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At least 649 records · Page 36Linked to original sources

PubMed2005

Monitoring cell adhesion processes on bioactive polymers with the quartz crystal resonator technique.

The Thickness Shear Mode (TSM) quartz crystal resonator has been extensively used as sensitive sensor in various electrochemical and biological applications. This technique based on the propagation of an ultrasonic shear wave generated by a sinusoidal electric field through a piezoelectric quartz resonator, provides a non-destructive and powerful means to probe changes at solid-solid or solid-liquid interfaces. In this study, TSM was used to characterize cell-polymer interactions developing during the cell adhesion process. TSM sensing was used to monitor the inhibiting properties of bioactive polymers towards fibroblast McCoy adhesion processes. For this purpose, thin films of various bioactive polymers exhibiting either carboxylate or/and sulfonate functional groups were deposited onto the TSM. Measurements of the time variation of the electrical motional resistance in the vicinity of the mechanical sensor resonant frequency were performed as the quartz crystal resonator was either coated with the continuous polymer phase or polymer plus cell suspensions. Cell adhesion processes on these surfaces was investigated by cell counting and the quartz resonator-based technique. Inhibition of fibroblast McCoy adhesion onto thin polymer films of various chemical compositions was analyzed and discussed in the perspective of a possible application of these bioactive polymers to fabricate intraocular lenses able to prevent secondary cataract phenomena.

Biocompatible Materials↗

PubMed2005

Surface characterization of silver-doped bioactive glass.

A bioactive glass belonging to the system SiO(2)-CaO-Na(2)O was doped with silver ions by ion exchange in molten salts as well as in aqueous solution. The ion exchange in the solution was done to check if it is possible to prepare an antimicrobial material using a low silver content. The doped glass was characterized by means of X-ray diffraction, SEM observation, EDS analysis, bioactivity test (soaking in a simulated body fluid), leaching test (GFAAS analyses) and cytotoxicity test. It is demonstrated that these surface silver-doped glasses maintain, or even improve, the bioactivity of the starting glass. The measured quantity of released silver into simulated body fluid compares those reported in literature for the antibacterial activity and the non-cytotoxic effect of silver. Cytotoxicity tests were carried out to understand the effect of the doped surfaces on osteogenic cell adhesion and proliferation.

Anti-Bacterial Agents↗

PubMed2005

Synthesis of a poly(L-lysine)-calcium phosphate hybrid on titanium surfaces for enhanced bioactivity.

Titanium has been a successful implant material owing to its excellent strength to weight ratio, toughness, and bioinert oxide surface. Significant progress has been made on the improvement of titanium's bioactivity by coating its oxide surface with calcium phosphates and bioactive molecules. Here, we report on the coating of titanium with a poly(L-lysine)-calcium phosphate hybrid material with a nanoscale texture. This hybrid coating was grown by first nucleating seed crystals of calcium phosphate, directly on the Ti surface and then exposing this surface to solutions containing Ca(2+), PO(4)(3-), and poly(L-lysine). The resultant hybrid coating was characterized by electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, and elemental analysis. This material contained 14% by weight poly(L-lysine), and this organic component decreased greatly the dimensions of the surface features, thus enhancing surface area relative to the inorganic control. The highly textured hybrid material was more susceptible than the control to acidic and enzymatic degradation. The amino acid cysteine was covalently linked to the hybrid material, demonstrating the potential of this coating for further functionalization. These hybrid coatings may prove useful in enhancing the bioactivity of titanium.

Calcium Chloride↗

PubMed2005

Compound changes and tooth mineralization effects of glass ionomer cements containing bioactive glass (S53P4), an in vivo study.

