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- Spectral Optical Properties of Rabbit Brain Cortex between 200 and 1000 nmPublication . Gonçalves, Tânia M.; Martins, Inês; Silva, Hugo; Tuchin, Valery V.; Oliveira, LuísThe knowledge of the optical properties of biological tissues in a wide spectral range is highly important for the development of noninvasive diagnostic or treatment procedures. The absorption coefficient is one of those properties, from which various information about tissue components can be retrieved. Using transmittance and reflectance spectral measurements acquired from ex vivo rabbit brain cortex samples allowed to calculate its optical properties in the ultraviolet to the near infrared spectral range. Melanin and lipofuscin, the two pigments that are related to the aging of tissues and cells were identified in the cortex absorption. By subtracting the absorption of these pigments from the absorption of the brain cortex, it was possible to evaluate the true ratios for the DNA/RNA and hemoglobin bands in the cortex—12.33-fold (at 260 nm), 12.02-fold (at 411 nm) and 4.47-fold (at 555 nm). Since melanin and lipofuscin accumulation increases with the aging of the brain tissues and are related to the degeneration of neurons and their death, further studies should be performed to evaluate the evolution of pigment accumulation in the brain, so that new optical methods can be developed to aid in the diagnosis and monitoring of brain diseases.
- Invasive and minimally invasive optical detection of pigment accumulation in brain cortexPublication . Oliveira, Luís; Gonçalves, Tânia; Pinheiro, Maria; Fernandes, Luís; Martins, Inês; Silva, Hugo; Oliveira, Hélder; Tuchin, Valery; Oliveira, LuísThe estimation of the spectral absorption coefficient of biological tissues provides valuable information that can be used in diagnostic procedures. Such estimation can be made using direct calculations from invasive spectral measurements or though machine learning algorithms based on noninvasive or minimally invasive spectral measurements. Since in a noninvasive approach, the number of measurements is limited, an exploratory study to investigate the use of artificial generated data in machine learning techniques was performed to evaluate the spectral absorption coefficient of the brain cortex. Considering the spectral absorption coefficient that was calculated directly from invasive measurements as reference, the similar spectra that were estimated through different machine learning approaches were able to provide comparable information in terms of pigment, DNA and blood contents in the cortex. The best estimated results were obtained based only on the experimental measurements, but it was also observed that artificially generated spectra can be used in the estimations to increase accuracy, provided that a significant number of experimental spectra are available both to generate the complementary artificial spectra and to estimate the resulting absorption spectrum of the tissue.
- Development and stability study of graphene nanofluidsPublication . Ramos, C.A.; Martins, Inês; Vilão, G.(Introduction) Graphene nanofluids have been studied since they have different properties that make them applicable in different areas. These nano fluids exhibit photothermal characteristics of interest to an area of great relevance, namely photothermal therapy, which consists of the degradation of cells, for example, cancerous ones, from the increase in temperature. Since graphene nanofluids have numerous potentialities, the study of their development and stability is extremely important. In this project, a graphene nanofluid in ethylene glycol was developed using a twostep method. The nanofluid was subjected to an ultrasonic homogenizer. In order to study the stability of the nanofluid as a function of sonication time, UV-Vis spectroscopy was performed. Additionally, a study of the nanofluid's pH in relation to the sonication time it underwent was conducted.
- Análise da citotoxicidade do grafeno a diferentes concentraçõesPublication . Martins, Inês; Vilão, G.; Pia, MariaO presente trabalho apresenta o desenvolvimento da metodologia a aplicar para o estudo da citotoxicidade de nano fluídos de grafeno em diferentes concentrações em culturas de fibroblastos. Os resultados bibliográficos mostram que baixas concentrações não afetam significativamente a mortalidade celular ou a integridade da membrana, mas podem causar rutura do citoesqueleto de Actina-F. Com o presente estudo visa-se identificar concentrações não tóxicas para aplicações biomédicas seguras.
- Influence of nanofluid on the optical properties of cancer cellsPublication . Martins, Inês; Vilão, Gina(Excerpt of the Introduction) Breast cancer is one of the most common types, with higher incidence in females, and it ranks as the second leading cause of cancer-related deaths in Portugal. Some of the most common symptoms include the appearance of new breast nodules, bone, chest or abdominal pain, shortness of breath, and headaches. The incidence of this disease has a positive correlation with age and is directly related to mammographic density. This relationship arises from the combined effects of cell proliferation in response to mitogens and generic data caused by mutagens.
- Tissue Spectroscopy and Optical Clearing of Colorectal Mucosa in the Pursuit of New Cancer Diagnostic ApproachesPublication . Fernandes, Luís; Silva, Hugo; Martins, Inês; Carvalho, Sónia; Carneiro, Isa; Henrique, Rui; Tuchin, Valery V.; Oliveira, LuísIn this paper we present three studies that demonstrate the applicability of spectroscopy methods and optical clearing treatments in pathology identification and monitoring. In the first study, by obtaining the absorption spectra of human healthy and pathological (adenocarcinoma) colorectal mucosa tissues, it was possible to identify a higher content of a pigment in the diseased tissues. This study also shows that machine learning methods can be used to reach the same differentiated results in vivo through diffuse reflectance spectroscopy. In the second study, the combination of collimated transmittance spectroscopy with optical clearing treatments allowed to obtain the diffusion coefficients of glucose in healthy and pathological colorectal mucosa as: Dglucose=5.8x10–7 cm2/s and Dglucose=4.4x10–7 cm2/s, respectively. This study also demonstrated that the diseased tissues contains about 5% more mobile water than the healthy tissues. The third study was performed to evaluate the protein dissociation mechanism of optical clearing. By treating both healthy and pathological colorectal mucosa tissues with 93%-glycerol, a protein dissociation rate of about 3 times higher was obtained for the pathological mucosa. All the discriminating parameters that result from these studies can be obtained in the in vivo situation through diffuse reflectance spectroscopy and further studies to evaluate their values in different stages of cancer progression are of great importance to develop disease monitoring protocols.
- Estimation of Rabbit Pancreas Dispersion Between 400 and 1000 nmPublication . Martins, Inês; Silva, Hugo; Tuchin, Valery; Oliveira, LuísCurrent biophotonics methods cover the entire optical spectrum from the deep ultraviolet to the terahertz. To optimize such methods for diagnostic and therapeutic applications, the need to obtain the wideband dispersion of tissues is high. The pancreas is a very important organ in the human body, since it produces insulin and its malfunction may induce diabetes. A reduced number of biophotonics publications regarding the pancreas is available, meaning that studies to determine its optical properties and their variation during optical clearing treatments are necessary. Considering this fact, we used the total internal reflection method to measure the refractive index of the rabbit pancreas for wavelengths between 400 and 850 nm. The experimental results allowed to calculate the pancreas dispersion with the Cauchy, Conrady and Cornu equations. It was observed that all those equations provided good data fitting in the spectral range of the measurements, but differences were observed outside these limits. Considering the wavelength of 633 nm, the mean value from the three dispersions was 1.3521, while the one published for porcine pancreas is 1.3517. The dispersion calculated with the Conrady equation does not present a fast decreasing behavior for shorter wavelengths as the ones calculated with the Cauchy and Cornu equations, but comparing these curves with a dispersion for a tissue-like material, all seem to have good agreement. © 2021 Journal of Biomedical Photonics & Engineering