The optimal combination of wavelengths of light (spectral quality) for single leaf photosynthesis has been well characterized, but spectral quality is not well characterized in whole plants in long-term studies. Here we report the effects of eight light spectra at two photosynthetic photon fluxes (200 and 500 µmol m-2 s-1) on dry mass, leaf area index and net assimilation of seven species in replicate 21-day studies. The combination of treatments allowed us to separately assess the effects of blue and green light fraction among species and PPF. At a PPF of 500, increasing blue light from 11 to 28 % significantly decreased dry mass in tomato, cucumber, and pepper, but there was no significant effect on soybean, lettuce and wheat. At a PPF of 200, dry mass significantly decreased only in tomato across the blue light range. Effects on leaf area paralleled effects on dry mass in all species at both PPFs, indicating that the effects of blue light on dry mass were mediated by changes in leaf area. Contrary to predictions of net assimilation based on blue light response of single leaves, there was no evidence of decreasing net assimilation with increasing blue light. In contrast to the significant effect of blue light dry mass and leaf area, increasing green light fraction from zero to 30 % resulted in few significant differences. Contrary to several reports on significant green light effects on growth (both increases and decreases), we found no consistent effect of green light among species on growth, leaf area or net assimilation. Collectively, these results indicate significant differences among species in sensitivity to blue light and less sensitivity to green light, and that the effect of blue light on dry mass is primarily determined by changes in leaf area.

This thesis investigates the use of Raman tweezers microspectroscopy to interrogate the biochemistry of single biological cells. Raman tweezers microspectroscopy is a powerful technique, which combines traditional Raman microspectroscopy and optical trapping, allowing the manipulation and environmental isolation of a biological cell of interest whilst simultaneously probing its biochemistry gleaning a wealth of pertinent information. The studies carried out in this thesis can be split into two broad categories: firstly, the exploitation of Raman tweezers microspectroscopy to study biological cells and secondly developments to the Raman tweezers microspectroscopy technique that extend its capabilities and the range of samples that can be studied. In the application of Raman tweezers, the stacking and interrogation of multiple cells is reported allowing a rapid representative Raman signal to be recorded from a small cell population with improved signal to noise. Also demonstrated is the ability of Raman spectroscopy to identify and grade the development of Human Papillomavirus induced cervical neoplasia with sensitivities of up to 96 %. These studies demonstrate the potential of Raman spectroscopy to study biological cells but it was noted that the traditional Raman tweezers system struggled to manipulate large cells thus a decoupled Raman tweezers microspectroscopy system is presented where a dual beam fibre optical trap is used to perform the trapping function and a separate Raman probe is introduced to probe the biochemical nature of the trapped cell. This development allowed the trapping and examination of very large cells whilst opening up the possibility of creating Raman maps of trapped objects. Raman tweezers microspectroscopy could potentially become an important clinical diagnostic and biological monitoring tool but is held back by the long signal integration times required due to the weak nature of Raman scattering. The final study presented in this thesis examines the potential of wavelength modulated Raman spectroscopy to improve signal to noise ratios and reduce integration times. All these studies aim to demonstrate the potential and extend the performance of Raman tweezers microspectroscopy.

