Adaptive Hybrid Molecular Brushes Composed of Chitosan, Polylactide, and Poly(N-vinyl pyrrolidone) for Support and...

Hybrid molecular brushes (HMBs) are macromolecular constructs made up of a backbone polymer and side-chain polymers with distinct properties. They adapt to a changing microenvironment via the conformational mechanism and thus may affect mammalian cell proliferation. Two biobenign HMBs were synthesized in this work: (1) polylactide (PLA) grafted to the chitosan (CHI) backbone to form chitosan-graft-polylactide (CHI-g-PLA), a two-component molecular brush, and (2) poly(N-vinyl pyrrolidone) (PNVP) grafted to chitosan moieties of CHI-g-PLA to form a three-component HMB. The molecular brushes were used to fabricate polymer coatings and nanofibers, guiding the attachment and growth of human dermal fibroblasts (HDFs) while silencing the response of macrophages to the scaffolds. The exterior surface composition of the coatings can be switched by exposure to solvents of different polarities: hydrophilic PNVP chains upon exposure to water or hydrophobic PLA chains upon treatment by anisole. Our experiments demonstrate substantial improvement of the HDF cell attachment and proliferation on the surface of the HMBs as compared to the parent polymers CHI, PLA, and PNVP. A Sirius Red assay and immunofluorescence show that HMBs stimulate production of collagen by HDF cells, which propagate on the polymer substrates revealing well-developed focal adhesion structures. On the other hand, a low attachment of macrophages is observed on the HMB surfaces, in particular if HMBs are switched to the hydrophilic state, i.e., PNVP in the top strata.