Materials for liposomes

Liposomes are the microvesicles that have an aqueous chamber surrounded by amphiphilic molecular bilayers. Thus, liposomes administered into the body are mainly taken up by the reticuloendothelial system, thereby stimulating an autoimmune response in the body. The encapsulation alters the drug absorption and distribution within the body. The drug can accumulate in the heart, liver, lungs, bones, marrow, and other tissues and organs, contributing to reducing the dose of therapeutic drugs and toxicity from drugs, thus achieving the purpose of targeted drug delivery. BOC Sciences provides its customers with high quality raw materials for the preparation of liposomes. All materials are prepared under sterile conditions. In addition, we offer a range of many types of liposomal products for you to choose from. At BOC Sciences, you're sure to make a difference in liposomes.

Liposomes Raw Materials

The raw materials used in the formulation of liposomes are major factors in terms of integrity, both at a structural and functional level. The general type of building blocks involves phospholipids as main constituents, which compose the essential lipid bilayer acting in the encapsulation of the therapeutic agents. Commonly used phospholipids include phosphatidylcholine (PC) , phosphatidylethanolamine (PE) , and phosphatidylglycerol (PG) . These lipids can be derived from both natural sources, such as soy or egg lecithin, and synthetic production.

Schematic diagram of liposome structure.

Key Phospholipids in Liposome Formulation

(1) Neutral Phospholipids

• Phosphatidylcholine (PC) : Widely used for its biocompatibility and ability to form stable liposomes.
• Phosphatidylethanolamine (PE) : Known for enhancing membrane fluidity and facilitating drug encapsulation.
• Sphingomyelin (SM): Increases mechanical stability, protecting sensitive biologics within liposomes.

(2) Negative Charged Phospholipids (Acidic Phospholipids)

• Phosphatidic Acid (PA) : Enhances membrane curvature and fluidity, improving cell uptake.
• Phosphatidylglycerol (PG) : Provides charge and contributes to liposome stability.
• Phosphatidylserine (PS) : Improves cellular uptake and targeting, particularly in cancer therapies.
• Phosphatidylinositol (PI): Facilitates targeting by allowing attachment of specific ligands for enhanced selectivity.

(3) Positive-charged Lipids

• Sterylamine (SA): Cationic lipid that aids in gene delivery by promoting electrostatic interactions with nucleic acids.

(4) Stigmasterol and Its Glucoside

• Sterol Glycosides (SG): Enhances liposomal stability and fluidity, beneficial for sensitive biomolecules.
• Soybean Sterol (SS): Natural plant-derived sterol that stabilizes membranes and extends liposome shelf life.

(5) Cholesterol

Cholesterol: Provides structural integrity and reduces permeability, extending drug circulation time.

Selecting the appropriate phospholipids is critical, as they not only affect the liposome's mechanical properties but also influence drug release profiles and bio-distribution in vivo.

Liposomes Composition

The composition of liposomes plays a vital role in determining their stability, drug loading capacity, and release kinetics. The hydrophilic end of the phospholipid molecule is curved in an arc and combines with the hydrophilic group of the cholesterol molecule to form a "U" shaped structure. The two "U" shaped structures are arranged opposite each other to form a bimolecular structure. A typical liposome consists of a lipid bilayer, an aqueous core, and sometimes additional components such as cholesterol and surfactants.

Lipid Bilayer and Cholesterol

• Cholesterol : Commonly added to the formulation of liposomes. Cholesterol helps in maintaining membrane fluidity and stability, especially when the conditions in the environment are fluctuating. By preventing early leakage, it holds the cargo of the liposomes until it reaches the target site.
• Surfactants: Nonionic surfactants, such as Polysorbate 80, are usually added to most formulations because of the enhanced solubility of the lipid mixture and the surface tension reduction. It speaks for the fact that the dispersions of liposomes after such modifications are more homogeneous, which is the necessary condition for maintaining consistent drug delivery.

