NADINE: new approaches to detecting breast cancer by sequential µm-wavelength imaging with the aid of novel frequency analysis techniques.

The study focuses on 12 breasts of six breast cancer patients sequential µm-wavelength imaging, taken by two different 3-5 µm wavelength area indium antimony (InSb) photovoltaic cameras. The aim of the study was to compare the functionality of area and pixel-based frequency analyses. Comparisons between these frequency analysis methods were made according to their relevancy to mammographic findings. Another objective of the study was to find reliable imaging conditions by specifying the border conditions for the patient stabilizing imaging bed and managing the imaging situation. According to the results, the match of pixel based frequency analysis to the mammography findings is better than using area frequency analysis. The results also indicate that when the optical axis of the camera in relation to the surface of the breast to be imaged grows to more than 40°, the emissivity changes dramatically and at that point reliable results will not be obtained. Consequently the analysis of the imagined breast requires more images to be fused into one analysis image to cover the whole breast.

Preparation and complex characterization of silica holmium sol-gel monoliths.

Amorphous, sol-gel derived SiO(2) are known to biocompatible and bioresorbable materials. Biodegradable and inert materials containing radioactive isotopes have potential application as delivery vehicles of the beta radiation to the cancer tumors inside the body. Incorporation of holmium in the sol-gel derived SiO(2) could lead to the formation of a biodegradable material which could be used as carrier biomaterial for the radiation of radioactive holmium to the various cancer sites. The homogeneity of the prepared sol-gel silica holmium monoliths was investigated by Back Scattered Electron Imaging of Scanning Electron Microscope equipped with Energy Dispersive X-ray Analysis, X-ray Induced Photoelectron Spectroscopy and Nuclear Magnetic Resonance Spectroscopy. The biodegradation of the monoliths was investigated in Simulated Body Fluid and TRIS (Trizma pre-set Crystals) solution. The results show that by suitable tailoring of the sol-gel processing parameters holmium can be homogeneously incorporated in the silica matrix with a controlled biodegradation rate.

The behaviour of selected yttrium containing bioactive glass microspheres in simulated body environments.

The study aims at the manufacture and investigation of biodegradable glass microspheres incorporated with yttrium potentially useful for radionuclide therapy of cancer. The glass microspheres in the SiO2-Na2O-P2O5-CaO-K2O-MgO system containing yttrium were prepared by conventional melting and flame spheroidization. The behaviour of the yttrium silicate glass microspheres was investigated under in vitro conditions using simulated body fluid (SBF) and Tris buffer solution (TBS), for different periods of time, according to half-life time of the Y-90. The local structure of the glasses and the effect of yttrium on the biodegradability process were evaluated by Fourier Transform Infrared (FT-IR) spectroscopy and Back Scattered Electron Imaging of Scanning Electron Microscopy (BEI-SEM) equipped with Energy Dispersive X-ray (EDX) analysis. UV-VIS spectrometry and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was used for analyzing the release behaviour of silica and yttrium in the two used solutions. The results indicate that the addition of yttrium to a bioactive glass increases its structural stability which therefore, induced a different behaviour of the glasses in simulated body environments.

The properties of biomimetically processed calcium phosphate on bioactive ceramics and their response on bone cells.

This study looks for grounds to alter the chemical composition (phosphate, calcium, silica and carbonate), dissolution properties, structure and nanotopography of the biomimetically processed surfaces on bioactive ceramics to optimize their shown ability to influence bone cell behaviour and production of new bone. In the bone environment desirable characteristic of these materials is their ability to be remodeled by natural osteoclastic resorption. Different silica and carbonate containing calcium phosphate layers were prepared on bioactive glasses 9 (S53P4) and 1-98 (S53P2) and sol-gel processed pure silica SiO2 in C- and R-SBF (conventional and revised simulated body fluid) for varying periods of time. It was shown that in R-SBF the CaP layer formed faster compared to C-SBF. The CaP layer in the R-SBF contained more carbonate (CO3(2-)) compared to that formed with the same immersion time in C-SBF. The CaP so formed in R-SBF with faster precipitation is more amorphous than the bonelike HCA formed in C-SBF. The results indicate that the most suitable surface for both osteoblasts and osteoclasts was found to be an amorphous CaP having mesoporous nanotopography and proper dissolution rate of calcium and silica.

