Synthesis of α,ω-allyl-terminated telechelic macromonomers based on poly(tert-butyl methacrylate) (poly(t-BMA)) and poly(methacrylic acid) (poly(MAA)) was studied with the aim of preparing end-linked gels and hydrogels. Low molecular weight α-allyl-terminated poly(t-BMA) macromonomers with narrow polydispersities (Mw/Mn = 1.16) were synthesized via controlled atom transfer radical polymerization (ATRP) using a Cu(I)Br/N,N,N',N',N',N'-hexamethyltriethylenetetraamine catalyst system in conjunction with an allyl-2-bromoisobutyrate as the functional initiator. The polymerizations exhibited a linear increase of molecular weight in direct proportion to the monomer conversion and first-order kinetics with respect to monomer concentration. No significant difference was found between using polar or non-polar solvents (tetrahydrofuran or benzene, respectively). Optimization of reaction conditions to obtain the highest degree of active terminal bromine is discussed. Quenching the ATRP reaction with allyltributyltin yielded α,ω-allyl-terminated poly(t-BMA) macromonomers by replacing the terminal bromine with ω-allyl functional group. Poly(MAA) macromonomers were prepared by deprotection of the tert-butyl group from α,ω-allyl-terminated poly(t-BMA) macromonomers using concentrated trifluoroacetic acid at room temperature. Successful synthetic steps were confirmed by 1H NMR, FT-IR and MALDI-TOF MS analyses. The α,ω-allyl-terminated macromonomers were proven to be candidates for further polymerization by forming end-linked, non-soluble gels.

The fabrication of micron-scale channels and reaction chambers using micromachining techniques has created devices with large surface to volume ratios. As a result, surface properties play a major role in determining the behavior of micromachined devices. In this work, we present strategies that can be used to reconfigure surfaces from hydrophobic to hydrophilic or from hydrophilic to hydrophobic. The reversible nature of the surface is made possible by using deposition and removal of biomolecules or amphiphiles on self-assembled monolayers (SAMs). When the initial surface was hydrophobic (using a CH3-terminated SAM on the surface, water contact angle ∼100), it was rendered hydrophilic (water contact angle ≤60°) using monolayer adsorption of avidin protein. To retrieve the hydrophobicity, the avidin was subsequently removed using non-ionic surfactant octyl-β-D-glucopyranoside. Moreover, by incorporating a biotinylated poly(ethyleneglycol), the avidin-coated surface was resistant to further non-specific adsorption. If the initial surface was hydrophilic (using a CO2H-terminated SAM on the surface, water contact angle ≤20°), it was rendered hydrophobic (water contact angle >90°) using monolayer amphiphilic octadecylamine adsorption. The hydrophilicity was restored after subsequently removing the amphiphile using anionic surfactant sodium lauryl sulfate. Both types of surfaces showed excellent reversibility and demonstrated the ability to control surface wettability.

Apatite-wollastonite (A-W)/high-density polyethylene composite (AWPEX) materials have been designed to match the mechanical strength of human cortical bone and to provide favorable bioactivity, with potential use in many orthopaedic applications. To better understand AWPEX properties, the effects of surface finish and ceramic filler size and content on osteoblast-like cell attachment, proliferation, and differentiation were examined. Glass ceramic content was tested at 30 and 50 vol% and median particle size at 4.5 and 7.7 μm. Samples were prepared as 10 × 10 × 1 mm3 tiles with polished or roughened surfaces, sterilized by gamma irradiation (2.5 Mrad), and characterized by SEM, surface energy, and surface profilometry. Saos-2 human osteoblastlike cells were cultured on each surface at an initial concentration of 4500 cells/cm2 in McCoy's medium and incubated at 37C in a humidified atmosphere with 5% CO2 for 1, 3, or 7 days. At each time point, adenosine triphosphate (ATP) and alkaline phosphatase (ALP) levels were measured to assess cell number and osteoblast differentiation. Significant differences were found at 7 days, confirmed by ANOVA post-hoc testing using Bonferroni's correction. Overall, increased exposure of the A-W phase in AWPEX through surface polishing, higher volume fraction, and/or larger particle size, was found to lead to an improved cell response.

The susceptibility of phosphatidylcholine liposomes to rupture by ultrasound was investigated. The liposomes were treated with (or had incorporated) a surface active dopant. The dopants studied here all contain polymers or oligomers of ethylene glycol as their hydrophilic “headgroup” component. All dopants strongly increased the ultrasonic permeabilizability of liposomes, as measured by the rate of release of a self-quenching fluorescent dye, at concentrations that caused no increase in permeability in the absence of ultrasound. The surface active dopants reached maximal effectiveness at about 1% of their critical micelle concentrations (CMCs). Using the roughly inverse relationship between CMC and membrane partition coefficient, we estimate that these maximally effective concentrations correspond approximately to the onset of headgroup contact among the surfactants in the membrane. Two surfactants, a PEG-lipid and a Pluronic triblock polymer, can be irreversibly incorporated into liposomes to give formulations that could in principle be used as drug delivery vehicles. The Pluronic polymer offers the possibility of additional temperature responsivity, owing to its highly temperaturedependent CMC.

