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At least 1,351 records · Page 75Linked to original sources
PubMed2001

The usefulness of the modified extra-oral vacuum aspirator (EOVA) from household vacuum cleaner in reducing bacteria in dental aerosols.

AIMS AND OBJECTIVES: Currently, as a preventive measure against air contamination caused by dental procedures, dust-collecting aspirators such as an extra-oral vacuum aspirator (EOVA) are coming into general use. In this study, we tested the ability of a modified EOVA that uses a household vacuum machine. DESIGN AND SETTING: The study was conducted in two parts. First, the modified EOVA was tested for its ability to eliminate an Escherichia coli aerosol generated in a manikin. Second, the device was tested for its ability to remove the aerosol generated by dental treatment procedures, scaling and drilling a tooth, on human subjects. RESULTS: There was a statistically significant reduction in both the E. coli aerosol and the oral bacterial aerosol during dental treatment procedures. CONCLUSION: The modified EOVA machine is highly effective in preventing air contamination by dental procedures. Its main advantages are that it can easily be modified for use with any dental unit and it is relatively inexpensive.

Aerosols↗
PubMed1995

Immobilization of heparin oligosaccharides onto radiofrequency plasma modified pyrolytic carbon-coated graphite.

Heparin oligosaccharides with different anticoagulant activities were prepared and immobilized onto pyrolytic carbon coated graphite (PC) heart valve materials commonly used in mechanical heart valve prostheses. Prior to immobilization, PC surfaces were modified by radiofrequency plasma polymerized N-vinyl-2-pyrrolidone (PPNVP) thin films (approximately 100 nm) and derivatized to provide surface hydroxyl groups. Cleaved, low affinity heparin (C-heparin) with factor Xa inhibition activity of 107 to 130 IU/mg, was prepared by partial deaminative cleavage of commercial crude heparin, and high-affinity heparin (HA-heparin) with factor Xa inhibition activity of 550 to 1000 IU/mg was prepared by fractionation of C-heparin using agarose-ATIII affinity chromatography. C-heparin and HA-heparin were immobilized to surface modified PC by reductive amination. Anticoagulant activity of the heparin immobilized surfaces was determined by chromogenic assay for the inhibition of factor Xa. Highest surface anticoagulant activity was measured on C-heparin immobilized surfaces (64.0 +/- 7.3 mIU/cm2) compared with HA-heparin immobilized surfaces (27.2 +/- 12.2 mIU/cm2), suggesting higher binding of C-heparin than HA-heparin on the modified PC surfaces. Immobilized surfaces were evaluated under dynamic flow conditions, by subjecting samples to shear stress of up to 206 dyn/cm2 in the presence of 5% albumin solution or human plasma. Anticoagulant activity of the immobilized heparin was retained, although reduced, and the modified surfaces showed evidence for protein resistance.

Anticoagulants↗
PubMed2002

Interaction of fibrinogen with surfaces of end-group-modified polyurethanes: a surface-specific sum-frequency-generation vibrational spectroscopy study.

Fibrinogen adsorption on polyurethanes with different surface-modifying end groups (SMEs) has been studied with sum-frequency-generation vibrational spectroscopy (SFG). The results show very different protein adsorption properties for different SMEs on the same backbone polymer. Fibrinogen binds weakly on the hydrophilic backbone of a poly(dimethyl siloxane) (PDMS)-modified polyurethane surface but leaves the hydrophobic PDMS part untouched. On sulfonate end-group-modified (SO(3(-) )) polyurethane surfaces, fibrinogen adsorbs well. However, on poly(ethylene oxide) (PEO)-modified surfaces, it adsorbs poorly. The protein-resistant character of PEO is probably due to steric repulsion. This work demonstrates the utility of SFG in the study of protein adsorption on polymeric biomaterials at the molecular level and the ability of SMEs to mediate protein adsorption.

Adsorption↗
PubMed1993

Immobilization of high-affinity heparin oligosaccharides to radiofrequency plasma-modified polyethylene.

