Effect of the molecular weight of poly(ethylene glycol) used as emulsifier on α-chymotrypsin stability upon encapsulation in PLGA microspheres

Abstract

Poly(ethylene glycol) (PEG) was used as emulsifier to prepare alpha-chymotrypsin-loaded poly(lactic-co-glycolic) acid (PLGA) microspheres by a solid-in-oil-in-water (s/o/w) technique. The effect of the molecular weight of PEG on protein stability was assessed by the determination of the amount of insoluble aggregates, the activity loss and the magnitude of structural perturbations. In addition, the effect of the molecular weight of PEG on the encapsulation efficiency, microsphere characteristics and release kinetics was investigated. X-ray photoelectron spectroscopy (XPS) was employed to characterize the surface chemistry of the microspheres. Microspheres were prepared using PEG with molecular weight of 6,000, 8,000, 10,000, 12,000 and 20,000. The results indicate that PEG 20,000 was the most effective emulsifier when producing alpha-chymotrypsin-loaded microspheres with respect to protein stability. The aggregate formation was decreased from 18% to 3%; the protein inactivation and the encapsulation-induced structural perturbations were largely prevented. XPS confirmed that PEG was largely located on the surface of microspheres. The molecular weight of PEG affected the microspheres' characteristics and release kinetics. Microspheres prepared with PEG 20,000 showed improved encapsulation efficiency (80%) and a continuous release (for 50 days) with the lowest amount of initial release. It is demonstrated that the selection of the optimum molecular weight of PEG when used as emulsifier in the preparation of microspheres is a critical factor in the development of sustained-release formulations for the delivery of proteins.

Targeted Delivery of PSC-RANTES for HIV-1 Prevention using Biodegradable Nanoparticles

“…Nanoparticles composed of biodegradable polymers such as PLGA are commonly used due to their ability to be reabsorbed by the body and to show lower toxicity than non-degradable polymers (29,30). Additionally, work with PLGA nanoparticles was shown to reduce immunogenic response, increase blood circulation lifetimes, protect against degradation, enhance tissue penetration, and provide sustained drug release (31–38). The sub-micron size of nanoparticles allows them to penetrate into the tissue through interstitial spaces to be readily taken up by the cells (39).…”

Stabilization of Proteins by Nanoencapsulation in Sugar–Glass for Tissue Engineering and Drug Delivery Applications

“…A number of approaches have been developed to ameliorate the impact of individual stresses in emulsion‐based methods. These include the use of interface stabilizers,7, 8 protein crystalization,9 and covalent protein modification 10. Ideally a single approach would protect against all these stresses, yielding excellent encapsulation efficiency and storage stability, while giving burst‐free sustained release for any protein and polymer system of interest.…”

Solid-in-oil dispersion: A novel core technology for drug delivery systems

“…In their report, the secondary structure of BSA, especially ␤-sheet content, was not disrupted by the encapsulation procedure (Castellanos et al, 2001a,b). Moreover, the effects of addition or covalent modification by PEG or cyclodextrins were investigated using ␣ or ␥-chymotrypsin as model proteins (Castellanos et al, , 2005a(Castellanos et al, , 2005b(Castellanos et al, , 2006Castellanos and Griebenow, 2003;Perez et al, 2002). A similar method has been used to prepare a PLGA microsphere containing vascular endothelial growth factor (Kim and Burgess, 2002), human growth hormone (hGH) (Takada et al, 2003), insulin (Kang and Singh, 2005;Andreas et al, 2011), immunoglobulin G (Wang et al, 2004), glial cell linederived neurotrophic factor (Checa-Casalengua et al, 2011), typical model proteins such as lysozyme, ␣-chymotrypsin, peroxidase and ␤-galactosidase (Giteau et al, 2008), BSA-loaded calcium phosphate nanoparticles (Pitukmanorom et al, 2008), BSA-loaded dextran glassy particles (Yuan et al, 2010), recombinant human granulocyte colony-stimulating factor-loaded glassy sodium hyaluronate particles (Wu et al, 2011), recombinant human erythropoietin and human serum albumin mixture microparticles (He et al, 2011), BSA-or ␤-galactosidasen-loaded dextran nanoparticles , BSA-loaded porous silicon microparticles (Fan et al, 2011) and zinc-BSA nanoparticles (Ma et al, 2012).…”