The engineers' early tests with a protein solution suggest that supercritical CO2 may leave medicines intact.

They applied a coating of the protein solution onto dime-sized plastic disks with a cotton swab, and placed the disks in a glass tank, which they then filled with supercritical CO2. The proteins contained a fluorescent biomarker, so the researchers were able to track how well the proteins penetrated the plastic by examining cross-sections of the material under a microscope in ultraviolet light.

The microscope showed that the proteins survived the embedding process, and formed a layer 30 micrometers, or millionths of a meter, beneath the surface of the plastic.

Although the plastic -- polymethylmethacrylate, or PMMA -- was undamaged by the procedure, the interior of the disks foamed up into a Swiss cheese-like texture, with voids opening inside. The faster the engineers turned off the high-pressure CO2, the foamier the material became. Lowering the pressure slowly had the opposite effect.

Tomasko envisions that such voids within an implant could come in handy for holding extra quantities of a drug for long-term therapy.

Today, medical implants are used for mechanical support where tissue or bone has been removed. The researchers' vision is to "piggyback" drug delivery onto this mechanical function. The implant may be impregnated with drugs to prevent inflammation or infection following surgery. Or, in cases where a patient has had bone surgically removed as part of a treatment for cancer, doctors may also need to dispense anti-tumor agents from the implant for a longer period, Tomasko explained.

He's been working with David Powell, clinical assistant professor of otolaryngology, to investigate the potential use of such implants for patients who've had facial surgery.

Since completing their initial study, the engineers have begun using a porous glass disk to dispense protein solution onto t
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Contact: David Tomasko
Tomasko.1@osu.edu
614-292-4249
Ohio State University
23-Mar-2004