Oligosaccharides of heparin with high affinity for antithrombin III (ATIII) have been immobilized onto surface-modified NHLBI Primary Reference low density polyethylene (PE). PE was modified by radiofrequency plasma polymerized (< 150 nm thick) films derived from N-vinyl-2-pyrrolidone (PPNVP) or allyl alcohol (PPAA), and coupled by chemical derivatization to either 3-aminopropyltriethoxysilane or amino-terminated poly(ethylene oxide). High affinity heparin oligosaccharides (HA-heparin, anti-factor Xa activity of 592 +/- 120 IU/mg) prepared by partial deaminative cleavage of commercial crude heparin and fractionated by agarose-ATIII affinity chromatography, were immobilized to surface-modified PE by reductive amination. The anticoagulant activity, as determined by a chromogenic assay for the inhibition of factor Xa, was estimated to be 30-70 mIU/cm2, with binding estimated to be 56-119 ng/cm2. The highest activity was obtained for the HA-heparin immobilized to PE modified by PPNVP with a PEO spacer. Visual confirmation of ATIII binding to immobilized HA-heparin was demonstrated by a gold-labeled double antibody method with imaging by SEM.

1-Propanol↗
PubMed1995

Human monocyte/macrophage adhesion and cytokine production on surface-modified poly(tetrafluoroethylene/hexafluoropropylene) polymers with and without protein preadsorption.

To study surface property-dependent human monocyte adhesion and cytokine (IL-1 beta, IL-6, TNF-alpha) production, poly(tetrafluoroethylene/hexafluoropropylene) (FEP) polymer was modified to exhibit neutral, anionic, or cationic properties by incorporating amide (CONH2) and/or carboxyl (COOH) or aminoethyl amide [CONH(CH2CH2NH)nCH2CH2NH2] groups on the surface. Monocyte adhesion on surface-modified FEP polymers and cytokines released by monocytes/macrophages (MC/MO) into the culture medium were compared to control tissue culture polystyrene (TCPS) at days 1 and 8. On day 1, the neutral surface FEP polymer with incorporated amide (NH2) groups showed the greatest inhibition of adhesion, 89% (P < .01), and cytokine production (IL-1 beta with 58%, IL-6 with 70%, and TNF-alpha with 39%) compared to control TCPS. In contrast, the highly cationic [CONH(CH2CH2NH)nCH2CH2NH2] surface did not show significant (P > .01) inhibition of monocyte adhesion and cytokine production. When fibrinogen or IgG was preadsorbed to the surface, the inhibitory effects of the neutral surface FEP polymer on monocyte adhesion and cytokine production were not altered. In addition, other surface-modified FEP polymers showed similar inhibition of monocyte adhesion and cytokine production compared to TCPS. Specifically, as the incorporation of carboxyl (COOH) group content increased on FEP polymer surfaces, monocyte adhesion and cytokine production were also increased on day 1 with IgG preadsorption. On day 8, all surface-modified FEP polymers showed significant (P < .01) inhibition of monocyte adhesion when fibrinogen or IgG was preadsorbed. However, without protein (fibrinogen or IgG) preadsorption, monocyte adhesion was not significantly inhibited compared to control TCPS. In addition, cytokine production detected by ELISAs on day 8 showed no detectable levels of IL-1 beta and significantly decreased levels of IL-6 compared to day 1 for all tested polymers, with or without protein preadsorption. Interestingly, the level of TNF-alpha production on day 8 remained high although not as high as on day 1. Based on these results, we suggest that FEP polymers with neutral hydrophilic surface properties may adhere and activate the least number of monocytes, which are important mediators of biocompatibility.

Adsorption↗
PubMed2003

Human bone marrow stromal cell and ligament fibroblast responses on RGD-modified silk fibers.

Adhesion, spreading, proliferation, and collagen matrix production of human bone marrow stromal cells (BMSCs) on an RGD-modified silk matrix was studied. Anterior cruciate ligament fibroblasts (ACLFs) were used as a control cell source. Scanning electron microscopy (SEM) and MTT analyses demonstrated that the modified silk matrices support improved BMSC and ACLF attachment and show higher cell density over 14 days in culture when compared with the non-RGD-modified matrices. Collagen type I transcript levels (at day 7) and content (at day 14) was significantly higher on the RGD-modified substrate than on the nonmodified group. The ability of RGD-coupled silk matrices to support BMSC attachment, which leads to higher cell density and collagen matrix production in vitro, combined with mechanical, fatigue, and biocompatibility properties of the silk protein matrix, suggest potential for use of this biomaterial for tissue engineering.

