Surface Pressure-area Research Articles

Interfacial insights: [6]-Gingerol monolayers at the air-water interface and beyond

Ginger is a culinary spice with a millennia-old tradition due to its extensive therapeutic applications, recently validated by scientific studies. In particular [6]-Gingerol, a key active molecule in ginger, exhibits extraordinary capabilities in addressing a wide spectrum of health issues. However, its therapeutic potential is limited by its rather low bioavailability. The incorporation of [6]-Gingerol into membrane systems of liposomes, micelles, or exosomes is a promising strategy to overcome this limitation. In this contribution, we report the hitherto unexplored surface properties of [6]-Gingerol at the air-water interface. Our comprehensive study, which includes a detailed analysis of surface pressure and surface potential vs. area per molecule isotherms, surface compression modulus, and Brewster Angle Microscopy, demonstrates the capability of [6]-Gingerol to form Langmuir films. These films can be transferred onto solid substrates, forming remarkably homogeneous Langmuir-Blodgett films which have been characterized by Quartz Crystal Microbalance and Atomic Force Microscopy. This study may be of interest as it paves the way for future research on introducing [6]-Gingerol into membrane systems and transporting it into living cells.

Facile preparation and study of supramolecular architecture of an efficient nanocomposite LB film AHSM/SA based on azo-functionalized hockey stick-shaped mesogen at air-water and air-solid interface

Hockey stick-shaped mesogens are fascinating thermotropic liquid crystal systems owing to their exceptional supramolecular assembly properties and shape anisotropy compared to conventional rod-and bent-shaped mesogens. In this article, we present an investigation of the supramolecular organization of a new azo-functionalized hockey stick-shaped mesogen with stearic acid at the air-water interface and air-solid interfaces by applying the Langmuir-Blodgett film deposition method. The incorporation of stearic acid can change the molecular organization of azo-functionalized hockey stick-shaped mesogen at an aqueous interface through hydrophobic-hydrophobic interactions and form a supramolecular nanostructure at the solid interface. The interfacial nature of the Langmuir monolayer was studied by recording the isotherm (surface pressure area, π–A), which was further analyzed by using Brewster angle microscopy. The significant reduction in molecular area, increased surface pressure, and lower isotherm slope of the AHSM/SA composite mixture indicate the hybrid AHSM/SA monolayer's greater stability compared to pure AHSM. BAM images of the AHSM/SA composite signify nanostructure aggregates formed by the interaction of AHSM and SA molecules at the air-water interface. Field emission scanning electron microscopic analysis of composite films revealed the formation of supramolecular domains. The impact of changing the surface pressure and the number of depositions on the morphology of the composite film surface was monitored using field emission scanning electron microscopy. The supramolecular H-type aggregation of azo-functionalized hockey stick-shaped mesogen and stearic acid molecules in the composite LB film was characterized using UV–visible absorption and steady-state fluorescence spectroscopy. The adsorption of stearic acid onto azo-functionalized hockey stick-shaped mesogen via hydrophobic interactions was confirmed by Fourier transform infrared spectroscopy of the composite Langmuir Blodgett film. Further, Raman spectroscopy of the LB films of the AHSM/SA composites is distinct from the pristine film components due to the merging of signals at similar wave numbers for both SA and AHSM with a lack of typical packing pattern further supported by PXRD studies of the films.

Line tension and line entropy associated with the monolayer/trilayer boundary of smectic liquid crystal at the air-water interface.

Molecularly thin films of the smectic liquid crystal 4'-octyl-4-biphenylcarbonitrile (8CB) at the air-water interface phase separate into regions with different numbers of layers, in analogy with freestanding smectic liquid crystalline films. This paper reports the line tension associated with the boundary of coexisting trilayer and monolayer phases of in Langmuir films of 8CB at the air-water interface as a function of temperature and humidity and infers information on the boundary profile between the coexisting phases. Two complementary techniques are used to characterize the 8CB thin films: surface pressure-area isotherm and Brewster angle microscopy (BAM). We determine the line tension by stretching isolated domains from their equilibrium circular shape and analyzing the free relaxation with a hydrodynamic model. Then, we interpret the line tension vs temperature data in terms of an excess line entropy for the domain boundary, which requires careful consideration of the thermodynamics of inhomogeneous monolayer systems.

