ABSTRACT
PURPOSE: To demonstrate the feasibility of a novel macromolecular delivery system for doxorubicin (DOX) which combines pH dependent DOX release with a high molecular weight and biodegradable gelatin carrier. METHODS: DOX was conjugated to gelatin using an acid labile hydrazone bond and a glycylglycine linker. The gelatin-doxorubicin conjugate (G-DOX) was evaluated for hydrazide and DOX content by spectrophotometry, molecular weight by HPLC-SEC, in vitro DOX release at various pH, and cell growth inhibition using EL4 mouse lymphoma and PC3 human prostate cells. RESULTS: G-DOX hydrazide and DOX content was 47% and 5-7%, respectively of theoretical gelatin carboxylic acid sites. During preparation of G-DOX, the molecular weight decreased to 22 kDa. DOX release was 48% in pH 4.8 phosphate buffer, 22% at pH 6.5, but 10% at pH 7.4. The G-DOX IC50 values in EL4 and PC3 cells were 0.26 µM and 0.77 µM, respectively; the latter value 3 times greater than that of free DOX. CONCLUSIONS: A 22 kDa macromolecular DOX conjugate containing 3.4-5.0% w/w DOX has been prepared. The pH dependent drug release in combination with a biodegradable gelatin carrier offer potential therapeutic advantages of enhanced tumor cell localization and reduced systemic toxicities of the drug.
Subject(s)
Antibiotics, Antineoplastic/administration & dosage , Antibiotics, Antineoplastic/pharmacology , Delayed-Action Preparations/chemistry , Doxorubicin/administration & dosage , Doxorubicin/pharmacology , Gelatin/chemistry , Animals , Antibiotics, Antineoplastic/chemistry , Cell Line, Tumor , Cell Proliferation/drug effects , Doxorubicin/chemistry , Humans , Male , Mice , Neoplasms/drug therapyABSTRACT
The purpose of this study was to examine doxorubicin adsorption in polypropylene containers as a function of pH and drug concentration based on anecdotal evidence of such adsorption. Doxorubicin loss was first examined in high-performance liquid chromatography (HPLC) glass inserts by UV absorbance to determine appropriate pH and time durations for subsequent analysis. Doxorubicin loss was then investigated in polypropylene microcentrifuge tubes at different pH values and starting drug concentration at 37°C over 48 h using HPLC with fluorescent detection. Doxorubicin concentrations was essentially constant in HPLC glass inserts at pH 4.8 up to 12 h but declined 5% at pH 7.4 by 3 h. The percent doxorubicin adsorption was calculated in polypropylene microcentrifuge tubes from extrapolations to zero time and was the least at pH 4.8, but increased with pH values 6.5 and 7.4, and decreased with drug concentration to reach a maximum adsorption of 45% in 2.0 µg/mL at pH 7.4 and 37°C. Degradation rate constants, ranging from 0.0021 to 0.019 h(-1), also increased with pH in these studies. Determinations of low amounts of doxorubicin in polypropylene containers at pH 7.4 may be underestimated if adsorption and degradation issues are not taken into account.
