Browsing by Author "Vilas Boas, Liliana"
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- Assessment of the deformability and velocity of healthy and artificially impaired red blood cells in narrow polydimethylsiloxane (PDMS) microchannelsPublication . Vilas Boas, Liliana; Faustino, Vera; Lima, Rui A.; Miranda, João; Minas, Graça; Fernandes, Carla S.; Catarino, SusanaMalaria is one of the leading causes of death in underdeveloped regions. Thus, the development of rapid, efficient, and competitive diagnostic techniques is essential. This work reports a study of the deformability and velocity assessment of healthy and artificially impaired red blood cells (RBCs), with the purpose of potentially mimicking malaria effects, in narrow polydimethylsiloxane microchannels. To obtain impaired RBCs, their properties were modified by adding, to the RBCs, different concentrations of glucose, glutaraldehyde, or diamide, in order to increase the cells' rigidity. The effects of the RBCs' artificial stiffening were evaluated by combining image analysis techniques with microchannels with a contraction width of 8 µm, making it possible to measure the cells' deformability and velocity of both healthy and modified RBCs. The results showed that healthy RBCs naturally deform when they cross the contractions and rapidly recover their original shape. In contrast, for the modified samples with high concentration of chemicals, the same did not occur. Additionally, for all the tested modification methods, the results have shown a decrease in the RBCs' deformability and velocity as the cells' rigidity increases, when compared to the behavior of healthy RBCs samples. These results show the ability of the image analysis tools combined with microchannel contractions to obtain crucial information on the pathological blood phenomena in microcirculation. Particularly, it was possible to measure the deformability of the RBCs and their velocity, resulting in a velocity/deformability relation in the microchannel. This correlation shows great potential to relate the RBCs' behavior with the various stages of malaria, helping to establish the development of new diagnostic systems towards point-of-care devices.
- Imaging of healthy and malaria-mimicked red blood cells in polydimethylsiloxane microchannels for determination of cells deformability and flow velocityPublication . Vilas Boas, Liliana; Lima, Rui A.; Minas, Graça; Fernandes, Carla S.; Catarino, SusanaImaging analysis techniques have been extensively used to obtain crucial information on blood phenomena in the microcirculation. In the present study, it is intended to mimic the effects of malaria on the red blood cells (RBCs), by changing their properties using a different concentration of glutaraldehyde solution. The effects of the disease in stiffing RBCs were evaluated using polydimethylsiloxane microchannels that comprise contractions with 10 μm width and measuring the cells deformability and the flow velocity in healthy and modified conditions. The obtained results show a decrease in the RBCs deformability and in the flow velocity with the presence of glutaraldehyde, when compared to the behavior of healthy RBCs samples. Therefore, it can be concluded that, using image analysis (ImageJ & PIVLab), it is possible to measure the deformability of the RBCs and the flow velocity and, consequently, obtaining a correlation between the difference of velocities/deformabilities in the microchannels. In the future, this correlation can be used to relate the RBCs behavior with the various stages of malaria. This study can be a starting point for establishing the development of new malaria diagnostic systems towards point-of-care lab-on-a-chip devices.
- Métodos de modificação dos glóbulos vermelhos para mimetizar efeitos da maláriaPublication . Vilas Boas, Liliana; Fernandes, Carla S.; Catarino, SusanaA malária mata mais de um milhão de pessoas por ano e é uma das principais causas de morte em regiões subdesenvolvidas. Assim, o desenvolvimento de técnicas de diagnóstico rápidas, eficientes e competitivas é essencial. Este trabalho focou-se no estudo da deformabilidade dos glóbulos vermelhos (GVs) como biomarcador de malária, visto que esta propriedade do sangue está diretamente relacionada com as alterações que o parasita provoca ao longo da evolução da doença. Sistemas microfluídicos com estreitamentos abruptos juntamente com técnicas de processamento de imagem permitem determinar parâmetros como a velocidade de escoamento e a deformabilidade dos GVs. Assim, utilizando microcanais poliméricos com estreitamentos de 6 µm a 10 µm, efetuou-se um estudo comparativo entre GVs saudáveis e GVs quimicamente modificados para aumentar a sua rigidez e mimetizar o comportamento do parasita da malária. Os resultados obtidos mostram que os GVs saudáveis se deformam naturalmente para atravessar estreitamentos e recuperam rapidamente a sua forma original após o estreitamento. Em contrapartida, nas amostras modificadas com maiores percentagens de químicos o mesmo não se verificou, ocorrendo várias oclusões. Conclui-se assim que o aumento da rigidez dos GVs provoca a diminuição da velocidade de escoamento, da deformabilidade e da capacidade de recuperação de forma das células. Este trabalho assume-se como um contributo para o desenvolvimento de novos sistemas de diagnóstico. Tendo em conta as microtecnologias existentes, será possível integrar, num chip, sensores, microeletrónica e plataformas microfluídicas, de forma a criar um método de diagnóstico simples, rápido, preciso e barato para deteção precoce da malária.