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Sonicated small unilamellar egg yolk phosphatidylcholine (EggPC) vesicles were investigated using atomic force microscopy (AFM) imaging and force measurements. Three different topographies (convex, planar, and concave shape) of the EggPC vesicles on the mica surface were observed by tapping mode in fluid, respectively. It was found that the topography change of the vesicles could be attributed to the interaction force between the AFM tip and vesicles. Force curves between an AFM tip and an unruptured vesicle were obtained in contact mode. During approach, two breaks corresponding to the abrupt penetration of upper and lower bilayer of vesicle were exhibited in the force curve. Both breaks spanned a distance of around 4 nm close to the EggPC bilayer thickness. Based on Hertz analysis of AFM approach force curves, the Young’s modulus (E) and the bending modulus (kc) for pure EggPC vesicles were measured to be (1.97 ± 0.75) × 10 6 Pa and (0.21 ± 0.08) × 10 −19 J, respectively. The results show that the AFM can be used to obtain good images of intact and deformed vesicles by tapping mode, as well as to probe the integrity and bilayer structure of the vesicles. AFM force curve compare favorably with other methods to measure mechanical properties of soft samples with higher spatial resolution. © 2003 Elsevier B.V. All rights reserved.

The self-associating structures at the solid-liquid interface of three nonionic trisiloxane surfactants ((CH3)3SiO)2Si(CH3)(CH2)3(OCH2CH2)n OH (n = 6, 8, and 12), or BEn, are studied as a function of substrate properties by atomic force microscopy (AFM) imaging and force measurement. These trisiloxane surfactants are known as superwetters, which promote rapid spreading of dilute aqueous solutions on low-energy surfaces. This study also attempts to relate the BEn surface aggregate structures at the solid-liquid interface to their superwetting behavior. Four substrates are used in the study: muscovite mica, highly oriented pyrolytic graphite, and oxidized silicon wafer with and without a full monolayer of self-assembled n-octadecyltrichlorosilane (OTS). The concentration of BEn is fixed at 2 times the critical aggregation concentration (CAC). The BEn surfactants are only weakly attracted to hydrophilic surfaces, more on oxidized silicon than on mica. All three form ordinary planar monolayers on HOPG and OTS-covered oxidized silicon. The significance of surfactant adsorption on the AFM tip is investigated by comparing the force curves obtained by tips with and without thiol modification. The surface aggregate structures of the BEn surfactants correlate with their bulk structures and do not exhibit anomalous adsorption behavior. The adsorption behavior of the BEn superwetters is similar to that of the CmEn surfactants. Thus, our results confirm previous work showing that superwetting shares its main features with other classes of surfactants.

We investigate the making of semiconductor nanorods using well-defined molecular templates. The films are characterized by AFM and XPS. The spin-coated monolayer of arachidic acid assembles on graphite as 1D nanostripes with bilayer periodicity. The copper arachidate film shows curved stripes, which become straight after reacting with hydrogen sulfide. The new template scheme may facilitate the fabrication of nanorod arrays of a variety of inorganic and semiconducting materials.

icone polyether (SPE) surfactants. The SPE surfactants exhibit several unique properties (4): (1) they can lower the air/water interfacial tension to about 20 mN/m; (2) the siloxane chain remains flexible and in the liquid state up to high molecular weight; (3) they are surface active in both aqueous and nonaqueous media; and (4) they are suitable for cosmetic applications because they cause little skin irritation. The base of the SPE surfactants is polydimethylsiloxane (PDMS). PDMS with sufficient molecular weight, e.g., about 1000, is well known for its hydrophobicity as well as oleophobicity. In particular, the oleophobicity distinguishes the silicone-based surfactants from their hydrocarbon counterparts. The molecular structure of SPEs is either comblike, with the polyoxyalkylene chain side-grafted to a PDMS backbone, or linear diblock (AB) and triblock (ABA) types, with A representing the polyoxyalkylene hydrophile and B the PDMS hydrophobe. SPEs incorporating copolymers of polyoxyethylene (PEO) and polyoxypropylene (PPO) are widely used in polyurethane foam manufacture and personal care prod

