Effect of cationic grafted copolymer structure on the encapsulation of bovine serum albumin

Abstract

The aim of the present study was to evaluate a library of poly-L-lysine (PLL)-graft (g)-polyethylene glycol (PEG) copolymers for the ability to encapsulate effectively a model protein, bovine serum albumin (BSA), and to characterize the stability and protein function of the resulting nanoparticle. A library of nine grafted copolymers was produced by varying PLL molecular weight and PEG grafting ratio. Electrostatic self-assembly of the protein and the grafted copolymer drove encapsulation. The formation of protein/polymer nanoparticles with a core/shell structure was confirmed using PAGE, dynamic light scattering, and electron microscopy. Encapsulation of the BSA into nanoparticles was strongly dependent on the copolymer-to-protein mass ratio, PEG grafting ratio, and PLL molecular weight. A copolymer-to-protein mass ratio of 7:1 and higher was generally required for high levels of encapsulation, and under these conditions, no loss of protein activity was observed. Copolymer characteristics also influenced nanoparticle resistance to polyanions and protease degradation. The results indicate that a copolymer of 15-30 kDa PLL, with a PEG grafting ratio of 10:1, is most promising for protein delivery.

Intracellular Delivery of Glucose Oxidase for Enhanced Cytotoxicity toward PSMA‐Expressing Prostate Cancer Cells

“…These results indicate GOX readily associated with PLL‐ g ‐PEG into complexes through electrostatic interactions This has similarly been observed for GOX by Kawamura et al using another cationic copolymer, polyethylene glycol‐graft‐poly(allyl amine) . Because our previous studies have found that complexes formed at a 7:1 C:P ratio were more resistant to dissociation than complexes formed at smaller ratios, we proceeded with a C:P ratio of 7:1 for further studies …”

“…Poly‐ l ‐lysine‐grafted‐polyethylene glycol was synthesized as previously described . Briefly, 15 mg of PLL was dissolved in 200 µL of PBS.…”

“…PLL‐ g ‐PEG/GOX complexes were synthesized using previous methods to associate cationic copolymers with proteins . Varying concentrations of PLL‐ g ‐PEG (25 µL) were added to GOX dissolved in PBS (2 mg mL −1 , 25 µL) dropwise, while gently vortexing.…”

“…The physicochemical properties of PLL‐ g ‐PEG/GOX complexes were determined using dynamic light scattering (DLS) to determine the size and phase analysis light scattering (PALS) to determine the surface charge as previously performed by our group . A Brookhaven Instrument Corporation ZetaPALS ζ‐potential analyzer was used for both measurements.…”

“…Complexation with PEGylated cationic copolymers has been shown to improve several aspects of biomacromolecule delivery, including resistance to heat denaturation, protease degradation, stimuli‐responsive delivery, as well as the ability to functionalize proteins and DNA without potentially deactivating covalent modifications . This approach has been successfully applied toward the encapsulation of proteins such as bovine serum albumin, butyrylcholinesterase, lysozyme, insulin, superoxide dismutase, and others to modify how they are delivered to cells . Additionally, PEGylated cationic copolymers have been shown to permit proteins, as well as DNA, to cross the cell membrane, enabling delivered proteins to have activity within the intracellular space …”