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At least 865 records · Page 48Linked to original sources

PubMed1989

Biotinylation of reactive amino groups in native recombinant human interleukin-1 beta.

Recombinant human interleukin-1 beta (rIL-1 beta) was chemically modified by a 10-fold molar excess (reagent:protein) of sulfosuccinimidyl 6-(biotinamido) hexanoate (sulfo-NHS-LC-biotin) or sulfosuccinimidobiotin (sulfo-NHS-biotin) under mild conditions. The primary product was purified in each case by cation exchange high performance liquid chromatography (HPLC) and digested with endoproteinase Lys C. Peptide mapping by C18 reverse phase HPLC permitted identification of three sites of biotinylation using both reagents; N-terminal alanine, lysine 93, and lysine 94. Few additional singly modified rIL-1 beta products were obtained under these conditions, despite the presence of 15 lysine residues in this protein. These data support the view that the N terminus as well as the trilysine sequence (residues 92-94) are readily susceptible to chemical modification and are exposed on the surface of the protein. Chromatography of intact biotinylated rIL-1 beta by C4 reverse phase HPLC resolved a protein modified exclusively at the N-terminal alanine from two proteins modified singly at either lysine 93 or lysine 94. In addition, a protein product modified at lysine 103 was also obtained when rIL-1 beta was similarly modified with sulfo-NHS-biotin. Since the only difference between the two biotinylation reagents relates to spacer length and its associated hydrophobicity, these data suggest that lysine 103 is not as accessible to surface modification reagents as are lysine 93, lysine 94, or alanine 1. Initial experiments indicate that none of the modifications described above decrease thymocyte proliferation by more than one order of magnitude. Therefore, these amino acid residues are not crucial for bioactivity, and we anticipate the use of these monobiotinylated proteins in structure/function analysis of IL-1 beta.

Amino Acid Sequence↗

PubMed2006

Mimicking cell-cell interactions at the biomaterial-cell interface for control of stem cell differentiation.

The ability to regulate stem cell proliferation and differentiation has relevance in numerous medical applications, including medical devices, tissue engineering, and regenerative medicine. To control cellular behavior at the biomaterial or scaffold interface, many studies have employed surface modifications that mimic the extracellular matrix. Strikingly absent is the immobilization of cell-surface ligands to the biomaterial surface. One cell-to-cell signaling pathway that has been shown to regulate tissue development and stem cell fate is the Notch pathway. Recently, the Notch signaling pathway was identified as a key regulator of epithelial differentiation. Utilizing this knowledge, we applied an affinity immobilization scheme designed to attach and orient the Notch ligand, Jagged-1, in an active conformation on a biomaterial surface. When epithelial stem cells were plated on the bound ligand, the Notch/CBF-1 signaling pathway was stimulated and the cells upregulated both intermediate- and late-stage differentiation markers. In addition, the ligand promoted tight clustering and extensive stratification. Soluble Jagged-1 showed no Notch/CBF-1 signaling and very little, if any, cell differentiating activity. The high potency of bound Jagged-1 suggests that modification of a surface with a Notch ligand presents a powerful method to control stem cell differentiation at the cell-biomaterial interface.

Animals↗

PubMed2006

Enhanced osteogenic promotion around dental implants with synthetic binding motif mimicking bone morphogenetic protein (BMP)-2.

Synthetic receptor binding motif mimicking bone morphogenetic protein-2 (BMP-2) was covalently linked to titanium (Ti) surfaces through a chemical conjugation process. The composition and properties of surface-modified Ti were investigated by XPS as well as by measuring surface radioactivity. In vitro tests were conducted with osteoblast-like MC3T3-E1 cells to assess cell attachment, morphology, and expression of osteogenic marker in the cells grown on modified Ti surfaces. In addition, in vivo experiments involved implants in mandibular bone defects of beagles to evaluate the effect of surface modification on bone regeneration. Results of XPS measurements showed a complete and homogeneous peptide overlayer on the Ti surfaces; the content was further measured by gamma counting. Biological evaluations showed that the biochemically modified Ti samples were active in terms of cell attachment behavior. The MC3T3-E1 cell growth rate, marker protein expression, and alkaline phosphatase production of the peptide-modified surfaces were all higher than those of control Ti. Importantly, the implants in the canine mandibles showed significant increase of bone growth when modified with bioactive peptide, thereby confirming that biochemical modifications of Ti surfaces can enhance the rate of bone healing as compared with untreated Ti surfaces.