In this study, modifications of glass ionomer cements (GICs) were made by adding bioactive glass (BAG) to GIC to obtain bioactive restorative materials. This study used SEM, EDS and visual analysis to examine the bioactivity and the ability of the study materials to mineralize dentin. Conventional cure and resin-modified light-curing GIC were used. The materials consisted of powder and liquid. Three experimental materials were made by mixing 10-30 wt% of BAG powder with GIC powders. Commercially available GIC without BAG were used as controls. Class III restorations were made in altogether 62 intact beagle dog teeth, and the operation was performed under general anesthesia. The restorations were followed clinically for 1, 3 or 6 weeks. Resin-modified GIC containing BAG showed uniform CaP surface formation on the restorations. Mineral depositions in the close vicinity of the restoration-dentin interface and in deeper parts of dentin tubules were also noticed in resin-modified GIC containing BAG particles. It can be concluded that resin-modified GIC containing BAG have good potential in clinical applications where enhanced mineralization is expected.

Analysis of Variance↗

PubMed2005

Improvement of surface bioactivity on titanium by water and hydrogen plasma immersion ion implantation.

We have investigated the surface bioactivity of titanium after water and hydrogen plasma immersion ion implantation. Plasma immersion ion implantation (PIII) excels in the surface treatment of components possessing a complicated shape such as medical implants. In addition, water and hydrogen PIII has been extensively studied as a method to fabricate silicon-on-insulator (SOI) substrates in the semiconductor industry and so it is relatively straightforward to transfer the technology to the biomedical field. In our investigation, water and hydrogen were plasma-implanted into titanium sequentially. Our objective is that water PIII introduces near-surface damages that trap hydrogen implanted in the subsequent step to improve the surface bioactivity while the desirable bulk properties of the materials are not compromised. Ti-OH functional groups can be detected on the (H(2)O+H(2))-implanted titanium surface by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. After incubation in simulated body fluids (SBF) for cytocompatibililty evaluation in vitro, bone-like hydroxyapatite was found to precipitate on the (H(2)O+H(2)) implanted samples while no apatite was found on titanium samples plasma implanted with water or hydrogen alone. Human osteoblast cells were cultured on the (H(2)O+H(2))-implanted titanium surface and they exhibited good adhesion and growth. Our results suggest a practical means to improve the surface bioactivity and cytocompatibility of medical implants made of titanium.

Biocompatible Materials↗

PubMed2006

How useful is SBF in predicting in vivo bone bioactivity?

The bone-bonding ability of a material is often evaluated by examining the ability of apatite to form on its surface in a simulated body fluid (SBF) with ion concentrations nearly equal to those of human blood plasma. However, the validity of this method for evaluating bone-bonding ability has not been assessed systematically. Here, the history of SBF, correlation of the ability of apatite to form on various materials in SBF with their in vivo bone bioactivities, and some examples of the development of novel bioactive materials based on apatite formation in SBF are reviewed. It was concluded that examination of apatite formation on a material in SBF is useful for predicting the in vivo bone bioactivity of a material, and the number of animals used in and the duration of animal experiments can be reduced remarkably by using this method.

Animals↗

PubMed2006

Bioactivity and cytocompatibility of zirconia (ZrO(2)) films fabricated by cathodic arc deposition.

Zirconium oxide thin films were fabricated on silicon wafers using a filtered cathodic arc system in concert with oxygen plasma. The structure and phase composition of the zirconium oxide thin films were characterized by atomic force microscopy (AFM), X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), and transmission electron microscopy (TEM). The bioactivity was assessed by investigating the formation of apatite on the film surface after soaking in simulated body fluids. Bone marrow mesenchymal stem cells (BMMSC) were used to further evaluate the cytocompatibility of the materials. The results indicate that the films are composed of stoichiometric ZrO(2) and the composition is quite uniform throughout the thickness. Bone-like apatite can be formed on the surface of the ZrO(2) thin film in our SBF immersion experiments, suggesting that the surface is bioactive. The outermost layer of the ZrO(2) thin film comprises nano-sized particles that can be identified by AFM images taken on the thin film surface and TEM micrographs obtained from the interface between the ZrO(2) thin film and apatite layer. The nanostructured surface is believed to be the key factor that apatite is induced to precipitate on the surface. Bone marrow mesenchymal stem cells are observed to grow and proliferate in good states on the film surface. Our results show that ZrO(2) thin films fabricated by cathodic arc deposition exhibit favorable bioactivity and cytocompatibility.