Nanostructured films of PM6 and Y6 and their assembly using Langmuir–Schaefer technique

This study investigates the molecular-level assembly and electronic properties of Langmuir and Langmuir–Schaefer (LS) films formed from Y6 (a non-fullerene electron acceptor) and PM6 (a wide bandgap electron donor polymer). We employ a variety of techniques including surface pressure-area isotherms, Brewster angle microscopy, ultraviolet-visible spectroscopy, Raman spectroscopy, and electrical characterizations to explore the behavior of these films. Our findings reveal that the films exhibit a tendency to aggregate and form non-homogeneous layers, which impacts their optical and electrical properties. The LS films show a significant sensitivity to solar radiation, which is evident from the changes in conductivity under illumination. This study highlights the potential of these materials in the development of photovoltaic applications, emphasizing the importance of molecular packing and film morphology in optimizing device performance.

PH-dependent interaction between acetaminophen and dioleoylphosphatidylcholine membranes

Abstract Acetaminophen may cause acute liver failure due to overdose. Understanding the processes of adsorption and incorporation of acetaminophen into cell membranes is crucial for elucidating the mechanisms of action and toxicity of acetaminophen. We investigated the interaction between acetaminophen and a model cell membrane (dioleoylphosphatidylcholine) using surface pressure–area isotherms. Acetaminophen was incorporated into the dioleoylphosphatidylcholine membrane under basic conditions, increasing the dioleoylphosphatidylcholine molecular area. The acetaminophen uptake was explained by the adsorption of hydroxide ions onto the lipid membrane and electrostatic interaction between acetaminophen and lipid molecules under basic conditions.

Effects of the ametryn pesticide on biomembrane models based on Langmuir films and giant unilamellar vesicles (GUVs)

The plasma membrane plays a crucial role in regulating various physiological processes within cells, controlling the flow of substances in and out of the cell. It primarily comprises lipids, oligosaccharides, sterols, and proteins, which are responsible for its functionalization. In this study, we utilized 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) to create mono and bilayers as mimetic systems for the lipid structure of cell plasma membranes. This approach constitutes the initial phase of comprehending the impact of contaminants on in vivo systems. Thus, the impact of the pesticide ametryn (AMT) on DPPC monolayers, which were formed using Langmuir films at the air/water interface, as well as on DPPC bilayers formed by giant unilamellar vesicles (GUVs), was investigated. The use of Brewster Angle Microscopy revealed a significant influence of AMT when in the water subphase on the morphology of DPPC aggregates in Langmuir monolayers, whose surface pressure vs. mean molecular area (π-A) isotherms are shifted to larger areas for higher AMT concentrations. Phase modulation infrared reflection-absorption spectroscopy indicated interactions between AMT and DPPC in Langmuir films, specifically involving the phosphate and choline DPPC head groups. Basically, the negatively charged hydrophilic portion of AMT (SCH3) would be oriented towards the DPPC choline group. At the same time, the AMT triazine ring would be positioned closer to the DPPC phosphate group, leading also to a slight disturb of the vertical orientation of the DPPC alkyl chains. In line with the findings from the monolayer experiments, the confocal microscopy images obtained through phase contrast revealed that the presence of AMT resulted in approximately 85 % of the DPPC GUVs losing their phase contrast. This loss can be attributed to the exchange between the inner and outer contents of the DPPC bilayer.

Detailed Study on the Interfacial Interaction between Different Polyoxometalates and Tetronic Block Copolymers Exploring the Langmuir-Blodgett Technique.

