The triggered control of interfacial properties on the nanometer scale holds significant promise for actuation in bio-nanotechnology applications where polymeric actuators may manipulate the transport, separation, and detection of biomolecules. To fabricate patterned, stimulus-responsive polymer brushes we have developed several methods that combine surface initiated polymerization (SIP) with dip-pen nanolithography (DPN). Surface-confined, stimulus-responsive polymer brush nanopatterns were fabricated by amplification of DPN patterned, self-assembled monolayers of 16-mercaptohexadecanoic acid on gold surfaces by SIP of N-isopropylacrylamide (NIPAAm). While free radical polymerization yielded only short polymer brushes (DP<50), atom transfer free radical polymerization (ATRP) produced thick, uniform polymer brushes. For free radical polymerization the thickness of the polymer brush layer is a function of the lateral feature size and the initiator density and is maximal at pattern boundaries.

Highly porous nano-fibrous poly(L-lactic acid) (PLLA) scaffolds were prepared and incubated in a simulated body fluid which resulted in the in situ formation of partially carbonated bone-like apatite. The macroporous interconnected architecture was created with a three-dimensional mold of thermally-bonded paraffin microspheres. PLLA solution was cast over the paraffin mold and was thermally induced to phase separate to form nano-scale fibers that mimic the fibrous structures of type I collagen. To potentially improve the osteoconductivity of these scaffolds, they were incubated in a buffered simulated body fluid at 37°C for certain periods of time to allow for apatite formation. It was seen that over time, the apatite particles increased in size. In addition, the growth of apatite particles on the nano-fibrous scaffolds was compared with the growth of particles on similar porous PLLA scaffolds with a solid-walled (not nano-fibrous) morphology. It was seen that the initial number of particles per unit area and the overall increase in mass of the scaffolds were significantly higher in the nano-fibrous scaffolds than in the solid-walled scaffolds. These novel scaffolds have well-defined architectures at three different size scales: (i) interconnected spherical pores ∼250–400 m in diameter; (ii) fibrous collagen-like matrix with fibers 50–500 nm in diameter; and (iii) carbonated bone-like apatite particles at the nanometer to micrometer scales; the scaffolds may serve as superior support for bone tissue regeneration.

Aggregations, created in 2-component suspension inside the optical trap zone were studied. Particles of porous glass-ceramic of CaO-TiO2-P2O5 composition and 1–50 um size were mixed with BSA molecules in water or with CdSe-TOPO 20 nm particles in toluene. Dynamic aggregations up to 300 um size were created inside the optical trap. These aggregations in comparison with one-component aggregations have a 30% higher growth rate. This effect could be explained by the stronger bonding of the protein molecules and CdSe-TOPO particles inside the glass-ceramic particle aggregations. Micro-Raman spectra, taken from dynamic and stable permanent aggregations show several new peaks, possibly associated with creation of chemical bonds.

Our system is the electrochemical approaches include the detection of hybridization from nonlabeling nucleic acids to protein-bound nucleic acids using soluble mediators with K4Fe(CN)6 solutions. In order to generate bio-functional surfaces, the streptavidin(SAv)-biotin system is used. A 50 % change of redox peak current after hybridization measured with 50 μM concentration of target DNA. We suggest that this result comes from the efficient electron transport through the SAv-biotin interaction. Our electrochemical detection system showed good reproducibility on a chip with non-labeling DNA hybridization detection.

The spherical protein ferritin can be used as a generic reaction vessel for the production of a variety of materials, such as iron and manganese oxides. Here, its use for the aqueous production of nanoparticles of equiatomically alloyed CoPt is demonstrated. These have been considered for ultrahigh density magnetic recording as well as permanent magnetic materials. This monodisperse protein strictly regulates the maximum diameter of nanocrystals synthesized within its 8 nm diameter cavity. As a consequence of its external uniformity, it decouples the formation of highly regular self-patterned films from any size distribution associated with the synthesized material. Further, its 2 nm-thick protein coating discourages sintering of particles at temperatures required for the transformation to the L10 phase required for magnetic recording applications.

Electrospinning for the formation of nanoscale diameter fibers has been explored for high performance filters and biomaterial scaffolds for vascular grafts or wound dressings. Fibers with nanoscale diameters provide benefits due to high surface area. In this study we used electrospinning for protein-based biomaterials to fabricate scaffolds from aqueous regenerated silkworm silk, Bombyx mori,. Adhesion, spreading and proliferation of human bone marrow stem cells (hBMSCs) on electrospun silk was characterized. Scanning electron microscopy (SEM) and MTT analyses demonstrated that the electrospun silk matrices promoted hBMSC attachment and proliferation over 10 days in culture. The responses of the hBMSCs on the electrospun silk matrices, combined with the biocompatibile properties of the silk fibroin protein matrix, suggest potential for use of this biomaterial as scaffolds for tissue engineering.

