The microfluidic system for studies of carcinoma and normal cells interactions after photodynamic therapy (PDT) procedures Biomicrofluidics 5, 041101 (2011) Drug injection into fat tissue with a laser based microjet injector J. Appl. Phys. 109, 093105 (2011) A near infrared instrument to monitor relative hemoglobin concentrations of human bone tissue in vitro and in vivo Rev. Sci. Instrum. 81, 043111 (2010) Mechanism of oxidative stress generation in cells by localized near-infrared femtosecond laser excitation Appl. Phys. Lett. 95, 233702 (2009) Probing nanoantenna-directed photothermal destruction of tumors using noninvasive laser irradiation Appl. Phys. Lett. 95, 233701 (2009) Additional information on J. Appl. Phys. The efficacy of photodynamic therapy ͑PDT͒ depends on a variety of parameters: concentration of the photosensitizer at the time of treatment, light wavelength, fluence, fluence rate, availability of oxygen within the illuminated volume, and light distribution in the tissue. Dosimetry in PDT requires the congregation of adequate amounts of light, drug, and tissue oxygen. The adequate dosimetry should be able to predict the extension of the tissue damage. Photosensitizer photobleaching rate depends on the availability of molecular oxygen in the tissue. Based on photosensitizers photobleaching models, high photobleaching has to be associated with high production of singlet oxygen and therefore with higher photodynamic action, resulting in a greater depth of necrosis. The purpose of this work is to show a possible correlation between depth of necrosis and the in vivo photosensitizer ͑in this case, Photogem®͒ photodegradation during PDT. Such correlation allows possibilities for the development of a real time evaluation of the photodynamic action during PDT application. Experiments were performed in a range of fluence ͑0 -450 J / cm 2 ͒ at a constant fluence rate of 250 mW/ cm 2 and applying different illumination times ͑0-1800 s͒ to achieve the desired fluence. A quantity was defined ͑ ͒ as the product of fluorescence ratio ͑related to the photosensitizer degradation at the surface͒ and the observed depth of necrosis. The correlation between depth of necrosis and surface fluorescence signal is expressed in and could allow, in principle, a noninvasive monitoring of PDT effects during treatment. High degree of correlation is observed and a simple mathematical model to justify the results is presented.

Photonic crystals are some of the more spectacular realizations that periodic arrays can change the behavior of electromagnetic waves. In nature, so-called structural colors appear in insects and even plants. Some species create beautiful color patterns as part of biological behavior such as reproduction or defense mechanisms as a form of biomimetics. The interaction between light and matter occurs at the surface, producing diffraction, interference and reflectance, and light transmission is possible under suitable conditions. In particular, there are two Colombian butterflies, Morpho cypris and Greta oto, that exhibit iridescence phenomena on their wings, and in this work, we relate these phenomena to the photonic effect. The experimental and theoretical approaches of the optical response visible region were studied to understand the underlying mechanism behind the light-matter interaction on the wings of these Colombian butterflies. Our results can guide the design of novel devices that use iridescence as angular filters or even for cosmetic purposes. Nature is colored and attracts our attention due to its beauty and complex colors. Colors can be produced by pigmentation or by the arrangement of nanostructures. Recent studies showed that some species use this latter option to create beautiful color patterns as part of biological behavior such as reproduction or defense mechanisms as a form of mimicry 1-8 , and these tools have been perfected over millions of years in nature. In all cases, the interaction between light and matter occurs at the surface, producing diffraction, interference and reflectance phenomena. Additionally, light transmission is possible under suitable conditions. In the last decade, another optical phenomenon that has generated great interest among researchers is iridescence, which is related to the angular dependence of the observed color; there are many biological species and minerals that have this feature 9-11. In particular, there are two Colombian butterflies, Morpho cypris and Greta oto, that exhibit an iridescent effect on their wings. Iridescence has many feasible applications 12 , and a key advantage of structural colors over pigmented colors is the more intense coloration, especially under high light conditions. However, the physical interpretation of this phenomenon remains unclear and deserves more study. Iridescence is an effect that takes place in the visible spectrum 13,14 ; thus, the interaction of light with the surfaces of these systems implies the existence of nanostructures with sizes comparable to the wavelength in the visible region. On the other hand, there are man-made structures that exhibit iridescent effects, such as TiO 2 traces 15-17 , but total control over this property in man-made systems is not yet available. In this way, comprehension of the proper working conditions when light interacts with a butterfly's wings is a very important step toward man-made systems that will use this property. The Morpho cypris and Greta oto butterfly samples were provided, wit...

