Selective Adhesion and Switchable Release of Breast Cancer Cells via Hyaluronic Acid Functionalized Dual Stimuli-Responsive Microgel Films.

The detection of tumor cells from liquid biopsy samples is of critical importance for early cancer diagnosis, malignancy assessment, and treatment. In this work, coatings of hyaluronic acid (HA)-functionalized dual-stimuli responsive poly( N -isopropylacrylamide) (PNIPAM) microgels are used to study the specificity of breast cancer cell binding and to assess cell friendly release mechanisms for further diagnostic procedures. The microgels are established by straightforward precipitation polymerization with amine bearing comonomers and postfunctionalization with a UV-labile linker that covalently binds HA to the microgel network. Well-defined microgel coatings for cell binding are established via simple physisorption and annealing. The HA-presenting PNIPAM microgel films are shown to specifically adhere CD44 expressing breast cancer cell lines (MDA-MB-231 and MCF-7), where an increase in adhesion correlates with higher CD44 expression and HA functionalization. Upon cooling below the lower critical solution temperature of PNIPAM microgels, the cells could be released; however, 10-30% of the cells still remained on the surface even after prolonged cooling and mild mechanical agitation. A complete cell release is achieved after applying the light stimulus by short UV treatment cleaving HA units from the microgels. Owing to the comparatively straightforward preparation procedures, such dual-responsive microgel films could be considered for the effective capture, release, and diagnostics of tumor cells.