The Influence of Surface Treatment by Hydrogenation on the Biocompatibility of Different Hydroxyapatite Materials

The influence of hydrogenation on the biocompatibility of different hydroxyapatite (HAP) materials was tested. Materials consisted of pure HAP, HAP substituted with manganese (Mn+2) and with magnesium (Mg+2) - all axially pressed and conventionally sintered for 2 h at 1200 degrees C; pure HAP isostatic pressed and sintered by a microwave technique for 15 min at temperature of 1200 degrees C. Biocompatibility was compared by enumeration of the number of osteoblast-like cells to the materials before and after hydrogenation. Obtained results show that the osteoblastic cells demonstrated a higher ability to attach to HAP if its surface was negatively charged. Hydrogenation altered the surface potential; HAP substituted with manganese - HAP(Mn) and with magnesium - HAP(Mg) demonstrated the highest ability to engineer the charge

The Influence of Surface Treatment by Hydrogenation on the Biocompatibility of Different Hydroxyapatite Materials

The influence of hydrogenation on the biocompatibility of different hydroxyapatite (HAP) materials was tested. Materials consisted of pure HAP, HAP substituted with manganese (Mn+2) and with magnesium (Mg+2) – all axially pressed and conventionally sintered for 2 h at 1200 °C; pure HAP isostatic pressed and sintered by a microwave technique for 15 min at temperature of 1200 °C. Biocompatibility was compared by enumeration of the number of osteoblast-like cells to the materials before and after hydrogenation. Obtained results show that the osteoblastic cells demonstrated a higher ability to attach to HAP if its surface was negatively charged. Hydrogenation altered the surface potential; HAP substituted with manganese – HAP(Mn) and with magnesium – HAP(Mg) demonstrated the highest ability to engineer the charge

Computational and Experimental Studies of Size and Shape Related Physical Properties of Hydroxyapatite Nanoparticles

In this work, the properties of hydroxyapatite (HAP) nanoparticles (NPs) have been studied both theoretically and experimentally focusing on computational analysis. HAP is widely used to fabricate implants, for drug delivery, etc. The physical properties of the nanosized HAP particles play an important role in the interaction with cells in the human body and are of great interest. Computer simulation was employed to understand the properties of HAP clusters (Ca(5)(PO(4))(3)OH) including formation energies, dipole moments and polarization (surface charges) by molecular mechanics (MM + , OPLS) and mostly by quantum semi-empirical Hartree-Fock (PM3) methods. The size of the simulated cluster is found to affect its dipole moment, polarization, and, finally, the electron work function- ϕ. These parameters depend on the concentration of hydrogen atoms H (or protons) at the surface. Values of ϕ were experimentally estimated via photoelectron emission measurements. The magnitude of ϕ was demonstrated to have a positive correlation on sizes. The NPs demonstrated a capability to be gathered within conglomerates. This property is confirmed by the calculated data for various sizes. Their sizes have a positive correlation on ϕ by the native particles. The main results show that the distributions of dipole moments have very different space orientations (along the OX, OY and OZ axes, the OZ axis is oriented along the OH column) and change with the addition of hydrogen atoms, which saturate the broken hydrogen bonds. This electrical property of NP leads to different behaviors and motions with consequent aggregation: (1) for the case of NPs having dipole moment oriented preferably perpendicular to the OZ axis (with more hydrogen bonds saturated by added H)-the HAP NP aggregates with hexagonal orientation and forms a wider and more spherical shape (sphere-like or bundle-like); (2) for the case of NPs having dipole moment oriented along the OZ axis (as is the case in the absence of added protons or non-saturated hydrogen bonds)-the NPs firstly rotated and oriented along this axis to form the most elongated cylindrical shape (rod-like)

Computational Studies of PVDF and P(VDF-TrFE) Nanofilms Polarization during Phase Transition Revealedby Emission Spectroscopy

Electronic structure and self-polarization of P(VDF-TrFE) Langmuir-Blodgett nanofilms according to their thickness, composition and structural conformation under temperature phase transition were analyzed. Both thermo-stimulated exoelectron emission (TSEE) spectroscopy and computational simulation, including quantum-chemical calculations from first principles, were provided. PVDF and composite P(VDF-TrFE) (70:30) molecular chains as Trans and Gauche conformers as well as crystal cells were modeled for these agreed-upon TSEE analyses. The quantum-chemical calculations and the computational simulation were based on the density functional theory (DFT) as well as semi-empirical (PM3) methods. It was demonstrated that the energies of electron states as well as the total energies of the studied PVDF and P(VDFTrFE) molecular clusters during phase transformation influenced electron work function and electron affinity. The performed combined analysis of the TSEE experimental data as well as the computational data of the molecular models showed the effectiveness of that joined approach. TSEE for the first time was in use for contactless measurements of nanofilm polarization and characterizations of the phase transition. The proposed new method can be widely used in nanobiomedicine, particularly in development of new bone bio-implants, including built-in sensors (new smart nanotechnology)

Polarization of poly(vinylidene fluoride) and poly(vinylidene fluoride-trifluoroethylene) thin films revealed by emission spectroscopy with computational simulation during phase transition

The electronic structure and self-polarization of P(VDF-TrFE) Langmuir-Blodgett nanofilms were analyzed under temperature-driven phase transitions, according to their thickness, composition, and structural conformation. Both thermo-stimulated exoelectron emission (TSEE) spectroscopy and computational simulation, including quantum-chemical calculations from first principles, were carried out. PVDF and composite P(VDF-TrFE) (70:30) molecular chains as Trans and Gauche conformers, as well as crystal cells, were modeled for these TSEE analyses. The quantum-chemical calculations and the computational simulation were based on the density functional theory (DFT) as well as semi-empirical (PM3) methods. It was demonstrated that the energy of electron states, as well as the total energies of the studied P(VDF-TrFE) molecular clusters during phase transformation, is influenced by electron work function and electron affinity. Analysis was performed by combining TSEE experimental data with the computational data of the molecular models, demonstrating the effectiveness of this joint approach. For the first time, TSEE was used for contactless measurements of nanofilm polarization, and characterization of the phase transition. The proposed new method can be widely applied in nanobiomedicine, particularly in development of new bone bio-implants, including built-in sensors (new smart nanotechnology). © 2012 American Institute of Physics