Surface Modification Of Glass Research Articles

Preparation and applications of novel fluoroalkyl end‐capped vinyltrimethoxysilane oligomer/hydroxyapatite nanocomposites

AbstractNovel fluoroalkyl end‐capped vinyltrimethoxysilane oligomer/hydroxyapatite (HAp) nanocomposites were prepared by the reaction of calcium nitrate tetrahydrate and phosphoric acid in the presence of the corresponding oligomer. These fluorinated oligomer/HAp composites thus obtained are nanometer size‐controlled fine particles (83–173 nm), and were found to exhibit good dispersibility in methanol, ethanol, and isopropyl alcohol. These fluorinated HAp nanocomposites were applied to the surface modification of glass and poly(methyl methacrylate) (PMMA) to exhibit good hydro‐ and oleophobic characteristics imparted by fluorine on their surface. In addition, the surface structural changes of the modified polyethylene terephtalate and PMMA films treated with these fluorinated nanocomposites before and after soaking in a simulated body fluid (SBF) were analyzed by using SEM, XRD, and EDX to observe the formation of spherical HAp deposits on the surface. Copyright © 2009 John Wiley & Sons, Ltd.

Organic light-emitting diode performance enhancement via indium tin oxide glass surface modification

A self-assembly monolayer (SAM), with phenyl-triethoxysilane (PTES), was used to modify the indium tin oxide anode for an organic light-emitting diode (OLED) in order to improve the OLED performance. The enhancement of OLED performance is attributed to the blockage of excessive hole injection by PTES, balancing the hole and electron injection numbers. The result indicates that the SAM process reaction time duration greatly affects the OLED performance outcomes. If the reaction time is too long, it will impact on the optical efficiency due to molecular aggregates accumulated on the SAM layers, thus reducing the performance of the OLEDs. The electrical and optical characteristics of the OLEDs are modeled by using the modified Shockley equation. Modified Shockley parameters are extracted to interpret the experimental data with excellent accuracy. Those parameters, both electrical and optical, can be used as the DC level modeling parameters for OLED product design simulations.

Differences in colonisation of five marine bacteria on two types of glass surfaces

The retention patterns of five taxonomically different marine bacteria after attachment on two types of glass surfaces, as-received and chemically etched, have been investigated. Contact angle measurements, atomic force microscopy (AFM), scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), X-ray fluorescence spectroscopy (XRF) and X-ray photoelectron spectrometry (XPS) were employed to investigate the impact of nanometer scale surface roughness on bacterial attachment. Chemical modification of glass surfaces resulted in a ∼1 nm decrease in the average surface roughness (R a) and the root-mean-squared roughness (Rq ) and in a ∼8 nm decrease in the surface height and the peak-to-peak (R max) and the 10-point average roughness (Rz ). The study revealed amplified bacterial attachment on the chemically etched, nano-smoother glass surfaces. This was a consistent response, notwithstanding the taxonomic affiliation of the selected bacteria. Enhanced bacterial attachment was accompanied by elevated levels of secreted extracellular polymeric substances (EPS). An expected correlation between cell surface wettability and the density of the bacterial attachment on both types of glass surfaces was also reported, while no correlation could be established between cell surface charge and the bacterial retention pattern.

Preparation and characterization of biodegradable poly(d,l-lactide) and surface-modified bioactive glass composites as bone repair materials

In order to improve filler dispersion and phase compatibility between poly(D,L-lactide) (PDLLA) and inorganic bioactive glass (BG) particles, and to enhance the mechanical properties of PDLLA/BG composites, the silane coupling agent 3-glycidoxypropyltrimethoxysilane (KH570) was used to modify the surface of BG particles (represented by KBG). The structure and properties of PDLLA/BG and PDLLA/KBG composites were investigated by mechanical property testing and scanning electron microscopy (SEM). This study demonstrated that the Guth and Gold models can be combined to predict the Young's modulus of the composites. The Pukanszky modulus showed that the interaction parameter B of PDLLA/KBG composites was higher than that of the PDLLA/BG, which indicates that there is a higher interfacial interaction between the PDLLA and KBG. The composites were incubated in simulated body fluid (SBF) at 37 degrees C to study the in vitro degradation and bioactivity of the composites and to detect bone-like apatite formation on their surfaces.

