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At least 19 recordsLinked to original sources

PubMed1989

Biomimetic studies using artificial systems. IV. Biomimetic peptide synthesis by using multifunctionalized crown ethers as a novel enzyme model. A new concept in mimicking of enzyme-catalyzed bond-forming reactions.

A novel approach to the mimicking of enzyme-catalyzed bond-forming reactions has been examined using multifunctionalized chiral crown ethers. In addition to the 18-crown-6 moiety as a binding site, the host have one thiol and one thio ester with an N-protected alpha-amino acid or a peptide, and have successfully achieved peptide synthesis in an enzyme-mimetic reaction mode. This new method involves the following three key reactions. (1) Intra-complex thiolysis: the host carries out the rapid intra-complex thiolysis of alpha-amino acid ester salts to form the dithioester, corresponding to the assembly of two guests by the host. (2) Amide formation: intramolecular aminolysis occurs between the bound guests to form the amide bond. (3) Peptide chain elongation: as the thiol reactive group is regenerated, the above two reactions are repeated to elongate the peptide chain. Formal turnover of the enzyme model has been demonstrated by the synthesis of a tetrapeptide derivative by the repetition of the above processes.

Catalysis↗

PubMed2001

New family of glutathionyl-biomimetic ligands for affinity chromatography of glutathione-recognising enzymes.

Three anthraquinone glutathionyl-biomimetic dye ligands, comprising as terminal biomimetic moiety glutathione analogues (glutathionesulfonic acid, S-methyl-glutathione and glutathione) were synthesised and characterised. The biomimetic ligands were immobilised on agarose gel and the affinity adsorbents, together with a nonbiomimetic adsorbent bearing Cibacron Blue 3GA, were studied for their purifying ability for the glutathione-recognising enzymes, NAD+-dependent formaldehyde dehydrogenase (FaDH) from Candida boidinii, NAD(P)+-dependent glutathione reductase from S. cerevisiae (GSHR) and recombinant maize glutathione S-transferase I (GSTI). All biomimetic adsorbents showed higher purifying ability for the target enzymes compared to the nonbiomimetic adsorbent, thus demonstrating their superior effectiveness as affinity chromatography materials. In particular, the affinity adsorbent comprising as terminal biomimetic moiety glutathionesulfonic acid (BM1), exhibited the highest purifying ability for FaDH and GSTI, whereas, the affinity adsorbent comprising as terminal biomimetic moiety methyl-glutathione (BM2) exhibited the highest purifying ability for GSHR. The BM1 adsorbent was integrated in a facile two-step purification procedure for FaDH. The purified enzyme showed a specific activity equal to 79 U/mg and a single band after sodium dodecylsulfate-polyacrylamide gel electrophoresis analysis. Molecular modelling was employed to visualise the binding of BM1 with FaDH, indicating favourable positioning of the key structural features of the biomimetic dye. The anthraquinone moiety provides the driving force for the correct positioning of the glutathionyl-biomimetic moiety in the binding site. It is located deep in the active site cleft forming many favourable hydrophobic contacts with hydrophobic residues of the enzyme. The positioning of the glutathione-like biomimetic moiety is primarily achieved by the strong ionic interactions with the Zn2+ ion of FaDH and Arg 114, and by the hydrophobic contacts made with Tyr 92 and Met 140. Molecular models were also produced for the binding of BM1 and BM3 (glutathione-substituted) to GSTI. In both cases the biomimetic dye forms multiple hydrophobic interactions with the enzyme through binding to a surface pocket. While the glutathioine moiety of BM3 is predicted to bind in the crystallographically observed way, an alternative, more favourable mode seems to be responsible for the better purification results achieved with BM1.

Aldehyde Oxidoreductases↗

PubMed1995

Biomimetic dye affinity chromatography for the purification of bovine heart lactate dehydrogenase.

