1. Effect of Mass Transport on the Protein Adsorption in a Miniaturized SPR Sensor; SpreetaTM
D. Yu1, S.-Y. Kim1, Y. Cho2, J. Y. Lee2,
H. J. Kim2, and J. W. Kim2
1 Department of Physics
Kangwon National University
2 Biomedlab Co.
Effect of Mass Transport
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
Under completely transport-limited conditions initial binding rates can be expected to increase in parallel with the albumin concentration and flow rate1/3.

2. Surface Plasmon Resonance
angle
Reflectivity
Light (ω)
2D-detector
array
Surface plasmon wave (Ksp)
Evanescent wave (Kev)
Protein solution
Prism
Metal
Surface Plasmon Resonance
At resonance angle, incident light dramatically decreases.
Resonance: Surface plasmon wave vector( ) = Evanescent wave vector( )
Refractive index( ) from resonance angle: ,

3. Inner Structure of SpreetaTM
18.5㎜
28㎜
41㎜
Gold Mirror Film
Thermistor
LED
Gold wafer
Detector
SPREETATM sensor based on the SPR principle

4. Mass Transport(M.T.) Compartment models C ri a
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.
Compartment models a ri C
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.

5. Calculation of Mass transport coefficient(km)
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.
At t=0, dC/dt=0 (initial condition)

6. Phosphate Buffered Saline(PBS)
Process of Experiment
Albumin Solution
Measurement of M.T.
Deionized Water(D.W)
Calibration sensor
0.1M NaOH + 1% Triton X-100
Washing sensor
D.W
Phosphate Buffered Saline(PBS)
Set a base line
PBS
Temperature Sensor
Teflon Tubing
Backing Plate
Teflon Connector Block
Flow Cell
Gold SPR Surface

7. Experiment Result
Relation between concentration and initial binding rate
Fixed flow rate(15㎕/min)and variable concentration(5, 25, 50, 100㎍/㎖)
The initial binding rate was clearly influenced by changes in the concentration.

8. Experiment Result
Response Unit data on flow rate
Relation between flow rate and initial binding rate
Fixed concentration(25㎍/㎖) and variable flow rate(5, 15, 25, 125㎕/min)
The initial binding rate was clearly influenced by changes in the flow rate.

9. Discussion
The initial binding rate was found to be proportional to concentration and flow rate1/3, which is in good accordance with theoretical expectations.
We also found the reaction was dependent on concentration and 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.