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PubMed2005

Potential of biomimetic surfaces to promote in vitro osteoblast-like cell differentiation.

Bioactive glasses, osteoproductive materials, have received considerable attention as bone graft substitutes in the treatment of bony defects. More recent strategies for achieving a predictable periodontal regeneration include the use of enamel matrix proteins, due to their role in the formation of bone tissue. The aim of our study is to examine the effects of these materials on the proliferation and differentiation of the mouse preosteoblastic cell line MC3T3-E1. Cells were cultured up to 28 days in contact with three types of granules: Bioglass 45S5 granules (BG), 45S5 granules coated with enamel matrix proteins (Emdogain) (BG/EMD), and a less reactive glass used as a control (60S). Phase contrast microscopic observations have shown that all substrates supported the growth of osteoblastic cells. Zones of differentiation were observed at an earlier stage in cultures of BG and BG/EMD. TEM observations revealed ultrastructural features very close to what is observed in vivo during intramembranous ossification with a direct bone apposition on the bioactive glasses. Total protein production was higher in the cultures with BG and BG/EMD. Northern Blot analysis revealed a stimulation of the transcription factor Cbfa1/Runx2 at day 13 in cultures of BG when compared to the two other cultures. Bone sialoprotein (early marker of differentiation) and osteocalcin (marker of late-stage differentiation) expression was increased in cultures with BG and BG/EMD when compared to 60S. Taken together, our findings indicate that Bioglass alone or combined with Emdogain, have the ability to support the growth of osteoblast-like cells in vitro and to promote osteoblast differentiation by stimulating the expression of major phenotypic markers. In addition, we noticed that the bioactive granules coated with Emdogain revealed significantly higher protein production than the bioactive granules alone at day 20.

Biomarkers↗

PubMed2005

Self-assembled biomimetic monolayers using phospholipid-containing disulfides.

Several phospholipid-based disulfide molecules were synthesized and attached onto the gold-coated silicon wafer using the self-assembling method. The syntheses of these surface-modifying agents were conducted by introducing bromoethylphosphorate (PBr), phosphorylcholine (PC) or phosphorylethanolamine (PE) groups on the terminals of a dialkyl disulfide. After disulfides adsorption onto gold substrate surfaces, the composition, the film thickness, and the conformational order of self-assembled monolayer surfaces were explored and discussed in detail based on reflection-absorption infrared spectroscopy, contact angle measurement, Auger electron spectroscopy, X-ray photoelectron spectroscopy, and so on. The monolayer having the PBr end group could also be converted to a PC surface by treating with trimethylamine. The model functional surfaces of Au-SC11-PC, -PE, -PBr, -OH or corresponding mixed layers were used to mimic biomembrane surfaces. The monolayer having PC groups was found to reduce fibrinogen adsorption as evaluated from protein adsorption experiments using quartz crystal microbalance. It also showed relatively low platelet adherence compare to the glass, PBr and PE surfaces. The cell viability test also revealed that the PC surface displayed lower cytotoxicity than other surfaces.

Biomimetic Materials↗

PubMed2005

Plasma-treated nanostructured TiO(2) surface supporting biomimetic growth of apatite.

Although some types of TiO(2) powders and gel-derived films can exhibit bioactivity, plasma-sprayed TiO(2) coatings are always bioinert, thereby hampering wider applications in bone implants. We have successfully produced a bioactive nanostructured TiO(2) surface with grain size smaller than 50 nm using nanoparticle plasma spraying followed by hydrogen plasma immersion ion implantation (PIII). The hydrogen PIII nano-TiO(2) coating can induce bone-like apatite formation on its surface after immersion in a simulated body fluid. In contrast, apatite cannot form on either the as-sprayed TiO(2) surfaces (both <50 nm grain size and >50 nm grain size) or hydrogen-implanted TiO(2) with grain size larger than 50 nm. Hence, both a hydrogenated surface that gives rise to negatively charged functional groups on the surface and small grain size (<50 nm) that enhances surface adsorption are crucial to the growth of apatite. Introduction of surface bioactivity to plasma-sprayed TiO(2) coatings, which are generally recognized to have excellent biocompatibility and corrosion resistance as well as high bonding to titanium alloys, makes them more superior than many current biomedical coatings.