In this thesis, the development of a femtosecond Cr⁴⁺:forsterite solid-state laser is described where the mode-locking procedure was initiated using two novel saturable absorbers. One was a GaInNAs quantum-well device and the other a quantum-dot-based saturable absorber. These devices had not previously been exploited for the generation of femtosecond pulses from a solid-state laser but in the course of this project, successful mode-locked laser operation in the femtosecond domain was demonstrated for both devices. When the GaInNAs device was incorporated in the Cr⁴⁺:forsterite laser, transform-limited pulses with durations as short as 62fs were obtained. The performance of this femtosecond laser was significantly superior to that for previous quantum-well based saturable absorbers in the 1300nm spectral region. The dynamics of the device were investigated with the aim of refining subsequent devices and to explore the potential to grow future devices for use at longer wavelengths. At the outset of my research work quantum-dot based saturable absorbers had not be used for the mode locking of solid-state lasers in the femtosecond regime. The work presented in this thesis showed that quantum-dot structures could be exploited very effectively for this purpose. This was initially achieved with the quantum-dot element being inclined at an off-normal incidence within the cavity but experimental assessment together with further development of the device allowed for implementation at normal incidence. Reliable operation of the femtosecond laser was demonstrated very convincingly where transform-limited pulses of 160fs duration were generated. Having developed practical femtosecond Cr⁴⁺:forsterite lasers, the final part of the project research was directed towards exemplar applications for a laser operating in the 1300nm spectral region. These were biophotonics experiments in which assessments of both deep tissue penetration and two-photon chromosome cutting were undertaken. This work confirmed the suitability of the 1300nm laser radiation for propagation through substantial thicknesses of biological tissue (~15cm). The demonstration of highly localised two-photon cutting of Muntjac deer chromosomes also represented a novel result because single-photon absorption could be avoided effectively and the temporal broadening of the femtosecond pulses in the delivery optics arising from group velocity dispersion around 1300nm was minimal.

This study presents the first attempt to combine the fields of ultraviolet (UV) photobiology, plant cell wall biochemistry, aerobic methane production and reactive oxygen species (ROS) mechanisms to investigate the effect of UV radiation on vegetation foliage. Following reports of a 17% increase in decomposition rates in oak (Quercus robur) due to increased UV, which were later ascribed to changes in cell wall carbohydrate extractability, this study investigated the effects of decreased UV levels on ash (Fraxinus excelsior), a fast-growing deciduous tree species. A field experiment was set up in Surrey, UK, with ash seedlings growing under polytunnels made of plastics chosen for the selective transmission of either all UV wavelengths, UV-A only, or no UV. In a subsequent field decomposition experiment on end-of-season leaves, a significant increase of 10% in decomposition rate was found after one year due to removal of UV-B. However, no significant changes in cell wall composition were found, and a sequential extraction of carbohydrate with different extractants suggested no effects of the UV treatments on cell wall structure. Meanwhile, the first observations of aerobic production of methane from vegetation were reported. Pectin, a key cell wall polysaccharide, was identified as a putative source of methane, but no mechanism was suggested for this production. This study therefore tested the effect of UV irradiation on methane emissions from pectin. A linear response of methane emissions against UV irradiation was found. UV-irradiation of de-esterified pectin produced no methane, demonstrating esters (probably methyl esters) to be the source of the observed methane. Addition of ROS-scavengers significantly decreased emissions from pectin, while addition of ROS without UV produced large quantities of methane. Therefore, this study proposes that UV light is generating ROS which are then attacking methyl esters to create methane. The study also demonstrates that this mechanism has the potential to generate several types of methyl halides. These findings may have implications for the global methane budget. In an attempt to demonstrate ROS generation in vivo by UV irradiation, radio-labelling techniques were developed to detect the presence of oxo groups, a product of carbohydrate attack by ROS. Using NaB3H4, the polysaccharides of ash leaflets from the field experiment were radio-labelled, but did not show any significant decrease in oxo groups due to UV treatments. However, UV-irradiation of lettuce leaves showed a significant increase in radio-labelling, suggesting increased UV irradiation caused an increase in the production of ROS. The study shows that the use of this radio-labelling technique has the potential to detect changes in ROS production due to changes in UV levels and could be used to demonstrate a link between ROS levels and methane emissions.