Polyoxometalates (POMs) interact with various biologically relevant entities. A basic understanding of this interaction is very important for various applications in the biological field. In this work, the focus is on the study of the interaction between tetronics and Keggin POMs. T701 and T90R4 are the two tetronics considered here; they have different solubilities in water due to different PPO/PEO ratios. The arrangement of PPO and PEO is also different with respect to the central ethylenediamine groups. Three different Keggin-type POMs, phosphomolybdic acid (PMA), phosphotungstic acid (PTA), and silicotungstic acid (STA), with different charge densities are chosen for an elaborate investigation using Langmuir-Blodgett technique. The observation is analyzed thoroughly, which shows both electrostatic interaction and adsorption of POMs on the PPO blocks of the tetronics due to the chaotropic effect, which is responsible for the binding of POMs (in subphase) with the tetronic monolayer. This interaction results in an expanded yet rigid monolayer for POM-tetronic association on the surface. Surface pressure vs mean molecular area isotherm is the key characterization to reach the conclusion. UV-vis spectroscopy, NMR, ITC, ellipsometric studies, FTIR, and SEM also serve as supportive characterization techniques.

Exploring proteins at soft interfaces and in thin liquid films – From classical methods to advanced applications of reflectometry

The history of the topic of proteins at soft interfaces dates back to the 19th century, and until the present day, it has continuously attracted great scientific interest. A multitude of experimental methods and theoretical approaches have been developed to serve the research progress in this large domain of colloid and interface science, including the area of soft colloids such as foams and emulsions. From classical methods like surface tension adsorption isotherms, surface pressure-area measurements for spread layers, and surface rheology probing the dynamics of adsorption, nowadays, advanced surface-sensitive techniques based on spectroscopy, microscopy, and the reflection of light, X-rays and neutrons at liquid/fluid interfaces offers important complementary sources of information. Apart from the fundamental characteristics of protein adsorption layers, i.e., surface tension and surface excess, the nanoscale structure of such layers and the interfacial protein conformations and morphologies are of pivotal importance for extending the depth of understanding on the topic. In this review article, we provide an extensive overview of the application of three methods, namely, ellipsometry, X-ray reflectometry and neutron reflectometry, for adsorption and structural studies on proteins at water/air and water/oil interfaces. The main attention is placed on the development of experimental approaches and on a discussion of the relevant achievements in terms of notable experimental results. We have attempted to cover the whole history of protein studies with these techniques, and thus, we believe the review should serve as a valuable reference to fuel ideas for a wide spectrum of researchers in different scientific fields where proteins at soft interface may be of relevance.

Surface Chemistry Study of Normal and Diseased Human Meibum Films Prior to and after Supplementation with Tear Mimetic Eyedrop Formulation

Ophthalmic nanoemulsions that can treat the deficiencies of meibum (MGS) in Meibomian gland disease and restore its functionality in the tear film are greatly sought. The Rohto Dry Aid (RDA) formulation employs TEARSHIELD TECHNOLOGYTM, which uses a multicomponent oil phase of polar and non-polar lipid-like molecules selected to mimic the profiles of healthy meibum. Thus, the interactions of RDA with “diseased” Meibomian (dMGS) films merit deeper analysis, as these interactions might offer important clues for both the development of new ocular formulations and the processes behind the therapeutic action of the nanoemulsions. Pseudobinary dMGS/RDA films were spread at the air–water surface of the Langmuir trough. Surface pressure-area isocycles and stress relaxations were used to access the layer’s response to blink-like cycling and dilatational viscoelasticity, respectively, while film morphology was recorded via Brewster angle microscopy. It was found that RDA is able to reverse the brittleness and to restore the stability of “diseased” MGS films and thus to revert the layer’s properties to the functionality of healthy Meibomian lipids. Therefore, in order to effectively treat dry eyes with MGS-oriented therapy, ophthalmic nanoemulsions warrant more research.

Closely Packed Core-Shell Micelle Structures of Double Hydrophilic Miktoarm Star Copolymers at the Air-Water Interface.