Animals↗

PubMed2006

The effect of starch and starch-bioactive glass composite microparticles on the adhesion and expression of the osteoblastic phenotype of a bone cell line.

There is a clear need for the development of microparticles that can be used simultaneously as carriers of stem/progenitor cells and as release systems for bioactive agents, such as growth factors or differentiation agents. In addition, when thinking on bone-tissue-engineering applications, it would be very useful if these microparticles are biodegradable and could be made to be bioactive. Microparticles with all those characteristics could be cultured together with adherent cells in appropriate bioreactors to form in vitro constructs that can then be used in tissue-engineering therapies. In this work, we have characterized the response of MC3T3-E1 pre-osteoblast cells to starch-based microparticles. We evaluated the adhesion, proliferation, expression of osteoblastic markers and mineralization of cells cultured at their surface. The results clearly show that MC3T3-E1 pre-osteoblast cells adhere to the surface of both polymeric and composite starch-based microparticles and express the typical osteoblastic marker genes. Furthermore, the cells were found to mineralize the extracellular matrix (ECM) during the culture period. The obtained results indicate that starch-based microparticles, known already to be biodegradable, bioactive and able to be used as carriers for controlled release applications, can simultaneously be used as carriers for cells. Consequently, they can be used as templates for forming hybrid constructs aiming to be applied in bone-tissue-engineering applications.

Biocompatible Materials↗

PubMed2006

Flavonoid-mediated inhibition of intestinal ABC transporters may affect the oral bioavailability of drugs, food-borne toxic compounds and bioactive ingredients.

The transcellular transport of ingested food ingredients across the intestinal epithelial barrier is an important factor determining bioavailability upon oral intake. This transcellular transport of many chemicals, food ingredients, drugs or toxic compounds over the intestinal epithelium can be highly dependent on the activity of membrane bound ATP binding cassette (ABC) transport proteins, able to export the compounds from the intestinal cells. The present review describes the ABC transporters involved in the efflux of bioactive compounds from the intestinal cells, either to the basolateral blood side, facilitating absorption, or back into the intestinal lumen, reducing bioavailability. The role of the ABC transporters in intestinal transcellular uptake also implies a role for inhibitors of these transporters in modulation of the bioavailability upon oral uptake. The present paper focuses on the role of flavonoids as important modulators or substrates of intestinal ABC transport proteins. Several examples of such an effect of flavonoids are presented. It can be concluded that flavonoid-mediated inhibition of ABC transporters may affect the bioavailability of drugs, bioactive food ingredients and/or food-borne toxic compounds upon oral uptake. All together it appears that the flavonoid-mediated interactions at the level of the intestinal ABC transport proteins may be an important mechanism for unexpected food-drug, food-toxin or food-food interactions. The overview also indicates that future studies should focus on i) in vivo validation of the flavonoid-mediated effects on bioavailability of drugs, toxins and beneficial bioactive food ingredients detected in in vitro models, and on ii) the role of flavonoid phase II metabolism in modulating the activity of the flavonoids to act as ABC transporter inhibitors and/or substrates.

ATP-Binding Cassette Transporters↗

PubMed2005

Characterization of bioactive glycolipids from Scytonema julianum (cyanobacteria).

Cyanobacteria serve as a rich source of novel bioactive metabolites. Few studies on glycolipids reported them as having specific biological activities. In this study, total lipids of Scytonema julianum, a filamentous cyanobacterium isolated from a Greek cave, were separated into neutral and phospho- and glycolipids, and the latter were further fractionated by high-performance liquid chromatography (HPLC). Each glycolipid fraction was tested in vitro for its ability to inhibit platelet-activating factor (PAF)- and thrombin-induced washed rabbit platelet aggregation and/or to cause platelet aggregation. The structures of the most active fractions were elucidated by biological assays, by chemical determinations and identified by electrospray mass spectrometry. One fraction was a potent inhibitor of PAF-induced platelet aggregation. Structural studies of this fraction indicated the existence of a phosphoglyco-analog of acyl-sphingosine. Two fractions causing platelet aggregation were detected and identified as phosphoglycolipids. The first one was identified as a phosphoglyco-analog of acyl-acetylated sphingosine and the second one as a glyco-analog of phosphatidylglycerol. The presence of the above bioactive compounds demonstrates new types of lipids in cyanobacteria in regard to the structure and biological activity. In addition, the identified bioactive lipids may contribute to the allergic character of cyanobacteria.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗

PubMed2005

Bioactive polar lipids from Chroococcidiopsis sp. (Cyanobacteria).

