Effect of Mass Transport on The Adsorption of Albumin on the Gold Surface

D. Yu1, S.-Y. Kim1, Y. Cho2, J. Y. Lee2, H. J. Kim2, and J. W. Kim2

1 Department of Physics Kangwon National University2 Biomedlab Co.

• Effect of Mass Transport

Under completely transport-limited conditions initial binding rates can be expected to increase in parallel with the flow rate1/3.

Using the SPREETATM that is a SPR based sensor, we studied the effect of mass transport on the adsorption of albumin to the gold surface. The mass transport effect dominates the adsorption rate when the binding of albumin onto the gold surface becomes more dominant than the diffusion of albumin near the surface.

• Expectation effect

Surface Plasmon Resonance

angle

Reflectiv

ity

Light (ω) 2D-detectorarray

p

nm800

x

Surface plasmon wave (Ksp)snmd 50 Evanescent wave (Kev)

z

x

mr

Protein solution

Prism

Metal

*

At resonance angle, incident light dramatically decreases.

Resonance: Surface plasmon wave vector( ) = Evanescent wave vector( )spK evK

Refractive index( ) from resonance angle: , sn ssn *2

*2

sin

sin

pmr

pmr

s

Mass Transport

Mass transport effects occur when the binding rate of analyte to the ligand is higher than diffusion of analyte to the surface. Flow rate is experimental parameter that can be controlled to minimize mass transport effects.

a

ri

C

C

Compartment models

A compartment model for ligands binding to receptors on spherical surface of radius a.

The space outside the sphere is divided into an inner region a< r ≤ ri, where the ligand concentration is C and outer region, r > ri, where the ligand concentration equals the bulk concentration C.

BkRCkdtdB

CCkABkARCkdtVdC

da

da

/

)(/_

BkCRkdtdB er

ef

_

/

At t=0, dC/dt=0 (initial condition)

ACkdtdBR

//lim_

Calculation of Mass transport coefficient(km)

3/12

82.1

hL

vD

A

Ckkm

)(/ 3/1vkckdtdB mm

V : denote the volume of inner compartment.A : the surface area of the cell.R : the concentration of free receptors on the cell surface.C : free ligand concentration in the inner compartment.B : bound ligand concentration on the cell surface. C : bulk concentration.

0 110 220

0.00085

0.00170

25l/min 15l/min 5l/min

RU

t

Experiment Result

1.6 2.4 3.2

0.0007

0.001425l/min.

15l/min.

5l/min.

Bv1/3

Average Point Linear Fit

Relation between flow rate and initial binding rateResponse Unit data on flow rate

The initial binding rate was clearly influenced by changes in the flow rate.

Discussion

The initial binding rate was found to be proportional to flow rate1/3, which is in good accordance with theoretical expectations.

We also found the reaction was dependent on flow rate, which provides further support for the mass transport limited model.

A benefit of the mass transport is that it may be used to determine the amount concentration of analyte.

The investigation of the mass transport effect may help to understand the fluidics.