Amino Acid Motifs↗

PubMed2006

Antibacterial activity of zinc modified titanium oxide surface.

Titanium-based implants are successfully used for various biomedical applications. However, in some cases, e.g. in dental implants, failures due to bacterial colonization are reported. Surface modification is a commonly proposed strategy to prevent infections. In this work, titanium oxide, naturally occurring on the surface of titanium, was modified by promoting the formation of a mixed titanium and zinc oxide, on the basis of the idea that zinc oxide on titanium surface may act as the zinc oxide used in pharmaceutical formulation for its lenitive and antibacterial effects. The present work shows that it is possible to form a mixed titanium and zinc oxide on titanium surfaces, as shown by Scanning Electron Microscopy and XPS analysis. To this end titanium was preactivated by UV on crystalline titanium oxide, both in the anatase form or in the co-presence of anatase and rutile. By performing antibacterial assays, we provide evidence of a significant reduction in the viability of five streptococcal oral strains on titanium oxide surfaces modified with zinc. In conclusion, this type of chemical modification of titanium oxide surfaces with zinc might be considered a new way to reduce the risk of bacterial colonization, increasing the lifetime of dental system applications.

Anti-Bacterial Agents↗

PubMed1996

Use of p-nitrophenyl chloroformate chemistry to immobilize protein on orthopedic biomaterials.

Biochemical surface modification involves covalently immobilizing biomolecules onto biomaterial surfaces to induce specific biological responses. This approach may be useful for enhancing the fixation of orthopedic implants. p-Nitrophenyl chloroformate (p-NPC) was used to immobilize protein on bulk samples of Co-Cr-Mo and Ti-6Al-4V. Activation of both materials was dependent on the concentration of p-NPC, with a maximum of approximately 1.5 active groups/nm2 of nominal surface area. Trypsin was used as a model protein because much is known about its structure and mode of action. Derivatization with 0.65 mg p-NPC/cm2 resulted in significantly greater enzymatic activity (7.4 BAEE [N-(alpha)-benzoyl-L-arginine ethyl ester hydrochloride] units) on the Co-Cr-Mo samples compared with higher concentrations of p-NPC (5 BAEE units) and with simple adsorption of trypsin (1.5 BAEE units). An activity of 10.5 BAEE units was measured on both adsorbed and p-NPC-activated Ti-6Al-4V, with the exception of samples derivatized with 1.95 mg p-NPC/cm2, on which activity was significantly lower (4 BAEE units). In probing the linkages between trypsin and biomaterial by treatment with chaotropic agents, guanidine hydrochloride (GuHCl) was observed to eliminate more enzymatic activity than was urea. On Co-Cr-Mo samples, GuHCl removed nearly all the trypsin activity, while urea significantly decreased the activity only at a concentration of 0.65 mg p-NPC/cm2. Treatment of Ti-6Al-4V samples with GuHCl caused a trend of decreasing activity with increasing concentration of p-NPC, whereas urea had no effect on immobilized trypsin activity.

Adsorption↗

PubMed2006

Osteoblast-like cell attachment to and calcification of novel phosphonate-containing polymeric substrates.

