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.

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: ,

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

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.

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)

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

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.

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.

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.