Study of yttrium containing bioactive glasses behaviour in simulated body fluid.

The influence of yttrium oxide on the bioactivity of glasses in the system SiO(2)-Na(2)O-P(2)O(5)-CaO-B(2)O(3)-K(2)O-MgO was studied in a simulated body fluid (SBF). Two series of glasses with different bioactivity were investigated. The reaction layers formed on the surface of the exposed glasses were evaluated by means of back scattered electron imaging of scanning electron microscopy equipped with energy dispersive X-ray analysis (BEI-SEM/EDXA). The concentration of Y, Ca and P released from the glasses into SBF, during 21 days was determined using inductively coupled plasma-emission spectroscopy ICP-AES and inductively coupled plasma-mass spectroscopy ICP-MS. Introducing yttrium in the selected bioactive glass tended to diminish the bioactivity of the glasses. The thickness of the calcium phosphate layer decreased with increasing yttrium oxide content. The same effect was also observed when yttrium oxide partially replaced only calcium, magnesium and phosphorous oxide in the precursor glass. The data show that we can produce bioactive glasses with yttrium oxide as a component. By suitable tailoring of the rest of the glasses the yttrium effect on the glass behavior in SBF should be possible to control and thus produce yttrium containing glasses with desired bioactivity.

Characterisation of bioactive glass coatings on titanium substrates produced using a CO2 laser.

Titanium and its alloys are widely used in load-bearing bioinert implants. Bioactive glasses (BAGs) form a chemical bond with bone, but they are not suitable for load-bearing applications. Creating a BAG coating on a titanium implant could combine the best properties of both materials. The results tend to be poor when conventional firing methods are applied to coat titanium with BAG. A local application of heat to melt the glass can be achieved by a CO2 laser. A new method is introduced to create BAG coatings on titanium locally in a controlled manner, with a focused CO2 laser beam. The coatings produced by this method precipitate calcium phosphate in vitro. Processing parameters (number of coated layers, laser power, and processing atmosphere) providing a firm attachment of the glass and good in vitro bioactivity were identified. XRD analysis showed no crystallisation of the glass due to processing with the laser. EDXA indicated the formation of a calcium phosphate layer, which FTIR suggested to be a hydroxyapatite. The results show CO2 laser processing to be a promising technique for the manufacture of 30-40 microm BAG coatings on titanium.

Implants coated with bioactive glass by CO2-laser, an in vivo study.

Due to ageing of the population, the number of revision operations is expected to increase. Thus good fixation of medical implants is crucial for successful treatment. In our previous studies, a method to coat titanium implants with bioactive glass (BAG) via CO2 laser treatment was introduced. It allows to localise the application of a bioactive coating, without heat treatment of the whole implant. In the present study, cylindrical titanium implants were used (BAG-coated, control group: NaOH-treated and grit-blasted Ti). Three implants were placed in each femoral epicondyle of six rabbits. After eight weeks the animals were sacrificed. Half of the implants were subjected to a torsional loading test. In the control groups, the failure occurred at the bone-implant interface, in the BAG group the failure occurred mainly in the reacted glass. The implants coated with BAG were integrated into host bone without a connective tissue capsule and were surrounded by significantly more bone than the control implants. The findings indicate clearly that the use of CO2 laser radiation to create BAG coatings did not inhibit the bioactive properties of the glass in terms of osteoconduction.

Molecular biologic comparison of new bone formation and resorption on microrough and smooth bioactive glass microspheres.