Influence of surface energy distribution on neuritogenesis

PC12 cells are a useful model to study neuronal differentiation, as they can undergo terminal differentiation, typically when treated with nerve growth factor (NGF). In this study we investigated the influence of surface energy distribution on PC12 cell differentiation, by atomic force microscopy (AFM) and immunofluorescence. Glass surfaces were modified by chemisorption: an aminosilane, n-[3-(trimethoxysilyl)propyl]ethylendiamine (C 8H 22N 2O 3Si; EDA), was grafted by polycondensation. AFM analysis of substrate topography showed the presence of aggregates suggesting that the adsorption is heterogeneous, and generates local gradients in energy of adhesion. PC12 cells cultured on these modified glass surfaces developed neurites in absence of NGF treatment. In contrast, PC12 cells did not grow neurites when cultured in the absence of NGF on a relatively smooth surface such as poly- l-lysine substrate, where amine distribution is rather homogeneous. These results suggest that surface energy distribution, through cell–substrate interactions, triggers mechanisms that will drive PC12 cells to differentiate and to initiate neuritogenesis. We were able to create a controlled physical nano-structuration with local variations in surface energy that allowed the study of these parameters on neuritogenesis.

Fluorescence-based peptide screening using ligand peptides directly conjugated to a thiolated glass surface

Functional peptides from peptide libraries are frequently screened using an array format. We report here results of a feasibility study of fluorescence-based peptide screening using an array format on surface-modified glass. The surface of an amine-coated glass slide was modified to contain thiol groups by iminothiolane treatment. The epsilon-amine of the C-terminal lysine from a ligand peptide was iodinated and then spotted onto the thiolated glass surface to covalently conjugate the ligand peptide to the surface via a thioether bond. This covalent immobilization allowed the ligand peptides to withstand washing steps by tightly adhering to the glass surface and confining their subsequent binding reactions within a spotted area. Two representative peptides were used as the ligand peptides; a 'target' (positive) heptapeptide that could specifically bind to trypsin, and a 'control' (negative) hexapeptide that had no binding affinity with trypsin. When fluorescein isothiocyanate-labeled trypsin was reacted with the ligand peptides, the target peptide demonstrated distinctively higher (ca. 8.7-fold) fluorescence intensity that was easily differentiated from the control peptide by a fluorescence scanner. A separate experiment using a quartz crystal microbalance confirmed that the difference in binding mass (ca. 9.1-fold) was very close to that seen in fluorescence intensity. These results suggested a quantitative, 1:1 correlation between mass and fluorescence signals. Furthermore, a smaller spot volume and a higher ligand peptide concentration resulted in higher fluorescence signal intensity. This study provides information on the potential for using fluorescence-based screening of functional peptides on a glass array format.

Inverted pattern formation of cell microarrays on poly(ethylene glycol) (PEG) gel patterned surface and construction of hepatocyte spheroids on unmodified PEG gel microdomains

