Porous-wall hollow glass microspheres are a novel form of glass material consisting of a 10 to 100 micron-diameter hollow central cavity surrounded by a 1 micron-thick silica shell. A tortuous network of nanometer-scale channels completely penetrates the shell.

We show here that these channels promote size-dependent uptake and controlled release of biological molecules in the 3–8 nm range, including antibodies and a modified single-chain antibody variable fragment (scFv). In addition, a 6 nm (70 kDa) dextran can be used to gate the porous walls, facilitating controlled release of an internalized small interfering RNA.

Porous-wall hollow glass microspheres remained in place after mouse intratumoral injection, suggesting a possible application for the delivery of anti-cancer drugs. The combination of a hollow central cavity that can carry soluble therapeutic agents with mesoporous walls for controlled release is a unique characteristic that distinguishes porous-wall hollow glass microspheres from other glass materials for biomedical applications.

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