Lipidic Nanoparticles, Extracellular Vesicles and Hybrid Platforms as Advanced Medicinal Products: Future Therapeutic Prospects for Neurodegenerative Diseases

Neurodegenerative diseases, such as Alzheimer's and Parkinson's, affect a wide variety of the population and pose significant challenges with progressive and irreversible neural cell loss. The limitations of brain-targeting therapies and the unclear molecular mechanisms driving neurodegeneration hamper the possibility of developing successful treatment options. Thus, nanoscale drug delivery platforms offer a promising solution. This paper explores and compares lipidic nanoparticles, extracellular vesicles (EVs), and hybrid liposomal-EV nanoplatforms as advanced approaches for targeted delivery to combat neurodegeneration. Lipidic nanoparticles are well-characterized platforms that allow multi-drug loading and scalable production. Conversely, EVs offer the ability of selectively targeting specific tissues and high biocompatibility. The combination of these two platforms in one could lead to promising results in the treatment of neurodegeneration. However, many issues, such as the regulatory framework, remain to be solved before these novel products are translated into clinical practice.

Exosome-like genistein-loaded nanoparticles developed by thin-film hydration and 3D-printed Tesla microfluidic chip: A comparative study

Exosomes are naturally derived information carriers that present interest as drug delivery systems. However, their vague cargo and isolation difficulties hinder their use in clinical practice. To overcome these limitations, we developed exosome-like nanoparticles, consisted of the main lipids of exosomes, using two distinct methods: thin-film hydration and 3D-printed microfluidics. Our novel microfluidic device, fabricated through digital light processing printing, demonstrated a favorable architecture to produce exosome-like nanoparticles. We compared these two techniques by analyzing the physicochemical characteristics (size, size distribution, and ζ-potential) of both unloaded and genistein-loaded exosome-like nanoparticles, using dynamic and electrophoretic light scattering. Our findings revealed that the presence of small lipophilic molecules, cholesterol and/or genistein, influenced the characteristics of the final formulations differently based on the development approach. Regardless of the initial differences of the formulations, all exosome-like nanoparticles, whether loaded with genistein or not, exhibited remarkable colloidal stability over time. Furthermore, an encapsulation efficiency of over 87% for genistein was achieved in all cases. Additionally, thermal analysis uncovered the presence of metastable phases within the membranes, which could impact the drug delivery efficiency. In summary, this study provides a comprehensive comparison between conventional and innovative methods for producing complex liposomal nanosystems, exemplified by exosome-like nanoparticles.

Preclinical evaluation of modified carbon nanohorns and their complexation with insulin

The current study emphasizes the minimal toxicity observed in vitro and in vivo for carbon nanohorns (CNHs) modified with third generation polyamidoamine (PAMAM) dendrimers. Initially, we investigated the interactions between CNH-PAMAM and lipid bilayers, which were utilized as representative models of cellular membranes for the evaluation of their toxicity in vitro. We found that the majority of those interactions occur between the modified CNHs and the polar groups of phospholipids, meaning that CNH-PAMAM does not incorporate into the lipid chains, and thus, disruption of the lipid bilayer structure is avoided. This outcome is a very important observation for further evaluation of CNH-PAPAM in cell lines and in animal models. Next, we demonstrated the potential of CNH-PAMAM for complexation with insulin, as a proof of concept for its employment as a delivery platform. Importantly, our study provides comprehensive evidence of low toxicity for CNH-PAMAM both in vitro and in vivo. The assessment of cellular toxicity revealed that the modified CNHs exhibited minimal toxicity, with concentrations of 151 μg mL-1 and 349 μg mL-1, showing negligible harm to EO771 cells and mouse embryonic fibroblasts (MEFs), respectively. Moreover, the histological analysis of the mouse livers demonstrated no evidence of tissue necrosis and inflammation, or any visible signs of severe toxicity. These findings collectively indicate the safe profile of CNH-PAMAM and further contribute to the growing body of knowledge on the safe and efficient utilization of CNH-based nanomaterials in drug and protein delivery applications.

Development of Liposomal and Liquid Crystalline Lipidic Nanoparticles with Non-Ionic Surfactants for Quercetin Incorporation

The aim of the present study is the development, physicochemical characterization, and in vitro cytotoxicity evaluation of both empty and quercetin-loaded HSPC (hydrogenated soy phosphatidylcholine) liposomes, GMO (glyceryl monooleate) liquid crystalline nanoparticles, and PHYT (phytantriol) liquid crystalline nanoparticles. Specifically, HSPC phospholipids were mixed with different non-ionic surfactant molecules (Tween 80 and/or Span 80) for liposomal formulations, whereas both GMO and PHYT lipids were mixed with Span 80 and Tween 80 as alternative stabilizers, as well as with Poloxamer P407 in different ratios for liquid crystalline formulations. Subsequently, their physicochemical properties, such as size, size distribution, and ζ-potential were assessed by the dynamic and electrophoretic light scattering (DLS/ELS) techniques in both aqueous and biological medium with serum proteins. The in vitro biological evaluation of the empty nanosystems was performed by using the MTT cell viability and proliferation assay. Finally, the entrapment efficiency of quercetin was calculated and the differences between the two different categories of lipidic nanoparticles were highlighted. According to the results, the incorporation of the non-ionic surfactants yields a successful stabilization and physicochemical stability of both liposomal and liquid crystalline nanoparticles. Moreover, in combination with an appropriate biosafety in vitro profile, increased encapsulation efficiency of quercetin was achieved. Overall, the addition of surfactants improved the nanosystem's stealth properties. In conclusion, the results indicate that the physicochemical properties were strictly affected by the formulation parameters, such as the type of surfactant.

Interaction of Rhus typhina Tannin with Lipid Nanoparticles: Implication for the Formulation of a Tannin-Liposome Hybrid Biomaterial with Antibacterial Activity

Tannins are natural plant origin polyphenols that are promising compounds for pharmacological applications due to their strong and different biological activities, including antibacterial activity. Our previous studies demonstrated that sumac tannin, i.e., 3,6-bis-O-di-O-galloyl-1,2,4-tri-O-galloyl-β-D-glucose (isolated from Rhus typhina L.), possesses strong antibacterial activity against different bacterial strains. One of the crucial factors of the pharmacological activity of tannins is their ability to interact with biomembranes, which may result in the penetration of these compounds into cells or the realization of their activity on the surface. The aim of the current work was to study the interactions of sumac tannin with liposomes as a simple model of the cellular membrane, which is widely used in studies focused on the explanation of the physicochemical nature of molecule-membrane interactions. Additionally, these lipid nanovesicles are very often investigated as nanocarriers for different types of biologically active molecules, such as antibiotics. In the frame of our study, using differential scanning calorimetry, zeta-potential, and fluorescence analysis, we have shown that 3,6-bis-O-di-O-galloyl-1,2,4-tri-O-galloyl-β-D-glucose interacts strongly with liposomes and can be encapsulated inside them. A formulated sumac-liposome hybrid nanocomplex demonstrated much stronger antibacterial activity in comparison with pure tannin. Overall, by using the high affinity of sumac tannin to liposomes, new, functional nanobiomaterials with strong antibacterial activity against Gram-positive strains, such as S. aureus, S. epidermitis, and B. cereus, can be formulated.

