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Synthesis and Magneto-Thermal Actuation of Iron Oxide Core-PNIPAM Shell Nanoparticles.

Kurzhals S, Zirbs R, Reimhult E - ACS Appl Mater Interfaces (2015)

Bottom Line: Superparamagnetic nanoparticles have been proposed for many applications in biotechnology and medicine.Thereafter, it is shown that local heating by magnetic fields as well as global thermal heating can be used to efficiently and reversibly aggregate, magnetically extract nanoparticles from solution and spontaneously redisperse them.The coupling of magnetic and thermally responsive properties points to novel uses as smart materials, for example, in integrated devices for molecular separation and extraction.

View Article: PubMed Central - PubMed

Affiliation: Institute for Biologically Inspired Materials, Department of Nanobiotechnology, University of Natural Resources and Life Sciences, Vienna , Muthgasse 11, A-1190 Vienna, Austria.

ABSTRACT
Superparamagnetic nanoparticles have been proposed for many applications in biotechnology and medicine. In this paper, it is demonstrated how the excellent colloidal stability and magnetic properties of monodisperse and individually densely grafted iron oxide nanoparticles can be used to manipulate reversibly the solubility of nanoparticles with a poly(N-isopropylacrylamide)nitrodopamine shell. "Grafting-to" and "grafting-from" methods for synthesis of an irreversibly anchored brush shell to monodisperse, oleic acid coated iron oxide cores are compared. Thereafter, it is shown that local heating by magnetic fields as well as global thermal heating can be used to efficiently and reversibly aggregate, magnetically extract nanoparticles from solution and spontaneously redisperse them. The coupling of magnetic and thermally responsive properties points to novel uses as smart materials, for example, in integrated devices for molecular separation and extraction.

No MeSH data available.


Dynamic lightscattering data showing hydrodynamic diameter (main peak of the numberweighted size distribution) and intensity count rate vs temperature.Heating (red diamonds) and cooling steps (blue squares) were 1 °Cwith 5 min to equilibrate at each measurement point, symbols representmean values from 3 runs with error bars giving the standard deviation,(A and B) grafting-to 3.9 nm core/PNIPAM 10 kDa, (C and D) grafting-to10.7 nm core/PNIPAM 20 kDa, (E and F) grafting-from 5.6 nm core/PNIPAM70 kDa.
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fig3: Dynamic lightscattering data showing hydrodynamic diameter (main peak of the numberweighted size distribution) and intensity count rate vs temperature.Heating (red diamonds) and cooling steps (blue squares) were 1 °Cwith 5 min to equilibrate at each measurement point, symbols representmean values from 3 runs with error bars giving the standard deviation,(A and B) grafting-to 3.9 nm core/PNIPAM 10 kDa, (C and D) grafting-to10.7 nm core/PNIPAM 20 kDa, (E and F) grafting-from 5.6 nm core/PNIPAM70 kDa.

Mentions: The size and reversible aggregation of theindividually stabilized core–shell nanoparticles at a concentrationof one mg/mL in ultrapure water were studied by dynamic light scattering(DLS) (Figure 3). Thehydrodynamic sizes determined at room temperature (20 °C) byDLS were 19 nm for the 3.9 nm/10 kDa PNIPAM and 45 nm for the 10.7nm core/20 kDa PNIPAM particles. The grafting-from particles had ahydrodynamic diameter of 30–40 nm, but possibly due to thepresence of clustered cores some uncertainty in the determinationof the hydrodynamic diameter was observed. The DLS detector countrate (Figure 3B,D,F)is a sensitive measure of aggregation due to its strong scaling withaggregate size, and it provides a less biased measure than the mainnumber peak size determined by the built-in CONTIN algorithm (Figure 3A,C,E). However,the count rate recorded at a single angle in DLS is susceptible tothe influence of many parameters of the sample, such as changes insize and refractive index that change the scattering angle distributionand thereby the count rate at a fixed detector angle. The interpretationof a change in count rate is therefore not unambiguous. Nonetheless,it provides a sensitive indicator to determine the temperature-inducedonset of aggregation and deaggregation through a mere change in countrate.


