In vivo Stability of Ester and Ether-Linked Phospholipid-Containing Liposomes as Measured by Perturbed Angular Correlation Spectroscopy (original) (raw)
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Modulation of pharmacokinetic behavior of liposomes
Advanced Drug Delivery Reviews, 1997
The authors's recent work on matters pertinent to the in vivo processing of systemically administered liposomes is reviewed. Particular emphasis is given to factors influencing blood clearance rates, hepatic and splenic uptake and intrahepatic as well as intrasplenic distribution. In addition to size, liposomal composition plays a crucial role in determining these parameters as was shown by comparing the fate of liposomes composed of egg phosphatidylcholine (eggPC), cholesterol (Chol) and either phosphatidylglycerol (PG) or different molar fractions of phosphatidylserine (PS) as negatively charged components. Neutral eggPC/Chol liposomes with and without lipid-anchored poly(ethylene glycol) were also compared. The experimental approach included the measurement of radiolabel distribution from [ 'Hlcholesterylether-labeled liposomes in blood, liver and spleen and in isolated hepatic cell fractions as well as morphological observations on colloidal gold containing liposomes at the light-and electronmicroscopical level. Evidence is presented that apolipoprotein-E plays an important role in the clearance and hepatic uptake and processing of some liposomes but not of others.
Liposomes for the sustained drug release in vivo
Biochimica et Biophysica Acta (BBA) - Biomembranes, 1990
New lipidic carriers suitable for the sustained drug release in vivo are presented. They consist of middle sized, compact phospholipid vesicles with one or up to few lipid bilayers which are sterically stabilized with a small amount of large-head phospholipids. As an example, phosphatidylcholine (PC) liposomes casted with up to 10 mol% of phosphatidylethanolamine with a covalently attached polyethyleneglycol 5000 headgroup (PE-PEG) are discussed. Such vesicles exhibit a very long circulation time after an i.v. administration in mice; the improvement over pure phosphatidylcholine liposomes within the first 24 h exceeds 8000%, at this point nearly 25% of the applied PE-PEG liposomes being still in the circulation. This advantage is a consequence of reduced phagocytosis of the lipidic carriers, as shown by an in vitro assay with blood monocyte cells in the flow cytometric experiments. For example, after 6 h incubation with THP-1 monocyte cells in human plasma the difference between the uptake of standard distearoylphosphatidylcholine (DSPC) and novel liposomes containing 10% distearoylphosphatidylethanolamine-PEG is by 1000%. Vesicles with 2.5 mol% DSPE-PEG are also taken-up via phagocytosis relatively slowly. But the latter vesicles, moreover, retain most of the enclosed model-drug carboxyfluorescein after an incubation in plasma. The rate of permeation of the encapsulated substance from such DSPE-PEG liposomes is below 2.4% per h. This is by approximately a factor of two less than for pure DSPC iiposomes; vesicles with a higher PE-PEG content are inferior in this respect. Long circulation time and high retention of the newly developed liposomes open up ways for the future systemic use as such stabilized drug carriers for the therapeutic applications in vivo.
Liposomes for the Drug Delivery: A Review
2021
Quick Response Code Abstract: Formulation of drugs in liposomes has provided an opportunity to enhance the therapeutic indices of various agents mainly through alteration in their bio distribution. Liposomes are a novel drug delivery system (NDDS), they are vesicular structures consisting of bilayer which form spontaneously when phospholipids are dispersed in water. They are microscopic vesicles in which an aqueous volume is entirely enclosed by a membrane composed of lipid bilayers. The goal of any drug delivery system is spatial placement and temporal delivery of the medicament. Research works are going on to prepare an ideal drug delivery system which satisfies these needs. Liposomes are small vesicles (100 nm) composed various lipid molecules which build their membrane bilayers. These formulations are mainly composed of phosphatidylcholine and other constituents such as cholesterol and lipidconjugated hydrophilic polymers. Liposomes are biodegradable and biocompatible in nature.
A Review on Liposomes as a Drug Delivery System
IJPAR JOURNAL
Nanoparticle systems have been perceived as the ultimate goal for effective drug delivery for decades. The ideal nanoparticle carries the drug-load safely to a predefined target. There, it is capable of releasing its cargo intracellular or in the extracellular space where the drug can be directly internalized and exert the desired action. Enroute, the nanoparticle prevents unwanted interactions of the drug-load with non-target tissues and where needed, it will enhance the circulation time of the encapsulated drug and enable sustained release. In this context, liposomes, a class of synthetic lipid nanoparticles have been explored in depth. Liposomes are microscopic self-assembling unilamellar or multilamellar vesicles made up of phospholipid bilayer. Both the hydrophilic and hydrophobic drugs can be attached to the lipid bilayer of liposomes and can show their efficacy in the target cell of the human body. Liposomes can significantly alter the pharmacokinetics of drugs. They have bee...
