Cholesterol Depletion from a Ceramide/Cholesterol Mixed Monolayer: A Brewster Angle Microscope Study

Engineered Polymer-siRNA Polyplexes Provide Effective Treatment of Lung Inflammation

Uncontrolled inflammation is responsible for acute and chronic diseases in the lung. Regulating expression of pro-inflammatory genes in pulmonary tissue using small interfering RNA (siRNA) is a promising approach to combatting respiratory diseases. However, siRNA therapeutics are generally hindered at the cellular level by endosomal entrapment of delivered cargo and at the organismal level by inefficient localization in pulmonary tissue. Here we report efficient anti-inflammatory activity in vitro and in vivo using polyplexes of siRNA and an engineered cationic polymer (PONI-Guan). PONI-Guan/siRNA polyplexes efficiently deliver siRNA cargo to the cytosol for highly efficient gene knockdown. Significantly, these polyplexes exhibit inherent targeting to inflamed lung tissue following intravenous administration in vivo. This strategy achieved effective (>70%) knockdown of gene expression in vitro and efficient (>80%) silencing of TNF-α expression in lipopolysaccharide (LPS)-challenged mice using a low (0.28 mg/kg) siRNA dosage.

Fluid Films as Models for Understanding the Impact of Inhaled Particles in Lung Surfactant Layers

Pollution is currently a public health problem associated with different cardiovascular and respiratory diseases. These are commonly originated as a result of the pollutant transport to the alveolar cavity after their inhalation. Once pollutants enter the alveolar cavity, they are deposited on the lung surfactant (LS) film, altering their mechanical performance which increases the respiratory work and can induce a premature alveolar collapse. Furthermore, the interactions of pollutants with LS can induce the formation of an LS corona decorating the pollutant surface, favoring their penetration into the bloodstream and distribution along different organs. Therefore, it is necessary to understand the most fundamental aspects of the interaction of particulate pollutants with LS to mitigate their effects, and design therapeutic strategies. However, the use of animal models is often invasive, and requires a careful examination of different bioethics aspects. This makes it necessary to design in vitro models mimicking some physico-chemical aspects with relevance for LS performance, which can be done by exploiting the tools provided by the science and technology of interfaces to shed light on the most fundamental physico-chemical bases governing the interaction between LS and particulate matter. This review provides an updated perspective of the use of fluid films of LS models for shedding light on the potential impact of particulate matter in the performance of LS film. It should be noted that even though the used model systems cannot account for some physiological aspects, it is expected that the information contained in this review can contribute on the understanding of the potential toxicological effects of air pollution.

Probing Physical Properties of the Cellular Membrane in Senescent Cells by Fluorescence Imaging

Cellular senescence is the irreversible cell cycle arrest in response to various types of stress. Although the plasma membrane and its composition are significantly affected by cellular senescence, detailed studies on the physical properties of the plasma membrane have shown inconclusive results. In this study, we utilized both ensemble and single-molecule fluorescence imaging to investigate how membrane properties, such as fluidity, hydrophobicity, and ganglioside GM1 level are affected by cellular senescence. The diffusion coefficient of lipid probes, as well as the type of diffusion determined by an exponent α, which is the slope of the log-log plot of mean squared displacement as a function of time lag, were analyzed. We found that the number of molecules with a lower diffusion coefficient increased as cells became senescent. The changes in the population with a lower diffusion coefficient, observed after methyl-β-cyclodextrin treatment, and the increase in ceramide levels, detected using a ceramide-specific antibody, suggest that ceramide-rich lipid rafts were enhanced in senescent cells. Our results emphasize the importance of membrane properties in cellular senescence and might serve as a base for in-depth studies to determine how such domains facilitate the signaling pathway specific to cellular senescence.