We present herein the novel technique for constructing inverted cell-adhesion patternes on PEG gel modified glass surfaces by photoirradiation using the same photomask and materials. The PEG gel micropatterns were prepared by a photolithographic technique using a photomask with 100 microm aligned cavities after spin-coating of a mixed solution of alpha,omega-dimethacryloyl-PEG (PEG-DMA) and a photoinitiator on glass surfaces. When methanol was used as a casting solvent for the spin-coating (Method A), the circular PEG gel domains with a diameter of 100 microm were fabricated on the surface, and as would be predicted, seeded bovine aortic endothelial cells (BAECs) adhered to the glass area on the constructed surface to form a BAECs sheet with 100 microm aligned cavity. In contrast, it was rather surprising for us that a complete inverted cell pattern was formed when the PEG gel pattern surface was prepared using methanol/water co-solvent (Method B). Furthermore, when hepatoma cancer cells were seeded on the constructed surface prepared by Method B, they formed a spherical multicellular aggregate (spheroid) on the unmodified PEG gel domains without feeder cells. In order to obtain information on this peculiar phenomenon, fluorescence-based protein adsorption experiments, contact angle measurements, and X-ray photospectroscopy (XPS) analysis were carried out.

Method for the Accurate Preparation of Cell-Spiking Standards

Preparation of calibration standards for cell enumeration is critical in characterizing the performance of any method or apparatus intended for recovering rare cells. Diluting a cell suspension serially is prone to statistical sampling errors as the cell suspension becomes more dilute, whereas transferring and injecting cells individually into a diluent with a micromanipulator is time-consuming. We developed a simple and robust method using a surface-modified glass capillary to siphon and eject cells. One-dimensional confinement of cells offered by the capillary made cell enumeration by visual counting simple and rapid, and cell ejection from the capillary was near 100% when the appropriate surface coating and cell solution was used. The residence time of cells in the capillary, however, could affect the percentage of cells that was ejected from the capillary. To characterize the performance of this method, we enumerated the ejected cell using both visual counting under a microscope and automated detection using a chip-based flow cytometer.

Surface Modification of Bioactive Glasses and Preparation of PDLLA/Bioactive Glass Composite Films

In order to improve the homogeneous dispersion of particles in the polymeric matrix, 45S5, mesoporous 58S, and 58S bioactive glasses were surface modified by esterification reactions with dodecyl alcohol at reflux temperature of 260 degrees C (named as m-45S5, m-mesoporous 58S, and m-58S, respectively). The modified particles showed better hydrophobicity and longer time of suspension in organic matrix. The PDLLA/bioactive glass composite films were fabricated using surface modified bioactive glass particles through solvent casting-evaporation method. Surface morphology, mechanical property, and bioactivity were investigated. The results revealed that the inorganic particle distribution and tensile strength of the composite films with modified bioactive glass particles were significantly improved while great bioactive properties were maintained. Scanning electron microscopy (SEM) observation illustrated that the modified bioactive glass particles were homogeneously dispersed in the PDLLA matrix. The maximum tensile strengths of composite films with modified bioactive glass particles were higher than that of composite films with unmodified bioactive glass particles. The bioactivity of the composite films were evaluated by being soaked in the simulated body fluid (SBF) and the SEM observation of the films suggested that the modified composite films were still bioactive in that they could induce the formation of HAp on its surface and the distribution of HAp was even more homogeneous on the film. The results mentioned above indicated that the surface modification of bioactive glasses with dodecyl alcohol was an effective method to prepare PDLLA/bioactive glass composites with enhanced properties. By studying the comparisons of modification effects among the three types of bioactive glasses, we could get the conclusion that the size and morphology of the inorganic particles would greatly affect the modification effects and the properties of composites.

Study on the Structure and Mechanical Properties of Dental Barium Glass Particles Surface Modification with Silane Coupling Reagent

The surface-modified dental barium glass with silane coupling reagent KH-570 was studied. The prepared samples before and after modification were characterized by static precipitation, angle of contact, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared ray, and thermo-gravimetric analysis. Research showed that the KH-570 was bound on the surface of barium glass, a firm chemical bonding of KH-570 to barium glass and an organic layer was formed, and the maximum mass fraction of KH-570 coated on the barium glass surface measured was about 2.86%. The surface performance of modified barium glass changed from hydrophilic to hydrophobic. Mechanical tests revealed that the mechanical properties of composite resin filled by KH-570 modified barium glass improved simultaneously.

