Silica Microparticles Effectively Transport Anticancer Antibodies

Microparticles of porous silica (functionalized mesoporous silica, or FMS) have been used to transport effectively anticancer antibodies that slowed the growth of melanoma tumors in a mouse model.

Investigators at the University of Washington (Seattle, USA) loaded chemically modified silica microparticles to a very high density with antibodies specific to the CTLA4 cell surface protein, which is present on many types of cancer cells including melanoma. The particles were approximately 6 µm to 12 µm in diameter and contained pores of about 30 nm in diameter. The pores were loaded to a super high density of about 0.4 mg − 0.8 mg of antibody per mg of FMS. Chemical modification of the FMS particles guaranteed long-lasting local release of the antibodies at the site of injection.

Results published in the May 3, 2010, online edition of the Journal of the American Chemical Society (JACS) revealed that FMS-anti-CTLA4 antibody injected directly into a mouse melanoma induced much greater and extended inhibition of tumor growth than did the antibody when given systemically or after having been injected into the tumor without microparticle carriers. Microparticle treatment prolonged the lives mice with melanoma. Of five mice that had been treated with particles alone (no antibody), all died within 21 days after treatment. In contrast, of the five mice treated with FMS-antibodies, three survived 21 days, and two were still alive at 34 days, when the experiment ended.

"We want to understand the mechanism, because not much is known about how the slowly leaked antibodies induce changes in the immune system or in the microenvironment of the tumor," said senior author Dr. Karl Erik Hellstrom, professor of pathology at the University of Washington.

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