Cyclodextrin-based Pickering emulsions: functional properties and drug delivery applications

Cyclodextrins (CDs) are biocompatible, cyclic oligosaccharides that are widely used in various industrial applications and have intriguing interfacial science properties. While CD molecules typically have low surface activity, they are capable of stabilizing emulsions by inclusion complexation of oil-phase components at the oil/water interface, which results in Pickering emulsion formation. Such surfactant-free formulations have gained considerable attention in recent years, owing to their enhanced physical stability, improved tolerability, and superior environmental compatibility compared to conventional, surfactant-based emulsions. In this review, we critically describe the latest insights into the molecular mechanisms involved in CD stabilization of Pickering emulsions, including covering practical aspects such as methods to prepare CD-based Pickering emulsions, lipid encapsulation, and relevant stability issues. In addition, the rheological and textural features of CD-based Pickering emulsions are discussed and particular attention is focused on promising examples for drug delivery, cosmetic, and nutraceutical applications. The functionality of currently developed CD-based Pickering emulsions is also summarised, including examples such as antifungal uses, and we close by discussing emerging possibilities to utilize the molecular encapsulation of CD-based emulsions for translational medicine applications in the antiviral and antibacterial spaces.

Characterization of hydroxypropyl-beta-cyclodextrins used in the treatment of Niemann-Pick Disease type C1

2-Hydroxypropyl-beta-cyclodextrin (HPβCD) has gained recent attention as a potential therapeutic intervention in the treatment of the rare autosomal-recessive, neurodegenerative lysosomal storage disorder Niemann-Pick Disease Type C1 (NPC1). Notably, HPβCD formulations are not comprised of a single molecular species, but instead are complex mixtures of species with differing degrees of hydroxypropylation of the cyclodextrin ring. The degree of substitution is a critical aspect of the complex mixture as it influences binding to other molecules and thus could potentially modulate biological effects. VTS-270 (Kleptose HPB) and Trappsol^® Cyclo^™ are HPβCD products under investigation as novel treatments for NPC1. The purpose of the present work is to compare these two different products; analyses were based on ion distribution and abundance profiles using mass spectrometry methodology as a means for assessing key molecular distinctions between products. The method incorporated electrospray ionization and analysis with a linear low-field ion mobility quadrupole time-of-flight instrument. We observed that the number of hydroxypropyl groups (the degrees of substitution) are substantially different between the two products and greater in Trappsol Cyclo than in VTS-270. The principal ions of both samples are ammonium adducts. Isotope clusters for each of the major ions show doubly charged homodimers of the ammonium adducts. In addition, both products show doubly charged homodimers from adduction of both a proton and ammonium. Doubly charged heterodimers are also present, but are more intense in Trappsol Cyclo than in VTS-270. Based on the analytical differences observed between VTS-270 and Trappsol Cyclo with respect to the degree of substitution, the composition and fingerprint of the complex mixture, and the impurity profiles, these products cannot be considered to be the same; the potential biological and clinical implications of these differences are not presently known.

Molecular dynamics simulations and Kelvin probe force microscopy to study of cholesterol-induced electrostatic nanodomains in complex lipid mixtures

The molecular arrangement of lipids and proteins within biomembranes and monolayers gives rise to complex film morphologies as well as regions of distinct electrical surface potential, topographical and electrostatic nanoscale domains. To probe these nanodomains in soft matter is a challenging task both experimentally and theoretically. This work addresses the effects of cholesterol, lipid composition, lipid charge, and lipid phase on the monolayer structure and the electrical surface potential distribution. Atomic force microscopy (AFM) was used to resolve topographical nanodomains and Kelvin probe force microscopy (KPFM) to resolve electrical surface potential of these nanodomains in lipid monolayers. Model monolayers composed of dipalmitoylphosphatidylcholine (DPPC), 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), 1,2-dioleoyl-sn-glycero-3-[phospho-rac-(3-lysyl(1-glycerol))] (DOPG), and cholesterol were studied. It is shown that cholesterol changes nanoscale domain formation, affecting both topography and electrical surface potential. The molecular basis for differences in electrical surface potential was addressed with atomistic molecular dynamics (MD). MD simulations are compared the experimental results, with 100 s of mV difference in electrostatic potential between liquid-disordered bilayer (L_d, less cholesterol and lower chain order) and a liquid-ordered bilayer (L_o, more cholesterol and higher chain order). Importantly, the difference in electrostatic properties between L_o and L_d phases suggests a new mechanism by which membrane composition couples to membrane function.