Dual Magnetic-/Temperature-Responsive Nanoparticles for Microfluidic Separations and Assays
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- 作者：James J. Lai ; John M. Hoffman ; Mitsuhiro Ebara ; Allan S. Hoffman ; Claude Estournè ; s ; Alain Wattiaux ; Patrick S. Stayton
- 刊名：Langmuir
- 出版年：2007
- 出版时间：June 19, 2007
- 年：2007
- 卷：23
- 期：13
- 页码：7385 - 7391
- 全文大小：492K
- 年卷期：v.23,no.13(June 19, 2007)
- ISSN：1520-5827
文摘
A stimuli-responsive magnetic nanoparticle system for diagnostic target capture and concentration has been developedfor microfluidic lab card settings. Telechelic poly(N-isopropylacrylamide) (PNIPAAm) polymer chains were synthesizedwith dodecyl tails at one end and a reactive carboxylate at the opposite end by the reversible addition fragmentationtransfer technique. These PNIPAAm chains self-associate into nanoscale micelles that were used as dimensionalconfinements to synthesize the magnetic nanoparticles. The resulting superparamagnetic nanoparticles exhibit a 
-Fe2O3core (~5 nm) with a layer of carboxylate-terminated PNIPAAm chains as a corona on the surface. The carboxylategroup was used to functionalize the magnetic nanoparticles with biotin and subsequently with streptavidin. Thefunctionalized magnetic nanoparticles can be reversibly aggregated in solution as the temperature is cycled throughthe PNIPAAm lower critical solution temperature (LCST). While the magnetophoretic mobility of the individualnanoparticles below the LCST is negligible, the aggregates formed above the LCST are large enough to respond toan applied magnetic field. The magnetic nanoparticles can associate with biotinylated targets as individual particles,and then subsequent application of a combined temperature increase and magnetic field can be used to magneticallyseparate the aggregated particles onto the poly(ethylene glycol)-modified polydimethylsiloxane channel walls of amicrofluidic device. When the magnetic field is turned off and the temperature is reversed, the captured aggregatesredisperse into the channel flow stream for further downstream processing. The dual magnetic- and temperature-responsive nanoparticles can thus be used as soluble reagents to capture diagnostic targets at a controlled time pointand channel position. They can then be isolated and released after the nanoparticles have captured target molecules,overcoming the problem of low magnetophoretic mobility of the individual particle while retaining the advantagesof a high surface to volume ratio and faster diffusive properties during target capture.
-Fe2O3core (~5 nm) with a layer of carboxylate-terminated PNIPAAm chains as a corona on the surface. The carboxylategroup was used to functionalize the magnetic nanoparticles with biotin and subsequently with streptavidin. Thefunctionalized magnetic nanoparticles can be reversibly aggregated in solution as the temperature is cycled throughthe PNIPAAm lower critical solution temperature (LCST). While the magnetophoretic mobility of the individualnanoparticles below the LCST is negligible, the aggregates formed above the LCST are large enough to respond toan applied magnetic field. The magnetic nanoparticles can associate with biotinylated targets as individual particles,and then subsequent application of a combined temperature increase and magnetic field can be used to magneticallyseparate the aggregated particles onto the poly(ethylene glycol)-modified polydimethylsiloxane channel walls of amicrofluidic device. When the magnetic field is turned off and the temperature is reversed, the captured aggregatesredisperse into the channel flow stream for further downstream processing. The dual magnetic- and temperature-responsive nanoparticles can thus be used as soluble reagents to capture diagnostic targets at a controlled time pointand channel position. They can then be isolated and released after the nanoparticles have captured target molecules,overcoming the problem of low magnetophoretic mobility of the individual particle while retaining the advantagesof a high surface to volume ratio and faster diffusive properties during target capture.