Active β-catenin signaling in melanoma is associated with aggressive disease. We have previously shown that Rad6B, an ubiquitin conjugating enzyme, is a positive regulator of β-catenin stability and transcriptional activity, and is itself a transcriptional target of β-catenin. This stabilization is mediated by Rad6B-induced K63-linked polyubiquitination of β-catenin that renders it insensitive to 26S proteasomal degradation. Immunohistochemical analysis of human cutaneous melanoma samples showed the first detectable expression of Rad6B in melanocyte hyperplasia and continued Rad6B and β-catenin overexpression in primary and metastatic melanomas. These data implicate a critical role for Rad6B in melanocyte transformation and a continuing role in melanoma progression. To analyze the role of Rad6B in melanomagenesis, we targeted Rad6B expression/activity in human M14 metastatic melanoma cells by using a Rad6-selective small molecule inhibitor SMI#9 and the CrispR/Cas9 gene editing system. Immunoblot analysis showed that compared to controls, M14 cells treated with SMI#9 showed decreased levels of β-catenin, and β-catenin driven transcriptional targets Rad6, vimentin, Mitf-M, and Melan A. Although Snail levels were not altered, SMI#9 treated cells showed increase in phosphorylated Snail. Immunocytochemical staining verified the western blot data and showed cytoplasmic relocalization of PCNA and Snail in SMI#9 treated cells which is consistent with increase in phosphorylated Snail. Concordant with the decrease in vimentin and unphosphorylated Snail levels, Rad6B-inhibited cells display poor capacity to migrate as compared to controls. Whereas Rad6B knockout cells were severely growth impaired, Rad6B edited clones showing partial expression (potentially from only one allele) similarly showed decreased levels of β-catenin, vimentin, and Mitf-M. Similar to Rad6B-inhibited cells, Rad6B edited cells were migration- and invasion-impaired. Whereas control cells produced robust tumors and overt lung metastases, the Rad6B gene edited cells were poorly tumorigenic. Rad6B gene edited clones showed complete loss of Melan A. Since Mitf-M is a transcriptional regulator of Melan A and a key player in melanocyte lineage specification, our data suggest that targeting Rad6B could potentially inhibit melanomagenesis by reprogramming melanoma cells. Supported by NIH CA178117 and 3Balls Racing. Citation Format: Ashapurna Sarma, Sarah Petit, Fangchao Liu, Pratima Nangia-Makker, Guangzhao Mao, Malathy Shekhar. Targeting Rad6B suppresses melanomagenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1149. doi:10.1158/1538-7445.AM2017-1149

The interaction forces provided by silicone polyether (SPE) surfactants, adsorbed at the interface of octadecyltrichlorosilan monolayer and aqueous surfactant solution, were measured by atomic force microscopy. Changes in the forces in the presence of ethanol were examined for a series of comb-type SPE surfactants. It was found that the steric repulsion provided by the SPE molecules persisted up to an 80% or higher ethanol level. Conversely, conventional hydrocarbon surfactants such as dodecyl polyoxyethylene ether lose their interfacial activity at much lower ethanol levels. The force measurement results were compared favorably with the findings from emulsion-stability and interfacial-tension measurements. The difference between the conventional hydrocarbon surfactants and the SPE surfactants is attributed to the polysiloxane moiety being hydrophobic but not oleophilic. The polyoxypropylene units in the polyether chain were found to add unique characteristics to the surface behavior of the SPE surfactants by modifying the hydrophile's solubility in the alcoholic media. The surface activity and colloidal stability can be fine-tuned by the ratio of polyoxypropylene to polyoxyethylene. In general, emulsion and colloidal products and processes that contain alcohol or other nonaqueous media will benefit from the unique properties of this special class of SPE surfactants.

Through the direct measurement on the microscopic image of a two-dimensional (2-D) colloidal polycrystalline array, the statistical distribution profiles of the crystalline grain size and the defect density were determined. At the same time, an optical diffraction analysis method was developed to extract the mean values of these two parameters from the measured diffraction pattern. Results from the two methods were compared. We found that both parameters obey the Poisson distribution. For grain size, the discrete unit of the distribution is the average distance between the neighboring defects. It implies that the growth of crystalline grains displays a process of increasing grain size with this quantum value. A possible reason for this distribution is discussed based on the atomic force microscopy (AFM) images.

Atomic force microscopy (AFM) was used to study the aggregation structure and kinetics of nonionic surfactant penta(oxyethylene) dodecyl ether (C12E5) on mica as a function of temperature. Surface forces and topographical images of surfactant aggregates at the liquid/solid interface were captured in the vicinity of 21 °C. The surfactant molecular aggregates were imaged by choosing an imaging force in the steric repulsion region so that the AFM tip was just outside the surface of the aggregates. At below 21 °C, C12E5 adsorbed as fragments of tens of nanometers in size. The fragments consist of 1−2 nm thick strongly adsorbed species and weakly adsorbed species extending as far as 15 nm from the substrate surface. The fragments gradually increased in number and attached to each other to form clusters connected in one dimension (strings) and two dimensions (networks). With increasing surface coverage, the surface force changed from a purely attractive one to one showing a repulsive force barrier. At above 21 ...

