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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.


Mass adsorption kinetics measured simultaneously by QCM-D and SPR, respectively, for the POPC SLB formation process on SiO2. The masses are calculated using the Sauerbrey relation for mQCM and the assumption of a uniformly thick film throughout the adsorption process and a dn/dc ≈ 0.25 for the lipids in an SLB in a p-polarized field [93]. Adapted with permission from Reimhult et al. [14]. Anal. Chem. 2004, 76, 7211–7220. Copyright 2004 American Chemical Society.
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biosensors-02-00341-f008: Mass adsorption kinetics measured simultaneously by QCM-D and SPR, respectively, for the POPC SLB formation process on SiO2. The masses are calculated using the Sauerbrey relation for mQCM and the assumption of a uniformly thick film throughout the adsorption process and a dn/dc ≈ 0.25 for the lipids in an SLB in a p-polarized field [93]. Adapted with permission from Reimhult et al. [14]. Anal. Chem. 2004, 76, 7211–7220. Copyright 2004 American Chemical Society.

Mentions: It was described in the SPR and OWLS sections that changes in the thickness of the adsorbed film, dfilm, and dn/dc affects the mass calculation from the SPR response, by the influence of dfilm on the solution to the equations describing the propagation of light through the multilayer structure to determine n and the influence of both dfilm and dn/dc on Equation (2) [14,15]. Both these parameters are very different for vesicles and SLBs, where dvesicle ~ 50 nm, dSPB ~ 5 nm, and the difference in dn/dc will vary depending on lipid composition and deformation of adsorbed liposomes and ordering of lipids in the SLB. Thus, we have to calculate the respective masses separately, by first separating the transducer signal, ΔΘ, into one for each species. Inspection of Figure 8 yields that ΔD is essentially zero for the SLB formed in the asymptotic limit and it has been demonstrated that the time where the maximum in ΔD occurs is a good estimate of the time at which the critical coverage needed for vesicle rupture is reached [94]. Since only liposomes contribute to changes in ΔD and since the surface is covered only by vesicles up to the critical coverage, ΔD will be used to separate the lipid molecule mass-response of vesicles and SLB in the SPR signal, ΔΘ.


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

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

Mass adsorption kinetics measured simultaneously by QCM-D and SPR, respectively, for the POPC SLB formation process on SiO2. The masses are calculated using the Sauerbrey relation for mQCM and the assumption of a uniformly thick film throughout the adsorption process and a dn/dc ≈ 0.25 for the lipids in an SLB in a p-polarized field [93]. Adapted with permission from Reimhult et al. [14]. Anal. Chem. 2004, 76, 7211–7220. Copyright 2004 American Chemical Society.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

biosensors-02-00341-f008: Mass adsorption kinetics measured simultaneously by QCM-D and SPR, respectively, for the POPC SLB formation process on SiO2. The masses are calculated using the Sauerbrey relation for mQCM and the assumption of a uniformly thick film throughout the adsorption process and a dn/dc ≈ 0.25 for the lipids in an SLB in a p-polarized field [93]. Adapted with permission from Reimhult et al. [14]. Anal. Chem. 2004, 76, 7211–7220. Copyright 2004 American Chemical Society.
Mentions: It was described in the SPR and OWLS sections that changes in the thickness of the adsorbed film, dfilm, and dn/dc affects the mass calculation from the SPR response, by the influence of dfilm on the solution to the equations describing the propagation of light through the multilayer structure to determine n and the influence of both dfilm and dn/dc on Equation (2) [14,15]. Both these parameters are very different for vesicles and SLBs, where dvesicle ~ 50 nm, dSPB ~ 5 nm, and the difference in dn/dc will vary depending on lipid composition and deformation of adsorbed liposomes and ordering of lipids in the SLB. Thus, we have to calculate the respective masses separately, by first separating the transducer signal, ΔΘ, into one for each species. Inspection of Figure 8 yields that ΔD is essentially zero for the SLB formed in the asymptotic limit and it has been demonstrated that the time where the maximum in ΔD occurs is a good estimate of the time at which the critical coverage needed for vesicle rupture is reached [94]. Since only liposomes contribute to changes in ΔD and since the surface is covered only by vesicles up to the critical coverage, ΔD will be used to separate the lipid molecule mass-response of vesicles and SLB in the SPR signal, ΔΘ.

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.