Animals↗
PubMed2003

Porous polymer scaffolds surface-modified with arginine-glycine-aspartic acid enhance bone cell attachment and differentiation in vitro.

This study was designed to determine if the surface modification of porous poly(lactic acid) (PLA) scaffolds would enhance osteogenic precursor cell (OPC) attachment, growth, and differentiation. A covalently grafted amino group (-NH(2)), poly(L-lysine) (PLL), and the peptide arginine-glycine-aspartic acid (RGD) were selected for the evaluation. The hypothesis was that surface modification would have a positive impact on cell-substratum interactions. The experiment was performed by OPC cells being placed on PLA films and scaffolds modified with NH(2), PLL, or RGD in tissue culture media. OPC attachment to PLA films was assessed after 24 h of incubation. The growth and differentiation of the adherent OPCs on porous PLA scaffolds were assessed after 14 and 28 days for alkaline phosphatase (APase) activity and calcium levels, both of which increase as OPCs differentiate into mature bone cells. All assays were accomplished in triplicate, and data were tested with post hoc orthogonal contrasts (i.e., Fisher's least significant difference) at p < or = 0.05. The PLA film surface-modified with RGD showed better OPC cell attachment than the other films. The cells on the PLA scaffolds surface-modified with RGD also exhibited an increase in APase activity and calcium levels in comparison with those on other scaffolds. This difference was apparent at both time intervals and was especially evident in the tissue culture media containing an osteogenic supplement. The results of this study indicate that modifying the surface of PLA polymer scaffolds with RGD enhances bone cell attachment and differentiation and may improve their ability to regenerate bone tissue more efficiently in wound models.

Absorbable Implants↗
PubMed2003

Monocyte/macrophage interactions with base and linear- and star-like PEG-modified PEG-poly(acrylic acid) co-polymers.

Poly(ethylene glycol):poly(acrylate) PEG-g-PA co-polymers were made that inhibited nonspecific protein and cellular adhesion. PEG-g-PA co-polymers were then covalently modified with either cell adhesion peptides or fragments of antibodies to monocyte/macrophage integrin receptors (anti-VLA4, anti-beta(1), anti-beta(2), and anti-CD64) known to enhance macrophage adhesion and, perhaps, modulate their activation. Peptides were either directly conjugated to the base material or linked by way of PEO-star tethers. Fragments of the antibody region containing the antigen-binding site (Fab' fragments) were coupled to other PEG-g-PA samples using the sulhydryl end groups on Fab' fragments to amine-bearing PEO stars. Macrophage adhesion rates, phagocytic response (oxidative burst), and cytokine expression were determined for each PEG-g-PA material. Luminol-enhanced chemiluminescence was used as a semiquantitative indication of monocyte-macrophage phagocytic activation (oxidative burst). Macrophage cytokine expression in response to control, base, and modified materials was determined by ELISAs for TNF-alpha, IL-1 beta, IL-6, and IL-8. Tissue culture poly(styrene) (TCPS)-mediated the greatest number of adherent monocyte/macrophage cells relative to PEG-g-PA materials. Both YRGDS and YEILDV peptides, whether directly or indirectly (via StarPEO) conjugated to PEG-g-PA, increased adhesion versus controls. Fab' fragments of all four antibodies also promoted enhanced adhesion versus controls. Fab'StarPEO materials presented two orders of magnitude fewer ligands per surface unit area than peptide star materials (10(8) vs. 10(10)), but were able to adhere similar numbers of cells. For surfaces presenting Fab'(VLA-4) or YEILDV, both of which may both bind to a cell's VLA-4 receptor, the Star:VLA4 surface showed a greater number of adherent monocyte/macrophages. This result suggests that the Fab' had a higher affinity to the cell receptor than a corresponding minimal peptide binding sequence. All materials exhibited low oxidative burst (luminescence counts per minute, LCPM) per cell DNA without the addition of exogenous stimuli (LCPM/DNA < 100). Directly conjugated peptide materials, poly(propylene) (PP), and TCPS showed the lowest levels of LCPM/DNA without the addition of exogenous stimulus (LCPM/DNA < 20). There was no correlation between LCPM/DNA ratios, with and without added LPS stimulus, versus the individual substrates. Monocyte/macrophages adherent to TCPS substrata showed the overall highest stimulatory potential in cytokine expression response to exogenous LPS, followed by PP > PEG-g-PA > StarPEO. Cells adherent to peptide-modified materials and Fab'-modified materials were overall less stimulated. The method of presenting the peptides (i.e., directly or via Star PEO) influenced the level of cytokine secreted by the adherent macrophage.

