Ciencias Exactas y Ciencias de la Salud

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STREM-1 based sepsis detection with centrifugal microfluidics incorporating active valves and image analysis
(2017-11-17) Medrano Danés, Jonathan; Martinez Chapa, Sergio Omar; Mehdi Aeinehvand, Mohammad; Dieck Assad, Graciano; Martins Fernandes, Rute Fabiana
Sepsis is the main cause of neonate death in hospitals. According to WHO, around one million neonatal deaths are caused each year because of sepsis. Rapid and early sepsis detection, are necessary for effective treatment of the patients to reduce the mortality rate, however this is still a big challenge, especially in low income countries with a poor healthcare system. Recently, soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) biomarker has showed to be an accurate indicator for sepsis detection in neonates. When compared to conventional tests that take several days up to a week, sTREM-1 immunoassay is a faster approach for sepsis detection as it can be performed in five hours. However, the sTREM-1 immunoassay must be performed in a clinic laboratory by specialized staff and require several expensive and bulky equipment. One way to enable the sTREM-1 immunoassay outside specialized labs or at point-of-care (POC) is the integration of the complex assay into a centrifugal microfluidic platform. The disc-shaped microfluidic platform also known as lab-on-disc (LoD), employs centrifugal force from spinning of the disc to manipulate samples and reagents. The centrifugal force that exist everywhere on the disc prevents the need for several expensive syringe pumps. However, it makes simultaneous control over the retention and flow of several reagents/samples on a LoD challenging. To overcome this problem and automate sTREM-1 immunoassay for POC settings, this document presents the development of a new sacrificial polyethylene and a novel reversible valving mechanism on LoD. Based on the two valving mechanisms, a sTREM-1 immunoassay LoD is developed for sepsis detection. Integrating a series of sacrificial valves in the disc allowed for storage of reagents in the disc and their controlled release to a reaction chamber. The reversible valve, was used for the retention of each reagent in the detection chamber during incubation periods, and then transferring it to a waste chamber. A portable spinning system was developed to run the assay by microfluidic disc at POC. The successful automation of sTREM1 immunoassay on the microfluidic disc can provide a significant contribution in the reduction of complexity of the resources needed for sepsis detection at POC settings, particularly in remote areas.
Modelling and simulation of an insulator-based DEP microdevice
(Instituto Tecnológico y de Estudios Superiores de Monterrey, 2007-11-01) Collado Arredondo, Esther; Martinez Chapa, Sergio Omar; Lapizco Encinas, Blanca H.; Dieck Assad, Graciano; Lapizco Encinas, Blanca H.; Bouchereau Lara, Frantz; Programa de Graduados; División de Electrónica, Computación, Información y Comunicaciones; Campus Monterrey
The current work presents a finite element method (FEM) model of a microchannel for particle separation using dielectrophoresis (DEP). The model is based on the commercial software COMSOL and Matlab was used to postprocess the FEM results. The microchannel layout consists of an array of insulating cylindrical posts in the midsection of the microchannel, etched in glass. The microchannel was filled with a ionic solution whose pH and conductivity were fixed to known values, by adding NaOH and K2HPO4. A series of experiments had to be conducted. In each experiment, the microchannel was filled with the ionic solution, a sample of fluorescent microspheres was injected in the inlet, and a DC electric field was applied across the channel using Pt electrodes The experiments were recorded using a camera coupled to a microscope. The electrokinetic mobility, which depends on the pH and the conductivity, was estimated using the particle image velocimetry (PIV) method from the captured videos. The insulating posts in the microchannel produce a non-uniform electric field distribution, which in turn generates a dielectrophoretic (DEP) force on the submerged particles. The DEP force competes with the fluid drag force exerted on the particles. At a certain voltage value, particles are trapped. The FEM model used the estimated electrokinetic mobility to predict the trapping voltage and to calculate the particle trajectories. This research work is a preliminary step in characterizing the dielectrophoretic microchannel, whose final target is to be used for the concentration, separation and identification of biological cells.

Ciencias Exactas y Ciencias de la Salud

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