Liposomes entrapping β-cyclodextrin/ibuprofen inclusion complex: Role of the host and the guest on the bilayer integrity and microviscosity

Cyclocurcumin as Promising Bioactive Natural Compound: An Overview

Although identical in molecular formula and weight, curcumin and cyclocurcumin show remarkable differences in their reactivity. Both are natural compounds isolated from the rhizome of turmeric, the former is involved in the diketo/keto-enol tautomerism through the bis-α,β-unsaturated diketone unit according to the polarity of the solvent, while the latter could react by trans-cis isomerization due to the presence of the α,β-unsaturated dihydropyranone moiety. Even if curcumin is generally considered responsible of the therapeutical properties of Curcuma longa L. due to its high content, cyclocurcumin has attracted great interest over the last several decades for its individual behavior and specific features as a bioactive compound. Cyclocurcumin has a hydrophobic nature characterized by fluorescence emission, solvatochromism, and the tendency to form spherical fluorescent aggregates in aqueous solution. Molecular docking analysis reveals the potentiality of cyclocurcumin as antioxidant, enzyme inhibitor, and antiviral agent. Promising biological activities are observed especially in the treatment of degenerative and cardiovascular diseases. Despite the versatility emerging from the data reported herein, the use of cyclocurcumin seems to remain limited in clinical applications mainly because of its low solubility and bioavailability.

On the relationship between the properties of planar structures of non-ionic surfactants and their vesicular analogues - Niosomes

In recent years, the study of niosomes as nanocarriers alternative to liposomes has received increasing attention. In contrast to well-studied liposome membranes, many aspects of the behavior of analogous niosome bilayers have not been studied. This paper considers one of these aspects related to the communication between the physicochemical properties of planar and vesicular objects. We present the first results of comparative studies of Langmuir monolayers of binary and ternary (with cholesterol) mixtures of non-ionic surfactants based on sorbitan esters and niosomal structures assembled from the same materials. The Thin-Film Hydration (TFH) method in the gentle shaking version was used to produce the particles of large sizes, while small unilamellar high quality vesicles with a unimodal distribution of particles were prepared by TFH using ultrasonic treatment and extrusion. An analysis of the structural organization and phase state of monolayers based on compression isotherms and supplemented by thermodynamic calculations, as well as the results of determining the particle morphology, polarity and microviscosity of niosome shells, made it possible to obtain fundamental data on the intermolecular interactions of the components and their packing in shells and to relate these data to the properties of niosomes. This relationship can be used to optimize the composition of niosome membranes and predict the behavior of these vesicular systems. It was shown that cholesterol excess creates regions of bilayers with increased rigidity (like "lipid rafts"), which hinders the process of folding film fragments into small niosomes.

Preparation of DRV Liposomes

Dried reconstituted vesicle (DRV) liposomes are formulated under mild conditions. The method has the capability to entrap substantially higher amounts of hydrophilic solutes, compared to other passive-loading liposome preparation methods. These characteristics make this liposome type ideal for entrapment of labile substances, such as peptides, proteins, or DNA's (or other nucleotides or oligonucleotides), or in general biopharmaceuticals and sensitive drugs. In this chapter, all possible types of DRV liposomes (in respect to the encapsulated molecule characteristics and/or their applications in therapeutics) are introduced, and preparation methodologies (for each type) are described in detail.

Targeted Carbon Nanostructures for Chemical and Gene Delivery to Plant Chloroplasts

Nanotechnology approaches for improving the delivery efficiency of chemicals and molecular cargoes in plants through plant biorecognition mechanisms remain relatively unexplored. We developed targeted carbon-based nanomaterials as tools for precise chemical delivery (carbon dots, CDs) and gene delivery platforms (single-walled carbon nanotubes, SWCNTs) to chloroplasts, key organelles involved in efforts to improve plant photosynthesis, assimilation of nutrients, and delivery of agrochemicals. A biorecognition approach of coating the nanomaterials with a rationally designed chloroplast targeting peptide improved the delivery of CDs with molecular baskets (TP-β-CD) for delivery of agrochemicals and of plasmid DNA coated SWCNT (TP-pATV1-SWCNT) from 47% to 70% and from 39% to 57% of chloroplasts in leaves, respectively. Plants treated with TP-β-CD (20 mg/L) and TP-pATV1-SWCNT (2 mg/L) had a low percentage of dead cells, 6% and 8%, respectively, similar to controls without nanoparticles, and no permanent cell and chloroplast membrane damage after 5 days of exposure. However, targeted nanomaterials transiently increased leaf H₂O₂ (0.3225 μmol gFW^-1) above control plant levels (0.03441 μmol gFW^-1) but within the normal range reported in land plants. The increase in leaf H₂O₂ levels was associated with oxidative damage in whole plant cell DNA, a transient effect on chloroplast DNA, and a decrease in leaf chlorophyll content (-17%) and carbon assimilation rates at saturation light levels (-32%) with no impact on photosystem II quantum yield. This work provides targeted delivery approaches for carbon-based nanomaterials mediated by biorecognition and a comprehensive understanding of their impact on plant cell and molecular biology for engineering safer and efficient agrochemical and biomolecule delivery tools.