Osteoblast proliferation and maturation on bioactive fiber-reinforced composite surface

The objective of this study was to evaluate the proliferation and osteogenic potential of bone-marrow derived osteoblast-like cells on fiber-reinforced composite (FRC) substrates with and without bioactive glass surface modification. Three FRC materials were fabricated for the study: (a) grit-blasted FRC, (b) grit-blasted FRC with bidirectional net reinforcement and (c) FRC with bioactive glass (BAG) coating. Rat bone-marrow derived osteoblast-like cells were harvested and cultured on experimental material plates and on cp. titanium plates (control) for 21 days. The materials' surfaces were characterized by roughness testing and scanning electron microscopy. Cell growth and differentiation kinetics were subsequently investigated by evaluating proliferation, alkaline phosphatase (ALP) activity, osteocalcin (OC) and bone sialoprotein (BSP) production. On day 14, the cell proliferation was significantly lower (P<0.05) on FRC-BAG than on titanium and FRC. The proliferation on the other three materials was equal throughout the experiment. The maximal ALP activities on FRC, FRC-Net, and titanium were observed on day 21, whereas FRC-BAG had already reached the maximal level on day 14. Expression of osteoblastic markers (OC, BSP) indicates that the fastest osteogenic differentiation takes place on FRC after 7 days. In contrast, a slower differentiation process was observed on titanium than on any other tested material (P<0.015) at 21 days, as was confirmed by increased mRNA expression of OC and BSP. It can be concluded that the proliferation and maturation of osteoblast-like cells on FRC appears to be comparable to titanium. Presence of BAG enhances cell maturation.

Preparation and applications of a variety of fluoroalkyl end-capped oligomer/hydroxyapatite composites

A variety of fluoroalkyl end-capped oligomers were applied to the preparation of fluorinated oligomer/hydroxyapatite (HAp) composites (particle size: 38–356 nm), which exhibit a good dispersibility in water and traditional organic solvents. These fluoroalkyl end-capped oligomer/HAp composites were easily prepared by the reactions of disodium hydrogen phosphate and calcium chloride in the presence of self-assembled molecular aggregates formed by fluoroalkyl end-capped oligomers in aqueous solutions. In these fluorinated HAp composites thus obtained, fluoroalkyl end-capped acrylic acid oligomers and 2-methacryloyloxyethanesulfonic acid oligomer/HAp nanocomposites afforded transparent colorless solutions toward water; however, fluoroalkyl end-capped N , N -dimethylacrylamide oligomer and acryloylmorpholine oligomer were found to afford transparent colorless solutions with trace amounts of white-colored HAp precipitants under similar conditions. HAp could be encapsulated more effectively into fluorinated 2-methacryloyloxyethanesulfonic acid oligomeric aggregate cores to afford colloidal stable fluorinated oligomer/HAp composites, compared to that of fluorinated acrylic acid oligomers. These fluorinated oligomer/HAp composites were applied to the surface modification of glass and PVA to exhibit a good oleophobicity imparted by fluorine. HAp formation was newly observed on the modified polyethylene terephthalate film surface treated with fluorinated 2-methacryloyloxyethanesulfonic acid oligomers and acrylic acid oligomer/HAp composites by soaking these films into the simulated body fluid.

Third-order Nonlinear Optical Properties of Regioregular Poly(3-Hexylthiophene) Thin Films on Quartz Glasses Modified by Hexamethyldisilazane

