Nontoxic and durable salt bridges using hydroxyethylmethacrylate hydrogels.

Polyhydroxyethylmethacrylate polymers (poly-HEMA) form hydrogels that provide an excellent alternative to agar in the production of salt bridges for use in bioelectrochemical experiments. A method for the simple production of poly-HEMA salt bridges is described. The poly-HEMA bridges were compared with agar bridges of similar geometry. Whereas poly-HEMA salt bridges have a conductivity that is 20 times lower than that of agar bridges of a similar geometry, poly-HEMA bridges are capable of dissipating twice the power compared with agar bridges. The mechanical properties of the poly-HEMA bridges make them easy to manufacture, store, and sterilize. When agar bridges were compared with poly-HEMA bridges in long-term cell culture experiments, the failure rate of the agar bridges was found to be approximately 10% per week vs. a virtually nonexistent failure rate for the poly-HEMA bridges. Because poly-HEMA salt bridges are reliable, durable, and nontoxic to cells, they are a practical alternative to agar salt bridges in certain experimental designs.