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Sequential push-pull pumping mechanism for washing and evacuation of an immunoassay reaction chamber on a microfluidic CD platform.

Thio TH, Ibrahim F, Al-Faqheri W, Soin N, Kahar Bador M, Madou M - PLoS ONE (2015)

Bottom Line: However, rotational speed dependency and limited space on a CD are two big obstacles to performing such repetitive filling and siphoning steps.The proposed technique is demonstrated on two CD designs.The two designs and the performance evaluation demonstrate that the technique is simple to implement, reliable, easy to control, and allows for repeated push-pulls and thus filling and emptying of the biosensor chamber.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia; Centre for Innovation in Medical Engineering, Department of Biomedical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia; Faculty of Science, Technology, Engineering and Mathematics, INTI International University, Persiaran Perdana BBN, Putra Nilai, 71800 Nilai, Negeri Sembilan, Malaysia.

ABSTRACT
A centrifugal compact disc (CD) microfluidic platform with reservoirs, micro-channels, and valves can be employed for implementing a complete immunoassay. Detection or biosensor chambers are either coated for immuno-interaction or a biosensor chip is inserted in them. On microfluidic CDs featuring such multi-step chemical/biological processes, the biosensor chamber must be repeatedly filled with fluids such as enzymes solutions, buffers, and washing solutions. After each filling step, the biosensor chamber needs to be evacuated by a passive siphoning process to prepare it for the next step in the assay. However, rotational speed dependency and limited space on a CD are two big obstacles to performing such repetitive filling and siphoning steps. In this work, a unique thermo-pneumatic (TP) Push-Pull pumping method is employed to provide a superior alternative biosensor chamber filling and evacuation technique. The proposed technique is demonstrated on two CD designs. The first design features a simple two-step microfluidic process to demonstrate the evacuation technique, while the second design shows the filling and evacuation technique with an example sequence for an actual immunoassay. In addition, the performance of the filling and evacuation technique as a washing step is also evaluated quantitatively and compared to the conventional manual bench top washing method. The two designs and the performance evaluation demonstrate that the technique is simple to implement, reliable, easy to control, and allows for repeated push-pulls and thus filling and emptying of the biosensor chamber. Furthermore, by addressing the issue of rotational speed dependency and limited space concerns in implementing repetitive filling and evacuation steps, this newly introduced technique increases the flexibility of the microfluidic CD platform to perform multi-step biological and chemical processes.

No MeSH data available.


Performance evaluation of push-wash and pull-evacuation.Performance evaluation of implementing evacuation, rinse and wash using push-wash and pull-evacuation in an immunoassay.
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pone.0121836.g006: Performance evaluation of push-wash and pull-evacuation.Performance evaluation of implementing evacuation, rinse and wash using push-wash and pull-evacuation in an immunoassay.

Mentions: The performance of various combinations of evacuation (E—consisting of a pull-evacuation), rinse (RE—consisting of a partial push-wash and pull-evacuation) and wash (WE—consisting of a push-wash and pull-evacuation) are shown in Fig 6. A low concentration of 0.152 (absorbance value) marks an ideal perfect wash while a high concentration of 1.1802 indicates no washing. As shown, using only an evacuation and no rinse or wash (see E in Fig 6), the concentration is the highest at 1.1802 while an automated wash (RE + 3xWE in Fig 6), and the manual wash (E + 3xWE in Fig 6) produce two of the lowest relative concentrations values of 0.2274 and 0.2108 respectively. As the biosensor chamber is repeatedly push-washed and pull-evacuated, the concentration progressively drops closer to the ideal value, indicating a more effective wash. Comparing experiments that start with an evacuation (E) with those that start with a rinse and evacuation (RE), a rinse and evacuation provides better overall washing. It can be seen that a rinse and evacuation, followed by three consecutive washes and evacuations (RE + 3xWE in Fig 6) produces a concentration value that is close to the manual wash (E + 3xWE in Fig 6). This result is encouraging as it is easier to perform a rinse and evacuation (RE) first, followed by numerous wash and evacuation (WE) than to first perform an evacuation (E) followed by numerous wash and evacuation (WE) (as explained in section 2.3,2, it is necessary to stop the CD to seal the TP air chamber when switching over from an initial evacuation (E) to a wash and evacuate (WE)).