Three biomimetic dye ligands bearing as a triazine-linked terminal moiety a carboxylated structure, which mimics substrates and inhibitors of L-lactate dehydrogenase (LDH), were immobilized on cross-linked agarose Ultrogel A6R. These biomimetic dyes are purpose-designed analogues of commercial monochlorotriazine Cibacron Blue 3GA (CB3GA) and parent dichlorotriazine Vilmafix Blue A-R (VBAR). The corresponding biomimetic adsorbents, along with non-biomimetic adsorbents bearing CB3GA and VBAR, were evaluated for their ability to purify LDH from bovine heart crude extract. When compared with non-biomimetic adsorbents, all biomimetic adsorbents exhibited a higher purifying ability. Further, one immobilized biomimetic dye, bearing mercaptopyruvic acid as biomimetic moiety, displayed the highest purifying ability. The concentration of immobilized dye affected both the capacity and the purifying ability of the affinity column, exhibiting an optimum value 2.2 mumol dye/g moist gel. This affinity adsorbent was exploited for the purification of LDH from bovine heart in a two-step procedure. The procedure consisted in a biomimetic dye affinity chromatography step (NAD+/sulphite elution, 25-fold purification, 64% step yield), followed by DEAE-agarose ion-exchange chromatography (1.4-fold purification, 78% step yield). The purified enzyme exhibited a specific activity of ca. 480 u/mg at 25 degrees C (content of impurities: pyruvate kinase and glutamic-oxaloacetic transaminase were not detected; malate dehydrogenase, 0.01%), compared with ca. 250 u/mg of commercial bovine heart LDH (malate dehydrogenase, 0.05%) suitable for analytical purposes.

Animals↗

PubMed1996

Molecular modelling for the design of chimaeric biomimetic dye-ligands and their interaction with bovine heart mitochondrial malate dehydrogenase.

Molecular modelling and kinetic inhibition studies, as well as KD determinations by both difference-spectra and enzyme-inactivation studies, were employed to assess the ability of purpose-designed chimaeric biomimetic dyes (BM dyes) to act as affinity ligands for bovine heart L-malate dehydrogenase (MDH). Each BM dye was composed of two enzyme-recognition moieties. The terminal biomimetic moiety bore a carboxyl or a keto acid structure linked to the triazine ring, thus mimicking the substrate of MDH. The chromophore anthraquinone moiety remained unchanged and the same as that of the parent dye Vilmafix Blue A-R (VBAR), recognizing the nucleotide-binding site of MDH. The monochlorotriazine BM dyes did not inactivate MDH but competitively inhibited inactivation by the parent dichlorotriazine dye VBAR. Dye binding to MDH was accompanied by a characteristic spectral change in the range 500-850 nm. This phenomenon was reversed after titration with increasing amounts of NADH. When compared with VBAR, Cibacron Blue 3GA and two control non-biomimetic anthraquinone dyes, all BM dyes exhibited lower KD values and therefore higher affinity for MDH. The enzyme bound preferably to BM ligands substituted with a biomimetic aromatic moiety bearing an alpha-keto acid group and an amide linkage, rather than a monocarboxyl group. Thus the biomimetic dye bearing p-aminobenzyloxanilic acid as its terminal biomimetic moiety (BM5) exhibited the highest affinity (KD 1.3 microM, which corresponded to a 219-fold decrease over the KD of a control dye). BM5 displayed competitive inhibition with respect to both NADH (Ki 2.7 microM) and oxaloacetate (Ki 9.6 microM). A combination of molecular modelling and experimental studies has led to certain conclusions. The positioning of the dye in the enzyme is primarily achieved by the recognition and positioning of the nucleotide-pseudomimetic anthraquinone moiety. The hydrophobic groups of the dye provide the driving force for positioning of the ketocarboxyl biomimetic moiety. A match between the alternating polar and hydrophobic regions of the enzyme binding site with those of the biomimetic moiety is desirable. The length of the biomimetic moiety should be conserved in order for the keto acid to approach the enzyme active site and form charge-charge interactions.

Affinity Labels↗

PubMed1999

Molecular modeling for the design of a biomimetic chimeric ligand. Application to the purification of bovine heart L-lactate dehydrogenase.

