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Hydrolytically degradable shells on thermoresponsive microgels

Abstract

Thermoresponsive microgels consisting of poly(N-isopropylacrylamide) cores and poly(N-isopropylmethacrylamide) shells cross-linked with the hydrolytically degradable cross-linker N,O-dimethacryloyl hydroxylamine were synthesized. Their swelling and erosion properties were characterized using a variety of analytical tools including dynamic light scattering, asymmetrical flow field-flow fractionation–multiangle light scattering, and atomic force microscopy. Shell addition leads to particle densification due to the added polymer and the mechanical, compressive force applied by the shell. Upon hydrolytic degradation of the shell cross-links, mechanical and chemical changes occur throughout the core and shell, leading to softer and more porous shells that permit greater core swelling. Such changes, which are triggered on exposure to physiologic conditions, are of potential utility within the realm of triggered drug delivery.

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Abbreviations

NIPAm:

N-Isopropylacrylamide

NIPMAm:

N-Isopropylmethacrylamide

DMHA:

N,O-Dimethacryloyl(hydroxylamine)

BIS:

N,N′-Methylene(bisacrylamide)

SDS:

Sodium dodecyl sulfate

APS:

Ammonium persulfate

DLS:

Dynamic light scattering

A4F:

Asymmetrical flow field-flow fractionation

MALS:

Multiangle light scattering

AFM:

Atomic force microscopy

LCST:

Lower critical solution temperature

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Acknowledgments

This work was partially supported by the National Institutes of Health (1 R01 GM088291-01). Additional funding for J.C.G. was provided by the National Institutes of Health training grant: GTBioMAT Graduate Training for Rationally Designed, Integrative Biomaterials (T32 EB 006343), by the U.S. Department of Education GAANN awards; the Georgia Tech Center for Drug Design, Development, and Delivery; and the Georgia Tech TI:GER program.

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Correspondence to L. Andrew Lyon.

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Gaulding, J.C., South, A.B. & Lyon, L.A. Hydrolytically degradable shells on thermoresponsive microgels. Colloid Polym Sci 291, 99–107 (2013). https://doi.org/10.1007/s00396-012-2692-0

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Keywords

  • Microgels
  • Core/shell
  • Themoresponsive
  • Degradable