"pH phoresis": a new concept that can be used for improving drug delivery to tumor cells.

We propose a new concept describing how nanoparticles composed of weak polybases (such as polyamines) would behave when they are exposed to a pH gradient; weak polybase-containing particles will tend to accumulate preferentially in low pH regions under a pH gradient environment. This phenomenon, which we term "pH phoresis", may provide a useful mechanism for improving the delivery of drugs to cancer cells in solid tumor tissues.