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Canonical Wnt signaling is critical for melanocyte lineage commitment and melanoma development. RAD6B, a ubiquitin-conjugating enzyme critical for translesion DNA synthesis, potentiates β-catenin stability/activity by inducing proteasome-insensitive polyubiquitination. RAD6B expression is induced by β-catenin, triggering a positive feedback loop between the two proteins. RAD6B function in melanoma development/progression was investigated by targeting RAD6B using CrispR/Cas9 or an RAD6-selective small-molecule inhibitor #9 (SMI#9). SMI#9 treatment inhibited melanoma cell proliferation but not normal melanocytes. RAD6B knockout or inhibition in metastatic melanoma cells downregulated β-catenin, β-catenin–regulated microphthalmia-associated transcription factor (MITF), sex-determining region Y-box 10, vimentin proteins, and MITF-regulated melan A. RAD6B knockout or inhibition decreased migration/invasion, tumor growth, and lung metastasis. RNA-sequencing and stem cell pathway real-time RT-PCR analysis revealed profound reductions in WNT1 expressions in RAD6B knockout M14 cells compared with control. Expression levels of β-catenin–regulated genes VIM, MITF-M, melan A, and TYRP1 (a tyrosinase family member critical for melanin biosynthesis) were reduced in RAD6B knockout cells. Pathway analysis identified gene networks regulating stem cell pluripotency, Wnt signaling, melanocyte development, pigmentation signaling, and protein ubiquitination, besides DNA damage response signaling, as being impacted by RAD6B gene disruption. These data reveal an important and early role for RAD6B in melanoma development besides its bonafide translesion DNA synthesis function, and suggest that targeting RAD6B may provide a novel strategy to treat melanomas with dysregulated canonical Wnt signaling.

A wide range of cellular activities including protein folding and cell secretion, such as neurotransmission or insulin release, are all governed by intracellular pH homeostasis, underscoring the importance of pH on critical life processes. Nano- scale pH measurements of cells and biomolecules therefore hold great promise in understanding a plethora of cellular functions, in addition to disease detection and therapy. In the current study, a novel approach using cadmium telluride quantum dots (CdTeQDs) as pH sensors, combined with fluorescent imaging, spectrofluorimetry, atomic force microscopy (AFM), and Western blot analysis, enabled the study of intracellular pH dynamics at 1 milli-pH sensitivity and 80nm pixel resolution, during insulin secretion. Additionally, the pH-dependent interaction between membrane fusion proteins, also called the soluble N-ethylmaleimide-sensitive factor activating protein receptor (SNARE), was determined. Glucose stimulation of CdTeQD-loaded insulin secreting Min-6 mouse insulinoma cell line demonstrated the initial (5-6min) intracellular acidification reflected as a loss in QD fluorescence, followed by alkalization and a return to resting pH in 10min. Analysis of the SNARE complex in insulin secreting Min-6 cells demonstrated an initial gain followed by loss of complexed SNAREs in 10min. Stabilization of the SNARE complex at low intracellular pH is further supported by results from studies utilizing both native and AFM measurements of liposome-reconstituted recombinant neuronal SNAREs, providing a molecular understanding of the role of pH during cell secretion.

