR laser light. We used a spectrophotometric method to monitor C-IV activity, by observing changes in the redox state of the small electron carrier protein cytochrome c. By examining a range of irradiances and exposure times, we collected data from samples exposed to overlapping radiant exposures, but at different irradiances. If the mechanism by which NIR exposure enhances C-IV activity is a traditional photochemical reaction, it is expected to exhibit irradiance reciprocity, meaning the biological outcome of a photoreaction is dependent upon the radiant exposure to which the sample is exposed (e.g. the same bioeffect is observed if irradiance is halved and exposure duration is doubled). Surprisingly, this was not the case, and instead irradiance was found to be the exposure parameter best correlated with the degree of C-IV activity enhancement. This violation of irradiance reciprocity is strong evidence that NIR exposure does not rely on delivery of a particular number of photons. This implies either light acts on C-IV indirectly or there are other secondary processes at work, before an eventual enhancement of C-IV activity.

Resonance Raman (RR) spectroscopy is a well-established technique that has been used in a variety of different applications. Shown here is its ability to investigate the underlying mechanisms of photobiomodulation. Isolated mitochondria from porcine cardiac tissue was used as the sample, and its cytochrome c redox state was probed by the RR technique. By injecting a substrate, such as succinate, into the mitochondrial sample, cytochrome c becomes reduced until the succinate is consumed. Without new freeelectrons from succinate, a lack of Complex III activity allows all the molecules of cytochrome c to become re-oxidized. A measurement of this activity provides information that can be used to determine electron transport chain kinetics. Using this RR technique, changes in kinetics within isolated cardiac mitochondria were explored using low irradiance visible light. A novel result occurred when mitochondria were irradiated with higher irradiance 532 nm light (402 W/cm²) where it was found that the substrate was consumed at a quicker rate than with a comparatively lower irradiance light (170 W/cm²). It was also determined that the rate at which cytochrome c was reduced after the substrate was introduced was larger. This increase in electron transport chain kinetics was not due to temperature and was hypothesized to be a photochemical effect. It was also found that lower irradiances of 520 nm light (30 mW/cm²) did not have an effect on the kinetics, therefore a higher irradiance is needed when imaging isolated mitochondria using resonance Raman spectroscopy.

For many years, photobiomodulation in cancer patients has been used empirically, based on the positive clinical experience. When using PBM for the prevention and treatment of early radiation toxicity, exposure can occur directly in the area of the tumor site. For that reason, the data is need about a potential influence of low-intensity red light as on the normal as well on the tumor cells exposed to ionizing radiation. The aim of the work was to study the effects of photobiomodulation (PBM) in the red spectrum (640 nm) with fluences from 3 mJ/cm² to 2 J/cm² in combination with ionizing radiation at doses of 2–6 Gy against human BJ-5ta-hTERT cells – postnatal fibroblasts. The cells were exposed to low-intensity red light before or after their exposure to IR, the viability of the cells was determined by MTT-test 24 hours after the last exposure. The effects of PBM depend on the fluence of PBM, the dose of IR and the sequence of the actions of these physical factors on cells. The adaptive effect of PBM was observed only for high fluences – 1 and 2 J/cm² when exposed to PBM and subsequent irradiation of IR. At the same time, the stimulating effect of PBM was observed only for low fluences from 3 to 300 mJ/cm² under IR irradiation and subsequent (after 1 hour) exposure to PBM. These data should be taken into account when using PBM for the correction of adverse events of radiation therapy in a clinic.

Introduction: Photodynamic therapy (PDT) is a promising adjunctive treatment for high grade brain tumors. However, early clinical trials have utilized significant variations in the conditions of light delivery, including the type of fibre and diffusing fluid. Our goal of this study was to sweep these conditions to determine optimal parameters for light delivery to the tumor resection cavity using a 3D model. Method: A 3D model to mimic an intracranial cavity was created and a PDT device was assembled using multiple 2W output lasers connected to cylindrical diffusing fibres. A variety of light delivery conditions were tested, including the use of bare fibres versus fibres placed inside balloon catheters, with deionized water or intralipid solutions. India ink was utilized to mimic blood products in the resection cavity. Light intensity at the edge of the model, signifying incident intensity at the tissue surface, was measured in multiple axes to assess for strength and uniformity. Light intensity and uniformity were compared between groups using Kruskal-Wallis analysis of variance. Results: Light delivery was significantly higher with the bare fibre compared to the balloon catheter across all types of circulating fluid (34.2 ± 3.54 vs. 30.8 ± 1.31 mV/cm2, p<0.05), but less uniform. The light uniformity increased as the concentration of intralipid increased. In conditions with the addition of india ink, the bare fibre performed better than the balloon catheter. Conclusion: In this phantom model assessment, bare fibres with 0.1% or 0.5% intralipid solution led to improved light delivery compared to other parameters. Photodynamic therapy of the cavity following surgical resection of HGG should be performed with optimal light delivery parameters to ensure treatment efficacy.