The aggregation behavior of amphiphilic block copolymers at the air-water interface has been extensively studied, but less attention was given to that of star copolymers. In this work, we studied the interfacial aggregation behavior of two double hydrophilic pH- and temperature-responsive miktoarm star copolymers of poly[di(ethylene glycol) methyl ether methacrylate]-poly[2-(dimethylamino)ethyl methacrylate] (PDEGMA3-PDMAEMA3 and PDEGMA4-PDMAEMA7, the subscripts denote arm numbers) with different molecular weights. The effects of subphase pH and temperature on the monolayer isotherms and hysteresis curves of the two star copolymers and the morphologies of their Langmuir-Blodgett (LB) films were studied by the Langmuir film balance technique and atomic force microscopy, respectively. At the air-water interface, the two star copolymers tend to form closely packed micelles. These micelles exhibit a core-shell structure, where the small hydrophobic core consists of cross-linker of ethylene glycol dimethacrylate (EGDMA) and the carbon backbones of PDEGMA and PDMAEMA arms and the short hydrophilic shell is composed of di(ethylene glycol) and tertiary amine side groups. With increasing subphase pH, the surface pressure versus molecular area isotherms shift toward larger mean molecular areas as a result of the enhanced interface adsorption of nonprotonated tertiary amine groups. The isotherm shift of PDEGMA3-PDMAEMA3 monolayers is primarily attributed to high density of tertiary amine groups in the shells, while that of PDEGMA4-PDMAEMA7 is mainly attributed to high density of di(ethylene glycol) groups in the shells. The hysteresis degrees in the monolayers of the two copolymers under alkaline and neutral conditions are greater than those under acidic conditions due to the decreased protonation degree of the tertiary amine groups. At 10 °C, the mobility of the shells is poor and the isotherms are located on the right. Above the lower critical solution temperature, di(ethylene glycol) groups contract, which causes a slight shift of the isotherms toward smaller mean molecular areas.

Understanding the Retention of Vaping Additives in the Lungs: Model Lung Surfactant Membrane Perturbation by Vitamin E and Vitamin E Acetate.

Deviations from the normal physicochemical and functional properties of pulmonary surfactants are associated with the incidence of lung injury and other respiratory disorders. This study aims to evaluate the alteration of the 2D molecular organization and morphology of pulmonary surfactant model membranes by the electronic cigarette additives α-tocopherol (vitamin E) and α-tocopherol acetate (vitamin E acetate), which have been associated with lung injury, termed e-cigarette or vaping-use-associated lung injury (EVALI). The model membranes used contained a 7:3 molar ratio of DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) and POPG (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol) to which α-tocopherol and α-tocopherol acetate were added to form mixtures of up to 20 mol % additive. The properties of the neat tocopherol additives and DPPC/POPG (7:3) mixtures with increasing molar proportions of additive were evaluated by surface pressure-area isotherms, excess area calculations, Brewster angle microscopy, grazing incidence X-ray diffraction, X-ray reflectivity, and atomic force microscopy. The addition of either additive alters the essential phase balance of the model pulmonary surfactant membrane by generating a greater proportion of the fluid phase. Despite this net fluidization, both tocopherol additives have space-filling effects on the liquid-expanded and condensed phases, yielding negative excess areas in the liquid-expanded phase and reduced tilt angles in the condensed phase. Both tocopherol additives alter the stability of the fluid phase, pushing the eventual collapse of this phase to higher surface pressures than the model membrane in the absence of an additive.

Mesoscale self-organization of polydisperse magnetic nanoparticles at the water surface.

In this study, we investigated the self-ordering process in Langmuir films of polydisperse iron oxide nanoparticles on a water surface, employing in situ x-ray scattering, surface pressure-area isotherm analysis, and Brewster angle microscopy. X-ray reflectometry confirmed the formation of a monolayer, while grazing incidence small-angle x-ray scattering revealed short-range lateral correlations with a characteristic length equal to the mean particle size. Remarkably, our findings indicated that at zero surface pressure, the particles organized into submicrometer clusters, merging upon compression to form a homogeneous layer. These layers were subsequently transferred to a solid substrate using the Langmuir-Schaefer technique and further characterized via scanning electron microscopy and polarized neutron reflectometry. Notably, our measurements revealed a second characteristic length in the lateral correlations, orders of magnitude longer than the mean particle diameter, with polydisperse particles forming circular clusters densely packed in a hexagonal lattice. Furthermore, our evidence suggests that the lattice constant of this mesocrystal depends on the characteristics of the particle size distribution, specifically the mean particle size and the width of the size distribution. In addition, we observed internal size separation within these clusters, where larger particles were positioned closer to the center of the cluster. Finally, polarized neutron reflectometry measurements provided valuable insights into the magnetization profile across the layer.

Hierarchical structure growth across different length scales in the two-phase coexistence region of myristic acid Langmuir monolayers: correlation of static and dynamic heterogeneities.