Molecular modeling was employed for the design of a biomimetic chimeric ligand for L-lactate dehydrogenase (LDH). This ligand is an anthraquinone monochlorotriazinyl dye comprising two moieties: (a) the ketocarboxyl biomimetic moiety, 2-(4-aminophenyl)-ethyloxamic acid, linked on the monochlorotriazine ring, mimicking the natural substrate of LDH, and (b) the anthraquinone chromophore moiety, linked also on the same monochlorotriazine ring via a diaminobenzenesulfonate group, acting as pseudomimetic of the cofactor NAD+. The positioning of the dye in the enzyme's binding site is primarily achieved by the recognition and positioning of the pseudomimetic anthraquinone moiety. The positioning of the biomimetic ketocarboxylic moiety is based on a match between the polar and hydrophobic regions of the enzyme's binding site with those of the biomimetic moiety of the ligand. The length of the biomimetic moiety is predetermined for the ketoacid to approach the enzyme catalytic site and form charge-charge interactions. The biomimetic chimeric ligand and the commercial nonbiomimetic ligand Cibacron(R) blue 3GA (CB3GA), were immobilized on crosslinked beaded agarose gel via their chlorotriazine ring. The two affinity adsorbents were evaluated for their purifying ability for LDH from six sources (bovine heart and pancreas, porcine muscle, chicken liver and muscle, and pea seeds). The biomimetic adsorbent exhibited approximately twofold higher purifying ability for LDH compared to the CB3GA adsorbent; therefore, the former was integrated in the purification procedure of LDH from bovine heart extract. The LDH afforded by this two-step purification procedure shows specific activity equal to 600 U/mg (25 degrees C) and a single band after SDS-PAGE analysis.

Animals↗

PubMed2002

Galactosyl-biomimetic dye-ligands for the purification of Dactylium dendroides galactose oxidase.

Two anthraquinone galactosyl-biomimetic dye-ligands comprising, as terminal biomimetic moiety, galactose analogues (1-amino-1-deoxy-beta-D-galactose and D(+)-galactosamine) were designed for the enzyme galactose oxidase (GAO), using molecular modelling, synthesized and characterized. The biomimetic ligands were immobilized on agarose beads and the affinity adsorbents, together with a non-biomimetic adsorbent bearing Cibacron Blue 3GA, were studied for their ability to purify GAO from Dactylium dendroides. Both biomimetic adsorbents showed higher purifying ability for GAO compared to the non-biomimetic adsorbent, thus demonstrating their superior effectiveness as affinity chromatography materials. In particular, the affinity adsorbent comprising, as terminal biomimetic moiety, 1-amino-1-deoxy-beta-D-galactose (BM1) exhibited the highest purifying ability for GAO. This affinity adsorbent did not bind galactose dehydrogenase, glucose dehydrogenase, alcohol dehydrogenase, or glucose oxidase. The dissociation constant (K(D)) of the immobilized BM1 ligand with GAO was found to be equal to 45.8 microM, whereas the binding capacity was equal to 709 U per ml adsorbent. Therefore, the BMI adsorbent was integrated in a facile two-step purification procedure for GAO. The purified enzyme showed a specific activity equal to 2038 U/mg, the highest reported so far, approximately 74% overall recovery and a single band after sodium dodecylsulfate-polyacrylamide gel electrophoresis analysis.

Chromatography, Liquid↗

PubMed2003

Biomimetic materials for tissue engineering.

The development of biomaterials for tissue engineering applications has recently focused on the design of biomimetic materials that are capable of eliciting specific cellular responses and directing new tissue formation mediated by biomolecular recognition, which can be manipulated by altering design parameters of the material. Biomolecular recognition of materials by cells has been achieved by surface and bulk modification of biomaterials via chemical or physical methods with bioactive molecules such as a native long chain of extracellular matrix (ECM) proteins as well as short peptide sequences derived from intact ECM proteins that can incur specific interactions with cell receptors. The biomimetic materials potentially mimic many roles of ECM in tissues. For example, biomimetic scaffolds can provide biological cues for cell-matrix interactions to promote tissue growth, and the incorporation of peptide sequences into materials can also make the material degradable by specific protease enzymes. This review discusses the surface and bulk modification of biomaterials with cell recognition molecules to design biomimetic materials for tissue engineering. The criteria to design biomimetic materials such as the concentration and spatial distribution of modified bioactive molecules are addressed. Recent advances for the development of biomimetic materials in bone, nerve, and cardiovascular tissue engineering are also summarized.

Amino Acid Sequence↗

PubMed1996

Biomimetic-dye affinity chromatography for the purification of mitochondrial L-malate dehydrogenase from bovine heart.

