RESEARCH PAPER Nanoparticles Based on a Hydrophilic Polyester with a Sheddable PEG Coating for Protein Delivery Neda Samadi & Mies J. van Steenbergen & Joep B. van den Dikkenberg & Tina Vermonden & Cornelus F. van Nostrum & Maryam Amidi & Wim E. Hennink Received: 15 January 2014 /Accepted: 27 February 2014 # Springer Science+Business Media New York 2014 ABSTRACT Purpose To investigate the effect of polyethylene glycol (PEG) in nanoparticles based on blends of hydroxylated aliphatic polyester, poly(D,L-lactic-co-glycolic-co-hydroxymethyl glycolic acid) (PLGHMGA) and PEG-PLGHMGA block copolymers on their degradation and release behavior. Methods Protein-loaded nanoparticles were prepared with blends of varying ratios of PEG-PLGHMGA (molecular weight of PEG 2,000 and 5,000 Da) and PLGHMGA, by a double emulsion method with or without using poly(vinyl alcohol) (PVA) as surfactant. Bovine serum albumin and lysozyme were used as model proteins. Results PEGylated particles prepared without PVA had a zeta potential ranging from ~ -3 to ~-35 mV and size ranging from ~200 to ~600 nm that were significantly dependent on the content and type of PEG-block copolymer. The encapsulation efficiency of the two proteins however was very low (<30%) and the particles rapidly released their content in a few days. In contrast, all formulations prepared with PVA showed almost similar particle properties (size: ~250 nm, zeta potential: ~-1 mV), while loading efficiency for both model proteins was rather high (80– 90%). Unexpectedly, independent of the type of formulation, the nanoparticles had nearly the same release and degradation char- acteristics. NMR analysis showed almost a complete removal of PEG in 5 days which explains these marginal differences. Conclusions Protein release and particle degradation are not substantially influenced by the content of PEG, likely because of the fast shedding of the PEG blocks. These PEG shedding particles are interesting system for intracellular delivery of drugs. KEY WORDS biodegradable . nanoparticles . polyethylene glycol (PEG) . protein release . shedding INTRODUCTION Biodegradable nanoparticles based on aliphatic polyes- ters are presently under investigation as injectable col- loidal systems for the targeted (intracellular) delivery of classical drugs as well as biotherapeutics (1–3). It is well known that to improve the biodistribution of nanopar- ticles, e.g. tumor accumulation, their surface properties should be modified to give them a stealth character. One of the most commonly used strategies to increase the circulation half-life of i.v. injected nanoparticles is to cover the surface with a hydrophilic, flexible and non- ionic polymer, such as poly(ethylene glycol) (PEG) (4–6). The PEG coating, however, may obstruct the entry of nanoparticles into the target cells (7). But even when the nanoparticles are endocytosed, the PEG layer may ad- versely affect endosomal escape (8). The therapeutic efficacy of sterically stabilized nanoparticles can be en- hanced by means of PEG shedding after arrival of the nanoparticles at the target site. Different approaches have been used for the design of PEG sheddable nano- particles such as shedding by degradation of the coating material itself (9); shedding by cleavage of a chemical bond between the stabilizing polymer and its anchor (7) and shedding by spontaneous extraction of stealth poly- mer from the nanoparticles (10). The shedding kinetics should however be optimized: when the stealth coating is shed too fast, the circulation kinetics will be negative- ly affected whereas a too slow shedding will hamper cellular uptake. In addition to providing a protective hydrophilic layer, some other characteristics of the nanoparticles such as particle surface charge and geometry, drug loading and release Electronic supplementary material The online version of this article (doi:10.1007/s11095-014-1355-x) contains supplementary material, which is available to authorized users. N. Samadi : M. J. van Steenbergen : J. B. van den Dikkenberg : T. Vermonden : C. F. van Nostrum : M. Amidi : W. E. Hennink (*) Department of Pharmaceutics Utrecht Institute for Pharmaceutical Sciences Utrecht University, 3584 CG Utrecht, The Netherlands e-mail: W.E.Hennink@uu.nl Pharm Res DOI 10.1007/s11095-014-1355-x