european journal of pharmaceutical sciences 27 ( 2 0 0 6 ) 27–36 available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/ejps In vivo tumor targeting of tumor necrosis factor--loaded stealth nanoparticles: Effect of MePEG molecular weight and particle size Chao Fang a,b , Bin Shi b , Yuan-Ying Pei b,* , Ming-Huang Hong b , Jiang Wu b , Hong-Zhuan Chen a a Department of Pharmacology, College of Basic Medical Sciences, Shanghai Jiao Tong University, Shanghai 200025, PR China b Department of Pharmaceutics, School of Pharmacy, Fudan University, Shanghai 200032, PR China article info Article history: Received 24 February 2005 Received in revised form 19 July 2005 Accepted 5 August 2005 Available online 16 September 2005 Keywords: Nanoparticles Stealth Tumor necrosis factor- Tumor targeting Long circulating Fixed aqueous layer thickness (FALT) abstract The aim of this study is to reveal the influence of methoxypolyethyleneglycol (MePEG) molecular weight and particle size of stealth nanoparticles on their in vivo tumor tar- geting properties. Three sizes (80, 170 and 240nm) of poly methoxypolyethyleneglycol cyanoacrylate-co-n-hexadecyl cyanoacrylate (PEG-PHDCA) nanoparticles loading recombi- nant human tumor necrosis factor- (rHuTNF-) were prepared at different MePEG molecu- lar weights (MW = 2000, 5000 and 10,000) using double emulsion method. The opsonization in mouse serum was evaluated by Coomassie brilliant blue staining of sodium dode- cyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Phagocytosis was evaluated by incubating 125 I-rHuTNF--loaded nanoparticles with mouse macrophages (RAW264.7). The pharmacokinetics, biodistribution and tumor targeting studies were performed in S-180 tumor-bearing mice. Higher MePEG molecular weight provided thicker fixed aqueous layer thickness (FALT) and smaller particle size offered higher surface MePEG density. The serum protein adsorption and phagocytic uptake were markedly decreased for the nanoparticles with higher MePEG molecular weight or smaller size. The particles (80 nm) made of PEG 5000 - PHDCA, possessing a thicker FALT (5.16nm) and a shortest distance (0.87nm) between two neighboring MePEG chains, showed the strongest capacity of decreasing protein adsorp- tion and phagocytic uptake. These particles extended the half-life of rHuTNF- in S-180 tumor-bearing mice by 24-fold (from 28.2 min to 11.33 h), elevated the rHuTNF- peak con- centration in S-180 tumors by 2.85-fold and increased the area under the intratumoral rHuTNF- concentration curve by 7.44-fold. The results of the present study showed PEG- PHDCA nanoparticles with higher MePEG molecular weight and smaller particle size could achieve higher in vivo tumor targeting efficiency. © 2005 Elsevier B.V. All rights reserved. ∗ Corresponding author. Tel.: +86 21 54237186. E-mail address: fangchao100@hotmail.com (Y.-Y. Pei). 0928-0987/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.ejps.2005.08.002