Antibacterial properties and regenerative potential of Sr2+ and Ce3+ doped fluorapatites; a potential solution for peri-implantitis.

Scaffolds and implants in orthopaedics and regenerative dentistry usually fail because of bacterial infections. A promising solution would be the development of biomaterials with both significant regenerative potential and enhanced antibacterial activity. Working towards this direction, fluorapatite was synthesised and doped with Sr2+ and Ce3+ ions in order to tailor its properties. After experiments with four common bacteria (i.e. E. Coli, S. Aureus, B. Subtilis, B. Cereus), it was found that the undoped and the Ce3+ doped fluorapatites present better antibacterial response than the Sr2+ doped material. The synthesised minerals were incorporated into chitosan scaffolds and tested with Dental Pulp Stem Cells (DPSCs) to check their regenerative potential. As was expected, the scaffolds containing Sr2+-doped fluorapatite, presented high osteoconductivity leading to the differentiation of the DPSCs into osteoblasts. Similar results were obtained for the Ce3+-doped material, since both the concentration of osteocalcin and the RUNX2 gene expression were considerably higher than that for the un-doped mineral. Overall, it was shown that doping with Ce3+ retains the good antibacterial profile of fluorapatite and enhances its regenerative potential, which makes it a promising option for dealing with conditions where healing of hard tissues is compromised by bacterial contamination.

Comparative evaluation of metallic skin staples or polypropylene sutures for primary closure of teat wounds in sheep.

AIMS: To compare stainless steel staples and polypropylene suture material for primary closure of wounds after teat amputation in ewes and to assess progress of healing in the presence or absence of intramammary infection (IMI). METHODS: Chios-cross ewes, aged 3-5 years were randomly allocated to be infected in one teat with 1,200-1,500 cfu of Mannheimia haemolytica 5 days after parturition (groups A and B; n = 8 in each group) or remain uninfected (groups C and D; n = 4 in each group). On the following 4 days one teat from each ewe was amputated 2.5 cm from the teat end and the wound was closed using skin staples (groups A and C) or polypropylene sutures (groups B and D). Clinical evaluation of wound healing was performed between 1-21 days after surgery. On day 21 tissue sections were collected for tensiometric and histological evaluation. RESULTS: The mean interval from the start to finish of wound closure was shorter when staples were used than when sutures were used (p < 0.001). Healing scores were lower (improved) for ewes in group A than B between days 1-7 after surgery (p = 0.005), but were similar between days 10-21 (p = 0.43). Healing scores were similar in groups C and D (p = 0.98). The tensile strain at maximum load was higher in tissue from group A than B (p = 0.001) and D (p = 0.004), but all other tensiometric measures were similar between groups. Histologically, collagen density was higher in sections from group A than B (p = 0.05) and D (p = 0.01), and angiogenesis was lower in sections from group A than B (p = 0.03) and D (p = 0.01). CONCLUSIONS AND CLINICAL RELEVANCE: Skin staples and polypropylene sutures can be used effectively for primary closure of teat wounds, even in the presence of IMI. Skin staples had the advantage of a reduction in surgical time. ABBREVIATION: IMI: intramammary infection.

Photocatalytical removal of fluorouracil using TiO2-P25 and N/S doped TiO2 catalysts: A kinetic and mechanistic study.

In the present study, the photocatalytic activity of TiO2-based photocatalysts toward degradation and mineralization of the anti-cancer drug 5-fluorouracil (5-FU) in aqueous phase was investigated under simulated solar and visible irradiation. Commercial TiO2 (P25) and N/S-doped TiO2 catalysts synthesized by a simple sol-gel method were used as photocatalysts. TiO2 P-25 was found to be the most photoactive catalyst for the removal of 5-FU, under simulated solar irradiation. Among N/S-doped TiO2 catalysts, the one with molar Ti:N/S ratio equal to 0.5 was the most efficient under simulated solar irradiation. In contrast, under visible irradiation the catalyst with equimolar Ti:N/S ratio showed the highest performance for the removal of 5-FU. Scavenging experiments revealed that HO radicals and h+ were the major reactive species mediating photocatalytic degradation of 5-FU using TiO2 P-25 and N/S-doped TiO2 catalysts, under simulated solar irradiation. On the other hand, the essential contribution of 1O2 and O2- in the degradation of 5-FU under visible light was proved. The transformation products (TPs) of 5-FU, were identified by LC-MS-TOF suggesting that defluorination followed by hydroxylation and oxidation are the main transformation pathways, under all the studied photocatalytic systems.

