Preparation of thermosensitive magnetic particles by dispersion polymerization

https://doi.org/10.1016/S1381-5148(97)00154-5Get rights and content

Abstract

A new kind of thermosensitive magnetic particles with core/shell structure was prepared by copolymerization of styrene (St) and N-isopropylacrylamide (NIPAM) in the presence of Fe3O4 magnetic fluid in ethanol/water medium. The particles shrank above the lower critical solution temperature (LCST) of Fe3O4/P(St-NIPAM) and swelled below the LCST in water. The effect of polymerization parameters such as initiator concentration and NIPAM/St ratio on particles was investigated. Higher initiator concentration formed larger Fe3O4/P(St-NIPAM) particles, and the particles size decreased as the NIPAM/St ratio increased.

Introduction

Magnetic polymer microspheres have been applied to the studies of cell labelling, cell separation, enzyme immunoassay, target drug, etc. Because magnetic separations are relatively rapid and easy, requiring simple equipment, compared to centrifugal separation [1]. Different methods have been applied in the production of magnetic particles 2, 3.

Poly(N-isopropylacrylamide) (PNIPAM) has a lower critical solution temperature (LCST) at 32°C in water, and changes from hydrophilic below the LCST to hydrophobic above it, due to the reversible formation and cleavage of the hydrogen bonds between the amide groups and surrounding water molecules with changing temperature [4]. This reversible thermosensitivity is considered to be used in biomedical or biological field, and so on, such as purification and separation of proteins [5].

In this study, a new kind of multifunctional Fe3O4/P(St-NIPAM) particles with various diameter was prepared by different reaction conditions in the presence of magnetic fluid. In order to coat the Fe3O4 tightly by polymer, we used styrene as a comonomer. The Fe3O4/P(St-NIPAM) particles with thermosensitive and magnetic property would provide useful application, such as protein concentration, reversible release and recovery of enzymes, etc.

Section snippets

Materials

Styrene was treated with sodium hydrate solution to remove the inhibitor and stored at 4°C. NIPAM (Aldrich) was purified by recrystallization from a mixture of 1 : 1 toluene and hexane. All other materials were analytical grade, and used without further purification, including polyethylene glycol (PEG, Mw=4000), potassium persulphate (KPS), hydrogen peroxide (H2O2, 30%), ethanol and ferrous sulphate.

Preparation of magnetic fluid

Fe3O4 magnetic fluid was prepared by precipitation–oxidation method as follows; 70 g of PEG was

Fe3O4 magnetic fluid

Fig. 1 shows the morphology of the Fe3O4 particles. The average diameter was about 50 nm. Most of particles were dispersed uniformly in a water solution. Some of them formed multiparticle aggregates because of the magneto-dipole interparticle interactions.

Fig. 2 shows IR spectra of the Fe3O4 magnetic fluid. Two absorption bands were observed at 1080 cm−1 and 1630 cm−1, the former bands being assigned to the C–O stretching vibration of PEG, the latter to the CO, which indicates that some of

Conclusion

Fe3O4/P(St-NIPAM) thermosensitive magnetic particles were prepared by dispersion copolymerization of St and NIPAM in the presence of Fe3O4 magnetic fluid. These particles with thermosensitive and magnetic property would provide useful application, such as protein purification, reversible release, recovery of enzymes, etc.

Acknowledgements

Project 59573011 supported by National Natural Science Foundation of China.

References (5)

  • J. Ugelstad et al.

    Prog. Polym. Sci.

    (1992)
  • J.P. Chen et al.

    Biomaterials

    (1990)
There are more references available in the full text version of this article.

Cited by (92)

  • Synthesis and coating methods of biocompatible iron oxide/gold nanoparticle and nanocomposite for biomedical applications

    2020, Chinese Journal of Physics
    Citation Excerpt :

    PEG is a water-soluble and biocompatible polymer used in numerous applications in medicine. Many studies have been recorded the utility of PEG [203–210]. It is working to increase the biocompatibility of blood circulation and iron oxide dispersions [211–213].

  • Magnetic polymeric nanocomposites

    2018, Polymeric Nanomaterials in Nanotherapeutics
  • In vitro biocompatibility of magnetic thermo-responsive nanohydrogel particles of poly(N-isopropylacrylamide-co-acrylic acid) with Fe<inf>3</inf>O<inf>4</inf> cores: Effect of particle size and chemical composition

    2013, Colloids and Surfaces B: Biointerfaces
    Citation Excerpt :

    The incorporation of MNPs into PNIPAAm hydrogel particles has received increased attention. PNIPAAm can be used to encapsulate the MNPs to avoid aggregation of the particles [20,21], to prevent the oxidation of the magnetic core [22], and to facilitate cellular binding [23]. Several researchers have synthesized micro- and nano-hydrogel particles consisting of PNIPAAm copolymers and magnetic nanoparticles [6,24–26,21,27–29].

View all citing articles on Scopus
View full text