Surface chemical immobilization of parylene C with thermosensitive block copolymer brushes based onN‐isopropylacrylamide andN‐tert‐butylacrylamide: Synthesis, characterization, and cell adhesion/detachment

Abstract

Poly(N-isopropylacrylamide) (pNIPAM), poly(N-tert-butylacrylamide) (pNTBAM), and their copolymer brushes were covalently immobilized onto parylene C (PC) surfaces via surface initiated atom transfer radical polymerization (ATRP). Contact angle measurement between 13 and 40°C showed that the hydrophobicity of the modified PC surfaces was thermally sensitive. Among these samples, PC grafted with pNIPAM (PC-NI), PC grafted with pNTBAM (PC-NT) and PC grafted with copolymer brushes containing pNTBAM and pNIPAM (PC-NT-NI) exhibited the lower critical solution temperature (LCST) at 29, 22, and 24°C, respectively. Cytocompatibility study for the modified surfaces was performed by 5 days human skin fibroblast culture at 37°C. Data showed that only a very small amount of cells adhered on the PC and PC-NI surfaces, while a significantly higher amount of cell adhesion and growth was observed on PC-NT and PC-NT-NI surfaces. Furthermore, cell detachment at the temperatures of 24 and 6°C were studied after the substrates were cultured with cells at 37°C for 24 h. The results showed that the cells on PC-NI formed the aggregations and loosely attached on the substrate after 30-min culture at 24°C, while no significant cell detachment was observed for PC-NT and PC-NT-NI samples at this temperature. By continuing the cell culture for additional 100 min at 6°C for PC-NT and PC-NT-NI, about 10 and 35% of the cells were found detached respectively, and the unattached cells aggregated on the substrate. In comparison, cells cultured on the tissue culture petri dish (TCP) exhibited no quantity and morphology changes at the culture temperatures of 37, 24, and 6°C. This study showed that: (1) immobilization of PC with nonthermal sensitive pNTBAM could provide PC surface thermal sensitive hydrophilicity; (2) the chlorines on the polymer brushes of PC-NT could be used to further initiate the ATRP pNIPAM and form block copolymer brushes; (3) the incorporation of pNTBAM into pNIPAM on PC-NT-NI could change the surface thermal hydrophilicity property, and be further applied to decrease the LCST of the modified PC surface; (4) grafted pNIPAM brushes on PC-NI by ATRP showed very low cell adhesion and proliferation in 5 days fibroblast culture at 37°C, and cell detached at 24°C; (5) the incorporation of pNTBAM into pNIPAM on PC-NT-NI decreased the thermal sensitivity of cell adhesion/detachment, cell detached at 6°C, but the cell adhesion and proliferation were significantly improved at a wide temperature range.

Copper-Mediated Living Radical Polymerization (Atom Transfer Radical Polymerization and Copper(0) Mediated Polymerization): From Fundamentals to Bioapplications

“…PNIPAAm is by far the most extensively studied thermoresponsive polymer because in aqueous solutions it displays a LCST of around 32 °C, which is close to physiological temperatures . Flat surfaces modified with well-defined PNIPAAm brushes prepared via ATRP ,− and Cu(0)-mediated polymerization (or by disproportionation of Cu­(I) into Cu(0) and Cu­(II)) , have been widely used in the control of cell adhesion and cell detachment.…”

Synthesis and optimization of fluorescent poly(N-isopropyl acrylamide)-coated surfaces by atom transfer radical polymerization for cell culture and detachment

“…See supplementary material for a summary of some of the most recent studies using ATRP of NIPAM for cellular attachment and detachment. 29 Although various polymerization techniques and conditions were used in these studies, [30][31][32][33][34][35][36][37][38][39][40][41][42] there are a few common conclusions that can be made. In general, there is a limit to the length and density of pNIPAM brushes before cells will not adhere to the surface.…”

Mimicking the biological world: Methods for the 3D structuring of artificial cellular environments

“…A cellular attachment and detachment study on functionalize poly(2-chloro xylylene) (PC) with poly(N-isopropylacrylamide) (PC-NI), poly(Ntert-butylacrylamide) (PC-NT), and both (PC-NT-NI) depict that only very small amounts of human skin fibroblasts adhered on the PC and PC-NI surface. However, a significantly higher amount of cellular adhesion and growth was observed on PC-NT and PC-NT-NI surfaces [132]. The focal attachment of bladder urothelial cells and related properties were improved when grown on grafted poly(3-hydroxybutyrate-co-3hydroxyvalerate) with laminin-derived YIGSR peptide sequences [133].…”