Core-shell microgels with controlled structural properties

Core-shell microgels with controlled structural properties: Here we report on the multistep synthesis of fluorescent core-shell microgels with inner and surface controlled composition. The tunability and versatility of this approach was confirmed in each step of the synthesis by confocal imaging, XPS and AFM. In particular, the in situ AFM measurements allowed us to study the swelling behaviour to understand the structural organization of the layers at single particle level. Microgels have gained great attention in the biomedical field for their wide application in diagnostic and drug delivery systems. The bulk properties as well as the surface features of these particular microparticles define their final performance. In particular, multifunctional microgels with complex architectures have been widely used in multiplex assays for their favourable capability to accommodate encoding systems and anchoring groups for probes to capture circulating targets by simply changing synthesis parameters. In this work a limited set of fluorescent encoded poly(ethyleneglycol) based microgels, of size ranging between 0.5 and 1.3μm, with a core-shell architecture were obtained by combining precipitation and seeded polymerizations. Here we demonstrate the possibility of tailoring and controlling the bulk and surface properties according to the synthesis by fluorescence imaging and pH titrations. Concerning the structural characterization, we adopted a method to calculate polymer fraction volumes from AFM images and combined these with equilibrium swelling theory (Peppas-Merrill equation) to determine the mesh size of the microgels. Surface composition was probed by X-ray photoelectron spectroscopy directly on freeze-dried microgels. In such a way we were able to describe the organizations of the different adlayers also in response to pH, highlighting the possibility of some overlap of the adlayers representing physical barriers at the boundaries of each shell.