Introdução: a incidência dos melanomas permanece em ascensão em diversos países. Os nevos melanocíticos podem ser seus precursores ou marcadores de risco. A radiação ultravioleta é o principal fator de risco ambiental para o seu desenvolvimento. Estudos com nevos irradiados mostram que a radiação ultravioleta B (UVB) pode causar alterações morfológicas e bioquímicas semelhantes às de um melanoma in situ. As metaloproteinases da matriz (MMP) são enzimas proteolíticas e, particularmente, as MMP-2 e –9 (gelatinases A e B) parecem estar associadas à invasão tumoral, à formação de metástases e de neoangiogênese em melanomas. O objetivo do presente estudo é avaliar os efeitos da UVB nas expressões imunoistoquímicas de MMP-2 e –9 nas diferentes linhagens celulares de nevos melanocíticos. Métodos: quarenta e dois nevos melanocíticos tiveram suas metades irradiadas com dose de 2 DEM (dose eritematosa mínima) de UVB e foram excisados uma semana após. As expressões imunoistoquímicas das MMP-2 e -9 foram comparadas, quanto à sua intensidade, por três avaliadores diferentes entre os lados irradiados e não irradiados em queratinócitos, melanócitos de epiderme e derme superior, células endoteliais e fibroblastos. Os dados foram analisados pelo teste t pareado para as diferenças de expressão e pelo ICC para avaliação da homogeneidade entre as respostas dos observadores. Resultados: com relação à expressão imunoistoquímica de MMP-2, todas as linhagens celulares mostraram aumento no lado irradiado, especialmente os melanócitos epidérmicos. Quanto à MMP-9, somente nos queratinócitos, não se observou aumento de expressão do lado irradiado, ficando essa evidente nas demais linhagens celulares avaliadas. Conclusões: A UVB na dose de 2 DEM aumenta a expressão imunoistoquímica das MMP-2 e –9 em quase todas as linhagens celulares dos nevos melanocíticos avaliados até uma semana após a irradiação, com exceção feita queratinócitos, com a MMP-9. / Background: the incidence of melanoma continues to increase in several countries. Melanocytic nevi may represent precursors or risk indicators of cutaneous melanoma. Ultraviolet radiation is the main environmental risk factor in their development. Studies with irradiated nevi show that ultraviolet B (UVB) radiation can cause morphological and biological alterations similar to those of a melanoma in situ. Matrix metalloproteinases (MMP) are proteolytic enzymes, and MMP-2 and -9 (gelatinase A and B) in particular, appear to be involved with tumour invasion, the formation of metastases and neoangiogenesis in melanomas. This study aims to evaluate the effects of UVB radiation on the immunohistochemical expression of MMP–2 and –9 in different cell lines from melanocytic nevi. Methods: one half of each of the forty-two melanocytic nevi used in the study was irradiated with 2 MEDs (Minimal Erythema Dosis) of UVB radiation and excised one week later. Three different observers were given the task of comparing the intensity of the immunohistochemical expression of the MMP –2 and –9 on the irradiated and nonirradiated sides of keratinocytes, melanocytes from the epidermis and upper dermis, endothelial cells and fibroblasts. The collected data were analysed using the paired t test for differences in expression and ICC in order to assess the homogeneity of the evaluations made by the observers. Results: in relation to the expression of MMP–2, all the cell lines showed an increase on the irradiated sides, especially the epidermal melanocytes. Regarding MMP-9, while no significant increase in its expression in keratinocytes was noted on the irradiated side, significant increases were observed in the remaining lines. Conclusions: UVB radiation at 2 MEDs increases the immunohistochemical expression of MMP –2 and –9 in almost all evaluated cell lines up to one week after irradiation, with the exception of MMP-9 in keratinocytes.

