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At least 667 records · Page 37Linked to original sources
PubMed2003

Detection of ATP-induced nitric oxide in a biomimetic circulatory vessel containing an immobilized endothelium.

Conditions for the adhesion of bovine pulmonary artery endothelial cells (bPAECs) in microbore tubing of 250-microm i.d. are described. When immobilized to the lumen of microbore tubing, these cells represent a mimic of a circulatory vessel's endothelium. The microbore tubing is coated with 100 microg mL(-1) fibronectin in order to promote bPAEC adhesion to the lumen of the tubing. A series of micrographs of the cells inside of the tubing indicates that approximately 3.5 h is necessary for cell adhesion. In this study, adenosine triphosphate (ATP) is used to induce the release of nitric oxide from the endothelium mimic. The endothelium-derived NO is detected amperometrically at a parallel flow cell containing a glassy carbon working electrode modified with Nafion. Results indicate that detectable amounts of NO are only produced by the endothelium mimic when ATP is present in the buffer. The typical concentration of NO produced by the endothelium mimic upon the introduction of 100 microM ATP is approximately 0.80 microM. Based on the injection volume of ATP and the estimated number of cells on the tubing lumen, this value corresponds to approximately 1 amol of NO/cell. Moreover, shear stress alone does not provide the agonistic effect required for NO production in the submicromolar range.

Adenosine Triphosphate↗
PubMed2003

Nonideal electrochemical behavior of biomimetic iron porphyrins: interfacial potential distribution across multilayer films.

The electrochemical behavior of multilayer films formed by iron porphyrins deposited on an edge plane graphite electrode has been examined under anaerobic conditions. In the scan rate interval (1-250 mV/s) where the electrode reaction is reversible, CV diagrams of these films demonstrate substantial deviations from ideality in broadening and separation of the peaks. A model that describes the observed behavior is proposed by taking into account the potential distribution at the electrode/film interface and the concentration dependence of surface activity coefficients. The peak separation is described in terms of the electric double layer that affects the potential difference driving the electrode reaction. The effective potential difference deviates from the applied value due to the potential distribution across the film. The interfacial potential distribution depends on the ionic concentration inside the film. When different ionic concentrations are assumed for oxidation and reduction, different shifts from the applied potential lead to a hysteresis of the peaks. The peak broadening is modeled by using the lattice theory expression for the surface activity coefficients. The model shows that the midpoint potentials of the redox centers depend on the ionic concentration inside the film. At low ionic concentrations, they are remarkably close to the midpoints of the cytochrome c oxidase heme a3/CuB site.

Electrochemistry↗
PubMed2005

Analyzing the mechanisms of selectivity in biomimetic self-assemblies via IR and NMR spectroscopy of prepolymerization solutions and molecular dynamics simulations.

Molecularly imprinted polymers (MIPs) for 2,4-dichlorophenoxyacetic acid were synthesized via a noncovalent approach with 4-vinylpyridine as functional monomer and ethylene glycol dimethacrylate as cross-linker in a methanol/water mixture. Templated polymers synthesized in this self-assembly approach rely on complex formation between the target analyte and functional monomers in porogenic solution prior to radical polymerization. Consequently, the achievable selectivity is governed by the nature and stability of these complexes. The nature of noncovalent interactions responsible for complex formation during imprinting of the template 2,4-dichlorophenoxyacetic acid (2,4-D) with the functional monomer 4-vinylpyridine has been investigated. Fourier transform infrared and 1H NMR spectroscopies provide the fundamental analytical basis for rationalizing the mechanisms of recognition during the imprinting process probing the governing interactions for selective binding site formation at a molecular level. Molecular modeling studies in explicit solvent (chloroform and water) corroborate the importance of hydrogen bonding in aprotic solvents and of hydrophobic interactions in protic media in agreement with the experimental spectroscopic investigations of prepolymerization solutions. Furthermore, chromatographic studies of the synthesized MIPs provided insight on the importance of size, shape, and functionality during selective 2,4-D rebinding processes confirming the results obtained during the prepolymerization studies.

Journal Article↗
PubMed2026

Biomimetic Hydrogels with Nucleus Pulposus-like Viscoelasticity and ECM Peptides for Discogenic Differentiation of Stem Cells.