Synthesis of folate- pegylated polyester nanoparticles encapsulating ixabepilone for targeting folate receptor overexpressing breast cancer cells.

The aim of this study was the preparation of novel polyester nanoparticles based on folic acid (FA)-functionalized poly(ethylene glycol)-poly(propylene succinate) (PEG-PPSu) copolymer and loaded with the new anticancer drug ixabepilone (IXA). These nanoparticles may serve as a more selective (targeted) treatment of breast cancer tumors overexpressing the folate receptor. The synthesized materials were characterized by (1)H-NMR, FTIR, XRD and DSC. The nanoparticles were prepared by a double emulsification and solvent evaporation method and characterized with regard to their morphology by scanning electron microscopy, drug loading with HPLC-UV and size by dynamic light scattering. An average size of 195 nm and satisfactory drug loading efficiency (3.5%) were observed. XRD data indicated that IXA was incorporated into nanoparticles in amorphous form. The nanoparticles exhibited sustained drug release properties in vitro. Based on in vitro cytotoxicity studies, the blank FA-PEG-PPSu nanoparticles were found to be non-toxic to the cells. Fluorescent nanoparticles were prepared by conjugating Rhodanine B to PEG-PPSu, and live cell, fluorescence, confocal microscopy was applied in order to demonstrate the ability of FA-PEG-PPSu nanoparticles to enter into human breast cancer cells expressing the folate receptor.

Modified chitosan coated mesoporous strontium hydroxyapatite nanorods as drug carriers.

Mesoporous strontium hydroxyapatite (SrHAp) nanorods (NRs) have been successfully synthesized using a simple and efficient chemical route, i.e. the hydrothermal method. Structural and morphological characterization of the as-synthesized SrHAp NRs have been performed by transmission electron microscopy (TEM) and high angle annular dark field scanning transmission electron microscopy (HAADF-STEM). TEM and HAADF-STEM measurements of the NRs reveal the coexistence of longer and shorter particles with the length ranging from 50 nm to 400 nm and a diameter of about 20-40 nm. Electron tomography measurements of the NRs allow us to better visualize the mesopores and their facets. Two model drugs, hydrophobic risperidone and hydrophilic pramipexole, were loaded into the SrHAp NRs. These nanorods were coated using a modified chitosan (CS) with poly(2-hydroxyethyl methacrylate) (PHEMA), in order to encapsulate the drug-loaded SrHAp nanoparticles and reduce the cytotoxicity of the loaded materials. The drug release from neat and encapsulated SrHAp NRs mainly depends on the drug hydrophilicity. Importantly, although neat SrHAp nanorods exhibit some cytotoxicity against Caco-2 cells, the Cs-g-PHEMA-SrHAp drug-loaded nanorods show an acceptable cytocompatibility.

Thermal degradation kinetics and decomposition mechanism of PBSu nanocomposites with silica-nanotubes and strontium hydroxyapatite nanorods.

Novel poly(butylene succinate) (PBSu) nanocomposites containing 5 and 20 wt% mesoporous strontium hydroxyapatite nanorods (SrHNRs) and silica nanotubes (SiNTs) were prepared by melt-mixing. A systematic investigation of the thermal stability and decomposition kinetics of PBSu was performed using pyrolysis-gas chromatography-mass spectroscopy (Py-GC-MS) and thermogravimetry (TG). Thorough studies of evolving decomposition compounds along with the isoconversional and model-fitting analysis of mass loss data led to the proposal of a decomposition mechanism for PBSu. Moreover, the effects of SrHNRs and SiNTs on the thermal stability and decomposition kinetics of PBSu were also examined in detail. The complementary use of these techniques revealed that the incorporation of SiNTs in PBSu does not induce significant effects neither on its thermal stability nor on its decomposition mechanism. In contrast, the addition of SrHNRs resulted in the catalysis of the initial decomposition steps of PBSu and also in modified decomposition mechanisms and activation energies. The evolving gaseous products of PBSu and their evolution pattern in the SiNT nanocomposites were the same as in neat PBSu, while they were slightly modified for the SrHNR nanocomposites, confirming the findings from thermogravimetric analysis.