Introdução: a incidência dos melanomas permanece em ascensão em diversos países. Os nevos melanocíticos podem ser seus precursores ou marcadores de risco. A radiação ultravioleta é o principal fator de risco ambiental para o seu desenvolvimento. Estudos com nevos irradiados mostram que a radiação ultravioleta B (UVB) pode causar alterações morfológicas e bioquímicas semelhantes às de um melanoma in situ. As metaloproteinases da matriz (MMP) são enzimas proteolíticas e, particularmente, as MMP-2 e –9 (gelatinases A e B) parecem estar associadas à invasão tumoral, à formação de metástases e de neoangiogênese em melanomas. O objetivo do presente estudo é avaliar os efeitos da UVB nas expressões imunoistoquímicas de MMP-2 e –9 nas diferentes linhagens celulares de nevos melanocíticos. Métodos: quarenta e dois nevos melanocíticos tiveram suas metades irradiadas com dose de 2 DEM (dose eritematosa mínima) de UVB e foram excisados uma semana após. As expressões imunoistoquímicas das MMP-2 e -9 foram comparadas, quanto à sua intensidade, por três avaliadores diferentes entre os lados irradiados e não irradiados em queratinócitos, melanócitos de epiderme e derme superior, células endoteliais e fibroblastos. Os dados foram analisados pelo teste t pareado para as diferenças de expressão e pelo ICC para avaliação da homogeneidade entre as respostas dos observadores. Resultados: com relação à expressão imunoistoquímica de MMP-2, todas as linhagens celulares mostraram aumento no lado irradiado, especialmente os melanócitos epidérmicos. Quanto à MMP-9, somente nos queratinócitos, não se observou aumento de expressão do lado irradiado, ficando essa evidente nas demais linhagens celulares avaliadas. Conclusões: A UVB na dose de 2 DEM aumenta a expressão imunoistoquímica das MMP-2 e –9 em quase todas as linhagens celulares dos nevos melanocíticos avaliados até uma semana após a irradiação, com exceção feita queratinócitos, com a MMP-9. / Background: the incidence of melanoma continues to increase in several countries. Melanocytic nevi may represent precursors or risk indicators of cutaneous melanoma. Ultraviolet radiation is the main environmental risk factor in their development. Studies with irradiated nevi show that ultraviolet B (UVB) radiation can cause morphological and biological alterations similar to those of a melanoma in situ. Matrix metalloproteinases (MMP) are proteolytic enzymes, and MMP-2 and -9 (gelatinase A and B) in particular, appear to be involved with tumour invasion, the formation of metastases and neoangiogenesis in melanomas. This study aims to evaluate the effects of UVB radiation on the immunohistochemical expression of MMP–2 and –9 in different cell lines from melanocytic nevi. Methods: one half of each of the forty-two melanocytic nevi used in the study was irradiated with 2 MEDs (Minimal Erythema Dosis) of UVB radiation and excised one week later. Three different observers were given the task of comparing the intensity of the immunohistochemical expression of the MMP –2 and –9 on the irradiated and nonirradiated sides of keratinocytes, melanocytes from the epidermis and upper dermis, endothelial cells and fibroblasts. The collected data were analysed using the paired t test for differences in expression and ICC in order to assess the homogeneity of the evaluations made by the observers. Results: in relation to the expression of MMP–2, all the cell lines showed an increase on the irradiated sides, especially the epidermal melanocytes. Regarding MMP-9, while no significant increase in its expression in keratinocytes was noted on the irradiated side, significant increases were observed in the remaining lines. Conclusions: UVB radiation at 2 MEDs increases the immunohistochemical expression of MMP –2 and –9 in almost all evaluated cell lines up to one week after irradiation, with the exception of MMP-9 in keratinocytes.