Many studies indicate that various bioactive metabolites subsist in cyanobacteria. Glycolipids of cyanobacteria are reported as molecules that exert specific bioactivities. In this study, total lipids of Chroococcidiopsissp., a coccoid cyanobacterium isolated from a Greek cave, were separated into neutral and polar-lipids and the latter were further fractionated by high-performance liquid chromatography (HPLC). Each polar lipid fraction was tested in vitro for its ability to inhibit platelet-activating factor (PAF)- and thrombin-induced washed rabbit platelet aggregation and/or to cause platelet aggregation. The structures of the most active fractions were elucidated by biological assays and identified by electrospray mass spectrometry. One fraction was a potent inhibitor of PAF-induced platelet aggregation. Structural studies of this fraction indicated the existence of phospho-glyco analog of ceramide. Another fraction that was a potent inhibitor of PAF- as well as of thrombin-induced platelet aggregation was structurally elucidated as a phospho-acetylated glyco-analog of diglyceride. The fraction that induced platelet aggregation was identified as a phospho-acetylated-glyco analog of ceramide. These novel bioactive polar lipids in cyanobacteria in regard to the structure and biological activity may contribute to the allergic character of cyanobacteria.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗

PubMed2006

Engineering human IL-18 with increased bioactivity and bioavailability.

Cytokines in plasmid form can act as potent adjuvants when co-administered with DNA vaccines, resulting in an enhanced immune response to the DNA-encoded antigen. This is true of interleukin-18 (IL-18), which has been shown to serve as an adjuvant in conjunction with certain DNA vaccines. To determine if the properties of IL-18 could be optimized for use as a DNA vaccine adjuvant, a model of IL-18/IL-18R binding was developed to identify variants of human IL-18 that were predicted to improve receptor interactions and potentially bioactivity. The linkage of mature IL-18 to a secretion signal sequence provided improved protein expression from mammalian cells and signal peptidase cleavage of this protein produced the authentic N-terminus. The IL-18 variant proteins secreted this way were bioactive, as demonstrated by their ability to induce interferon gamma (IFNgamma) expression by human peripheral blood mononuclear cells (PBMCs) and to bind to IL-18R, as demonstrated by BIAcore analysis. The IL-18 variants were inhibited by IL-18 binding protein (IL-18BP), the soluble inhibitor of IL-18, as measured by neutralization of the IFNgamma response in PBMCs. One variant, V11I/T63A, demonstrated increases both in bioactivity and mammalian cell expression as compared to native IL-18, indicating that this molecule may be particularly well suited for use as a DNA-encoded vaccine adjuvant.

Amino Acid Sequence↗

PubMed2005

Increased serum estrogenic bioactivity in three male newborns with ambiguous genitalia: a potential consequence of prenatal exposure to environmental endocrine disruptors.

In the past 15 years, anomalies of male sexual differentiation have greatly increased in both wildlife and humans in different parts of the world. Environmental endocrine disruptors have been implicated in the dramatic rise in neonatal ambiguous genitalia with variable rates of severity, such as micropenis, cryptorchidism, and isolated or associated hypospadias. Because most environmental pollutants, such as organochlorine pesticides, polychlorinated biphenyls, dioxins and furans, alkylphenol polyetholyethoxylates, and phytoestrogens and phtalates, have estrogenic and antiandrogenic activity, they are able to interfere with normal fetal male sexual differentiation. In a neonatal screening program of ambiguous genitalia, we had the opportunity to evaluate three newborns with male pseudohermaphroditism (MPH) whose mothers were exposed to endocrine disruptors during pregnancy. All had normal testosterone production after human chorionic gonadotrophin stimulation testing, suggesting androgen resistance or so-called idiopathic MPH. Sequences of the 5alpha reductase and androgen receptor genes were normal. Since environmental pollutants are known for their estrogenic activity and can be released progressively from the adipose tissue where they accumulate, we detected their presence by measuring the estrogenic bioactivity of the newborns' serum with a recently developed ultrasensitive bioassay. We found higher estrogenic bioactivity in these newborns than in controls. In conclusion, the maternal exposure to environmental pollutants during pregnancy and high estrogenic bioactivity in the newborns' serum highly suggest that ambiguous genitalia are related to fetal exposure to endocrine disruptors.

