RESUMO
Ultra-fine (<1 microm) microfilters are required to effectively trap microbial cells. We designed microfilters featuring a rain drop bypass architecture, which significantly reduces the likelihood of clogging at the cost of limited cell loss. The new rain drop bypass architecture configuration has a substantially lower pressure drop and allows a better efficiency in trapping protozoan cells (Cryptosporidium parvum and Giardia lamblia) in comparison to our previous generation of a microfilter device. A modified version displaying sub-micron filter gaps was adapted to trap and detect bacterial cells (Escherichia coli), through a method of cells labeling, which aims to amplify the fluorescence signal emission and therefore the sensitivity of detection.
Assuntos
Cryptosporidium parvum/isolamento & purificação , Escherichia coli/isolamento & purificação , Técnica Indireta de Fluorescência para Anticorpo/métodos , Giardia lamblia/isolamento & purificação , Técnicas Analíticas Microfluídicas/métodos , Animais , Cryptosporidium parvum/citologia , Cryptosporidium parvum/imunologia , Desenho de Equipamento , Escherichia coli/citologia , Escherichia coli/imunologia , Fluorescência , Técnica Indireta de Fluorescência para Anticorpo/instrumentação , Fluorimunoensaio/instrumentação , Fluorimunoensaio/métodos , Giardia lamblia/citologia , Giardia lamblia/imunologia , Técnicas Analíticas Microfluídicas/instrumentação , Sensibilidade e EspecificidadeRESUMO
Simultaneous sample washing and concentration of two waterborne pathogen samples were demonstrated using a rotational magnetic system under continuous flow conditions. The rotation of periodically arranged small permanent magnets close to a fluidic channel carrying magnetic particle suspension allows the trapping and release of particles along the fluidic channel in a periodic manner. Each trapping and release event resembles one washing cycle. The performance of the magnetic separation system (MSS) was evaluated in order to test its functionality to isolate magnetic-labelled protozoan cells from filtered, concentrated tap water, secondary effluent water, and purified water. Experimental protocols described in US Environmental Protection Agency method 1623 which rely on the use of a magnetic particle concentrator, were applied to test and compare our continuous flow cell separation system to the standard magnetic bead-based isolation instruments. The recovery efficiencies for Giardia cysts using the magnetic tube holder and our magnetic separation system were 90.5% and 90.1%, respectively, from a tap water matrix and about 31% and 18.5%, respectively, from a spiked secondary effluent matrix. The recovery efficiencies for Cryptosporidium cells using the magnetic tube holder and our magnetic separation system were 90% and 83.3%, respectively, from a tap water matrix and about 38% and 36%, respectively, from a spiked secondary effluent matrix. Recoveries from all matrices with the continuous flow system were typically higher in glass tubing conduits than in molded plastic conduits.
Assuntos
Cryptosporidium/isolamento & purificação , Giardia/isolamento & purificação , Separação Imunomagnética/instrumentação , Água/parasitologia , Monitoramento Ambiental/instrumentação , Monitoramento Ambiental/métodos , Desenho de Equipamento , Separação Imunomagnética/métodos , Água/análise , Abastecimento de Água/análiseRESUMO
Cell loss during sample transporting from macro-components to micro-components in integrated microfluidic devices can considerably deteriorate cell detection sensitivity. This intrinsic cell loss was studied and effectively minimized through (a) increasing the tubing diameter connecting the sample storage and the micro-device, (b) applying a hydrodynamic focusing approach for sample delivering to reduce cells contacting and adhesion on the walls of micro-channel and chip inlet; (c) optimizing the filter design with a zigzag arrangement of pillars (13 microm in chamber depth and 0.8 microm in gap) to prolong the effective filter length, and iv) the use of diamond shaped pillar instead of normally used rectangular shape to reduce the gap length between any two given pillar (i.e. pressure drop) at the filter region. Cell trapping and immunofluorescent detection of 12 Giardia lamblia and 12 Cryptosporidium parvum cells in 150 microl solution and 50 MCF-7 breast cancer cells in 150 microl solution was completed within 15 min with trapping efficiencies improved from 79+/-11%, 50.8+/-5.5% and 41.3+/-3.6% without hydrodynamic focusing, respectively, to 90.8+/-5.8%, 89.8+/-16.6% and 77.0+/-9.2% with hydrodynamic focusing.