Sequential push-pull pumping mechanism for washing and evacuation of an immunoassay reaction chamber on a microfluidic CD platform.

Thio TH, Ibrahim F, Al-Faqheri W, Soin N, Kahar Bador M, Madou M - PLoS ONE (2015)

Performance evaluation of push-wash and pull-evacuation.Performance evaluation of implementing evacuation, rinse and wash using push-wash and pull-evacuation in an immunoassay.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4390340&req=5

pone.0121836.g006: Performance evaluation of push-wash and pull-evacuation.Performance evaluation of implementing evacuation, rinse and wash using push-wash and pull-evacuation in an immunoassay.
Mentions: The performance of various combinations of evacuation (E—consisting of a pull-evacuation), rinse (RE—consisting of a partial push-wash and pull-evacuation) and wash (WE—consisting of a push-wash and pull-evacuation) are shown in Fig 6. A low concentration of 0.152 (absorbance value) marks an ideal perfect wash while a high concentration of 1.1802 indicates no washing. As shown, using only an evacuation and no rinse or wash (see E in Fig 6), the concentration is the highest at 1.1802 while an automated wash (RE + 3xWE in Fig 6), and the manual wash (E + 3xWE in Fig 6) produce two of the lowest relative concentrations values of 0.2274 and 0.2108 respectively. As the biosensor chamber is repeatedly push-washed and pull-evacuated, the concentration progressively drops closer to the ideal value, indicating a more effective wash. Comparing experiments that start with an evacuation (E) with those that start with a rinse and evacuation (RE), a rinse and evacuation provides better overall washing. It can be seen that a rinse and evacuation, followed by three consecutive washes and evacuations (RE + 3xWE in Fig 6) produces a concentration value that is close to the manual wash (E + 3xWE in Fig 6). This result is encouraging as it is easier to perform a rinse and evacuation (RE) first, followed by numerous wash and evacuation (WE) than to first perform an evacuation (E) followed by numerous wash and evacuation (WE) (as explained in section 2.3,2, it is necessary to stop the CD to seal the TP air chamber when switching over from an initial evacuation (E) to a wash and evacuate (WE)).

Bottom Line: However, rotational speed dependency and limited space on a CD are two big obstacles to performing such repetitive filling and siphoning steps.The proposed technique is demonstrated on two CD designs.The two designs and the performance evaluation demonstrate that the technique is simple to implement, reliable, easy to control, and allows for repeated push-pulls and thus filling and emptying of the biosensor chamber.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia; Centre for Innovation in Medical Engineering, Department of Biomedical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia; Faculty of Science, Technology, Engineering and Mathematics, INTI International University, Persiaran Perdana BBN, Putra Nilai, 71800 Nilai, Negeri Sembilan, Malaysia.

ABSTRACT
A centrifugal compact disc (CD) microfluidic platform with reservoirs, micro-channels, and valves can be employed for implementing a complete immunoassay. Detection or biosensor chambers are either coated for immuno-interaction or a biosensor chip is inserted in them. On microfluidic CDs featuring such multi-step chemical/biological processes, the biosensor chamber must be repeatedly filled with fluids such as enzymes solutions, buffers, and washing solutions. After each filling step, the biosensor chamber needs to be evacuated by a passive siphoning process to prepare it for the next step in the assay. However, rotational speed dependency and limited space on a CD are two big obstacles to performing such repetitive filling and siphoning steps. In this work, a unique thermo-pneumatic (TP) Push-Pull pumping method is employed to provide a superior alternative biosensor chamber filling and evacuation technique. The proposed technique is demonstrated on two CD designs. The first design features a simple two-step microfluidic process to demonstrate the evacuation technique, while the second design shows the filling and evacuation technique with an example sequence for an actual immunoassay. In addition, the performance of the filling and evacuation technique as a washing step is also evaluated quantitatively and compared to the conventional manual bench top washing method. The two designs and the performance evaluation demonstrate that the technique is simple to implement, reliable, easy to control, and allows for repeated push-pulls and thus filling and emptying of the biosensor chamber. Furthermore, by addressing the issue of rotational speed dependency and limited space concerns in implementing repetitive filling and evacuation steps, this newly introduced technique increases the flexibility of the microfluidic CD platform to perform multi-step biological and chemical processes.

No MeSH data available.