In an attempt to interact natural bone and bone cells with biomaterials and to begin to develop modular tissue engineering scaffolds, substrates containing phosphonate groups were identified to mimic mineral-protein and natural polymer-protein interactions. In this study, we investigated poly(vinyl phosphonic acid) copolymer integration with existing materials as a graft-copolymer surface modification. Phosphonate-containing copolymer-modified surfaces were created and shown to have varying phosphate content within different polymeric surfaces. As the phosphonate content in the monomer feed approached 30% vinyl phosphonic acid, increased osteoblast-like cell adhesion (3- to 8-fold increase in adhesion) and proliferation (2- to 10-fold increase in proliferation rate) was observed. Since surfaces modified with 30% vinyl phosphonic acid in the feed exhibited a maximal cell adhesion and proliferation (9.4 x 10(4) cells/cm(2)/day), it was hypothesized that this copolymer composition was optimal for protein-polymer interactions. Osteoblast-like cells formed confluent layers and were able to differentiate on all surfaces that contained vinyl phosphonic acid. Most importantly, cells interacting with these surfaces were able to significantly mineralize the surface. These results suggest that phosphonate-containing polymers can be used to integrate biomaterials with natural bone and could be used for tissue engineering applications.

3T3 Cells↗

PubMed1990

Modulation of bacterial binding to salivary pellicle by treatment with hydrophilizing compounds.

Two hydrophilizing agents, a branched polyethylene glycol derivative and a non-ionic cellulose ether (EHEC) bind to buffer-treated hydroxyapatite and prevent attachment of Streptococcus mutans. EHEC gives a more efficient surface modification, presumably due to a more complete surface coverage. Neither of the 2 hydrophilizing agents were effective on hydroxyapatite which had been pre-treated with saliva. In a small clinical trial, EHEC was found to be moderately effective in preventing plaque formation.

Adhesiveness↗

PubMed1991

Modern metal processing for improved load-bearing surgical implants.

A review of modern methods for preparing metallic alloys that could be useful for the fabrication of load-bearing metallic biomaterials is presented. The use of rapid solidification processing and surface modification of metals by ion implantation or surface coatings and variations thereof is used currently for the formation of novel metallic alloys in other high-tech fields, notably the optoelectronics industry. Further studies to explore potential benefits for surgical implant fabrication through the application of these technologies is recommended.

Alloys↗

PubMed1995

Surface characterization and ex vivo blood compatibility study of plasma-modified small diameter tubing: effect of sulphur dioxide and hexamethyldisiloxane plasmas.

The development of a small diameter artificial vascular graft or prosthesis is limited by rapid thrombus formation and subsequent embolization upon blood contact. Plasma surface modification was employed to modify the inner surface of small diameter low density polyethylene (LDPE) tubing without varying the outer surface chemistry and physical properties of the tubing. A sulphur dioxide (SO2) plasma was used to form sulphonate functionality on the surface. In addition, a hexamethyldisiloxane (HMDSO) plasma and different gas flow ratios of SO2-HMDSO gas mixture plasmas were used to form ultrathin polysiloxane-like coatings inside the LDPE tubing. X-ray photoelectron spectroscopy (XPS) indicated that the inner surface of the tubing can be modified uniformly with this treatment. In addition, XPS results showed that the percentage of sulphur atoms bound to two or three oxygen atoms (sulphone or sulphonate) increased with the SO2-HMDSO mass flow rate ratio. The blood compatibility of the plasma-modified model materials was evaluated using an ex vivo canine arteriovenous shunt model. Similar thrombogenicity was observed comparing the untreated control and the surfaces modified by HMDSO plasma and SO2-HMDSO gas mixture plasmas, despite the differences in surface chemistry. The SO2 plasma-modified surface, which is the most hydrophilic as measured by the captive bubble contact angle measurement technique, was more thrombogenic than the untreated control. This may be attributed to the combined effect of the surface chemistry and surface hydrophilicity.

Animals↗

PubMed1992

Liposome encapsulated hemoglobin: long-term storage stability and in vivo characterization.