Apatites↗

PubMed2005

Helical rosette nanotubes: a biomimetic coating for orthopedics?

Helical rosette nanotubes (HRN) are obtained through an entropically driven self-assembly process of low-molecular-weight synthetic modules under physiological conditions. Counter-intuitively, these materials undergo extensive self-assembly under the effect of temperature, resulting in networks of very long nanotubes. We have previously shown, using an in vitro model, that titanium (Ti) coated with HRN containing a lysine side chain (HRN-K1) displayed enhanced osteoblast (OB) adhesion when compared to uncoated Ti (p < 0.01). Because it has been widely known that proteins play a critical role in OB adhesion on nanophase materials, here we examine OB adhesion on heated (+T) and unheated (-T) HRN-K1-coated Ti under serum (+S, presence of proteins) and serum-free (-S, absence of proteins) conditions. The results demonstrated that (a) while proteins enhanced OB adhesion on +T HRN-K1-coated Ti, they had no effect on -T HRN-K1-coated Ti, suggesting an active role played by the rosette nanotubes in promoting OB adhesion, and (b) under -S conditions, +T HRN-K1 induced the same level of OB adhesion as uncoated Ti under +S conditions, suggesting that +T HRN-K1 acts as a protein substitute. Finally, transmission electron microscopy and atomic force microscopy studies of +T and -T HRN-K1-coated Ti revealed a significant change in surface coverage, density and hierarchical organization of the nanotubes upon heating, which was correlated with their ability to promote cell adhesion.

Adsorption↗

PubMed2006

Chemical composition, crystal size and lattice structural changes after incorporation of strontium into biomimetic apatite.

Recently, strontium (Sr) as ranelate compound has become increasingly popular in the treatment of osteoporosis. However, the lattice structure of bone crystal after Sr incorporation is yet to be extensively reported. In this study, we synthesized strontium-substituted hydroxyapatite (Sr-HA) with different Sr content (0.3%, 1.5% and 15% Sr-HA in mole ratio) to simulate bone crystals incorporated with Sr. The changes in chemical composition and lattice structure of apetite after synthetic incorporation of Sr were evaluated to gain insight into bone crystal changes after incorporation of Sr. X-ray diffraction (XRD) patterns revealed that 0.3% and 1.5% Sr-HA exhibited single phase spectrum, which was similar to that of HA. However, 15% Sr-HA induced the incorporation of HPO4(2-) and more CO3(2-), the crystallinity reduced dramatically. Transmission electron microscopy (TEM) images showed that the crystal length and width of 0.3% and 1.5% Sr-HA increased slightly. Meanwhile, the length and width distribution were broadened and the aspect ratio decreased from 10.68+/-4.00 to 7.28+/-2.80. The crystal size and crystallinity of 15% Sr-HA dropped rapidly, which may suggest that the fundamental crystal structure is changed. The findings from this work indicate that current clinical dosage which usually results in Sr incorporation of below 1.5% may not change chemical composition and lattice structure of bone, while it will broaden the bone crystal size distribution and strengthen the bone.

Biocompatible Materials↗

PubMed2006

Biochemical and immunochemical characterization of the antigen-antibody reaction on a non-toxic biomimetic interface immobilized red blood cells of crucian carp and gold nanoparticles.

A special protein assay system based on a highly hydrophilic, non-toxic and conductive biominetic interface has been demonstrated. To fabricate such assay system, red blood cells of crucian carp (RBC) was initially grown on a glassy carbon electrode surface (GCE) deposited nano-sized gold particles (GPs), a second gold nanoparticle layer (NG) was then absorbed on the RBC surface, and finally mammary cancer 15-3 antibody (anti-CA15-3) was attached on the functional RBC surface. A competitive immunoassay format was employed to detect CA15-3 with horseradish peroxidase (HRP)-labeled CA15-3 as tracer and hydrogen peroxide as enzyme substrate. When the immunosensor was incubated into a mixture solution containing HRP-labeled CA15-3 and CA15-3 sample for 1h at 37 degrees C, the amperometric response decreased with the increment of CA15-3 sample concentration. AFM images of the modified layer revealed a uniform distribution of protein and nanogold. In situ QCM and electrochemical measurements demonstrated that the wanted antibody-antigen reactions should occur with high specificity and selectivity. The specific immunoassay system can be developed further to yield sophisticated structures for other proteins.

