Browsing by Author "Shih, Po-Huai"

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AMPFLUID: Aggregation Magnified Post-Assay Fluorescence for Ultrasensitive Immunodetection on Digital Microfluidics
(2015-02-01)
Huang, Cheng-Yeh
;
Shih, Po-Huai
;
Tsai, Po-Yen
;
Lee, I-Chin
;
Hsu, Hsin-Yun
Several strategies are currently employed to enhance the detection limit of bead-based assays, but all these approaches improve the sensitivity by varying the assay procedures chemically or biologically. In previous digital microfluidic setups for bead-based immunoassay, the magnetic beads were suspended for detection. We investigated the effect of bead aggregation in such an immunoassay system and propose the aggregation magnified post-assay fluorescence for ultrasensitive immunodetection on digital microfluidics (AMPFLUID). The detection signal and sensitivity are further enhanced even at the post-assay stage without altering the original assay protocol on employing magnetically triggered post-assay aggregation of beads in a digital microfluidic setup followed by processing of the fluorescent signal. This method is shown to enhance the fluorescent signal with increased consistency and sensitivity after appropriate charge-coupled device (CCD) calibration. This method of on-chip detection allows the fulfilment of consumption of a volume at the nanoliter level and a limit of detection in the range picogram/mL. In our sTNF-RI model immunoassay, only 2.5 nL of sample is required; a detection limit 15 pg/mL is achieved. The decreased uncertainty of the measure is indicated by the error bars and coefficient of variation.
Signal Enhancement by Particle Concentration Using Dielectrophoresis in an Electrowetting-driven Droplet
(2012)
Chuo, Tsung-Min
;
Hsu, Wensyang
;
Huang, Cheng-Yeh
;
Huang, Yu-Shan
;
Chen, Yu-Tong
Signal Enhancement by Particle Concentration Using Dielectrophoresis in an Electrowetting-driven Droplet
(2012-01-01)
Chuo, Tsung-Min
;
Shih, Po-Huai
;
Hsu, Wensyang
;
Huang, Cheng-Yeh
;
Huang, Yu-Shan
This paper describes a new method for enhancing the fluorescence signal of a bead-based immunosensor in a digital microfluidic system by dielectrophoresis (DEP) force. A single droplet containing scattered polystyrene microbeads conjugated with fluorescent dye is first moved by electrowetting to 3-phase spiral electrodes. The fluorescent microbeads are then concentrated by DEP force at 145 VRMS over 100 kHz. It is shown that the proposed microfluidic chip can evidently enhance the fluorescent intensity even there are only very few fluorescent microbeads (10 to 100), where the droplet volume is only 6.25 nanoliter. The total operation time of the concentrating process is less than 3 minutes. The proposed signal enhancement method holds great potential for bead-based immunoassays to have better limit of detection with short analysis time and small sample volume.