A mini review for lipid-based nanovaccines: from their design to their applications

Nanovaccines have shown to be effective, and this is the reason they are preferred than conventional vaccines. The scope of this review is to describe the role, mechanisms, and advantages of nano vaccines based on lipids, and present the most important types, their physicochemical characteristics, as well as their challenges. The most important categories of lipid nano-vaccines are liposomal nano vaccines and (virus-lipid nanoparticles (NPs)/virosomes. Examples of vaccine formulations from each category are presented and analyzed below, focusing on their structure and physicochemical characteristics. In all cases, a nanoscale platform is used, enriched with adjuvants, antigens, and other helping agents to trigger immune response process and achieve cell targeting, and eventually immunity against the desired disease. The exact mechanism of action of each vaccine is not always completely known or understood. Physicochemical characteristics, such as particle size, morphology/shape, and zeta potential are also mentioned as they seem to affect the properties and mechanism of action of the vaccine formulation.

Synthesis and Testing of Analogs of the Tuberculosis Drug Candidate SQ109 against Bacteria and Protozoa: Identification of Lead Compounds against Mycobacterium abscessus and Malaria Parasites

SQ109 is a tuberculosis drug candidate that has high potency against Mycobacterium tuberculosis and is thought to function at least in part by blocking cell wall biosynthesis by inhibiting the MmpL3 transporter. It also has activity against bacteria and protozoan parasites that lack MmpL3, where it can act as an uncoupler, targeting lipid membranes and Ca2+ homeostasis. Here, we synthesized 18 analogs of SQ109 and tested them against M. smegmatis, M. tuberculosis, M. abscessus, Bacillus subtilis, and Escherichia coli, as well as against the protozoan parasites Trypanosoma brucei, T. cruzi, Leishmania donovani, L. mexicana, and Plasmodium falciparum. Activity against the mycobacteria was generally less than with SQ109 and was reduced by increasing the size of the alkyl adduct, but two analogs were ∼4-8-fold more active than SQ109 against M. abscessus, including a highly drug-resistant strain harboring an A309P mutation in MmpL3. There was also better activity than found with SQ109 with other bacteria and protozoa. Of particular interest, we found that the adamantyl C-2 ethyl, butyl, phenyl, and benzyl analogs had 4-10× increased activity against P. falciparum asexual blood stages, together with low toxicity to a human HepG2 cell line, making them of interest as new antimalarial drug leads. We also used surface plasmon resonance to investigate the binding of inhibitors to MmpL3 and differential scanning calorimetry to investigate binding to lipid membranes. There was no correlation between MmpL3 binding and M. tuberculosis or M. smegmatis cell activity, suggesting that MmpL3 is not a major target in mycobacteria. However, some of the more active species decreased lipid phase transition temperatures, indicating increased accumulation in membranes, which is expected to lead to enhanced uncoupler activity.

The Regulatory Landscape of New Health Technologies and Nanotechnologies: The Role of Complexity of Nanosystems

Herein we present the modern issue of new health technologies that emerge in Medicine and Therapeutics, with regard to their development, regulatory framework, approval, and post-approval monitoring. The European law and legislation distinguish the various subcategories of health technologies in medicinal products, medical devices, biotechnological products, advanced therapy medicinal products, and nanomedicinal products. Each of these categories presents its own distinctive characteristics, based on principles that regard the development technology and intended therapeutic use, and, as a result, is defined by a unique regulatory framework inside the European legislation environment. New health technologies are a key of twenty-first-century knowledge, science, and economy and a part of society growth and economic development, while at the same time they present significant challenges, mainly through matters that regard their safety, efficacy, and value for the public. In this environment, the concept of complexity of living and artificial systems arises, as part of their nature, but also as a perspective that will give answers regarding their dynamic behavior, evolution, and overall quality.

Concomitant delivery of doxorubicin and cisplatin through liposome-based thermosensitive nanoparticles: perspective in the treatment of cancer in animal models

The temperature sensitive liposomal formulations are a promising tool to improve the therapeutic index of the drugs with minimal toxicity. The aim of this study was to investigate the potential of concomitant delivery of cisplatin (Cis) and doxorubicin (Dox) containing thermosensitive liposomes (TSLs) with mild hyperthermia against cancer in vitro and in vivo. The polyethylene glycol coated DPPC/DSPC, thermosensitive and DSPC, non-thermosensitive liposomes incorporating Cis and Dox were prepared and characterized. A conventional Differential Scanning Calorimetry (DSC) technique and Fourier Transform Infrared Spectroscopy (FT-IR) were applied to study drug-phospholipid interaction and compatibility. The chemotherapeutic efficacy of these formulations was evaluated in benzo[a]pyrene (BaP) induced fibrosarcoma under hyperthermic condition. The size diameter of prepared thermosensitive liposomes was measured to be 120 ± 10 nm. The DSC data exhibited the changes in the curves of DSPC + Dox and DSPC + Cis while comparing the pure DSPC and drugs. However, the FITR showed same spectrum of phospholipids and drugs individually and in the mixture as well. The data showed higher efficacy of Cis-Dox-TSL as 84% inhibition in tumor growth was recorded in this group of animals in hyperthermic condition. The Kaplan-Meir curve revealed, 100% and 80% survival of the animals in the groups treated with Cis-Dox-TSL under hyperthermia and Cis-Dox-NTSL without hyperthermia, respectively. However, Cis-TSL as well as Dox-TSL exhibited 50% survival, while only 20% survival was recorded in the groups of animals treated with Dox-NTSL and Cis-NTSL. The flow cytometry analysis revealed that Cis-Dox-NTSL augments the induction of apoptosis in the tumor cells which was recorded as 18%. As expected, Cis-Dox-TSL showed great potential as 39% of cells were measured as apoptotic cells, significantly very high in comparison to Cis-Dox-NTSL, Dox-TSL and Cis-TSL as well. The apoptotic analysis of the cells by flow cytometry clearly indicated the effect of hyperthermia during the treatment while Cis-Dox-TSL formulation was administered. Finally, the immunohistochemical analysis of the tumor tissues by confocal microscopy exhibited several fold increases in the expression of pAkt in the animals treated with vehicles in Sham-NTSL as well as Sham-TSL. However, Cis-Dox-TSL showed great reduction in the expression of Akt, as it declined by 11-fold. The results of the present study directed the role of concomitant delivery doxorubicin and cisplatin containing thermosensitive liposomes under hyperthermic conditions for the development of a novel therapeutic strategy for the treatment of cancer.