Encapsulated Agents

Various substances can be encapsulated in the membrane composed of the aqueous phase and lipid bilayer of liposomes:

• Hydrophilic Drugs: These drugs are encapsulated into the aqueous core of the liposome and are ideal for molecules such as nucleic acids, which need protection from degradation and a very efficient transport system to enter the cells.
• Hydrophobic Drugs: Hydrophobic drugs are incorporated into the lipid bilayer. This enhances not only the bioavailability of lipophilic compounds but also allows for controlled release of the drug over time.
• Fat-soluble Drugs: Fat-soluble, or lipophilic, drugs are commonly encapsulated within the lipid bilayer of the liposome due to the fact that they can be well incorporated into the hydrophobic interior of the phospholipid membrane. This embedding in the lipid bilayer will improve the bioavailability of poorly water-soluble drugs and enhance their therapeutic potency.
• Amphoteric Compounds: Amphoteric compounds are capable of behaving both as acids and bases, their delivery can be quite challenging due to variable charges under variable pH conditions. Liposomes afford an adaptive environment for such drugs because they can encapsulate amphoteric compounds either in the lipid bilayer or in the aqueous core, depending on the pH of the medium and the conditions of formulation.

Raw Material for Liposome Manufacturing from BOC Sciences

BOC Sciences specializes in supplying high-quality raw materials necessary for efficient liposome production, including premium phospholipids, cholesterol, and cryoprotectants essential for maintaining liposome stability during storage and transport. BOC Sciences recognizes that the integrity of each component used in liposome synthesis significantly affects the final product's quality and reliability, particularly in pharmaceutical applications where precision is paramount.

Key Materials for Liposomes from BOC Sciences

• Phospholipids : BOC Sciences provides a wide variety of natural and synthetic phospholipids, allowing researchers to choose formulations that meet specific stability and release profile requirements.
• Cholesterol : With BOC Sciences' high-grade cholesterol, liposomal formulations can achieve enhanced durability, especially useful for drug delivery applications requiring extended circulation times.
• Cryoprotectants: For formulations that involve lyophilization (freeze-drying), cryoprotectants such as sucrose and trehalose are available to prevent liposome damage during freezing. This feature is crucial for ensuring long-term stability of liposome formulations, particularly those carrying temperature-sensitive therapeutic agents.

Through BOC Sciences' rigorous quality control and extensive catalog, researchers can rely on consistent and pure materials, which form the foundation of robust liposomal drug delivery systems.

Liposome Preparation Protocol

The preparation of liposomes involves multiple steps to ensure a homogenous dispersion and optimal encapsulation of active agents. The most common preparation method includes the following steps:

• Lipid Film Hydration: Initially, a mixture of phospholipids and cholesterol is first dissolved in an organic solvent. Evaporation of the solvent results in a thin film of the lipids on the walls of the container. Hydration of the film with an aqueous solution that may contain the therapeutic agent results in spontaneous formation of liposomes.
• Size Reduction and Homogenization: The hydrated film is then either sonicated or extruded, allowing the size reduction of the particles and distributing them uniformly. Sonication relies on ultrasonic waves that break larger vesicles into smaller ones, whereas in extrusion, the suspension of liposomes is passed through membranes with specified pore sizes to uniformly distribute the particle size.
• Freeze-Thaw Cycles: Freeze-thaw cycles are used as one of the methods of enhancing encapsulation efficiency and stability. The process consists of freeze-thaw cycling of the suspension of liposomes in liquid nitrogen and subsequent thawing at temperatures close to the lipid transition point.
• Optional Lyophilization: The process of lyophilization or freeze-drying of formulations imparts long-term stability to the formulations. The process involves removal of water by sublimation, hence converting the liposomes into powder form, which could be reconstituted later. In this process, cryoprotectants like sucrose are added, which provide protection to the liposome structure.
• Characterization: When ready, liposomes are subjected to a detailed characterization involving the size of the particles, zeta potential, encapsulation efficiency, and stability. This is important information that will be used to ascertain if the specifications for the liposomes are within required limits for intended application.

BOC Sciences offers technical support for liposome preparation, ensuring users achieve the desired product quality and reproducibility in every batch.

Liposomes Raw Material in Drug Delivery

In drug delivery applications, the quality and composition of liposomal raw materials are of prime importance to therapeutic efficacy. Careful selection of lipids, stabilizers, and surfactants can potentially influence biodistribution, cellular uptake, and release kinetics of the drug-loaded liposomes.

