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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.


Demonstration of sequential biosensor chamber pull-evacuation:(i) Blue and Red liquids are loaded into source chamber A1 and A2. (ii—iv) Blue liquid bursts from source chamber A1 into biosensor chamber B, then pull-evacuated into waste chamber W. (v—viii) Sequentially Red liquid bursts from source chamber A2 into biosensor chamber B, then pull-evacuated into waste chamber W
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pone.0121836.g004: Demonstration of sequential biosensor chamber pull-evacuation:(i) Blue and Red liquids are loaded into source chamber A1 and A2. (ii—iv) Blue liquid bursts from source chamber A1 into biosensor chamber B, then pull-evacuated into waste chamber W. (v—viii) Sequentially Red liquid bursts from source chamber A2 into biosensor chamber B, then pull-evacuated into waste chamber W

Mentions: The demonstration of sequential biosensor chamber pull-evacuation is shown in Fig 4. The process demonstrates how two liquids that burst at separate times into biosensor chamber B can be sequentially pull-evacuated into waste chamber W. Fig 4(i) illustrates the initiation of the test with the loading of source chambers A1 & A2 with 40μL of Blue and Red colored liquids respectively. Next, the microfluidic CD is spun up gradually to 250 rpm, and the heat source is positioned over the TP air chamber T and powered ON to prepare it for pull-evacuation. During the heating process, the heated air in TP air chamber T expands and escapes through the venting holes in biosensor chamber B. Once the CD surface reaches 50°C (after about 4 minutes), the CD spin speed is gradually increased to 300rpm to burst the Blue liquid from source chamber A1 into biosensor chamber B (see Fig 4(ii)). The heat source is then powered OFF, and the CD is allowed to cool down while rotating at 300rpm. Fig 4(iii) represents the stage at which the CD starts to cool down and the trapped air in TP air chamber T starts to contract and pulls the Blue liquid from biosensor chamber B towards waste chamber W. In Fig 4(iv), the evacuation of the Blue liquid is completed in approximately 4 minutes.


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)

Demonstration of sequential biosensor chamber pull-evacuation:(i) Blue and Red liquids are loaded into source chamber A1 and A2. (ii—iv) Blue liquid bursts from source chamber A1 into biosensor chamber B, then pull-evacuated into waste chamber W. (v—viii) Sequentially Red liquid bursts from source chamber A2 into biosensor chamber B, then pull-evacuated into waste chamber W
© Copyright Policy
Related In: Results  -  Collection

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

pone.0121836.g004: Demonstration of sequential biosensor chamber pull-evacuation:(i) Blue and Red liquids are loaded into source chamber A1 and A2. (ii—iv) Blue liquid bursts from source chamber A1 into biosensor chamber B, then pull-evacuated into waste chamber W. (v—viii) Sequentially Red liquid bursts from source chamber A2 into biosensor chamber B, then pull-evacuated into waste chamber W
Mentions: The demonstration of sequential biosensor chamber pull-evacuation is shown in Fig 4. The process demonstrates how two liquids that burst at separate times into biosensor chamber B can be sequentially pull-evacuated into waste chamber W. Fig 4(i) illustrates the initiation of the test with the loading of source chambers A1 & A2 with 40μL of Blue and Red colored liquids respectively. Next, the microfluidic CD is spun up gradually to 250 rpm, and the heat source is positioned over the TP air chamber T and powered ON to prepare it for pull-evacuation. During the heating process, the heated air in TP air chamber T expands and escapes through the venting holes in biosensor chamber B. Once the CD surface reaches 50°C (after about 4 minutes), the CD spin speed is gradually increased to 300rpm to burst the Blue liquid from source chamber A1 into biosensor chamber B (see Fig 4(ii)). The heat source is then powered OFF, and the CD is allowed to cool down while rotating at 300rpm. Fig 4(iii) represents the stage at which the CD starts to cool down and the trapped air in TP air chamber T starts to contract and pulls the Blue liquid from biosensor chamber B towards waste chamber W. In Fig 4(iv), the evacuation of the Blue liquid is completed in approximately 4 minutes.

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.