In a recent in vitro study, chemical microroughening of a bioactive glass surface was shown to enhance attachment of MG-63 osteoblastic cells to glass. The current study was designed to delineate the effects of microroughening on the gene expression patterns of bone markers during osteogenesis and new bone remodeling on bioactive glass surface in vivo. With the use of a rat model of paired comparison, a portion of the medullary canal in the proximal tibia was evacuated through cortical windows and filled with microroughened or smooth bioactive glass microspheres. The primary bone-healing response and subsequent remodeling were analyzed at 1, 2, and 8 weeks, respectively, by radiography, pQCT, histomorphometry, BEI-SEM, and molecular biologic analyses. The expression of various genes for bone matrix components (type I collagen, osteocalcin, osteopontin, osteonectin) and proteolytic enzymes (cathepsin K, MMP-9) were determined by Northern analysis of the respective mRNAs. Paired comparison showed significant differences in the mRNAs levels for specific bone matrix components at 2 weeks: osteopontin was significantly higher (p =.01) and osteonectin significantly lower (p =.05) in bones filled with microroughened microspheres than in those filled with smooth microspheres. Bones filled with microrough microspheres also showed significantly increased ratios of cathepsin K and MMP-9 (both markers of osteoclastic resorption) to type I collagen (p =.02 and p =.02, respectively) at 2 weeks and a significantly increased expression of MMP-9 at 8 weeks (p =.05). The pQCT, histomorphometric, and BEI-SEM analyses revealed no significant differences in the pattern of bone-healing response. Based on these results, microroughening of a bioactive glass surface could trigger temporal changes in the expression of specific genes especially by promoting the resorption part of new bone-remodeling processes. Future studies are needed to evaluate if the observed changes of gene expression are directly related to the microrough surface of any biomaterial or are biomaterial specific.

Characterization of microrough bioactive glass surface: surface reactions and osteoblast responses in vitro.

The current study characterized the in vitro surface reactions of microroughened bioactive glasses and compared osteoblast cell responses between smooth and microrough surfaces. Three different bioactive glass compositions were used and surface microroughening was obtained using a novel chemical etching method. Porous bioactive glass specimens made of sintered microspheres were immersed in simulated body fluid (SBF) or Tris solutions for 1, 6, 24, 48, or 72 h, and the formation of reaction layers was studied by means of a scanning electron microscope/energy dispersive X-ray analysis (SEM/EDXA). Cell culture studies were performed on bioactive glass disks to examine the influence of surface microroughness on the attachment and proliferation of human osteoblast-like cells (MG-63). Cell attachment was evaluated by means of microscopic counting of in situ stained cells. Cell proliferation was analyzed with a nonradioactive cell proliferation assay combined with in situ staining and laser confocal microscopy. The microroughening of the bioactive glass surface increased the rate of the silica gel layer formation during the first hours of the immersion. The formation of calcium phosphate layer was equal between control and microroughened glass surfaces. In cell cultures on bioactive glass, the microrough surface enhanced the attachment of osteoblast-like cells but did not have an effect on the proliferation rate or morphology of the cells as compared with smooth glass surface. In conclusion, microroughening significantly accelerated the early formation of surface reactions on three bioactive glasses and had a positive effect on initial cell attachment.

Influence of the non-bridging oxygen groups on the bioactivity of silicate glasses.

The effect of the composition and bonding configuration of the bioactive silica-based glasses on the initial stage in vitro bioactivity is presented. Information of the IR active Si-O groups of glass in the system SiO(2)-P(2)O(5)-CaO-Na(2)O-K(2)O-MgO-B(2)O(3) was obtained by fourier transform Infrared (FTIR) spectroscopy. Two different bands associated to non-bridging oxygen stretching vibrations (Si-O-1NBO and Si-O-2NBO) and a gradual shifting of the bridging oxygen stretching vibration (Si-O) have been observed and evaluated. Both effects are attributed to a decrease of the local symmetry originating from the incorporation of alkali ions into the vitreous silica network. The Si-O-NBO(s)/Si-O(s) absorbance intensity ratio increases with a gradual incorporation of the alkali ions (diminution of SiO(2) content) following a linear dependence up to values close to 50 wt % of SiO(2). In vitro test analysis by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDXA) showed a correlation between the amount and type of the non-bridging oxygen functional groups and the growth of the silica-rich and CaP layers. It was found that a minimum concentration of Si-O-NBO bonds in the glass network is required in order to have an efficient ion exchange and dissolution of the silica network. Finally, the bioactivity of the glass is favored by the presence of the Si-O-2NBO groups in the glassy network. The role of these functional groups in the dissolution of the silica network through the formation of silanol groups and the adsorption of water is discussed.

