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PubMed2000

Morphogenesis and tissue engineering of bone and cartilage: inductive signals, stem cells, and biomimetic biomaterials.

Morphogenesis is the developmental cascade of pattern formation, body plan establishment, and the architecture of mirror-image bilateral symmetry of many structures and asymmetry of some, culminating in the adult form. Tissue engineering is the emerging discipline of design and construction of spare parts for the human body to restore function based on principles of molecular developmental biology and morphogenesis governed by bioengineering. The three key ingredients for both morphogenesis and tissue engineering are inductive signals, responding stem cells, and the extracellular matrix. Among the many tissues in the human body, bone has considerable powers for regeneration and is a prototype model for tissue engineering based on morphogenesis. Implantation of demineralized bone matrix into subcutaneous sites results in local bone induction. This model mimics sequential limb morphogenesis and permitted the isolation of bone morphogens. Although it is traditional to study morphogenetic signals in embryos, bone morphogenetic proteins (BMPs), the inductive signals for bone, were isolated from demineralized bone matrix from adults. BMPs and related cartilage-derived morphogenetic proteins (CDMPs) initiate, promote, and maintain chondrogenesis and osteogenesis and have actions beyond bone. The symbiosis of bone inductive and conductive strategies are critical for tissue engineering, and is in turn governed by the context and biomechanics. The context is the microenvironment, consisting of extracellular matrix, which can be duplicated by biomimetic biomaterials such as collagens, hydroxyapatite, proteoglycans, and cell adhesion proteins including fibronectins. Thus, the rules of architecture for tissue engineering are an imitation of the laws of developmental biology and morphogenesis, and thus may be universal for all tissues, including bones and joints.

Adult↗
PubMed1985

Effects of a biomimetic superoxide dismutase on complete and multistage carcinogenesis in mouse skin.

The effects of a selective detoxifier of the proximate oxygen radical, superoxide anion, on the induction of tumors in the skin of CD-1 mice by either the initiation-promotion regimen or the complete carcinogenesis process were investigated. The principle agent of interest, copper (II) (3,5-diisopropylsalicylate)2 (CuDIPS), is a low molecular weight, lipophilic copper coordination complex that catalytically disproportionates superoxide anion at a rate comparable to native Cu-Zn superoxide dismutase (SOD). The protocols used to elicit tumors were: (i) a single application of 0.2 mumol of 7,12-dimethylbenz[a]anthracene (DMBA) followed by twice-weekly applications of 12-O-tetradecanoylphorbol-13-acetate (TPA) in an initiation-promotion study, and (ii) either a single application of 3.6 mumol DMBA followed by no further treatment or weekly applications of 0.2 mumol DMBA in complete carcinogenesis protocols. Application of 2 mumol CuDIPS 15 min prior to the initiating dose of DMBA was without significant effect on tumor yield or incidence, whereas application prior to each dose of TPA substantially reduced tumor incidence and yield. This anti-promoting property of CuDIPS can be attributed to its SOD-mimetic activity in as much as the corresponding zinc coordination complex lacking in SOD activity, zinc (II) (3,5-diisopropylsalicylate)2, was non-inhibitory. Significant reductions in tumor yield were also observed when CuDIPS was applied prior to DMBA in either of the complete carcinogenesis protocols. Additionally, covalent binding of [3H]DMBA to epidermal DNA was markedly reduced by CuDIPS pre-treatment, suggesting that the anti-carcinogenic properties may reflect a perturbation in superoxide anion-dependent metabolic activation of DMBA. The induction by DMBA of ornithine decarboxylase activity, a biochemical marker of tumor promoter activity, was not affected by CuDIPS; however, induction of ornithine decarboxylase by TPA was potently blocked. Collectively, these effects of a biomimetic SOD further implicate reactive oxygen species at multiple stages in chemical carcinogenesis.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1999

alpha-BSM: a biomimetic bone substitute and drug delivery vehicle.

alpha-BSM is a biomimetic endothermically setting apatitic calcium phosphate bone substitute material. Its injectability and ability to harden at body temperature in the presence of physiologic saline, and other buffering agents, makes it an attractive clinical bone substitute and delivery vehicle for therapeutic agents in orthopaedic and dental applications. In osseous tissue, alpha-BSM alone remodels into bone and promotes bone healing. alpha-BSM treatment has been shown in several animal models to be effective in promoting healing of surgically created critical size defects and restoring bone biomechanical strength to values equal to or greater than values achieved with autograft controls. In vitro studies with alpha-BSM containing gentamicin show that antibiotics can be incorporated stably into alpha-BSM and that the release kinetics can be controlled with the appropriate formulation and preparative procedures. Growth factors and enzymes also are compatible with the alpha-BSM setting reaction. The incorporation of recombinant human bone morphogenetic protein-2 with alpha-BSM was shown to be effective in stimulating bone formation and accelerating restoration of the differentiated phenotype in an osteotomy model. Clinical trial investigators in Europe currently are using alpha-BSM implantations for treatment of fractures and other indications.