A mixed film of microscopic heterogeneity was formed by stepwise deposition of a long-chain organosilane n -octadecyltrichlorosilane (OTS) and a short-chain organosilane aminobutyldimethylmethoxysilane (ABS). The amount of silane deposited on an oxidized silicon substrate was controlled kinetically by varying the dip time in each silane solution. The binary film was characterized by the atomic force microscopy (AFM), infrared attenuated total internal reflection (IR-ATR), and contact angle goniometry. OTS forms a monolayer structure whose fractional surface coverage and surface energy can be precisely controlled. ABS agglomerates slowly to form island structure and is ineffective in surface energy or composition variation. The contact angles on sub-monolayers of OTS follows the Cassie equation, while the contact angle of the binary OTS and ABS film deviates positively from the equation.

Langmuir–Blodgett (LB) multilayers of arachidic acid (AA) and octadecylamine (ODA) were used as templates in order to produce cadmium sulfide (CdS) nanoparticle arrays. Both atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used to characterize the film. In the absence of ODA, the cadmium arachidate trilayers were highly crystalline with a lattice constant of 0.42 nm. Upon reaction with hydrogen sulfide (H2S), an ordered array of CdS nanoparticles with a particle separation of 4.2 nm was imaged. The existence of CdS was also confirmed by XPS. No CdS nanoparticles were formed when ODA was used as the sole component. In the presence of ODA, the crystalline structure of the AA film was disturbed, resulted in randomly distributed particles. The average particle height was reduced from 4 to 1 nm when the amount of ODA was increased. It is concluded that there is a direct correlation between the ordering of the organic template and that of the nanoparticle array. There is also a correlation between the particle size and the ratio of AA and ODA. Mixed LB films are promising in synthesizing semiconducting nanoparticle arrays of limited particle sizes.

The simple molecular structure, relatively high stability, and color variation with molecular packing structure make the streptopolymethine dyes an ideal candidate for the study of surface effects ...

A recently developed method of spherulitic crystallization was used for the preparation of highly ordered 80 nm thin films of the dye 1.7-bis(dimethylamino)heptamethinium perchlorate (BDH+ClO4-). Depending on the crystallization temperature, the film color and surface topography varied widely, while the crystal structure and film thickness remained the same. At low undercooling, two homogeneous regions were obtained. One showed in-plane symmetrical and the other asymmetrical growth behaviors. At high undercooling, a banded spherulitic structure with rainbow-like colors developed, whose formation is attributed to the out-of-plane asymmetrical growth. The spherulitic growth kinetics, microstructure, and optical properties were investigated by optical microscopy, atomic force, and scanning tunneling microscopy in static and real time mode. A molecular mechanism is proposed which originates from different directions of macroscopic growth and microscopic molecular attachment dictated by the three-dimensional c...

Atomic force microscopy (AFM) studies of N-[4-[4-cyano-2-(2-furanylmethylene)-2,5-dihydro-5-oxo-3-furanyl]phenyl]-1-butanesulfonamide (1), a crystalline dye used in photographic film, are described. AFM of the largest crystal face of freshly cleaved blade-shaped crystals of 1 revealed molecular scale contrast with periodicity identical with the low-energy oleophilic (100) plane, and ledges oriented along [001] with step heights equal to the a lattice parameter, which corresponds to the height of single molecules of 1. These features are consistent with the solid-state structure of the dye, which reveals a low-energy oleophilic (100) plane and strong intermolecular π−π interactions along [001]. Real-time in situ AFM reveals that growth of 1 near equilibrium conditions proceeds by flow of the [001] ledges along the [010] direction, consistent with the relative surface energies of the crystal planes and a terrace−ledge−kink mechanism. Addition of an ionic octyl oligoether sulfate surfactant to the growth med...

It is well established that the status of the endoplasmic reticulum (ER) and mitochondria, and the interactions between them, is critical to numerous cellular functions including apoptosis. Mitochondrial dynamics is greatly influenced by cell stress, and recent studies implicate ER in mitochondrial fission. Although a number of proteins have been identified to participate in ER-induced mitochondrial fission, the molecular mechanism of the process is little understood. In the current study, we confirm the involvement of ER in mitochondrial fission and hypothesize the involvement of water channels or aquaporins (AQP) in the process. Previous studies demonstrate the presence of AQP both in the ER and mitochondrial membranes. Mitochondrial swelling has been observed following mitochondrial calcium overload, and studies report that chelation of cytosolic calcium induces extensive mitochondrial division at ER contact sites. Based on this information, the involvement of ER in mitochondrial division, possibly via water channels, is hypothesized. Utilizing a multi-faceted imaging approach consisting of atomic force microscopy on aldehyde-fixed and semi-dry cells, transmission electron microscopy, and immunofluorescence microscopy on live cells, the physical interactions between the two organelles are demonstrated. Mitochondrial fission following ER stress was abrogated with exposure of cells to the AQP inhibitor mercuric chloride, suggesting the involvement of AQP(s) especially AQP8 and AQP9 known to be present in the mitochondrial membrane, in mitochondrial fission.