Introdução: a incidência dos melanomas permanece em ascensão em diversos países. Os nevos melanocíticos podem ser seus precursores ou marcadores de risco. A radiação ultravioleta é o principal fator de risco ambiental para o seu desenvolvimento. Estudos com nevos irradiados mostram que a radiação ultravioleta B (UVB) pode causar alterações morfológicas e bioquímicas semelhantes às de um melanoma in situ. As metaloproteinases da matriz (MMP) são enzimas proteolíticas e, particularmente, as MMP-2 e –9 (gelatinases A e B) parecem estar associadas à invasão tumoral, à formação de metástases e de neoangiogênese em melanomas. O objetivo do presente estudo é avaliar os efeitos da UVB nas expressões imunoistoquímicas de MMP-2 e –9 nas diferentes linhagens celulares de nevos melanocíticos. Métodos: quarenta e dois nevos melanocíticos tiveram suas metades irradiadas com dose de 2 DEM (dose eritematosa mínima) de UVB e foram excisados uma semana após. As expressões imunoistoquímicas das MMP-2 e -9 foram comparadas, quanto à sua intensidade, por três avaliadores diferentes entre os lados irradiados e não irradiados em queratinócitos, melanócitos de epiderme e derme superior, células endoteliais e fibroblastos. Os dados foram analisados pelo teste t pareado para as diferenças de expressão e pelo ICC para avaliação da homogeneidade entre as respostas dos observadores. Resultados: com relação à expressão imunoistoquímica de MMP-2, todas as linhagens celulares mostraram aumento no lado irradiado, especialmente os melanócitos epidérmicos. Quanto à MMP-9, somente nos queratinócitos, não se observou aumento de expressão do lado irradiado, ficando essa evidente nas demais linhagens celulares avaliadas. Conclusões: A UVB na dose de 2 DEM aumenta a expressão imunoistoquímica das MMP-2 e –9 em quase todas as linhagens celulares dos nevos melanocíticos avaliados até uma semana após a irradiação, com exceção feita queratinócitos, com a MMP-9. / Background: the incidence of melanoma continues to increase in several countries. Melanocytic nevi may represent precursors or risk indicators of cutaneous melanoma. Ultraviolet radiation is the main environmental risk factor in their development. Studies with irradiated nevi show that ultraviolet B (UVB) radiation can cause morphological and biological alterations similar to those of a melanoma in situ. Matrix metalloproteinases (MMP) are proteolytic enzymes, and MMP-2 and -9 (gelatinase A and B) in particular, appear to be involved with tumour invasion, the formation of metastases and neoangiogenesis in melanomas. This study aims to evaluate the effects of UVB radiation on the immunohistochemical expression of MMP–2 and –9 in different cell lines from melanocytic nevi. Methods: one half of each of the forty-two melanocytic nevi used in the study was irradiated with 2 MEDs (Minimal Erythema Dosis) of UVB radiation and excised one week later. Three different observers were given the task of comparing the intensity of the immunohistochemical expression of the MMP –2 and –9 on the irradiated and nonirradiated sides of keratinocytes, melanocytes from the epidermis and upper dermis, endothelial cells and fibroblasts. The collected data were analysed using the paired t test for differences in expression and ICC in order to assess the homogeneity of the evaluations made by the observers. Results: in relation to the expression of MMP–2, all the cell lines showed an increase on the irradiated sides, especially the epidermal melanocytes. Regarding MMP-9, while no significant increase in its expression in keratinocytes was noted on the irradiated side, significant increases were observed in the remaining lines. Conclusions: UVB radiation at 2 MEDs increases the immunohistochemical expression of MMP –2 and –9 in almost all evaluated cell lines up to one week after irradiation, with the exception of MMP-9 in keratinocytes.

