Application of DSC and Imaging Techniques on the Development of Innovative Chimeric/Mixed Nanosystems

The aim of this study was to rationally design, develop and investigate chimeric/mixed liposomes, comprising the lipid L-a-phosphatidylcholine, hydrogenated (Soy) (HSPC) and two pH-sensitive amphiphilic diblock copolymers poly(2-(dimethylamino)ethyl methacrylate)-b-poly(lauryl methacrylate) (PDMAEMA-b-PLMA), at various molar ratios to be proposed as new drug nanocarriers. Initially, chimeric bilayers of phospholipid and polymer were prepared and characterized by differential scanning calorimetry (DSC) in order to assess the thermotropic behavior in physiological and acidic environment. Based on the results, chimeric liposomes were developed by thin-film hydration and their physicochemical properties, as well as colloidal physical stability, were investigated with dynamic, electrophoretic and static light scattering (DLS, ELS and SLS). In addition, their size and morphology were evaluated through atomic force microscopy (AFM) and cryogenic transmission electron microscopy (cryo-TEM). An in vitro screening confirmed the low toxicity of these bioinspired and biocompatible nanosystems, which are composed of non-toxic biomaterials as building blocks. Finally, based on the above set of results, the most promising for in vivo applications chimeric liposomes were optimized. Classic and micro-DSC techniques were employed to highlight the thermodynamic phenomena that drive the self-assembly of these mixed nanosystems and that contribute to the membrane properties (transition cooperativity, fluidity, phase separation, etc.), also quantifying the pH-responsive character of these nanosystems. Complementary information as regard the morphological aspects emerged by imaging techniques and the influence of the concentration and hydrophilic-to-hydrophobic balance of the copolymer was assessed. Drug molecule entrapment/incorporation and release studies will be the next step of this work and require a multidisciplinary approach. In this integrated frame, the calorimetric methods are of great relevance as regards both the characterization and the design of these nanosystems

The Formation of Chimeric Nanomorphologies, as a Reflection of Naturally Occurring Thermodynamic Processes

The self-assembly process of different in nature biomaterials leads to the morphogenesis of various nano-structures, where the individual molecule properties (e.g. hydrophilic-to-hydrophobic balance and elasticity), profoundly affect the intermediate surfaces’ interfacial thermodynamics. Herein, the mixing of a phospholipid and an amphiphilic block copolymer, through the thin-film hydration method, gave different morphologies, among which there were vesicles (i.e. liposomes and polymersomes), micelles and worm-like structures. The formation of such variety of structures is attributed to divergent entropic pathways, which are determined by a number of parameters, such as the lipid: polymer molar ratio and the polymer composition. The developed nanosystems are considered as chimeric/mixed, because of the two different in type biomaterials that compose them. The vesicles also exhibited membrane “irregularities”, which are connected with their biophysical behavior. Nature has “chosen” vesicular forms to be the thermodynamically stable “biological apartments”, in which life was enclosed and additionally, vesicles provided compartmentalized systems, where the intracellular environment was built. Phospholipid properties result in membranes/bilayers that harmonically assimilate other molecules, like proteins and retain their integrity and functionality, while gaining additional features. A cause that alters this relationship might induce changes in the membrane composition and morphology, with respect to lipid rafts/domains, what has been linked with the activation and development of certain human disorders/diseases. The self-assembly of two different biomaterials into various structures that present distinct membrane phenomena is believed to simulate these natural processes

Liposomes: Production Methods and Application in Alzheimer’s Disease

Liposomes and lipidic vehicles are nanotechnological platforms that are present in the clinic and industry, with extensive application and much potential in the field of therapeutics. Currently, the obstacles associated with the pathology and physiology of Alzheimer’s disease (AD) and neurodegenerative disorders (NDDs) in general have rendered it impossible to find an effective therapy for these conditions. The only achievement of the available drugs and treatments is that they have succeeded in temporarily alleviating the symptoms and assisting patients in carrying on with their activities of daily living, but they do not delay, let alone halt, the progression of the diseases. So far, numerous small drug molecules and biological molecules have failed in clinical trials. Liposomes represent a promising option for drug delivery that have yet to be tested in clinical trials. They are manufactured by many different and versatile techniques. Their contribution in AD regards mainly the delivery of bioactive agents in a targeted and controlled manner through the blood-brain barrier and into the brain, with the ultimate goal to block the β-amyloid (Aβ) and/or tau aggregation. Their flexibility and biocompatibility as platforms, combined with their ability to protect the encapsulated/incorporated molecules, are advantages that are expected to assist this endeavor. © 2021, The Author(s), under exclusive license to Springer Nature Switzerland AG

A novel, nontoxic and scalable process to produce lipidic vehicles

Lipidic vehicles are novel industrial products, utilized as components for pharmaceutical, cosmeceutical and nutraceutical formulations. The present study concerns a newly invented method to produce lipidic vehicles in the nanoscale that is simple, nontoxic, versatile, time-efficient, low-cost and easy to scale up. The process is a modification of the heating method (MHM) and comprises (i) providing a mixture of an amphiphilic lipid and a charged lipid and/or a fluidity regulator in a liquid medium composed of water and a liquid polyol, (ii) stirring and heating the mixture in two heating steps, wherein the temperature of the second step is higher than the temperature of the first step and (iii) allowing the mixture to cool down to room temperature. The process leads to the self-assembly of nanoparticles of small size and good homogeneity, compared with conventional approaches that require additional size reduction steps. In addition, the incorporation of bioactive molecules, such as drugs, inside the nanoparticles is possible, while lyophilization of the products provides long-term stability. Most importantly, the absence of toxic solvents and the simplicity guarantee the safety and scalability of the process, distinguishing it from most prior art processes to produce lipidic vehicles. © MDPI AG. All rights reserved