Synthetic vector-based gene delivery systems continue to gain strength as viable alternatives to viral vectors due to safety and other concerns. DNA release dynamics is key to the understanding and control of gene delivery from nano-systems. Here we describe atomic force microscope application to the understanding of DNA release dynamics from bioreducible polycation-based nano-systems. The two nano-systems are polyplex nanoparticles and layer-by-layer films.

Synthetic vector-based gene delivery continues to gain strength as viable alternatives to viral vectors due to safety and other concerns. DNA release dynamics is key to the understanding and control of gene delivery from nanosystems. Here we describe atomic force microscope (AFM) application to the understanding of DNA release dynamics from bioreducible polycation-based nanosystems. The two nanosystems are polyplex nanoparticles and layer-by-layer (LbL) films.

Ultrathin organic multilayer films are appealing to scientists not only because they serve as molecular level models but also because they can be transformed into superlattices through successive deposition of alternating layers of different materials. Cationic bolaform amphiphile and anionic polyelectrolyte multilayers were self-assembled from their aqueous solutions via electrostatic attraction. The bolaform amphiphile layers are photopolymerizable by UV irradiation. The mechanical and surface electrical properties of the multilayer film were studied by surface force measurements, and the surface topography was studied by atomic force microscopy. We observed an average increase in film thickness of 75 with each amphiphile and polyelectrolyte double layer deposition, a molecularly smooth first anchoring amphiphile layer, and nonuniform polyelectrolyte layers with a surface roughness of 30 A. The surface roughness was preserved in the multilayer deposition process and was reduced by adding salt to the polyelectrolyte solution. Photopolymerization increases the integrity of the first anchoring layer as well as the subsequent multilayers. It took less than 5 min to dissolve a monomeric amphiphile film in chloroform, but immersion of the UV-irradiated film in chloroform for 2 h only resulted in partial removal of film materials. The multilayer film is quite fragile especially for the first few layers. Controlling of the monolayer structure by selective variation of the amphiphile chemical structure may help to optimize the photopolymerization process.

Insights into the three-dimensional (3D) organization and function of intracellular structures at nanometer resolution, holds the key to our understanding of the molecular underpinnings of cellular structure−function. Besides this fundamental understanding of the cell at the molecular level, such insights hold great promise in identifying the disease processes by their altered molecular profiles, and help determine precise therapeutic treatments. To achieve this objective, previous studies have employed electron microscopy (EM) tomography with reasonable success. However, a major hurdle in the use of EM tomography is the tedious procedures involved in fixing, high-pressure freezing, staining, serial sectioning, imaging, and finally compiling the EM images to obtain a 3D profile of sub-cellular structures. In contrast, the resolution limit of EM tomography is several nanometers, as compared to just a single or even sub-nanometer using the atomic force microscope (AFM). Although AFM has been hugely successful in 3D imaging studies at nanometer resolution and in real time involving isolated live cellular and isolated organelles, it has had limited success in similar studies involving 3D imaging at nm resolution of intracellular structure–function in situ. In the current study, using both AFM and EM on aldehyde-fixed and semi-dry mouse pancreatic acinar cells, new insights on a number of intracellular structure–function relationships and interactions were achieved. Golgi complexes, some exhibiting vesicles in the process of budding were observed, and small vesicles were caught in the act of fusing with larger vesicles, possibly representing either secretory vesicle biogenesis or vesicle refilling following discharge, or both. These results demonstrate the power and scope of the combined engagement of EM and AFM imaging of fixed semi-dry cells, capable of providing a wealth of new information on cellular structure–function and interactions.

We have prepared self-assembled monolayers of novel cationic bolaform amphiphiles on negatively charged substrates. Most of these amphiphiles form smooth, defect-free monolayers which can be used to reverse the substrate surface charge and thus allow subsequent adsorption of anionic molecules and construction of multilayers. Atomic force microscopy, surface force measurement, and surface plasmon spectroscopy were combined to probe the molecular orientation and ordering, mechanical properties, and surface electrical properties of the monolayers. In addition, the amphiphile aggregation behavior at an air-water interface was studied by surface tension measurement, and lyotropic phase behavior was studied by polarization microscopy. Our study suggests that monolayer interfacial and bulk properties can be controlled to a certain degree by selective variation of amphiphile chemical structure, in particular, the alkyl chain length and the type of counterions. A n increase in alkyl chain length assists close-packing at the liquid-solid interface and self-assembly in a liquid medium due to a favorable hydrophobic free energy change. Exchange of halide ions with the strongly associating salicylate ions reduces electrostatic repulsion between head groups and also favors self-assembly and close-packing. Our study suggests that it is possible to overcome the dominance and limitation of the substrate electrostatic effect on monolayer structure by using amphiphiles with a strong inherent tendency for close-packing. Our observations contribute to the understanding of two-dimensional topochemical photopolymerization, multilayer deposition of alternating surface charges, modification of hydrophilic surface electrical properties, and in general, the dependence of monolayer architecture on molecular chemical structure and intermolecular forces.