Intervertebral disc (IVD) degeneration is a leading cause of low back pain (LBP), primarily originating in the nucleus pulposus (NP). Regenerative strategies combining mesenchymal stem cells (MSCs) with biomaterials offer great potential for NP repair by replenishing cells and restoring extracellular matrix (ECM). However, key translational challenges remain, including limited stem cell differentiation, poor cell survival in the harsh degenerative niche, and insufficient biomaterial support. While matrix viscoelasticity has been shown to influence adipose-derived stem cell (ASC) discogenic differentiation, its interplay with cell-adhesive ligands for IVD regeneration remains unclear. Moreover, most current hydrogels fail to replicate the ultrafast stress relaxation properties of native non-degenerative human NP tissue. Here, we developed viscoelastic ECM peptide-functionalized hydrogels (VEPH), specifically designed to mimic healthy human NP biomechanics and promote ASC differentiation for NP regeneration. We biochemically conjugated NP ECM-derived adhesive peptides (IKVAV, hA5G26, CHAD) through maleimide-thiol click chemistry, achieving hydrogels with significantly faster stress relaxation (∼25 s) compared to conventional viscoelastic alginate hydrogels (>100 s). Our results demonstrated that VEPH supported >95% ASC viability and robust metabolic activity over 21 days in 3D culture. Notably, the IKVAV-functionalized hydrogel significantly enhanced ASC cell-matrix interactions, upregulated NP marker expression (KRT18, HIF-1α, ITGA3, and CD24), and promoted type-II collagen secretion, indicating an NP-committed cell fate. Our findings highlight the synergistic roles of matrix viscoelasticity and NP-specific biochemical cues in directing ASC discogenic differentiation and advancing novel biomaterial design for IVD regeneration.

cell-adhesive peptides↗
PubMedDate not supplied

A biomimetic pH-responsive polymer directs endosomal release and intracellular delivery of an endocytosed antibody complex.

Poly(propylacrylic acid) (PPAAc) is a synthetic pH-responsive polymer that has been shown to disrupt cell membranes at low pH values typical of the endosome, but not at physiological pH, suggesting its use as an endosomal-releasing agent [Murthy et al. J. Controlled Release 61, 137-43]. We have constructed an antibody-targeted biotherapeutic model to investigate whether PPAAc can enhance intracellular trafficking of proteins to the cytoplasm. A ternary complex composed of a biotinylated anti-CD3 antibody, streptavidin, and biotinylated PPAAc was fluorescently labeled, and its intracellular fate was analyzed by confocal microscopy, flow cytometry, and quantitative western blotting of cell fractionates. The 64.1 anti-CD3 antibody was previously shown to direct receptor-mediated endocytosis in the Jurkat T-cell lymphoma cell line and was rapidly trafficked from the endosome to the lysosomal compartment. The antibody-streptavidin complex was also rapidly internalized to the endosomal/lysosomal compartment and retained there, as evidenced by punctate regions of fluorescence observed by confocal fluorescence microscopy. In samples containing the ternary complex of antibody, streptavidin, and PPAAc-biotin, diffuse fluorescence in the cytoplasm was observed, indicating that PPAAc enhanced translocation to the cytoplasm. This was confirmed by western blotting analysis of the isolated cytoplasm. Flow cytometry results demonstrated that neither streptavidin nor PPAAc caused nonspecific uptake of the complex, nor did they inhibit antibody-mediated endocytosis. The striking enhancement of protein delivery to the cytoplasm by complexed PPAAc suggests that this polymer could provide a new delivery agent for therapeutic, vaccine, and diagnostics development.

Antibodies, Monoclonal↗
PubMedDate not supplied

Biomimetic poly(methyl methacrylate)-based terpolymers: modulation of bacterial adhesion effect.

Adherence of Staphylococcus aureus, responsible for major foreign body infections, was assessed onto functionalized poly(methyl methacrylate)-based terpolymers bearing sulfonate and carboxylate groups and onto poly(methyl methacrylate) as control. These terpolymers, have been synthesized by radical copolymerization of methyl methacrylate, methacrylic acid, and sodium styrene sulfonate by varying the ratio R = [COO(-)]/[COO(-) + SO(3)(-)] from 0 to 1 and keeping ionic monomer content between 7 and 18%. Adsorption of fibronectin onto poly(methyl methacrylate) was shown to dramatically promote bacterial adherence, whereas a strong inhibition of bacteria adherence was observed onto functionalized terpolymers containing both carboxylate and sulfonate groups. When terpolymers were predominantly functionalized by carboxylate groups, bacteria adherence was favored and reached values close to those obtained for poly(methyl methacrylate). These results have been related to the distribution of the anionic groups along the macromolecular chains, creating active sites responsible for specific interactions with fibronectin and inducing modifications of its conformation. The conformation of the adsorbed adhesive protein was then suggested to have an influence on the availability of its interaction sites to bacteria adhesins and therefore on modulation of bacteria adherence. Inhibition of Staphylococcus aureus adherence by functionalized poly(methyl methacrylate)-based terpolymers is of great interest in the field of biomedical implants and especially in the case of ophthalmic applications.

