Protein Adsorption on Poly(<i>N</i>-isopropylacrylamide) Brushes: Dependence on Grafting Density and Chain Collapse

Xue, Changying; Yönet-Tanyeri, Nihan; Brouette, Nicolas; Sferrazza, Michele; Braun, Paul V.; Leckband, Deborah

doi:10.1021/la2001909

Cited by 133 publications

(165 citation statements)

References 61 publications

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“…However, such an assumption has been shown to break down [54] due to surface-induced crowding [55] and termination effects [56]. Another technique consists of evaluating the grafting density using a surface sensitive technique, such as Xray photoelectron spectroscopy in order to determine the surface coverage of polymerization initiator, but relies on an assumption regarding the fraction of initiator that actually leads to chain growth [57]. The various means for determining the molecular parameters of grafted-from brushes thus present limitations in terms of ease of use or quantitative reliability.…”

Section: B Brush Swelling At Room Temperaturementioning

confidence: 99%

The Conformation of Thermoresponsive Polymer Brushes Probed by Optical Reflectivity

2016

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We describe a microscope-based optical setup that allows us to perform space-and time-resolved measurements of the spectral reflectance of transparent substrates coated with ultrathin films. This technique is applied to investigate the behavior in water of thermosensitive polymer brushes made of poly(N-isopropylacrylamide) grafted on glass. We show that spectral reflectance measurements yield quantitative information about the conformation and axial structure of the brushes as a function of temperature. We study how molecular parameters (grafting density, chain length) affect the hydration state of a brush, and provide one of the few experimental evidence for the occurrence of vertical phase separation in the vicinity of the lower critical solution temperature of the polymer. The origin of the hysteretic behavior of poly(N-isopropylacrylamide) brushes upon cycling the temperature is also clarified. We thus demonstrate that our optical technique allows for in-depth characterization of stimuli-responsive polymer layers, which is crucial for the rational design of smart polymer coatings in actuation, gating or sensing applications.

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Section: B Brush Swelling At Room Temperaturementioning

confidence: 99%

The Conformation of Thermoresponsive Polymer Brushes Probed by Optical Reflectivity

2016

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“…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.…”

Section: Introductionmentioning

confidence: 99%

“…[2][3][4]13 This approach could be more expensive and tedious as compared to the coupling/adhesion promoting approach. [2][3][4][5] However, the thermo-responsive and cellular behaviors on these retained pNIPAAm films as well as the mechanistic study of this coupling/adhesion promoting approach to retain these thermo-responsive polymers, to the best of our knowledge, have not been investigated. In this study, 3-aminopropyltriethoxysilane (APTES) a common coupling agent that exhibits many unique properties due to its molecular nature, especially when it is fully hydrolyzed (containing three -OH groups), is being used for retaining pNIPAAm on a silica based surface.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2017

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Silane coupling agents are commonly employed to link an organic polymer to an inorganic substrate. One of the widely utilized coupling agents is 3-aminopropyltriethoxy silane (APTES). In this study, the authors investigated the ability of APTES to retain thermo-responsive poly(N-isopropylacrylamide) (pNIPAAm) on hydroxylated surfaces such as glass. For comparison purposes, the authors also evaluated the retention behaviors of (1) polystyrene, which likely has weaker van der Waals interactions and acid-base interactions (contributed by hydrogen-bonding) with APTES, on APTES as well as (2) pNIPAAm on two other silane coupling agents, which have similar structures to APTES, but exhibit less interaction with pNIPAAm. Under our processing conditions, the stronger interactions, particularly hydrogen bonding, between pNIPAAm and APTES were found to contribute substantially to the retention of pNIPAAm on the APTES modified surface, especially on the cured APTES layer when the interpenetration was minimal or nonexistent. On the noncured APTES layer, the formation of an APTES-pNIPAAm interpenetrating network resulted in the retention of thicker pNIPAAm films. As demonstrated by water contact angles [i.e., 7 -15 higher at 40 C, the temperature above the lower critical solution temperature (LCST) of 32 C for pNIPAAm, as compared to those at 25 C] and cell attachment and detachment behaviors (i.e., attached/spread at 37 C, above LCST; detached at 20 C, below LCST), the retained pNIPAAm layer (6-15 nm), on both noncured and cured APTES, exhibited thermo-responsive behavior. The results in this study illustrate the simplicity of using the coupling/adhesion promoting ability of APTES to retain pNIPAAm films on hydroxylated substrates, which exhibit faster cell sheet detachment ( 30 min) as compared to pNIPAAm brushes (in hours) prepared using tedious and costly grafting approaches. The use of adhesion promoters to retain pNIPAAm provides an affordable alternative to current thermo-responsive supports for cell sheet engineering and stem cell therapy applications.

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“…7). High affinity between ECM proteins and substrate promotes primary adsorption, whereas a high grafting density tends to suppress primary and maybe ternary adsorption [117,118]. Primary and ternary adsorption favor bioadhesion, whereas a theoretical model predicts that secondary adsorption preferably occurs for large cylindrical proteins [44,119].…”

Section: Smart Bio-surfaces: Example Of Poly(n-isopropylacrylamide) Tmentioning

confidence: 99%

“…In addition to their slight control of LCST, it appears that the grafting density and the chain length also play an important role on bioadhesion. Thus, the material seems to be resistant to the adsorption of either proteins or cells when chain density and chain length are both high [117]. This is explained by the difficulty for proteins to enter the PNIPAM layer due to steric hindrance when chain grafting is dense.…”

Section: Smart Bio-surfaces: Example Of Poly(n-isopropylacrylamide) Tmentioning

confidence: 99%

PNIPAM grafted surfaces through ATRP and RAFT polymerization: Chemistry and bioadhesion

Conzatti

Cavalié

Combes

et al. 2017

Colloids and Surfaces B: Biointerfaces

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a b s t r a c tBiomaterials surface design is critical for the control of materials and biological system interactions. Being regulated by a layer of molecular dimensions, bioadhesion could be effectively tailored by polymer surface grafting. Basically, this surface modification can be controlled by radical polymerization, which is a useful tool for this purpose. The aim of this review is to provide a comprehensive overview of the role of surface characteristics on bioadhesion properties. We place a particular focus on biomaterials functionalized with a brush surface, on presentation of grafting techniques for "grafting to" and "grafting from" strategies and on brush characterization methods. Since atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT) polymerization are the most frequently used grafting techniques, their main characteristics will be explained. Through the example of poly(N-isopropylacrylamide) (PNIPAM) which is a widely used polymer allowing tuneable cell adhesion, smart surfaces involving PNIPAM will be presented with their main modern applications.

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Protein Adsorption on Poly(N-isopropylacrylamide) Brushes: Dependence on Grafting Density and Chain Collapse

Cited by 133 publications

References 61 publications

The Conformation of Thermoresponsive Polymer Brushes Probed by Optical Reflectivity

The Conformation of Thermoresponsive Polymer Brushes Probed by Optical Reflectivity

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

PNIPAM grafted surfaces through ATRP and RAFT polymerization: Chemistry and bioadhesion

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