Production and characterization of core-shell biopolymer vehicles for multiple delivery strategies

FIORAMONTI, SA; PEREZ, AA; ARINGOLI, EE; SANTIAGO, LG

Córdoba

Congreso; 1ra Reunión Internacional de Ciencias Farmacéuticas - RICiFa; 2010

Universidad Nacional de Córdoba, The American Association of Pharmaceutical Scientists (AAPS)

INTRODUCTION: In the pharmaceutical sector, there are many potential applications for nano and microparticles developed with engineered biomaterials (proteins and polysaccharides). These particles could be used to encapsulate, protect, and deliver functional agents such as bioactive peptides, proteins, enzymes or lipophilic drugs (1,2). In this contribution, experimental information about the preparation and molecular characterization of core-shell biopolymer particles produced by electrostatic deposition of an anionic polysaccharide (sodium alginate, SA) on the surface of soluble protein aggregates (heat-denatured whey protein isolate, hd-WPI) will be presented. MATERIALS AND METHODS: Whey protein isolate (WPI) was provided from Davisco (Minnesota, USA), and low viscosity sodium alginate (SA) was supplied by Cargill (Buenos Aires, Argentina). WPI aqueous solutions (6.0% wt) were heat treated over the temperature range 55-85ºC. The incidence of thermal treatment on the hd-WPI aggregates formation was monitored using a set of complementary spectroscopic techniques: UV/Vis absorption (3), intrinsic and extrinsic fluorescence (4). Polysaccharide electrostatic deposition on the surface of the hd-WPI aggregates (core-shell particles formation) was performed at pH 4.0. The influence of protein-polysaccharide ratio, Pr:Ps (1:1-6:1), on molecular structure of the core-shell biopolymer particles was studied spectroscopically at 0.3% wt total biopolymer concentration. On the other hand, in order to determine the macroscopic phase behavior (cosolubility, complexation and coacervation) of aqueous mixed systems as a function of pH (6.0-3.0), transmittance studies were performed (5). In all cases, the results were compared with their respective controls (thermally untreated WPI). Analysis of variance (ANOVA) was carried out, and the statistical differences (p>0.05) were determined using the LSD test. RESULTS: The hd-WPI aggregates formation was observed at the highest heating temperature (85ºC) as it can be deduced from: (i) an increment in the aqueous system turbidity, (ii) changes in protein conformation (increased flexibility and molecular rearrangement), and (iii) a greater exposure of protein hydrophobic patches. SA electrostatic deposition on the surface of the hd-WPI aggregates had a great impact on the core-shell particles formation depending on the magnitude of Pr:Ps. The increase in Pr:Ps value caused: (i) an increased turbidity of mixed systems, and (ii) occlusion of protein surface hydrophobic patches. Transmittance studies revealed that SA-hd-WPI system mixed at 4:1 ratio showed a typical behaviour (soluble complex formation followed by an associative phase separation, i.e. coacervation) at pH values of 4.3 and 3.3, respectively. However, for the other evaluated systems, the onset of complex coacervation could not be determined experimentally possibly due to cold-set gelation of SA-hd-WPI mixed systems. CONCLUSIONS: Results derived from this research could be useful to determine structural and environmental (pH, Pr:Ps) conditions in order to: (i) control polysaccharide electrostatic deposition on the surface of soluble protein aggregates (ii) develop core-shell biopolymer particles with specific characteristics and multiple applications. The core-shell biopolymer vehicles prepared in this work could be used as drug carriers and/or as delivery systems of heat insensitive lipophilic agents. ACKNOWLEDGEMENTS: Authors would like to thank the financial support of CAI+D-2009 tipo II PI 57-283 project.