Preparation and characterization of Tween 80 coated cetylpalmitate nanoparticles for brain drug targeting.

Purpose. To produce spray-dried alginate particles for the preparation of alginate/PLGA composite microparticles intended for protein encapsulation and delivery. Methods. A sodium alginate solution was spray-dried, at an inlet temperature of 135°C and a pump flow rate of 8% (2 ml/min), to obtain sodium alginate microparticles. Calcium alginate particles were produced by dropping an acetonitrile alginate particle suspension in a calcium chloride solution. The mixture was maintained under stirring for 10 minutes to allow gelation and the particles were recovered by centrifugation. Bovine insulin absorption studies (10mM glycine buffer, pH 2.8) were carried out in order to determine the exact amount of insulin absorbable by the alginate particles. Insulin solutions were assayed by RPHPLC. Insulin loaded composite microparticle were prepared by the solvent diffusion evaporation method and the influence of the theoretical loading on encapsulation efficiency and stability has been studied. Actual loading was determined by micro-BCA protein assay (total insulin) and by RP-HPLC (native insulin). RP-HPLC analysis were carried out in an isocratic manner (1 ml/min at 40°C) using 74% of 0.2M sulfate buffer pH 2.3 and 26% acetonitrile. Results. Sodium alginate particles were produced with a good recovery and characterized by a volume mean diameter around 8 μm. After gelation, alginate particles were characterized by a volume mean diameter around 7 μm, dimensions suitable for the encapsulation in PLGA microparticles. Alginate particles showed to absorb until around 50% (w/w) of bovine insulin with four hours of incubation. Insulin loaded composite microparticles were characterized by an encapsulation efficiency of 44, 59 and 66% when working with a theoretical loading of 7.4, 9.1 and 10.7%, respectively. Bovine insulin native structure was very well preserved by the presence of alginate hydrogel, since 98, 86 and 81% of the peptide was found in its native form for 7.4, 9.1 and 10.7% theoretical loading, respectively. Conclusion. Alginate showed good protective properties during insulin encapsulation allowing a good encapsulation efficiency. The influence of alginate particles on the release behavior will be investigated as well.