Biochimica et Biophysica Acta (BBA) - General Subjects, 1982
The kinetics of [14C]sucrose release from multilamellar liposomes of fixed diameter (approx. 0.23 i~m) incubated in human plasma (serum and blood) were quantified. Composition was various ratios of phosphatidylcholine, phosphatidic acid and cholesterol with a-tocopherol included as antioxidant. Considerable intra-individual variability was noted for liposome stability in blood and its derived fluids, yet reproducible results were obtained for pooled samples. The destabilizing effects of plasma decreased with increasing lipid concentrations. Results of fitting a kinetic model to the data showed that four of five model parameters were linearly related to liposome cholesterol content. Liposomes depleted plasma of its destabilizing factors, and when pre-incubated with plasma were partially stabilized to the effects of a subsequent plasma addition. Plasma caused a rapid rise in liposome membrane permeability which then declined non-linearly, presumably because of a rearrangement of membrane lipids and adsorbed proteins to form their most stable configuration. The therapeutic availability of drugs administered encapsulated in liposomes, which can be governed by the kinetics of their in vivo extracellular release, may be directly proportional to-and predictable from-the time-course and extent of release in plasma. The kinetic model was used in conjuction with simple pharmacokinetic assumptions to show that the effectiveness of a liposome drug carrier cannot be predicted based simply on its plasma stability; more stable liposomes may not be more effective drug carriers. Interestingly, plasma-induced solute release from liposomes serendipitously mimics an important facet of ideal carrier behavior.
Journal of Biotechnology & Biomaterials, 2017
Liposomes are a novel drug delivery system (NDDS), they are vesicular structures consisting of bilalyers which form spontaneously when phospholipids are dispersed in water. They are microscopic vesicles in which an aqueous volume is entirely enclosed by a membrane composed of lipid bilayers. NDDS aims to deliver the drug at a rate directed by the needs of the body during the period of treatment and direct the place of action. Liposomes are colloidal spheres of cholesterol non-toxic surfactants, sphingolipids, glycolipids, long chain fatty acids and even membrane proteins and drug molecules or it is also called vesicular system. It differs in size, composition and charge and drug carrier loaded with variety of molecules such as small drug molecules, proteins, nucleotides or plasmids etc. Few drugs are formulated as liposomes to improve their therapeutic index. Hence a number of vesicular drug delivery systems such as liposomes, niosomes, transfersomes and pharmacosomes are developed. The focus of this chapter is to the various method of preparation, characterization of liposomes, advantages and applications, etc.
Liposomes as drug carriers and their characterization using different analytical methods
The physicochemical properties of liposomes are significantly affected by the composition of phospholipid bilayer; differences in composition allow the use of liposomes for analytical purposes and for therapeutic purposes. One of the most used components of phospholipid bilayer is cholesterol. Its concentration plays a significant role in the behaviour of liposomes. This study points to changes in the properties of liposomes and its influence on encapsulated doxorubicin according to the content of cholesterol in the phospholipid bilayer. The influence of SDS addition to liposomal variants was also evaluated. Three variants of liposomes differing in various concentrations of cholesterol were assessed. Firstly, the toxicity of all types of liposomal doxorubicin was evaluated and it was found that the content of cholesterol increases the IC50 values of encapsulated doxorubicin in liposome. The highest concentration of cholesterol in liposome increased the IC50 value even four times com...
Review on Liposomes as a Drug Delivery System
DrSriram Publications, 2023
Nanoparticle systems have been perceived as the ultimate goal for effective drug delivery for decades. The ideal nanoparticle carries the drug-load safely to a predefined target. There, it is capable of releasing its cargo intracellular or in the extracellular space where the drug can be directly internalized and exert the desired action. Enroute, the nanoparticle prevents unwanted interactions of the drug-load with non-target tissues and where needed, it will enhance the circulation time of the encapsulated drug and enable sustained release. In this context, liposomes, a class of synthetic lipid nanoparticles have been explored in depth. Liposomes are microscopic self-assembling unilamellar or multilamellar vesicles made up of phospholipid bilayer. Both the hydrophilic and hydrophobic drugs can be attached to the lipid bilayer of liposomes and can show their efficacy in the target cell of the human body. Liposomes can significantly alter the pharmacokinetics of drugs. They have been investigated for diverse applications such as treatment of cancer, delivery of gene and vaccine, treatment of lung and skin diseases, treatment of tumours, and imaging tumours at the site of infection. They are leading present-day smart delivery systems due to their flexible biophysical and physicochemical properties, which permit easy control to address different delivery concerns. This review will discuss various advances and updates in liposome-assisted drug delivery and the current clinical use of liposomes for biomedical applications.
Liposomes: A targeted drug delivery system- A review
2015
Liposomes are a novel drug delivery system (NDDS), which are vesicular structures consisting of hydrated bilalyers which form spontaneously whenphospholipids are dispersed in water. They are simple microscopic vesicles in which an aqueous volume is entirely enclosed by a membrane composed of lipid bilayers. Novel drug delivery system aims to deliver the drug at a rate directed by the needs of the body during the period of treatment, and channel the active entity to the siteof action. It has been a study interest in the development of a NDDS. Liposomes are colloidal spheres of cholesterol non-toxic surfactants, sphingolipids, glycolipids, long chain fatty acids and even membrane proteins and drug molecules or it is also called vesicular system. It is differ in size, composition and charge. It is a drug carrier loaded with great variety of molecules such as small drug molecules, proteins, nucleotides and even plasmids. Few drugs are also formulated as liposomes to improve their therap...
FEBS Letters, 1996
Transfer of MPEG19oo-DSPE from micellar phase to pre-formed liposomes imparts long in vivo circulation half-life to an otherwise rapidly cleared lipid composition. MPEG19oo-DSPE transfers efficiently and quickly in a time and temperature dependent manner. There is negligible content leakage and a strong correlation between assayed mol% MPEG19oo-DSPE, liposome diameter increase, and pharmacokinetic parameters such as distribution phase half-life. Since a biological attribute (liposome clearance rate) can be modified by the insertion process, it suggests a simple and economical way to impart sitespecific targeting to a variety of liposome delivery systems. This method is also a convenient way to measure the 'brush' thickness of such conjugates directly.