Development of stimuli-responsive lyotropic liquid crystalline nanoparticles targeting lysosomes: Physicochemical, morphological and drug release studies

The abilities of sub-cellular targeting and stimuli-responsiveness are critical challenges in pharmaceutical nanotechnology. In the present study, glyceryl monooleate (GMO)-based non-lamellar lyotropic liquid crystalline nanoparticles were stabilized by the poly(2-(dimethylamino)ethyl methacrylate)-b-poly(lauryl methacrylate) block copolymer carrying tri-phenyl-phosphine cations (TPP-QPDMAEMA-b-PLMA), either used alone or in combination with other polymers as co-stabilizers. The systems were designed to perform simultaneously sub-cellular targeting, stimuli-responsiveness and to exhibit stealthiness. The physicochemical characteristics and fractal dimensions of the resultant nanosystems were obtained from light scattering techniques, while their micropolarity and microfluidity from fluorescence spectroscopy. Their morphology was assessed by cryo-TEM, while their thermal behavior by microcalorimetry and high-resolution ultrasound spectroscopy. The analyzed properties, including the responsiveness to pH and temperature, were found to be dependent on the combination of the polymeric stabilizers. The subcellular localization was monitored by confocal microscopy, revealing targeting to lysosomes. Subsequently, resveratrol was loaded into the nanosystems, the entrapment efficiency was investigated and in vitro release studies were carried out at different conditions, in which a stimuli-triggered drug release profile was achieved. In conclusion, the proposed multi-functional nanosystems can be considered as potentially stealth, stimuli-responsive drug delivery nanocarriers, with targeting ability to lysosomes and presenting a stimuli-triggered drug release profile.

Amphiphilic Copolymer-Lipid Chimeric Nanosystems as DNA Vectors

Lipid-polymer chimeric (hybrid) nanosystems are promising platforms for the design of effective gene delivery vectors. In this regard, we developed DNA nanocarriers comprised of a novel poly[(stearyl methacrylate-co-oligo(ethylene glycol) methyl ether methacrylate] [P(SMA-co-OEGMA)] amphiphilic random copolymer, the cationic 1,2-dioleoyl-3-(trimethylammonium) propane (DOTAP), and the zwitterionic L-α-phosphatidylcholine, hydrogenated soybean (soy) (HSPC) lipids. Chimeric HSPC:DOTAP:P[(SMA-co-OEGMA)] nanosystems, and pure lipid nanosystems as reference, were prepared in several molar ratios of the components. The colloidal dispersions obtained presented well-defined physicochemical characteristics and were further utilized for the formation of lipoplexes with a model DNA of linear topology containing 113 base pairs. Nanosized complexes were formed through the electrostatic interaction of the cationic lipid and phosphate groups of DNA, as observed by dynamic, static, and electrophoretic light scattering techniques. Ultraviolet-visible (UV-Vis) and fluorescence spectroscopy disclosed the strong binding affinity of the chimeric and also the pure lipid nanosystems to DNA. Colloidally stable chimeric/lipid complexes were formed, whose physicochemical characteristics depend on the N/P ratio and on the molar ratio of the building components. Cryogenic transmission electron microscopy (Cryo-TEM) revealed the formation of nanosystems with vesicular morphology. The results suggest the successful fabrication of these novel chimeric nanosystems with well-defined physicochemical characteristics, which can form stable lipoplexes.

Development of Ulvan-Containing Liposomes as Antibacterial Drug Delivery Platforms

Liposomes, due to their safety profile and targeting ability, are among the most studied nanocarriers as antimicrobial delivery systems. However, due to lack of stability and the non-specific interaction of liposomes with cells and proteins, their use is relatively limited. Aiming to overcome these drawbacks, it was envisaged that incorporation of ulvan, a bioactive marine sulfated polysaccharide isolated from green algae, in liposomes could improve their physicochemical properties and overall stability. Thus, we initially studied the interactions of ulvan with neutral, negatively, and positively charged lipids using Differential Scanning Calorimetry and subsequently, based on the obtained results, we prepared the respective ulvan–containing neutral and charged liposomes, where ulvan interacts with both lipid chains and polar groups in the liposomal bilayer. In a further step, we entrapped in the liposomes fusidic acid, used as a model antibacterial drug, and proceeded with the evaluation of their antibacterial activity against Staphylococcus aureus. The physicochemical properties (size and ζ-potential), stability, morphology, and entrapment efficiency of the prepared liposomal formulations were determined.

Lipid-based nanoparticles and RNA as innovative neuro-therapeutics

RNA-delivery is a promising tool to develop therapies for difficult to treat diseases such as neurological disorders, by silencing pathological genes or expressing therapeutic proteins. However, in many cases RNA delivery requires a vesicle that could effectively protect the molecule from bio-degradation, bypass barriers i.e., the blood brain barrier, transfer it to a targeted tissue and efficiently release the RNA inside the cells. Many vesicles such as viral vectors, and polymeric nanoparticles have been mentioned in literature. In this review, we focus in the discussion of lipid-based advanced RNA-delivery platforms. Liposomes and lipoplexes, solid lipid nanoparticles and lipid nanoparticles are the main categories of lipidic platforms for RNA-delivery to the central nervous systems (CNS). A variety of surface particles' modifications and routes of administration have been studied to target CNS providing encouraging results in vivo. It is concluded that lipid-based nanoplatforms will play a key role in the development of RNA neuro-therapies.