Bacterial Adhesion↗
PubMedDate not supplied

Biomimetic mineralization of noble metal nanoclusters.

A number of biological systems have developed highly orchestrated detoxification mechanisms toward the bioreduction and mineralization of noble metals. These systems incorporate small peptides and proteins as nucleation sites for metal binding and nanocluster stabilization. Herein, we present the use of biologically relevant ligands ranging from single amino acids (histidine, imidazole, and cysteine) to linear peptides (glutathione and a histidine rich peptide) in the stabilization of a variety of noble metal surfaces (Au(0), Ag(0), Pt(0), and Cu(0)). As a result, the different nanocluster/ligand combinations offered a broad range of sizes and stabilitites. The peptide coat also affords a unique functional handle for the formation of larger assemblies. Using Ni chelation and immunomolecular approaches, strategies for the assembly of nanocluster heterostructures were investigated.

Amino Acids↗
PubMedDate not supplied

Control of nanobiointerfaces generated from well-defined biomimetic polymer brushes for protein and cell manipulations.

To better understand protein/material and cell/material interactions at the submolecular level, well-defined polymer brushes consisting of poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) on silicon wafers were prepared by atom transfer radical polymerization (ATRP). Silicon wafers were treated with 3-(2-bromoisobutyryl)propyl dimethylchlorosilane (BDCS) to form a monolayer that acts as initiators for ATRP. Silicon-supported BDCS monolayers were soaked in a methanol/water mixture solution containing Cu(I)Br, bipyridine, and a sacrificial initiator. After MPC was added to the solution, ATRP was carried out for 18 h. The molecular weight and thickness of the PMPC brush layer on the silicon surface increased with an increase in the polymerization time. The dense polymer brushes were obtained by the "grafting from" system. By selective decomposition of the BDCS monolayer by UV light-irradiation, the PMPC brush region and the sizes were well controlled, resulting in fabricating micropatterns of the PMPC brushes. When the thickness of the PMPC brush layer was greater than 5.5 +/- 1.0 nm (3 h polymerization), serum protein adsorption and fibroblast adhesion were effectively reduced, i.e., proteins and cells could recognize such thin polymer brushes on the surface. In addition, the density of the adherent cells on the patterned PMPC brush surface could be controlled by changing the size of the pattern.

Adsorption↗
PubMed2006

Cobalt ion mediated self-assembly of genetically engineered bacteriophage for biomimetic Co-Pt hybrid material.

Biological scaffolds are used for the synthesis of inorganic materials due to their ability to self-assemble and nucleate crystal formation. We report the self-assembly of engineered M13 bacteriophage as a template for Co-Pt crystals. A M13 phage library with an octapeptide library on the major coat protein (pVIII) was used for selection of binders to cobalt ions. Fibrous structures with directionally ordered M13 phage were obtained by interaction with cobalt ions. Co-Pt alloys were synthesized on the fibrous scaffold, and their magnetic properties were characterized. The mineralization showed organized nanoparticles on fibrous bundles. This approach using the phage pVIII library allows for genetic selection that both induces assembly of the phage and directs mineralization of the selected inorganic material.

Bacteriophage M13↗
PubMedDate not supplied

Biomimetic metal-sorbing vesicles: Cd2+ uptake by phosphatidylcholine vesicles doped with ionophore A23187.

Unilamellar phosphatidylcholine vesicles, harboring the ionophore, A23187, in the bilayer and the water-soluble chelating agent, nitrilotriacetate, in the vesicle interior, rapidly sequester and concentrate Cd2+ from dilute aqueous solution. Metal-sorbing vesicle permeabilities for cadmium ion at 5 ppm (42.8 microM) ranged from 8.09 x 10(-7) to 1.27 x 10(-4) cm/s for surface A23187 concentrations of 0.22-2.27 pmol/cm2 (which correspond to lipid:carrier molar ratios of 2000:1 to 200:1) and pH's from 5.5 to 8.5. The Cd2+ permeability shows linear variation with carrier concentration under the conditions studied. As pH is decreased, an increasing fraction of the A23187 becomes protonated, and the permeability exhibits a positive linear relationship with a function related to that for the fraction of unprotonated carrier. These noncovalently assembled, metal-sorbing vesicles exhibit shelf lives of several months and remain stable throughout typical metal sorption studies.

Adsorption↗
PubMedDate not supplied

Biomimetic peptide surfaces that regulate adhesion, spreading, cytoskeletal organization, and mineralization of the matrix deposited by osteoblast-like cells.

