N. Polyaka

Electrically Charged Hydroxyapatite Enhances Immobilization and Proliferation of Osteoblasts

Hydroxyapatite (HAP) is in use to fabricate implants in dentistry and orthopaedy. To functionalise a surface of the HAP that has a direct contact to the human cells a surface electrical charge deposition is employed. The current technologies can not provide uniformity of the charge for contrarily situated surfaces.

Electrically Functionalized Hydroxyapatite and Calcium Phosphate Surfaces to Enhance Immobilization and Proliferation of Osteoblasts In Vitro and Modulate Osteogenesis In Vivo

Hydroxyapatite (HAP) is used to fabricate implants for bone repair in dentistry and orthopaedics. To functionalise the surface of HAP that is in direct contact with human cells a surface electrical charge deposition has been achieved by means of hydrogenation technology. This technology provides uniform 3 dimensioned processing of the specimen surfaces. The engineered charge was estimated from measurements of the photoelectron emission work function (ϕ). The later was increased to ~ 0.2 eV. The negatively charged HAP surface attached 10 times more osteoblatic cells and increased their proliferation capacity 1.6 times, in contrast to the uncharged one.

Influence of Bioimplant Surface Electrical Potential on Osteoblast Behavior and Bone Tissue Formation

Following the general adhesion theory the bone cells attachment to the bioimplant could be controlled by its surface electrical potential. The latter was adjusted both by deposition of the electrical charge and the surface microgeometry. It was demonstrated that a relief of the surface had an influence on the potential at the nanoscale and could be engineered to promote cell adhesion.

PbS Nanodots For Ultraviolet Radiation Dosimetry

Lead sulfide (PbS) nanodots in Zirconia (ZrO2) thin film matrix (ZrO2:PbS films) were investigated for UV radiation dosimetry purposes. Samples were fabricated using sol-gel technique. ZrO2:PbS films were irradiated with UV light with wavelengths 250 – 400 nm during 50 minutes. Photoelectron emission spectra of ZrO2:PbS films were recorded and band structure for nonradiated and UV irradiated samples was calculated. It was found that quantity of localized states decreased after UV irradiation while density of localized states was dependent on concentration of PbS nanodots. The observed changes in band structure of ZrO2:PbS films after UV irradiation suggest that the films may be considered as an effective material for UV radiation dosimetry, PbS nanodots being the UV sensitive substance of such a dosimeter.

The Biomaterial Surface Nanoscaled Electrical Potential Promotes Osteogenesis of the Stromal Cell

The calcium phosphate coating was provided onto the titanium substrate because of the nanoarc coatings technology. Both surface morphology and electrical charge of the coating were measured at the nano/micro-scaled lateral resolution. The negative electrical potential was typical for sockets, however the positive one to the peaks of the roughness. The cells were mainly attached at the negatively charged sockets. The cells expressed both osteocalcin and alkaline phosphatase that are the osteoblastic molecular markers.

Nanoscale Electrical Potential and Roughness of a Calcium Phosphate Surface Promotes the Osteogenic Phenotype of Stromal Cells

Mesenchymal stem cells (MSCs) and osteoblasts respond to the surface electrical charge and topography of biomaterials. This work focuses on the connection between the roughness of calcium phosphate (CP) surfaces and their electrical potential (EP) at the micro- and nanoscales and the possible role of these parameters in jointly affecting human MSC osteogenic differentiation and maturation in vitro. A microarc CP coating was deposited on titanium substrates and characterized at the micro- and nanoscale. Human adult adipose-derived MSCs (hAMSCs) or prenatal stromal cells from the human lung (HLPSCs) were cultured on the CP surface to estimate MSC behavior. The roughness, nonuniform charge polarity, and EP of CP microarc coatings on a titanium substrate were shown to affect the osteogenic differentiation and maturation of hAMSCs and HLPSCs in vitro. The surface EP induced by the negative charge increased with increasing surface roughness at the microscale. The surface relief at the nanoscale had an impact on the sign of the EP. Negative electrical charges were mainly located within the micro- and nanosockets of the coating surface, whereas positive charges were detected predominantly at the nanorelief peaks. HLPSCs located in the sockets of the CP surface expressed the osteoblastic markers osteocalcin and alkaline phosphatase. The CP multilevel topography induced charge polarity and an EP and overall promoted the osteoblast phenotype of HLPSCs. The negative sign of the EP and its magnitude at the micro- and nanosockets might be sensitive factors that can trigger osteoblastic differentiation and maturation of human stromal cells.