Animals↗

PubMed2005

Biomimetic oxidation of Hantzsch 1,4-dihydropyridines with tetra-n-butylammonium periodate catalyzed by tetraphenylporphyrinatomanganese(III) chloride [Mn(TPP)Cl].

Efficient oxidation of Hantzsch 1,4-dihydropyridines to their corresponding pyridine derivatives with (Bu(4)N)IO(4) catalyzed by tetraphenylporphyrinatomanganese(III) chloride [Mn(TPP)Cl] is reported. This catalytic system shows high efficiency in the oxidation of 1,4-dihydropyridines at room temperature in the presence of imidazole.

Biomimetics↗

PubMed2005

Biomimetic synthesis and ultrastructural characterization of a zerovalent gold-hydroxyapatite composite.

This manuscript describes one-pot, in situ synthesis of organoapatite-gold nanoparticle composite and its characterization by XRD, energy dispersive X-ray analysis, atomic force, and scanning electron microscopy. This methodology offers a different approach into the synthesis of zerovalent metal-mineral-phase nanocomposites having potential application as osteointegrative ceramics.

Biomimetics↗

PubMed2005

Cyclodextrin retinylidene: a biomimetic kinetic trap model for rhodopsin.

All trans retinal was attached to both the primary face and the secondary face of beta-cyclodextrin via a Schiff base linkage, analogous to that in rhodopsin. The new models were evaluated and compared with n-butylamine retinylidene Schiff base for their rates of hydrolysis, and factors that influence such rates. Competition studies using adamantane carboxylate demonstrated the kinetic trap theory by diminishing the binding of retinal in the cyclodextrin, thereby augmenting the rate of hydrolysis. NMR experiments indicate that the retinylidene is most probably bound in the form of a dimer.

Biomimetics↗

PubMed2004

A 2H solid-state NMR spectroscopic investigation of biomimetic bicelles containing cholesterol and polyunsaturated phosphatidylcholine.

Deuterium solid-state NMR spectroscopy was used to qualitatively study the effects of both 1-palmitoyl-2-linoleoyl-sn-glycero-3-phosphatidylcholine (PLiPC) and cholesterol on magnetically aligned phospholipid bilayers (bicelles) as a function of temperature utilizing the chain-perdeuterated probe 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine (DMPC-d54) in DMPC/dihexanoylPC (DHPC) phospholipid bilayers. The results demonstrate that polyunsaturated PC and cholesterol were successfully incorporated into DMPC/DHPC phospholipid bilayers, leading to a bicelle that will be useful for investigations of eukaryotic membrane protein-lipid interactions. The data indicate that polyunsaturated PC increases membrane fluidity and decreases the minimum magnetic alignment temperature for DMPC/DHPC bicelles. Conversely, the introduction of cholesterol into aligned DMPC/DHPC bilayers decreases fluidity in the membrane and increases the minimum temperature necessary to magnetically align the phospholipid bilayers. Finally, the addition of Tm3+ to magnetically aligned DMPC/DMPC-d54/PLiPC/DHPC bilayers doubles the quadrupolar splittings, indicating that this unique bicelle system can be aligned with the bilayer normal parallel to the static magnetic field.

Biomimetic Materials↗

PubMed2006

Biomimetics of silver nanoparticles by white rot fungus, Phaenerochaete chrysosporium.

Extracellular synthesis of silver nanoparticles by a white rot fungus, Phaenerochaete chrysosporium is reported in this paper. Incubation of P. chrysosporium mycelium with silver nitrate solution produced silver nanoparticles in 24h. These silver nanoparticles were characterized by means of UV-vis spectroscopy, X-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy, and photoluminescence spectroscopy. The synthesized silver nanoparticles absorbed maximum at 470 nm in the visible region. XRD spectrum of the silver nanoparticles confirmed the formation of metallic silver. The SEM characterization of the fungus reacted on the Ag+ indicated that the protein might be responsible for the stabilization of silver nanoparticles. This result was further supported by the TEM examination. Though shape variation was noticed, majority of the nanoparticles were found to be of pyramidal shape as seen under TEM. Photoluminescence spectrum showed a broad emission peak of silver nanoparticles at 423 nm when excited at 350 nm. Apart from eco-friendliness, fungus as bio-manufacturing unit will give us an added advantage in ease of handling when compared to other classes of microorganisms.

