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pH- and thermoresponsive nanocomposite composed of poly(N-acryloyl glycine) (PNAG) matrix and magnetite nanoparticle (MNP) was synthesized and then used for drug controlled release application. The effects of crosslinkers, e.g., ethylenediamine and tris(2-aminoethyl)amine, and their concentrations (1 and 10 mol%) on the size, magnetic separation ability, and water dispersibility of the nanocomposite were investigated. The nanocomposite crosslinked with tris(2-aminoethyl)amine (size ranging between 50 and 150 nm in diameter) can be rapidly separated by a magnet while maintaining its good dispersibility in water. It can respond to the pH and temperature change as indicated by the changes in its zeta potential and hydrodynamic size. From the in vitro release study, theophylline as a model drug was rapidly released when the pH changed from neutral to acidic/basic conditions or when increasing the temperature from 10°C to 37°C. This novel nanocomposite showed a potential application as a magnetically guidable vehicle for drug controlled release with pH- and thermotriggered mechanism.

The synthesis of negatively charged magnetite nanoclusters grafted with poly(acrylic acid) (PAA) and their application as reusable nanosupports for adsorption with antibodies and antigens are presented in this article. They were facilely prepared via the free-radical polymerization of PAA in the presence of functionalized magnetite nanoparticles to obtain highly negative charged nanoclusters with a high magnetic responsiveness and good dispersibility and stability in water. According to transmission electron microscopy, the sizes of the nanoclusters ranged between 200 and 500 nm, without large aggregation visually observed in water. The hydrodynamic size of the nanocluster consistently increased with increasing pH of the dispersion; this indicated its pH-responsive properties, which was due to the repulsion of the anionic carboxylate groups in the structure. This nanocluster was successfully used as an efficient and reusable support for adsorption with anti-horseradish peroxidase antibody. It preserved higher than a 97% adsorption ability of the antibody after eight reuse cycles; this signified the potential of this novel nanocluster as a reusable support in the magnetic separation applications of other bioentities.

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A pectin‐coated magnetite nanoparticle functionalized with Hg2+‐specific aptamer was developed to obtain a magnetic nanosorbent having high selectivity toward Hg2+ and facile reusability. The aptamer labeled with biotin was immobilized on pectin‐coated MNP conjugated with streptavidin through the specific biotin–streptavidin interaction to obtain an aptamer‐functionalized nanosorbent. Pectin coated on the particle improved its stability and dispersibility in water, while thymine in the aptamer played an important role as a recognition element, which can bind to the Hg2+ target via T–Hg2+–T complexes. The nanosorbent showed a linear concentration, ranging from 2.8 to 700 μg/L, with the limit of detection of 0.8 ± 0.2 μg/L and limit of quantitation of 2.8 ± 0.2 μg/L for the detection of Hg2+. It showed high selectivity with good tolerance toward Hg2+ in the presence of other metal ions. The system can be repeatedly used for up to 10 cycles of Hg2+ adsorption with only slight changes in its performance. In addition, satisfactory recoveries were also obtained for the detection of Hg2+ in real water samples. This nanosorbent might be a promising tool for extended applications in biological and analytical fields.