Aleksandra Szcześ

Synthesis of hydroxyapatite for biomedical applications

The current need for long lasting implants and bone substitutes characterized by biocompatibility, bioactivity and mechanical properties, without the immune rejection is a great challenge for scientists. These bone substitute structures should be prepared for individual patients with all details controlled on the micrometer level. Similarly, nontoxic, biocompatible targeted drug delivery systems which allow controlling the rate and time period of the drug delivery and simultaneously eliminating toxic and side effects on the healthy tissues, are of great interest. Extensive attempts have been made to develop a simple, efficient, and green method to form biofunctional scaffolds and implant coatings possessing the above mentioned significant biocompatibility, bioactivity and mechanical strength. Moreover, that could also serve as drug delivery systems. Hydroxyapatite (HA) which is a major mineral component of vertebrate bones and teeth is an excellent material for these purposes. In this literature review the biologically inspired scaffolds, bone substitutes, implants characterized by mechanical strength and biocompatibility, as well the drug delivery systems, based on hydroxyapatite are discussed.

Influence of impurity ions and magnetic field on the properties of freshly precipitated calcium carbonate

Static magnetic field (MF) effects on the properties of freshly precipitated calcium carbonate have been investigated in the presence of impurity ion Mg(2+), Fe(2+), or SO4(2-). One or both solutions, CaCl2 and Na2CO3, were exposure to MF (0.5T) for 20min at 20 degrees C. Then calcium carbonate was precipitated and zeta potential, pH and light absorbance (lambda=543.3 nm) were measured. The same parameters were also determined for the reference systems in which the solutions were not MF-treated. It was found that in all the systems tested MF effects as determined by the above mentioned parameters had appeared. They depended on the kind of the impurity ion present, as well as on which solution, CaCl2, Na2CO3 or both, MF interacted. For example, if Mg(2+) ion was present in CaCl2 solution, the largest shift in the zeta potential toward higher positive values was observed if Na2CO3 was MF-treated (e.g. from 2 to 12mV) and the same was true as for the maximum in the light absorbance and the pH increase. Interestingly, if (CaCl2 + Mg(2+)) was MF-treated pH of the slurry had decreased. Moreover, a correlation between above mentioned MF effects and the entropy of hydration of the ions has also been found. This points to the changes in the hydrating water structure caused by magnetic field.

Phenol adsorption on closed carbon nanotubes.

We present the results of systematic studies of phenol adsorption on closed commercially available, unmodified carbon nanotubes. Phenol adsorption is determined by the value of tube-specific surface area, the presence of small amount of surface groups influence adsorption only in very small amount. Phenol can be applied as a probe molecule for comparative analysis of tube surface areas. Tube curvature influences adsorption from solution, i.e., we observe increasing adsorption energy (and slower desorption process) with the decrease in tube curvature. This is in full accordance with molecular simulation results.

Surface modification of glass plates and silica particles by phospholipid adsorption

The effect of phospholipid adsorption on the hydrophobicity of glass plates and on the surface charge of silica particles using contact angle and electrophoretic mobility measurements, respectively, was investigated. Deposition of successive statistical monolayers of dipalmitoylphosphatidylcholine (DPPC) on the glass surface showed zig-zag changes of water contact angle, especially on the first few monolayers. This behavior is qualitatively coherent with the oscillations observed in zeta potential values for increasing DPPC concentration. The results indicate that the phospholipid is adsorbed vertically on the plates, exposing alternately its polar head and non-polar hydrocarbon chains in successive layers. On the other hand, experiments conducted on glass plates prior hydrophobized by contact with n-tetradecane suggest that DPPC molecules may to some extent dissolve in the relatively thick n-alkane film and then expose their polar heads over the film surface thus producing polar electron-donor interactions. The effect of both DPPC and dioleoylphosphatidylcholine (DOPC) on the electrokinetic potential of silica spheres confirms adsorption of the phospholipids, leading to a decrease in the (originally negative) zeta potential of silica and even reversal of its sign to positive at acidic pH. Hydrophobic interactions between phospholipid molecules in the medium and those already adsorbed may explain the overcharging. The adsorption of neutral phospholipids may reduce the zeta potential as a consequence of the shift of the electrokinetic or slip plane. The effect is more evident in the case of DOPC, suggesting a less efficient packing of this phospholipid because of the presence of double bonds in its molecule, which in fact is well known.

Stability of binary model membranes--prediction of the liposome stability by the Langmuir monolayer study.

In this paper, usefulness of the Langmuir monolayer study is demonstrated for predictions of the stability of liposomes composed of dipalmitoyl phosphatidylcholine (DPPC) and cholesterol (Chol). Thermodynamic analysis of the surface pressure (π)-area (A) isotherms of the DPPC/Chol systems was performed, which allowed for concluding on miscibility of the components, their molecular packing, and the interactions between molecules. It was found that the most stable system, in which the strongest interactions between molecules occured, was DPPC/Chol at x(Chol)=0.25. The stability of liposomes of the same composition as that in the Langmuir monolayers was analyzed by determining the size distribution of vesicles and the polydispersity as a function of time. The changes of these parameters confirmed that the system of the greatest stability is that with low Chol content.

