Dataset Information

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.

SUBMITTER: Alghunaim A

PROVIDER: S-EPMC5328667 | biostudies-literature | 2016 Sep

REPOSITORIES: biostudies-literature

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

Alghunaim Abdullah A Brink Eric T ET Newby Bi-Min Zhang BZ

Polymer 20160901

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 t ...[more]

PMID: 28255182

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Project description:Copolymerization of N-isopropylacrylamide (NIPAM), itaconamic acid (IAM; 4-amino-2-methylene-4-oxobutanoic acid) and β-cyclodextrin was investigated in this study. β-cyclodextrin was at first modified by reacting with allyl glycidyl ether to substitute its OH end groups with moieties containing double bonds to facilitate the subsequent radical copolymerization with NIPAM and IAM. It was reported that poly(NIPAM-IAM) can respond to the change of temperature as well as pH value. In this study, the structure of β-cyclodextrin was introduced to poly(NIPAM-IAM) copolymers because of its cavity structure capable of encapsulating a variety of drug molecules. The tri-component copolymers, poly(CD-NIPAM-IAM), were synthesized with different monomeric ratios of NIPAM/IAM/β-CD and the hydrogels of the tri-component copolymers were also synthesized by additionally adding N,N'-methylenebisacrylamide as a cross-linking agent. The results show that the lower critical solution temperature (LCST) of the copolymer (or hydrogel) increases as the molar fraction of IAM increases. The transmission electron microscopic (TEM) images of linear copolymers (no cross-linking) show that molecules undergo self-assembly to have a distinct core-shell structure, compared to poly(CD-NIPAM) which contains no IAM. On the other hand, the scanning electron microscopic (SEM) images of hydrogels show that the pores gradually become sheet-like structures as the molar fraction of IAM increases to enhance the water absorption capacity. In order to exhibit the thermal and pH sensitivities of poly(CD-NIPAM-IAM) as the drug carrier, the drug release of the newly synthesized hydrogels at 37 °C and different pH values, pH = 2 and pH = 7.4, was investigated using atorvastatin which was used primarily as a lipid-lowering drug. The drug release experimental result shows that poly(CD-NIPAM-IAM) as a drug carrier was pH-sensitive and has the largest release rate at pH = 7.4 at 37 °C, indicating it is useful to release drugs in a neutral or alkaline (intestinal) environment.

Project description:In this paper, we report detailed experimental observations of unusual changes in the thickness of solid poly(N-isopropylacrylamide) (PNIPAM) ultrathin films, which are well known to have temperature-responsive hydrophilic-hydrophobic switching properties. To date, a number of studies have been carried out on the bulk and the brush forms of PNIPAM in contact with liquid water, as well as in highly humid environments, and, recently, these ultrathin films have been preliminarily shown to exhibit temperature responses even under low-humidity, ambient conditions. In this work, the thicknesses of ultrathin PNIPAM films in a temperature/moisture-controlled sample stage were monitored continuously using multichannel X-ray reflectometry. At room temperature, the sample thickness showed an unexpected increase after thermal treatment at 70 °C for 3 h. In the temperature cycle between 15 and 60 °C, heating and cooling resulted in some clear differences. During cooling, initially, the thickness was almost constant but began to increase when the temperature exceeded 33 °C, which corresponds to the lower critical solution temperature (LCST). This observation indicates that the PNIPAM ultrathin film is sensitive to the small amounts of water contained in the air, even under ambient, low-humidity conditions. On the other hand, during heating run from 15 to 60 °C, the humidity dependence was monotonic, and no specific changes in the PNIPAM films were observed at around the LCST. By studying the humidity dependence, we found that the hydrophilic and hydrophobic states of the PNIPAM ultrathin film exhibit different temperature dependence behaviors. In addition, we found that swelling takes place even under low-moisture conditions. To understand the difference in the thickness changes observed on cooling and heating further, some models considering the effect of the boundary conditions in the polymer ultrathin film system were considered. In the case of the ultrathin film, the hydrophilic/hydrophobic switching property occurred only in the surface layer, which dominated the absorption of water molecules from air. In contrast, the interface layer was time-stable and provided an escape route for water molecules during heating.

Dataset Information

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

Publications

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

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