Accurate dosimetry is crucial for the ongoing development and clinical study of photodynamic therapy (PDT). Current dosimetry standards range from less accurate methods involving measurement of only light fluence and photosensitizer concentration during treatment, to significantly improved methods such as singlet oxygen explicit dosimetry (SOED), a macroscopic model that includes an additional important parameter in its dosimetric calculations: ground-state oxygen concentration ([³O₂]). However, neither of these models is a method of direct dosimetry. Multispectral singlet oxygen luminescence dosimetry (MSOLD) shows promise in this regard but requires significant improvement in signal quality and remains to be validated in a clinical setting. In this study, we validate a linearly increasing MSOLD signal with an InGaAs photodiode detector for increasing concentration (0 mg/kg to 200 mg/kg) in tissue-simulating phantoms containing photofrin, calculating a calibration curve based on 1270 nm peak-intensity signal and area under the curve for backgroundsubtracted singlet oxygen emission. Additionally, we validate MSOLD against the current clinical dosimetry standard, SOED, through simultaneous measurement of SOED parameters and MSOLD signal for varying concentrations (50 μM – 500 μM). Finally, we investigate the effects of using very high gain amplification on InGaAs photodiode detectors to amplify the MSOLD signal for use in clinical models. We show that a calibration curve relating photosensitizer concentration (PS) and MSOLD signal can be established. Additionally, we demonstrate good correlation between MSOLD signal and SOED-calculated [1O2]rx. However, we show that when using high amplification on InGaAs photodiodes for long illumination times, the inherent instability in these detectors becomes apparent.

Recent advances in photodynamic inactivation and photobiomodulation require extensive research of application safety in living tissues in vitro and in vivo. Superficial phototoxicity induced cellular morphological changes have been observed and recorded with using confocal Brillouin microspectrometer. We are reporting evidence of biomechanical processes occurring in cells subjected to high-power laser radiation. 4T1 murine fibroblast cells were used in the study, making results easily after exposure to high power laser radiation. Spatial distribution of subcellular structures’ stiffness was recorded with high precision and analyzed, drawing correlation between existing morphological model and novel stiffness data within the cell.

Photodynamic therapy (PDT) is a promising treatment for colorectal cancer owing to its high selectivity and limited systemic side effects. However, the true potential of PDT for therapeutic applications against tumors hasn’t been realized partly due to the complexity of PDT regimen. In the present study, we examine the efficacy of different fluence rates of hematoporphyrin derivative (HpD)-mediated PDT to predict long-term control rates of murine CT26 colorectal cancer. We further show how variation in the expression of immune checkpoints in the response of HpD-PDT at different fluence rates. Tumor-bearing mice were injected with 5 mg/kg HpD and subjected 48 h later to an 80 J/cm² red light dose administered at fluence rates of 10, 50, and 100 mW/cm². The expression of immune checkpoints（PD-1, LAG-3, and TIM-3）on tumor-infiltrating lymphocytes was measured 10 days after PDT. Mice treated with fluence rates of 10 and 50 mW/cm² exhibited significantly longer survival than those treated at 100mW/cm². Immune checkpoints on tumor-infiltrating CD8⁺ T cells were upregulated following PDT. Tumors treated with fluence rate of 10 mW/cm² showed a significant increase of immune checkpoints on CD8⁺ T cells than those treated at 50 and 100 mW/cm². Low light fluence rate results in significant tumor control and immune checkpoints upregulation. Improved tumor control could be expected by reducing the rate and combining checkpoint inhibitors with PDT using low fluence rate. Our data establish a correlation between activation of immune checkpoint and fluence rate and show the potential to combine PDT with checkpoint inhibitors.