Studies of cadmium(II), lead(II), nickel(II), cobalt(II) and chromium(VI) sorption on extracellular polymeric substances produced by Rhodococcus opacus and Rhodococcus rhodochrous

The adsorption of Cd(II), Pb(II), Ni(II), Co(II) and Cr(VI) ions on the extracellular polymeric substances (EPS) obtained from bacterial strain Rhodococcus opacus and Rhodococcus rhodochrous was investigated by the static sorption method. Influence of pH, time and temperature were studied. It was found that the influence of the pH value and time of adsorption depends on the type of adsorbed ions. For all investigated systems an increase of temperature above 35°C reduces adsorption. However, the static sorption capacities values oscillate around 1.5mmol/g, independently of the type of the studied metal ions. The adsorption mechanism of studied metal ions onto the tested EPSs seems to be very complex and it is probably due to an electrostatic attraction, a surface complex formation and chemical interaction between the metal ions and the functional groups (mainly hydroxyl, acetamido or amino groups) of bacterial extracellular biopolymers.

Surface properties of Ti-6Al-4V alloy part I: Surface roughness and apparent surface free energy

Titanium (Ti) and its alloys are the most often used implants material in dental treatment and orthopedics. Topography and wettability of its surface play important role in film formation, protein adhesion, following osseointegration and even duration of inserted implant. In this paper, we prepared Ti-6Al-4V alloy samples using different smoothing and polishing materials as well the air plasma treatment, on which contact angles of water, formamide and diiodomethane were measured. Then the apparent surface free energy was calculated using four different approaches (CAH, LWAB, O-W and Neumanns Equation of State). From LWAB approach the components of surface free energy were obtained, which shed more light on the wetting properties of samples surface. The surface roughness of the prepared samples was investigated with the help of optical profilometer and AFM. It was interesting whether the surface roughness affects the apparent surface free energy. It was found that both polar interactions the electron donor parameter of the energy and the work of water adhesion increased with decreasing roughness of the surfaces. Moreover, short time plasma treatment (1min) caused decrease in the surface hydrophilic character, while longer time (10min) treatment caused significant increase in the polar interactions and the work of water adhesion. Although Ti-6Al-4V alloy has been investigated many times, to our knowledge, so far no paper has been published in which surface roughness and changes in the surface free energy of the alloy were compared in the quantitative way in such large extent. This novel approach deliver better knowledge about the surface properties of differently smoothed and polished samples which may be helpful to facilitate cell adhesion, proliferation and mineralization. Therefore the results obtained present also potentially practical meaning.

Phosphate mineral formation on the supported dipalmitoylphosphatidylcholine (DPPC) layers.

Dipalmitoylphosphatidylcholine (DPPC) mono- and bilayers supported on mica surface were soaked for two weeks in a simulated body fluid (SBF) with ion concentrations nearly equal to those of human blood plasma. Two solutions were investigated: with and without Tris. The experiment was conducted at 20°C and at a physiological temperature equal to 37°C. Raman spectroscopy was used for the characterization of the precipitated phosphate minerals. These studies may provide information about the physiological mineralization of cell membranes that are mainly composed of phospholipids. Findings from these experiments suggest that the DPPC bilayers enhance the formation of less soluble phosphate forms especially at a temperature of 37°C. In the solution without Tris temperature increase gives more mineral deposits. It is probably the hydrogen interactions between phosphate groups of the phospholipid and hydroxyl groups from Tris that lower exposure of the phosphate group to interact with calcium ions.

Magnetic water treatment–A review of the latest approaches

Understanding of magnetic field (MF) effects observed during and after its action on water and aqueous solutions is still a controversial issue although the effects have been reported for at least half of century. The purpose of this paper was a brief review of the literature which deals with the magnetic force treatment effects. However, it is especially focused on the latest approaches, published mostly in the last decade which have developed our understanding of the mechanisms accompanying the field action. Generally, the changes in water structure via hydrogen bonding changes, as well as in intraclusters and between interclusters were taken into account, but the most remarkable progress was achieved in 2012 by Coey who applied the non-classical theory of nucleation mechanism of the formation of dynamically ordered liquid like oxyanion polymers (DOLLOP) to explain the magnetic field action. His criterion for the magnetic field effect to occur was experimentally verified. It was also proved that the gradient of the magnetic field is more important than the magnetic field strength itself. Some interesting approaches explaining an enhanced evaporation rate of water by MF are also discussed. More experimental results are needed for further verification of the DOLLOP theory to achieve a more profound understanding of the MF effects.