Real time and non-destructive analysis of tablet coating thickness using acoustic microscopy and infrared diffuse reflectance spectroscopy.

Tablet coating thicknesses were estimated using several techniques such as weight gain and scanning electron microscopy (SEM), in comparison with acoustic microscopy and diffuse reflectance spectroscopy. Acoustic microscopy, used for the first time in such an application, is based on the physical phenomenon of ultrasound propagation through the materials and the echoes generated by their interfaces. Based on the time of flights (TOFs) of the echoes from the coating surface and the tablet, it is possible to calculate the coating thickness. In order to evaluate the accuracy and robustness of these methods, drug tablets were coated with Kollicoat SR polymer for several times, so that to prepare tablets with different coating thicknesses. Tablets with 3, 6 and 9 wt% coating material have been prepared and based on SEM micrographs it was found that the tablet coating thickness is 71.99 ± 1.2 µm, 92.5 ± 1.7 µm and 132.3 ± 2.1 µm, respectively (SEM analysis). The tablet coating thicknesses measured with acoustic microscopy and infrared diffuse reflectance spectroscopy, were in agreement with those obtained using SEM. This verifies that both techniques can be successfully applied for real time and non-destructive thickness measurements of tablet coating. Furthermore, both techniques, compared with SEM and weight gained measurements, are fast and fully automated.

Facile synthesis of polyester-PEG triblock copolymers and preparation of amphiphilic nanoparticles as drug carriers.

Novel amphiphilic triblock copolymers of poly(propylene succinate) (PPSu) and poly(ethylene glycol) (PEG) with different hydrophobic/hydrophilic ratios were synthesized using a facile one-pot procedure. The molecular weight of the copolymers was adjusted by varying the molecular weight of PPSu while keeping that of PEG constant. The copolymers exhibited glass transition temperatures between -36.0 and -38°C and single melting points around 44°C. WAXD data indicated that both blocks of the copolymers could crystallize. The mPEG-PPSu copolymers exhibited low in vitro toxicity against HUVEC cells. The synthesized copolymers were used to prepare core-shell nanoparticles with hydrophobic PPSu and hydrophilic PEG forming the core and shell, respectively. The drug loading efficiency and drug release properties of the mPEG-PPSu nanoparticles were investigated using two model drugs: the hydrophilic Ropinirole and the hydrophobic Tibolone. The mean size of the drug-loaded mPEG-PPSu nanoparticles ranged between 150 and 300nm and increased with the molecular weight of the PPSu block. The drug loading efficiency of the nanoparticles was found to be dependent upon drug hydrophilicity and was much higher for the hydrophobic Tibolone. Drug release characteristics also depended on drug hydrophilicity: the hydrophilic Ropinirole was released at a much higher rate than the hydrophobic Tibolone. Contrary to Ropinirole, the profiles of Tibolone exhibited an early phase of burst release followed by a phase of slow release. By varying the composition (mPEG/PPSu ratio) of mPEG-PPSU copolymers, nanoparticles of different sizes and drug loading capacities can be synthesized exhibiting different drug release characteristics. Based on the results obtained, the proposed mPEG-PPSu copolymers can be useful in various controlled drug delivery applications, especially those involving relatively hydrophobic drugs.

Dissolution rate and stability study of flavanone aglycones, naringenin and hesperetin, by drug delivery systems based on polyvinylpyrrolidone (PVP) nanodispersions.

OBJECTIVE: To study the dissolution behavior, the release mechanism and the stability of nanodispersion system of aglycones with PVP. METHODS: The nanodispersion system of polyvinylpyrrolidone (PVP)/naringenin-hesperetin was prepared using the solvent evaporation method. The chemical stability (compatibility) of naringenin and hesperetin in the prepared dispersions was studied under accelerated conditions for 3 months. The evaluation of physical stability was performed by X-ray diffraction analysis (XRD) and by comparing the dissolution profile before and after storage at high temperature and moisture (40 masculineC, RH 75%). RESULTS: The dissolution rate of naringenin and hesperetin released was dramatically increased in the nanodispersion system of PVP/naringenin-hesperetin (80/20, w/w). The release mechanism of both flavanone aglycones was better described by the diffusion model (Higuchi model). Also it was found that the rate-limiting step that controlled the release of naringenin and hesperetin in the nanodispersion system was dissolution of the carrier (PVP). CONCLUSIONS: During accelerated degradation analysis, for 3 months at high temperature and moisture, PVP nanodispersion system showed enhanced chemical compatibility and physical stability. The physical evaluation (obtained from XRD analysis) of PVP/naringenin-hesperetin (80/20, w/w) in the selected storage conditions did not show any crystallization of flavanone aglycones in the PVP nanodispersion system or any change in their release profile.