We investigated the hierarchical structure growth of myristic acid monolayers at the air-water interface across different length scales in the two-phase coexistence region of the first order liquid expanded (LE)-liquid condensed (LC) phase transition. A combined study of surface pressure-area (π-A) isotherm measurements with Brewster angle microscopy (BAM) observations was done at different temperatures. At the nanometer scale, the analysis of the π-A isotherm by application of a thermodynamic cluster equation allowed us to obtain the π dependence of cluster size (cluster distribution) in the LE-LC coexistence region. The cluster distributions showed a peak at the midpoint pressure of the transition. At higher temperature the larger nanocluster size was obtained at the transition midpoint. At the micrometer scale, BAM showed that LC domains have characteristic textures depending on the temperature. At low temperature domain density was lower and the average size of circular domains was larger. A large number of circular domains revealed a virtual boojum texture from the initial to the late stage of the transition. At the final stage some circular domains coalesced to form larger circular stripe domains and others coalesced to each other without the formation of stripe domains, finally resulting in a uniform texture over the entire water surface. At high temperature the domain texture was predominantly uniform, and a small number of domains only included straight line defects from the intermediate to the late stage of the transition. All domains coalesced to each other without the development of any texture including the stripe, different from the case at low temperature. The phase boundary line tension is highly likely to play a key role for understanding the hierarchical growth and coarsening (coalescence) process in the LE-LC transition between the different length scales from the nanometer to the micrometer scale consistently together.

Phospholipid Molecular Layer that Enhances Distinction of Odors Based on Artificial Sniffing.

We propose a novel odor-sensing system based on the dynamic response of phospholipid molecular layers for artificial olfaction. Organisms obtain information about their surroundings based on multidimensional information obtained from sniffing, i.e., periodic perturbations. Semiconductor- and receptor-based odor sensors have been developed previously. However, these sensors predominantly identify odors based on one-dimensional information, which limits the type of odor molecule they can identify. Therefore, the development of odor sensors that mimic the olfactory systems of living organisms is useful to overcome this limitation. In this study, we developed a novel odor-sensing system based on the dynamics of phospholipids that responds delicately to chemical substances at room temperature using multidimensional information obtained from periodic perturbations. Odor molecules are periodically supplied to the phospholipid molecular layer as an input sample. The waveform of the surface tension of the phospholipid molecular layer changes depending on the odor molecules and serves as an output. Such characteristic responses originating from the dynamics of odor molecules on the phospholipid molecular layer can be reproduced numerically. The phospholipid molecular layer amplified the information originating from the odor molecule, and the mechanism was evaluated by using surface pressure-area isotherms. This paper offers a platform for an interface-chemistry-based artificial sniffing system as an active sensor and a novel olfactory mechanism via physicochemical responses of the receptor-independent membranes of the organism.

Dense Monolayer Network Structures of Double Hydrophilic Hyperbranched Copolymers at the Air/Water Interface.

Influences of subphase pH and temperature on the interfacial aggregation behavior of two double hydrophilic hyperbranched copolymers of poly[oligo(ethylene glycol) methacrylate-co-(2-diisopropylamino)ethyl methacrylate] (P(OEGMA-co-DIPAEMA)) at the air/water interface are studied by the Langmuir film balance technique. Morphologies of their Langmuir-Blodgett (LB) films are characterized by atomic force microscopy (AFM). At the interface, P(OEGMA-co-DIPAEMA) copolymers tend to form a dense network structure of circular micelles composed of branching agent-connected carbon backbone cores and mixed shells of OEGMA and DIPAEMA segments (pendant groups). This network structure containing many honeycomb-like holes with diameters of 6-8nm is identified for the first time and clearly observed in the enlarged AFM images of their LB films. Under acidic conditions, surface pressure versus molecular area isotherms of the two copolymers in the low-pressure region show larger mean molecular area than those under neutral and alkaline conditions due to the lack of impediment from DIPAEMA segments. Upon further compression, each isotherm exhibits a wide pseudo-plateau, which corresponds to OEGMA segments being pressed into the subphase. Furthermore, the isotherms under neutral and alkaline conditions exhibit the lower critical solution temperature behavior of OEGMA segments, and the critical temperature is lower when the hyperbranched copolymer contains higher OEGMA content.

