Browsing by Author "Catarino, Susana"
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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.
- Biomedical microfluidic devices by using low-cost fabrication techniques: a reviewPublication . Faustino, Vera; Catarino, Susana; Lima, Rui A.; Minas, GraçaOne of the most popular methods to fabricate biomedical microfluidic devices is by using a soft-lithography technique. However, the fabrication of the moulds to produce microfluidic devices, such as SU-8 moulds, usually requires a cleanroom environment that can be quite costly. Therefore, many efforts have been made to develop low-cost alternatives for the fabrication of microstructures, avoiding the use of cleanroom facilities. Recently, low-cost techniques without cleanroom facilities that feature aspect ratios more than 20, for fabricating those SU-8 moulds have been gaining popularity among biomedical research community. In those techniques, Ultraviolet (UV) exposure equipment, commonly used in the Printed Circuit Board (PCB) industry, replaces the more expensive and less available Mask Aligner that has been used in the last 15 years for SU-8 patterning. Alternatively, non-lithographic low-cost techniques, due to their ability for large-scale production, have increased the interest of the industrial and research community to develop simple, rapid and low-cost microfluidic structures. These alternative techniques include Print and Peel methods (PAP), laserjet, solid ink, cutting plotters or micromilling, that use equipment available in almost all laboratories and offices. An example is the xurography technique that uses a cutting plotter machine and adhesive vinyl films to generate the master moulds to fabricate microfluidic channels. In this review, we present a selection of the most recent lithographic and non-lithographic low-cost techniques to fabricate microfluidic structures, focused on the features and limitations of each technique. Only microfabrication methods that do not require the use of cleanrooms are considered. Additionally, potential applications of these microfluidic devices in biomedical engineering are presented with some illustrative examples.
- A comparative study of image processing methods for the assessment of the red blood cells deformability in a microfluidic devicePublication . Faustino, Vera; Catarino, Susana; Pinho, Diana; Minas, Graça; Lima, Rui A.Red blood cells (RBCs) deformability is a high relevant mechanical property, whose variations are associated with some diseases, such as diabetes and malaria. Therefore, the present study aims to compare different image processing methods for assessing the RBCs deformability in a continuous flow, measured in a polydimethylsiloxane (PDMS) microchannel composed by 15 μm spacing inner pillars. The images were acquired with a high speed camera and analyzed with ImageJ software for tracking and measuring the RBCs deformation index (DI). Additionally, to understand the performance of the software, it was performed a comparison between different image processing tools provided by ImageJ and the best methods for the deformation measurements were selected, considering the measured RBCs number and their DIs. The results show that those image methods significantly affect the number of measured RBCs and their DIs and, therefore, the studies focused on the deformability measurements need to take into account the effect of the image processing methods for avoiding loss of relevant information in the images.
- Diagnosis methods for COVID-19: a systematic reviewPublication . Maia, Renata; Carvalho, Violeta Meneses; Faria, Bernardo; Miranda, Inês; Catarino, Susana; Teixeira, Senhorinha F.C.F.; Lima, Rui A.; Minas, Graça; Ribeiro, J.E.At the end of 2019, the coronavirus appeared and spread extremely rapidly, causing millions of infections and deaths worldwide, and becoming a global pandemic. For this reason, it became urgent and essential to find adequate tests for an accurate and fast diagnosis of this disease. In the present study, a systematic review was performed in order to provide an overview of the COVID-19 diagnosis methods and tests already available, as well as their evolution in recent months. For this purpose, the Science Direct, PubMed, and Scopus databases were used to collect the data and three authors independently screened the references, extracted the main information, and assessed the quality of the included studies. After the analysis of the collected data, 34 studies reporting new methods to diagnose COVID-19 were selected. Although RT-PCR is the gold-standard method for COVID-19 diagnosis, it cannot fulfill all the requirements of this pandemic, being limited by the need for highly specialized equipment and personnel to perform the assays, as well as the long time to get the test results. To fulfill the limitations of this method, other alternatives, including biological and imaging analysis methods, also became commonly reported. The comparison of the different diagnosis tests allowed to understand the importance and potential of combining different techniques, not only to improve diagnosis but also for a further understanding of the virus, the disease, and their implications in humans.
- 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.
- Label-free multi-step microfluidic device for mechanical characterization of blood cells: diabetes type IIPublication . Pinho, Diana; Faustino, Vera; Catarino, Susana; Pereira, Ana I.; Minas, Graça; Pinho, Fernando T.; Lima, Rui A.The increasing interest to establish significant correlations between blood cell mechanical measurements and blood diseases, has led to the promotion of microfluidic devices as attractive clinical tools for potential use in diagnosis. A multi-step microfluidic device able to separate red and white blood cells (RBCs and WBCs) from plasma and simultaneously measure blood cells deformability (5 and 20% of hematocrit) is presented in this paper. The device employs passive separation based on the cross-flow filtration principle, introduced at each daughter channel. At the outlets, hyperbolic geometries allow single-cell deformability analysis. The device was tested with blood from five healthy and fifteen diabetic type II voluntary donors. The results have shown that WBCs have lower deformability than RBCs, and no significant differences were observed in WBCs from healthy and pathological blood samples. In contrast, RBCs have shown significant differences, with pathological cells exhibiting lower deformability. Shear rheology has shown that blood from patients with type II diabetes has higher viscosity than blood from healthy donors. This microfluidic device has demonstrated the ability to reduce cell concentration at the outlets down to 1%, an ideal cell concentration for assessing the blood cells deformability, under healthy and pathological conditions. The results provide new insights and quantitative information about the hemodynamics of in vitro type II diabetes mellitus RBCs. Thus, such device can be a promising complement in clinical diagnosis and biological research as part of an integrated blood-on-a-chip system.
- 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.
- A passive microfluidic device based on crossflow filtration for cell separation measurements: a spectrophotometric characterizationPublication . Faustino, Vera; Catarino, Susana; Pinho, Diana; Lima, Rui A.; Minas, GraçaMicrofluidic devices have been widely used as a valuable research tool for diagnostic applications. Particularly, they have been related to the successful detection of different diseases and conditions by assessing the mechanical properties of red blood cells (RBCs). Detecting deformability changes in the cells and being able to separate those cells may be a key factor in assuring the success of detection of some blood diseases with diagnostic devices. To detect and separate the chemically modified RBCs (mimicking disease-infected RBCs) from healthy RBCs, the present work proposes a microfluidic device comprising a sequence of pillars with different gaps and nine different outlets used to evaluate the efficiency of the device by measuring the optical absorption of the collected samples. This latter measurement technique was tested to distinguish between healthy RBCs and RBCs chemically modified with glutaraldehyde. The present study indicates that it was possible to detect a slight differences between the samples using an optical absorption spectrophotometric setup. Hence, the proposed microfluidic device has the potential to perform in one single step a partial passive separation of RBCs based on their deformability.