Effects of magnetic and electric fields, mechanical stress on the conformational state and release behavior of the composite gels with embedded colloid particles
Final Report Abstract
The main objective of the project was the synthesis of the gels and cryogels with embedded emulsion droplets containing hydrophobic (or amphiphilic) substances and investigation of the effect of the external fields on the release of oil droplets from the gels. As the first step we performed a comparative study of the thermo-responsive gels and cryogels with embedded microdroplets of Vaseline, olive, peanut, and linseed oils and their mixtures with hydrophobic dye Sudan 3. These composite gel matrices were obtained by the three-dimensional copolymerization of N- isopropylacrylamide and N,N’-bis(acryloyl)cystamine in the presence of oil emulsions stabilized with sodium dodecylsulfate or Span 80. Polymerization was performed at room temperature for conventional gels and at -15oC for cryogels. It was shown that all synthesized systems exhibit heat-induced collapse at temperatures higher than 34oC. For conventional gels prepared at room temperature shrinking lasts within 20 to 80 min in accordance with the gel composition. No squeezing of oil droplets was observed due to low effective size of the gels’ pores. In contrast, the cryogels having the same composition released a large fraction of oils together with different substances dissolved in the emulsions and the response time was significantly shorter, about tens of seconds. Different vegetable oils can be used as filler for the cryogels. Their chemical nature only slightly affects the amount of the released oil during the gel collapse. The chemical structures of the surfactant used for stabilizing of the emulsions also do not influence strongly the resulting release of oils from the thermo-responsive cryogels. The mechanical stress applied to both conventional gels and cryogels did not result in oil release. Cryogels with embedded oil emuldions are the promising candidates for use as stimuli-responsive carriers of lipophilic drugs and for other biomedical applications. In order to investigate the influence of charged groups on the thermoresponsive behavour of the cryogels we synthesized weakly charged conventional gels and cryogels of acrylamide and N-isopropylacrylamide copolymers with sodium acrylamido-2-methyl-1-propyl sulfonate (AMPS). Contrary to our expectations, we found out that the cryogel collapse temperature, as well as the polyelectrolyte swelling, is weakly dependent on the presence of charges on network chains. As an example of a system capable to release oil droplets containing hydrophobic compounds we prepared composite alginate beads filled with Fe3O4 magnetic particles and Vaseline oil droplets containing the dissolved hydrophobic dye Sudan 3. The optimum composition of the beads as well as the best ultrasound treatment regime was found. The structures of the beads and magnetic particles were studied with the aid of an optical microscope. The destruction of the beads in a constant magnetic field was investigated. The effects of the composition of the beads and the magnitude of the magnetic field on the release of hydrophobic components in the surrounding solution were analyzed. The release of Sudan 3 due to the disruption of the beads attained 75%. Such beads may find application in biomedicine and other fields where the remote on-demand release of hydrophobic (or amphiphilic) components is required, which can be achieved by using the magnetic field.
Publications
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“Magnetic alginate beads for the targeted delivery of functional hydrophobic compounds,” Polym. Sci. Ser. A, vol. 54, no. 12, pp. 955–959, Dec. 2012
G. A. Komarova, S. G. Starodubtsev, and A. R. Khokhlov
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“Intelligent gels and cryogels with embedded emulsions of various oils,” J. Appl. Polym. Sci., vol. 127, no. 4, pp. 2703–2709, Feb. 2013
G. A. Komarova, S. G. Starodubtsev, V. V. Lozinsky, I. R. Nasimova, and A. R. Khokhlov
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“Specific features of the polyelectrolyte behavior of weakly charged cryogels of polyacrylamide and poly(N-isopropylacrylamide),” Polym. Sci. Ser. A, vol. 55, no. 6, pp. 415–420, Jun. 2013
G. A. Komarova, S. G. Starodubtsev, and A. R. Khokhlov