Agriculture↗

PubMed2006

Design of homogeneous, monopegylated erythropoietin analogs with preserved in vitro bioactivity.

OBJECTIVE: Erythropoietin (Epo) bioactivity is significantly reduced by modification of lysine residues with amine-reactive reagents, which are the most commonly used reagents for attaching polyethylene glycols (PEGs) to proteins to improve protein half-life in vivo. The aims of this study were to determine whether Epo bioactivity can be preserved by targeting attachment of maleimide-PEGs to engineered cysteine analogs of Epo, and to determine whether the pegylated Epo cysteine analogs have improved pharmacokinetic properties in vivo. MATERIALS AND METHODS: Thirty-four Epo cysteine analogs were constructed by site-directed mutagenesis and expressed as secreted proteins in baculovirus-infected insect cells. Following purification, monopegylated derivatives of 12 cysteine analogs were prepared using 20-kDa maleimide-PEGs. In vitro biological activities of the proteins were measured in an Epo-dependent cell proliferation assay. Plasma levels of insect cell-expressed wild-type Epo (BV Epo) and a pegylated Epo cysteine analog were quantitated by ELISA following intravenous administration to rats. RESULTS: Biological activities of 17 purified Epo cysteine analogs and 10 purified pegylated Epo cysteine analogs were comparable to that of BV Epo in the in vitro bioassay. The only pegylated cysteine analogs that displayed consistently reduced in vitro bioactivities were substitutions for lysine residues, PEG-K45C and PEG-K154C. The pegylated Epo cysteine analog had a slower initial distribution phase and a longer terminal half-life than BV Epo in rats, but the majority of both proteins were cleared rapidly from the circulation. CONCLUSIONS: Targeted attachment of maleimide-PEGs to engineered Epo cysteine analogs permits rational design of monopegylated Epo analogs with minimal loss of in vitro biological activity. Insect cell-expressed Epo proteins are cleared rapidly from the circulation in rats, possibly due to improper glycosylation. Site-specific pegylation appears to improve the pharmacokinetic properties of Epo.

Amino Acid Substitution↗

PubMed2006

Lipidic implants for controlled release of bioactive insulin: effects on cartilage engineered in vitro.

Controlled release systems for growth factors and morphogens are potentially powerful tools for the engineering or the treatment of living tissues. However, due to possible instabilities of the protein during manufacture, storage, and release, in the development of new release systems it is paramount to investigate into the maintenance of bioactivity of the protein. Within this study, recently developed protein releasing lipid matrix cylinders of 2 mm diameter and 2 mm height made from glycerol tripalmitate were manufactured in a compression process without further additives. Insulin in different concentrations (0.2%, 1%, and 2%) served as model protein. The bioactivity of the protein released from the matrices was investigated in a long-term cartilage engineering culture for up to four weeks; additionally, the release profiles were determined using ELISA. Insulin released from the matrices increased the wet weights of the cartilaginous cell-polymer constructs (up to 3.2-fold), the amount of GAG and collagen in the constructs (up to 2.4-fold and 3.2-fold, respectively) and the GAG and collagen content per cell (1.8-fold and 2.5-fold, respectively), compared to the control. The dose-dependent effects on tissue development correlated well with release profiles from the matrices with different insulin loading. In conclusion, the lipid matrices, preserving the bioactivity of incorporated and released protein, are suggested as a suitable carrier system for use in tissue engineering or for the localized treatment of tissues with highly potent protein drugs such as used in the therapy of brain cancer or neurodegenerative CNS diseases.