Seven biomimetic anthraquinone triazinyl dye-ligands, bearing as triazine-linked terminal moiety (keto)carboxylated structures mimicking substrates and inhibitors of malate dehydrogenase (MDH), were immobilised on cross-linked agarose Ultrogel A6R. These biomimetic ligands are terminal-ring analogues of commercial nonbiomimetic Cibacron blue 3GA (CB3GA) and parent Vilmafix blue A-R (VBAR). The biomimetic-dye adsorbents, along with nonbiomimetic adsorbents bearing immobilised CB3GA and VBAR, were evaluated for their ability to purify mitochondrial malate dehydrogenase (mMDH) from bovine heart. All but two biomimetic-dye adsorbents displayed higher purifying ability for MDH, compared to nonbiomimetic-dye adsorbents. Furthermore, immobilised anthraquinone-dyes were able to discriminate between the mitochondrial and the cytoplasmic MDH isoenzymes, binding only to the former. One immobilised biomimetic-dye (BM5), bearing as biomimetic terminal moiety 4-aminophenyloxanylic acid, showed the highest purifying ability. This affinity adsorbent was exploited in the purification of mMDH from unpretreated bovine heart extract in one-step. The procedure afforded mMDH at 54% overall yield and of specific activity approx. 1300 U mg-1 (25 degrees C), using step-elution with a mixture containing 0.1 mM beta-nicotinamide adenine dinucleotide (NAD+) and 1.5 mM sulphite. Commercial analytical-grade bovine heart mitochondrial MDH, when assayed under identical conditions, gave a specific activity not exceeding 950 U mg-1. The well-known adsorbent Cibacron blue 3GA-agarose exhibited 8% lower recovery and 25% lower purification for mMDH. The product obtained from the procedure based on the BM5-adsorbent was free of cytoplasmic MDH, glutamic-oxaloacetic transaminase (GOT) and fumarase, and since it has also shown high specific activity, it should be suitable for analytical applications.

Acetone↗

PubMed2000

Biomimetic dyes as affinity chromatography tools in enzyme purification.

Affinity adsorbents based on immobilized triazine dyes offer important advantages circumventing many of the problems associated with biological ligands. The main drawback of dyes is their moderate selectivity for proteins. Rational attempts to tackle this problem are realized through the biomimetic dye concept according to which new dyes, the biomimetic dyes, are designed to mimic natural ligands. Biomimetic dyes are expected to exhibit increased affinity and purifying ability for the targeted proteins. Biocomputing offers a powerful approach to biomimetic ligand design. The successful exploitation of contemporary computational techniques in molecular design requires the knowledge of the three-dimensional structure of the target protein, or at least, the amino acid sequence of the target protein and the three-dimensional structure of a highly homologous protein. From such information one can then design, on a graphics workstation, the model of the protein and also a number of suitable synthetic ligands which mimic natural biological ligands of the protein. There are several examples of enzyme purifications (trypsin, urokinase, kallikrein, alkaline phosphatase, malate dehydrogenase, formate dehydrogenase, oxaloacetate decarboxylase and lactate dehydrogenase) where synthetic biomimetic dyes have been used successfully as affinity chromatography tools.

Chromatography, Affinity↗

PubMed2003

Elastic cartilage engineering using novel scaffold architectures in combination with a biomimetic cell carrier.

Tissue engineering of an elastic cartilage graft that meets the criterion for both structural and functional integration into host tissue, as well as allowing for a clinically tolerable immune response, is a challenging endeavour. Conventional scaffold technologies have limitations in their ability to design and fabricate complex-shaped matrix architectures of structural and mechanical equivalence to elastic cartilage found in the body. We attempted to investigate the potential of conventionally isolated and passaged chondrocytes (2D environment) when seeded and cultured in combination with a biomimetic hydrogel in a mechanically stable and biomimetic composite matrix to form elastic cartilage within ectopic implantation sites. In vitro cultured scaffold/hydrogel/chondrocytes constructs showed islets of cartilage and mineralized tissue formation within the cell-seeded specimens in both pig and rabbit models. Specimens with no cells seeded showed only vascularized fibrous tissue ingrowth. These studies demonstrated the potential of such scaffold/hydrogel/cell constructs to support chondrogenesis in vivo. However, it also showed that even mechanically stable scaffolds do not allow regeneration of a large mass of structural and functional cartilage within a matrix architecture seeded with 2D passaged chondrocytes in combination with a cell biomimetic carrier. Hence, future experiments will be designed to evaluate an initial 3D culture of chondrocytes, effect on cell phenotype and their subsequent culture within biomimetic 3D scaffold/cell constructs.

