AC Electrokinetic Concentration of Pathogen from Blood for Rapid Detection of Staphylococcus aureus

• Main Authors: Tzu-YingChen, 陳姿穎
• Other Authors: Hsien-Chang Chang
• Format: Others
• Language: en_US
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/41813081709044860350

碩士 === 國立成功大學 === 奈米科技暨微系統工程研究所 === 100 === Recently, separation and concentration of pathogens before identifying them in clinical settings becomes increasingly important. According to the statistics of National Nosocomial Infection Surveillance System in Centers for Disease Control and Prevention and Surveillance and Control of Pathogens of Epidemiologic Importance, Staphylococcus aureus (S. aureus) is the most common microbial infection of bloodstream in hospitals. Rapid detection is the key point for treatment, but traditional separation methods are time-consuming and require several complicated steps. Therefore, in this research, we developed a microfluidic platform for rapid, selective and long-range concentration of bacteria by combining dielectrophoresis (DEP) with asymmetric polarization AC electroosmosis (A-P ACEO) to selectively concentrate pathogens from blood cells for follow-up detection and analysis. The experimental results show that S. aureus can be selectively separated from blood cells and concentrated at the stagnation point on the central electrode. This is done by coupling ACEO and positive DEP under an optimal electric field gradient as a DC biased voltage of 0.5 V was added to AC voltages of 12 Vpp (outer) and 10 Vpp (inner) at an optimal frequency of 1.3 kHz after diluting blood cells 100-fold. In contrast, a strong negative DEP force was induced in blood cells. If this induced negative DEP force is larger than the ACEO flow induced drag force, blood cells would be excluded at the edge of the electrode. By this way, S. aureus can be trapped on the central electrode surface for the detection using Raman spectroscopy and blood cells can be excluded to reduce the interference in bacterial detection. Raman spectra with a peak at 1521 cm-1 can also be identified using the S. aureus concentration of 5×10^6 CFU/mL for a mixture of the bacteria and blood cells. The AC electrokinetic chip successfully separates S. aureus from blood cells and S. aureus is simultaneously concentrated; thereby, the waiting time is reduced. Compared to traditional selective culture, our simple chip demonstrated an extremely fast (6-10 min) and selective isolation and concentration capability that decreased the bio-target detection time from days to minutes. Our AC electrokinetic chip can be extended to other bacterial detection and identification.