Host-Guest Sensing Interactions of Calixarene-Entrapped Para-Aminobenzoic Acid Using the Langmuir Technique

Calixarenes are frequently studied as the host supramolecule in drug carrier applications. The ability to encapsulate and control drug delivery is due to their unique structures with a hydrophobic upper rim and a hydrophilic lower rim. Para-aminobenzoic acid (PABA) is a drug used as the main ingredient in sunscreen products with photoallergic contact dermatitis effects. This study has been motivated by the necessity of developing a PABA sensor even at a deficient concentration. In this work, the uses of two calixarenes, calix[4]arene (C4) and calix[6]arene (C6), in entrapping the PABA drug have been studied using the Langmuir technique. In the Langmuir-Blodgett trough, calixarenes in solution form were prepared and spread on the subphase to form the Langmuir monolayer. The formation of Langmuir films by C4 and C6 has been investigated based on the surface pressure-area ( - ) isotherm and surface potential-area ( - ) isotherm recorded using Langmuir apparatus KSV 2000 System 2. The differences and changes of the isotherms with the presence of para-aminobenzoic acid (PABA) in the subphase during the formation of Langmuir films have been observed and studied. The interactions between calixarenes and PABA have been shown by the effective dipole moment ( ) of the calixarene-PABA complexes calculated based on the results using the Helmholtz equation. Host-guest interaction shown by the sensing of PABA by calixarenes happens most probably at the lower rim of calixarenes due to the amphiphilic property of calixarenes. The findings of this study can be applied to the potential application of drug sensors using C4 and C6.

Annexin A5 stabilizes matrix vesicle-biomimetic lipid membranes: unravelling a new role of annexins in calcification

Matrix vesicles are a special class of extracellular vesicles thought to actively contribute to both physiologic and pathologic mineralization. Proteomic studies have shown that matrix vesicles possess high amounts of annexin A5, suggesting that the protein might have multiple roles at the sites of calcification. Currently, Annexin A5 is thought to promote the nucleation of apatitic minerals close to the inner leaflet of the matrix vesicles’ membrane enriched in phosphatidylserine and Ca2+. Herein, we aimed at unravelling a possible additional role of annexin A5 by investigating the ability of annexin A5 to adsorb on matrix-vesicle biomimetic liposomes and Langmuir monolayers made of dipalmitoylphosphatidylserine (DPPS) and dipalmitoylphosphatidylcholine (DPPC) in the absence and in the presence of Ca2+. Differential scanning calorimetry and dynamic light scattering measurements showed that Ca2+ at concentrations in the 0.5–2.0 mM range induced the aggregation of liposomes probably due to the formation of DPPS-enriched domains. However, annexin A5 avoided the aggregation of liposomes at Ca2+ concentrations lower than 1.0 mM. Surface pressure versus surface area isotherms showed that the adsorption of annexin A5 on the monolayers made of a mixture of DPPC and DPPS led to a reduction in the area of excess compared to the theoretical values, which confirmed that the protein favored attractive interactions among the membrane lipids. The stabilization of the lipid membranes by annexin A5 was also validated by recording the changes with time of the surface pressure. Finally, fluorescence microscopy images of lipid monolayers revealed the formation of spherical lipid-condensed domains that became unshaped and larger in the presence of annexin A5. Our data support the model that annexin A5 in matrix vesicles is recruited at the membrane sites enriched in phosphatidylserine and Ca2+ not only to contribute to the intraluminal mineral formation but also to stabilize the vesicles’ membrane and prevent its premature rupture.

Surface Pressure-Area Mechanics of Water-Spread Poly(ethylene glycol)-Based Block Copolymer Micelle Monolayers at the Air-Water Interface: Effect of Hydrophobic Block Chemistry.