Respiratory complications in patients with spinal cord injury (SCI) are common and can have a negative impact on the quality of patients' lives. Previously, we found that intradiaphragmatic administration of the nanoconjugate-bound A1 adenosine receptor antagonist, 1,3-dipropyl-8-cyclopentylxanthine (DPCPX) induced recovery of diaphragm function following SCI in rats. When administered immediately following the injury, recovery was observed as early as 3days following SCI and it persisted until the end of the study, 28days after the drug delivery. The recovery was observed using diaphragmatic electromyography (EMG) as well as phrenic nerve recordings; both of which were conducted under anesthetized conditions. Confounding effects of anesthetic may make data interpretation complex in terms of the impact on overall ventilatory function and clinical relevance. The objective of the present study was to test the hypothesis that intradiaphragmatic administration of nanoconjugate-bound DPCPX, enhances recovery of ventilation following SCI in the unanesthetized rat. To that end, Sprague-Dawley rats underwent C2 spinal cord hemisection (C2Hx) on day 0 and received either: (i) 0.15μg/kg of nanoconjugate-bound DPCPX or (ii) vehicle control (50μl distilled water). To assess ventilation, unrestrained whole body plethysmography (WBP) was performed on day 0 (immediately before the surgery) and 3, 7, 14, 21 and 28days following the SCI. Frequency, tidal volume, and minute ventilation data were analyzed in two minute bins while the animal was calm and awake. We found that a single administration of the nanoconjugate-bound A1 adenosine receptor antagonist facilitated recovery of tidal volume and minute ventilation following SCI. Furthermore, the treatment attenuated SCI-associated increases in respiratory frequency. Taken together, this study suggests that the previously observed DPCPX nanoconjugate-induced recovery in diaphragmatic and phrenic motor outputs may translate to a clinically meaningful improvement in ventilatory function in patients with SCI.

The current study was aimed to develop a targeted dendrimer formulation of 3, 4-difluorobenzylidene curcumin (CDF) and evaluate its potential in CD44 targeted therapy for pancreatic cancer. Using amine terminated fourth generation poly(amidoamine) (PAMAM) dendrimer nanocarrier and hyaluronic acid (HA) as a targeting ligand, we engineered a CD44-targeted PAMAM dendrimer (HA-PAMAM) formulation of CDF. The resulting dendrimer nanosystem (HA-PAMAM-CDF) had a particle size and surface charge of 9.3 ± 1.5 nm and -7.02 ± 9.53 mV, respectively. When CD44 receptor overexpressing MiaPaCa-2 and AsPC-1 human pancreatic cancer cells were treated with HA-PAMAM-CDF, a dose-dependent cytotoxicity was observed. Furthermore, blocking the CD44 receptors present on the MiaPaCa-2 cells using free excess soluble HA prior to treatment with HA-PAMAM-CDF nano-formulation resulted in 1.71 fold increase in the IC50 value compared to non-targeted formulation (PAMAM-CDF), confirming target specificity of HA-PAMAM-CDF. Additionally, HA-PAMAM-CDF formulation when compared to PAMAM-CDF, displayed higher cellular uptake in MiaPaCa-2 cancer cell lines as shown by fluorescence studies. In summary, the novel CD44 targeted dendrimer based nanocarriers appear to be proficient in mediating site-specific delivery of CDF via CD44 receptors, with an improved therapeutic margin and safety.

Lack of a system for genetic manipulation of Chlamydia trachomatis has been a key challenge to advancing understanding the molecular genetic basis of virulence for this bacterial pathogen. We developed a non-viral, dendrimer-enabled system for transformation of this organism and used it to characterize the effects of inserting the common 7.5 kbp chlamydial plasmid into strain L2(25667R), a C. trachomatis isolate lacking it. The plasmid was cloned in pUC19 and the clone complexed to polyamidoamine dendrimers, producing ∼83 nm spherical particles. Nearly confluent McCoy cell cultures were infected with L2(25667R) and reference strain L2(434). At 16 h post-infection, medium was replaced with dendrimer–plasmid complexes in medium lacking additives (L2(25667R)) or with additive-free medium alone (L2(434)). Three h later complexes/buffer were removed, and medium was replaced; cultures were harvested at various times post-transformation for analyses. Real time PCR and RT-PCR of nucleic acids from transformed cultures demonstrated plasmid replication and gene expression. A previous report indicated that one or more plasmid-encoded product govern(s) transcription of the glycogen synthase gene (glgA) in standard strains. In L2(25667R) the gene is not expressed, but transformants of that strain given the cloned chlamydial plasmid increase glgA expression, as does L2(434). The cloned plasmid is retained, replicated, and expressed in transformants over at least 5 passages, and GFP is expressed when transformed into growing L2(25667R). This transformation system will allow study of chlamydial gene function in pathogenesis.