Adult↗

PubMed2003

Application of the empirical force field to macrocyclic ion carriers, siderophores, and biomimetic analogs.

The empirical force field (EFF), developed by Prof. Lifson, was applied to the study of macrocyclic alkali ion carriers and to di- and tripodal and open chain siderophores and synthetic biomimetic molecules binding transition metals. The highly symmetric nature of these structures facilitated a favorable coordination geometry of the ligating groups about the metal, which helped organize the entire molecule into a fairly rigid structure. In our combined experimental-theoretical approach, EFF calculations were used to help predict likely candidates to synthesize, and provided a wealth of structural data to complement what we learned from the spectroscopic measurements, while feedback from these measurements allowed us to continue improving the EFF itself. The simple, highly modular design of the biomimetic analogs allowed rapid synthesis and systematic examination of a large number of related structures, as well as facilitating an efficient, piecewise conformational scanning for the theoretical calculations. In the early years, we focused on macrocyclic polylactones and lactams binding monovalent alkali ions, particularly the natural products enniatin and valinomycin, including inside a crystal lattice. Later we switched to bi- and tridentate siderophores, natural microbial iron carriers, and synthetic biomimetic analogs-in particular, of enterobactin, ferrichrome, and ferrioxamine B. Over the years a large number of biomimetic siderophores have been prepared, some active in a broad range of microorganisms while others are highly species specific. The results of this work have broad applications in many areas, including the design of novel drugs and antimicrobial agents, helical polymeric structures, and polynuclear metal complexes.

Ion Transport↗

PubMed1995

The interaction of Candida boidinii formate dehydrogenase with a new family of chimeric biomimetic dye-ligands.

Seven chimeric biomimetic dye-ligands (BM) are purpose-designed and synthesized by specific structural modification of the parent anthraquinone dichlorotriazine dye Vilmafix blue A-R (VBAR). Each BM dye is composed of two enzyme-recognition moieties. The terminal biomimetic moiety bears a variable carboxylated structure linked to the triazine ring, thus mimicking the substrate of formate dehydrogenase (FDH). The anthraquinone moiety remains the same as that of the parent dye and recognizes the nucleotide-binding area of the target enzyme. Dyes are purified by liquid column chromatography (typically 99%), analyzed by liquid-paper chromatography, thin-layer chromatography, and high-performance liquid chromatography, and their lambda max and epsilon values are determined. The ability of dyes to act as affinity ligands versus Candida boidinii FDH is evaluated by kinetic studies and determining KD values from both difference spectra and enzyme inactivation studies. The parent dichlorotriazine dye VBAR binds specifically and irreversibly to FDH (k3 0.19 min-1; KD 19.3 microM). The inactivation of the NAD(+)-dependent enzyme by VBAR is competitively inhibited by NAD+, NADH, and ADP. Quantitatively inhibited FDH contained approx 1 mol of dye per mole of active site. The inhibition is irreversible and activity cannot be recovered either on incubation with 10 mM each of NAD+, NADH, and ADP or by extensive dialysis or gel filtration chromatography. The monochlorotriazine BM dyes do not inactivate FDH but inhibit competitively the inactivation by VBAR. When compared to VBAR and Cibacron blue 3GA (CB3GA), all BM dye-ligands exhibited lower KD values. FDH generally preferred binding to BM ligands which bore an aromatic terminal biomimetic moiety substituted with a monocarboxyl group rather than an alpha-ketoacid. Dye binding to FDH is accompanied by a characteristic spectral change in the range 550-800 nm. This phenomenon is perturbed after titration by increasing amounts of NAD+. Electrostatic interactions appeared to play a dominant role in the dye.FDH complex. The BM dye-ligand bearing a m-aminobenzoate at its terminal biomimetic moiety (BM1) exhibited the highest affinity (KD 1.6 microM, 8.0-fold decrease over CB3GA). BM1 differentiated between the binding sites of FDH, displaying uncompetitive inhibition with respect to NAD+ (Ki 15.6 microM) and competitive with respect to formate (Ki 18.1 microM).

