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Using complementary acoustic and optical techniques for quantitative monitoring of biomolecular adsorption at interfaces.

Konradi R, Textor M, Reimhult E - Biosensors (Basel) (2012)

Bottom Line: In this tutorial review, different optical and acoustic evanescent techniques are used to illustrate how an understanding of the transducer principle of each technique can be exploited for further interpretation of hydrated and extended polymer and biological films.The case studies deal with representative examples of adsorption of protein films, polymer brushes and lipid membranes, and describe e.g., how to deal with strongly vs. weakly hydrated films, large conformational changes and ordered layers of biomolecules.The presented systems and methods are compared to other representative examples from the increasing literature on the subject.

View Article: PubMed Central - PubMed

Affiliation: BASF SE, Advanced Materials and Systems Research, D-67056 Ludwigshafen, Germany. rupert.konradi@basf.com.

ABSTRACT
The great wealth of different surface sensitive techniques used in biosensing, most of which claim to measure adsorbed mass, can at first glance look unnecessary. However, with each technique relying on a different transducer principle there is something to be gained from a comparison. In this tutorial review, different optical and acoustic evanescent techniques are used to illustrate how an understanding of the transducer principle of each technique can be exploited for further interpretation of hydrated and extended polymer and biological films. Some of the most commonly used surface sensitive biosensor techniques (quartz crystal microbalance, optical waveguide spectroscopy and surface plasmon resonance) are briefly described and five case studies are presented to illustrate how different biosensing techniques can and often should be combined. The case studies deal with representative examples of adsorption of protein films, polymer brushes and lipid membranes, and describe e.g., how to deal with strongly vs. weakly hydrated films, large conformational changes and ordered layers of biomolecules. The presented systems and methods are compared to other representative examples from the increasing literature on the subject.

No MeSH data available.


(a) Swollen thickness and stretching of PMOXA side-chains as a function of the grafting density calculated using mOWLS and mVoigt of the PLL-g-PMOXA coatings (see text); (b) The ‘dry’ serum adsorbed mass decreases as a function of the side-chain stretching. Full resistance to protein adsorption is reached for chain stretching of approximately S ≥ 4.
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biosensors-02-00341-f007: (a) Swollen thickness and stretching of PMOXA side-chains as a function of the grafting density calculated using mOWLS and mVoigt of the PLL-g-PMOXA coatings (see text); (b) The ‘dry’ serum adsorbed mass decreases as a function of the side-chain stretching. Full resistance to protein adsorption is reached for chain stretching of approximately S ≥ 4.

Mentions: In Figure 7(a) dfilm and S are plotted as a function of the PMOXA side-chain grafting density. At low grafting densities, up to a value of α ≈ 0.22, both quantities increase approximately linearly with grafting density up to maximum values of dfilm ≈ 10 nm and S = 4.5. In this regime also the adsorbed polymer mass shows a linear increase with grafting density (see Figure 6(a)) and is mainly determined by the number of PMOXA side-chains per PLL backbone. This increase in side-chain density at more or less constant backbone density causes the corresponding increase in chain stretching and swollen thickness. At high grafting densities where the polymer adsorption becomes limited, decreasing swollen thickness and decreasing chain stretching are observed with increasing grafting density. Since OWLS and QCM are mean-field techniques, the measurements cannot be laterally resolved and the quantities mOWLS and mVoigt are average values over the entire surface area. In Equations (5) and (6) the surface number σPMOXA and spacing L of PMOXA side-chains were calculated based on mOWLS, inherently assuming a homogenous distribution of PMOXA side-chains. Thus, any molecular inhomogeneity of the polymer surface coverage, side-chain spacing and stretching are not accounted for in these calculations. Therefore, in the high grafting density regime, where stiffening of the backbone may cause lateral inhomogeneities, the calculated swollen thickness and side-chain stretching would be averaged over densely grafted adsorbed copolymer molecules and uncovered surface area. Thus, these values might not reflect the swollen thickness and chain stretching on a molecular scale.