In vitro and in vivo activity of thermosensitive liposomes loaded with doxorubicin and cisplatin

Thermosensitive liposomes loaded with cisplatin and doxorubicin composed of DPPC, DSPC, and DPPE-PEG5000 with different ratios were prepared by thin film hydration method. The Differential Scanning Calorimetry (DSC) curves showed that the liposomes composed of DPPC-DSPC-DPPE-PEG5000 with phospholipid ratio 95:5:0.05 w/w were a suitable formulation as thermosensitive liposomes with a DSC peak at 42.1 °C. The effect of doxorubicin and cisplatin encapsulated non-thermosensitive and thermosensitive liposomes on cellular proliferation and IC50 in SKBR3 & MDA-MB-231 breast cancer and PC-3 & LNcaP prostate cancer cell lines was investigated. The results showed that doxorubicin loaded into thermosensitive liposomes showed 20-fold decrease in the IC50 at 42 °C while comparing it with the same at 37 °C. Also, the results showed a more than 35-fold and 12-fold decrease in the IC50 of cisplatin thermosensitive liposomes at 42 °C, while compared with free cisplatin and cisplatin thermosensitive liposomes at any temperature. The in vivo results showed that the effect of doxorubicin encapsulated thermosensitive liposomes at hyperthermic conditions during the treatment as the tumor growth inhibition was measured 1.5-fold higher than any of the liposomal formulations of doxorubicin. It was also noticed that the tumor volume reduced to 150 mm³ in doxorubicin thermosensitive liposomes (G8) after 3 weeks during the treatment, but increased to 196 mm³ after 4 weeks. The Kaplan-Meir curve showed the 100% survival of the animals from G8 (thermosensitive liposomes containing doxorubicin plus hyperthermia) after 12 weeks. The flow cytometry data revealed more than 25% apoptotic cells and 6.25% necrotic cells in the tumor cells from the tissues of the G8 group of the animals. The results clearly indicate the superior efficacy of doxorubicin and cisplatin containing thermosensitive liposomes treatment during hyperthermia.

Protein-liposome interactions: the impact of surface charge and fluidisation effect on protein binding

At the dawn of a new nanotechnological era in the pharmaceutical field, it is very important to examine and understand all the aspects that influence in vivo behaviour of nanoparticles. In this point of view, the interactions between serum proteins and liposomes with incorporated anionic, cationic, and/or PEGylated lipids were investigated to elucidate the role of surface charge and bilayer fluidity in protein corona's formation. 1,2-dipalmitoyl-sn-glycero-3- phosphocholine (DPPC), hydrogenated soybean phosphatidylcholine (HSPC), and 1,2-dioctadecanoyl-sn-glycero-3-phosphocholine (DSPC) liposomes with the presence or absence of 1,2-dipalmitoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (sodium salt) (DPPG), 1,2-di-(9Z-octadecenoyl)-3-trimethylammonium-propane (chloride salt) (DOTAP), and/or 1,2-dipalmitoylsn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-5000] (DPPE-PEG 5000) lipids were prepared by the thin-film hydration method. The evaluation of their biophysical characteristics was enabled by differential scanning calorimetry and dynamic and electrophoretic light scattering. The physicochemical characteristics of mixed liposomes were compared before and after exposure to foetal bovine serum (FBS) and were correlated to calorimetric data. Our results indicate protein binding to all liposomal formulations. However, it is highlighted the importance of surface charge and fluidisation effect to the extent of protein adsorption. Additionally, considering the extensive use of cationic lipids for innovative delivery platforms, we deem PEGylation a key parameter, because even in a small proportion can reduce protein binding, and thus fast clearance and extreme toxicity without affecting positive charge. This study is a continuation of our previous work about protein-liposome interactions and fraction of stealthiness (Fs) parameter, and hopefully a design road map for drug and gene delivery.

Losartan Interactions with 2-Hydroxypropyl-β-CD

Losartan potassium salt (LSR) is a well-known antihypertensive drug with proven beneficial effects on human health. Its formulation with the non-toxic 2-hydroxypropyl-β-cyclodextrin (2-HP-β-CD) could improve its pharmacological profile. Thus, its molecular interactions are studied using a combination of Differential Scanning Calorimetry (DSC), Nuclear Magnetic Resonance (NMR) and Molecular Dynamics (MD). First, its complexation is shown through Differential Scanning Calorimetry as lyophilization provided distinct thermal properties in comparison to the mixture. The complexation is further proved by utilizing the chemical shift changes in the complexation and T1 values. Furthermore, the reversible favorable complexation was shown by MD calculations. Such physical chemical properties provide evidence that this formulation must be further explored through biological experiments.

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.

Chimeric liposomes decorated with P407: an alternative biomaterial for producing stealth nano-therapeutics

The aim of the present study is the development and evaluation of the physicochemical properties of chimeric hydrogenated soya phosphatidylcholine (HSPC) and egg phosphatidylcholine (EggPC) liposomes with incorporated triblock copolymer Poloxamer P407 (P407). The physicochemical assay was held in water HPLC-grade and Foetal Bovine Serum (FBS), in order to determine whether these systems can be used as drug or antigen delivery nanosystems. Dynamic and electrophoretic light scattering (DLS/ELS) techniques were used for the measurement of the hydrodynamic diameter, the polydispersity index, and the ζ-potential of the prepared nanosystems. The incorporation of the P407 resulted in a size reduction of all systems. A decrease in the hydrodynamic diameter and polydispersity index were also found as a result of increasing the storage temperature from 4 °C to 25 °C, attributed to P407. The experiments that were carried out in FBS, showed that the addition of P407 improved systems stealth properties. Concluding, we propose P407 as a promising alternative to PEG in the development of lipid nanoparticles with optimized bio- and shelf-stability.

The technology of transdermal delivery nanosystems: from design and development to preclinical studies

Transdermal administration has gained much attention due to the remarkable advantages such as patient compliance, drug escape from first-pass elimination, favorable pharmacokinetic profile and prolonged release properties. However, the major limitation of these systems is the limited skin penetration of the stratum corneum, the skin's most important barrier, which protects the body from the insertion of substances from the environment. Transdermal drug delivery systems are aiming to the disruption of the stratum corneum in order for the active pharmaceutical ingredients to enter successfully the circulation. Therefore, nanoparticles are holding a great promise because they can act as effective penetration enhancers due to their small size and other physicochemical properties that will be analyzed thoroughly in this report. Apart from the investigation of the physicochemical parameters, a comparison between the different types of nanoparticles will be performed. The complexity of skin anatomy and the unclear mechanisms of penetration should be taken into consideration to reach some realistic conclusions regarding the way that the described parameters affect the skin permeability. To the best of the authors knowledge, this is among the few reports on the literature describing the technology of transdermal delivery systems and how this technology affects the biological activity.

Thermoresponsive chimeric nanocarriers as drug delivery systems

Chimeric or mixed nanosystems belong to the class of advanced therapeutics. Their distinctive characteristic compared with other types of nanoparticles is that they combine two or more different classes of biomaterials. These platforms have created a promising and versatile field of nanomedicine, incorporating materials that are biocompatible, such as lipids, but also functional, such as stimuli-responsive polymers. In the present work, thermoresponsive chimeric nanocarriers composed of l-α-phosphatidylcholine (Egg, Chicken) (EPC) phospholipids and poly(N-isopropylacrylamide)-b-poly(lauryl acrylate) (PNIPAM-b-PLA) block copolymers were designed and developed. Initially, model lipid bilayers with incorporated polymers and drug molecule TRAM-34 were built and studied for their thermodynamics, in order to assess the stability and functionality of the systems. Chimeric nanoparticles of EPC and PNIPAM-b-PLA were then developed and evaluated for their physicochemical properties in different medium conditions, as well as for their morphology. Polymer incorporation led to alterations in the properties and morphology of the nanoparticles, while interactions with serum proteins were absent. TRAM-34 was also incorporated inside the developed nanocarriers, followed by incorporation and release studies, which revealed the functionality of the system in elevated temperature conditions. Finally, in vitro studies on normal cells suggest the biocompatibility of these nanosystems. The proposed platforms are promising for further studies and applications in vitro and in vivo.