HAPEXTM (40 vol% hydroxyapatite in a high-density polyethylene matrix) and AWPEX (40 vol% apatite-wollastonite glass ceramic in a high density polyethylene matrix) are composites designed to provide bioactivity and to match the mechanical properties of human cortical bone. HAPEXTM has had clinical success in middle ear and orbital implants, and there is great potential for further orthopaedic applications of these materials. However, more detailed in vitro investigations must be performed to better understand the biological interactions of the composites and so the bioactivity of each material was assessed in this study. Specifically, the effects of controlled surface topography and ceramic filler composition on apatite layer formation in acellular simulated body fluid (SBF) with ion concentration similar to those of human blood plasma were examined. Samples were prepared as 1 cm × 1 cm × 1 mm tiles with polished, roughened, or parallel-grooved surface finishes, and were incubated in 20 ml of SBF at 36.5 °C for 1, 3, 7, or 14 days. The formation of a biologically active apatite layer on the composite surface after immersion was demonstrated by thin-film x-ray diffraction (TF-XRD), environmental scanning electron microscopy (ESEM) imaging and energy dispersive x-ray (EDX) analysis. Variations in sample weight and solution pH over the period of incubation were also recorded. Significant differences were found between the two materials tested, with greater bioactivity in AWPEX than HAPEXTM overall. Results also indicate that within each material the surface topography is highly important, with rougher samples correlated to earlier apatite formation.

We report on the structural properties of siliceous spicules, found in the hexactinellid sponge Euplectella. Selective chemical etching of Euplectella spicules in bleach reveals the presence of a striated arrangement of silica spheres (∼50-200 nm in diameter) placed radially around a central, high-organic content cylindrical region. Complementary etching experiments with HF indicate a graded variation of silica content in these shells. The presence of such a multi-layered and variable-composition structure affords these spicules not only with enhanced structural integrity but could also be reflected in their optical properties. Qualitative, index-matched, refractive index measurements are shown to support this expectation.

Colloidal quantum dots (QDs) exhibit unique optical and electronic properties due to their physical size and the semi-conductor material from which they are made [1,2]. While the isolated properties of these nanoparticles offer a number of potential applications, such as bioimaging, their future use in novel electronic devices will require large arrays of known order. The assembling of these arrays is non-trivial and requires a monodisperse sample of quantum dots in order to facilitate the self-assembling process [3,4]. We propose first to validate the concept of using natural and/or recombined (genetic engineered) proteins to build stable, water soluble QD-protein conjugates [5]. Eventually, strategies to design these structures with highly controlled patterns will emerge.

We report a method using vesicle fusion techniques that result in long-standing hydrophilic and protein-resistant PDMS surfaces. The PDMS was oxidized in plasma followed by treatment with various concentrations of phospholipid vesicles to form planar bilayer membranes in the microchannels. Contact angle measurements showed that a freshly oxidized hydrophilic surface began hydrophobic recovery immediately, but PC (phosphatidylcholine) treated surfaces exhibited prolonged hydrophilic properties up to two hours after bilayer modification, and cationic DOPC+ treated surfaces had a contact angle of ∼70. FRAP experiments confirmed fusion of vesicles to form bilayers with lateral mobility. Protein adsorption studies in microchannels showed 2-3 orders of magnitude decrease in fluorescence from non-specific adsorption of dye-conjugated avidin and BSA. Coulombic interaction was found to play an important role in determining the amount of non-specific adsorption. Dehydration of the membranes resulted in increased protein adsorption after rehydration for PC but not for the synthetic lipid DOPC+, which has a positively charged headgroup.

Since the cytocompatibility of carbon nanofibers with respect to neural applications remains largely uninvestigated, the objective of the present in vitro study was to determine cytocompatibility properties of formulations containing carbon nanofibers. Carbon fiber substrates were prepared from four different types of carbon fibers, two with nanoscale diameters (nanophase, or less than or equal to 100 nm) and two with conventional diameters (or greater than 200 nm). Within these two categories, both a high and a low surface energy fiber were investigated and tested. Astrocytes (glial scar tissue-forming cells) and pheochromocytoma cells (PC-12; neuronal-like cells) were seeded separately onto the substrates. Results provided the first evidence that astrocytes preferentially adhered on the carbon fiber that had the largest diameter and the lowest surface energy. PC-12 cells exhibited the most neurites on the carbon fiber with nanodimensions and low surface energy. These results may indicate that PC-12 cells prefer nanoscale carbon fibers while astrocytes prefer conventional scale fibers. A composite was formed from poly-carbonate urethane and the 60 nm carbon fiber. Composite substrates were thus formed using different weight percentages of this fiber in the polymer matrix. Increased astrocyte adherence and PC-12 neurite density corresponded to decreasing amounts of the carbon nanofibers in the poly-carbonate urethane matrices. Controlling carbon fiber diameter may be an approach for increasing implant contact with neurons and decreasing scar tissue formation.