Thermoresponsive Liposomes for Photo-Triggered Release of Hypericin Cyclodextrin Inclusion Complex for Efficient Antimicrobial Photodynamic Therapy

Antimicrobial strategies with high efficacy against bacterial infections are urgently needed. The development of effective therapies to control bacterial infections is still a challenge. Herein, near-infrared (NIR)-activated thermosensitive liposomes (TSL) were loaded with the NIR-dye 1,1-dioctadecyl-3,3,3,3-tetramethylindotricarbocyanine iodide (DiR) and the water-soluble hypericin (Hyp) β-cyclodextrin inclusion complex (Hyp-βCD). DiR and Hyp-βCD loaded thermosensitive liposomes (DHβCD-TSL) are functionalized for photothermal triggered release and synergistic photodynamic therapy to eliminate the gram-positive Staphylococcus saprophyticus. The dually active liposomes allow the production of heat and singlet oxygen species with the help of DiR and Hyp, respectively. The elevated temperature, generated by the NIR irradiation, irreversibly damages the bacterial membrane, increases the permeation, and melts the liposomes via a phase-transition mechanism, which allows the release of the Hyp-βCD complex. The photodynamic effect of Hyp-βCD eradicates the bacterial cells owing to its toxic oxygen species production. DHβCD-TSL measured the size of 130 nm with an adequate encapsulation efficiency of 81.3% of Hyp-βCD. They exhibited a phase transition temperature of 42.3 °C, while they remained stable at 37 °C, and 44% of Hyp-βCD was released after NIR irradiation (T > 47 °C). The bacterial viability dropped significantly after the synergistic treatment (>4 log₁₀), indicating that the NIR-activated TSL have immense therapeutic potential to enhance the antibacterial efficacy. The liposomes showed good biocompatibility, which was confirmed by the cellular viability of mouse fibroblasts (L929).

Cyclodextrins-in-Liposomes: A Promising Delivery System for Lippia sidoides and Syzygium aromaticum Essential Oils

Biological activity of essential oils (EOs) has been extensively reported; however, their low aqueous solubility, high photosensitivity, and volatility compromise a broad industrial use of these compounds. To overcome these limitations, we proposed a nanoencapsulation approach to protect EOs, that aims to increase their stability and modulate their release profile. In this study, drug-in-cyclodextrin-in-liposomes encapsulating two essential oils (Lippia sidoides and Syzygium aromaticum) and their respective major compounds (thymol and eugenol) were produced by ethanol injection and freeze-dried to form proliposomes and further physicochemically characterized. Liposomes showed high physical stability over one month of storage at 4 °C, with slight changes in the mean size, polydispersity index (PDI), and zeta potential. Reconstituted proliposomes showed a mean size between 350 and 3300 nm, PDI from 0.29 to 0.41, and zeta potential between -22 and -26 mV. Differential scanning calorimetry and X-ray diffraction of proliposomes revealed a less-ordered crystalline structure, leading to high retention of the major bioactive compounds (between 73% and 93% for eugenol, and 74% and 84% for thymol). This work highlights the advantages of using drug-in-cyclodextrin-in-liposomes as delivery systems to retain volatile compounds, increasing their physicochemical stability and their promising potential to be utilized as carriers in products in the pharmaceutical, food, and cosmetic industries.