Synthesis and Magneto-Thermal Actuation of Iron Oxide Core-PNIPAM Shell Nanoparticles.

Kurzhals S, Zirbs R, Reimhult E - ACS Appl Mater Interfaces (2015)

Dynamic lightscattering data showing hydrodynamic diameter (main peak of the numberweighted size distribution) and intensity count rate vs temperature.Heating (red diamonds) and cooling steps (blue squares) were 1 °Cwith 5 min to equilibrate at each measurement point, symbols representmean values from 3 runs with error bars giving the standard deviation,(A and B) grafting-to 3.9 nm core/PNIPAM 10 kDa, (C and D) grafting-to10.7 nm core/PNIPAM 20 kDa, (E and F) grafting-from 5.6 nm core/PNIPAM70 kDa.
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fig3: Dynamic lightscattering data showing hydrodynamic diameter (main peak of the numberweighted size distribution) and intensity count rate vs temperature.Heating (red diamonds) and cooling steps (blue squares) were 1 °Cwith 5 min to equilibrate at each measurement point, symbols representmean values from 3 runs with error bars giving the standard deviation,(A and B) grafting-to 3.9 nm core/PNIPAM 10 kDa, (C and D) grafting-to10.7 nm core/PNIPAM 20 kDa, (E and F) grafting-from 5.6 nm core/PNIPAM70 kDa.
Mentions: The size and reversible aggregation of theindividually stabilized core–shell nanoparticles at a concentrationof one mg/mL in ultrapure water were studied by dynamic light scattering(DLS) (Figure 3). Thehydrodynamic sizes determined at room temperature (20 °C) byDLS were 19 nm for the 3.9 nm/10 kDa PNIPAM and 45 nm for the 10.7nm core/20 kDa PNIPAM particles. The grafting-from particles had ahydrodynamic diameter of 30–40 nm, but possibly due to thepresence of clustered cores some uncertainty in the determinationof the hydrodynamic diameter was observed. The DLS detector countrate (Figure 3B,D,F)is a sensitive measure of aggregation due to its strong scaling withaggregate size, and it provides a less biased measure than the mainnumber peak size determined by the built-in CONTIN algorithm (Figure 3A,C,E). However,the count rate recorded at a single angle in DLS is susceptible tothe influence of many parameters of the sample, such as changes insize and refractive index that change the scattering angle distributionand thereby the count rate at a fixed detector angle. The interpretationof a change in count rate is therefore not unambiguous. Nonetheless,it provides a sensitive indicator to determine the temperature-inducedonset of aggregation and deaggregation through a mere change in countrate.

Bottom Line: Superparamagnetic nanoparticles have been proposed for many applications in biotechnology and medicine.Thereafter, it is shown that local heating by magnetic fields as well as global thermal heating can be used to efficiently and reversibly aggregate, magnetically extract nanoparticles from solution and spontaneously redisperse them.The coupling of magnetic and thermally responsive properties points to novel uses as smart materials, for example, in integrated devices for molecular separation and extraction.

View Article: PubMed Central - PubMed

Affiliation: Institute for Biologically Inspired Materials, Department of Nanobiotechnology, University of Natural Resources and Life Sciences, Vienna , Muthgasse 11, A-1190 Vienna, Austria.

ABSTRACT
Superparamagnetic nanoparticles have been proposed for many applications in biotechnology and medicine. In this paper, it is demonstrated how the excellent colloidal stability and magnetic properties of monodisperse and individually densely grafted iron oxide nanoparticles can be used to manipulate reversibly the solubility of nanoparticles with a poly(N-isopropylacrylamide)nitrodopamine shell. "Grafting-to" and "grafting-from" methods for synthesis of an irreversibly anchored brush shell to monodisperse, oleic acid coated iron oxide cores are compared. Thereafter, it is shown that local heating by magnetic fields as well as global thermal heating can be used to efficiently and reversibly aggregate, magnetically extract nanoparticles from solution and spontaneously redisperse them. The coupling of magnetic and thermally responsive properties points to novel uses as smart materials, for example, in integrated devices for molecular separation and extraction.

No MeSH data available.