Functional Biointerfaces Tailored by “Grafting‐To” Brushes

Bittrich, Eva; Stamm, Manfred; Uhlmann, Petra

doi:10.1002/9781119455042.ch10

Cited by 5 publications

(6 citation statements)

References 235 publications

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“…In Figure 1, we plot the pH-dependent brush thickness obtained from null-ellipsometry measurements. 66 It serves as reference data for the model parametrization. In the simulation the average brush height, ⟨H⟩, results from the effective pH-/ IS-dependent interaction of the brush with the implicit solvent.…”

Section: Model and Techniquementioning

confidence: 99%

“…This mapping was obtained by matching the swelling of a pure PAA brush to the one observed in experiments. 66 The second part of the study addressed the swelling behavior of the mixed brush in response to different (pH, T) conditions and, in particular, to characterize the interplay between each species when they respond to these environmental changes. In agreement with recent experiments, we observe a decrease in the temperature-induced responsiveness of PNIPAm when PAA polymers are added to the brush, accompanied by a shift of the lower critical solution temperature of PNIPAm to lower temperatures.…”

Section: Summary and Concluding Remarksmentioning

confidence: 99%

“…The mass of the polymer is M w = 57K. Null-ellipsometry measurements66 serve as reference data, to which we match average height in our simulations by adapting the solvent-mediated Flory− Huggins parameter (cf. inset).…”

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confidence: 99%

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Functional Poly(N-isopropylacrylamide)/Poly(acrylic acid) Mixed Brushes for Controlled Manipulation of Nanoparticles

Léonforte

Müller

2016

Macromolecules

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Molecular dynamics simulations of a coarse-grained model with soft, nonbonded interactions and implicit solvent are used to study the temperature- and pH-sensitive response of mixed brushes composed of poly(N-isopropylacrylamide) [PNIPAm] and poly(acrylic acid) [PAA] polymers. The model is developed in order to address experimentally relevant, large invariant degrees of polymerization, and nonbonded interactions are expressed via a third-order virial expansion of the equation of state. The choice of interaction parameters for PNIPAm mimics the swelling behavior in water as the temperature increases toward the lower critical solution temperature, T LCST, and the model captures the pH-dependent response of PAA at fixed ionic strength (IS). For this case, the solvent-mediated Flory–Huggins parameter is adapted to reproduce the experimental pH swelling of the homopolymer brush. Mixed brushes incorporating various amounts of PAA are considered, and the effect of mixing polymers on the response of the mixed brushes to both temperature and pH changes is discussed. Additionally, nanoparticles (NPs) that preferably interact with the PAA portion of the polymers are considered. As a function of their radius and the size of the functional NP-attractive groups on PAA chains, the capability to capture NP and allow them to penetrate inside brushes is studied at various temperatures and fixed pH. Moreover, the kinetics of adsorption and release of NPs is investigated.

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Section: Model and Techniquementioning

confidence: 99%

Section: Summary and Concluding Remarksmentioning

confidence: 99%

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Functional Poly(N-isopropylacrylamide)/Poly(acrylic acid) Mixed Brushes for Controlled Manipulation of Nanoparticles

Léonforte

Müller

2016

Macromolecules

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“…Figure 2B displays the change in the amount of GOx, modeled from SE data using the refractive index for dry protein and a modified De-Feijter approach (De Feijter et al, 1978 ; Bittrich, 2010 ). Upon introduction of the enzyme in step IV, a continuous increase of GOx can be observed.…”

Section: Resultsmentioning

confidence: 99%

“…For the optical properties of the ambient, the refractive index n (λ) was measured with a digital multiple wavelength refractometer (DSR-lambda, Schmidt+Haensch GmbH& Co.) at eight different wavelengths from 435.8 to 706.5 nm. The amount of enzyme incorporated into the polymer brush layer was calculated according to a modified De-Feijter approach (De Feijter et al, 1978 ; Bittrich, 2010 ).…”

Section: Methodsmentioning

confidence: 99%

In-situ-Investigation of Enzyme Immobilization on Polymer Brushes

et al. 2019

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Herein, we report on the use of a combined setup of quartz-crystal microbalance, with dissipation monitoring and spectroscopic ellipsometry, to comprehensively investigate the covalent immobilization of an enzyme to a polymer layer. All steps of the covalent reaction of the model enzyme glucose oxidase with the poly(acrylic acid) brush by carbodiimide chemistry, were monitored in-situ. Data were analyzed using optical and viscoelastic modeling. A nearly complete collapse of the polymer chains was found upon activation of the carboxylic acid groups with N-(3-Dimethylaminopropyl)-N′-ethylcarbodiimide and N-Hydroxysuccinimide. The reaction with the amine groups of the enzyme occurs simultaneously with re-hydration of the polymer layer. Significantly more enzyme was immobilized on the surface compared to physical adsorption at similar conditions, at the same pH. It was found that the pH responsive swelling behavior was almost not affected by the presence of the enzyme.

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Binary and Bidisperse Polymer Brushes: Coexisting Surface States

Romeis

Sommer

2015

ACS Appl. Mater. Interfaces

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In the present work, we consider polydispersity effects on a mixed polymer brush. Two types of polymer chains with different solvent selectivity being densely grafted together onto an impenetrable surface are forming a binary mixed polymer brush. Using a numerical quasi off-lattice self-consistent field method for heterogeneous chains we study the brush profile upon varying the strength of solvent selectivity (e.g., temperature) and the degree of polymerization of the two chain types (N1 and N2, respectively). For a monodisperse brush (N1 = N2) it is well-known, that the two types of polymers segregate into a two-layer structure, if the difference in solvent selectivity is increased. The state where the chains exposed to their good solvent forming the top layer of the brush can be frustrated for shorter chains and an inversion of the layering takes place. In the inverted state, the top layer is formed by long chains exposed to poor solvent covering the layer of shorter chains. By varying the solvent selectivity of the long chains we show that coexistence of the two states occurs,which indicates a discontinuous phase transition scenario for the switching process. We consider further the case of a very low fraction of short chains and find these chains to undergo a conformational transition of first order from a "coil" state, found deep inside the compact brush layer, to a "flower" state, stretching to the top of the brush upon varying the strength of the solvent selectivity. At the transition both states are found to be quasi-stable with an energy barrier of the order of the chain length in units of kBT. The discontinuous nature of the switching process by combining solvent selectivity and bidispersity can be of high interest for the creation of stimuli-responsive surfaces.

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Functional Biointerfaces Tailored by “Grafting‐To” Brushes

Cited by 5 publications

References 235 publications

Functional Poly(N-isopropylacrylamide)/Poly(acrylic acid) Mixed Brushes for Controlled Manipulation of Nanoparticles

Functional Poly(N-isopropylacrylamide)/Poly(acrylic acid) Mixed Brushes for Controlled Manipulation of Nanoparticles

In-situ-Investigation of Enzyme Immobilization on Polymer Brushes

Binary and Bidisperse Polymer Brushes: Coexisting Surface States

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