Cationic b-lactoglobulin nanoparticles as a bioavailability enhancer: Comparison between ethylenediamine and polyethyleneimine as cationizers Zi Teng a , Ying Li a , Yuge Niu b , Yuhong Xu c , Liangli Yu a,b , Qin Wang a,⇑ a Department of Nutrition and Food Science, University of Maryland, 0112 Skinner Building, College Park, MD 20742, United States b Institute of Food and Nutraceutical Science, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, China c School of Pharmacy, Shanghai Jiao Tong University, Shanghai 200240, China article info Article history: Received 30 November 2013 Received in revised form 31 January 2014 Accepted 4 March 2014 Available online 14 March 2014 Keywords: Cationic beta-lactoglobulin (CBLG) Ethylenediamine (EDA) Polyethyleneimine (PEI) Nanoparticles Mucoadhesive properties Secondary structure Protein digestion abstract Cationic b-lactoglobulin (CBLG) was synthesized by two strategies: extensive conjugation of ethylenediamine (EDA) and limited cationization with polyethyleneimine (PEI). Both methods provided CBLG with satisfactory water solubility and resistance to peptic digestion. Compared with EDA-derived CBLG (C-EDA), PEI-derived CBLG (C-PEI) exhibited a higher zeta potential (54.2 compared to 32.4 mV for C-EDA), which resulted in sig- nificantly elevated mucoadhesion (439% and 118% higher than BLG and C-EDA, respectively) in a quartz crys- tal microbalance (QCM) study. In addition, PEI caused reduced conformational disruption on BLG compared to EDA as evidenced by FTIR measurement. This character, together with the steric hindrance provided by PEI, caused a phenomenal reduction in tryptic digestibility by at least 75% compared to C-EDA. In the presence of aqueous acetone, C-PEI aggregated spontaneously into nanoparticles with average size of 140 nm and narrow size distribution. These merits made C-PEI a useful material that provides desirable solubility and protection for orally administrated nutraceuticals or drugs. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction In the past decades, nano-scaled encapsulation and delivery systems have attracted increasing attention as transporters for nutraceuticals or drugs (Augustin & Hemar, 2009; Jahanshahi & Babaei, 2008). Numerous nanoencapsulation strategies and systems have been developed by now, providing target compounds with desirable solubility (Luo & Wang, 2013), satisfactory stability (Guzey & McClements, 2006), controlled release properties (Teng, Luo, & Wang, 2013) and elevated bioavailability (Luo, Teng, Wang, & Wang, 2013). It is generally believed that the success of delivery is highly dependent on the surface properties of the encapsulant, such as charge and hydrophobicity (Futami, Kitazoe, Murata, & Yamada, 2007). Cationic polymers such as chitosan (Agnihotri, Mallikarjuna, & Aminabhavi, 2004), polylysine (Mislick, Baldeschwieler, Kayyem, & Meade, 1995) and lactoferrin (Bengoechea, Jones, Guerrero, & McClements, 2011), have demon- strated significantly higher mucoadhesive capacity and cellular internalization compared with anionic macromolecules. This phenomenon was largely attributed to two factors. The first factor is the affinity of the polycations to the negatively charged glycoproteins, the latter of which are abundant on the membrane of epithelia cells or tissues (e.g., small intestine wall) (Blau, Jubeh, Haupt, & Rubinstein, 2000). The second advantage for cationic encapsulants is their ability to acquire a negatively charged ‘‘corona’’ consisting mostly of serum proteins, which bind strongly to specific receptors on the cell membrane and thus promote the cellular internalization (Wang et al., 2013). A wide array of cationic polymers have been exploited as novel encapsulating systems (Agnihotri et al., 2004; Bengoechea et al., 2011; Qi et al., 2012). However, these polymers are either insoluble at neutral pH (e.g., chitosan) or susceptible to digestion by pepsin or trypsin (e.g., polylysine). Therefore, the protection provided by these materials would be easily diminished when they enter the http://dx.doi.org/10.1016/j.foodchem.2014.03.022 0308-8146/Ó 2014 Elsevier Ltd. All rights reserved. Abbreviations: BLG, beta-lactoglobulin; CBLG, cationic BLG; PEI, polyethylene- imine; EDA, ethylenediamine dihydrochloride; C-EDA, EDA-derived CBLG; C-P600 and C-P1200, CBLG synthesized with PEI-600 and PEI-1200; EDC, N-(3-dimethyl- aminopropyl)-N-ethylcarbodiimide; PSM, porcine stomach mucin; TCA, trichloro- acetic acid; PBS, phosphate buffer saline; QCM, quartz crystal microbalance; MALDI-TOF, matrix assisted laser desorption/ionization time-of-flight mass spec- trometry; SEM, scanning electron microscopy; FT-IR, Fourier transform infrared spectroscopy; FSD, Fourier self deconvolution. ⇑ Corresponding author. Tel.: +1 (301) 405 8421; fax: +1 (301) 314 3313. E-mail address: wangqin@umd.edu (Q. Wang). Food Chemistry 159 (2014) 333–342 Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem