Polymer interface science is broadening its area to nanotechnologies, medicine, and biotechnology. The well-defined and controlled polymeric interfaces have been developed and provided a variety of surface properties by varying molecular characteristics of the polymer brushes1. However, affinity-based sorting of colloidal particulates, such as cells and viruses, from a mixture of different particles is limited due to the quasi-irreversible adsorption having a high energy barrier to detach particles from the surface.2, 3 This limitation can be overcome by utilizing local oscillating repulsive forces generated at the microstructured stimuli-responsive polymer interface. The particle adhesion force is balanced by the repulsion force. In this study, a microstructured polymer interface consisting of poly(N-isopropylacrylamide) (PNIPAM) and RGD (Arg-Gly-Asp) conjugated polyacrylic acid (PAA) was prepared. PNIPAM is known for a stimuli-responsive polymer that changes its conformation responding to the lower critical solution temperature (LCST)4, so repulsive force is generated by changing its conformation responding to temperature change. PAA is used for the conjugation of adhesive motifs for affinity-based interactions with particles. Such a dynamic regime enables competitive adsorption-desorption of different particles and sorting of colloidal mixtures based on the strength of particle-polymer adhesion. The developed interface was successfully proved its ability to sort the specific particles through the isolation of U-87 MG cancer cells from whole blood cells with one out of billions cells ratio based on the composition of their membrane proteins, integrins.
(1) Azzaroni, Omar. "Polymer brushes here, there, and everywhere: Recent advances in their practical applications and emerging opportunities in multiple research fields." Journal of Polymer Science Part A: Polymer Chemistry 50.16 (2012): 3225-3258.
(2)Housmans, C.; Sferrazza, M.; Napolitano, S., Kinetics of irreversible chain adsorption. Macromolecules 2014, 47 (10), 3390-3393
(3) Yu, C.; Granick, S., Revisiting Polymer Surface Diffusion in the Extreme Case of Strong Adsorption. Langmuir 2014, 30 (48), 14538-14544.
(4) Tsai, Hsin-Yi, et al. "Two-Dimensional Micropatterns of Self-Assembled Poly (N-isopropylacrylamide) Microgels for Patterned Adhesion and Temperature-Responsive Detachment of Fibroblasts." Langmuir: the ACS journal of surfaces and colloids 29.39 (2013).