Animals↗
PubMed2001

Biomimetic finger control by filtering of distributed forelimb pressures.

A linear filter was developed for decoding finger commands from volitional pressures distributed within the residual forelimb. Filter parameters were based on dynamic pressures recorded from the residual limb within its socket, during specific finger commands. A matrix of signal features was derived from eight-dimensional (8-D) pressure vectors, and its pseudoinverse comprised the filter parameters. Results with amputees showed that the filter could discriminate specific finger flexion commands, suggesting that pressure vector decoding (PVD) can provide them with biomimetic finger control.

Adult↗
PubMed1999

Rationalization of esthetic restorative dentistry based on biomimetics.

UNLABELLED: The exponential progressivism that characterizes the current decade often comes with substantial financial implications. Dental care is not spared by this phenomenon. However, new generations of concepts emerging from biomimetics provide the operator with the ability to restore the biomechanical, structural, and esthetic integrity of teeth. The development of adhesion and the evolution of porcelain veneers constitute striking examples of this nascent process. Indications for bonding porcelain are extending to more perilous situations (crown-fractured incisors, nonvital teeth), resulting in considerable improvements, comprising both the medical-biologic aspect (economy of sound tissues and maintenance of tooth vitality) and the socioeconomical context (decrease of costs compared to traditional and more invasive prosthetic treatments). CLINICAL SIGNIFICANCE: In the bonded porcelain veneer and its extensions, restorative dentistry has found new solutions for the anterior segment that balance the need for functional and esthetic reconstruction. The optimal stiffness of porcelain in thin section, the ideal surface characteristics, and the biomechanical continuum achieved through high performance bonding mean the crown of the tooth as a whole can support incisal or masticatory function. By the same token, the conduction of optical effects from within the tooth combined with the ideal surface features of the porcelain veneer make this restorative approach the ultimate in esthetic satisfaction, for both the practitioner and the patient.

Cuspid↗
PubMed1998

Catalytic galactose oxidase models: biomimetic Cu(II)-phenoxyl-radical reactivity.

Biomimetic functional models of the mononuclear copper enzyme galactose oxidase are presented that catalytically oxidize benzylic and allylic alcohols to aldehydes with O2 under mild conditions. The mechanistic fidelity between the models and the natural system is pronounced. Modest structural mimicry proves sufficient to transfer an unusual ligand-based radical mechanism, previously unprecedented outside the protein matrix, to a simple chemical system.

Alcohols↗
PubMed1992

Iron uptake and molecular recognition in Pseudomonas putida: receptor mapping with ferrichrome and its biomimetic analogs.

The presence of an Fe(3+)-ferrichrome uptake system in fluorescent Pseudomonas spp. was demonstrated, and its structural requirements were mapped in Pseudomonas putida with the help of biomimetic ferrichrome analogs. Growth tests, 55Fe3+ uptake, and competition experiments demonstrated that the synthetic L-alanine derivative B5 inhibits the action of ferrichrome but does not facilitate Fe3+ transport, while the enantiomeric D-Ala derivative B6 fails to compete with ferrichrome. Contraction of the molecule's envelope by replacing L-Ala by glycine provided a synthetic carrier, B9, which fully simulates ferrichrome as a growth promoter. Sodium azide inhibited 55Fe3+ uptake of the Gly derivative B9, suggesting an active transport process. These data demonstrate the chiral discrimination of the ferrichrome receptor and its sensitivity to subtle structural changes. They further confirm that receptor binding is a necessary but not sufficient condition for Fe3+ uptake to occur and suggest that binding to the receptor and transport proteins might rely on different recognition patterns.

Bacterial Outer Membrane Proteins↗
PubMed1997

Advanced EPR spectroscopy on electron transfer processes in photosynthesis and biomimetic model systems.