A novel supported bilayer membrane was formed on top of a hydrophobic spacer layer of hexyl thioctate (HT) and its application in the detection of pore forming toxins was demonstrated. The formation kinetics, effect of different flow rates on the fusion process of vesicles and perforation by incubation with streptolysin O (SLO) and pristine membranes were investigated. Individual layers of the multilayer structure were successfully characterized with surface plasmon resonance (SPR), and the resulting spectra were analyzed in order to determine the layer thickness and other membrane properties. The interaction of SLO with the pristine biomimetic membrane resulted in a pronounced change in the reflectivity spectrum. Elements of these spectral changes were analyzed to explain the process of toxin binding and pore formation taking place on the lipid membrane.

Microparticles (32-53 μm) of cross-linked poly-β-Cyclodextrin (PCD) having a bifunctional hexyl spacer were prepared. PCD served as an insoluble robust matrix, which is chemically inert in acidic and basic media while preserving accessibility of pesticide methyl parathion (MPT) and its hydrolysis product p-nitrophenol (p-NP) to cyclodextrin cavities. The multi-utility of PCD was demonstrated as a stable biomaterial for adsorption of MPT and p-NP through inclusion phenomena and as a single unit system suitable for casting alternate enzyme/polyelectrolyte multilayers.

γ-Fe2O3@Au core-shell nanoparticles were prepared through a combined route, in which high temperature organic solution synthesis and colloidal microemulsion techniques were successively applied. High magnification of TEM reveals the core-shell structure. The presence of Au on the surface of as-prepared particles is also confirmed by UV-Vis absorption. The magnetic core-shell nanoparticles offer a promising application in bio- and medical systems.

Carbon nanofibers possess excellent conductivity properties, which may be beneficial in the design of more effective neural prostheses, however, limited evidence on their cytocompatibility properties exists. The objective of the present in vitro study was to determine cytocompatibility and material properties of formulations containing carbon nanofibers to predict the gliotic scar tissue response. Poly-carbonate urethane was combined with carbon nanofibers in varying weight percentages to provide a supportive matrix with beneficial bulk electrical and mechanical properties. The substrates were tested for mechanical properties and conductivity. Astrocytes (glial scar tissue-forming cells) were seeded onto the substrates for adhesion. Results provided the first evidence that astrocytes preferentially adhered to the composite material that contained the lowest weight percentage of carbon nanofibers. Positive interactions with neurons, and, at the same time, limited astrocyte functions leading to decreased gliotic scar tissue formation are essential for increased neuronal implant efficacy.

Bacterio-rhodopsin purple membrane (PM) thin films have been prepared by selfassembling (SA) technique. Morphological properties of the layers were inspected by Scanning Electron Microscopy (SEM) and Scanning Force Microscopy (SFM) highlighting the presence of densely packed PM films. Reflectance Uv-vis spectra on these films revealed the typical bR absorption at 570 nm. By using a tungsten lamp illuminations (250-350 mW) chopped at 0.5Hz, photoelectric responses were detected. Differential (light-on and light-off) photocurrent signals of up to 1 μA/cm2 were obtained upon light exposure.

Thin films of calcium carbonate were deposited on the surfaces of synthetic substrates using a simple biomimetic pathway. The Nylon 66 fiber knit pre-adsorbed with acidic polymers was used as a template for the controlled deposition of CaCO3 thin film. The presence of the soluble macromolecules on the fiber knit surface was characterized using ATR-FTIR spectroscopy. The characterization of the mineral films was carried out using scanning electron microscope (SEM), X-ray diffraction (XRD) and energy dispersive Xray scattering (EDX) studies.