The Influence of Hydrophobic Blocks of PEO-Containing Copolymers on Glyceryl Monooleate Lyotropic Liquid Crystalline Nanoparticles for Drug Delivery

The investigation of properties of amphiphilic block copolymers as stabilizers for non-lamellar lyotropic liquid crystalline nanoparticles represents a fundamental issue for the formation, stability and upgraded functionality of these nanosystems. The aim of this work is to use amphiphilic block copolymers, not studied before, as stabilizers of glyceryl monooleate 1-(cis-9-octadecenoyl)-rac-glycerol (GMO) colloidal dispersions. Nanosystems were prepared with the use of poly(ethylene oxide)-b-poly(lactic acid) (PEO-b-PLA) and poly(ethylene oxide)-b-poly(5-methyl-5-ethyloxycarbonyl-1,3-dioxan-2-one) (PEO-b-PMEC) block copolymers. Different GMO:polymer molar ratios lead to formulation of nanoparticles with different size and internal organization, depending on the type of hydrophobic block. Resveratrol was loaded into the nanosystems as a model hydrophobic drug. The physicochemical and morphological characteristics of the prepared nanosystems were investigated by dynamic light scattering (DLS), cryogenic transmission electron microscopy (cryo-TEM), fast Fourier transform (FFT) analysis and X-ray diffraction (XRD). The studies allowed the description of the lyotropic liquid crystalline nanoparticles and evaluation of impact of copolymer composition on these nanosystems. The structures formed in GMO:block copolymer colloidal dispersions were compared with those discussed previously. The investigations broaden the toolbox of polymeric stabilizers for the development of this type of hybrid polymer/lipid nanostructures.

Chimeric Stimuli-Responsive Liposomes as Nanocarriers for the Delivery of the Anti-Glioma Agent TRAM-34

Nanocarriers are delivery platforms of drugs, peptides, nucleic acids and other therapeutic molecules that are indicated for severe human diseases. Gliomas are the most frequent type of brain tumor, with glioblastoma being the most common and malignant type. The current state of glioma treatment requires innovative approaches that will lead to efficient and safe therapies. Advanced nanosystems and stimuli-responsive materials are available and well-studied technologies that may contribute to this effort. The present study deals with the development of functional chimeric nanocarriers composed of a phospholipid and a diblock copolymer, for the incorporation, delivery and pH-responsive release of the antiglioma agent TRAM-34 inside glioblastoma cells. Nanocarrier analysis included light scattering, protein incubation and electron microscopy, and fluorescence anisotropy and thermal analysis techniques were also applied. Biological assays were carried out in order to evaluate the nanocarrier nanotoxicity in vitro and in vivo, as well as to evaluate antiglioma activity. The nanosystems were able to successfully manifest functional properties under pH conditions, and their biocompatibility and cellular internalization were also evident. The chimeric nanoplatforms presented herein have shown promise for biomedical applications so far and should be further studied in terms of their ability to deliver TRAM-34 and other therapeutic molecules to glioblastoma cells.

Association of the Thermodynamics with the Functionality of Thermoresponsive Chimeric Nanosystems

Stimuli-responsive nanosystems are an emerging technology in the field of therapy and are very promising for various applications, including targeted drug delivery. In this chapter, our scope is to integrate two different methodologies, namely differential scanning calorimetry (DSC) and dynamic light scattering (DLS), in order to rationally approach the functional behavior of thermoresponsive chimeric/mixed liposomes and interpret their thermoresponsiveness on a thermodynamic basis. In particular, chimeric bilayers comprised of the phospholipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and two different-in-composition thermoresponsive amphiphilic block copolymers poly(N-isopropylacrylamide)-b-poly(lauryl acrylate) (PNIPAM-b-PLA) 1 or 2 were built by a conventional evaporation technique, followed by DSC, and chimeric liposomes of DPPC and PNIPAM-b-PLA 1 were developed and studied by DLS, after preparation and after a simple heating protocol. The results from both methodologies indicate the composition- and concentration-dependent lyotropic effect of the foreign copolymer molecule on the properties and functionality of the lipidic membrane.

Chimeric liposomes incorporating functional copolymers: preparation and pH/thermo-responsive behaviour in aqueous solutions

The purpose of this study is to prepare stimuli-responsive chimeric liposomes (i.e. hybrid polymer-lipid liposomes) containing functional copolymers and conduct aqueous solution studies in order to determine their properties and potential as drug-delivery nanocarriers. Two random copolymers, composed of the hydrophilic, pH and thermo-responsive 2-(dimethyl amino) ethyl methacrylate (DMAEMA) monomer and the hydrophobic stearyl methacrylate (SMA) monomer, were synthesized via free-radical polymerization and molecularly characterized using SEC, FTIR, and 1H-NMR. The synthesis was followed by aqueous solution studies, utilising dynamic light scattering (DLS) in order to determine their stimuli responsive self-assembly properties. The preparation of chimeric liposomes was mediated by thin film deposition and hydration, followed by aqueous solution studies via DLS, ζ-potential and fluorescence spectroscopy. The drug-loading studies include curcumin loading via a thin film deposition and hydration technique, while aqueous solution properties of the drug-loaded chimeric liposomes were determined utilizing DLS, and UV-Vis spectroscopy.

Differential Scanning Calorimetry (DSC) on Sartan/Cyclodextrin Delivery Formulations

Differential scanning calorimetry (DSC) is a widely utilized method for the interactions of drug molecules with drug delivery systems (DDSs). Herein is described a protocol for studying the interactions and entrapment efficiency of the prototype sartan losartan and the polydynamic, structurally similar irbesartan inside the nontoxic 2-hydroxypropyl-β-cyclodextrin (2-HP-β-CD). The thermal scan properties of both sartan molecules have been studied when physically mixed or complexed with the cyclodextrin. The thermograms indeed showed significant differences between the mixtures and complexes, establishing DSC as a valuable method to characterize the state of the drugs in these pharmaceutical formulations.

