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.
Improved Silymarin Characteristics for Clinical Applications by Novel Drug Delivery Systems
Madhu Gupta, Durgesh Nandini Chauhan, Vikas Sharma, Nagendra Singh Chauhan in Novel Drug Delivery Systems for Phytoconstituents, 2020
Another nanostructure of lipids in water is cubosomes, which are the self-assembled cubic crystalline structures of amphiphilic lipids with networks of water channels (Figure 10.2) and can be used as a favorable system for the delivery of hydrophilic, amphiphilic, and hydrophobic drugs due to the presence of lipid and water phase, its large surface area, and good features for the sustained release of the enclosed agent. Amphiphilic lipids including monoglycerides, phospholipids, urea-based lipids, and glycolipids can be considered in this regard. However, the unsaturated monoglycerides are the most commonly studied material. Glycerylmonooleate (GMO) and mixtures of GMO with other lipids or its structural derivatives are the most popular agent in cubosome preparation. GMO is biodegradable and safe for human oral drug delivery (Pan et al., 2013). Silymarin as a poor soluble agent was loaded on glyceryl monooleate/poloxamer 407 liquid crystalline matrices (GMO/P407 LCM). This delivery system could significantly increase maximum plasma concentration for silymarin and also increase oral bioavailability (Lian et al., 2011).
Liquorice and Chinese herbal medicine
Vivienne Lo, Michael Stanley-Baker, Dolly Yang in Routledge Handbook of Chinese Medicine, 2022
The special place given to liquorice may possibly be explained by an examination of the chemistry of the glycyrrhizin molecule. As mentioned previously, one half of the molecule (the sugar half) is hydrophilic, while the other half (the steroid part) is hydrophobic. Molecules of this type are known as amphiphilic. An aqueous environment causes glycyrrhizin molecules to aggregate rather than dissolve, probably in the form of a sphere (although cylindrical aggregates are possible) (Zhang, Wang, Wang and Yu 2006) with the hydrophobic part of the molecules pointing in, and the sugar part on the outside hydrogen bonding to water molecules in the solvent. There is good physical evidence to support this view. A mass spectroscopic study with glycyrrhetinic acid revealed that, in the spectrometer, aggregates of up to eight molecules form readily (Borisenko, Lekar, Vetova et al. 2016).
Multifunctional and stimuli-responsive nanocarriers for targeted therapeutic delivery
Published in Expert Opinion on Drug Delivery, 2021
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
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).
Destruction of Pseudomonas aeruginosa pre-formed biofilms by cationic polymer micelles bearing silver nanoparticles
Published in Biofouling, 2020
Tsvetelina Paunova-Krasteva, Emi Haladjova, Petar Petrov, Aleksander Forys, Barbara Trzebicka, Tanya Topouzova-Hristova, Stoyanka R. Stoitsova
One important target for destruction of mature biofilms is the EPS or the permeability barrier it creates (Koo et al. 2017). If it is destroyed, this would result in both biofilm dispersal and enhanced access of antibiotics to the biofilm bacteria (Roizman et al. 2017). Different possible ways to destroy or at least loosen the EPS have been tested. Since the EPS is mostly anionic, one approach is to permeabilize it with cationic substances (Chen et al. 2014; Powell et al. 2018), and these have for instance been included in some anti-biofilm hydrogels (Li et al. 2018). Amphiphilic molecules have also been considered. As an example, surfactants (Li et al. 2018; Tyldesley et al. 2019) and biosurfactants (Simões et al. 2006; Vasudevan and Prabhune 2018) have been applied, with variable success. Chemical targets in the EPS can be its major components, hence enzymatic dissolution of eDNA, proteins and polysaccharides may also be effective (Roy et al. 2018).
Related Knowledge Centers
- Chemical Compound
- Detergent
- Hydrocarbon
- Micelle
- Phospholipid
- Surfactant
- Cell Membrane
- Soap
- Lipid Polymorphism
- Bolaamphiphile