OTS自组装单层膜诱导定向生长SrTiO3功能陶瓷薄膜

采用自组装单层膜技术,以三氯十八烷基硅烷(octadecyl-trichioro-silane,OTS)为模版,在玻璃基片上成功制备了钛酸锶晶态薄膜.改性基板的亲水性测定与金相显微镜测试表明,紫外光照射使基板由疏水转变为亲水,OTS单分子膜对薄膜的沉积具有诱导作用:X射线衍射(XRD)与扫描电镜(SEM)表征显示,制备成功的钛酸锶薄膜结晶良好,样品表面均匀,在垂直基板表面方向上呈花状生长:EDS能谱测试为钛酸锶薄膜的化学组成提供了有力的证据;同时探讨了白组装单层膜和钛酸锶薄膜的形成机理.     

Growth kinetics and morphology of self-assembled monolayers formed by contact printing 7-octenyltrichlorosilane and octadecyltrichlorosilane on Si(100) wafers

The growth kinetics and morphologies of self-assembled monolayers deposited by contact printing 7-octenyltrichlorosilane (OCT) and octadecyltrichlorosilane (OTS) on Si(100) were studied by ellipsometry and atomic force microscopy. We found that, for both OCT and OTS, full monolayers could be obtained at room temperature after printing times of 120-180 s; the printing-based monolayer assembly processes follow apparent Langmuir adsorption kinetics, with the measured film growth rates increasing both with the ambient humidity and with concentration of the ink used to load the stamp. At a dew point of 10 degrees C and an ink concentration (in toluene) of 50 mM, the observed film growth rate constant is 0.05 s(-)(1). When the printing was carried out at a lower ambient humidity (dew points of 1-3 degrees C), the measured rates of assembly were approximately a factor of 2 slower. Increasing the deposition temperature from 25 to 45 degrees C under these conditions increased the film growth rate only slightly. The morphology of the films depends on the identity of the ink. Uniform, high-coverage films could be obtained readily from the eight-carbon chain length adsorbate OCT, provided that the stamp was not overloaded with the ink; for high concentrations outside of the optimal range, the surface presented significant numbers of adsorbed particles ascribed, in part, to siloxane polymers formed by hydrolysis of the ink on the stamp before printing. In marked contrast, for the 18-carbon adsorbate OTS, the printed films always consisted of a mixture of a uniform monolayer plus adsorbed polysiloxane particles. The different film morphologies seen for OCT and OTS are proposed to result from the different transfer efficiencies of the organotrichlorosilane relative to polysiloxane hydrolysis products formed during the printing process. These transfer efficiencies exhibit sensitivities related to the permeation of the poly(dimethylsiloxane) (PDMS) stamp by the silane reagents. Short-chain inks such as OCT evidently permeate the PDMS stamp more deeply than longer-chain inks such as OTS. This difference, and the different diffusion rates of ink vs oligomeric silane hydrolysis products, determines the film morphology obtained by contact printing. The mass transfer dynamics of the process thus yield surface layers derived from varying quantities of siloxane oligomers, which subsequently transfer to the substrate along with unhydrolyzed silane adsorbate during the printing step. The structural evolution of the contact-printed films so obtained is strikingly different from that of SAMs prepared by immersion.     

Preparation of hybrid soda-lime/quartz glass chips with wettability-patterned channels for manipulation of flow profiles in droplet-based analytical systems

Profile switching of two-phase flows is often required in microfluidic systems. Manipulation of flow profiles can be realized by control of local surface energy of micro channel through wettability-patterning of channel surface. This article presents a facile approach for wettability-patterning of the micro channels of glass chips. Commercially available octadecyltrichlorosilane (OTS) was used to hydrophobilize the channels via the formation of OTS self-assembly monolayer (SAM), and a UV-source that mainly emits deep UV-light of 254 and 185 nm was employed to degrade the in-channel formed OTS-SAM. The architecture of soda-lime glass/quartz glass hybrid chip was designed to facilitate the deep UV-light effective degrading the OTS-SAM. The established approach, together with the side-by-side laminar-flow patterning technique, was applied to prepare various finely patterned channel networks for different tasks of flow profile switching. The micro device capable of conducting the profile switch from W/O droplets to two separated continuous phases was demonstrated to perform on-chip quick liquid–liquid extraction for the determination of partition coefficients of pharmaceuticals.     