To investigate the effect of surface functionalization of mesoporous silica nanoparticles (MSN) on crystallization, loading, release and activity of mitoxantrone (MTX). Thiol-, amine-, and mixed thiol/amine-functionalized MSN were synthesized and characterized by electron microscopy, thermogravimetry, surface area analysis, elemental analysis and zeta potential. MTX loading and release kinetics were determined in phosphate and acetate buffers (pH 7.4 and 4.5). The crystalline state of MTX in MSN was determined by differential scanning calorimetry and X-ray diffraction. Cytotoxicity and activity of MTX loaded MSN were determined by MTS assay in MDA-MB-231 cells. Our results demonstrate that loading of MTX depends strongly on the type of surface functional groups in MSN. Thiol-MSN showed the highest MTX loading (18 % w/w) when compared with thiol/amine-MSN (6 % w/w) and amine-MSN (1 % w/w). MTX release was strongly dependent on the pH of the release medium and the type of surface functional group. MTX was found in the amorphous form when loaded in thiol-functionalized MSN. No significant effect of surface modification of MSN on particle toxicity was observed. MTX loaded in MSN exhibited comparable anticancer activity in vitro as free MTX. Surface modifications of MSN have significant effect on MTX crystallization and release behavior.

Monoand multilayers of photopolymerizable bolaform amphiphiles and polyelectrolytes self-assembled onto mica from aqueous solution were studied by surface force measurement and atomic force microscopy. Multiple layers of positively charged amphiphiles self-assemble if a negatively charged polyelectrolyte is inserted between them. The layers can be photopolymerized with a high-pressure UV lamp. The atomic force microscopy images indicate that the photopolymerized amphiphile monolayer has a higher degree of order than the unpolymerized monolayer, although the latter possesses some long-range order. Mechanical properties of the system measured by the surface force apparatus indicate that a photopolymerized layer is more robust and demonstrate that the rigidity and integrity of the first anchoring layer greatly influence the stability of the multilayer. The interaction between polyelectrolyte layers in water can be either attractive or repulsive depending on the coverage of the polyelectrolyte on the amphiphile layer. The mica separation of a pair of opposed monolayers in contact in the presence of water is surprisingly small (25 A) compared to the thickness (78 A) of a bilayer composed of fully extended amphiphiles.

This paper describes the formation of organic nanorods induced by monolayer-protected inorganic nanoparticles. Alkanes and alkane derivatives, such as n-carboxylic acids, self-assemble on highly oriented pyrolytic graphite (HOPG) into a persistent molecular packing structure that is dictated by the epitaxial interaction between the carbon chain plane and the HOPG basal plane. Carboxylic acids form 2-D crystalline layers consisting of nanostripe domains whose periodicity is one or two times the molecular chain length. However, when the molecular ordering occurs in the vicinity of a nanoparticle, this persistent HOPG-dominated nanostripe pattern is disrupted, and nanorods attached to the nanoparticles become the dominant structure. In order to understand the underlying mechanism of the nanoparticle-mediated nanorod formation, the effects of film-forming conditions, carboxylic acid chain length, nanoparticle size, and chemical composition of the nanoparticle are examined. It is determined that carboxylic acid nanorods can be induced by nanoparticles of different core materials including CdSe, CdS, and Au, as long as the protecting monolayer allows sufficient dispersion and colloidal stability of the nanoparticles in solution. A carboxylic chain length range amenable to the nanorod formation is identified, as is the relationship between the nanoparticle size and the number of nanorods per nanoparticle. This study contributes to the understanding of seed-mediated crystallization and molecular ordering. Moreover, it defines the parameters governing solution-based formation of hybrid nanostructures and nanopatterns incorporating dual functionality as defined by the inorganic nanoparticle and organic nanorod, respectively.