Adenosine Diphosphate↗

PubMed2001

A comparison of the use of an ATP-based bioluminescent assay and image analysis for the assessment of bacterial adhesion to standard HEMA and biomimetic soft contact lenses.

The aim of this study was to investigate in vitro adhesion of clinically relevant bacteria to standard HEMA and novel biomimetic soft contact lenses (SCL) using bioluminescent ATP assay and image analysis. Unworn SCL were incubated with Pseudomonas aeruginosa, Staphylococcus epidermidis or Serratia marcescens suspended in sterile phosphate buffered saline (PBS). The level of bacterial adhesion after 1, 2, 4, 6 and 18h, was assessed using both image analysis and a bioluminescent ATP assay. Species differences in the overall level of adhesion to the different types of lens were observed using both measurement techniques. Generally bacterial adhesion was shown to peak at 4-6 h, then decline to a much lower level by 18 h. After 4 h, adhesion of all species of bacteria to the biomimetic SCL (omafilcon A) was found to be significantly lower than to the standard HEMA SCL (polymacon) (p<0.05. Student's t-test, n = 4). Both these techniques demonstrated that novel biomimetic SCL materials exhibit significantly lower bacterial adhesion in vitro compared to standard HEMA SCL materials. SCL manufactured with these novel biomimetic materials may reduce the risk of infection.

Adenosine Triphosphate↗

PubMed1995

Fragmentation reactions of aromatic cation radicals: a tool for the detection of electron transfer mechanisms in biomimetic and enzymatic oxidations.

1. Mechanistic criteria, based on the side-chain fragmentation reactions of aromatic cation radicals, involving the cleavage of a beta bond (i.e. C-H, C-Si and C-S) have been developed for the detection of electron transfer mechanisms in oxidative processes of alkylbenzenes and aromatic sulphides. 2. For benzylic oxidations, the distinction between electron transfer (ET) and hydrogen atom transfer mechanism (HAT) has been based: (a) on studies of intramolecular selectivity, which, with appropriate substrates (5-Z-1,2,3,-trimethylbenzenes and 4-Z-1,2-dimethylbenzenes, where Z = OMe, alkyl), turns out to be much higher in ET than in HAT processes; and (b) on products studies concerning the reactions of bicumyl and benzyltrimethylsilanes since in these systems, the nature of products can be significantly different for ET and HAT mechanisms. 3. These criteria have been applied to the reactions of alkylbenzenes with an NO3 radical (shown to be an ET process) as well as to the microsomal and biomimetic (by iron porphyrins in the presence of PhIO) side-chain oxidation of the same compounds, where the mechanistic probes have suggested a HAT mechanism, with the exception of the biomimetic oxidation of 4-methoxybenzyltrimethylsilane in CH2Cl2-H2O-MeOH, which probably occurs by an ET mechanism. 4. For the enzymatic and biomimetic oxidation of aromatic sulphides an oxygen transfer is suggested, since, with cumyl phenyl sulphide and 4-methoxybenzyl phenyl sulphide, these reactions lead exclusively to the corresponding sulphoxides and sulphones, whereas the same substrates, in genuine ET reactions, form cation radicals which undergo C-H and C-S bond cleavage. 5. An oxygen transfer mechanism is also likely in the biomimetic and enzymatic oxidations of sulphoxides since in these reactions 4-methoxybenzyl phenyl sulphoxide is exclusively converted to sulphone, whereas in ET reactions it forms only C-S bond cleavage products.

Animals↗

PubMed1991

[Problems of biomimetic chemistry].

The main goals of biomimetic chemistry have been formulated on the basis of the concept of biochemical organization. Biomimetic chemistry is defined as a science which employs the principles of biochemical organization (i. e., the principles of structural organization, functioning and regulation of biological systems at the levels corresponding to biomacromolecules, supramolecular complexes and subcellular structures) for the construction of artificial systems with predetermined properties or for conferring desired properties on natural biochemical systems with the help of artificial elements. The relationships between biomimetics and biochemical modelling are discussed. As examples of biomimetic systems, some enzymes entrapped into hydrated reverse micelles of a surfactant in an organic solvent and conjugates of proteins with polyalkylene oxidases are considered.