Inspired by biological systems, in which damage triggers an autonomous healing response, a polymer composite material that can heal itself when cracked has been developed. The material consists of an epoxy matrix composite, which utilizes embedded microcapsules to store a healing agent and an embedded catalyst. This paper investigates issues of fracture and fatigue consequential to the development and optimization of this new class of materials. When damage occurs, the propagating crack ruptures the microcapsules, which releases healing agent into the crack plane. Polymerization of the healing agent is triggered by contact with exposed catalyst, which bonds the crack faces closed. The efficiency of crack healing is defined as the ability of a healed sample to recover fracture toughness. Healing efficiencies of over 90% have been achieved. Embedded microcapsules significantly increase the fracture toughness and reduce the fatigue crack propagation rate of epoxy. Fracture mechanisms for neat epoxy and epoxy with embedded microcapsules are presented.

In this paper we report on the synthesis in solution of cobalt nanoparticles, nanorods and nanowires achieved through the decomposition of an organometallic precursor Co(η3-C8H13)(η4-C8H12) and stabilized by carboxylic acid / amine based mixtures. Through decomposition of the precursor in the presence of a 1/1 mixture of oleylamine / oleic acid during 3 hours, the formation of 3 nm spherical nanoparticles is observed while hcp-cobalt nanorods are obtained if the reaction is pursued for 48 hours. Increasing the amount of oleic acid to 2 equivalents with respect to the amine results in the formation of hcp-cobalt nanowires, micrometers in length and 6 nm mean diameter‥ By using amines with various chain lengths we have observed a modification of the aspect ratio of the cobalt nanorods1. For example, the decomposition of Co(η3-C8H13)(η4-C8H12) in the presence of octadecyl-, hexadecyl-, dodecyl- and octylamine in association with oleic acid allows to selectively produce nanorods of varying aspect ratio.

Physical characterization using TEM and HRTEM, shows that the nanoparticles, nanorods and nanowires are all hcp single crystals. The magnetic properties reveal a saturation magnetization similar to that of bulk and a ferromagnetic behavior at room temperature for the nanorods and nanowires while the 3 nm nanoparticles remain super-paramagnetic.

PET has been widely used for medical materials such as an artificial ligament. However, the affinity of tissues is no good. To compensate this, the mesh formed PET has clinically been used for artificial ligament intruding tissue into mesh. However, this method has not shown sufficient affinity with the tissue; that is, the initial adapting strength of the material and tissue is weak. · The artificial ligament must be biocompatible to contact blood and tissue. The foregoing artificial ligament, however, doesn't satisfy the biocompatibility. ·

Thus, we have modified the PET surface into hydrophilic by substituting NH2 or OH functional groups. Firstly, an ArF excimer laser light was irradiated the PET with water on top. The OH functional group was substituted on the PET surface by this photochemical reaction. Secondly, the ArF excimer laser light was irradiated the PET in ammonia gas ambient. In this photochemical reaction, the NH2 functional group was substituted on the PET surface.

· In this study, the untreated sample had the contact angle with water of 80 degrees and the bonding strength with protein of only 1.0kg/cm2. The contact angle of the modified sample improved to 40 degrees and the bonding strength, to 23kg/cm2. When treated in ammonia gas, the contact angle also improved to 40 degrees; however, the bonding strength was almost the same as that of the untreated sample.

It was confirmed that the affinity of the PET for water and protein could be controlled by increasing or decreasing the substitution concentration of OH and NH2 functional groups on the surface.

A nanoparticulate-hydroxyapatite filler augmented osteointegration within a resorbable polymer based bone graft substitute designed for orthopaedic and periodontal applications. The unsaturated polyester poly(propylene glycol-co-fumaric acid) (PPF), was used to prepare the bone graft substitute. The nanoparticulate-hydroxyapatite filler was examined in terms of biocompatibility, bony ingrowth and mechanical stability in a rat calvarial defect model. The nano-hydroxyapatite fillerwas compared against a commercially available micrometer-sized hydroxyapatite(HA) filler. Histological analysis indicated that remodeling of the newly formed bone was more advanced in the defect filled with the nano-hydroxyapatite augmented PPF. Mechanical evaluation showed a more rapid increase in stiffness of the nano-hydroxyapatite PPF. Implants of the nano-HA augmented PPF showed more advanced bone formation and recovery of mechanical properties, suggesting an improved biological response to the nano-sized particles.