Effects of surface hydrophobization on the growth of self-assembled monolayers on silicon

The growth of self-assembled monolayers from octadecyltrichlorosilane (OTS) on modified silicon surfaces has been investigated. The influence of different immersion times in a deactivation reagent on the growth mechanism and the ordering of the films has been studied. Characterization of the films and the submonolayer coverage has been performed with tapping mode atomic force microscopy, ellipsometry, and infrared spectroscopy. We found that a deactivation of active sites led to a higher mobility of adsorbed molecules on the surface resulting in circular islands of highly ordered alkylsiloxane. However, upon prolonged immersion in OTS these ordered islands did not continue to grow and full monolayer coverage could not be obtained. Instead, an exchange reaction with the deactivation reagent leading to a disordered film between the ordered islands was observed. This was confirmed by external reflection infrared spectroscopy.     

Electrochemical and interface analysis of titanium alloy in simulated body fluid

The effect of raftiline inulin in presence of Ca²⁺ on titanium alloy as biomaterial was investigated in simulated body fluid solution at 37 °C. The behavior of Ti alloy was studied at different concentrations of inulin with immersion time using electrochemical impedance spectroscopy and potentiodynamic polarization tests. Ti alloy was effectively inhibited by the addition of 0.25% by weight raftiline in presence of 10^?5 m calcium levulinate, which reacts with Ti alloy and forms a protective film on its surface. The results were confirmed by surface examination via scanning electron microscope. Copyright © 2013 John Wiley & Sons, Ltd.     

Toward a quantitative description of the anodic oxide films on aluminum

A method to quantify the composition of anodic oxide films on aluminum using Infrared Spectroscopic Ellipsometry (IRSE) is proposed. It consists of obtaining the absorption coefficient of the film as a function of wavelength. Using values of the absorption coefficients for the pure components of the film, the percentages (mole or wt%) of each component in the sample can be calculated.The method is demonstrated in a study of the structure of the oxide film on electropolished aluminum and the anodically formed barrier layer film. Both surface oxides were found to be initially a form of amorphous Al₂O₃. While the barrier film is essentially free of water as prepared, the film on electropolished aluminum contained about 25 wt% water. Hydration of both types of films by immersion in boiling water results in the formation of pseudoboehmite (AlOOH). The technique may have more general applicability to the quantitative determination of the composition of corrosion films and other surface layers on metals.     

Plasma protein adsorption and thrombus formation on surface functionalized polypyrrole with and without electrical stimulation

A surface modification technique was developed in which heparin was covalently immobilized onto electrically conductive polypyrrole (PPY) film through poly(ethylene glycol) methacrylate (PEGMA) graft copolymerization and subsequent cyanuric chloride activation. In vitro plasma protein adsorption and thrombus formation experiments were carried out on the various films. The PEGMA-graft-copolymerized PPY surfaces with immobilized heparin have good bioactivity indicated by low level of protein adsorption, high ratio of albumin to fibrinogen adsorption, and low thrombus formation, making them potentially good candidates for biomedical applications. Since the PPY film retained significant electrical conductivity after surface modification, the effect of electrical stimulation on protein adsorption and thrombus formation was also evaluated. The covalently immobilized heparin on the PPY film was able to retain its bioactivity after 4 days of immersion in PBS. The film after long-term immersion in PBS also retained sufficient electrical conductivity for electrical stimulation still to be effective for reducing protein adsorption.     