Ascomycota↗

PubMed2004

The human ankle during walking: implications for design of biomimetic ankle prostheses.

The non-disabled human ankle joint was examined during walking in an attempt to determine overall system characteristics for use in the design of ankle prostheses. The hypothesis of the study was that the quasi-stiffness of the ankle changes when walking at different walking speeds. The hypothesis was examined using sagittal plane ankle moment versus ankle angle curves from 24 able-bodied subjects walking over a range of speeds. The slopes of the moment versus ankle angle curves (quasi-stiffness) during loading appeared to change as speed was increased and the relationship between the moment and angle during loading became increasingly non-linear. The loading and unloading portions of the moment versus angle curves showed clockwise loops (hysteresis) at self-selected slow speeds that reduced essentially to zero as the speed increased to self-selected normal speeds. Above self-selected normal speeds, the loops started to traverse a counter-clockwise path that increased in area as the speed was increased. These characteristics imply that the human ankle joint could be effectively replaced with a rotational spring and damper for slow to normal walking speeds. However, to mimic the characteristics of the human ankle during walking at fast speeds, an augmented system would be necessary. This notion is supported by the sign of the ankle power at the time of opposite heel contact, which was negative for slow speeds, was near zero at normal speeds, and was positive for fast walking speeds.

Adult↗

PubMed2004

Structural organization of DMPC lipid layers on chemically micropatterned self-assembled monolayers as biomimetic systems.

The growth structure of DMPC lipid layers on hydrophobic and hydrophilic alkylsilane-based self-assembled monolayers adsorbed on silicon has been investigated by means of X-ray reflectometry and atomic force microscopy. Hydrophilic modification of hydrophobically terminated ODS-SAMs has been achieved by dose-controlled irradiation with DUV light. While island formation of small DMPC bilayer islands is observed on hydrophobic SAM surfaces, closed layers of DMPC monolayers are formed on hydrophilic SAM surfaces. Furthermore, DMPC adsorption on chemically micropatterned substrates with alternating hydrophobic/hydrophilic surface properties has been studied by imaging ellipsometry and photoemission microscopy. Indication for at least partial bridging of hydrophobic areas by an adsorbed DMPC monolayer has been found.

Adsorption↗

PubMed2005

Novel biomimetic polymersomes as polymer therapeutics for drug delivery.

Novel amphiphilic diblock copolymers, cholesterol-end-capped poly(2-methacryloyloxyethyl phosphorylcholine) (CMPC), which have poly(2-methacryloyloxyethyl phosphorylcholine) (poly(MPC)) as hydrophilic segment and cholesterol as hydrophobic segment, was specially designed as drug delivery systems. Fluorescence probe technique and transmission electron microscope (TEM) characterizations indicated that this novel amphiphilic copolymer formed micelles structure in water and the critical micelle concentration (CMC) was determined to be 1.57 x 10(-7) mol/l. A commercial obtained polymeric amphiphiles, Cholesterol end capped PEO (CPEO), which had a similar structure with CMPC, was used as a control in the cytotoxicity test. While CPEO showed obvious cytotoxicity, cytotoxicity of this novel amphiphiles was not observed as indicated by cell culture. Anti-cancer drug adriamycin (ADR) was incorporated into the micelles by oil-in-water method. The size of the drug-containing micelles was less than 200 nm, and the size distribution of the drug-containing micelles showed a narrow and monodisperse unimodal pattern. The release rate of ADR from the nanosphere was slow and the release continued over 7 days and the release rate decreased with the increase of molecular weights of the copolymer and the amount of the drug entrapped. These experimental results suggested that the nanoparticles prepared from CMPC block copolymers could be a good candidate for injectable drug delivery carrier.

