Nanoparticle based protein delivery systems provide an attractive option to deliver protein molecules for extended period of time. However, most therapeutic proteins undergo denaturation and aggregation following their contact with a hydrophobic surface. To gain a better understanding of the denaturation mechanism, it is essential to investigate the adsorption of proteins at solid/liquid interfaces, and the interfacial activity and stability of proteins in a characterized model. In order to understand the degree and mechanism structural changes in a protein following its interaction with hydrophobic and hydrophilic surfaces, recombinant human growth hormone (rhGH) was used as a model protein. A series of studies of the interaction of rhGH with zwitterionic and negatively charged polystyrene nanoparticles, and biodegradable poly (D,L-lactic-co-glycolic acid) (PLGA) were carried out to study the adsorption behavior of rhGH on these surfaces. Adsorption of recombinant human growth hormone on zwitterionic polystyrene nanoparticles (~200 nm) with both carboxyl and amino groups was investigated at a variety of pH values in the presence of competing proteins, competing surfactants, or polymers. The adsorption of rhGH on zwitterionic nanoparticle surface was reduced by bovine serum albumin (BSA), pluronic F68, tween-20, and PEG400 at pH 4, 5.3 and 7. Desorption results of r-hGH indicated that competing protein BSA and surfactants may facilitate desorption from nanoparticle surfaces, due to the reversible adsorption of modified polystyrene nanoparticle surfaces. There was an unanticipated increase of rhGH adsorption on zwitterionic particles with β-casein as a competing protein, which was explained by the interaction of rhGH and β-casein in solution experiments, and the formation of rhGH-β-casein complexes or aggregates. However, BSA had no interaction with r-hGH to form aggregates in solution.
The reversible adsorption coating of polystyrene nanoparticles functionalized with coupling proteins may cover nonspecific binding sites, reducing hydrophobicity and immunogenicity by modifying the nanoparticle surface with protein-nanoparticle coronas. The adsorption of rhGH onto negatively charged polystyrene nanoparticles (~200 nm) precoated with coupling proteins indicated that r-hGH displaced BSA, β-casein, gelatin and transferrin from the polystyrene nanoparticle surface (PS-COOH). The adsorbed amounts of rhGH on polystyrene-COOH particles pre-coated with BSA, β- casein, gelatin and transferrin were higher than those in lysozyme coated PS-COOH. This indicated a stronger interaction of NP-COOH with lysozyme than with BSA, β-casein, gelatin and transferrin. As a biocompatible and biodegradable copolymer for protein delivery systems, PLGA nanoparticles (199 nm, with carboxyl end group) were prepared by the Water/Oil/Water double emulsion solvent evaporation method. The adsorption of rhGH onto PLGA was found to be high, at pH 4.0 (close to the pI of the carboxylic acid group on the PLGA polymer) and pH 5.3 (rhGH pI= 5.3). With the increase of BSA concentrations, adsorption of rhGH to PLGA nanoparticles decreased at pH 4.0 and 5.3. Adsorption of rhGH onto PLGA particles was unaffected in the presence of either surfactant at pH 5.3 and 4.0, but significantly increased in the presence of both surfactants at pH 7.2 (PLGA negatively charged).
|School:||University of the Sciences in Philadelphia|
|School Location:||United States -- Pennsylvania|
|Source:||DAI-B 78/08(E), Dissertation Abstracts International|
|Subjects:||Biochemistry, Pharmacy sciences|
|Keywords:||Adsorption, Casein, Nanoparticles, Polystyrene|
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