Pore diameter of more than 100 microm is not requisite for bone ingrowth in rabbits.

The optimal pore size for bone ingrowth is claimed to be 100-400 microm. With the use of a highly standardized experimental model, the present study reevaluated whether a pore size of 100 microm is the threshold value for bone ingrowth into porous structures under non-load-bearing conditions. Titanium triangle-shaped plates 250 or 500 microm thick were perforated with the use of a laser in order to create standard-sized holes ( 50, 75, 100, and 125 microm) in multiple rows. The amount of bone ingrowth through the implant holes was studied in the cancellous bone of the distal rabbit femur. Twelve weeks after implantation, detailed analysis of bone ingrowth was performed with computerized image analysis of backscattered electron imaging techniques of scanning electron microscopy. The results showed that the amount of ingrown new bone was independent of the pore size and implant thickness. The median value for bone ingrowth varied between 64 and 78%. A striking feature was the formation of secondary osteonal structures even in the smallest holes. Based on these results, there is no threshold value for new bone ingrowth in pore sizes ranging from 50 to 125 microm under non-load-bearing conditions.

Creation of microrough surface on sintered bioactive glass microspheres.

Bioactive glasses are surface-active, generally silica-based, synthetic materials that form a firm chemical bond to bone. The aim of this study was to further enhance the bioactivity of glasses by creating a microroughness on their surface. Microroughness increases potential surface area for cell attachment and biomaterial-cell interactions. Three bioactive glasses of different composition were studied. Each material was flame-sprayed into microspheres, and a selected fraction of the spheres (250-300 microm) was sintered to form porous bioactive glass specimens. To create microrough surfaces, different acid etching techniques were tested. Atomic force microscopy (AFM) and back-scattered electron imaging of scanning electron microscopy (BEI-SEM) were used to characterize surface roughness. The degree of roughness was measured by AFM. A novel chemical-etching method, developed through intensive screening of different options, was found consistently to create the desired microroughness, with an average roughness value (R(a)) of 0.35-0.52 microm and a root mean-square roughness value (R(rms)) of 0.42-0.64 microm. Microroughening of the glass surface was obtained even in the internal parts of the porous glass matrices. Measured by BEI-SEM, the etching of a bioactive glass surface did not interfere with the formation of the characteristic surface reactions of bioactive glasses. This was confirmed by immersing the etched and control glass bodies in a simulated body fluid and tris(hydroxymethyl) aminomethane/HCl. The etching process did not significantly affect the mechanical strength of the sintered bioactive glass structures. Based on these experiments, it seems possible to create a reproducible microroughness of appropriate size on the surface of porous bioactive glass. The biologic benefits of such a surface treatment need to be validated with in vivo experiments.

Silica-based bioactive glasses modulate expression of bone morphogenetic protein-2 mRNA in Saos-2 osteoblasts in vitro.

