The pandemic emergency determined by the spreading worldwide of the SARS-CoV-2 virus has focused the scientific and economic efforts of the pharmaceutical industry and governments on the possibility ...to fight the virus by genetic immunization. The genetic material must be delivered inside the cells by means of vectors. Due to the risk of adverse or immunogenic reaction or replication connected with the more efficient viral vectors, non-viral vectors are in many cases considered as a preferred strategy for gene delivery into eukaryotic cells. This paper is devoted to the evaluation of the gene delivery ability of new synthesized
bis-pyridinium surfactants with six methylene spacers, both hydrogenated and fluorinated, in comparison with compounds with spacers of different lengths, previously studied. Results from MTT proliferation assay, electrophoresis mobility shift assay (EMSA), transient transfection assay tests and atomic force microscopy (AFM) imaging confirm that pyridinium
surfactants could be a valuable tool for gene delivery purposes, but their performance is highly dependent on the spacer length and strictly related to their structure in solution. All the fluorinated compounds are unable to transfect RD-4 cells, if used alone, but they are all able to deliver a plasmid carrying an enhanced green fluorescent protein (EGFP) expression cassette, when co-formulated with 1,2-dioleyl-sn-glycero-3-phosphoethanolamine (DOPE) in a 1:2 ratio. The fluorinated compounds with spacers formed by six (FGP6) and eight carbon atoms (FGP8) give rise to a very interesting gene delivery activity, greater to that of the commercial reagent, when formulated with DOPE. The hydrogenated compound GP16_6 is unable to sufficiently compact the DNA, as shown by AFM images.
The spectral analysis of thermal fluctuations, or flickering, is a simple and non-invasive method widely used to determine the mechanical properties of artificial and biological lipid membranes. In ...its most common implementation, the position of the edge of a cell or vesicle is tracked from optical microscopy videos. However, a systematic disagreement with X-ray scattering and micromechanical manipulation data has brought into question the validity of the method. We present an improved analysis protocol that resolves these discrepancies by accounting for the finite vertical resolution of the optics used to image fluctuations.
We investigate the interfacial dynamics of a 2D self-organized mixed layer made of silica nanoparticles interacting with phospholipid (DPPC) monolayers at the air/water interface. This system has ...biological relevance, allowing investigation of toxicological effects of nanoparticles on model membranes and lung surfactants. It might also provide bio-inspired technological solutions, exploiting the self-organization of DPPC to produce a non-trivial 2D structuration of nanoparticles. The characterization of interfacial dynamics yields information on the effects of NPs on the mechanical properties, important to improve performances of systems such as colloidosomes, foams, creams. For this, we combine micro-tracking in real-space with measurement in momentum-space via x-ray photon-correlation spectroscopy and Digital Fourier Microscopy. Using these complementary techniques, we extend the spatial range of investigation beyond the limits of each one. We find a dynamical transition from Brownian diffusion to an arrested state driven by compression, characterized by intermittent rearrangements, compatible with a repulsive glass phase. The rearrangement and relaxation of the monolayer structure results dramatically hindered by the presence of NPs, which is relevant to explain some the mechanical features observed for the dynamic surface pressure response of these systems and which can be relevant for the respiratory physiology and for future drug-delivery composite systems.
The development of very efficient and safe non-viral vectors, constituted mainly by cationic lipids bearing multiple charges, is a landmark for in vivo gene-based medicine. To understand the effect ...of the hydrophobic chain's length, we here report the synthesis, and the chemico-physical and biological characterization, of a new term of the homologous series of hydrogenated
bispyridinium surfactants, the 1,1'-bis-dodecyl-2,2'-hexane-1,6-diyl-bispyridinium chloride (GP12_6). Moreover, we have collected and compared the thermodynamic micellization parameters (cmc, changes in enthalpy, free energy, and entropy of micellization) obtained by isothermal titration calorimetry (ITC) experiments for hydrogenated surfactants GP12_6 and GP16_6, and for the partially fluorinated ones, FGP
(where
is the spacer length). The data obtained for GP12_6 by EMSA, MTT, transient transfection assays, and AFM imaging show that in this class of compounds, the gene delivery ability strictly depends on the spacer length but barely on the hydrophobic tail length. CD spectra have been shown to be a useful tool to verify the formation of lipoplexes due to the presence of a "tail" in the 288-320 nm region attributed to a chiroptical feature named ψ-phase. Ellipsometric measurements suggest that FGP6 and FGP8 (showing a very interesting gene delivery activity, when formulated with DOPE) act in a very similar way, and dissimilar from FGP4, exactly as in the case of transfection, and confirm the hypothesis suggested by previously obtained thermodynamic data about the requirement of a proper length of the spacer to allow the molecule to form a sort of molecular tong able to intercalate DNA.