Using complementary acoustic and optical techniques for quantitative monitoring of biomolecular adsorption at interfaces.

Konradi R, Textor M, Reimhult E - Biosensors (Basel) (2012)

(a) Swollen thickness and stretching of PMOXA side-chains as a function of the grafting density calculated using mOWLS and mVoigt of the PLL-g-PMOXA coatings (see text); (b) The ‘dry’ serum adsorbed mass decreases as a function of the side-chain stretching. Full resistance to protein adsorption is reached for chain stretching of approximately S ≥ 4.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4263558&req=5

biosensors-02-00341-f007: (a) Swollen thickness and stretching of PMOXA side-chains as a function of the grafting density calculated using mOWLS and mVoigt of the PLL-g-PMOXA coatings (see text); (b) The ‘dry’ serum adsorbed mass decreases as a function of the side-chain stretching. Full resistance to protein adsorption is reached for chain stretching of approximately S ≥ 4.
Mentions: In Figure 7(a) dfilm and S are plotted as a function of the PMOXA side-chain grafting density. At low grafting densities, up to a value of α ≈ 0.22, both quantities increase approximately linearly with grafting density up to maximum values of dfilm ≈ 10 nm and S = 4.5. In this regime also the adsorbed polymer mass shows a linear increase with grafting density (see Figure 6(a)) and is mainly determined by the number of PMOXA side-chains per PLL backbone. This increase in side-chain density at more or less constant backbone density causes the corresponding increase in chain stretching and swollen thickness. At high grafting densities where the polymer adsorption becomes limited, decreasing swollen thickness and decreasing chain stretching are observed with increasing grafting density. Since OWLS and QCM are mean-field techniques, the measurements cannot be laterally resolved and the quantities mOWLS and mVoigt are average values over the entire surface area. In Equations (5) and (6) the surface number σPMOXA and spacing L of PMOXA side-chains were calculated based on mOWLS, inherently assuming a homogenous distribution of PMOXA side-chains. Thus, any molecular inhomogeneity of the polymer surface coverage, side-chain spacing and stretching are not accounted for in these calculations. Therefore, in the high grafting density regime, where stiffening of the backbone may cause lateral inhomogeneities, the calculated swollen thickness and side-chain stretching would be averaged over densely grafted adsorbed copolymer molecules and uncovered surface area. Thus, these values might not reflect the swollen thickness and chain stretching on a molecular scale.

Bottom Line: In this tutorial review, different optical and acoustic evanescent techniques are used to illustrate how an understanding of the transducer principle of each technique can be exploited for further interpretation of hydrated and extended polymer and biological films.The case studies deal with representative examples of adsorption of protein films, polymer brushes and lipid membranes, and describe e.g., how to deal with strongly vs. weakly hydrated films, large conformational changes and ordered layers of biomolecules.The presented systems and methods are compared to other representative examples from the increasing literature on the subject.

View Article: PubMed Central - PubMed

Affiliation: BASF SE, Advanced Materials and Systems Research, D-67056 Ludwigshafen, Germany. rupert.konradi@basf.com.

ABSTRACT
The great wealth of different surface sensitive techniques used in biosensing, most of which claim to measure adsorbed mass, can at first glance look unnecessary. However, with each technique relying on a different transducer principle there is something to be gained from a comparison. In this tutorial review, different optical and acoustic evanescent techniques are used to illustrate how an understanding of the transducer principle of each technique can be exploited for further interpretation of hydrated and extended polymer and biological films. Some of the most commonly used surface sensitive biosensor techniques (quartz crystal microbalance, optical waveguide spectroscopy and surface plasmon resonance) are briefly described and five case studies are presented to illustrate how different biosensing techniques can and often should be combined. The case studies deal with representative examples of adsorption of protein films, polymer brushes and lipid membranes, and describe e.g., how to deal with strongly vs. weakly hydrated films, large conformational changes and ordered layers of biomolecules. The presented systems and methods are compared to other representative examples from the increasing literature on the subject.

No MeSH data available.