Shuichi Arakawa

Biomineralization of hydroxyapatite on DNA molecules in SBF: morphological features and computer simulation.

The hydroxyapatite (HA) formation on the DNA molecules in SBF was examined. After immersion for four weeks in SBF at 36.5 °C, the HA crystallites of ~1-14 μm in diameter grew on the surface of DNA molecules. Various morphologies were successfully observed through scanning electron microscopy analysis. The Ca/P mol ratio (1.1-1.5) in HA was estimated by energy dispersive X-ray analysis. Original peaks of both of DNA and HA were characterized by Fourier transform infrared spectroscopy. The molecular orbital computer simulation has been used to probe the interaction of DNA with two charge-balancing ions, i.e., CaOH(+) and CaH2PO4(+). The adsorption enthalpy of the two ions on ds-DNA and/or ss-DNA having large negative value (~ -60 kcal/mol per charge-balancing ion) was the evidence for the interface in mineralization of HA in SBF.

Preparation and characterization of DNA/allophane composite hydrogels

The preparation and characterization of the composite hydrogels based on double-stranded deoxyribonucleic acid (DNA) and natural allophane (AK70) were reported. To understand the propensity of the natural allophane to adsorb the DNA molecules, using zeta potential measurement, Fourier transform infrared spectroscopy (FTIR) and electrophoresis analyses assessed the adsorption characteristics. The freeze-dried DNA/AK70 hydrogels were demonstrated that the DNA bundle structure with a width of ∼2μm and a length of ∼15-20μm was wrapped around the clustered allophane particles as revealed by FE-SEM/EDX analysis. The incorporation of AK70 in hydrogels induced the increase in the enthalpy of the helix-coil transition of DNA duplex due to the restricted molecular motions of the DNA duplex facilitated by the interaction between the phosphate groups of DNA and the protonated (+)(OH2)Al(OH2) groups on the wall perforations of the allophane.

Phase separation behavior and magnetic properties of Li(FexAl1–x)5O8solid solutions

Phase separation behaviour and magnetic properties of Li(FexAl1–x)5O8 solid solutions have been investigated. A single-phase Li(Fe0.5Al0.5)5O8 solid solution, which was quenched from 1250 °C, separated into Fe-rich and Al-rich solid solution phases with a continuous compositional variation when it was annealed at 1000 and 950 °C inside the chemical spinodal estimated using the theory of Cook and Hilliard. On the other hand, a Li(Fe0.68Al0.32)5O8 solid solution showed binodal-type phase separation after an incubation period of 200 h at 1000 °C inside the miscibility gap but outside the spinodal. The coercive force of the Li(Fe0.5Al0.5)5O8 solid solution spinodally decomposed at 1000 °C increased to 7.2 kA m–1, which was about 9 times as large as that before annealing. Annealing of the Li(Fe0.5Al0.5)5O8 solid solution at 950 °C raised the coercive force to 8.6 kA m–1. The increase in the coercive force is possibly due to the modulated structure which is characteristic of spinodally decomposed ceramics. The coercive force of the Li(Fe0.68Al0.32)5O8 solid solution remained constant even after it was annealed at 1000 °C for 200 h to decompose it binodally.

CHAPTER 2:Smart Surfaces Chemistry and Coating Materials for Tissue Engineering

In this chapter, we provide an in-depth discussion of nanoscale surfaces based on RGD nanospacing and surface topography for tissue engineering scaffolds over the last decade. The complex interrelation between focal adhesion, traction forces, and nanoscale ligand patterns are discussed. In addition, current strategies used in scaffold-mediated delivery as reservoirs in therapeutics are described. These methods involve the use of anticancer drugs, DNA and proteins to achieve multi-modal release. A new research area to broaden our understanding of scaffold-mediated delivery is presented.