The chlamydiae are important human pathogens. Lack of a genetic manipulation system has impeded understanding of the molecular bases of virulence for these bacteria. We developed a dendrimer-enabled system for transformation of chlamydiae and used it to characterize the effects of inserting the C . trachomatis plasmid into C . pneumoniae , which lacks any plasmids. The plasmid was cloned into modified yeast vector pEG(KG) and the clone complexed to polyamidoamine dendrimers, producing 50–100nm spherical particles. HEp-2 cell cultures were infected with C . pneumoniae strain AR-39. Twenty-four hours later, medium was replaced for 3hours with dendrimer-plasmid complexes, then removed and the medium replaced. Cultures were harvested at various times post-transformation. Real-time PCR and RT-PCR of nucleic acids from transformed cultures demonstrated plasmid replication and gene expression. The cloned plasmid was replicated and expressed in transformants over 5 passages. This system will allow study of chlamydial gene function, allowing development of novel dendrimer-based therapies. From the Clinical Editor This team of investigators developed a dendrimer-enabled system for transformation of chlamydiae and successfully utilized it to characterize the effects of inserting the C. trachomatis plasmid into C. pneumonia . This system will allow study of chlamydial gene function, allowing development of novel dendrimer-based therapies.

A long-term effect of chronically implanted neural electrodes is the formation of a glial scar made up of reactive astrocytes, microglia and the matrix proteins they generate. Studies have shown glial fibrillary acidic protein (GFAP) and cytokines interleukin-1beta (IL-1β), tumor necrosis factor alpha (TNFα), and transforming growth factor beta 1 (TGFβ1) are involved with the initial and modulation phases of reactive astrogliosis. In the present study, nanopatterning of polydimethylsiloxane (PDMS) was attempted as a method for reducing the inflammatory response of glial cells. A unique feature of this study is the use of in vitro brain slice cultures (organotypic cultures) in order to more accurately depict the native response. The aim of the study was to determine whether nanotopography could reduce inflammatory signals typically resultant from neural electrode implantation. Specifically, observation of cell alignment and surveillance of GFAP, IL-1β, TNFα, and TGFβ1 gene expression around the PDMS pins was performed. Results of this study confirm nanopatterning not only influences cell morphology, but some of the molecular signals as well. These results collectively indicate nanopatterning improves the biocompatibility of PDMS by reducing inflammatory markers such as GFAP, IL-1β, TGFβ1 and TNFα compared to the non-patterned PDMS pins.

Drug resistance limits the success of many anticancer drugs. Reduced accumulation of the drug at its intracellular site of action because of overexpression of efflux transporters such as P-glycoprotein (P-gp) is a major mechanism of drug resistance. In this study, we investigated whether photodynamic therapy (PDT) using methylene blue, also a P-gp inhibitor, can be used to enhance doxorubicin-induced cytotoxicity in drug-resistant tumor cells. Aerosol OT (AOT)-alginate nanoparticles were used as a carrier for the simultaneous cellular delivery of doxorubicin and methylene blue. Methylene blue was photoactivated using light of 665 nm wavelength. Induction of apoptosis and necrosis following treatment with combination chemotherapy and PDT was investigated in drug-resistant NCI/ADR-RES cells using flow cytometry and fluorescence microscopy. Effect of encapsulation in nanoparticles on the intracellular accumulation of doxorubicin and methylene blue was investigated qualitatively using fluorescence microscopy and was quantitated using HPLC. Encapsulation in AOT-alginate nanoparticles significantly enhanced the cytotoxicity of combination therapy in resistant tumor cells. Nanoparticle-mediated combination therapy resulted in a significant induction of both apoptosis and necrosis. Improvement in cytotoxicity could be correlated with enhanced intracellular and nuclear delivery of the two drugs. Further, nanoparticle-mediated combination therapy resulted in significantly elevated reactive oxygen species (ROS) production compared to single drug treatment. In conclusion, nanoparticle-mediated combination chemotherapy and PDT using doxorubicin and methylene blue was able to overcome resistance mechanisms and resulted in improved cytotoxicity in drug-resistant tumor cells.