Innovative vaccine platforms against infectious diseases: Under the scope of the COVID-19 pandemic

While classic vaccines have proved greatly efficacious in eliminating serious infectious diseases, innovative vaccine platforms open a new pathway to overcome dangerous pandemics via the development of safe and effective formulations. Such platforms play a key role either as antigen delivery systems or as immune-stimulators that induce both innate and adaptive immune responses. Liposomes or lipid nanoparticles, virus-like particles, nanoemulsions, polymeric or inorganic nanoparticles, as well as viral vectors, all belong to the nanoscale and are the main categories of innovative vaccines that are currently on the market or in clinical and preclinical phases. In this paper, we review the above formulations used in vaccinology and we discuss their connection with the development of safe and effective prophylactic vaccines against SARS-CoV-2. © 2021 Elsevier B.V

The significance of drug-to-lipid ratio to the development of optimized liposomal formulation

Liposomes are considered to be one of the most extensively investigated drug delivery nanosystems. Each drug can be loaded either in the liposomal hydrophilic core or within the lipidic bilayer and delivered eventually to the proper site into the organism. There are already many marketed approved liposomal products. The development of a liposomal product is a quite complicated process, while many critical parameters have to be investigated during the preparation process. The present study deals with the drug-to-lipid ratio (D/L ratio), which is a critical process parameter, expresses the actual capacity of the liposome to accommodate the drug and can play a key role at the optimization of every liposomal formulation. D/L ratio is affected by the composition, the different biomaterials and the loading method being used, so the improvement of D/L ratio can optimize the liposomal formulation. D/L ratio can be used as an index of the effectiveness of the preparation method too. Furthermore, D/L ratio influences the therapeutic efficacy of the liposomal product, expressing the actual dose of the drug being administrated. There is a variety of analytical methods, quantifying the drug and the lipids and estimating eventually the D/L ratio. According to the regulatory framework of nanomedicine, about the development of nanosimilars, D/L ratio is a necessary element for the nanosimilar product description and the statement of product comparability. © 2017, © 2017 Informa UK Limited, trading as Taylor & Francis Group

Artificial Exosomes as Targeted Drug Delivery Systems

Exosomes are biological extracellular vesicles that are released by both prokaryotic and eukaryotic cells. Their size ranges between 40 and 160 nm, and their role, although not fully clarified yet, seems to be important for intracellular homeostasis and intercellular communication. As exosomes are enriched in a plethora of payloads, such as cytosolic or surface proteins, lipids, and nucleic acids, their interaction with target cells has proved significant in the progression of many diseases. Cardiovascular, neurodegenerative, or immune pathological conditions are only some examples, where the effect of exosomes is studied, either as disease modulators or as powerful diagnostic tools. On the other hand, exosomes, due to their ability to deliver different types of information, have numerous advantages as drug delivery systems. These nanoplatforms are currently under preclinical and clinical evaluation for the therapy of many diseases, including the novel coronavirus disease. However, production, purification, and compliance with the good manufacturing practice (GMP) issues limit the wide clinical use of exosomes as therapeutic delivery systems. For this reason, the area of artificial exosomes is rapidly evolving. Novel nanosystems that mimic the functionality of exosomes but lack their disadvantages have started to be developed. The aim of this chapter is to present the recent work on the development approaches and the possible payloads of the artificial exosomes so that they can be utilized as safe and effective drug delivery nanosystems. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG

Design and development of pH-responsive HSPC:C12H25-PAA chimeric liposomes

The application of stimuli-responsive medical practices has emerged, in which pH-sensitive liposomes figure prominently. This study investigates the impact of the incorporation of different amounts of pH-sensitive polymer, C12H25-PAA (poly(acrylic acid) with a hydrophobic end group) in l-α-phosphatidylcholine, hydrogenated (Soy) (HSPC) phospholipidic bilayers, with respect to biomimicry and functionality. PAA is a poly(carboxylic acid) molecule, classified as a pH-sensitive polymer, whose pH-sensitivity is attributed to its regulative –COOH groups, which are protonated under acidic pH (pKa ∼4.2). Our concern was to fully characterize, in a biophysical and thermodynamical manner, the mixed nanoassemblies arising from the combination of the two biomaterials. At first, we quantified the physicochemical characteristics and physical stability of the prepared chimeric nanosystems. Then, we studied their thermotropic behavior, through measurement of thermodynamical parameters, using Differential Scanning Calorimetry (DSC). Finally, the loading and release of indomethacin (IND) were evaluated, as well as the physicochemical properties and stability of the nanocarriers incorporating it. As expected, thermodynamical findings are in line with physicochemical results and also explain the loading and release profiles of IND. The novelty of this investigation is the utilization of these pH-sensitive chimeric advanced Drug Delivery nano Systems (aDDnSs) in targeted drug delivery which relies entirely on the biophysics and thermodynamics between such designs and the physiological membranes and environment of living organisms. © 2016 Informa UK Limited, trading as Taylor & Francis Group