Liposome Encapsulated Hemoglobin (LEH) has been the focus of research and development at the Naval Research Laboratory in an effort to find a viable oxygen-carrying resuscitative fluid. Previous reports from our laboratory have shown that LEH binds and releases oxygen in a manner similar to red blood cells, and that it can sustain life when red cell hematocrits are decreased to critical levels. We have also reported on LEH with regards to preparative methods, scale-up feasibility, toxicity, hemodynamics, hemoglobin P50 modification by coencapsulation of organic phosphates, liposomal surface modification, and storage strategies. In this report, the issue of LEH efficacy following long-term storage in the dry state will be addressed. We have shown that hemoglobin, liposomes, and LEH may be successfully lyophilized and rehydrated to viable states. The modification of the LEH formulation by addition of the carbohydrate trehalose results in the successful lyophilization and storage of LEH. In vitro characterization of LEH stored in the dry state for up to six months includes measurement of oxygen-carrying capacity, liposome size retention, methemoglobin production, and the intraliposomal hemoglobin concentration. The in vivo studies report on physiological parameters such as circulation persistence, blood chemistry, and pathological examination in mice.

Animals↗

PubMed1999

[The effect of surface structure on the photoluminescence of SnO2 nanoparticles in hydrosols and organosols].

In this paper, we report the optical properties of SnO2 semiconductor nanoparticles in hydrosols and those of SnO2 semiconductor nanoparticles in organosols in which the surfaces of the particles are coated by a layer of organic surfactant molecules. The photoluminescence spectra of SnO2 semiconductor nanoparticles in the hydrosols and organosols in different conditions were measured and discussed. We conclude that the surface structure of the SnO2 semiconductor nanoparticles affects their optical properties strongly. The oxygen deficiencies on the surface of SnO2 semiconductor nanoparticles play an important role in the optical properties. The surface modification of the particles effectively removes the surface defects of the particles and enhances the intensity of luminescence.

English Abstract↗

PubMed2003

Bacterial biofilms and implantable prosthetic devices.

Erectile dysfunction afflicts millions of men. A group of patients with advanced degeneration of their erectile tissue do not respond to pharmacological therapy, and surgical prosthetic reconstruction represents an attractive and highly satisfying alternative. Yet many men are unwilling to take this step due to fear of infection. Implanted prosthetic devices are at risk for infection because they provide a platform for the development of a bacterial biofilm, an organized bacterial colony that grows on the surface of the implanted material. The biofilm is resistant to all efforts to eradicate it short of removal of the foreign material. Bacteria may attach to the surface of the foreign material by surface charge attraction, hydrophilic/hydrophobic interactions, and by specific attachment by fimbrae. Growth, colonization, and maturation follow bacterial attachment. A mature biofilm is composed of three layers: a linking film binding the biofilm to the surface; a base film made up of a compact layer of bacteria; and a surface film from which free-floating bacteria can arise and spread. The majority of the surface layer is made up of exopolysaccharide matrix. Bacteria deep within the biofilm matrix live in a protected environment; diffusion of antibiotics is difficult, low oxygen tension leads to a lower bacterial metabolic rate rendering the bacteria functionally resistant to high levels of antibiotics. Effective strategies to reduce prosthetic infection levels must rely on the prevention of biofilm formation through surface modification. Possible mechanisms include the addition of antimicrobials to the surface of the device, or chemical modifications, which reduces bacterial attachment.

Biofilms↗

PubMed2005

Formation of tetra(ethylene oxide) terminated Si-C linked monolayers and their derivatization with glycine: an example of a generic strategy for the immobilization of biomolecules on silicon.