This review focuses on the recent advances in EPR spectroscopy as they are applied both to photoinduced electron transfer in the photosynthetic apparatus and to biomimetic systems. The review deals with time-resolved direct-detection cw and pulsed EPR and ENDOR methods, both at conventional bands [X-(9.5 GHz), K-(24 GHz), and Q-(35 GHz)(] and at high frequency bands (W-band, 95 GHz, and even higher frequency bands). EPR studies on photosynthetic and model systems in their doublet, triplet and radical pair states are surveyed, including their static and dynamic properties. APplications of time-resolved EPR in studying photoinduced electron and energy transfer in isotropic and anisotropic environments, and the concepts of electron spin polarization and magnetic field effects in photochemical reactions are also reviewed.

Electron Spin Resonance Spectroscopy↗
PubMed2001

Image-based biomimetic approach to reconstruction of the temporomandibular joint.

This article will present an image-based approach to the designing and manufacturing of biomimetic tissue engineered temporomandibular (TMJ) condylar prosthesis. Our vision of a tissue-engineered TMJ prosthesis utilizes a 3-D designed and manufactured biodegradable scaffold shaped similar to a condylar head and neck, i.e. a condylar-ramus unit (CRU). The fabricated CRU scaffold can be constructed with a specific intra-architectural design such that it will enhance the formation of tissue from implanted cells placed within its interstices. These biologic cues could influence scaffold-implanted mesenchymal stem cells (MSC) or bone marrow stromal cells (BMSC) to form a fibrocartilaginous joint surface, or cap, on top of a bony strut, similar to a costochondral rib graft (CCRG), which could be fixed to the mandibular ramus. This new approach to tissue engineering a TMJ would be advantageous because of its patient site-specific anatomical configuration as well as its potential ability to adapt to the loading forces placed on it during function.

Biocompatible Materials↗
PubMed2001

Artificial ears for a biomimetic sonarhead: from multiple reflectors to surfaces.

This work presents an evolutionary approach to pinna design. Narrowband echolocating bats move the pinna to alter the directional sensitivity of their perceptual systems. Adding pinnae to RoBat--a biomimetic sonarhead mounted on a mobile robot--is the goal of this work. After a description of the earlier work on artificial pinnae consisting of multiple reflectors around the transducer, an acoustic model, inspired by a physical model of sound diffraction and reflections in the human concha, is described and revisited as the model to use for evolving complex shapes. A genetic algorithm evolved the shape of the pinnae with respect to desired features of the directivity pattern of the receiver transducers. Some interesting paraboloid shapes for specific echolocating behaviors were evolved, improving performance with respect to the bare transducer's performance.

Animals↗
PubMed2001

Mechanistic studies on the biomimetic reduction of tetrahydroxynaphthalene, a key intermediate in melanin biosynthesis.

1,3,6,8-Tetrahydroxynaphthalene (T4HN) is an aromatic polyketide, serving as a general precursor of fungal melanin. Melanin biosynthesis involves two consecutive deoxygenations of T4HN, consisting of the reduction of a phenolic carbon followed by dehydration. The first reduction to produce scytalone was studied in a biomimetic reduction with sodium borohydride. The reduction required a strong alkaline condition, leading to the tautomerization of T4HN to a reactive species whose structure was clarified by NMR spectroscopy.

Magnetic Resonance Spectroscopy↗
PubMed2003

Biomimetic oxidation of curcumin with hydrogen peroxide catalyzed by 5,10,15,20-tetraarylporphyrinatoiron(III) chlorides in dichloromethane.

The biomimetic oxidation of curcumin, a main turmeric pigment with hydrogen peroxide catalyzed by different 5,10,15,20-tetraarylporphyrinatoiron(III) chlorides [TAPFe(III)Cl] in dichloromethane has been studied to give a C-C coupled curcumin dimer in 40-70% yield. The structure of the dimer has been elucidated by (1)H-, (13)C-NMR, IR and FAB-Mass spectroscopic data.

Curcumin↗
PubMed2006

Isolation and biomimetic synthesis of anti-inflammatory stilbenolignans from Gnetum cleistostachyum.