In an effort to regulate mammalian cell behavior in contact with solid material surfaces, we have functionalized surfaces with different ratios of both the putative cell binding (-Arg-Gly-Asp-) domain and a consensus heparan-binding domain. The peptide sequences -Arg-Gly-Asp- (-RGD-) and -Phe-His-Arg-Arg-Ile-Lys-Ala- (-FHRRIKA-) or mixtures of the two in the ratios of 75:25 (mimetic peptide surface I), 25:75 (mimetic peptide surface II), and 50:50 (mimetic peptide surface III) were immobilized on model surfaces using a heterobifunctional cross-linker to link the peptide(s) to amine-functionalized quartz surfaces. Contact angle measurements, spectroscopic ellipsometry, and X-ray photoelectron spectroscopy were used to confirm the chemistry, thickness of the overlayers, and surface density of immobilized peptides ( approximately 4-6 pmol/cm2). The degree of rat calvaria osteoblast-like cell spreading, focal contact formation, cytoskeletal organization, proliferation, and mineralization of the extracellular matrix (ECM) on model biomaterial surfaces was examined. Mimetic peptide surface II (MPS II) and MPS III supported the highest degree of cell spreading (p < 0.05), following 4 h of incubation, compared to MPS I, homogeneous -RGD-, and homogeneous -FHRRIKA- grafted surfaces. Furthermore, MPS I, MPS II, MPS III, and homogeneous -RGD- surfaces promoted the formation of focal contacts and stress fibers by attached bone cells. The strength of bone cell detachment following 30 min of incubation was significantly higher (p < 0.05) on MPS II surfaces compared to homogeneous -RGD- and -FHRRIKA-. However, the degree of cell proliferation on the peptide surfaces were not significantly different from each other (p > 0.1). Following 24 d in culture, the areas of mineralized ECM formed on MPS II and MPS III surfaces were significantly (p < 0.05) larger than those of other surfaces. These results demonstrate that utilizing peptide sequences incorporating both cell- and heparin-adhesive motifs can enhance the degree of cell surface interactions and influence the long-term formation of mineralized ECM in vitro.

Amino Acid Sequence↗
PubMed2001

Biomimetic extraction of PAHs and PCBs from soil with octadecyl-modified silica disks to predict their availability to earthworms.

We developed a model to predict the availability of PAHs and PCBs to earthworms (Lumbricus terrestris L.) in soils. We related the uptake of PAHs and PCBs by earthworms to the extraction with octadecyl-modified silica disks (C18 disks). Eleven soils (data set A) were used to develop the model, and 14 additional soils (data set B) were used to validate it independently. The biota-to-soil accumulation factors (BSAFs) of higher molecular weight PAHs (> or =202 g mol(-1)) and PCBs were higher than the corresponding Cl8 disk-soil partition coefficients (Kdisk) in the soils of data set A. This suggested that PAHs and PCBs were not only partitioned between soil and earthworms but also selectively ingested or metabolized. Nevertheless, we could predict the BSAFs of individual PAHs and PCBs for data set A by regression equations of log BSAF on log Kdisk (r=0.47-0.87). To predict the BSAFs of all PAHs and PCBs, respectively, we derived a model for each compound class that uses Kdisk and K(ow) values. Both the compound and the compound-class specific model were suitable to predict the BSAFs of PAHs and PCBs in data set B within a factor of 10-15.

Animals↗
PubMed2003

Effects of humic substances on the pattern of oxidation products of pentachlorophenol induced by a biomimetic catalytic system using tetra(p-sulfophenyl)porphineiron(III) and KHSO5.

In the presence of humic substances (HSs), the oxidative conversion of pentachlorophenol (PCP) was found to be efficiently catalyzed by tetra(p-sulfophenyl)porphineiron(III) (Fe(III)-TPPS) using KHSO5 as an oxygen donor. Ortho-tetrachloroquinone (o-TeCQ), 2-hydroxyl-nonachlorodiphenyl ether (2H-NCDE), 4-hydroxyl-nonachlorodiphenyl ether (4H-NCDE), and octachlorodibenzo-p-dioxin (OCDD) were identified as the major byproducts of the reaction. Decreased amounts of these byproducts were produced in the presence of HS. In particular, the addition of HSs with a lower degree of humification resulted in a large decrease in the formation of dimers, such as 2H-NCDE, 4H-NCDE, and OCDD. More than 60% of the chlorine, which was released from PCP, was found in the HS fractions after the reaction. This suggests that chlorinated intermediates from PCP were incorporated into the HS. Pyrolysis-GC/MS and 13C NMR studies confirmed that the binding of the chlorinated intermediates was covalent in nature and that the intermediates were copolymerized with HS via oxidative coupling reactions. A Microtox test demonstrated that the toxicity of the HS fraction containing PCP-derived intermediates was much lower than that of the mixture of PCP and HS in the absence of a catalytic reaction.

Catalysis↗