Tunable Encapsulation of Proteins within Charged Microgels

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The binding of cytochrome cto pH and thermoresponsive colloidal hydrogels was investigated using multiangle light scattering, measuring loading through changes in particle molar mass and root-mean-square radius. Loosely cross-linked microgels [composed of a random copolymer of N-isopropylacrylamide (NIPAm) and acrylic acid (AAc)] demonstrated a high loading capacity for protein. Encapsulation was dependent on both the charge characteristics of the network and the salinity of the medium. Under favorable binding conditions (neutral pH, low ionic strength), microgels containing the highest studied charge density (30 mol % AAc) were capable of encapsulating greater than 9.7 A 105cytochrome cmolecules per particle. Binding resulted in the formation of a polymer protein complex and condensation of the polymer. Anionic microgels demonstrated a change in density 20-fold in the presence of oppositely charged proteins. These studies of cytochrome cencapsulation represent a significant step toward direct measurement of encapsulation efficiency in complex media as we pursue responsive nanogels and microgels for the delivery of macromolecular therapeutic agents.


This is a pre-copy-editing, author-produced PDF of an article accepted for publication in Macromolecules, volume 44, in 2011 following peer review. The definitive publisher-authenticated version is available online at DOI: 10.1021/ma201365p.


American Chemical Society