Colloids and Surfaces B: Biointerfaces 111 (2013) 460–468 Contents lists available at SciVerse ScienceDirect Colloids and Surfaces B: Biointerfaces jou rn al hom epage: www.elsevier.com/locate/colsurfb Selective encapsulation of hemoproteins from mammalian cells using mesoporous metal oxide nanoparticles Mohamed Khairy a,b , Sherif A. El-Safty a,b,∗ a National Institute for Materials Science (NIMS), 1-2-1 Sengen, Tsukuba-shi, Ibaraki-ken 305-0047, Japan b Graduate School for Advanced Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan a r t i c l e i n f o Article history: Received 15 January 2013 Received in revised form 3 June 2013 Accepted 18 June 2013 Available online 2 July 2013 Keywords: Metal oxides Hemoproteins Selective encapsulation Mesoporous Mammalian cells a b s t r a c t A key requirement in successful protein encapsulation is the fabrication of selective protein supercap- tors that are not impeded by the physical shape and three-dimensional hydrodynamics of the protein, exhibit minimal clogging effect but with high protein retention, and with uniformly sized adsorbent pores. We report a novel nanomagnet-selective supercaptor approach in the encapsulation of hemopro- tein from mammalian cells using mesoporous metal oxide nanoparticles (NPs). Different morphologies of mesoporous NiO and Fe 3 O 4 NPs were fabricated. Among these nanoadsorbents, NiO nanoroses (NRs) had higher loading capacity of hemoprotein than NiO nanospheres (NSs) and nanoplatelets (NPLs), or even superparamagnetic Fe 3 O 4 NPs. The key finding of this study was that mesoporous NiO nanomagnet supercaptors show exceptional encapsulation and selective separation of high-concentration Hb from human blood. In this induced-fit separation model, in addition to the heme group distributions and protein-carrier binding energy, the morphology and magnetic properties of NiO NPs had a key function in broadening the controlled immobilization affinity and selectivity of hemoproteins. In addition, ther- modynamics, kinetics, and theoretical studies were carried out to investigate the optimal performance of protein adsorption. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Mesoporous metal oxides have elicited extensive attention because they are promising candidates in a plethora of technolo- gically important disciplines, including catalysis and biocatalysts, nanofiltration, energy generation using fuel cells and solar cells, optical imaging, phototherapy, environmental capture, sensor applications and bioadsorption and encapsulation technology [1–3]. However, these applications require large-scale production, low-cost manufacturing, and controlled physical characteristics such as morphology, porosity, and surface area. Among the vari- eties of mesoporous nanomaterials, magnetic nanoparticles (NPs) with uniform morphology have drawn our attention because such materials are potential candidates in various studies in biology and medicine. Magnetic NPs can be used as antibody carriers and used in drug delivery systems, bimolecular and cell separation, and tissue typing [4–9]. These nanoparticles have the following key features: (1) they have the ability to interact with biological molecules in different ways due to their magnetic features; (2) they offer a large ∗ Corresponding author. Tel.: +81 298592135; fax: +81 298592025. E-mail addresses: sherif.elsafty@nims.go.jp, sherif@aoni.waseda.jp (S.A. El-Safty). exposed surface area without using porous materials, which are often plagued by high mass transfer resistances; (3) they intro- duce a wide variety of surface functionalizations that can serve as versatile platforms for effective manipulation of various bimolec- ular reactions, which is an important factor in proteomics; and (4) they require simple separation of the target compound, support full automation, and provide precise results [9,10]. The adsorption and separation of the target protein from a com- plex solution on a solid surface has a critical function in different disciplines ranging from gene biology, biotechnology, biochemical engineering, biomedicine, and environmental processes [11–13]. Therefore, special attention should be exerted in understanding the fundamental factors that control protein-surface interactions. These factors are imperative in improving the ability to design bio- compatible materials and biotechnological devices [14,15]. Protein loading on solid surfaces is a complex process because it involves numerous binding events, such as conformational changes, hydro- gen bonding, and/or hydrophobic and electrostatic interactions [4–6,16,17]. Surface characteristics, protein properties, and chem- ical environments influence these interactions. In the last few decades, proteins have been separated and purified from tis- sues after expression in bacteria or yeast by different classical techniques including chromatography, gel electrophoresis, ultrafil- tration, microfluidics, and multi-lane channel methods [7]. Among 0927-7765/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.colsurfb.2013.06.037