DNA release dynamics from layer-by-layer (LbL) films is an important aspect to consider with regards to localized gene delivery systems. The rate of DNA release and the condensation state of DNA during release are of particular interest in the field of gene delivery. A hyperbranched poly(amido amine) (RHB) containing bioreducible disulfide bonds is used to form interpolyelectrolyte complexes with DNA during LbL film assembly. During film disassembly, DNA is released in physiologic conditions due to the reducing nature of the RHB. Uncondensed DNA deposited on the surface was compared to DNA condensed by RHB in polyplex form by using two types of LbL films, RHB/DNA/RHB and polyplex terminated films, RHB/DNA/polyplex. LbL films with up to three layers are used in order to facilitate high-resolution atomic force microscopy (AFM) imaging. X-ray reflectivity, ellipsometry, and Fourier transform infrared spectroscopy are also used. The film disassembly, rearrangement, and release of molecules from the surface due to thiol-disulfide exchange is conducted in reducing dithiothreitol (DTT) solutions. Salt is found to accelerate the overall rate of film disassembly. Additionally, it was found that the polyplex layer disassembles faster than the DNA layer. The predominant intermediate structure is the toroid structure for the polyplex layer and the fiber bundle structure for the DNA layer during film disassembly. This study offers a simple means to modulate DNA release from LbL films by utilizing both condensed and uncondensed DNA in different layers. The study highlights nanostructures, toroids, and bundles as dominant intermediate DNA structures during DNA release from LbL films.

Surface forces measurements have been made between adsorbed layers on mica of a cationic polymer (Polymer JR-400) in distilled water, both in the absence and in the presence of the anionic surfactant sodium dodecylsulfate. In the absence of surfactant, the polymer was bound to the oppositely charged mica surface and exhibited hysteresis force curves which were monotorically repulsive up to a compression of 104 μN m−1. In the presence of surfactant hysteresis was also observed but while the compressing force curves were monotonically repulsive, the separating force curves showed a significant attraction between the layers. This suggests that bound surfactant may be inducing hydrophobic interactions between the esdsorbed layers.

Layer-by-layer (LbL) films were assembled on flexible stainless steel substrate using plasmid DNA and reducible hyperbranched poly(amido amine) (RHB) polycation. The films were characterized by XPS and their disassembly in reducing conditions confirmed by ellipsometry. Fibroblast and smooth muscle cell attachment and proliferation on DNA/RHB films were indistinguishable from those on control DNA/poly(ethylenimine) (PEI) films. In vitro transfection activity was evaluated using reporter plasmids encoding for secreted alkaline phosphatase (SEAP) and green fluorescent protein (GFP). DNA/RHB films showed higher and longer lasting transfection activity than control DNA/PEI films using SEAP plasmid. It was revealed through the use of GFP plasmid that DNA/RHB films transfected almost the entire cell population growing on the films. In vivo transfection activity was evaluated by subcutaneously implanting a stainless steel substrate coated with the DNA/RHB films containing SEAP plasmid DNA and measuring the levels of SEAP secreted into the blood circulation of rats. It was found that the plasma levels of SEAP peaked at approximately 160 ng SEAP/mL five days post-implantation.

This article describes the stability and reversibility of ultrathin films of N-isopropylacrylamide (NIPA)-vinylimidazole (VI)-poly(ethylene glycol) (PEG) graft terpolymer adsorbed at the solid-liquid interface upon temperature cycling from below to above its phase transition temperature. The coil-to-globule and globule-to-coil phase transitions were captured by in situ fluid tapping atomic force microscopy (AFM). The film thickness of 1 nm was determined by AFM, X-ray photoelectron spectroscopy, and X-ray reflectivity. The concentration required to reach full coverage was found to be higher when adsorption occurred below the phase transition temperature. From 23 to 42 degrees C, the adsorbed NIPA terpolymer film was observed to be molecularly smooth, corresponding to the close-packed structure of flexible polymer coils. Particles containing between one and a few globules appeared abruptly at the interface at 42-43 degrees C, the same temperature as the solution phase transition temperature, which was determined by dynamic light scattering. The size of the particles did not change with temperature, whereas the number of particles increased with increasing temperature up to 60 degrees C. The particles correspond to the collapsed and associated state of the globules. The film morphological changes were found to be reversible upon temperature cycling. Subtle differences were observed between dip-coated and spin-coated films that are consistent with a higher degree of molecular freedom for spin-coated films. The study contributes to the fundamental understanding and applications of smart ultrathin films and coatings.

Two-dimensional periodic structures with nanometer feature sizes have been widely used in many photonic devices. The profile and size of the nanostructure elements can greatly affect optical performances. Various practical subwavelength structures working in the visible and near infrared region have been fabricated using electron-beam writing or laser interference techniques. In this paper, we present a new technique which use nanosphere lithography (NSL) and reactive-ion etching to fabricate two-dimensional nanostructures with tunable nanoelement size and profile.

We use the self-assembled polystyrene nanosphere monolayer pattern to replace photoresist mask for the fabrication of 2D nanostructures on various substrates. The optical properties of these artificial structures are measured and compared with theoretical calculation.