Regenerative medicine is the science of design and manufacture of parts for functional restoration of damaged tissues due to cancer, disease and trauma. Morphogenesis is the developmental cascade of pattern formation, body plan establishment and differentiation of tissues culminating in adult form. Regeneration in general, recapitulates in parts, embryonic morphogenesis. Thus, the principles of morphogenesis can be applied to tissue engineering for regenerative medicine and surgery. The threekey ingredients for tissue engineering and regenerative medicine are inductive morphogens, responding stem cells, and extracellular matrix materials. Therefore bioactive morphogens can be integrated into materials for functional restoration by tissue engineering. A morphogen is a morphogenetic protein signal that acts on responding stem cells. Bone morphogenesis is induced by bone morphogenetic proteins (BMPs). BMPs play a role in pattern formation, cell differentiation, maintenance and regeneration of tissues. BMPs are pleiotropic and act on chemotaxis, mitosis and differentiation of progenitor stem cells. There are nearly twenty BMPs in the human genome. BMPs have actions beyond bone in development of teeth, heart, kidney, eye, skin, and brain. Thus, BMPs may be called body morphogenetic proteins. Stem cells are primordial cells with unlimited replicative potential and can be programmed by morphogens such as BMPs. Extracellular matrix is the native scaffolding material that can be used to deliver morphogens such as BMPs for tissue engineering of bone. Biomimetic materials are typically synthetic, polymeric structures that mimic extracellular matrix scaffolding by presenting the cellular binding sites found within collagens, fibronectin, proteoglycans and glycoproteins. Materials that mimic extracellular matrix scaffolding such as BMPs bind to collagens I&IV, heparan sulfate and heparin. BMPs bound to collagen acts as a composite biomaterial to initiate bone formation and the shape can be molded by an appropriate template. In addition to including BMPs in a carrier matrix, the geometry of the carrier matrix is critical for optimal tissue engineering. For example: collagen particles smaller than 44μm are feeble in bone induction compared to the coarse (420μm) particles. Gene therapy approaches using genes for morphogenesis such as BMPs allows a sustained, prolonged secretion of gene products. Thus, morphogens integrated into biomaterials may be useful in regenerative medicine.

The use of electrostatic forces to shape materials processed from solution provides exciting opportunities to enhance material properties by creating new structures and morphologies during processing. In this context we report the formation of nanoscale webs composed of interconnected electrospun polymer fibrils. These nanowebs have been formed from synthetic spider silk, collagen, and denatured collagen when they are electrospun from various concentrations of formic acid. These nanowebs have been characterized by field emission scanning electron microscopy (FESEM) in order to characterize their morphology and measure their surface areas.

The research presented here aims to mimic the highly specialized local environment of the retina and to exploit the principles that govern its function, in order to construct functional optical interfaces that can be used as biotransducers. In the retina, a chromophore isomerizes and the protein to which it binds changes shape. In this proof-of-concept experiment we engineer an artificial surface to mimic the physiochemical environment of the retina and the key reaction of the visual cycle. We immobilized small peptides on silicon and assessed changes in their surface properties upon chromophore binding via AFM. Our observations suggest that when binding occurs it is accompanied by conformational changes of the surface-anchored peptide.

The present study demonstrated for the first time desirable cytocompatibility properties of carbon nanofibers pertinent for bone prosthetic applications. Specifically, osteoblast (boneforming cells), fibroblast (cells contributing to callus formation and fibrous encapsulation events that result in implant loosening), chondrocyte (cartilage-forming cells), and smooth muscle cell (for comparison purposes) adhesion were determined on carbon nanofibers in the present in vitro study. Results provided evidence that nanometer dimension carbon fibers promoted select osteoblast adhesion, in contrast to the performance of conventional carbon fibers. Moreover, adhesion of other cells was not influenced by carbon fiber dimensions. To determine properties that selectively enhanced osteoblast adhesion, similar cell adhesion assays were performed on poly-lactic-co-glycolic (PLGA) casts of carbon fiber compacts previously tested. Compared to PLGA casts of conventional carbon fibers, results provided the first evidence of enhanced select osteoblast adhesion on PLGA casts of nanophase carbon fibers. The summation of these results demonstrate that due to a high degree of nanometer surface roughness, carbon fibers and PLGA with nanometer surface dimensions may be optimal materials to selectively increase osteoblast adhesion necessary for successful orthopedic implant applications.

Elastic protein-based polymers comprised of repeating pentapeptide sequences, (GXGXP)n, exhibit mechanical resonances that have been observed to date with frequency maxima near 5 MHz and 3 kHz. Because the 3 kHz resonance is in the middle of the acoustic frequency range, the purpose here is to substantiate the relevance of the 3 kHz resonance to acoustic absorption and to demonstrate means of improving mechanical properties for the sound absorption application. Previously reported loss factor data in the 100 Hz to 10 kHz range is substantiated by relevant but distinctly different measurements of loss shear modulus and loss permittivity. Furthermore cross-linking approaches are reported that result in increased elastic moduli by an order of magnitude to 4 × 106 Pa at 20% strain and increased break stress by two orders of magnitude to 1.3 × 107 Pa while exhibiting break stain values of several hundred per cent.