Enhancing Targeted Drug Delivery

Targeted drug delivery should be enabled by engineering the liposomal surface with specific ligands such as antibodies, peptides, or folic acid, which could interact with their respective cognate receptors on the surface of the target cells. This approach is very important in cancer treatment, where liposomes can selectively accumulate in tumor tissues and reduce damage to normal cells, hence reducing side effects. BOC Sciences offers functional lipids and conjugation reagents to support targeted liposome design by ligand attachment, which would greatly enhance the therapeutic specificity and efficiency of liposomal drugs.

Improving Bioavailability and Stability

Liposomal formulations enhance the bioavailability of poorly soluble drugs by incorporating them into the lipid bilayer, which facilitates absorption in biological environments. Stability is further increased by using high-grade cholesterol and stabilizing agents provided by BOC Sciences, which mitigate premature drug release and degradation.

New Liposome Raw Materials

With the development of liposomal technology, designing new, innovative raw materials is of high importance in solving existing limitations with respect to stability, targeting, and controlled release. These novel materials will be designed specifically for improving liposome performance upon their various applications, such as oncology, immunotherapy, gene delivery, and vaccine development. Thus, these materials, emphasizing enhanced stability, bioavailability, and targeted delivery, have contributed much to the expansion of possibilities for the application of liposomal drug carriers. Under the broad category, advanced materials supplied by BOC Sciences are supportive in efforts to drive breakthroughs concerning formulation and functionality.

Synthetic Lipids and Polymeric Materials

• Advanced Synthetic Lipids

Traditional lipids indeed face problems of stability in physiological conditions. BOC Sciences provides the next generation of synthetic lipids designed to achieve better durability, less oxidation, and even environmental responsiveness, such as pH and temperature. Such developments, like pH-sensitive lipids for tumor environments, allow considerably higher drug delivery precision with fewer off-target effects.

• Biodegradable Polymers

Biodegradable polymers, such as PLGA and PCL, serve to enhance the efficacy of liposomes through controlled and sustained drug release. These predictably degrading polymers have very important value in treatments that require extended exposure. With tunable degradation rates, the polymers provided by BOC Sciences allow for tailored release profiles, benefiting applications requiring prolonged therapeutic action.

PEGylation and Surface Modification Agents

• Polyethylene Glycol (PEG)

PEGylation improves the pharmacokinetics of liposomes by increasing circulation time and reducing immunogenicity. The enhanced tumor accumulation is facilitated by this effect. PEG agents supplied by BOC Sciences are available in various molecular weights to ensure the optimal performance of stealth liposome formulations by balancing circulation time with targeting efficiency.

• Targeting Ligands

Targeting ligands can be attached to the surface of liposomes for high precision in delivery, which usually contains certain antibodies or peptides. BOC Sciences supports such modifications, enabling selective uptake by specific cells with minimal exposure to non-target tissues being a priceless approach in targeting receptors of cancer cells or other therapeutic targets.

Bio-inspired Lipids and Peptides

• Biomimetic Lipid Components

Biomimetic liposomes are designed to be highly biocompatible by imitating the cell membrane; for this reason, it mediates cell uptake and intracellular delivery. Bio-inspired lipids in BOC Sciences results in an improvement of the grade of membrane fusion, hence enabling reduced immune activation; this is exemplified in gene therapy where cellular internalization is needed.

• Peptide-Lipid Complexes

Incorporating cell-penetrating peptides (CPPs) strongly enhance endocytosis to allow the intracellular delivery of complex biomolecules, including nucleic acids and proteins. BOC Sciences' peptide-lipid complexes support the promotion of cell entry and, hence increase the possibility for therapies related to gene therapy and some chemotherapeutic treatments.

Temperature-Responsive and pH-Sensitive Lipids

Temperature-responsive and pH-sensitive lipids enable site-specific, on-demand release. BOC Sciences' formulations respond to local temperature (e.g., hyperthermia-triggered release) or acidic environments, such as tumor sites, enhancing targeted drug release and therapeutic efficacy.

The functionality of liposomes within drug delivery systems is assured by the choice and quality of raw materials. BOC Sciences provides a comprehensive portfolio of high-quality phospholipids, along with relevant stabilizers, cryoprotectants, and synthetic additives that enhance liposome formulation and stability with improved drug release. Accordingly, with continuous development in the materials that could be used in liposomes, new avenues are opened for therapeutic agents that are correctly targeted and delivered efficiently.