Positively Charged Anticancer Nanoparticles Accumulate in the Acidic Microenvironment of a Tumor

Nanoparticles containing an anticancer drug within a weak polybase sphere accumulate inside tumors where the acidic environment promotes their retention and induces swelling, which enhances delivery of the chemotherapeutic load.

Investigators at Purdue University (West Lafayette, IN, USA) coined the term "pH phoresis" to describe the tendency of nanoparticles composed of weak polybases (such as polyamines) to migrate to areas of negative charge when exposed to a pH gradient.

Furthermore, in regions of lower pH—such as in the pH 6.5-6.9 microenvironment surrounding a tumor—increased protonation of the amines in the shell cause them to repel each other, which forces the particles to expand in size. Doubling the size of the particles would, in theory, result in a similar increase in the efficiency of drug delivery to tumors.

"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," said first author Dr. You-Yeon Won, associate professor of chemical engineering at Purdue University. "Such an effect would be a game changer by delivering the proper dose of anticancer drugs inside tumor cells. This pH phoresis concept also could be combined readily within other established drug-delivery methodologies, making it potentially practical for medical application."

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