Amphiphilic block copolymer micelles can mimic the ability of natural lung surfactant to reduce the air-water interfacial tension close to zero and prevent the Laplace pressure-induced alveolar collapse. In this work, we investigated the air-water interfacial behaviors of polymer micelles derived from eight different poly(ethylene glycol) (PEG)-based block copolymers having different hydrophobic block chemistries to elucidate the effect of the core block chemistry on the surface mechanics of the block copolymer micelles. Aqueous micelles of about 30 nm in hydrodynamic diameter were prepared from the PEG-based block copolymers via equilibration-nanoprecipitation (ENP) and spread on the water surface using water as the spreading medium. Surface pressure-area isotherm and quantitative Brewster angle microscopy (QBAM) measurements were performed to investigate how the micelle/monolayer structures change during lateral compression of the monolayer; widely varying structural behaviors were observed, including the wrinkling/collapse of micelle monolayers and deformation and/or the desorption of individual micelles. By bivariate correlation regression analysis of surface pressure-area isotherm data, it was found that the rigidity and hydrophobicity of the hydrophobic core domain, which are quantified by glass-transition temperature (Tg) and water contact angle (θ) measurements, respectively, are coupled factors that need to be taken into account concurrently in order to control the surface mechanical properties of polymer micelle monolayers; micelles having rigid and strongly hydrophobic cores exhibited high surface pressure and a high compressibility modulus under high compression. High surface pressure and a high compressibility modulus were also found to be correlated with the formation of wrinkles in the micelle monolayer (visualized by Brewster angle microscopy (BAM)). From this study, we conclude that polymer micelles based on hydrophobic block materials having higher Tg and θ are more suitable for surfactant replacement therapy applications that require the therapeutic surfactant to produce a high surface pressure and modulus at the alveolar air-water interface.

Enhanced luminescence and electrical conductivity of polymer ultrathin films doped with TiO2 nanoparticles

The chemical polymerization method was used to prepare nanocomposite materials of polyaniline (PANi) and Titanium dioxide (TiO2) nanoparticles. Ultrathin films were deposited by using the Langmuir Blodgett (LB) Technique. Surface Pressure vs mean molecular area isotherms of nanocomposite materials showed an increase in maximum attained surface pressure with variation in nanoparticle doping concentration. Photoluminescence (PL) spectra were taken for LB multilayers deposited on a quartz substrate, an increase in the intensity of PL peaks with increasing doping concentration of TiO2 nanoparticles. The topography of LB monolayer film under atomic force microscopy (AFM) revealed that films were uniformly and densely deposited on the substrate. Phase imaging ensured the presence of nanoparticles in the polymer matrix. Conductive atomic force microscopy (C-AFM) was used to investigate the local electrical properties of nanocomposite LB films. Current-voltage characteristics showed variation in current with changing doping concentrations of TiO2 nanocomposite in PANi matrix. The work presents new insights in analyzing uniformly deposited ultrathin films of the composites which can be probed by C-AFM to reveal local electric properties by understanding topography-current correlation at the nanoscale. The conductive data analysis could be useful for understanding the current flow through the nanostructure surface.

Unveiling the mechanisms underlying photothermal efficiency of gold shell-isolated nanoparticles (AuSHINs) on ductal mammary carcinoma cells (BT-474)

Gold nanoparticles are valuable photothermal agents owing to their efficient photothermal conversion, photobleaching resistance, and potential surface functionalization. Herein, we combined bioinspired membranes with in vitro assays to elicit the molecular mechanisms of gold shell-isolated nanoparticles (AuSHINs) on ductal mammary carcinoma cells (BT-474). Langmuir and Langmuir-Schaefer (LS) films were handled to build biomembranes from BT-474 lipid extract. AuSHINs incorporation led to surface pressure-area (π-A) isotherms expansion, increasing membrane flexibility. Fourier-transform infrared spectroscopy (FTIR) of LS multilayers revealed electrostatic AuSHINs interaction with head portions of BT-474 lipid extract, causing lipid chain disorganization. Limited AuSHINs insertion into monolayer contributed to hydroperoxidation of the unsaturated lipids upon irradiation, consistently with the surface area increments of ca. 2.0%. In fact, membrane disruption of irradiated BT-474 cells containing AuSHINs was confirmed by confocal microscopy and LDH leakage, with greater damage at 2.2 × 1013 AuSHINs/mL. Furthermore, the decrease in nuclei dimensions indicates cell death through photoinduced damage.