Working with engineers at the University of California, San Francisco and Pennsylvania State University, the team members with William Fissell, MD have developed the first entirely new membrane for renal replacement since the high-flux polysulfone dialyser. The membrane, made from a silicon chip just like a microprocessor, has elongated slot-shaped pores, rather than round holes, mirroring the pores that have evolved in many animals. The team tested the novel membranes, predicting that the membrane’s benefit would be in permeability — letting salt and water through, but retaining proteins — and the predictions were correct.
In a recent paper, Andrew Zydney, Chair of Chemical Engineering at Pennsylvania State University and a close collaborator on the bioartificial kidney project, demonstrated that the novel membranes also were able to discriminate between smaller molecules and larger molecules more effectively than membranes with round pores. This finding was borne out by experiments showing that the new membranes could retain albumin and other large proteins while passing 2-microglobulin, a molecule that accumulates in renal failure.
At right, a photo of the prototype bioartificial kidney membrane – photographed at 50x with interference contrast microscopy. Each rectangular window consists of nearly 1,500 nano-scale slit pores measuring 9 nm wide. The small dimension of the pore is manufactured with a tolerance +/- 1 nm and each square centimeter holds more than 3.8 million individual pores.
Current Project Status Estimates
The first phase of the project, which has already been completed, focused on developing the technologies required to reduce the device to a size that could fit into the body and testing the individual components in animal models.
In the second and current phase, the team is doing the sophisticated work needed to scale up the device for use in humans. The team now has the components and a visual model and is pursuing federal and private support to bring the project to clinical use.
The project is on track for the device to be tested in humans within five to seven years.