While ocean acidification (OA) is predicted to inhibit calcification in marine macroalgae, species whose photosynthesis is limited by current dissolved inorganic carbon (DIC) levels may benefit. Furthermore, variations in macroalgal morphology will likely give rise to a range of OA tolerance in calcifying macroalgae. One genus of calcifying macroalgae that has shown varying species’ tolerance to OA is Halimeda, a major carbonate sediment producer on tropical reefs. Species within this genus occupy a range of habitats within tropical environments (reefs and lagoons), illustrating their ability to adapt to diverse environmental conditions (e.g. carbonate chemistry, irradiance). To date it is not clear if morphological and photophysiological diversity in Halimeda will translate to different tolerances to OA conditions (elevated pCO2 and lower pH). / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

O tratamento fotodinâmico antifúngico (APDT) é um método promissor que combina um fotossensibilizador não tóxico (FS), oxigênio e luz visível para provocar a morte seletiva das células microbianas. O desenvolvimento do APDT depende da identificação de FS que sejam eficazes para as diferentes espécies de patógenos. No presente estudo, as suscetibilidades, in vitro, de conídios de Colletotrichum acutatum, C. gloeosporioides (ambas são espécies fitopatogênicas) e Aspergillus nidulans ao APDT com quatro FS fenotiazínicos [azul de metileno (MB), novo azul de metileno N (NMBN), azul de toluidina O (TBO) e o novo fenotiazínico pentacíclico S137 (S137)] em combinação com a luz vermelha, foram investigadas. Nós também avaliamos a suscetibilidade dos conídios de C. acutatum e A. nidulans ao APDT com o psoraleno 8-metóxipsoraleno (8-MOP), com duas cumarinas (7- metoxicumarina e 5,7-dimetóxicumarina) e com uma furanocumarina (isopimpinelina) em combinação com a radiação solar. Ambas as cumarinas e a furanocumarinas foram extraídas, no presente trabalho, do limão Tahiti (Citrus latifolia). Os efeitos dos tratamentos com os diferentes FS nas folhas de laranja-pera (Citrus sinensis) também foram avaliados. O NMBN e o S137 foram os fenotiazínicos mais eficazes. Os APDT com o NMBN (50 ?M) e S137 (10 ?M) e dose de luz de 25 J cm-2 resultaram na redução de aproximadamente 5 logs na sobrevivência dos conídios das três espécies. O APDT com o 8-MOP e com as cumarinas resultaram em uma redução de aproximadamente 4 logs na sobrevivência dos conídios de C. acutatum e A. nidulans. O APDT com a furanocumarina foi menos efetivo e resultou em uma redução na sobrevivência dos conídios de aproximadamente dois logs para C. acutatum e de três logs para A. nidulans. Nenhum dano nas folhas foi observado quando os FS foram colocados na superfície adaxial das folhas. Os estudos histológicos mostraram que nenhum dos FS fenotiazínicos atravessou a cutícula das folhas. / Antifungal photodynamic treatment (APDT) is a promising method that combines a nontoxic photosensitizer (PS), oxygen and visible light to cause selective killing of microbial cells. The development of APDT depends on identifying effective PS for the different pathogenic species. In the present study, the in vitro susceptibilities of Colletotrichum acutatum, C. gloeosporioides (both are phytophatogenic species) and Aspergillus nidulans conidia to APDT with four phenothiazinium PS [methylene blue (MB), new methylene blue N (NMBN), toluidine blue O (TBO) and the novel pentacicyclic phenothiazinium S137 (S137)] in combination with red light were investigated. We also evaluated the susceptibilities of C. acutatum and A. nidulans conidia to APDT with the psoralen 8-methoxypsoralen (8-MOP), with two coumarins (7-methoxicoumarin and 5,7-dimethoxycoumarin) and one furanocoumarin (isopimpinelin) in combination with solar radiation. Both the coumarins and the furanocoumarin were extracted, in the present work, from Tahiti lemon (Citrus latifolia). The effects of the treatments with all the PS on Citrus sinensis leaves were also evaluated. NMBN and S137 were the more effective phenothiazinium PS. APDT with NMBN (50 ?M) and S137 (10 ?M) and light dose of 25 J cm-2 resulted in a reduction of approximately 5 logs in the survival of the conidia of the three species. APDT with 8-MOP and with the coumarins resulted in a reduction of approximately 4 logs in the survival of C. acutatum and A. nidulans conidia. APDT with the furanocumarin was less effective and resulted in the reduction of approximately 2 logs for C. acutatum and 3 logs for A. nidulans. No damages to the leaves were observed when the PS were spotted on the adaxial surface of the leaves and the plants were exposed to solar radiation. Histological studies showed that the phenothiazinium PS did not cross the leave cuticle.

