Dynamic Interfacial Properties of Poly(ethylene glycol)-Modified Ferritin at the Solid/Liquid Interface

Poly(ethylene glycol)-modified ferritins (PEG-ferritins) with various molecular weights were synthesized by the grafting method, and their dynamic interfacial properties at the solid/liquid interface were investigated. The number of PEG grafted to ferritins was controlled by the amount of 1,1′-carbonyldiimidazole-modified PEG adding to the reaction solution. The adsorption kinetics and energy dissipation of PEG-ferritins onto bare Si substrate and amino-modified Si substrate were investigated with a quartz crystal microbalance (QCM) in 10 mM bis-Tris/HCl buffer (pH 5.8), while their morphologies were characterized by scanning electron microscopy (SEM). The adsorption dynamics of PEG-ferritins onto amino-modified Si substrate were quite different from those of unmodified ferritin, which can be reasonably interpreted by the desorption capability of PEG-ferritins on the surface attributed to amphiphilicity and the high-chain mobility of PEG chains

Growth of Giant Two-Dimensional Crystal of Protein Molecules from a Three-Phase Contact Line

A novel method to fabricate a two-dimensional (2D) crystal of protein molecules has been developed. The method enables us to control both the position of nucleation and the direction of the crystal growth. The crystal obtained using a protein molecule, ferritin, was found to be composed of a number of densely packed single crystal domains with an unprecedentedly large size of approximately 100 μm2. This method also reveals characteristic behavior of the spatiotemporal evolution of the crystal; for example, “fusion” of the crystal domains, which is never observed in an ordinary crystal composed of atoms or ions, was demonstrated. Our approach could have potential in fabricating extraordinarily large and highly ordered nanoparticle arrays of organic or inorganic materials

Mechanism Underlying Specificity of Proteins Targeting Inorganic Materials

Adhesion force analysis using atomic force microscopy clearly revealed for the first time the mechanism underlying the specific binding between a titanium surface and ferritin possessing the sequence of Ti-binding peptide in its N-terminal domain. Our results proved that the specific binding is due to double electrostatic bonds between charged residue and surface groups of the substrate. Furthermore, it is also demonstrated that the accretion of surfactant reduces nonspecific interactions, dramatically enhancing the selectivity and specificity of Ti-binding peptide

Thermoresponsive Nanostructured Surfaces Generated by the Langmuir–Schaefer Method Are Suitable for Cell Sheet Fabrication

Thermoresponsive poly­(<i>N</i>-isopropylacrylamide) (PIPAAm)-immobilized surfaces for controlling cell adhesion and detachment were fabricated by the Langmuir–Schaefer method. Block copolymers composed of polystyrene and PIPAAm (St-IPAAms) having various chain lengths and compositions were synthesized by reversible addition–fragmentation chain transfer radical polymerization. The St-IPAAm Langmuir film at an air–water interface was horizontally transferred onto a hydrophobically modified glass substrate while regulating its density. Atomic force microscopy images clearly visualized nanoscaled sea–island structures on the surface. By adjusting both the composition of St-IPAAms and the density of immobilized PIPAAms, a series of thermoresponsive surfaces was prepared to control the strength, rate, and quality of cell adhesion and detachment through changes in temperature across the lower critical solution temperature range of PIPAAm molecules. In addition, a two-dimensional cell structure (cell sheet) was more rapidly recovered on the optimized surfaces than on conventional PIPAAm surfaces. These unique PIPAAm surfaces are suggested to be useful for controlling the strength of cell adhesion and detachment