Acrylates↗
PubMed2004

Endothelial cell functions in vitro cultured on poly(L-lactic acid) membranes modified with different methods.

We recently developed several methods to enhance the cell-polymer interactions. Optimal conditions for each method have been revealed separately by in vitro cell culture. As a practical consideration for construction of tissue-engineered organs, it is necessary to consider which is the most suitable and convenient in clinical applications. To compare the efficiency of these methods with respect to cell functions, poly-L-lactic acid (PLLA) was selected as matrix being modified by 1) aminolysis (PLLA-NH(2)), 2) collagen immobilization with GA (PLLA-GA-Col), 3) chondroitin sulfate (CS)/collagen layer-by-layer (LBL) assembly (PLLA-CS/Col), 4) photo-induced grafting copolymerization of hydrophilic methacrylic acid (MAA) (PLLA-g-PMAA), and 5) further immobilization of collagen with 1-ethyl-3-(3-dimethylamino propyl) carbodiimide hydrochloride (EDAC) (PLLA-g-PMAA-Col). The surface wettability of the modified PLLA was determined by water contact angle measurements. The cell response to the modified PLLA was quantitatively assessed and compared by using human umbilical endothelial cells (HUVECs) culture. Our results indicate that all the modifications can improve the cytocompatibility of PLLA (e.g., cells can attach with spreading morphology, proliferate and secret vWF and 6-keto-PGF(1 alpha)). All the collagen-modified PLLA showed more positive cell response than those purely aminolyzed or PMAA grafted. Among all the methods, collagen immobilization by LBL assembly or GA bridging after aminolysis is more acceptable for the convenience and applicability to scaffolds.

Biocompatible Materials↗
PubMed2005

Biostability and macrophage-mediated foreign body reaction of silicone-modified polyurethanes.

In this study, the effect of soft segment chemistry on the phase morphology and in vivo response of commercial-grade poly(ether urethane) (PEU), silicone-modified PEU (PEU-S), poly(carbonate urethane) (PCU), and silicone-modified PCU (PCU-S) elastomers were examined. Silicone-modified polyurethanes were developed to combine the biostability of silicone with the mechanical properties of PEUs. Results from the infrared spectroscopy confirmed the presence of silicone at the surface of the PEU-S and PCU-S films. Atomic force microscopy phase imaging indicated that the overall two-phase morphology of PEUs, necessary for its thermoplastic elastomeric properties, was not disrupted by the silicone modification. After material characterization, the in vivo foreign body response and biostability of the polyurethanes were studied using a subcutaneous cage implant protocol. The results from the cage implant study indicated that monocytes adhere, differentiate to macrophages which fuse to form foreign body giant cells on all of the polyurethanes. However, the silicone-modified surfaces promoted apoptosis of adherent macrophages at 4 days and high levels of macrophage fusion after 21 days. These results confirm that the surface of a biomaterial may influence the induction of apoptosis of adherent macrophages in vivo and are consistent with previous cell culture studies of these materials. This study validates the use of our standard cell culture protocol to predict in vivo behavior and further supports the hypothesis that interleukin-4 is the primary mediator of macrophage fusion and foreign body giant cell formation in vivo. The impact of these findings on the biostability of polyurethanes is the subject of current investigations. Attenuated total reflectance-Fourier transform infrared analysis of explanted specimens provided evidence of chain scission and crosslinking at the surface of all of the polyurethanes. The silicone modification did not fully inhibit the oxidative biodegradation of the polyether or polycarbonate soft segments; however, the rate of chain scission of PEU-S and PCU-S seemed to be slower than the control polyurethanes. To verify this finding and to quantify the rate of chain scission in order to predict long-term biostability, an in vitro environment that simulated the microenvironment at the adherent cell-material interface was used to accelerate the biodegradation of the polyurethanes. Polyurethane films were treated in vitro for up to 36 days in 20% hydrogen peroxide/0.1M cobalt chloride solution at 37 degrees Celsius. Characterization with attenuated total reflectance-Fourier transform infrared and scanning electron microscopy showed soft segment and hard segment degradation consistent with the chemical changes observed after long-term in vivo treatment. The biostability ranking of these four materials based on rate of chain scission and surface pitting was as follows: PEU < PEU-S PCU < PCU-S. The silicone modification increased the biostability of the PEU and PCU elastomers while maintaining the thermoplastic elastomeric properties.