A chemical exchange of the silica gel layer forming on the surface of bioactive glasses is thought to be the principal reaction for bone-bioactive glass bonding. The contribution of biological molecules on cell-bioactive glass interaction is largely unknown. To further analyze the mechanisms involved in efficient bone bonding to bioactive glass, Saos-2 osteoblastic cells with proven osteogenic phenotype were cultured for 4, 7 and 14 days on two bioactive glasses with different Si contents. Culture plates and dishes made of bioactive (BAG, 53 % SiO2), biocompatible (BCG, 58% SiO2) and control (GO) glasses were extensively conditioned with phosphate buffer and DMEM medium before seeding the cells. Northern hybridization was used for analysis of mRNA levels of collagen type I (Col-I), alkaline phosphatase (ALP) and bone morphogenetic protein-2 (BMP-2). A significant increase was observed in Col-I mRNA levels in cells grown on the two bioactive glasses when compared with those grown on controls at 4 and 7 days (p < 0.04). The mRNA level for ALP in the cultures of bioactive glasses-made plates and dishes was also increased over control at 7 days (p < 0.02) and remained this way between BAG and G0 at 14 days. Striking differences in BMP-2 mRNA levels existed between BAG and G0 plates and dishes at 7 days (p < 0.05). BMP-2 mRNA level in BAG group was higher than in BCG group at 4, 7 and 14 days, but without statistical significance. Saos-2 osteoblastic cells with strong ALP staining were mostly seen on BAG plates under a light microscope. In confocal microscopy, a bright FITC-stained F-actin ring was present in the cytoplasm of cells grown on BAG dish, demonstrating an active functional status. Stimulation of the expression of BMP-2 and other bone mRNAs by bioactive glasses in osteoblastic cells suggests biological involvement of bone related growth factors, peptides and cytokines in bone-bioactive glass bonding.

Porous bioactive glass matrix in reconstruction of articular osteochondral defects.

BACKGROUND AND AIMS: This study was carried out to investigate the use of porous bioactive glass implants in promotion of articular cartilage and subchondral bone repair in large osteochondral joint defects. MATERIAL AND METHODS: Two conical osteochondral defects (top diameter 3.0-3.2 mm) were drilled into the patellar grooves of the distal femurs in the rabbit. The defects, extending (approximately 6-7 mm) from the surface of the articular cartilage to the subchondral marrow space, were reconstructed with size-matched porous conical implants made of sintered bioactive glass microspheres (microsphere diameter 250-300 microm, structural implant compression strength 20-25 MPa) using press-fit technique. The implant surface was smoothened to the level of the surrounding articular cartilage. One of the two defects in each femur was left empty to heal naturally and to serve as the control. At 8 weeks, the defect healing was analyzed with use of a semiquantitative histological grading system, histomorphometry of subchondral bone repair, back-scattered electron imaging of scanning electron microscopy (BEI-SEM), and a microindentation test for characterization for the stiffness properties of the cartilage repair tissue. RESULTS: The porous structure of the bioactive glass implants, extending from the articular defect of the patellar groove into the posterior cortex of the femur, was extensively filled by new bone. Cartilage repair varied from near-complete healing by hyaline cartilage to incomplete healing predominantly by fibrocartilage or fibrous tissue. There were, however, no statistical differences in the histological scores of repair between the glass-filled and control defects, although the sum of the averages of each category was lowest for the bioactive glass filled defects. The indentation stiffness values of all the defects were also significantly lower than that of normal cartilage on the patellar groove. CONCLUSIONS: Porous textures made by sintering bioactive glass microspheres may expand the opportunities in reconstruction of deep osteochondral defects of weight-bearing joints. The implants act mechanically as a supporting scaffold and facilitate the penetration of stromal bone marrow cells and their chondrogenic and osteogenic differentiation. Ionic properties of the bioactive glasses make the substances highly potential even as delivery systems for adjunct growth factor therapy.

Bioactive glasses induce chemiluminescence by human polymorphonuclear leukocytes.

The effect of bioactive glasses on human polymorphonuclear leukocytes (PMNLs) were studied in vitro by a chemiluminescence (CL) assay. Eight different glasses were chosen. All glasses induced a rapid CL response by human PMNLs, which proved to be dose dependent. The CL response also seemed to depend on the durability of the glasses. The least durable glass caused the highest CL response, and highly durable glasses caused only low CL responses by the cells.