One new stilbenolignan, gnetucleistol F (1), and four known stilbenolignans, gnetofuran A (2), lehmbachol D (3), gnetifolin F (4) and gnetumontanin C (5) were isolated from the lianas of Gnetum cleistostachyum C. Y. CHENG (Gnetaceae). Their structures and relative configurations were determined by means of spectroscopic evidence. Compounds 1, 2, 3 and 4 were synthesized for the first time on the basis of their biogenetic pathway, and their possible biomimetical synthetic mechanisms were discussed. The pharmacological activities of all stilbenolignans have been tested. Among them, 1, 2, 3, 4 and 5 showed moderate inhibitory activities on TNF-alpha and 1 also showed potent inhibitory activity on malondialdehyde.

Anti-Inflammatory Agents↗
PubMed1993

[A new lupin alkaloid, (-)-leontalbinine N-oxide, in Sophora flavescens var. angustifolia seeds and its synthesis by biomimetic transformation from (+)-matrine N-oxide].

The possibility of the biomimetic transformation of (+)-matrine N-oxide, a main alkaloid in Sophora flavescens var. angustifolia, under various oxidative conditions was examined by the use of several metallic ions. When (+)-matrine N-oxide was warmed with FeSO4, or Fe(COOH)2 in MeOH-H2O at 40 degrees C, (-)-7, 11-didehydromatrine [(-)-leontalbinine], a minor alkaloid in the same plant, was obtained along with (+)-matrine. This selective formation of (-)-leontalbinine seems to be specific to the reaction of (+)-matrine N-oxide with ferrous reagents. In addition, the structure of the newly isolated minor lupin alkaloid from the seeds of S. flavescens. was determined as (-)-leontalbinine N-oxide from its spectral comparison with the authentic sample.

Alkaloids↗
PubMed2000

[Total synthesis of crassostreaxanthin B directed toward the biomimetic synthesis of carotenoids].

Marine carotenoids halocynthiaxanthin 2, mytiloxanthin 3 and crassostreaxanthin B 4 have characteristic structures, commonly possessing a monoacetylenic end group. The cyclopentyl end group of 3 is believed to be formed in nature from the epoxide end group of 5,6-epoxy carotenoids such as 2 (Chart 1, route a). It is also conceivable that 4 including a novel tetrasubstituted olefinic end group arises from epoxy carotenoids by the opening of the C-6-oxygen bond of the oxirane ring and the subsequent migration of the methyl group at the C-1 position (route b). We found that treatment of the epoxide 6a having a partial structure of epoxy carotenoids with Lewis acids gave the cyclopentyl ethyl ketone 9 possessing the same configuration as 3, and the acyclic tetrasubstituted olefinic methyl ketone 11 including a partial structure of 4 (Chart 2). It supported the proposed metabolic pathway of 5,6-epoxy carotenoids. Toward the biomimetic synthesis of 4, we examined the reaction of epoxides having several substituents at C-6 position with Lewis acids. Among these epoxides, an epoxide 60 was found to provide a tetrasubstituted compound 61 as a major product. This could be converted into an aldehyde 73 in 8 steps which was transformed into a compound 75 through the coupling reaction with vinyllithium 63. Then, the first total synthesis of 4 was accomplished via the double Wittig condensation of 75 with phosphonium salts 76 and 77.

Antineoplastic Agents↗
PubMedDate not supplied

Biomimetic conversion of (3S)-(-)-neodictyoprolenol to optically pure (1S,2R)-(-)-dictyopterene B, marine algal sex pheromone.

Both enantiomers of (3S)-(-)- and (3R)-(+)-Neodictyoprolenol [(3S,5Z,8Z)-(-)-1,5,8-undecatrien-3-ol] were successfully converted to the algal sex pheromone, (1S,2R)-(-)-dictyopterene B and (1R,2S)-(+)-dictyopterene B in high enantiomeric purities (e. e. > 99%), respectively, by the biomimetic reaction involving phosphorylation and elimination under a mild condition.

Fatty Alcohols↗
PubMed1997

Effect of urea on biomimetic aggregates.

The effect of urea on biomimetic aggregates (aqueous and reversed micelles, vesicles and monolayers) was investigated to obtain insights into the effect of the denaturant on structured macromolecules. Direct evidence obtained from light scattering (static and dynamic), monolayer maximum isothermal compression and ionic conductivity measurements, together with indirect evidence from fluorescence photodissociation, fluorescence suppression, and thermal reactions, strongly indicates the direct interaction mechanism of urea with the aggregates. Preferential solvation of the surfactant headgroups by urea results in an increase in the monomer dissociation degree (when applied), which leads to an increase in the area per headgroup and also in the loss of counterion affinities.

Coated Vesicles↗