Surface modification with oligo(ethylene oxide) functionalized monolayers terminated with reactive headgroups constitutes a powerful strategy to provide specific coupling of biomolecules with simultaneous protection from nonspecific adsorption on surfaces for the preparation of biorecognition interfaces. To date, oligo(ethylene oxide) functionalized monolayer-forming molecules which can be activated for attachment of biomolecules but which can selectively form monolayers onto hydrogen terminated silicon have yet to be developed. Here, self-assembled monolayers (SAMs) containing tetra(ethylene oxide) moieties protected with tert-butyl dimethylsilyl groups were formed by thermal hydrosilylation of alkenes with single-crystal Si(111)-H. The protection group was used to avoid side reactions with the hydride terminated silicon surface. Monolayer formation was carried out using solutions of the alkene in the high-boiling-point solvent 1,3,5-triethylbenzene. The protecting group was removed under very mild acidic conditions to yield a free hydroxyl functionality, a convenient surface moiety for coupling of biological entities via carbamate bond formation. The chemical composition and structure of the monolayers before and after deprotection were characterized by X-ray photoelectron spectroscopy (XPS) and X-ray reflectometry. To demonstrate the utility of this surface for covalent modification, two reagents were compared and contrasted for their ability to activate the surface hydroxyl groups for coupling of free amines, carbonyl diimidazole (CDI), and disuccinimidyl carbonate (DSC). Analysis of XP spectra before and after activation by CDI or DSC, and after subsequent reaction with glycine, provided quantitative information on the extent of activation and overall coupling efficiencies. CDI activated surfaces gave poor coupling yields under various conditions, whereas DSC mediated activation followed by aminolysis at neutral pH was found to be an efficient method for the immobilization of amines on tetra(ethylene oxide) modified surfaces.

Amines↗

PubMed2006

Ultrasensitive detection and characterization of posttranslational modifications using surface-enhanced Raman spectroscopy.

Posttranslational modification (PTM) of proteins is likely to be the most common mechanism of altering the expression of genetic information. It is essential to characterize PTMs to establish a complete understanding of the activities of proteins. Here, we present a sensitive detection method using surface-enhanced Raman spectroscopy (SERS) that can detect PTMs from as little as zeptomoles of peptide. We demonstrate, using model peptides, the ability of SERS to detect a variety of protein modifications, such as acetylation, trimethylation, phosphorylation, and ubiquitination. In addition, we show the capability to obtain positional information for modifications such as trimethylation and phosphorylation using SERS and wavelet decomposition data analysis techniques. We further show that it is possible to apply SERS to detect PTMs from biological samples such as histones. We envision that this detection method might be a valuable technique that is complementary to mass spectrometry in obtaining orthogonal chemical and modification-specific information from biological samples at sensitive levels.

Acetylation↗

PubMed2003

Self-assembled monolayers of novel surface-bound dendrons: peripheral structure determines surface organization.

The synthetic and functional versatility of dendrimers and their well-defined shapes make them attractive molecules for surface modification. We synthesized six structurally very similar surface-bound dendrons and used them as building blocks for the preparation of self-assembled monolayers (SAMs) on a gold surface. We studied the effects of the surface-bound dendron's main structure, peripheral substituents, and the coadsorption process on its self-assembling behavior. Using scanning tunneling microscopy (STM), we observed nanostripes for SAMs of the surface-bound dendron consisting of symmetrical benzene rings. When we changed the symmetrical dendron's structure slightly, by increasing or decreasing the numbers of benzene rings at one wedge, we found no ordered structures were formed by the asymmetrical dendrons. We also introduced two kinds of substituents, heptane chains and oligo(ethylene oxide) chains, to the symmetrical dendron's periphery. Heptane chains appear to enhance the interaction between symmetrical backbones, leading to the formation of stripes, while oligo(ethylene oxide) chains appear to weaken the interaction between symmetrical backbones, resulting in a homogeneous structure. Dendrons with both heptane and oligo(ethylene oxide) chains exhibit nanophase separation in a confined state, leading to the formation of a honeycomb structure. Electrochemical studies provide additional evidence for understanding the resulting surface organizations: surface-bound dendrons with symmetrical structures form denser monolayers than their asymmetrical analogues; SAMs comprising peripherally substituted dendrons exhibit blocking effects proportionate to their hydrophilic fraction.

