This work describes a rational approach of hydroxyapatite (HAp) nanosurface modification for graft polymerization of -caprolactone (CL). The ring-opening polymerization of CL on HAp surfaces was carried out using three types of HAp with different surface hydroxyl functionality: unmodified HAp (surface OH), HAp modified with L-lactic acid (secondary OH), and HAp modified with ethylene glycol (primary OH). The grafting efficiency and the amount of grafted poly( -caprolactone) (PCL) were dependent on the nature and steric environment of the hydroxyl groups on the HAp surfaces. Transmission electron microscopy measurements and time-dependent phase monitoring indicated that surface-modified HAp could be more uniformly dispersed in methylene chloride than unmodified HAp, and its colloidal stability increased dramatically as the amount of grafted PCL increased. The nanocomposites of PCL and PCL-grafted HAp showed enhanced tensile strength and toughness, compared with that of unmodified HAp and PCL. Increased interfacial interaction parameters (B σy ) for the composite of PCL and PCLgrafted HAp strongly supported the enhanced mechanical strength of the nanocomposites. The use of HAp modified with a larger amount of PCL was found to be much more effective in improving mechanical properties of the nanocomposites.

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The work describes a simple and convenient process for highly efficient and direct DNA separation with functionalized silica-coated magnetic nanoparticles. Iron oxide magnetic nanoparticles and silica-coated magnetic nanoparticles were prepared uniformly, and the silica coating thickness could be easily controlled in a range from 10 to 50 nm by changing the concentration of silica precursor (TEOS) including controlled magnetic strength and particle size. A change in the surface modification on the nanoparticles was introduced by aminosilanization to enhance the selective DNA separation resulting from electrostatic interaction. The efficiency of the DNA separation was explored via the function of the amino-group numbers, particle size, the amount of the nanoparticles used, and the concentration of NaCl salt. The DNA adsorption yields were high in terms of the amount of triamino-functionalized nanoparticles used, and the average particle size was 25 nm. The adsorption efficiency of aminofunctionalized nanoparticles was the 4-5 times (80-100%) higher compared to silica-coated nanoparticles only (10-20%). DNA desorption efficiency showed an optimum level of over 0.7 M of the NaCl concentration. To elucidate the agglomeration of nanoparticles after electrostatic DNA binding, the Guinier plots were calculated from small-angle X-ray diffractions in a comparison of the results of energy diffraction TEM and confocal laser scanning microscopy. Additionally, the direct separation of human genomic DNA was achieved from human saliva and whole blood with high efficiency.