Polyelectrolyte complex films derived from polyethyleneoxide-maleic acid copolymer and chitosan: preparation and characterization

Polyelectrolyte complex films were prepared with polyethyleneoxide-maleic acid copolymer and chitosan using a casting/solvent evaporation method. The films were examined in terms of their IR spectra, surface and cross-section morphologies, cytotoxicity, and swelling behavior at different pH levels. To assess the potential of these films as a biomedical device, the profiles of the release of model drug from the CS/PEOMA films were examined at pH 4.8. The surface morphology of the films was quite smooth and uniform, and the cross-sectional morphology was dense and homogeneous. The swelling behaviors of CS/PEOMA films were found to depend on the pH of the solution as well as on the CS/PEOMA composition. Drug release from different CS/PEOMA films at pH 4.8 was found to be dependent on film composition. The results showed the potential applicability of CS/PEOMA film as a drug delivery vehicle.     

Transport of topical anesthetics in vitamin E loaded silicone hydrogel contact lenses

Transport of surface active anesthetic drugs through silicone hydrogel contact lenses containing nanosized vitamin E aggregates is explored for achieving extended anesthetics delivery. Commercial silicone hydrogel contact lenses release most ophthalmic drugs including local anesthetics for only a few hours, which is not adequate. Here we focus on creating dispersion of highly hydrophobic vitamin E aggregates in the lenses as barriers for drug diffusion for increasing the release durations. This approach has been shown previously to be successful in extending the release durations for some common hydrophilic ophthalmic drugs. The topical anesthetic drugs considered here (lidocaine, bupivacaine, and tetracaine) are hydrophilic at physiologic pH due to the charge, and so these cannot partition into the vitamin E barriers. However, these surface active drug molecules adsorb on the surface of the vitamin E barriers and diffuse along the surface, leading to only a small decrease in the effective diffusivity compared to non-surface-active hydrophilic drugs. The drug adsorption can be described by the Langmuir isotherm, and measurements of surface coverage of the drugs on the vitamin E provide an estimate of the available surface area of vitamin E, which can then be utilized to estimate the size of the aggregates. A diffusion controlled transport model that includes surface diffusion along the vitamin E aggregates and diffusion in the gel fit the transport data well. In conclusion, the vitamin E loaded silicone contact lens can provide continuous anesthetics release for about 1-7 days, depending on the method of drug loading in the lenses, and thus could be very useful for postoperative pain control after corneal surgery such as the photorefractive keratectomy (PRK) procedure for vision correction.     

Titanium‐implanted CaTiO3 films and their changes in Hanks' solution

Titanium‐implanted CaTiO₃ film was prepared and then characterized by x‐ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectrometry (RBS) before and after immersion in Hanks' solution for 7 days. An as‐prepared specimen contained a small amount of Ar implanted during sputtering, although the pressure was as low as 10^?4 Torr. Even though Ar convolution increased with an increase in the relative Ti ion dose, most of the convoluted Ar was not from the Ar gas used for Ti ion production but rather was from the Ar gas used for sputtering the CaTiO₃. During Ti implantation, the CaTiO₃ films were ion‐etched by Ti ions. The composition of the CaTiO₃ film was not changed to any great degree by the Ti implantation, however its properties changed considerably. After immersion in Hanks' solution, the thickness of the specimen not implanted with Ti decreased the most whereas the [Ca]/[P] ratio, which was nearly unity before exposure, decreased significantly, becoming 0.23 on the Ti‐implanted specimen prepared at 200 W and 0.13 on the Ti‐implanted specimen prepared at 50 W. It was also observed by XPS that the ratio [Ca]/[P] was ～1.9 for all Ti‐implanted specimens after immersion in Hanks' solution for 7 days. Judging from the binding energies of Ca 2p_3/2 and P 2p electrons and the [Ca]/[P] ratio, it was suggested that a hydroxyapatite‐like substance had formed on the surfaces of the Ti‐implanted specimens after immersion in Hanks' solution. Copyright © 2003 John Wiley & Sons, Ltd.     