Aspirin and 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine (DMPE) are deposited from their alcoholic mixed solution onto highly oriented pyrolytic graphite (HOPG) by spin coating. The film structure and morphology are characterized by atomic force microscopy (AFM). The barely soluble DMPE forms a highly oriented stripe phase as a result of its one-dimensional epitaxy with the HOPG lattice. The bilayer stripe pattern exposes the cross section of the lipid bilayer lamellae and enables the direct visualization of the molecular interactions of drug or biological molecules with either the hydrophobic or the hydrophilic part of the phospholipid bilayer. The bilayer pattern affects the aspirin molecular deposition and aggregation. AFM shows that the aspirin molecules prefer to deposit and aggregate along the aliphatic interior part of the bilayer pattern, giving rise to parallel dimer rods in registry with the underlying pattern. The nonpolar interactions between aspirin and the phospholipid bilayer are consistent with the lipophilic nature of aspirin. The bilayer pattern not only stabilizes the rodlike aggregate structure of aspirin at low aspirin concentration but also inhibits crystallization of aspirin at high aspirin concentration. Molecular models show that the width of the DMPE aliphatic chain interior can accommodate no more than two aspirin dimers. The bilayer confinement may prevent aspirin from reaching its critical nucleus size. This study illustrates a general method to induce a metastable or amorphous form of an active pharmaceutical ingredient (API) by chemical confinement under high undercooling conditions. Metastable and amorphous solids often display better solubility and bioavailability than the stable crystalline form of the API.

We report the first results of self-assembled nanostructures using colloids for antireflection optical coatings. Two-dimensional (2D) periodic nano-structures were made by using self-assembled 2D colloidal crystals on top of a transparent substrate. An atomic force microscope was used to evaluate the quality of the nanostructure. The feature size of the structures was around 105 nm. This sub-wavelength structure is equivalent to an artificial film on top of the substrate. The effective refractive index of the film is found to be around 1.3. Such a low-index materials is desired for anti-reflection coating to reduce Fresnal reflection. We have observed the reduced reflection from glass surfaces as well as enhanced transmission. Our calculated results agree well with experimental measurement.

The morphology and stability of small unilamellar egg yolk phosphatidylcholine (EggPC) liposomes modified with the Pluronic® copolymer (poly (oxyethylene)–poly (oxypropylene)–poly (oxyethylene) (PEO–PPO–PEO)) with different compositions on mica surface have been investigated using atomic force microscopy. Morphology studies reveal significant morphological changes of liposomes upon incorporating the Pluronic® copolymer. Bilayers are observed for Pluronic® with small hydrophilic (PEO) chain lengths such as L81 [(PEO)2(PPO)40(PEO)2] and L121 [(PEO)4(PPO)60(PEO)4]; bilayer and vesicle coexistence is observed for P85 [(PEO)26(PPO)39.5(PEO)26] and F87 [(PEO)61.1(PPO)39.7(PEO)61.1]; and stable vesicles are observed for F88 [(PEO)103.5(PPO)39.2(PEO)103.5], F127 [(PEO)100(PPO)65(PEO)100], and F108 [(PEO)132.6(PPO)50.3(PEO)132.6]. The micromechanical properties of Pluronic®-modified EggPC vesicles were studied by analyzing AFM approaching force curve. The bending modulus ( k c ) of the Pluronic®-modified EggPC vesicles increased several-fold compared with that of the pure EggPC vesicles. The significant difference is due to the enhanced rigidity of the EggPC vesicles as a result of the incorporation of PPO molecules and PEO chains. Based on the analysis of onset point by AFM and diameters of vesicles by light scattering, it was concluded that the favorable model to describe the polymer–bilayer interaction is the membrane-spanning model.

The micromechanical properties of pure and cholesterol modified egg yolk phosphatidylcholine (EggPC) vesicles prepared by sonication were studied by atomic force microscopy (AFM) on mica surface. The force curves between an AFM tip and an unruptured vesicle were obtained by contact mode. During approach, two repulsion regions with two breaks were observed. The slopes of the two repulsive force regimes for the pure EggPC vesicles are determined to be several times lower than that of EggPC/cholesterol vesicles. The elastic properties from force plot analysis based on the Hertzian model showed that Young's modulus (E) and the bending modulus (kc) of cholesterol-modified vesicles increased several-fold compared with pure EggPC vesicles. The significant difference is attributed to the enhanced rigidity of the EggPC vesicles as a result of the incorporation of cholesterol molecules. The behavior of cholesterol-modified vesicles upon adsorption is different from that in solution as revealed by mechanical properties. The results indicate that AFM can provide a direct method to measure the mechanical properties of adsorbed small liposomes and to detect the stability change of liposomes.

