Development of dextran nanoparticles for stabilizing delicate proteins

Abstract

One of the most challenging problems in the development of protein pharmaceuticals is to deal with stabilities of proteins due to its complicated structures. This study aims to develop a novel approach to stabilize and encapsulate proteins into dextran nanoparticles without contacting the interface between the aqueous phase and the organic phase. The bovine serum albumin, granulocyte-macrophage colony-stimulating factor (GM-CSF), granulocyte colony-stimulating factor (G-CSF), β-galactosidase, and myoglobin were selected as model proteins. The proteins were added into an aqueous solution containing the dextran and polyethylene glycol, and then encapsulated into dextran nanoparticles by aqueous-aqueous freezing-induced phase separation. The encapsulation efficiency and recovery of dextran nanoparticles were determined. The dextran nanoparticles loaded with proteins were characterized by scanning electron microscopy and particle size analysis. The protein aggregation was determined by size-exclusion chromatography-high-performance chromatography, and the bioactivity of proteins recovered during formulation steps was determined. The bioactivity of GM-CSF, G-CSF, and β-galactosidase were examined by the proliferation of TF-1 cell, NSF-60 cell, and ortho-nitrophenyl-β-galactoside assay, respectively. The results of bioactivity recovered show that this novel dextran nanoparticle can preserve the protein's bioactivity during the preparation process. LysoSensor™ Yellow/Blue dextran, a pH-sensitive indicator with fluorescence excited at two channels, was encapsulated into dextran nanoparticles to investigate the ability of dextran nanoparticles to resist the acidic microenvironment (pH < 2.5). The result shows that the dextran nanoparticles attenuate the acidic microenvironment in the poly (lactic-co-glycolic acid) microsphere by means of the dilution effect. These novel dextran nanoparticles provided an appealing approach to stabilize the delicate proteins for administration.

Figure 1

The formulation strategy of fabricating the dextran nanoparticles loaded with proteins.

Figure 2

An SEM photo of dextran nanoparticles loaded with BSA.

Figure 3

The size distribution of dextran nanoparticles loaded with BSA.

Figure 4

SEC-HPLC of model proteins recovered from standard solution (a), dextran nanoparticle (b), and W/O emulsion (c).

Figure 5

Bioactivity of model proteins recovered from standard solution, dextran nanoparticle, and W/O emulsion. GM-CSF (A), G-CSF (B), β-galactosidase (C).

Figure 6

The relation of fluorescent intensity ratio and pH. Assay mechanism (A), standard curve of fluorescent intensity ratios of the LysoSensor™ Yellow/Blue dextran vs. pH (B), fluorescence image of dextran nanoparticle taken at λem = 521,452 nm (C).

Figure 7

Fluorescent image of LysoSensor™ Yellow/Blue dextran-loaded PLGA microspheres. λem = 521,452 nm during the in vitro release period. Dextran nanoparticles loaded in PLGA microsphere (A), the controlled LysoSensor™ Yellow/Blue dextran solution loaded in PLGA microsphere by traditional W/O/W method (B).