The wide majority of biological fibrous composites exhibit twisted plywood architectures (planar or cylindrical) for mechanical reasons [1–5]. These supramolecular organizations originate from the passage of the extracellular matrix (surrounding the chiral fibrous molecules) trough a lyotropic cholesteric liquid crystalline mesophase during the structure formation process [1–5]. In this work, we used the well-established Landau-de Gennes theory of liquid crystals in order to develop a fundamental understanding of the supramolecular self-assembly process leading to the planar monodomain (defect-free) twisted plywood architecture [6]. Simulations illustrate the importance of constraining surface in the formation of defect-free (mechanically effective) composites. These results provide a better understanding of tissue morphogenesis which is highly desirable for the development of new bio-inspired synthetic composites.

Protein patterning techniques are crucial for the development of antibody-based biosensor and the study of controlled cell growth. This paper discusses a protein patterning technique based on microelectronic fabrication, DNA hybridization and biotin-streptavidin pair. A gold-on-silicon-dioxide substrate with micron size pattern was fabricated with photolithography and lift-off process. The average surface roughness of the gold pattern is 4.3 nm, measured by contact mode AFM. Thiol derivatized single stranded DNA was attached to the gold pattern surface by the chemical bonding between gold atom and sulfur atom. Surface attached DNA was then hybridized with a biotin conjugated complementary DNA sequence. Thus, the gold pattern was translated into a biotin pattern with similar resolution. Fluorescein conjugated streptavidin was patterned as demonstration. Fluorescence microscopy shows relative uniform streptavidin coverage of micron resolution and low background non-specific binding. The proposed protein patterning technique takes advantage of the high resolution of modern microelectronic fabrication. It has the potential of reaching sub-micron resolution. The biotin-streptavidin pair provides extremely specific and stable linking for protein immobilization. To show its application in biological inspired self-assembly, this technique was used successfully in the self-assembly of 20 nm streptavidin conjugated gold particles.

In this work we report first results on a direct deposition of 2–4nm gold nanoparticles onto DNA strands. In a two step protocol first cis-Pt (cis-diamminedichloroplatinum(II), cis-Pt(NH3)2Cl2) is intercalated into a DNA duplex. In a second step cysteamine stabilized gold nanoparticles are immobilized on DNA due to a ligand exchange (NH3 vs. NH2-R) at the Pt center which was done in solution as well as on surface bound oligonucleotides. The DNA-nanoparticle assemblies are prepared on mica and silicon and are imaged by AFM.

The central part of polymethylmethacrylate (PMMA) lens was modified to be hydrophobic and the peripheral part, to be hydrophilic by photochemical reaction with ArF excimer laser and chemicals. PMMA has a high–transmittance property in the visible light and has been used as an intraocular lens. However, protein and fat are stuck onto the lens surface after a long-term insertion, which makes the surface get opaque; that is the after-cataract.

Accordingly, the central part of the lens was modified to be hydrophobic in order to protect the PMMA lens from fat and protein. And, the peripheral part was modified to be hydrophilic to develop an affinity for the tissue. Firstly, the central part of the lens was irradiated with ArF laser (147kcal/mol) in the presence of fluorine oil (perfluoropolyether) or CFn gas ambience. By this photochemical reaction, the CF3 functional group was substituted on the PMMA surface. Secondly, the peripheral part of the lens was irradiated with ArF laser (147kcal/mol) in the presence of water. By this photochemical reaction, the OH functional group was substituted on the PMMA.

The contact angle with the physiological salt solution was measured. The contact angle of the non-treatment sample was 83 degrees. The one treated with perfluoropolyether was 117 degrees at the laser shot number of 5000 and the laser fluence of 25 mJ/cm2. When using CBrF3 and CClF 3, the contact angles were both 91 degrees at the laser shot number of 5 and the laser fluence of 20 mJ/cm2. And, the one using the water was 14 degrees, less than the contact angle of the non-treatment sample.

It was confirmed that the exposure part of the PMMA surface with the laser was modified into hydrophobic or hydrophilic by the existence of oil and water. In conclusion, our study successfully demonstrated the production of the ideal intraocular lens.