Animals↗

PubMed2005

Inhibition of prostate cancer cell growth by an avocado extract: role of lipid-soluble bioactive substances.

Although the avocado is known as a rich source of monounsaturated fatty acids, there has been far less attention given to its content of other bioactive substances including carotenoids, which might contribute to cancer preventive properties similar to those attributed to other fruits and vegetables. The yellow-green color of the avocado prompted us to study the carotenoid content of this fruit using established methods in our laboratory. The California Hass avocado (Persea americana Mill.) was selected for study, because it is the most commonly consumed variety in the southwest United States. These avocados were found to contain the highest content of lutein among commonly eaten fruits as well as measurable amounts of related carotenoids (zeaxanthin, alpha-carotene, and beta-carotene). Lutein accounted for 70% of the measured carotenoids, and the avocado also contained significant quantities of vitamin E. An acetone extract of avocado containing these carotenoids and tocopherols was shown to inhibit the growth of both androgen-dependent (LNCaP) and androgen-independent (PC-3) prostate cancer cell lines in vitro. Incubation of PC-3 cells with the avocado extract led to G(2)/M cell cycle arrest accompanied by an increase in p27 protein expression. Lutein alone did not reproduce the effects of the avocado extract on cancer cell proliferation. In common with other colorful fruits and vegetables, the avocado contains numerous bioactive carotenoids. Because the avocado also contains a significant amount of monounsaturated fat, these bioactive carotenoids are likely to be absorbed into the bloodstream, where in combination with other diet-derived phytochemicals they may contribute to the significant cancer risk reduction associated with a diet of fruits and vegetables.

Blotting, Western↗

PubMed2005

Simultaneous quantification of 12 bioactive components of Ligusticum chuanxiong Hort. by high-performance liquid chromatography.

A sensitive and specific HPLC-UV method has been developed, for the first time, to simultaneously quantify 12 bioactive ingredients in Ligusticum chuanxiong Hort. (Rhizoma Chuanxiong). This assay was fully validated in respect to precision, accuracy and sensitivity. This method was successfully applied to quantify twelve ingredients in six different Chuanxiong samples. The results demonstrated significant variations in the total content and quantity of each of the main bioactive compounds in different herbs, indicating that quality control of bioactive ingredients in Chuanxiong is critical to ensure its clinical benefits. This assay can be readily utilized as quality control method for Chuanxiong.

Chromatography, High Pressure Liquid↗

PubMed2006

Determination of androgen bioactivity in human serum samples using a recombinant cell based in vitro bioassay.

The present study describes the development and optimization of a cell-based reporter assay for the determination of androgen bioactivity levels in human serum samples. Towards this end, human embryonic kidney (HEK) 293 cells were cotransfected with two plasmids, one encoding the mouse mammary tumor virus (MMTV)-driven luciferase reporter gene and the other the SV40 promoter-driven human androgen receptor (AR), and a stable cell line, expressing human AR and androgen-responsive luciferase was established by antibiotic selection. RT-PCR confirmed proper transcription and stable integration of AR in the cell line. On stimulation of the cells with testosterone (T) for 24h, luciferase activity was increased in dose-dependent fashion up to 15-fold, with the minimum effective concentration of T being 0.03 nmol/l. T-induced reporter gene expression of the cells was inhibited by the anti-androgens cyproterone acetate and hydroxyflutamide. Upon stimulation with non-androgenic steroids like estradiol, progesterone, dexamethasone and cortisol, the cells showed only marginal activity except for a weak glucocorticoid effect at high concentration. The cells also responded well to various chemicals (mostly pesticides, their metabolites and common industrial chemicals) with known androgenic activity. The cell line was further optimized by measuring the levels of androgens from male and female serum samples. Our data indicated that the cells can be used to estimate androgen bioactivity in serum of females suffering from polycystic ovary syndrome (PCOS) and males of different age groups. In conclusion, we demonstrate that the bioassay based on this cell line provides a reliable method to determine serum levels of androgen bioactivity from biological samples even at the low concentrations present in female circulation. The 96-well plate format makes the assay suitable for high throughput measurements.

Androgens↗