Journal Article↗

PubMed2004

Stable microstructured network for protein patterning on a plastic microfluidic channel: strategy and characterization of on-chip enzyme microreactors.

Chemical modification of a poly(methyl methacrylate) (PMMA) microchannel surface has been explored to functionalize microfluidic chip systems. A craft copolymer was designed and synthesized to introduce the silane functional groups onto the plastic surface first. Furthermore, it has been found that, through a silicon-oxygen-silicon bridge that formed by tethering to these functional groups, a stable patterning network of gel matrix could be achieved. Thus, anchorage of proteins could be realized onto the hydrophobic PMMA microchannels with bioactivity preserved as far as possible. The protein homogeneous patterning in a microfluidic channel has been demonstrated by performing microchip capillary electrophoresis with laser-induced fluorescence detection and confocal fluorescence microscopy. To investigate the bioactivity of enzymes entrapped within stable silica gel-derived microchannels, the suggested scheme was employed to the construction of immobilized enzyme microreactor-on-a-chip. The proteolytic activity of immobilized trypsin has been demonstrated with the digestion of cytochrome c and bovine serum albumin at a fast flow rate of 4.0 microL/min, which affords the short residence time less than 5 s. The digestion products were characterized using MALDI-TOF MS with sequence coverage of 75 and 31% observed, respectively. This research exhibited a simple but effective strategy of plastic microchip surface modification for protein immobilization in biological and proteomic research.

Amino Acid Sequence↗

PubMedDate not supplied

Hydroxyapatite surface modified by L-lactic acid and its subsequent grafting polymerization of L-lactide.

A new method of surface modification of hydroxyapatite nanoparticles (n-HA) by surface grafting reaction of l-lactic acid and ring-opening polymerization of l-lactide (LLA) was developed. Two modified HA nanoparticles were obtained: HA modified by l-lactic acid (l-HA) and HA grafting with poly(l-lactide) (PLLA; p-HA). The modified surface of n-HA was attested by Fourier transformation infrared, (31)P MAS NMR, and thermal gravimetric analysis. The results showed that l-lactic acid could be easily grafted onto the n-HA surface by forming a Ca carboxylate bond and initiated by the hydroxyl group of the grafted l-lactic acid and LLA could be graft-polymerized onto the n-HA surface in the presence of stannous octanoate. The highest grafting amounts of l-lactic acid and PLLA were about 33 and 22 wt %, respectively. The modified HA/PLLA composites showed good mechanical properties and uniform microstructure. The tensile strength and modulus of the p-HA/PLLA composite containing 15 wt % of p-HA were 67 MPa and 2.1 GPa, respectively, while those of the n-HA/PLLA composites were 45 MPa and 1.7 GPa, respectively. The elongation at the break of the l-HA/PLLA composite containing 15 wt % l-HA could reach 44%, in comparison with 6.5% of the n-HA/PLLA composites containing 15 wt % n-HA.

Durapatite↗

PubMed2007

Synthesis of temperature-responsive heterobifunctional block copolymers of poly(ethylene glycol) and poly(N-isopropylacrylamide).

Heterobifunctional block copolymers of poly(ethylene glycol) (PEG) and poly(N-isopropylacrylamide) (PNIPAM) were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization of NIPAM using a macromolecular trithiocarbonate PEG-based chain transfer agent. The polymerization showed all the expected features of living radical polymerization and allowed the synthesis of copolymers with different lengths of the PNIPAM block. The synthesized block copolymers contained a carboxylic acid group from L-lysine at the focal point and a trithiocarbonate group at the terminus of the PNIPAM block. The trithiocarbonate functionality was converted into a thiol group and used for conjugation of biotin to the end of the PNIPAM block. The copolymers exhibited temperature-dependent association behavior in aqueous solution with a phase transition of approximately 32 degrees C. The described heterobifunctional block copolymers show promise for surface modifications with the potential for stimulus-controlled surface presentation of ligands attached to the terminus of the PNIPAM block.

Acrylic Resins↗