Lamellarity and size distributions in mixed DPPC/amphiphilic poly(2-oxazoline) gradient copolymer vesicles and their temperature response

Mixed liposomes of dipalmitoylphosphatidylcholine (DPPC) and gradient (pseudodiblock) poly(2-methyl-2-oxazoline)-grad-poly(2-phenyl-2-oxazoline) (MPOx) copolymers are investigated by small angle neutron scattering (SANS). All experimental data, from different phospholipid-copolymer compositions, concentrations and temperatures are fitted with one model. This model allows the determination of the separate contributions from vesicular populations of different lamellarity and size. MPOx copolymers are proved to modify both the size and lamellarity of DPPC liposomes. The gradient copolymer with higher hydrophilic content induces shrinkage of the uni- and bi-lamellar DPPC vesicles. The copolymer with lower hydrophilic content causes dramatic changes on the lamellarity of DPPC vesicles by the formation of hexa-lamellar vesicles. The tendency of multi-lamellar vesicles to transform into uni-lamellar ones as temperature increases is more pronounced in the presence of the copolymers. These findings may have direct implications on the drug loading and release properties of liposomes and their interactions with cells.

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 of lipidic vehicles.

Liquid crystalline nanoparticles for drug delivery: The role of gradient and block copolymers on the morphology, internal organisation and release profile

Amphiphilic polymers represent one of the main class of stabilizers for non-lamellar lyotropic liquid crystalline nanoparticles, being essential for their formation and stability. In the present study, poly(ethylene oxide)-block-poly(ε-caprolactone) (PEO-b-PCL) block copolymers and poly(2-methyl-2-oxazoline)-grad-poly(2-phenyl-2-oxazoline) (MPOx) gradient copolymers were incorporated as stabilizers in liquid crystalline nanoparticles prepared from glyceryl monooleate. The polymers were chosen according to their high biocompatibility and promising stealth properties, in order to develop safe and efficient drug delivery nanosystems. The physicochemical characteristics and fractal dimension of the resultant nanosystems were obtained from light scattering techniques, while their micropolarity and microfluidity from fluorescence spectroscopy. The effect of temperature, serum proteins and ionic strength on the physicochemical behavior was monitored. Their morphology was assessed by cryo-TEM, while their thermal behavior by microcalorimetry and high-resolution ultrasound spectroscopy. Their properties were dependent on the stabilizer chemistry and topology (block/gradient copolymer) and its concentration. Subsequently, resveratrol, as model hydrophobic drug, was loaded into the nanosystems, the entrapment efficiency was calculated and in vitro release studies were carried out, highlighting how the different stabilizer can differentiate the drug release profile. In conclusion, the proposed copolymers broaden the toolbox of polymeric stabilizers for the development of liquid crystalline nanoparticles intended for drug delivery applications.

Preparation and Biophysical Characterization of Quercetin Inclusion Complexes with β-Cyclodextrin Derivatives to be Formulated as Possible Nose-to-Brain Quercetin Delivery Systems

Quercetin (Que) is a flavonoid associated with high oxygen radical scavenging activity and potential neuroprotective activity against Alzheimer's disease. Que's oral bioavailability is limited by its low water solubility and extended peripheral metabolism; thus, nasal administration may be a promising alternative to achieve effective Que concentrations in the brain. The formation of Que-2-hydroxypropylated-β-cyclodextrin (Que/HP-β-CD) complexes was previously found to increase the molecule's solubility and stability in aqueous media. Que-methyl-β-cyclodextrin (Que/Me-β-CD) inclusion complexes were prepared, characterized, and compared with the Que/HP-β-CD complex using biophysical and computational methods (phase solubility, fluorescence and NMR spectroscopy, differential scanning calorimetry (DSC), and molecular dynamics simulations (MDS)) as candidates for the preparation of nose-to-brain Que's delivery systems. DSC thermograms, NMR, fluorescence spectroscopy, and MDS confirmed the inclusion complex formation of Que with both CDs. Differences between the two preparations were observed regarding their thermodynamic stability and inclusion mode governing the details of molecular interactions. Que's solubility in aqueous media at pH 1.2 and 4.5 was similar and linearly increased with both CD concentrations. At pH 6.8, Que's solubility was higher and positively deviated from linearity in the presence of HP-β-CD more than with Me-β-CD, possibly revealing the presence of more than one HP-β-CD molecule involved in the complex. Overall, water solubility of lyophilized Que/Me-β-CD and Que/HP-β-CD products was approximately 7-40 times and 14-50 times as high as for pure Que at pH 1.2-6.8. In addition, the proof of concept experiment on ex vivo permeation across rabbit nasal mucosa revealed measurable and similar Que permeability profiles with both CDs and negligible permeation of pure Que. These results are quite encouraging for further ex vivo and in vivo evaluation toward nasal administration and nose-to-brain delivery of Que.

Antihypertensive activity and molecular interactions of irbesartan in complex with 2-hydroxypropyl-β-cyclodextrin

Irbesartan (IRB) exerts beneficial effects either alone or in combination with other drugs on numerous diseases, such as cancer, diabetes, and hypertension. However, due to its high lipophilicity, IRB does not possess the optimum pharmacological efficiency. To circumvent this problem, a drug delivery system with 2-hydroxypropyl-β-cyclodextrin (2-HP-β-CD) was explored. The 1:1 complex between IRB and 2-HP-β-CD was identified through ESI QTF HRMS. Dissolution studies showed a higher dissolution rate of the lyophilized IRB-2-HP-β-CD complex than the tablet containing IRB at pH = 1.2. DSC results revealed the differences of the thermal properties between the complex and various mixtures consisting of the two components, namely IRB and 2-HP-β-CD. Interestingly, depending on the way the mixture preparation was conducted, different association between the two components was observed. Molecular dynamics (MD) simulations predicted the favorable formation of the above complex and identified the dominant interactions between IRB and 2-HP-β-CD. In vitro pharmacological results verified that the inclusion complex not only preserves the binding affinity of IRB for AT1R receptor, but also it slightly increases it. As the complex formulation lacks the problems of the tablet, our approach is a promising new way to improve the efficiency of IRB.

Nanomedicines and Nanosimilars: Looking for a New and Dynamic Regulatory "Astrolabe" Inspired System

The application of the nanotechnology in medicine and pharmaceutics opens new horizons in therapeutics. Several nanomedicines are in the market and an increasing number is in clinical trials. But which is the advantage of the medicines in nanoscale? The scientists and the regulatory authorities agree that the size and consequently the physiochemical/biological properties of nanomaterials play a key role in their safety and effectiveness. Additionally, all of them agree that a new scientific-based regulatory landscape is required for the establishment of nanomedicines in the market. The aim of this review is to investigate the parameters that the scientists and the regulatory authorities should take into account in order to build up a dynamic regulatory landscape for nanomedicines. For this reason, we propose an "astrolabe-like system" as the guide for establishing the regulatory approval process. Its function is based on the different physicochemical/biological properties in comparison to low molecular weight drugs.

