Liposomal Vitamin C Injection

Solvent injection method: Dissolve fat soluble raw materials in organic solvents. After the raw materials are completely dissolved, quickly inject the solution into an aqueous medium to form crude liposomes, and then remove the organic solvents contained therein.

Thin film hydration method: Phospholipids are dissolved in organic solvents, and the organic solvents are removed by vacuum evaporation to form a lipid film. Then, a suitable aqueous medium is added to hydrate and detach the lipid film at the phase transition temperature of phospholipids, and self-assembly is carried out to form liposomes.

Reverse evaporation method: Dissolve lipophilic raw materials in organic solvents, mix and emulsify them with drug containing aqueous solutions, and then remove the organic solvents through vacuum evaporation to form liposomes.

Double emulsion method: First, dissolve the fat soluble raw materials in an appropriate amount of organic solvent, add a small amount of aqueous solution in proportion, mix and emulsify the two through mechanical force to form a relatively stable W/O emulsion, then quickly add a large amount of aqueous solution, mix for secondary emulsification treatment to form W/O/W emulsion, and then remove residual organic solvent through physical means to obtain liposome suspension.

Microfluidic method: Lipids and water phases are transported to a microfluidic chip at a constant speed in a certain proportion for mixing and emulsification. Different flow channel structures in the chip enable the liquid to reach turbulent, laminar, or atomized states. Then, under the action of a high-pressure delivery pump, the liquid is reduced in particle size by impact and shear forces.

Adsorption: Liposomes with low fluidity can stably adsorb onto the surface of cultured cells near or below the phase transition temperature of the lipid bilayer. This process is almost temperature dependent and belongs to a common physical adsorption phenomenon, which is influenced by factors such as particle size, density, and surface charge of both.

Lipid exchange: Lipids in liposomes exchange with lipids on the cell membrane. The process involves adsorption between liposomes and cells, followed by specific exchange of polar top groups or non-specific exchange of acyl chains under the mediation of cell surface proteins. Exchange only occurs between the outer monolayer of the liposome bilayer and the outer monolayer of the cell membrane, while the contents of liposomes do not enter the cultured cells.

Endocytosis: Liposomes are easily engulfed by reticuloendothelial system cells, especially monocytes, as foreign substances, entering lysosomes, fusing, and rapidly digested and lysed by lysosomes to release drugs. After drug release, it acts in lysosomes or in vitro with lysosomes. Through endocytosis, liposomes can specifically concentrate drugs in the cell chamber they want to act on, and can also allow drugs that cannot pass through the plasma membrane to reach the lysosome.

Fusion: Liposomal membranes have similar components to cell membranes, and drugs can be loaded into cells through fusion and released through lysosomal digestion. In vitro experiments have shown that liposomes can deliver bioactive macromolecules into cultured cells through cell fusion.

Leakage: Leakage is an indicator of the stability of liposomes, which may be the result of the interaction between cell surface proteins and liposomes.

Diffusion: Liposome gel preparation is used for skin, and the lipid membrane becomes a controlled release membrane. The drug contained in it is released through diffusion, and enters the body subject to the transdermal absorption mechanism. Oral liposomes are mostly digested in the gastrointestinal tract, but they also release their contents through adsorption, diffusion, or fusion with the intestinal mucosa.

Phosphatase digestion: Liposome phospholipid membrane digestion is directly proportional to the content of phosphatase in the body. The level of phosphatase in tumor tissue is significantly higher than that in normal tissue, so liposomes are more likely to release drugs in tumor tissue.

Administration routes: including intravenous injection, intramuscular injection, subcutaneous injection, oral administration, intraocular administration, etc. For example, after intravenous injection, liposomes are preferentially taken up by tissues rich in reticuloendothelial cells such as the liver and spleen, and rapidly engulfed and degraded by mononuclear phagocytes, with small amounts taken up by the lungs, bone marrow, and kidneys.

Wide drug loading range: Liposoluble drugs can be located between bilayer lipid membranes, amphiphilic drugs can be located on phospholipids at the interface between the aqueous phase and the membrane, and hydrophilic drugs can be located in the aqueous phase.

There are various routes of administration: in addition to the most common injection route, liposomes are also suitable for oral administration, ocular administration, pulmonary inhalation administration, and transdermal administration.

Targeted: Ordinary liposomes have liver and spleen tissue targeting properties, and liposomes modified with monoclonal antibodies and other antibodies can have specific targeting properties.

Long acting: Long circulating liposomes can prolong the retention time of drugs in the blood, which is beneficial for increasing drug efficacy.

Good tissue compatibility: With a structure similar to biological membranes, liposomes have good cell affinity and tissue compatibility, and can adsorb around target cells for a long time. They can also directly enter cells and release drugs through lysosomal digestion.

Can reduce drug toxicity: After being encapsulated in liposomes, the cumulative amount of drugs in the heart and kidneys is much lower than that of free drugs. Therefore, drugs that are toxic to the heart and kidneys can be prepared into liposomes to achieve the effect of reducing drug toxicity.

Can improve drug stability: For some drugs that are unstable in specific environments, they can be protected by liposome bilayers to enhance the stability of certain drugs.

Low encapsulation efficiency and instability: Ordinary liposomes have problems such as low encapsulation efficiency, instability, and drug leakage during long-term storage.

The difficulty of industrial production is high: for the industrial production of liposomes, it involves many challenges such as particle size distribution, drug loading rate, encapsulation efficiency, sterility, stability, etc. Currently, there is a lack of mature experience in China and a complete technical system has not been formed. For example, the particle size and distribution of liposome formulations significantly affect their in vivo behavior, which requires the use of particle size control equipment in large-scale production and good reproducibility between batches.

High cost: The cost of excipients and equipment required for preparing liposomes is relatively high, so the cost of liposome formulations is higher than many formulations, resulting in higher prices for liposomes.