Stepped merged injection for surface plasmon resonance assays
A device and method for producing data for correction curves for SPR assays provides a plurality of different concentrations of solvent or other compound to the reference surface and active surface of a SPR chip. The concentration are mixed online by two pumps, one connected to a source of a first concentration of solvent or other compound and the other connected to a source of a second, different concentration of solvent or compound. Mixing of the two different concentration of solvent or compound can take place in a fluid mixer and the concentration of solvent or compound in the mixture leaving the fluid mixer can be varied by adjusting the relative speeds of the pumps. The concentration of the solvent or compound mixture can be adjusted during injection of the mixed liquids in order to provide the different concentrations necessary to make a solvent correction curve.
1. A fluid circuit for a surface plasmon resonance (SPR) device, the fluid circuit comprising:
a first flow cell of the SPR device, the first flow cell having a reference surface;
a second flow cell of the SPR device, the second flow cell having an active surface, wherein the active surface comprises a quantity of ligands and the reference surface comprises a lesser quantity or no ligands;
a first pump and a second pump;
a first liquid source;
a second liquid source, the second liquid source upstream of the second pump; and,
a mixer having a first inlet and a second inlet; the second inlet being positioned downstream of the second pump and the first inlet being positioned downstream of the first liquid source, there being no pump between the first liquid source and the first inlet; the mixer having an outlet that is positioned upstream of the first flow cell, the second flow cell and the first pump, the first pump being positioned downstream of the first flow cell and the second flow cell.
2. The fluid circuit of claim 1 , wherein the first flow cell and the second flow cell are arranged in series.
3. The fluid circuit of claim 2 , wherein the first flow cell is downstream of the mixer, and the second flow cell is downstream of the first flow cell.
4. The fluid circuit of claim 1 , further comprising a buffer inlet connected to the first flow cell and a ligand inlet connected to the second flow cell.
5. The fluid circuit of claim 1 , wherein the first liquid source comprises a first liquid at a first concentration, and the second liquid source comprises the first liquid at a second concentration.
6. The fluid circuit of claim 5 , where the first liquid is dimethyl sulfoxide (DMSO).
7. The fluid circuit of claim 1 , wherein during operation of the SPR device, the fluid circuit is capable of controlling a proportion of the first liquid and the second liquid entering the fluid mixer while maintaining a constant liquid flow rate through the mixer.
8. The fluid circuit of claim 7 , wherein the proportion of the first liquid and the second liquid entering the fluid mixer is changed by altering the flow rate of the second pump and without altering the flow rate of the first pump.
9. The fluid circuit of claim 1 , wherein during operation, when the first pump is activated to provide a first flow rate and the second pump is switched off, then only fluid from the first source will be able to flow through the fluid mixer to the flow cells and it will do so at the first flow rate.