Liposomes
Danilo D. Lasic in LIPOSOMES in GENE DELIVERY, 2019
Liposomes are vesicular colloidal particles composed of self-assembled amphiphilic molecules. Amphiphiles are molecules that contain two groups with different solubility. The hydrophilic group, often referred to as the polar head, is “water loving,” while the hydrophobic part, the so-called nonpolar tail, is “water hating.” Therefore, these molecules self-assemble and form ordered structures in aqueous solutions. Single-chain amphiphiles, such as soaps and detergents, form micelles. These are small spherical structures in which surface polar heads shield the nonpolar interior against water. Many natural amphiphiles, such as lecithin (diacyl phosphatidylcholine), have two nonpolar tails and due to a bulky nonpolar part cannot be packed into micelles. These molecules normally self-assemble into lipid bilayers in which two polar surfaces shield the nonpolar interior. Bilayered lamellae have their edges exposed to water, therefore, at lower concentrations they self-close into spherical structures to eliminate this unfavorable exposure, and lipid vesicles or liposomes are formed. Figure 6-1 shows the structure of micelles and lipid bilayers schematically.
Nanoparticle-Based Medicines: A Review of FDA-Approved Materials and Clinical Trials to Date *
Valerio Voliani in Nanomaterials and Neoplasms, 2021
Polymeric micelles consist of self-assembled polymeric amphiphiles tailored for controlled delivery of hydrophobic drugs. Through careful design of the hydrophobic/hydrophilic balance in the amphiphile, the size and morphology of the assembled micelles can be controlled. The internal core is hydrophobic and can be used to encapsulate poorly water-soluble drugs, whereas the exterior surface is polar enough to allow dissolution in aqueous solution. The use of block copolymers as the amphiphiles has led to lower critical micelle concentration (CMC) and thus higher stability in comparison to traditional surfactant-based micelles [40]. To date, a traditional micellar formulation of estradiol (Estrasorb™) is the only FDA-approved micelle, indicated as a topical treatment for moderate to severe vasomotor symptoms of menopause. Transdermal delivery avoids first pass metabolism and also gastrointestinal side-effects, leading to stable serum levels for 8–14 days [41]. Beyond this example, a number of micelle formulations are in late-stage clinical trials.
Nanocarriers as an Emerging Platform for Cancer Therapy
Lajos P. Balogh in Nano-Enabled Medical Applications, 2020
Lipid-based carriers have attractive biological properties, including general biocompatibility, biodegradability, isolation of drugs from the surrounding environment, and the ability to entrap both hydrophilic and hydrophobic drugs. Through the addition of agents to the lipid membrane or by the alteration of the surface chemistry, properties of lipid-based carriers, such as their size, charge, and surface functionality, can easily be modified. Liposomes, polymersomes, and micelles represent a class of amphiphile-based particles. Liposomes are spherical, self-closed structures formed by one or several concentric lipid bilayers with inner aqueous phases. Today, liposomes are approved by regulatory agencies to carry a range of chemotherapeutics [26, 71, 72] (Table 2.1).
Multifunctional and stimuli-responsive nanocarriers for targeted therapeutic delivery
Published in Expert Opinion on Drug Delivery, 2021
Joydeb Majumder, Tamara Minko
Nanocarriers which can change their certain property upon endogenous or exogenous stimuli, offered a wide range of biomedical applications including controlled release of therapeutics directly at the desired site thereby reducing side effects in the surrounding healthy tissue [114]. Such nanocarriers are referred to as stimuli-responsive nanocarriers, which have attracted enormous attention in recent years in the field of targeted drug delivery from various research groups throughout the world. Stimuli-responsive nanocarriers are generally made of a hydrophobic inner core and a hydrophilic or amphiphilic outer shell, which is usually an amphiphilic stimulus-responsive polymer sensitive to various endogenous or exogenous stimuli. The amphiphilic compound can be any of the natural lipids or lipid like materials or surfactants which are usually pH, redox, temperature, light, enzyme, or magnetic responsive polymers. For some nanocarriers, the hydrophobic part of amphiphilic polymers is modified with cationic groups for conjugating anionic agents such as nucleic acids in the hydrophobic core [115]. In addition, these nanocarriers sometime contain another component such as a targeting ligand or adhesion ligand which is specific to its receptor on target cells or tissues. Various stimuli-sensitive nanocarriers developed for drug and gene delivery application have been summarized in Table 2 [34,38,39,40,116–126]. We will be discussing various endogenous or exogenous stimuli-responsive nanocarriers for targeted therapeutic delivery applications.
Vesicle formation mechanisms: an overview
Published in Journal of Liposome Research, 2021
Chandra Has, Sharadwata Pan
According to symmetry and charge distribution, molecules can be roughly divided into two categories, i.e. polar and non-polar. Polar molecules are soluble in a polar solvent (e.g. ethanol in water) and insoluble in a non-polar solvent (e.g. oil in water), and vice versa (Lasic 1993). Some molecules (such as phospholipids, surfactants, and copolymers) contain both polar and non-polar groups, commonly known as amphiphiles. As these amphiphiles possess both hydrophilic and hydrophobic interactions, they can self-assemble and form ordered structures in an aqueous milieu. Depending on amphiphiles molecular shape, their self-assembly in water results in several phases, e.g. some organise into small spherical, globular or cylindrical micelles, while the others appear to assemble into spherical vesicles, bicontinuous cubic phases or planner bilayers (Lasic 1993, Sterling 1993, Guida 2010).
Novel nano-pomegranates based on astragalus polysaccharides for targeting ERα-positive breast cancer and multidrug resistance
Published in Drug Delivery, 2020
Bingjie Wang, Chunjing Guo, Yanhui Liu, Guangting Han, Yi Li, Yanchun Zhang, Haiyu Xu, Daquan Chen
Of the different nano-delivery systems constructed, micelles are extraordinary and magnetic, owing to their unique properties. Many researchers have used micelles to construct nano-delivery systems (Greish et al., 2018; Yotsumoto et al., 2018; Du et al., 2019; Mu et al., 2019; Song et al., 2019). First, micelles are formed by the self-assembly of amphiphilic materials. If the hydrophobicity of their constituent materials changes under strong external conditions, the micelles disintegrate and the drugs are rapidly released from the micelles. Second, the micelles have a large hydrophobic cavity structure, which allows the loading of many drugs. Third, the outside of the micelles can be easily modified with many target ligands or monoclonal antibody molecules, greatly improving the targeting of micelles (Yu et al., 2018). In our study, micelles were selected to deliver curcumin (Cur) to achieve anti-breast cancer effects.
Related Knowledge Centers
- Chemical Compound
- Detergent
- Hydrocarbon
- Micelle
- Phospholipid
- Surfactant
- Cell Membrane
- Soap
- Lipid Polymorphism
- Bolaamphiphile