Interfacial properties of hydrophilized poly(lactic-co-glycolic acid) layers with various thicknesses

Biodegradable polyesters such as poly(lactic-co-glycolic acid) copolymers (PLGA) are preferred materials for drug carrier systems although their surface hydrophobicity greatly limits their use in controlled drug delivery. PLGA thin films on a solid support blended with PEG-containing compound (Pluronic) were used as model systems to study the interfacial interactions with aqueous media. Degree of surface hydrophilization was assessed by wettability, and X-ray photoelectron spectroscopy (XPS) measurements. Protein adsorption behavior was investigated by in situ spectroscopic ellipsometry. The degree of protein adsorption showed a good correlation with the hydrophilicity, and surface composition. Unexpectedly, the layer thickness was found to have a great impact on the interfacial characteristics of the polymer films in the investigated regime (20-200 nm). Thick layers presented higher hydrophilicity and great resistance to protein adsorption. That special behavior was explained as the result of the swelling of the polymer film combined with the partial dissolution of Pluronic from the layer. This finding might promote the rational design of surface modified biocompatible nanoparticles.     

Film‐ and ointment‐based delivery systems for the transdermal delivery of TNP‐470

Pathological angiogenesis, the process of new blood vessel formation, is responsible for a broad range of neovascular‐related systemic diseases. One of the first antiangiogenic compounds tested in clinical trials against cancer was TNP‐470. Despite promising activity the injectable drug showed poor plasma stability and caused adverse side effects in high doses lead to termination of the trials. In our current work, we introduce the development of a transdermal delivery systems for controlled release of TNP‐470. Such formulation can potentially reduce toxicity due to controlled continuous dosing and improve stability by avoiding gastrointestinal first pass metabolism. Although transdermal delivery is a very challenging route for drug administration due to the low permeability of the skin, here we present a successful development of two different drug delivery systems, film and ointment for dermal application of TNP‐470. Chitosan film had high loading capacity of up to 50% w/w of TNP‐470 compared with 10% maximum loading in hydrocarbon ointment. A detailed step‐by‐step development of TNP‐470 films, from the initial solvent screening to final optimized formulation, is presented. Ex vivo skin permeation studies demonstrated a superior release of the drug from the film formulation compared with the ointment. Furthermore, histological test of the skin confirmed ointment safety showing no evidence of skin tissues damage. Our results present novel, promising, controlled release drug delivery systems with improved stability, efficacy, and safety profile of TNP‐470 via transdermal route.     

Electrospun nanofibers for drug delivery applications: Methods and mechanism

Electrospinning procedures such as blend electrospinning, coaxial electrospinning, and emulsion electrospinning have been used for the fabrication of electrospun nanofibers (ENFs) for biomedical applications. These ENFs are attracted great interest especially in drug delivery applications due to their small size, high surface area-to-volume, and porosity. The aim of this review is to focus on the controlled release mechanism among the different electrospinning methods, and the selectivity of hydrophilic, water-soluble polymers as a carrier for drug. The mechanism for the drug delivery depends mainly on the method of drug loading, polymeric interactions, and the nature of polymer swelling, erosion, or degradation. This review compressed on the literature survey about the fabrication of nanofibers by different electrospinning methods, factors affecting the nanofiber morphologies, selectivity of polymeric blends for successful controlled release behavior, and the mechanism involved in the drug release steps.     

Low-temperature investigation of the growth mechanism of alkylsiloxane self-assembled monolayers

The growth behavior of self-assembled monolayer films strongly depends on parameters such as solvent, water concentration in the solvent, substrate type, and deposition method. A further parameter, the temperature, is of particular importance. It has been found that growth kinetics, size, and shape of the structures obtained strongly depend on the deposition temperature. Thus, exact adjustment and control of the solution temperature is of crucial importance for investigation of deposition mechanisms. The development of a temperature control unit has been the basis for a series of experiments on deposition of octadecyltrichlorosilane (OTS) on silicon wafers to study the influence of temperature on growth kinetics and film structure. Characterization of the films was performed with ellipsometry and atomic-force microscopy. It has been found that octadecylsiloxane (ODS) island sizes decrease with increasing temperature. Furthermore, a characteristic temperature exists above which increasingly disordered deposition occurs. At low temperatures (5–10 °C) smaller dot-like features are observed besides larger fractally shaped islands characteristic for self-assembly growth of ODS films. Our results indicate that these small dot-like features originate from ordered aggregates in the adsorption solution and that they are the precursors of the formation of larger islands. However, they can only be observed at low temperatures, because at room temperature they coalesce quickly to form larger units, due to the high surface mobility.     