PBS Nanodots for Ultraviolet Radiation Nanosensor

PbS nanodots embedded in a zirconium oxide nanofilm were explored as possible ultraviolet (UV) sensors for nanodosimetry purposes. The nanodots were excited by ultraviolet photons to get emission of weak electrons. The emitted charge correlated to UV exposure indicates that PbS nanodots have potential for use as UV sensors for nanodosimetry.

Surface Properties of Ocular Prostheses Material Change under UV Influence

Poly methyl metha acrylate (PMMA) is widely used for eye prostheses and contact lenses. These devices are worn outdoors and, therefore, exposed to the ultraviolet radia- tion of Sun. This may cause changes in PMMA properties and bring discomfort to the patient, for instance, because of poly- mer surface wettability alteration. Namely, alteration of wet- tability of PMMA due to ultraviolet radiation and correlation of wettability with other surface properties is under the focus of the present research. Wettability of PMMA changes due to UV irradiation in ir- regular manner. Besides, good correlation existed between wettability, electron work function and peculiarities of the absorption spectra of PMMA.

PbS Nanodots Embedded in ZrO2 Thin Films for Ultraviolet Radiation Dosimetry

PbS nanodots embedded in ZrO2 thin film matrix (ZrO2:PbS films) were investigated for UV radiation dosimetry purposes. ZrO2:PbS films were UV irradiated using wavelengths 250 - 400 nm. Photoelectron emission spectra of ZrO2:PbS films were recorded and band structure of the films was calculated. It was found that density of localized states increased with increase in concentration of PbS nanodots which allowed to suggest that PbS nanodots are responsible for creation of localized states. Number of localized states decreased after UV irradiation. The linear correlation between number of localized states and time of UV exposure was observed. Observed changes in band structure of ZrO2:PbS films under the influence of UV irradiation suggest that the films may be considered as an effective material for UV radiation dosimetry, PbS nanodots being the UV sensitive substance of the films.

Influence of Hydrogenated Calcium Phosphate Surface on Potential of Stromal Stem Cells in Situ

We have applied novel technique for enhancing bone tissue formation on micro- and nanostructured calcium phosphate (CP) coatings. CP surfaces with “primitive” physical-chemical composition, which is not corresponding to last one in bone, have an active effect on functional properties of mesenchymal stromal cell pull (MSCP). The studied micro-CP coatings, characterized by marked roughness of surface had an osteoinductive potential up to 100 %. Relief of CP coatings from HAP nanoparticles (30–50 nm) does not practically differ from ones designed by use of HAP microparticles. Roughness of all CP nanocoatings had average Ra=5.13−6.43 µm and Rz=18.71−24.16 µm that was corresponded to CP microcoatings one. Probability of bone plate formation on CP nanostructured coatings was only 12.5 %. Hydrogenation of the CP surface layer increased its negative charge that was evaluated by means of photoelectron work function (ϕ) measurement. An increment of ϕ at the values of ≈0.1−1 eV was supplied. This had an effect on the directions of MSCP differentiation. For example, connective tissue growth was improved. For all this, probability of following ossification with growth of membrane reticulated bone was 20 %. Vice versa, decrease of ϕ led to primary formation of bone from bone marrow MSCP. Technique of intracellular RNA staining detected the actively synthesized osteoblasts and bone marrow stromal cells. The above evidences that hydrogenation of CP coatings could in situ effect MSCP differentiation in fibroblasts or osteoblasts associated with stromal cells of hemopoietic inducing microenvironment.