Biochemical Phenomena↗

PubMed2003

Potential of enzyme mimics in biomimetic sensors: a modified-cyclodextrin as a dehydrogenase enzyme mimic.

This paper reports the application of a dehydrogenase enzyme mimic as a biomimetic sensor. The model compound investigated was a beta-cyclodextrin (beta-CD) derivative with a nicotinamide group attached to the secondary face of a beta-CD (Fig. 1g). It was envisaged that the nicotinamide group would act as the electron transfer agent and that the cyclodextrin would provide a suitable hydrophobic cavity for the reaction to take place in. Ethanol, propranalol, dopamine and acetone were used as substrates in backgrounds of hydrophilic and hydrophobic anions. Electrochemical and fluorescence techniques were used to study the catalytic effects in solution. It was found that the size of the analyte and the hydrophobicity of the anion affected the catalytic activity of the dehydrogenase mimic. Catalytic effects were most enhanced with ethanol and dopamine in presence of larger and more strongly solvated anions, SO4(2-) and H2PO4- which are excluded from the cavity. The molecule was also immobilised in a sol-gel matrix and investigated as a sol-gel electrochemical biomimetic sensor. Concentration dependence with increasing aliquots of ethanol was observed. These results indicated that a re-usable biomimetic sensor is indeed feasible.

Biomimetic Materials↗

PubMed2004

Modulation of differentiation and mineralization of marrow stromal cells cultured on biomimetic hydrogels modified with Arg-Gly-Asp containing peptides.

We synthesized biomimetic hydrogels modified with an osteopontin-derived peptide (ODP) and used them as a substrate for in vitro culture of marrow stromal cells (MSCs) to investigate the effect of the biomimetic surface on differentiation of MSCs into osteoblasts. Proliferation and biological assays for 16 days proved that MSCs became differentiated into osteoblasts secreting osteogenic phenotypic markers such as alkaline phosphatase (ALP), osteopontin, and mineralized calcium. In addition, there was an additive effect of the cell-binding peptide on differentiation and mineralization of MSCs cultured in the presence of soluble osteogenic supplements in cell culture media. For example, calcium content at day 16 on peptide-modified hydrogels was significantly higher than on tissue culture polystyrene. Two general trends were observed: (1) proliferation of MSCs decreased as the amount of differentiation markers increased, and (2) higher peptide concentrations accelerated the differentiation of MSCs. On the hydrogel modified with ODP, ALP activity exhibited a maximum value of 36.7 +/- 4.2 pmol/cell/h at day 10 for the concentration of 2 micromol/g while the culture time needed for maximum ALP activity occurred on day 13 for the lower concentrations. On the same hydrogel, the calcium content at day 10 was 21.4 +/- 2.3 ng/cell for the peptide concentration of 2 micromol/g and 1.0 +/- 0.3 ng/cell for 1.0 micromol/g. We used Gly-Arg-Gly-Asp-Ser (GRGDS) for modification of the hydrogel as a comparison to the results with ODP. However, osteoblast development was not significantly affected by the nature of the binding peptide sequences. These results suggest that MSC function can be modulated by variation of the peptide concentration in biomimetic hydrogels used for scaffold-based bone tissue engineering.

Alkaline Phosphatase↗

PubMed2003

Biomimetic systems for studying actin-based motility.

Actin polymerization provides a major driving force for eukaryotic cell motility. Successive intercalation of monomeric actin subunits between the plasma membrane and the filamentous actin network results in protrusions of the membrane enabling the cell to move or to change shape. One of the challenges in understanding eukaryotic cell motility is to dissect the elementary biochemical and biophysical steps that link actin polymerization to mechanical force generation. Recently, significant progress was made using biomimetic, in vitro systems that are inspired by the actin-based motility of bacterial pathogens such as Listeria monocytogenes. Polystyrene microspheres and synthetic phospholipid vesicles coated with proteins that initiate actin polymerization display motile behavior similar to Listeria, mimicking the leading edge of lamellipodia and filopodia. A major advantage of these biomimetic systems is that both biochemical and physical parameters can be controlled precisely. These systems provide a test bed for validating theoretical models on force generation and polarity establishment resulting from actin polymerization. In this review, we discuss recent experimental progress using biomimetic systems propelled by actin polymerization and discuss these results in the light of recent theoretical models on actin-based motility.

Actins↗