Biocompatible Materials↗
PubMed2007

Fibrinogen adsorption and platelet lysis characterization of fluorinated surface-modified polyetherurethanes.

A polyetherurethane (PU) was modified using fluorinated surface-modifying macromolecules (SMMs). A double radiolabel method was used simultaneously to measure the number of adhered platelets ((51)Cr) and the quantity of adsorbed Fg ((125)I), in a cone-and-plate instrument. The objectives were to determine if adsorbed Fg levels correlated to platelet adhesion on the surfaces, and to assess if any reductions in platelet adhesion for the SMM-treated surfaces resulted from surface-induced platelet lysis, rather than changes directly related to lower platelet activation and attachment on the novel surfaces. Platelet lysis was determined from lactate dehydrogenase (LDH) and unbound (51)Cr released into plasma isolated from whole blood exposed to test materials. The corresponding Fg adsorption, evaluated under the same platelet adhesion conditions, did not account for the reduced platelet adhesion on the treated surfaces. LDH and (51)Cr platelet release were very low and indicated no statistically significant differences between the materials. It was therefore concluded that platelet lysis did not contribute to the reduction in platelet adhesion characteristic observed on the SMM-treated surfaces. More importantly, the work emphasizes that the platelet activation cannot be inferred to by assessing the quantity of fibrinogen as is commonly done in the literature. The finding suggests a much more complex mechanism of action for the SMM surface modifiers. On-going work is investigating other Fg parameters such as protein binding affinity and protein conformational state in order to establish the mechanism by which the fluorinated surface modifiers may be reducing platelet adhesion via intermediary changes in initial protein adsorption.

Adsorption↗
PubMed2007

Targeting microspheres and cells to polyethylene glycol-modified biological surfaces.

It has previously been demonstrated that damaged arterial tissue can be acutely modified with protein-reactive polyethylene glycol (PEG) to block undesirable platelet deposition. This concept might be expanded by employing PEG-biotin and its strong interaction with avidin for site-specific targeted delivery. Toward this end, cultured endothelial cells (ECs) were surface modified with PEG-biotin and the available biotin was quantified with flow cytometry. NeutrAvidin-coated microspheres and PEG-biotin modified ECs with NeutrAvidin as a bridging molecule were delivered under arterial shear stress to PEG-biotin modified ECs on a coverslip as well as scrape-damaged bovine carotid arteries. After incubation with a 10 mM solution for 1 min, 8 x 10(7) PEG-biotin molecules/EC were found and persisted for up to 120 h. Perfused microspheres adhered to NHS-PEG-biotin treated bovine carotid arteries with 60 +/- 16 microspheres/mm(2) versus 11 +/- 4 microspheres/mm(2) for control arteries (p < 0.015). Similarly, 22 +/- 5 targeted ECs/mm(2) adhered to NHS-PEG-biotin treated bovine carotid arteries versus 6 +/- 2 ECs/mm(2) for control arteries (p < 0.01). The targeting strategy demonstrated here might ultimately find application for drug delivery, gene therapy, or cell therapy where localization to specific labeled vascular regions is desired following catheter-based or surgical procedures.

Animals↗
PubMed2006

Modified p27 Kip1 is efficient in suppressing HER2-mediated tumorigenicity.

