Determination of protein loading in biodegradable polymer microspheres containing tetanus toxoid
Abstract
Various methods to determine loading of vaccine in biodegradable polymer microspheres encapsulating tetanus toxoid were evaluated. The microspheres were composed of poly (D-lactic acid) (PLA) and poly (DL-lactic-co-glycolic acid) (PLGA). Dissolution of microspheres in organic solvents such as methylene chloride, chloroform, or dimethyl sulfoxide and extraction of vaccine antigen or total protein with phosphate buffered saline gave variable results which depended upon the characteristics of the microspheres, such as type of polymer, excipients used in the microspheres and formulation conditions. Microspheres made from low molecular weight PLGA polymer and showing a large burst release exhibited up to 25% extraction of antigen whereas microspheres made from PLA microspheres with low burst release showed < 1% extraction. Extraction of total protein with 0.1 N NaOH and 5% sodium dodecyl sulfate showed results similar to those obtained with organic solvent extraction method. Partial digestion of microspheres with 6 N HCl at 60 degrees C for 20 h resulted in approximately 30% loss in TT protein by micro-bicinchoninic acid (BCA) assay. The major problem with this method was strong reactions in the micro-BCA assay of stabilizers, parti...Continue Reading
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Diphtheria and tetanus toxoid microencapsulation into conventional and end-group alkylated PLA/PLGAs
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