Liposomes as vehicles for topical ophthalmic drug delivery and ocular surface protection

Introduction: The development of ophthalmic formulations able to deliver hydrophilic and hydrophobic drugs to the inner structures of the eye and restore the preocular tear film has been a leading topic of discussion over the last few years. In this sense, liposomes represent a suitable strategy to achieve these objectives in ocular drug delivery.Areas covered: Knowledge of the different physiological and anatomical eye structures, and specially the ocular surface are critical to better understanding and comprehending the characteristics required for the development of topical ophthalmic liposomal formulations. In this review, several features of liposomes are discussed such as the main materials used for their fabrication, basic structure and preparation methods, from already established to novel techniques, allowing the control and design of special characteristics. Besides, physicochemical properties, purification processes and strategies to overcome delivery or encapsulation challenges are also presented. Expert opinion: Regarding ocular drug delivery of liposomes, there are some features that can be redesigned. Specific biocompatible and biodegradable materials presenting therapeutic properties, such as lipidic compounds or polymers significantly change the way of tackling ophthalmic diseases. Besides, liposomes entail an effective, safe and versatile strategy for the treatment of diseases in the clinical practice.

Assessment of various formulation approaches for the application of beta-lapachone in prostate cancer therapy

Beta-lapachone (β-Lap) is an anticancer drug activated by the NAD(P)H:quinone oxidoreductase (NQO1), an enzyme over-expressed in a large variety of tumors. B-Lap is poorly soluble in water and in most biocompatible solvents. Micellar systems, liposomes and cyclodextrins (CDs) have been proposed for its solubilization. In this work, we analyzed the properties and in vitro efficacy of β-Lap loaded in polymer nanoparticles, liposome bilayers, complexed with sulfobutyl-ether (SBE)- and hydroxypropyl (HP)-β cyclodextrins, or double loaded in phospholipid vesicles. Nanoparticles led to the lowest drug loading. Encapsulation of [β-Lap:CD] complexes in vesicles made it possible to slightly increase the encapsulation rate of the drug in liposomes, however at the cost of poor encapsulation efficiency. Cytotoxicity tests generally showed a higher sensitivity of NIH 3T3 and PNT2 cells to the treatment compared to PC-3 cells, but also a slight resistance at high β-Lap concentrations. None of the studied β-Lap delivery systems showed significant enhanced cytotoxicity against PC-3 cells compared to the free drug. Cyclodextrins and double loaded vesicles, however, appeared more efficient drug delivery systems than liposomes and nanoparticles, combining both good solubilizing and cytotoxic properties. Ligand-functionalized double loaded liposomes might allow overcoming the lack of selectivity of the drug.

Complex systems that incorporate cyclodextrins to get materials for some specific applications

Cyclodextrins (CDs) are a family of biodegradable cyclic hydrocarbons composed of α-(1,4) linked glucopyranose subunits, the more common containing 6, 7 or 8 glucose units are named α, β and γ-cyclodextrins respectively. Since the discovery of CDs, they have attracted interest among scientists and the first studies were about the properties of the native compounds and in particular their use as catalysts of organic reactions. Characteristics features of different types of cyclodextrins stimulated investigation in different areas of research, due to its non-toxic and non-inmunogenic properties and also to the development of an improved industrial production. In this way, many materials with important properties have been developed. This mini-review will focus on chemical systems that use cyclodextrins, whatever linked covalently or mediated by the non covalent interactions, to build complex systems developed mainly during the last five years.

Effect of the Incorporation of Functionalized Cyclodextrins in the Liposomal Bilayer

Liposomes loaded with drug–cyclodextrin complexes are widely used as drug delivery systems, especially for species with low aqueous solubility and stability. Investigation of the intimate interactions of macrocycles with liposomes are essential for formulation of efficient and stable drug-in-cyclodextrin-in-liposome carriers. In this work, we reported the preparation of unilamellar vesicles of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) embedded with native β-cyclodextrin and two synthetic derivatives: heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin (TMCD) and heptakis(2,3-di-O-acetyl)-β-cyclodextrin (DACD). We then studied the effect of these macrocycles on the liposomal size, membrane viscosity, and liposomal stability at different temperatures and concentrations. We observed that TMCD and DACD affected vesicle size and the change of size was related to CD concentration. Irrespective of its nature, the macrocycle established interactions with the phospholipidic head groups, preventing cyclodextrins to diffuse into the lipid bilayer, as confirmed by molecular dynamics simulations. Such supramolecular structuring improves liposome stability making these colloid systems promising carriers for biologically active compounds.