The boundary lipid around DMPC-spanning influenza A M2 transmembrane domain channels: Its structure and potential for drug accommodation

We have investigated the perturbation of influenza A M2TM in DMPC bilayers. We have shown that (a) DSC and SAXS detect changes in membrane organization caused by small changes (micromolar) in M2TM or aminoadamantane concentration and aminoadamantane structure, by comparison of amantadine and spiro[pyrrolidine-2,2'-adamantane] (AK13), (b) that WAXS and MD can suggest details of ligand topology. DSC and SAXS show that at a low M2TM micromolar concentration in DPMC bilayers, two lipid domains are observed, which likely correspond to M2TM boundary lipids and bulk-like lipids. At higher M2TM concentrations, one domain only is identified, which constitutes essentially all of the lipid molecules behaving as boundary lipids. According to SAXS, WAXS, and DSC in the absence of M2TM, both aminoadamantane drugs exert a similar perturbing effect on the bilayer at low concentrations. At the same concentrations of the drug when M2TM is present, amantadine and, to a lesser extent, AK13 cause, according to WAXS, a significant disordering of chain-stacking, which also leads to the formation of two lipid domains. This effect is likely due, according to MD simulations, to the preference of the more lipophilic AK13 to locate closer to the lateral surfaces of M2TM when compared to amantadine, which forms stronger ionic interactions with phosphate groups. The preference of AK13 to concentrate inside the lipid bilayer close to the exterior of the hydrophobic M2TM helices may contribute to its higher binding affinity compared to amantadine.

pH-responsive chimeric liposomes: From nanotechnology to biological assessment

The utilization of liposomes in biomedical applications has greatly benefited the diagnosis and treatment of various diseases. These biomimetic nano-entities have been very useful in the clinical practice as drug delivery systems in their conventional form, comprising lipids as structural components. However, the scientific efforts have recently shifted towards the development of more sophisticated nanotechnological platforms, which apply functional biomaterials, such as stimuli-responsive polymers, in order to aid the drug molecule targeting concept. These nanosystems are defined as chimeric/mixed, because they combine more than one different in nature biomaterials and their development requires intensive study through biophysical and thermodynamic approaches before they may reach in vivo application. Herein, we designed and developed chimeric liposomes, composed of a phospholipid and pH-responsive amphiphilic diblock copolymers and studied their morphology and behavior based on crucial formulation parameters, including biomaterial concentration, dispersion medium pH and polymer composition. Additionally, their interactions with biological components, pH-responsiveness and membrane thermodynamics were assessed. Finally, preliminary in vivo toxicity experiments of the developed nanosystems were carried out, in order to establish a future protocol for full in vivo evaluation. The results have been correlated with the properties of the chimeric nanosystems and highlight the importance of such approaches for designing and developing effective nanocarriers for biomedical applications.

Preparation and physicochemical characterization of elastic liposomes: a road-map library for their design

Elastic liposomes consist of phospholipids and of surfactants, could be considered as promising nanotechnological platforms for skin drug delivery. The aim of the present study was the formation of elastic liposomes by thin film hydration method, using different phospholipids and surfactants, in order to determine the effect of the components on their physical characteristics and on their physical stability. Physical properties of elastic liposomes were evaluated using dynamic light scattering (DLS)method. The particle size at the day of their preparation, was ranged between small and large unilamellar vesicles (SUVs and LUVs), dependent on the hydrophilicity of the surfactant used, while their PDI (Poly Dispersity Index) value was close to zero, indicating monodispersed systems. Physical stability study involved the measure of particle size, as a quantifiable physical property, at selected times over a 30-days period, at storage conditions: (i) 4 °C, (ii) 25 °C, iii) 45 °C, suggested that refrigerated conditions promote physical stability, while high temperatures induce aggregation. According to the physical stability study elastic liposomes composed ofTween80 were found to bemore stable than those composed of Span80, at ambient conditions. The goal of our investigation was centred to the development and evaluation of a well know liposomal category i.e. elastic liposomes, by modified their composition with common surfactants (i.e. Span and/or Tween), creating, a new liposomal class namely, elastic lipo-niosomes. To the best of knowledge this the first time that these hybrid vesicles appeared in the literature exhibiting the aforementioned category lipid/surfactants and molar ratios.

Stimuli-Responsive Lyotropic Liquid Crystalline Nanosystems with Incorporated Poly(2-Dimethylamino Ethyl Methacrylate)-b-Poly(Lauryl Methacrylate) Amphiphilic Block Copolymer

There is an emerging need to evolve the conventional lyotropic liquid crystalline nanoparticles to advanced stimuli-responsive, therapeutic nanosystems with upgraded functionality. Towards this effort, typically used stabilizers, such as Pluronics^®, can be combined or replaced by smart, stimuli-responsive block copolymers. The aim of this study is to incorporate the stimuli-responsive amphiphilic block copolymer poly(2-(dimethylamino)ethyl methacrylate)-b-poly(lauryl methacrylate) (PDMAEMA-b-PLMA) as a stabilizer in lipidic liquid crystalline nanoparticles, in order to provide steric stabilization and simultaneous stimuli-responsiveness. The physicochemical and morphological characteristics of the prepared nanosystems were investigated by light scattering techniques, cryogenic-transmission electron microscopy (cryo-TEM), X-ray diffraction (XRD) and fluorescence spectroscopy. The PDMAEMA-b-PLMA, either individually or combined with Poloxamer 407, exhibited different modes of stabilization depending on the lipid used. Due to the protonation ability of PDMAEMA blocks in acidic pH, the nanoparticles exhibited high positive charge, as well as pH-responsive charge conversion, which can be exploited towards pharmaceutical applications. The ionic strength, temperature and serum proteins influenced the physicochemical behavior of the nanoparticles, while the polymer concentration differentiated their morphology; their micropolarity and microfluidity were also evaluated. The proposed liquid crystalline nanosystems can be considered as novel and attractive pH-responsive drug and gene delivery nanocarriers due to their polycationic content.

Carbon nanohorn/liposome systems: Preformulation, design and in vitro toxicity studies

In the present work, the convergence of two different drug delivery systems is investigated, namely the combination of carbon nanohorns (CNHs) and liposomes. Our effort initially included the synthesis of two conversely charged carbon nanohorns and their subsequent analysis through various methods. The study of their effect on the thermotropic behavior of artificial membranes provided an essential assistance for the upcoming liposome preparation, which were estimated for their physicochemical properties. The presence of CNHs alters the calorimetric parameters of the lipids. We also prepared CNHs:liposome systems. The characteristic morphology and secondary spherical superstructure of CNHs is retained in the chimeric materials, suggesting that the interactions with the liposomes do not alter the dahlia-flower-like aggregation of CNHs. Both CNHs-liposome systems exhibit a relatively small cellular cytotoxicity in vitro, tested in mouse embryonic fibroblasts. To summarize, we developed CNHs:liposome platforms with a complete knowledge of their thermotropic, physicochemical, morphological and nanotoxicological characteristics.