Improvement in chemical and physical stability of fluvastatin drug through hydrogen bonding interactions with different polymer matrices.

Solid dispersions of Fluvastatin with polyvinylpyrrolidone (PVP), eudragit RS100 (Eud), and chitosan (CS) as drug carrier matrices, were prepared using different techniques in order to evaluate their effect on Fluvastatin stability during storage. The characterization of the three different systems was performed with the use of differential scanning calorimetry (DSC) and wide angle X-ray diffractometry (WAXD). It was revealed that amorphization of the drug occurred in all of the solid dispersions of Fluvastatin as a result of drug dissolution into polymer matrices and due to physical interactions (hydrogen bonding) between the polymer matrix and Fluvastatin. This was established through the use of FTIR spectroscopy. SEM and micro-Raman spectroscopy showed that Fluvastatin was interspersed to the polymer matrices in the form of molecular dispersion and nanodispersion, too. The finding that completely different polymer matrices, used here as drug carriers, produce completely different dissolution profiles for each one of the solid dispersions, suggests that each matrix follows a different drug release mechanism. Hydrogen bonding interactions as in the case of CS/Fluva solid dispersions lead to controlled release profiles. All formulations were subjected to accelerated aging in order to evaluate Fluvastatin stability. From by-products analysis it was found that Fluvastatin is very unstable during storage and anti-isomer as well as lactones are the main formed by-products. On the other hand, solid dispersions due to the evolved interactions of their reactive groups with Fluvastatin provide a sufficient physical and chemical stability. The extent of interactions seems to play the most important role in the drug stabilization.

Effect of conditions of preparation on the size and encapsulation properties of PLGA-mPEG nanoparticles of cisplatin.

The effect of conditions of preparation on the size and encapsulation properties of PLGA-mPEG nanoparticles of cisplatin was investigated. A modified double emulsion method was applied for the preparation of PLGAmPEG nanoparticles of cisplatin, based on the partial or complete replacement of the water of the inner aqueous phase of the emulsion by dimethyl formamide(dmf) or the addition of cisplatin in the form of a complex with poly(glutamic acid). These modifications resulted in significant improvement of cisplatin loading in the PLGA-mPEG nanoparticles. Increased cisplatin loading and encapsulation efficiency were obtained when a relatively low dmf/water ratio, low dmf volume (when pure dmf formed the inner polar phase), or a high drug/polymer ratio were applied. A reduction of average size of nanoparticles was observed with decreasing the amount of PLGA-mPEG added in the formulation or increasing sonication time. The only factor that had a significant effect on size distribution was the sonication time, with the size P.I. being decreased with increasing sonication time. Prolonged sonication, however, decreased cisplatin loading and encapsulation efficiency. From the four lyoprotectant sugars tested (glucose, lactose, mannitol, and trehalose), only mannitol could prevent nanoparticle aggregation upon lyophilization. When appropriate amounts of an effective lyoprotectant were added in nanoparticles before lyophilization, drug loading of the nanoparticles was not affected by nanoparticle lyophilization.

Ochre-differentiation through micro-Raman and micro-FTIR spectroscopies: application on wall paintings at Meteora and Mount Athos, Greece.

The most widely-used inorganic pigments of Byzantine and post-Byzantine hagiography are earth pigments called ochres such as, red and yellow ochres, limonite, goethite, raw and burnt sienna, caput mortuum and hematite. The present experimental work proposes a technique of differentiation that allows one to distinguish among all the different kinds of iron oxides, thereby providing a better understanding of the painting technique used on portable icons and wall paintings. The ratios between the main spectroscopic peaks, attributable to the major components usually present in ochres, were calculated and compared, one against the another, from the spectra obtained through micro-Raman spectroscopy. Elementary composition is also revealed through a scanning electron microscopy (SEM) analysis. The possibility for detailed study on a particular Byzantine ochre palette can thus be performed based on the small differences in its nature and composition. These differences can first be observed and then measured among all of the natural earth pigments, through microRaman and microFTIR spectroscopies.