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At least 793 records · Page 44Linked to original sources
PubMed1989

Biomimetic chemistry of hemeproteins.

Hemeproteins play important physiological roles for an oxygen metabolism in living organisms. Their functions are divided to three main groups, i) hemoglobins, myoglobins and the cytochromes which function by transporting and storing dioxygen and electrons; ii) catalase and peroxidases which are activated by hydrogen peroxide, iii) cytochrome oxidase and cytochrome P450 both of which bind dioxygen and use the dioxygen as an electron sink or by partially reducting the dioxygen to make a powerful oxidizing agent. The hemeproteins included to group ii) have been established to produce a reaction intermediate, oxo-ferry (Fe(IV] pi-cation radical, during the catalytic cycle. Recent model studies to mimic cytochrome P450 catalyzed-reaction have shown that the intermediate retains an activated oxygen and functions as a powerful oxidizing agent in the monoxygenase reaction. In this article, the properties of the intermediate and the role in cytochrome P450 monoxygenase reaction is summarized.

Chemical Phenomena↗
PubMedDate not supplied

Biomimetic surfaces: how man-made becomes man-like.

Biomaterials are usually synthetic or man-made substances that possess one or more properties that are suitable for use in devices that come into contact with living tissues. Living tissues are most content to be in contact with other tissues, especially those of their own kind. Biomimicry takes this observation and turns it into a practical solution to some problems of biocompatibility. It involves transforming traditional materials into tissue-like materials so that they may then be able to convince their host that it is in contact with one of its kind.

Biocompatible Materials↗
PubMed1999

Carbohydrate Recognition through Noncovalent Interactions: A Challenge for Biomimetic and Supramolecular Chemistry.

Carbohydrates are not always as "sticky" as one might expect. Even in organic solvents they are difficult targets for the supramolecular chemist, due to their complex, three-dimensional structures. In their natural environment (water) they are especially elusive, presenting challenges which will occupy synthetic and theoretical chemists for some time to come. The complex of an octaamide supramolecular receptor with beta-D-glucopyranose, which binds through apolar and polar contacts, is shown.

Journal Article↗
PubMed2000

Affinity chromatography on immobilized "biomimetic" ligands. Synthesis, immobilization and chromatographic assessment of an immunoglobulin G-binding ligand.

A synthetic bifunctional ligand (22/8) comprising a triazine scaffold substituted with 3-aminophenol (22) and 4-amino-1-naphthol (8) has been designed, synthesised, characterised and immobilized on agarose beads to create a robust, highly selective affinity adsorbent for human immunoglobulin G (IgG). Scatchard analysis of the binding isotherm for IgG on immobilized 22/8 (90 micromol 22/8/g moist weight gel) indicated an affinity constant (Ka) of 1.4 x 10(5) M(-1) and a theoretical maximum capacity of 151.9 mg IgG/g moist weight gel. The adsorbent shows similar selectivity to immobilized protein A and binds IgG from a number of species. An apparent capacity of 51.9 mg human IgG/g moist weight gel was observed under the experimental conditions selected for adsorption. Human IgG was eluted with glycine-HCl buffer with a recovery of 67-69% and a purity of 97.3-99.2%, depending on the pH value of the buffer used for elution. Preparative chromatography of IgG from human plasma showed that under the specified conditions, 94.4% of plasma IgG was adsorbed and 60% subsequently eluted with a purity of 92.5%. The immobilized ligand was able to withstand incubation in 1 M NaOH for 7 days without loss of binding capacity for IgG.

Animals↗
PubMed2001

Replacing and renewing: synthetic materials, biomimetics, and tissue engineering in implant dentistry.

Hundreds of thousands of implantations are performed each year in dental clinical practice. Dental implants are a small fraction of the total number of synthetic materials implanted into the human body in all fields of medicine. Basically, these millions of implants going into humans function adequately. But longevity and complications still are significant issues and provide opportunities for the creation of improved devices. This manuscript briefly reviews the history of dental implant devices and the concepts surrounding the word "biocompatibility." It then contrasts the foreign body reaction with normal healing. Finally, the article describes how ideas gleaned from the study of normal wound healing can be applied to improved dental implants. In a concluding section, three scenarios for dental implants twenty years from now are envisioned.

Bacterial Adhesion↗
PubMed2002

Biomimetic actuators in prosthetic and rehabilitation applications.

Where humans and mechanical systems operate in close proximity there is a need to provide drive systems that combine the positive attributes of conventional actuator design with a 'softer' safer interaction capacity. This is achieved by natural muscle, and engineering emulation of this functionality could have a significant benefits in many areas, but particularly the medical domain. This work will study the use of compliance regulated and controlled pairs of antagonistic pneumatic Muscle Actuators (pMAs) in two medical scenarios; i) The construction of dexterous prosthetic hands having a high power and low mass potential, ii) The construction of a power assist device that can be used to augment the strength of those suffering from degenerative muscle wasting diseases.

Amputation, Surgical↗
PubMed2003

[Metalloporphyrin catalyzed biomimetic oxidation potentials: potential uses and applications].

Oxidative processes catalysed by metalloporphyrins nowadays are gaining importance in the study of various biological systems. One of the main direction of the investigations with synthetic metalloporphyrin catalysts is the development of systems which are capable of reproducing oxidative processes mediated by hem proteins (such as cytochrome P450, lignin peroxidase, nitric oxide synthesize (NOS), etc.). Another possible application is to develop systems containing metalloporphyrin catalyst, which could selectively oxidize organic compounds or detoxicate polluting agents at industrial level. We proved the benefits of the application of pentafluoride iron porphyrin used in three fields:--in the insect selective cytochrome P450 catalysed metabolism of carbamate insecticides [1],--to verify the natural decomposition path of insect selective cytochrome P450 inhibitors (metabolic pathways of lignin peroxidase) [2],--in modelling the H2O2 dependent NOS catalysed oxidation of the N-hydroxyguanidine based NO donors [3].