Tissue losses and organ failures resulting from injuries or diseases remain frequent and serious health problems despite great advances in medical technologies. Transplantation and reconstructive surgeries are seriously challenged by donor tissue shortage. We take a tissue engineering approach to design 3D scaffolds for cells to grow and synthesize new tissues. The scaffolds are biodegradable and will be absorbed after fulfilling the purpose as 3D templates, leaving nothing foreign in the body. To better mimic natural bone structurally, mechanically and biologically, nano-sized hydroxyapatite particles (N-HAP) were formulated with biodegradable poly(α-hydroxyl acids) to form composite scaffolds with well-controlled pore structures using thermally induced phase separation (TIPS) in this work. The pore structure and mechanical properties of the scaffolds were optimized by the use of multiple solvent systems, different quenching rates and quenching depths. The fabricated scaffolds possessed porosities higher than 90% and average pore sizes ranging from 50 to 500 μm. The scaffolds containing N-HAP maintained open and regular 3D pore structure similar to those of plain polymer scaffolds, implying that N-HAP particles were dispersed within the polymer pore walls of the scaffolds. The addition of N-HAP increased the compressive modulus by 20∼80% over that of plain polymer scaffolds. These results indicate that poly(α-hydroxyl acids)/N-HAP scaffolds may provide excellent 3D substrates for bone tissue engineering.

Motivated by the SERS (Surface Enhanced Raman Spectroscopy) sensitivity to very small amounts of material we are interested in the application of the SERS technique for studying complex biological systems, such as cells.

Using nanometer-sized Ag particles deposited on GaAs surfaces as SERS-active substrate we have observed an enhancement of Raman signal from human spermatozoa. We have obtained structural information on extremely small amounts of biomaterials and at the same time evidence that the bio-systems are preserved on the surface.

In our opinion, this kind of SERS-active substrates with nanometer-sized Ag particles on semiconductors might have promising application in nanoscale science and technology. In fact bio-molecules, cells and processes of their interfacing with Si, GaAs, silver and gold and other inorganic substrates, form the basis of bio-electronics a new emerging field at the crossing of molecular biology and nano-electronics with numerous electronic and biotechnological applications.

Using gel electrophoresis we demonstrate the attachment of short ssDNAs to a new type of water-soluble gold nanocluster that is encapsulated with ethylene oxide ligands. Initial experiments indicate that these DNA/nanocluster conjugates can subsequently be hybridized to a longer DNA template suggesting a pathway for nanofabrication of multi-cluster assemblies.

Phase separation into controllable patterned microstructures was observed for Bombyx mori silkworm silk and poly(ethylene oxide) (PEO) (900,000 g/mol) blends cast from aqueous solution. Solution blending was used to incorporate water-soluble PEO into silk to enhance elasticity and hydrophilicity. The sizes of the globule fibroin phase ranged from 3.1±0.9 μm to 18.2±2.1 μm depending on the ratio of silk/PEO. Optical microscopy and SEM analysis confirmed the micro-phase separation between PEO and silk. Surface properties were determined by contact angle. The PEO can be easily extracted from the films with water to generate silk matrices with definable porosity and enhanced surface roughness. These blend films formed from two biocompatible polymers provide new potential tissue engineering scaffolds and controlled release drug delivery materials.

Experiments have shown that ordered monolayers of large organic molecules can control crystal nucleation and growth. The work of nucleation controls which morphology and phase will appear. We have used molecular dynamics to simulate the interfaces between stearic acid and a number of calcium carbonate surfaces. An important issue is the ionisation state of the acid which depends on the pH of the solution at the surface. We estimate this by solving the nonlinear Grahame equation for a calcium carbonate solution. The species in solution are chosen from geochemical models. The calculated interfacial binding energy between monolayer and material is often of the order of 1 Jm-2, suggesting that the nucleation rate is strongly enhanced.

Hydroxyapatite (HA) is a bone-like ceramic with good cytocompatibility properties and, consequently, has been used as coatings for dental and orthopedic implants. However, the main limitation of using HA as a coating material is its high calcium dissolution rate. The present study investigated an assortment of dopants in order to lower the calcium dissolution rate of HA. The HA dopants used in the present study were divalent (magnesium and zinc) and trivalent (yttrium, lanthanum, indium, and bismuth) cations. In a 21 day study, undoped HA and HA doped with magnesium (Mg), lanthanum (La), and bismuth (Bi) were found to increase in mass while formulations doped with zinc (Zn), indium (In), and yttrium (Y) were found to decrease in mass. Decreased mass may be due to loss of a number of chemical groups (such as calcium, phosphorous, and hydroxyl groups). Studies were also performed to specifically evaluate calcium dissolution. The divalent and trivalent-doped HA averaged samples had calcium concentrations in the supernatant consistently below the undoped HA samples suggesting lower calcium dissolution rate for all doped formulations. The results of the present study demonstrated that of those dopants tested that increased in mass, HA doped with Bi had the lowest amount of calcium released into the supernatant media. Since calcium has been shown to increase adsorption of proteins important for new bone growth, the present study provided evidence that to decrease the calcium dissolution rate of HA, dopants should be used, particularly Bi.