Surface immobilization of thermo-responsive poly(N-isopropylacrylamide) by simple entrapment in a 3-aminopropyltriethoxysilane network

Abstract

In a previous study, we demonstrated the feasibility of retaining poly(N-isopropylacrylamide) (pNIPAAm) on hydroxylated surfaces by spin-coating a blend of pNIPAAm with a small amount of 3-aminopropyltriethoxysilane (APTES), an organosilane, followed by thermal annealing. In this study, we detail the conditions for retaining pNIPAAm films by APTES. Our results show that the difference in surface energy between pNIPAAm and APTES in the blended film resulted in the segregation of APTES molecules to the film/substrate interface, as verified by XPS, during annealing, and the segregated APTES molecules cross-linked to form the APTES network, thus entrapping pNIPAAm. The retained pNIPAAm films (25–35 nm) exhibited thermo-responsive behavior, determined by water contact angles and film thickness in water at temperatures above and below the lower critical solution temperature of pNIPAAm, as well as good cell attachment and rapid detachment (<10 minutes). The gained insights would allow a better design of these thermo-responsive surfaces for cell sheet engineering and other relevant applications.

Retention of poly(N-isopropylacrylamide) on 3-aminopropyltriethoxysilane

“…Polymer retention is often achieved by using different grafting methods [1][2][3][4][5] or by utilizing coupling agents/adhesion promoters. [6][7][8][9] When silanes are used as the adhesion promoters, they are normally deposited on the inorganic/metal surface and cured to form a network, which is expected to interdiffuse with the polymer once the polymer is placed on it. [10][11][12] Thus, an effective adhesion promoter should consist of appropriate groups that would react/interact with the polymer as well as exhibit a suitable solubility with the polymer to form an interdiffused interphase.…”

“…Its functional-NH 2 group and the -OH groups not only react with the active groups on hydrolyzed substrates, but also allow both intermolecular and intramolecular hydrogen bonding. 7,8,[14][15][16][17][18] The short backbone alkyl chains (three -CH 2 ) of APTES provide insufficient intermolecular van der Waals forces to form an ordered monolayer, instead forming a disordered loose three-dimensional multilayered network that anchors to the substrate with fewer chemical bonds. 7,[17][18][19][20] This loose network allows the interdiffusion of a) Electronic mail: bimin@uakron.edu polymer chains, especially for polymers that are compatible with APTES.…”

“…The network can be tightened when the APTES molecules cross-link with each other under thermal annealing to firmly lock the diffused polymer chains in the network. [6][7][8] In addition, to further enhance the coupling, hydrolyzed APTES, with its amino and hydroxyl groups, might allow acid-base (AB) (e.g., H-bonding) interactions with the amide group in pNIPAAm (Ref. 21) as well as vander Waals interactions.…”

A comprehensive review on staphylococcal protein A (SpA): Its production and applications

“…[ [40][41][42][43][44][45][46][47][48][49][50][51][52][53][54] Extracellular expression of recombinant SpA…”

“…[14][15][16][39][40][41][42][43][44] with MabSelect [31]. Some cellular proteins contain two or more adjacent histidine residues which may interfere with affinity purification.…”