Catalysis↗
PubMedDate not supplied

Model systems for metabolism studies. Biomimetic oxidation of acetaminophen and ellipticine derivatives with water-soluble metalloporphyrins associated to potassium monopersulfate.

Some original water-soluble metalloporphyrins/KHSO5 systems were developed to mimic the metabolic biooxidation of drugs. Oxidation of acetaminophen and various ellipticine derivatives were used as model reactions. Oxidative products (mainly quinone-imine structures) were obtained in good yield after 2 min of reaction, for a catalyst/substrate ratio of 0.04. Iron(III) derivative of tetrasodium meso-tetrakis(p-sulfonatophenyl)porphyrin and manganese(III) derivative of tetraacetate meso-tetrakis(4-N-methyl-pyridiniumyl)-porphyrin were the best catalysts for the oxidation of acetaminophen and ellipticine compounds, respectively. At low catalyst concentration, initial turnover rates could rise up to 8 catalytic cycles/sec. In some conditions, these catalytic systems are nearly as efficient as horseradish peroxidase/H2O2. They might have a real future as oxidation catalysts, in complement to the use of purified monooxygenase and peroxidases, to predict the possible in vivo oxidative metabolite pathways.

Acetaminophen↗
PubMed2006

[Comparison between biomimetic sampling technique using semipermeable membrane device and bioconcentration in caged fish for polycyclic aromatic hydrocarbons].

Semipermeable membrane device (SPMD) was recently accepted to estimate the time-integrated concentrations of bioavailable hydrophobic organic compounds (HOCs) in a similar manner as lipophilic bioconcentration. However few field researches were carried out to verify the similarities of SPMD and fish in concentrating HOCs from water. In present work, SPMD and caged crucian carps (Carassius auratus) were deployed side-by-side at five sites in Meiliang Bay, Taihu Lake for 32 days and concentrations of polycyclic aromatic hydrocarbons (PAHs) in SPMD and fish were analyzed. The results showed that the composition of PAHs and relative concentration of individual PAH in SPMD and fish were quite similar. There was significant correlation between bioconcentration factors (lg BCF) and device concentration factors (lg DCF) for concentrations of PAHs (p < 0.0001). However in a quantitative analysis, lipid-normalized concentrations of PAHs in SPMD and fish were similar, and the ratios of the concentrations of PAHs in fish and SPMD were ranged from 0.47 to 4.12. In summary, SPMD could be the surrogate to estimate PAHs levels in fish in fresh water lake.

Animals↗
PubMed2006

[The experimental study of biomimetic artificial cartilage fabrication in vitro and ectopic chondrogenesis in vivo].

Tri-dimensional poly (DL-lactic-co-glycolic acid) (PLGA) scaffolds were fabricated using a rapid prototyping (RP) technique and the gene of human bone morphogenetic protein 2 (hBMP-2) was transferred into rabbit bone marrow stromal cells (MSCs) via recombinant adeno-associated virus vectors (rAAV-hBMP-2). Thirty-two PLGA scaffolds, size (4 mm X 4 mm X 4 mm), were coated with collagen type I and equally divided into 2 groups. In group A, each scaffold was loaded with 2 X 10(4) hBMP-2 (+) MSCs to establish a hBMP-2 (+) MSCs/PLGA composite. In group B, each scaffold was loaded with 2 X 10(4) hBMP-2 (-) MSCs to establish a hBMP-2 (-) MSCs/PLGA composite. The composites in both groups were cultured for subcutaneous implantation in nude mice. All animals were killed 30 days after implantation and the differentiation of composites was evaluated. As a result, MSCs infected with rAAV-hBMP-2 efficiently expressed hBMP-2 protein. RP-based PLGA scaffolds had ideal microarchitecture. The diameters of macropore and micropore of the scaffolds were 300 microm and 3-5 microm, respectively. At 3-5 days after culture, a number of seeding cells well grew on the scaffolds of both groups. The composites in group A had chondrogenesis ability in vivo and the expression of collagen type II was positive. In group B, however, only polymers and fiber tissues were predominantly found. The percentage of polymer remnant area was significantly lower in group A than in group B (P<0.01). Our results therefore indicate that RP-based PLGA scaffolds efficiently coated with collagen type I have good biocompatibility with hBMP-2 (+) MSCs and the techniques developed in this study may favor cartilage tissue engineering.

Animals↗
PubMed1984

Biomimetic preparation and structure determination of QGI, one of the quinoline-DNA base adducts formed in cells treated with 4-nitroquinoline 1-oxide.

One of the quinoline-DNA base adducts, QGI, formed in cells treated with 4-nitroquinoline 1-oxide, was readily prepared in vitro from GMP or dGMP and 4-hydroxy-aminoquinoline 1-oxide in the presence of ATP, L-serine, and seryl tRNA synthetase. Synthetic seryl-AMP could be substituted for the enzymatic activation system for QGI formation. Chemical and spectral analyses of the adduct thus prepared revealed that QGI can be formulated as N4-(guan-8-yl)-4-aminoquinoline 1-oxide, the structure of which is identical with the modified base structure involved in the deoxyguanosine-quinoline adduct, dGIII (nomenclature of Loucheux-Lefebvre et al.) obtained by the chemical modification of deoxyguanosine with monoacetyl and diacetyl derivatives of 4HAQO.

4-Hydroxyaminoquinoline-1-oxide↗