Hyperthermal organic thin film growth on surfaces terminated with self-assembled monolayers. I. The dynamics of trapping

We have examined the initial stages of growth of a crystalline small molecule organic thin film, diindenoperylene (DIP), on SiO(2) surfaces terminated with a series of self-assembled monolayers (SAMs). In this study we make use of supersonic molecular beam techniques to vary the incident kinetic energy of the DIP molecules, and we use in situ, real time synchrotron x-ray scattering to monitor the buildup of each molecular layer in the growing thin film. We find that the effects of the SAMs are most apparent concerning growth in the sub-monolayer regime, before the substrate is entirely covered by the DIP thin film. In this coverage regime on bare SiO(2), and SiO(2) terminated with either hexamethyldisilazane or perflurooctyltrichlorosilane the adsorption dynamics are consistent with trapping-mediated adsorption as observed in more simple systems, where the probability of adsorption decreases significantly with increasing kinetic energy. Once these surfaces are covered with DIP, however, the adsorption probability increases, particularly at the highest incident kinetic energy, and the probability of adsorption exhibits only a weak dependence on the incident kinetic energy. In contrast, on surfaces terminated by octyl- (OTS) and octadecyltrichlorosilane (ODTS) the trapping probability is high and exhibits little dependence on the incident kinetic energy, essentially the same as what is observed on these same surfaces covered by DIP. We postulate, which is backed by the results of molecular dynamics simulations, that direct molecular insertion into the OTS and ODTS layers is a primary explanation for efficient trapping on these surfaces.     

Adsorption of phenyl phosphate on Ni-Cr alloy surface: Experimental and theoretical investigations

The adsorption behaviour of phenyl phosphate, which is an available biomolecule, on NiCr alloys was investigated. Atomic flame spectroscopy was used to characterize the elemental dissolution during immersion in neutral aqueous solution of 0.09 w% sodium chloride, 37°C. Phenyl phosphate is shown to reduce the release of both Ni²⁺ and Cr³⁺ ions. XPS analyses evidence the formation of a passive film which is mainly consisted in dichromium trioxide and an ultrafilm layer of phenyl phosphate is adsorbed at the passive film surface. DFT+U calculations show that the phenyl phosphate self-assembling at a Cr₂O₃ surface is thermodynamically favoured, with calculated adsorption energy of 2.9 eV. The first half of this value is due to the interaction with the surface, and the second one is due to self-assembling. This study suggests that phenyl phosphate has an important capacity to prevent, in neutral liquid environment, the release of Cr-Ni surface ions thanks to self-assembling in an inner sphere adsorption on the passive film surface. The phosphate group is covalently anchored to the surface. However, the phenyl ring has two roles: (i) it strongly contributes to the self-assembling and (ii) it acts as a hydrophobic function.     

Controlling adsorption and release of drug and small molecules by organic functionalization of mesoporous materials

A series of mesoporous nanosphere materials that are functionalized with various terminal and bridging organic groups were synthesized. They have improved adsorption capacity and different release properties for drug and small molecules. The materials contained terminal vinyl, 3-mercaptopropyl, 3-aminopropyl, and secondary amine functional groups and bridging ethane, ethene, and benzene groups within their mesopore channel walls. The samples containing mercaptopropyl and vinyl groups showed greater adsorption capacity and better controlled release behavior for rhodamine 6G molecules. On the other hand, mesoporous matrices containing amine functional groups showed higher adsorption capacity and better release properties for ibuprofen molecules. Further studies revealed that the bridging organic groups in the mesopore channel walls also improved the adsorption capacity and release properties of the materials compared to the corresponding samples containing no bridging organic groups. Such improved adsorption and controlled release properties of molecules by simple changes of functional groups on mesoporous materials are important for the development of nanomaterial drug delivery vehicles and for controlled release of drugs over long time periods at specific targeted sites in the body. By judicious choice of organic groups and by systematic design and synthetic approaches, nanoporous materials having different adsorption capacity and release properties for many other drug molecules can also be achieved.     

