Elution Characteristics of Doxorubicin-loaded Microspheres Differ by Drug-loading Method and Microsphere Size

To examine the loading and elution behavior of doxorubicin and superabsorbent polymer microspheres (SAP-MS) as they relate to particle size and loading techniques.SAP-MS, 30-60 μm and 50-100 μm, were subject to loading 50 mg of doxorubicin from a dry lyophilized state. Doxorubicin loading was performed after prehydration of SAP-MS (one-step method) or serially in two divided administrations (two-step method). Loading rate and elution characteristics were determined after doxorubicin analysis using a high-pressure liquid chromatography (HPLC) assay. All experiments were performed in triplicate.All systems showed the ability to load and elute doxorubicin effectively in the specified time frame (loading 15 minutes to 2 hours and elution 1 hour to 14 days). For the two loading methods, 30-60 μm SAP-MS showed no statistically significant difference in loading rate but a statistically significant difference in cumulative elution at 14 days (19.13 mg vs 17.83 mg, one-step vs two-step; P = .02). For the two loading methods, 50-100 μm SAP-MS showed no statistically significant difference in loading rate and no statistically significant difference in cumulative elution at 14 days (14.87 mg vs 12.77 mg, one-step vs two-step; P = .20).SAP-MS exhibit the ability to load and release doxorubicin. In comparing particle size and loading methods, higher cumulative elution rates were associated with smaller (30-60 μm) particle size and one-step loading. Higher elution from the one-step loading method may be due to release of unbound doxorubicin. Differences in the loading and elution of doxorubicin may depend on the increased surface area of smaller SAP-MS resulting in alterations of behavior of doxorubicin and its interactions with the polymer microspheres.