Cyclin-dependent kinase (CDK) inhibitor p27 Kip1, a haplo-insufficient tumor suppressor, is downregulated by oncogenic signal of HER2, a receptor tyrosine kinase oncogene. HER2 promotes mitogenic growth and transformation of cancer cells. HER2 signaling can enhance p27 Kip1 ubiquitination, thereby promoting p27 degradation and subsequent activation of CDK activity. p27 ubiquitination and degradation is enhanced by JAB1 binding as well as by phosphorylation on Thr187. In this study, we generated modified p27 proteins, which are mutated at Thr 187 or deleted at JAB1 binding domain. We applied these modified p27 genes as novel anticancer agents for HER2-overexpressing cells under the control of a tetracycline (tet)-regulated gene expression system. Induction of p27 T187A and p27 T187A DeltaJAB inhibits HER2-activated cell growth, CDK2 activity, cell proliferation, and transformation. Significantly, a modified protein (p27 T187ADeltaJAB) reduced the tumor volume in a HER2-overexpressing tumor model efficiently. These findings demonstrate the applicability of employing modified p27 proteins as a therapeutic intervention in HER2-overexpressing cancers.

Amino Acid Substitution↗
PubMed2003

Evaluation of a modified commercial assay in detecting antibody to hepatitis C virus in oral fluids and dried blood spots.

Oral fluid testing is an effective alternative to serum antibody testing for surveillance of human immunodeficiency virus (HIV) and hepatitis B infections, and is being extended to hepatitis C infections. The objective of this study was to determine and compare the sensitivity and specificity of a modified commercial assay for the detection of antibody to hepatitis C virus (anti-HCV) in oral fluids collected by two different oral fluid collection devices (the Epitope OraSure trade mark and Sarstedt Salivette ) and in dried fingerprick blood spots. In this study, 253 anti-HCV seropositive patients and 394 blood donors (all anti-HCV negative) were recruited between August 2000 and January 2001. Each participant provided oral fluid specimens by OraSure and Salivette, and at least one dried blood spot. Serum specimens were collected from the patients whenever possible. For those injecting drug users who did not provide a serum specimen, HCV status was established on the basis of previous testing. All the nonserum samples were tested for the presence of anti-HCV, using a modified Ortho HCV 3.0 SAVe enzyme-linked immunosorbent assay (ELISA) protocol. The recommended preliminary cutoffs for the modified ELISA were suboptimal. Further, the sensitivity, specificity, and positive and negative predictive values could be improved by varying the cutoff and taking into account the likely prevalence of HCV in the population under investigation. For instance, given a population with a 50% prevalence of anti-HCV, the optimal sensitivities of the modified assay on OraSure, Salivette, and dried blood spots were 92%, 83%, and virtually 100%, respectively, in contrast to 83%, 59%, and 99% using the preliminary cutoffs. The respective optimal specificities were 99%, 93%, and 100%. In conclusion, oral fluids collected by the OraSure device provide an extremely useful method to conduct public health surveillance of not only HIV, but also hepatitis C, among injecting drug users. In addition, dried blood spot specimens may be useful for surveillance and could be employed as a first line diagnostic specimen.

Blood Specimen Collection↗
PubMed1999

Effect of serum proteins on osteoblast adhesion to surface-modified bioactive glass and hydroxyapatite.

Previous studies indicate that modification of the surface of porous bioactive glass promotes osteoblast function. We hypothesize that bone formation on treated bioactive glass is due to the selective adsorption of serum attachment proteins. To test this hypothesis, we examined the profile of proteins adsorbed to treated bioactive glass and compared these proteins with those adsorbed to untreated bioactive glass and porous hydroxyapatite. Porous bioactive glass was treated with Tris-buffered electrolyte solution to generate a calcium phosphate-rich surface layer and then immersed in tissue-culture medium containing 10% serum. Proteins adsorbed to the ceramic surfaces were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot analysis. Porous hydroxyapatite bound a higher amount of total protein than did the other substrates. However, surface-modified porous bioactive glass adsorbed more fibronectin than did hydroxyapatite. The effect of serum-protein adsorption on osteoblast adhesion to bioactive glass and hydroxyapatite was also evaluated. Cell adhesion to porous bioactive glass that was surface-modified and serum-treated was significantly greater than to porous bioactive glass that was either surface-modified or serum-treated. Furthermore, cell adhesion to porous bioactive glass treated to form the dual layer of calcium phosphate and serum protein was significantly higher than adhesion to porous hydroxyapatite with adsorbed serum protein. Results of the study strongly suggest that adsorption of serum fibronectin to the surface of modified porous bioactive glass coated with calcium phosphate may be responsible for enhanced osteoblast adhesion.