Maspin, an epithelial-specific member of the serine protease inhibitor superfamily, inhibits tumor invasion and metastasis. Overall maspin expression is downregulated or lost in invasive and metastatic carcinomas. Maspin subcellular distribution among the nuclear, cytoplasmic and extracellular compartments is differentially regulated during tumor progression. Extracellular maspin has been shown to inhibit tumor cell invasion and motility in vitro. Also, recombinant maspin was shown to inhibit endothelial cell tube formation in vitro and tumor-angiogenesis in vivo. To date, the mechanisms governing maspin trafficking remain unclear. In the current study, we aim to investigate the mechanism and biological significance of maspin secretion. Normal and tumor cells known to secrete maspin, were treated with or without drugs targeting classical or non-classical secretory pathways. The CM were collected and analyzed for soluble and exosome-associated proteins. We also utilized atomic force microscopy to characterize the physical characteristics of exosomes. We found maspin as a soluble protein in the CM. Maspin secretion was not inhibited by the drug treatments. In fact, maspin secretion increased under drug treatment targeting the classical secretory pathway. Furthermore, maspin was detected in the exosomes. Under drug treatment, the overall increase in maspin secretion was accompanied by an increase in detection of maspin in the exosomes. Based on the drug treatment-induced changes in maspin's secretion patterns, we speculate that maspin is secreted via a non-classical pathway. In addition, we provide the first evidence that maspin is secreted inclusively as both a free and an exosome-encapsulated molecule in normal and tumor cells. The existence of extracellular maspin as a free and an exosome-associated molecule implies a dual role for maspin in the tumor microenvironment. These novel findings are currently under investigation since the tumor suppressive activity of exosome-associated maspin may be of particular significance in cell-cell communication, and tumor suppressive activity of free maspin may be associated with extracellular matrix remodeling. Citation Format: Ivory S. Dean, Sijana Dzinic, Alexander Kaplun, Yi Zou, Guangzhao Mao, Shijie Sheng. Human prostate epithelial cells secrete the tumor suppressor maspin as a soluble and exosome-associated protein . [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5067. doi:10.1158/1538-7445.AM2013-5067

This communication describes a spin-coating method to nucleate organic molecular rods of uniform size from an inorganic nanoparticle at a solid surface. The particle-rod hybrid structure spontaneously forms when a film is spin coated from a mixed 2-propanol solution of arachidic acid (AA) and nanoparticles of cadmium selenide capped by mercaptoundecanoic acid (MUA-CdSe) on graphite. AFM images show that MUA-CdSe nanoparticles nucleate single crystalline rods of AA with a cross section of a single unit cell of the C-form. The solution-based process potentially allows the precise tuning of the wetting profile of the solution on the surface-attached nanoparticle, which provides the reservoir for the growth of the single crystalline rods. The results suggest that nanoparticles can be regarded as nanoseeds for the nucleation of guest crystals. It should be possible to further functionalize the AA rods by electrostatic complexation with metal or organic ions.

The failure of prosthesis after total joint replacement is due to the lack of early implant osseointegration. In this study polyvinyl alcohol-collagen-hydroxyapatite (PVA-Col-HA) electrospun nanofibrous meshes were fabricated as a biomimetic bone-like extracellular matrix for the modification of orthopedic prosthetic surfaces. In order to reinforce the PVA nanofibers, HA nanorods and Type I collagen were incorporated into the nanofibers. We investigated the morphology, biodegradability, mechanical properties and biocompatibility of the prepared nanofibers. Our results showed these inorganic-organic blended nanofibers to be degradable in vitro. The encapsulated nano-HA and collagen interacted with the PVA content, reinforcing the hydrolytic resistance and mechanical properties of nanofibers that provided longer lasting stability. The encapsulated nano-HA and collagen also enhanced the adhesion and proliferation of murine bone cells (MC3T3) in vitro. We propose the PVA-Col-HA nanofibers might be promising modifying materials on implant surfaces for orthopedic applications.

We have created nanospirals by self-assembly during droplet evaporation. The nanospirals, 60–70 nm in diameter, formed when solvent mixtures of methanol and m-cresol were used. In contrast, spin coating using only methanol as the solvent produced epitaxial films of stripe nanopatterns and using only m-cresol disordered structure. Due to the disparity in vapor pressure between the two solvents, droplets of m-cresol solution remaining on the substrate serve as templates for the self-assembly of carboxylic acid molecules, which in turn allows the visualization of solution droplet evaporation one molecule at a time.

A new approach to the generation of nanoparticle arrays in periodic as well as non-periodic fashions has been discovered based on reduction of oxidized nanoscroll/nanoribbon precursors in the transmission electron microscope (carbothermal reduction) or by hydrogen annealing. Arrays consisting of nickel arsenide nanoparticles of size 3-4 nm have been generated.