Layer-by-layer (LbL) assemblies of DNA and polycations on the surface of colloidal templates can be used for gene delivery. Plasmid DNA encoding for secreted alkaline phosphatase (SEAP) was used to deposit LbL films with poly(ethylenimine) (PEI) on the surface of polystyrene and poly(lactide-co-glycolide) microparticles. The formation of LBL films was confirmed by zeta potential analysis and fluorescence and atomic force microscopy techniques. The LbL particles were rapidly internalized in a dose-dependent manner by J774.1 murine macrophages. Transfection activity of the LbL particles was evaluated in J774.1 cells using three different doses (5, 10, 25 particle per cell). The levels of SEAP expression increased with increasing dose but were lower than transfection levels mediated by control PEI/DNA polyplexes at corresponding DNA doses. The LbL particles reported here present a promising platform for delivery of DNA to phagocytic cells.

ENATBIO: a National Conference on Emerging Nanoscience in Technology and Biomedicine Guangzhao Mao, PhD, Golam Newaz, Chiming Wei, MD, PhD⁎ Department of Chemical Engineering and Materials Science, Wayne State University, Detroit, Michigan, USA Department of Mechanical Engineering, Wayne State University, Detroit, Michigan, USA Department of Surgery, Johns Hopkins University School of Medicine, Ellicott City, Maryland, USA

Phages are promising alternatives to antibodies as the biorecognition element in a variety of biosensing applications. In this study, a monolayer of bacteriophage P22 whose tailspike proteins specifically recognize Salmonella serotypes was covalently bound to glass substrates through a bifunctional cross linker 3-aminopropyltrimethoxysilane. The specific binding of Salmonella typhimurium to the phage monolayer was studied by enzyme-linked immunosorbent assay and atomic force microscopy. Escherichia coli and a Gram-positive bacterium Listeria monocytogenes were also studied as control bacteria. The P22 particles show strong binding affinity to Salmonella typhimurium. In addition, the dried P22 monolayer maintained 50% binding capacity to Salmonella typhimurium after a one-week storage time. This is a promising method to prepare phage monolayer coatings on surface plasmon resonance and acoustic biosensor substrates in order to utilize the nascent phage display technology.

Poor drug encapsulation efficiency and rapid release of the encapsulated drug limit the use of nanoparticles in biomedical applications involving water-soluble drugs. We have developed a novel polymer-surfactant nanoparticle formulation, using the anionic surfactant Aerosol OT (AOT) and polysaccharide polymer alginate, for sustained release of water-soluble drugs. Particle size of nanoparticles, as determined by atomic force microscopy and transmission electron microscopy, was in the range of 40-70 nm. Weakly basic molecules like methylene blue, doxorubicin, rhodamine, verapamil, and clonidine could be encapsulated efficiently in AOT-alginate nanoparticles. In vitro release studies with basic drug molecules indicate that nanoparticles released 60-70% of the encapsulated drug over 4 weeks, with near zero-order release during the first 15 days. Studies with anionic drug molecules demonstrate poorer drug encapsulation efficiency and more rapid drug release than those observed with basic drugs. Further studies investigating the effect of sodium concentration in the release medium and the charge of the drug suggest that calcium-sodium exchange between nanoparticle matrix and release medium and electrostatic interaction between drug and nanoparticle matrix are important determinants of drug release. In conclusion, we have formulated a novel surfactant-polymer drug delivery carrier demonstrating sustained release of water-soluble drugs.

This paper reports the disassembly of layer-by-layer (LbL) films of plasmid DNA and a reducible cationic polypeptide. To utilize a reducing microenvironment of cellular plasma membrane as a potential trigger, LbL films are assembled to contain both DNA and the TAT-based polypeptide (PTAT) with reducible disulfide bonds in the backbone. The assembly and disassembly processes are monitored by goniometry, ellipsometry, and atomic force microscopy (AFM). The structure of the PTAT films is compared with that of non-reducible poly( l -lysine) (PLL) films. Both PTAT and PLL films exhibit exponential growth but with the contact angle alternating between characteristic values. Ellipsometry and AFM show a gradual and complete disassembly of the PTAT but not the PLL films in a 24 h period in the reducing environment in vitro. This study suggests a potential of using reducible LbL films for controlled DNA delivery.