Photodynamic therapy (PDT) is a treatment modality that can be indicated for several cancer types and precancer lesions. One of the main applications of PDT is the treatment of superficial skin lesions such as basal cell carcinoma, Bowen's disease and actinic keratosis. Three elements are necessary in PDT, a photosensitizer (PS); light at specific wavelength to be absorbed by the PS, and molecular oxygen. A typical PS used for skin lesion is protoporphyrin IX (PpIX), which is an intrinsic PS; its production is stimulated by a pro-drug, such as 5-aminolevulinic acid (ALA). Before starting a treatment, it is very important to follow up the PpIX production (to ensure that enough PS was produced prior to a PDT application) and, during a PDT session, to monitor its photodegradation (as it is evidence of the photodynamic effect taking place). The aim of this paper is to present a unique device, LINCE (MMOptics -São Carlos, Brazil), that brings together two probes that can, respectively, allow for fluorescence imaging and work as a light source for PDT treatment. The fluorescence probe of the system is optically based on 400 nm LED (light emitting diodes) arrays that allow observing the fluorescence emission over 450 nm. The PDT illumination probe options are constituted of 630 nm LED arrays for small areas and, for large areas, of both 630 nm and 450 nm LED arrays. Joining both functions at the same device makes PDT treatment simpler, properly monitorable and, hence, more clinically feasible. LINCE has been used in almost 1000 PDT treatments of superficial skin lesions in Brazil, with 88.4% of clearance of superficial BCC.

We present experimental evidence of the existence of cell variability in terms of threshold light dose for Hep G2 (liver cancer cells) cultured. Using a theoretical model to describe the effects caused by successive photodynamic therapy (PDT) sessions, and based on the consequences of a partial response we introduce the threshold dose distribution concept within a tumor. The experimental model consists in a stack of flasks, and simulates subsequent layers of a tissue exposed to PDT application. The result indicates that cells from the same culture could respond in different ways to similar PDT induceddamages. Moreover, the consequence is a partial killing of the cells submitted to PDT, and the death fraction decreased at each in vitro PDT session. To demonstrate the occurrence of cell population modification as a response to PDT, we constructed a simple theoretical model and assumed that the threshold dose distribution for a cell population of a tumor is represented by a modified Gaussian distribution.Microscopic image (100×) of a necrosis caused by PDT in a rat liver. The edge is the depth of necrosis

Along the past years, a national program to implement photodynamic therapy (PDT) for nonmelanoma skin cancer (NMSC) was performed over the Brazilian territory. Using a strategy involving companies, national bank, and medical partners, equipment, medication, and protocols were tested in a multicenter study. With results collected over 6 years, we could reach a great deal of advances concerning the use of PDT for skin cancer. We present the overall reached results of the program and discuss several aspects about it, including public politics of treatment. A discussion about advantages of this technique within conditions of health care is placed, comparing PDT with surgery, including an analysis about the implementation of PDT in countries in development as Brazil, considering not only technical but social aspects, as the distribution of medical doctor in the Brazilian territory. The program resulted in a huge dissemination of PDT in Brazil and many countries in Latin America, in a partnership among public politics, universities, companies, and hospitals and clinics and in the insertion of national technologies as option to treat NMSC. Consequence of the program is mainly the continuation of the use of PDT in Brazil and many countries in Latin America.

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Organ transplantations have an increasing medical relevance. It is becoming a regular procedure with an increase in individuals waiting for organs. The increase in the number of discarded organs is mostly due to the donor bacterial and/or viral infection. In this article, we are demonstrating the feasibility of reduction of the bacterial load in kidney model by using ultraviolet-C as a germicidal agent in circulating liquids. Using Staphylococcus aureus as a bacteria model, we were able to demonstrate that in less than 30 min of liquid circulation and associated to irradiation, the bacterial load of the perfusate Custodiol HTK, histidine-tryptophan-ketoglutarate (solution with 5 log CFU mL À1 ), was fully eliminated. A modeling approach was created to verify the possibility of bacterial load decrease, when an organ (here, a renal experimental model) is present in the circuit, releasing a varied rate of microorganisms over time, while the solution is irradiated. Finally, we use an ex vivo model with swine kidney, circulating in the preservation solution with a Lifeport Kidney Transporter machine, to demonstrate that we can contaminate the organ and then promote the elimination of the microbiological load. The results show the feasibility of the technique.