Regioregular poly(3-hexylthiophene) [RR-P3HT] thin films were prepared on fused quartz glasses by spin-coating and drop-casting from the chloroform solutions. The effect of surface modification of quartz glass by hexamethyldisilazane (HMDS) on the RR-P3HT film structures was investigated. Film structures and morphologies were characterized by UV-visible absorption spectra, out-of-plane X-ray diffraction (XRD) and atomic force microscopy (AFM). The third-order nonlinear optical (NLO) susceptibilities Χ(3)(-3ω; ω, ω, ω) of the RR-P3HT films were determined by the third harmonic generation (THG) technique with an incident wavelength of 1064 nm. The drop-cast film shows enhanced Χ(3) of about three times of that of the spin-coated one, and HMDS treatment can increase the Χ(3) further to about 30 percent higher than the untreated one, keeping all the film thicknesses around 140 nm These results revealed the deposition method and surface modification effects on the RR-P3HT film structures, and the importance of higher ordering (enhanced inter-molecular interactions through π-π stacking) and increased crystallinity to the enhancement of the Χ(3) of the polymeric films for their applications in NLO devices.

Surface modification and biocompatibility of Ni-free Zr-based bulk metallic glass

The surface of Ni-free Zr 60 Ti 6 Cu 20 Fe 5 Al 10 bulk metallic glass (BMG) was modified to be bioactive by using the micro-arc oxidation technique. A rough and porous oxide layer mainly containing tetragonal ZrO 2 and amorphous SiO 2 incorporating some Ca and P was formed. This layer adhered very well to the BMG substrate and exhibited a superior biocompatibility.

Dual-Surface-Modified Reverse-Selective Membranes

The reverse selectivity of inorganic membranes can be enhanced by surface modification using long hydrocarbon chain silanes. Improvements in n-C4H10 selectivity of Vycor porous glass over N2 and CH4 were obtained by sequentially modifying it with a C18 monochlorosilane (OCS) followed by a C18 trichlorosilane (ODS). The membranes were tested for pure and mixed gases at different feed pressures. The dual-modified membranes have higher ideal, or pure-gas, selectivities than membranes modified using OCS alone. The n-C4H10/N2 and n-C4H10/CH4 ideal selectivities for the dual-modified membrane were 88 and 35, respectively, as compared to values of 13 and 7, respectively, for the OCS-modified membrane. Adsorption experiments showed an increase in the relative adsorption of n-C4H10 over N2 and CH4 after dual surface modification of Vycor glass. Nuclear magnetic resonance, X-ray photoelectron spectroscopy, and thermogravimetric analysis techniques were used to confirm the presence of silanes on the surface of the substrates. A high flux of n-butane was measured for a dual-modified membrane fabricated using a 5 nm pore diameter γ-alumina ultrafilter substrate. The mixed-gas n-butane permeance for this membrane was 2 × 10-4 cm3(STP) cm-2 cm Hg-1 s-1 (6.7 × 10-8 mol m-2 s-1 Pa-1).

Development of peptide-based patterns by laser transfer

Peptide-based arrays and patterns have provided a powerful tool in the study of protein recognition and function. A variety of applications have been identified, including the interactions between peptides–enzymes, peptides–proteins, peptides–DNA, peptides–small molecules and peptides–cells. One of the main and most critical unresolved issues is the generation of high-density arrays which maintain the biological function of the peptides. In this study, we employ nanosecond laser-induced forward transfer for the generation of high-density peptide arrays and patterns on modified glass surfaces. We show that peptide-based microarrays can be fabricated on solid surfaces and specifically recognized by appropriate fluorescent tags, with the transfer not affecting the ability of the peptides to form fibrils. These initial results are poised to the construction of larger peptide patterns as scaffolds for the incorporation and display of ligands critical for cell attachment and growth, or for the templating of inorganic materials.

Spot arrays on modified glass surfaces for efficient SPOT synthesis and on‐chip bioassay of peptides

To make SPOT synthesis of peptides and their assays on glass surfaces more convenient, a simple method for making spot arrays on a slide glass was designed through patterning with a photoresist and perfluorination followed by amination with various silane compounds and polymers. With these spot-arrayed glass surfaces, we could measure the coupling completion of each Fmoc amino acid on the glass surface by direct fluorescence analysis after fluorescence-labeling the amino groups on the surface of each spot. Then we synthesized several types of decapeptides and HPQ-pentapeptides on the spot-arrayed glasses and identified the optimal surface condition for stepwise peptide coupling and on-chip bioassay. After optimizing the surface conditions, we synthesized a model library of biotin-Gly-Ala-P(1)-Gly (P(1): one of 19 amino acids) and successfully replicated the well-known alpha-chymotrypsin subsite specificities through Cy5-streptavidin binding to the remaining biotin on the surface after the enzymatic digestion.