3T3 Cells↗

PubMed2004

Chromium-containing biomimetic cation triaqua-mu3-oxo-mu-hexapropionatotrichromium(III) inhibits colorectal tumor formation in rats.

The cation [Cr(3)O(propionate)(6)(H(2)O)(3)](+) has recently been found by oral or intravenous administration to increase insulin sensitivity and improve serum lipids in healthy and type 2 diabetic model rats. Serum insulin concentrations and, hence, insulin sensitivity are in part responsible for the relationship between diet and the incidence of colorectal cancer. This strongly suggested that the synthetic cation, which in vitro is able to stimulate insulin receptor tyrosine kinase activity in a fashion similar to the oligopeptide chromodulin, could influence the incidence of colorectal cancer. Consequently, the effects of the cation on the inhibition of colon tumorigenesis induced by 1,2-dimethylhydrazine in male Sprague Dawley rats were examined. Gavage administration of aqueous solutions of the complex (1000 microg Cr/kg body mass daily for 6 months) resulted in significantly decreased colon tumor incidence (P<0.003).

1,2-Dimethylhydrazine↗

PubMed2005

Copper(II) complexes of new biomimetic polydentate amide ligands: a spectroscopic study.

Complexes of Cu(II) with N,N'-bis(3-carboxy-1-oxopropanyl)-1,2-ethylenediamine(C(10)H(16)N(2)O(6),L(1)), N,N'-bis(3-carboxy-1-oxopropanyl)-1,2-phenylenediamine(C(14)H(16)N(2)O(6),L(2)), N,N'-bis(2-carboxy-1-oxophenelenyl)-1,2-phenylenediamine(C(22)H(16)N(2)O(6),L(3)) and N,N'-bis(3-carboxy-1-oxoprop-2-enyl)-1,2-phenylenediamine(C(14)H(12)N(2)O(6),L(4)) have been prepared and characterised by elemental analyses, vibrational spectra, magnetic susceptibility measurements, ligand field spectra, EPR spectra, thermal studies and X-ray diffraction spectra. Vibrational spectra indicate coordination of amide and carboxylate oxygens of the ligands giving a MO(4) square planar chromophore. Ligand field and EPR spectra support square planar geometry around Cu(II). [Cu(L(1))] complex has the maximum activation energy and [Cu(L(3))] complex has the minimum activation energy.

Biomimetic Materials↗

PubMed2004

Synthesis, spectra and biomimetic properties of copper(II)-copper(II) and copper(II)-zinc(II) binuclear complexes with CuN5 chromophores.

X-band electron spin resonance (ESR) and UV-vis spectra of a homobinuclear [(Bipy)2Cu-E-Im-Cu(Bipy)2](BF4)3 and a heterobinuclear [(Bipy)2Cu-E-Im-Zn(Bipy)2](BF4)3 complexes, E-Im=2-ethylimidazolate ion have been described as possible models for superoxide dismutase (SOD). Magnetic moment and ESR spectral measurements of the homobinuclear complex have shown an antiferromagnetic exchange interaction. From pH-dependent ESR and UV-vis spectral measurements studies, these complexes have been found to be stable over 8.5-10.5 pH range. These complexes catalyze the dismutation of superoxide (O2-) at biological pH. All the observations indicate that these complexes act as good possible models for superoxide dismutase.

Anti-Bacterial Agents↗

PubMed2003

Detection and analysis of membrane interactions by a biomimetic colorimetric lipid/polydiacetylene assay.

We describe applications of a colorimetric assay based on supramolecular assemblies of lipid-polydiacetylene vesicles for analysis and screening of membrane interactions of lipophilic enzymes, peptides, and ions and for study of the effects of lipid composition upon membrane properties. The lipid-polymer aggregates undergo visible and quantifiable blue-to-red transitions following interfacial interactions and perturbation by varied biochemical processes. Specifically, we show that the colorimetric assay can be tuned for selective detection of enzymes reacting with different lipid species. The experiments also demonstrate that the lipid/polymer platform facilitates screening of peptide-membrane interactions in multicomponent mixtures. The colorimetric vesicles can incorporate lipid species from different cellular sources facilitating analysis of the contribution of molecular components to membrane properties and lipid interactions.

Acetylene↗