Improved dissolution and cytotoxicity of camptothecin incorporated into oxidized-cellulose microspheres prepared by spray drying

Oxidized celluloses (OC) containing 7, 13, and 20% carboxylic content (OC-7, OC-13, and OC-20, respectively) have been converted into aqueous colloidal dispersions and used to prepare microspheres of the antineoplastic agent camptothecin (CPT) by spray drying. Plasticizers used were glycerin, polyethylene glycol 400 (PEG-400), and polyethylene glycol 6000 (PEG-6000). Irrespective of the carboxylic content of OC and the nature of plasticizer employed, the size of microspheres varied from 1.25 ± 0.40 to 1.52 ± 0.47 μm. The release studies in pH 7.4 buffer revealed the dissolution of CPT to be faster from the microsphere formulations than from physical mixtures and free CPT. The times to release 50% CPT (T-50%) from microspheres prepared using OC-7, OC-13, and OC-20 were about 31, 37, and 19 h, respectively. The in vitro cytotoxicity results indicated OC-20/CPT microspheres to be more effective than free CPT against human-derived RPMI-8402 lymphoid and THP-1 myeloid leukemia cell lines. The ED₅₀ values for the OC-20/CPT microspheres and free CPT were 1 × 10^-5 and 0.25 × 10^-1 μg/mL, respectively, against the RPMI-8402 line and 0.5 × 10^-2 and 0.75 μg/mL, respectively, against the THP-1 line. The higher activity of OC-20/CPT microspheres compared to that of the free drug is attributed to increased dissolution of CPT from microspheres.