Increasingly, organosilane self-assembled monolayers (SAMs) are used to modify the surfaces of silicon-based sensors and atomic force microscope (AFM) probes. Organosilane SAMs are preferred due to their fast and easy preparation, stability, and applicability to a wide range of substrates. The traditional dip coating method from solution often yields ill-defined particulate aggregates on the two-dimensional SAM. The presence of such three-dimensional aggregates seriously reduces the performance of miniaturized biosensor devices and AFM probes. It is difficult to control the amount of water in solution-based deposition. This paper describes a chemical vapor deposition (CVD) method to deposit octadecyltrichlorosilane (OTS) monolayers on silicon wafers and AFM probes under vacuum condition. OTS coated surfaces with static water contact angle ranging from 20° to 107° can be obtained by controlling the deposition conditions. The silicon substrates and AFM probes after CVD are characterized by AFM, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and contact angle goniometry. The OTS monolayer is in a uniform low-density state below 65%. Above 65%, densely packed crystalline-like domains start to form. It takes 24 h to reach the adsorption saturation. The time span in the CVD deposition is much longer than the solution case and thus allowing precise variation of the substrate hydrophobicity for biosensor applications.

Temperature- and pH-controlled association of terpolymers of N -isopropylacrylamide (NIPA) with 1-vinylimidazole (VI) and polyethylene glycol (PEG) has been investigated by light scattering and atomic force microscopy (AFM) in situ. The polymers contained 0–15 mol% VI and 0–2 mol% PEG. The phase transition temperatures ( T p ) have been in the range of 32–45 °C and exhibited significant dependence on the pH of solution in the pH range between 5 and 8. The T p of the polymers increased with increasing VI content and with decreasing pH, confirming major effect of VI ionization status on T p . The presence of PEG grafts in the polymer structure had augmenting effect on the magnitude of pH-responsiveness and on the pH-independent colloidal stability of the polymer particles formed above T p . Incorporation of VI into the polymer structure had similar, but pH-dependent effect on colloidal stabilization of the polymer particles. The size of the particles formed after the phase transition is driven by the association of the collapsed NIPA segments in the globule conformation and it decreased with decreasing pH. The phase transition temperature of the polymers could be adjusted to increase from temperatures below, to temperatures above body temperature upon decreasing pH from 7 to 6, suggesting that such polymers could provide a material platform for a variety of biomedical applications. AFM analysis in situ showed a fully reversible formation of particles in the solutions of the polymers above their T p .

Use of bioactive cationic peptides as gene carriers is limited by instability of their DNA complexes in vivo and by the loss of their biological activity due to undesired interactions of their bioactive parts with the DNA. To overcome the two major limitations, biodegradable high-molecular-weight form of TAT peptide (POLYTAT) sensitive to cellular redox-potential gradients was synthesized in this study by oxidative polycondensation. Physicochemical and transfection properties of DNA polyplexes based on POLYTAT were investigated and compared with polyplexes based on TAT polymer prepared by in situ template-assisted polymerization. Physicochemical properties of TAT-based polyplexes were affected by the molecular weight and method of polymerization of the TAT peptide. All TAT-based DNA polyplexes exhibited reduced cytotoxicity when compared with control polyethylenimine (PEI) polyplexes. Polyplexes based on both high-molecular-weight TAT polypeptides exhibited increased transfection efficiency compared to control TAT peptide but lower than that of PEI polyplexes. The evidence shows that transfection activity of TAT-based polyplexes is strongly dependent on the presence of chloroquine and therefore suggests that TAT polyplexes are internalized by an endocytosis. Overall, high-molecular-weight reducible polycations based on bioactive peptides has the potential as versatile carriers of nucleic acids that display low cytotoxicity and can prove to be especially beneficial in cases that require surface presentation of membrane-active or cell-specific targeting peptides.

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.

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

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.

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.

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.