Incorporation of PEGylated δ-decalactone into lipid bilayers: thermodynamic study and chimeric liposomes development

Liposomes have been on the market as drug delivery systems for over 25 years. Their success comes from the ability to carry toxic drug molecules to the appropriate site of action through passive accumulation, thus reducing their severe side effects. However, the need for enhanced circulation time and site and time-specific drug delivery turned research focus on other systems, such as polymers. In this context, novel composites that combine the flexibility of polymeric nanosystems with the properties of liposomes gained a lot of interest. In the present work a mixed/chimeric liposomal system, composed of phospholipids and block copolymers, was developed and evaluated in regards with its feasibility as a drug delivery system. These innovative nano-platforms combine advantages from both classes of biomaterials. Thermal analysis was performed in order to offers an insight into the interactions between these materials and consequently into their physicochemical characteristics. In addition, colloidal stability was assessed by monitoring z-potential and size distribution over time. Finally, their suitability as carriers for biomedical applications was evaluated by carrying out in vitro toxicity studies.

PEO-b-PCL grafted niosomes: The cooperativilty of amphiphilic components and their properties in vitro and in vivo

Niosomes belong to drug delivery systems and consist mainly of non-ionic surfactants and cholesterol. In this study, we designed and developed systems composed of non-ionic surfactants i.e. Tween 80, Span 80 and cholesterol with and without poly(ethylene oxide)-b-poly(ε-caprolactone) (PEO-b-PCL) block copolymer, using different molar ratios of the above components. The nanosystems were formed by the thin-film hydration method with purified water as dispersion medium. Several physicochemical techniques were utilized in order to study the physicochemical and morphological characteristics of the prepared assemblies. The results showed that the presence of the block copolymer alters significantly the size and morphology of neat surfactant/cholesterol niosomes. The ageing studies also revealed that the stability is strongly dependent on the nature and the molar ratios of the components. Moreover, neither of the studied nanosystems exhibited elevated signs of cellular toxicity in vitro nor acute systemic toxicity in vivo short-term experiments. This investigation covers a new field of drug delivery platforms those of niosomes composed by different biomaterials i.e. surfactants and block copolymers.

Comparative Perturbation Effects Exerted by the Influenza A M2 WT Protein Inhibitors Amantadine and the Spiro[pyrrolidine-2,2'-adamantane] Variant AK13 to Membrane Bilayers Studied Using Biophysical Experiments and Molecular Dynamics Simulations

Aminoadamantane drugs are lipophilic amines that block the membrane-embedded influenza A M2 WT (wild type) ion channel protein. The comparative effects of amantadine ( Amt) and its synthetic spiro[pyrrolidine-2,2'-adamantane] (AK13) analogue in dimyristoylphosphatidylcholine (DMPC) bilayers were studied using a combination of experimental biophysical methods, differential scanning calorimetry (DSC), X-ray diffraction, solid-state NMR (ssNMR) spectroscopy, and molecular dynamics (MD) simulations. All three experimental methods pointed out that the two analogues perturbed drastically the DMPC bilayers with AK13 to be more effective at high concentrations. AK13 was tolerated in lipid bilayers at very high concentrations, while Amt was crystallized. This is an important consideration in the formulations of drugs as it designates a limitation of Amt incorporation. MD simulations verify provided details about the strong interactions of the drugs in the interface region between phosphoglycerol backbone and lipophilic segments. The two drugs form hydrogen bonding with both water and sn-2 carbonyls in their amine form or water and phosphate oxygens in their ammonium form. Such localization of the drugs explains the DMPC bilayers reorientation and their strong perturbing effect evidenced by all biophysical methodologies applied.

Development and Evaluation of Stimuli-Responsive Chimeric Nanostructures

Chimeric/mixed stimuli-responsive nanocarriers are promising agents for therapeutic and diagnostic applications, as well as in the combinatorial field of theranostics. Herein, we designed chimeric nanosystems, composed of natural phospholipid and pH-sensitive amphiphilic diblock copolymer, in different molar ratios and assessed the polymer lyotropic effect on their properties. Initially, polymer-grafted bilayers were evaluated for their thermotropic behavior by thermal analysis. Chimeric liposomes were prepared through thin-film hydration and the obtained vesicles were studied by light scattering techniques, to measure their physicochemical characteristics and colloidal stability, as well as by imaging techniques, to elucidate their global and membrane morphology. Finally, in vitro screening of the systems' toxicity was held. The copolymer effect on the membrane phase transition strongly depended on the pH of the surrounding environment. Chimeric nanoparticles were around and above 100 nm, while electron microscopy revealed occasional morphology diversity, probably affecting the toxicity of the systems. The latter was assessed to be tolerable, while dependent on the nanosystems' material concentration, polymer concentration, and polymer composition. All experiments suggested that the thermodynamic and biophysical properties of the nanosystems are copolymer-composition- and concentration-dependent, since different amounts of incorporated polymer would produce divergent effects on the lyotropic liquid crystal membrane. Certain chimeric systems can be exploited as advanced drug delivery nanosystems, based on their overall promising profiles.

Cubic lyotropic liquid crystals as drug delivery carriers: Physicochemical and morphological studies

The self-assembly process of amphiphilic molecules into solvents results in different mesophases, such as inverse cubic and hexagonal that both belong to the wider category of lyotropic liquid crystals. The above mesophases can be further exploited upon the formation of liquid crystalline nanoparticles, cubosomes and hexosomes respectively, which may be utilized as drug delivery nanosystems, exhibiting major advantages. In the present study, liquid crystalline nanoparticles were prepared and evaluated in terms of morphology and physicochemical behavior. The goal of this study is to examine the effect of the different formulation parameters, as well as the effect of the different microenvironmental factors (temperature, ionic strength, pH, serum proteins presence) on their behavior. The physicochemical behavior and the morphology of the systems were investigated by X-Ray Diffraction (XRD), cryogenic-Transmission Electron Microscopy (cryo-TEM), fluorescence spectroscopy and a gamut of light scattering techniques. The formulation process was proved to influence strictly the physicochemical behavior of the prepared nanosystems. They presented colloidal stability over time and upon ionic strength increase, but they were affected by the presence of proteins and presented reversible structure alterations upon temperature increase. Their morphological structure and internal microenvironment, reflected by micropolarity and microfluidity, were also influenced by the formulation parameters.