Novel, biocompatible, thermo-responsive microgels are synthesized by surfactant-free precipitation copolymerization of <i>N</i>-Vinylcaprolactam (VCL) with 2-methoxyethyl acrylate (MEA). MEA is chosen because PMEA is known for his excellent blood compatibility and low protein adsorption and therefore already in use as coating for artificial organs.<br/>Using optimized precipitation polymerization procedure, up to 32 mol% of MEA can be incorporated into PVCL-based microgels without loss of colloidal stability. Via Raman-Spectroscopy the microgel composition is quantified. Both, calorimetric measurements and a high resolution transverse relaxation NMR study deliver that MEA is located mainly in the microgel shell due to its lower polymerization rate in comparison to VCL. The swelling degree of the microgels decrease with increasing comonomer content. This behavior can be explained by the temperature-responsivity of both monomers: While pure PVCL microgels exhibit a VPTT = 32 °C, linear PMEA has a very low LCST = 0-5 °C. It follows that the microgel shell is already collapsed at room temperature which prevents the swelling of the PVCL-rich core. Consequently, the PVCL/MEA microgels become more rigid and less temperature-sensitive with increasing MEA-content. While the particles with low MEA-content exhibit a core-shell like structure which indicates that the core is denser than the shell, the particles with high MEA-content are rigid and compact that could be approved by AFM measurements (see Figure).<br/>Furthermore, the protein repellent properties of microgel films are investigated. High protein repellence can be obtained for PVCL/MEA microgels, as expected. Cytotoxicity tests with L929 mice fibroblasts show good cell proliferation on PVCL/MEA microgel films that indicates the high biocompatibility of these microgel films. Due to the switchability of PVCL/MEA microgel films from a hydrophobic (collapsed state, cell attachment) to a hydrophilic surface (swollen state, cell repellance) by temperature change, these microgel films can be used for non-invasive cell recovery.

Microgels decorated with 2-methoxyethyl acrylate as new building block for biomaterials

255th National Meeting (2018)

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