Mitigation of biomolecular adsorption with hydrophilic polymer additives
Molecular adsorption to the microfluidic device surfaces can be passively and actively mitigated by mixing certain hydrophilic polymers (organic polymers with repeating hydrophilic groups—the preferred polymers being amphipathic surfactants—with the sample liquid during or prior to relevant microfluidic operations. Nonionic surfactants such as polyoxyethylene sorbitan monooleate and polyoxyethylene octyl phenyl ether are especially effective. High molecular weight polyethylene polymers are also effective. The hydrophilic polymers appear to prevent binding of the fouling molecules to the microfluidic by occupying the surface sites in place of the fouling molecules or by interacting with the fouling molecules to prevent binding of the fouling molecules the surface. When surface adsorption is thus mitigated, microfluidic devices can readily handle samples containing biomolecules to enable active sample concentration, filtering, washing, transport, mixing and other sample handling operations.
1. A method of transporting a sample droplet by electrowetting on an electrowetting-on-dielectric (EWOD) surface in a microfluidic device, the method comprising:
(a) providing a sample droplet on the EWOD surface comprising:
(i) a sample;
(ii) a hydrophilic polymer additive; and
(iii) a component which in the absence of the hydrophilic polymer additive would cause the sample droplet to fail to be transported by electrowetting on the EWOD surface; and
(b) transporting the sample droplet by electrowetting on the EWOD surface, wherein in the absence of the hydrophilic polymer, the droplet would fail to be transported.
2. The method according to claim 1 , wherein the hydrophilic polymer additive comprises a nonionic surfactant.
3. The method according to claim 2 , wherein the nonionic surfactant is selected from the group consisting of polyethylene glycol and methoxypolyethylene glycol.
4. A method of conducting droplet transport by electrowetting-on-dielectric (EWOD), the method comprising:
(a) providing an EWOD surface and a droplet on the EWOD surface, the droplet comprising a fouling agent and a quantity of hydrophilic polymer effective to prevent EWOD surface adsorption of the fouling agent and thereby permit transport of a droplet that would not be transportable in the absence of the hydrophilic polymer; and
(b) transporting the droplet by electrowetting on the EWOD surface.
5. The method of claim 4 wherein the droplet comprises a sample.
6. The method of claim 4 wherein the droplet comprises a biological sample.
7. The method of claim 4 wherein the droplet comprises a diagnostic sample.
8. The method of claim 4 wherein the fouling agent comprises a globular protein.
9. The method of claim 4 wherein the fouling agent comprises albumin.
10. The method of claim 4 wherein the hydrophilic polymer exhibits surfactant properties.
11. The method of claim 4 wherein the hydrophilic polymer comprises polyethylene glycol.
12. The method of claim 4 wherein the hydrophilic polymer is non-fouling.
13. The method of claim 4 wherein the hydrophilic polymer is amphipathic.
14. The method according to claim 4 , wherein the hydrophilic polymer comprises a nonionic surfactant.
15. The method according to claim 14 , wherein the nonionic surfactant is selected from the group consisting of polyethylene glycol and methoxypolyethylene glycol.