In this work, we demonstrate – in two different settings – the potential of the recognition motif made by tetraphosphonate cavitand/
N
-methyl ammonium salt for the development of supramolecular ...polymer chemistry. In the first part a novel pH sensitive supramolecular homopolymer was assembled by proper design of the corresponding monomer, and monitoring the self-assembling process by several analytical tools, including NMR spectroscopy and light scattering techniques. These measurements provided the evidence for the formation of the homopolymer and its pH responsiveness. In the second study, the two recognition groups – tetraphosphonate cavitand (Host) and sarcosine hydrochloride (Sarc) – introduced in polystyrene (PS–Host) and poly(butyl methacrylate) (PBMA–Sarc) respectively, led to the mixing of the two otherwise immiscible polymers thanks to the energetically favourable host–guest interactions between the polymer chains. The polymer blending was verified by the presence of a single glass transition temperature (
T
g
) and showed its homogeneous morphology by atomic force microscopy (AFM).
Controlled phase separation in a polymer film, with subsequent morphology rearrangement on the micro-scale, provides novel perspectives in smart materials. Based on our experience on supramolecularly ...compatibilised polymer blends consisting of polystyrene and poly(butyl methacrylate), we demonstrate here physical segregation of the blend in the solid state by the application of an electrochemical stimulus. The thereby occurring changes in film morphology, namely the appearance of voids and grains, have been characterised by atomic force microscopy in spin coated and in Langmuir-Schaefer deposited films.
We present an overview of recent advances in stimuli-responsive nanostructures for medicine and drug delivery aiming at improving the efficacy and minimizing side effects of cancer therapies. We ...focus on two complementary system: Self-Lighted Photodynamic Therapy (SLPDT), and magnetic systems for hyperthermia and for controlled drug release. SPLDT, also known as X-ray triggered PDT, bases on hybrid nanostructures such as functionalized SiC/SiOx nanowires and CeF3/ZnO nanostructures. We emphasize the importance of discriminating the various Reactive Oxygen Species (ROS) produced, i.e., singlet oxygen, peroxide, superoxide, and hydroxyl radicals, which have different effects on cells and different therapeutic efficacy. Singlet oxygen is quantified by an ad hoc NIR fluorimeter. SLPDT can be usefully complemented by smart systems responsive to magnetic fields. As examples, we discuss the use of superparamagnetic iron oxide nanoparticles for magnetic hyperthermia and magnetic nanocapsules for triggered drug release. Finally, we highlight promising directions for future developments.
Complex interfaces, such as vesicles and biological membranes, and interface-dominated systems, such as foams and emulsions, are central to a vast range of naturally occurring and synthetic ...materials. In order to characterize their dynamics, it is necessary to cover a wide range of length and time scales. This can only be done by a combination of different techniques. We review here recent results and discuss new trends focusing on two class of techniques: correlation spectroscopies and microscopies, highlighting some examples of their combined use.
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•In complex interfaces and interface-dominated systems, dynamics impact a wide range of technologies.•To characterize dynamics, a combination of techniques spanning a large range of space and time scales is needed.•Synergy between microscopy, direct accessing dynamics, and spectroscopy, which is superior in terms of statistics.•New results expected from the application of optical Monte Carlo methods to DWS.•New results expected from upcoming coherent x-ray beams (upgraded synchrotrons, XFELs) accessing fast dynamics.•A wealth of new microscopy techniques recently developed, thanks to new fast image processing hardware and software.
The control of the behavior of oil in water emulsions requires deeper investigations on the adsorption properties of the emulsion stabilizers at the interfaces, which are fundamental to explain the ...(de)stabilization mechanisms. In this work, we present an extensive study on oil-in-water emulsions stabilized by sodium dodecyl sulfate (SDS) below its critical micellar concentration. Dynamic tensiometry, dilational rheology, and electrical conductivity measurements are used to investigate the adsorption properties at the droplet interface, whereas the aging of the respective emulsions was investigated by monitoring the macroscopic thickness of the emulsion layer, by microimaging and dynamic light scattering (DLS) analysis, to get information on the drop size distribution. In addition, the droplet coalescence is investigated by a microscopy setup. The results of this multitechnique study allow deriving a coherent scenario where the adsorption properties of this ionic surfactant relate to those of the emulsion, such as, for example, the prevention of droplet coalescence and the presence of other mechanisms, such as Ostwald ripening, responsible for the emulsion aging.
This paper examines Michael Oakeshott's ideas on the relation between political philosophy and normative thought. To this end, some of the most controversial concepts of his thought are considered in ...the context of the philosophical debates that developed after the success of analytic philosophy and, in particular, of Ayer's Language, Truth, and Logic. First, the paper argues that, in contrast to analytic and ordinary language thinkers, Oakeshott defends the legitimacy and the rationality of normative thinking. To this end, the importance of the Oakeshottian concepts of tradition and moral practice is stressed, and the controversial notion of 'pursuit of intimations' is considered. Through a discussion of Oakeshott's unpublished notes, the relevance of Aristotle for the development of his thought is also highlighted. Second, the paper contends that Oakeshott sees political philosophy as a critical activity aiming at universal concepts. At the same time, the paper stresses the Oakeshottian distinction between political philosophy and normative thought. With this discussion as a background, the paper finally discusses some of the controversies provoked by Oakeshott's position.
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