October 31, 2011 — Drugs conjugated to cationic polymeric nanoparticles might be able to form cross-linked hydrogels with hyaluronic acid in the synovial fluid once they are injected into the knee joint, and this could generate a sort of "slow release" sponge inside the joint that could prolong the treatment duration of pain-relieving osteoarthritis (OA) drugs, according to data reported in a poster presentation at the 2011 American Association of Pharmaceutical Scientists annual meeting.
Lead researcher Michael Morgen, PhD, director of new technology development at Bend Research in Oregon, concluded, "This study demonstrates the feasibility of using a cross-linked hydrogel formulation containing cationic polymeric nanoparticles to increase the retention time in the knee joint for indications such as [OA]."
Dr. Morgen and colleagues tested the concept in an in vitro study using a fluorescently labeled therapeutic peptide, and in vivo using fluorescently labeled polymeric nanoparticles injected into the knee joints of rats. Retention of the nanoparticles in the rat knees was monitored by near-infrared fluorescence molecular tomography.
The researchers found that release of the nanoparticles from the hydrogels in vitro was 20% to 25% per week, and that 70% of the test peptide was retained in the rat knee joints at 7 days.
"Current delivery methods do not maintain the drug in the knee for very long, which limits the effectiveness of therapeutic agents," Dr. Morgen said in a press statement. "We hope that this type of sustained release technology, when used with current or new [OA] drugs, will allow patients to be effectively treated with drug injections every three months instead of once a week."
Dr. Morgen is an employee of Bend Research, Inc. Other authors are employed by Pfizer, Inc.
American Association of Pharmaceutical Scientists Annual Meeting: Abstract W4155. Presented October 26, 2011.
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