O basidiomiceto Cryptococcus neoformans é um fungo saprófita, com ampla distribuição geográfica, que é normalmente isolado de solos que contêm excretas de pombos e detritos vegetais. Apesar de saprófita, o fungo pode infectar e causar doença em uma grande variedade de hospedeiros animais, como mamíferos, aves e insetos. O número de casos de micoses graves, causadas por C. neoformans e por outros gêneros de fungos, tem aumentado em todo o mundo, principalmente devido ao aumento do número de indivíduos imunocomprometidos. Adicionalmente, a emergência de novas espécies de patógenos e a seleção de linhagens tolerantes aos antifúngicos comumente utilizados fazem com que o desenvolvimento de novas estratégias para o controle de fungos seja extremamente desejável. A inativação fotodinâmica de fungos é um método novo e promissor, que pode ser utilizado tanto para o controle de micoses (em animais e em vegetais), como para a eliminação de fungos do ambiente. A fotoinativação de fungos é baseada no uso de fotossensibilizadores que se acumulam ou que são preferencialmente metabolizados pelas células do microrganismo-alvo. A seguir, o fotossensibilizador é exposto à luz visível, que, na presença de oxigênio, inicia processos fotoquímicos que produzem uma série de espécies reativas de oxigênio capazes de matar as células fúngicas sem provocar danos significativos nos tecidos do hospedeiro. Neste trabalho, foram avaliadas as eficácias do azul de metileno (MB) (em solução e em nanoemulsão), da cloro-alumínio ftalocianina (em nanoemulsão) e do complexo nitrosilo de rutênio (em solução) como fotossensibilizadores para a fotoinativação de células melanizadas e não melanizadas de C. neoformans. C. neoformans foi suscetível à fotoinativação pela cloro-alumínio ftalocianina, com uma inativação próxima de 100% quando foi utilizada uma combinação apropriada da concentração do fotossensibilizador e da dose de luz. A completa fotoinativação do fungo pela ftalocianina, em condições compatíveis com a terapia fotodinâmica, abre a perspectiva da utilização desse fotossensibilizador para o tratamento de micoses causadas por C. neoformans. A fotoinativação pelo MB foi apenas parcial e não ocorreu fotoinativação pelo nitrosilo de rutênio. Nenhum dos fotossensibilizadores matou o fungo na ausência da luz. Também foram feitos experimentos para se verificar a influência do tempo de crescimento e da melanização na tolerância de C. neoformans à fotoinativação pelo MB. Houve diferença significativa na tolerância entre diferentes linhagens de C. neoformans. Para a maioria dos tratamentos [linhagens e tempo de crescimento (4, 6 ou 8 dias)], não houve diferença significativa entre a tolerância de células melanizadas e não melanizadas. Também não foi observada diferença na tolerância entre células com idade de 4 a 8 dias. / The basidiomycete Cryptococcus neoformans is a saprophytic worldwide fungus which is normally isolated from soils contaminated with pigeon excreta and plant detritus. Despite a saprophytic existence, the fungus can infect and cause disease in a wide variety of animal hosts such as mammals, birds and insects. Serious infections caused by C. neoformans and by other genera of fungi have emerged all over the world, primarily due to the increased numbers of immunocompromised individuals. Additionally, the emergence of new species and antimycotic-resistant strains of pathogenic fungi makes the development of new fungus-control techniques highly desirable. Photodynamic inactivation of fungi is a new and promising method that can be used to control localized mycoses or kill fungi in the environment. The photodynamic inactivation of fungi is based on the use of a photosensitizer that accumulates in, or preferentially is metabolized by, cells of the target microorganism. The photosensitizer is then exposed to visible light in the presence of oxygen, and this starts photochemical processes that produce a series of reactive oxygen species (ROS) capable of killing the fungal cells without causing significant damage to host tissues. We report here the efficacy of methylene blue (MB) (in solution and in nanoemulsion), chloroaluminum phthalocyanine (in nanoemulsion) and nitrosyl ruthenium complex (in solution) as photosensitizers in photoinactivation of melanized and nonmelanized Cryptococcus neoformans yeast cells. C. neoformans were susceptible to photoinactivation by chloroaluminum phthalocyanine with inactivation close to 100% when the appropriate combination of photosensitizer concentration and light-exposure dose was used. Photoinactivation by MB was only partial and nitrosyl ruthenium complex was ineffective. In the dark, neither photosensitizers inactivated the fungus. Complementary experiments were performed to estimate the effect of the age of the cells and of melanization in the fungus tolerance to photoinactivation by MB. There was a significative difference in the tolerance among strains of C. neoformans. For most of the treatments (strains and time of growth) there was no difference between the tolerance of melanized and nonmelanized cells. There was no difference in the tolerance among 4 to 8-day cells either.