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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.


Schematic diagram of the optical waveguide lightmode spectroscopy (OWLS) setup. Light from a He-Ne laser is coupled into the waveguiding film via an optical grating. Only at a specific angle of incidence α, under constructive interference conditions, is a guided mode excited and a peak in light intensity detected. The evanescent field penetrates about 100–200 nm into the bulk solution and senses changes of the refractive index in this region. Thus, molecular adsorption can be precisely monitored by measuring the incoupling angle as a function of time.
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biosensors-02-00341-f002: Schematic diagram of the optical waveguide lightmode spectroscopy (OWLS) setup. Light from a He-Ne laser is coupled into the waveguiding film via an optical grating. Only at a specific angle of incidence α, under constructive interference conditions, is a guided mode excited and a peak in light intensity detected. The evanescent field penetrates about 100–200 nm into the bulk solution and senses changes of the refractive index in this region. Thus, molecular adsorption can be precisely monitored by measuring the incoupling angle as a function of time.

Mentions: OWLS, similar to SPR, is an optical in situ technique capable of monitoring, in real time, changes in the polarizability density, i.e., in the refractive index, in the vicinity of the waveguide surface [21]. As in SPR, the sensing principle of OWLS is based on an evanescent light field, thus confining the probe depth to a region extending less than a few hundred nanometers above the waveguide. In contrast to SPR, the evanescent field, however, does not originate from a surface plasmon, but from light propagating in a planar optical waveguide (see Figure 2).


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

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

Schematic diagram of the optical waveguide lightmode spectroscopy (OWLS) setup. Light from a He-Ne laser is coupled into the waveguiding film via an optical grating. Only at a specific angle of incidence α, under constructive interference conditions, is a guided mode excited and a peak in light intensity detected. The evanescent field penetrates about 100–200 nm into the bulk solution and senses changes of the refractive index in this region. Thus, molecular adsorption can be precisely monitored by measuring the incoupling angle as a function of time.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

biosensors-02-00341-f002: Schematic diagram of the optical waveguide lightmode spectroscopy (OWLS) setup. Light from a He-Ne laser is coupled into the waveguiding film via an optical grating. Only at a specific angle of incidence α, under constructive interference conditions, is a guided mode excited and a peak in light intensity detected. The evanescent field penetrates about 100–200 nm into the bulk solution and senses changes of the refractive index in this region. Thus, molecular adsorption can be precisely monitored by measuring the incoupling angle as a function of time.
Mentions: OWLS, similar to SPR, is an optical in situ technique capable of monitoring, in real time, changes in the polarizability density, i.e., in the refractive index, in the vicinity of the waveguide surface [21]. As in SPR, the sensing principle of OWLS is based on an evanescent light field, thus confining the probe depth to a region extending less than a few hundred nanometers above the waveguide. In contrast to SPR, the evanescent field, however, does not originate from a surface plasmon, but from light propagating in a planar optical waveguide (see Figure 2).

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.