Surface modification of plastic, glass and titanium by photoimmobilization of polyethylene glycol for antibiofouling

Photoreactive poly(ethylene glycol) (PEG) was prepared and the polymer was photoimmobilized on organic, inorganic and metal surfaces to reduce their interaction with proteins and cells. The photoreactive PEG was synthesized by co-polymerization of methacrylate-PEG and acryloyl 4-azidobenzene. Surface modification was carried in the presence and the absence of a micropatterned photomask. It was then straightforward to confirm the immobilization using the micropatterning. Using the micropatterning method, immobilization of the photoreactive PEG on plastic (Thermanox™), glass and titanium was confirmed by time-of-flight secondary ion mass spectroscopy and atomic force microscopy observations. The contact angle on an unpatterned surface was measured. Although the original surfaces have different contact angles, the contact angle on PEG-immobilized surfaces was the same on all surfaces. This result demonstrated that the surface was completely covered with PEG by the photoimmobilization. To assess non-specific protein adsorption on the micropatterned surface, horseradish peroxidase (HRP)-conjugated proteins were adsorbed. Reduced protein adsorption was confirmed by vanishingly small staining of HRP substrates on the immobilized regions. COS-7 cells were cultured on the micropatterned surface. The cells did not adhere to the PEG-coated regions. In conclusion, photoreactive PEG was immobilized on various surfaces and tended to reduce interactions with proteins and cells.

Two methods for glass surface modification and their application in protein immobilization

Protein immobilization is a crucial step in protein chip, biosensor, etc. Here, two methods to immobilize proteins on glass surface were analyzed, one is silanization method using 3-aminopropyltriethoxysilane (APTES), and the other is hydrophobin HFBI coating. The modified glass surfaces were characterized with X-ray photoelectron spectroscopy (XPS), water contact angle measurement (WCA) and immunoassay. The results of XPS and WCA illustrated that the surface property of glass can be changed by both the two methods. The following immunoassay using microcontact printing (μCP) verified that both methods could help protein immobilization effectively on glass slides. Compared with the amine treatment, it is concluded that hydrophobin self-assemblies is a simple and generic way for protein immobilization on glass slides, which has potential application in protein chips and biosensors.

Amplified protein sensing using deep purple fluorophores on homogeneous Au substrates

We report here the first observation of appreciable enhancement of fluorescence induced by large Au colloids. Au monolayers with Au colloids of 40 nm, 59 nm, and 81 nm in radii, were formed on silane modified glass surfaces, respectively. The nanoparticle densities were varied by varying the deposition times and documented by scanning electron microscopy. Two types of samples were prepared, with large inter-particle distance and hence little or no inter-particle coupling and small inter-particle distance with inter-particle coupling. The fluorescence enhancement was examined by using a self assembled monolayer of the fluorophore-protein conjugate with Deep Purple as a fluorophore and Bovine Serum Albumin as protein (DP-BSA). The data show the over 15 fold enhancement under optimized conditions and reveal strong variations with both inter-particle distance and particle size. Nanostructures of appropriate size with optimized inter-particle distance thus prepared can produce promising substrates for decent fluorescence enhancement. We demonstrated that the Au colloid monolayers on glass surfaces are promising substrates for fluorescence enhancement with outstanding macroscopic homogeneity. This important feature will pave the way for the application of our substrates in biotechnology and life sciences such as imaging and sensing of biomolecules in proteomics.