Novel phosphate–phosphonate hybrid nanomaterials applied to biology

A new process for preparing oligonucleotide arrays is described that uses surface grafting chemistry which is fundamentally different from the electrostatic adsorption and organic covalent binding methods normally employed. Solid supports are modified with a mixed organic/inorganic zirconium phosphonate monolayer film providing a stable, well-defined interface. Oligonucleotide probes terminated with phosphate are spotted directly to the zirconated surface forming a covalent linkage. Specific binding of terminal phosphate groups with minimal binding of the internal phosphate diesters has been demonstrated. On the other hand, the reaction of a bisphosphonate bone resorption inhibitor (Zoledronate) with calcium deficient apatites (CDAs) was studied as a potential route to local drug delivery systems active against bone resorption disorders. A simple mathematical model of the Zoledronate/CDA interaction was designed that correctly described the adsorption of Zoledronate onto CDAs. The resulting Zoledronate-loaded materials were found to release the drug in different phosphate-containing media, with a satisfactory agreement between experimental data and the values predicted from the model.     

Dual functional polyelectrolyte multilayer coatings for implants: permanent microbicidal base with controlled release of therapeutic agents

Here we present a new bifunctional layer-by-layer (LbL) construct made by combining a permanent microbicidal polyelectrolyte multilayered (PEM) base film with a hydrolytically degradable PEM top film that offers controlled and localized delivery of therapeutics. Two degradable film architectures are presented: (1) bolus release of an antibiotic (gentamicin) to eradicate initial infection at the implant site, or (2) sustained delivery of an anti-inflammatory drug (diclofenac) to cope with inflammation at the site of implantation due to tissue injury. Each degradable film was built on top of a permanent base film that imparts the implantable device surface with microbicidal functionality that prevents the formation of biofilms. Controlled-delivery of gentamicin was demonstrated over hours and that of diclofenac over days. Both drugs retained their efficacy upon release. The permanent microbicidal base film was biocompatible with A549 epithelial cancer cells and MC3T3-E1 osteoprogenitor cells, while also preventing bacteria attachment from turbid media for the entire duration of the two weeks studied. The microbicidal base film retains its functionality after the biodegradable films have completely degraded. The versatility of these PEM films and their ability to prevent biofilm formation make them attractive as coatings for implantable devices.     

Chitosan-Based Surface Molecularly Imprinted Polymer Microspheres for Sustained Release of Sinomenine Hydrochloride in Aqueous Media

The surface molecular imprinting technique has been proposed as a prospective strategy for template molecule recognition and separation by devising the recognition sites on the surface of imprinted materials. The purpose of this study was to establish a novel drug delivery system which was developed by surface molecular imprinting method using β-cyclodextrin (β-CD)-grafted chitosan (CS) (CS-g-β-CD) microspheres as matrix and sinomenine hydrochloride (SM) as the template molecule. By adjusting the amount of functional monomer and cross-linking agent, we got the more excellent adsorption of CS-g-β-CD molecularly imprinted polymers (MIPs-CS-g-β-CD). When the amount of functional monomer was 6 mmol and cross-linking agent was 20 mmol, the maximum binding capacity of MIPs and non-imprinted polymers (NIPs) was 55.9 mg/g and 37.2 mg/g, respectively. The results indicated that the recognition of SM with MIPs was superior to NIPs. The adsorption isotherms of MIPs-CS-g-β-CD indicated that the adsorption behavior fitted better to the Langmuir model, which showed that the adsorption process of polymer was monomolecular layer. In in vitro drug release studies, the accumulative release amount of MIPs-CS-g-β-CD was up to 78% within 24 h. MIPs exhibited an excellent controlled SM release profile without burst release and the mechanism of SM release was shown to conform to non-Fick diffusion. Therefore, MIPs-CS-g-β-CD were successfully applied to extraction of SM and used as the materials for drug delivery system.