Absorption↗
PubMed2006

In vitro characterization of peptide-modified p(AAm-co-EG/AAc) IPN-coated titanium implants.

Interpenetrating polymer networks (IPNs) of poly(acrylamide-co-ethylene glycol/acrylic acid) [p(AAm-co-EG/AAc)] functionalized with an -Arg-Gly-Asp- containing peptide derived from rat bone sialoprotein [bsp-RGD(15)] were grafted to titanium implants in an effort to modulate osteoblast behavior in vitro. Surface characterization data were consistent with the presence of an IPN, and ligand density measurements established that the range of peptide density on the modified implants spanned three orders of magnitude (0.01-20 pmol/cm2). In vitro biological characterization of the modified implants employing the primary rat calvarial osteoblast (RCO) model resulted in the identification of a critical ligand density (0.01<Gammacrit<0.1 pmol/cm2) for maximal support of the osteoblast phenotype. After 14 and 21 days, mineralization was greater on the 0.1 and 10 pmol/cm2 bsp-RGD(15) modified implants compared to the base titanium and other control surfaces. The observed effects were attributed to specific interactions with bsp-RGD(15) and support the concept that peptide-modified implants can enhance the kinetics of differentiation of the cells they contact. These results suggest that in vivo biological performance evaluation of these biomimetic implant surfaces is merited.

Acrylic Resins↗
PubMed2006

Strain and excursion of the sciatic, tibial, and plantar nerves during a modified straight leg raising test.

A modified straight leg raising (SLR) in which ankle dorsiflexion is performed before hip flexion has been suggested to diagnose distal neuropathies such as tarsal tunnel syndrome. This study evaluates the clinical hypothesis that strain in the nerves around the ankle and foot caused by ankle dorsiflexion can be further increased with hip flexion. Linear displacement transducers were inserted into the sciatic, tibial, and plantar nerves and plantar fascia of eight embalmed cadavers to measure strain during the modified SLR. Nerve excursion was measured with a digital calliper. Ankle dorsiflexion resulted in a significant strain and distal excursion of the tibial nerve. With the ankle in dorsiflexion, the proximal excursion and tension increase in the sciatic nerve associated with hip flexion were transmitted distally along the nerve from the hip to beyond the ankle. As hip flexion had an impact on the nerves around the ankle and foot but not on the plantar fascia, the modified SLR may be a useful test to differentially diagnose plantar heel pain. Although the modified SLR caused the greatest increase in nerve strain nearest the moving joint, mechanical forces acting on peripheral nerves are transmitted well beyond the moving joint.

Aged↗
PubMed2005

Kinetic parameters of urease immobilized on modified acrylonitrile copolymer membranes in the presence and absence of Cu(II) ions.

Poly(acrylonitrile-methylmethacrylate-sodium vinylsulfonate) membranes were subjected to seven different chemical modifications and the amount of the newly formed groups was measured for each membrane. Urease was then covalently immobilized onto the modified membranes and the amount of bound protein was determined. The kinetic parameters V(max) and K(m) of the immobilized urease were studied under static and dynamic conditions. Results showed that the rate of the enzyme reaction was higher for the membranes modified with NH(2)OH . H(2)SO(4), NH(2)NH(2) . H(2)SO(4), NaOH + EDA and NaOH + GA + EDA. It was confirmed that the reaction rate, measured under dynamic conditions, was higher than that one determined under static conditions. The influence of Cu(II) ions, as inhibitors, on the enzyme reaction kinetics (V(i) and K(i)) was also investigated. It turned out that the most sensitive membranes towards Cu(II) were those modified with NH(2)NH(2) . H(2)SO(4), NaOH + EDA and H(2)O(2). The results initiated further investigations on the influence of other heavy metal ions (Cd(II), Zn(II), Ni(II) and Pb(II)) over urease bound to a NH(2)OH . H(2)SO(4)-modified membrane. It was found that the inhibition effect of the heavy metal ions over immobilized urease decreases in the order: Cu(II) > Cd(II) > Zn(II) > Ni(II) > Pb(II). [Diagram: see text]

Acrylonitrile↗