INTRODUCTION:

Cryptosomes are being developed as drug delivery systems to improve therapeutic activity and lessen side effects of several new medications. Liposomes distribute drugs via lipids. Over the last three years, various liposomes have been studied to deliver medication to humans and animals. Drug use, development, and discovery have increased due to this method. Lipid-based drug delivery systems (LDDS) consist of several formulations that possess diverse structural and functional characteristics, which are determined by the lipid and other constituents used. LDDS has transitioned from a microscale to a nanoscale by enhancing its effectiveness and use in therapy. LDDS comes in vesicular, solid lipid tablet, emulsion-based, and particle dose forms.

Cryptosomes are vesicular drug delivery mechanisms¹. Vesicles have been the preferred medication delivery mechanism in recent years. Lipid vesicles are useful in diagnostics, immunology, membrane biology, and genetic engineering.²

The vesicular system plays a crucial role in neurodegenerative diseases (NDD), namely in the sorting of diseased cells, genes, genetic materials, as well as in diagnostics and ensuring safe, efficient, and targeted drug delivery in living organisms. They function as a sustained-release mechanism, reducing the amount of medication that is rapidly metabolised. Over the last several decades, they have been extensively used as vehicles for delivering medication. The Greek terms Soma (body or bearer) and Crypto (hidden) are the origin of the phrase "cryptosome. (Figure 1) These lipid vesicles are less readily absorbed by phagocytes because they stay in the circulation for a considerable amount of time after being given systemically. The surfaces are covered with polyoxyethylene and phosphatidylcholine, both of which are derived from phosphatidylethanolamine. Cryptosomes, namely DSPE-PEG, consist of distearoylphosphatidylcholine and phospholipids like distearoylphosphatidylethanolamine-polyethylene glycol. Immuno-liposomes, another name for cryptosomes, are a particular kind of cryptosome with the ability to evade immune system recognition. The way that polyethylene glycol (PEG) and lipid are connected may have an impact on the characteristics of cryptosomes. The stiffness and surface hydrophilicity of the phospholipid bilayer are critical for the extended life of cryptosomes, which effectively maintains their presence in the circulation. Another crucial determinant controlling the duration of Cryptosomes circulation inside a living organism is the inhibition of macromolecule attachment to the outer layer of these vesicles. The presence of mobile steric repulsion on the lipid surface might hinder the process of adsorption.^3-4.

Figure 1: Figure of Cryptosomes.

Composition of cryptosomes:

Cryptosomes are liposomal mixtures made up of poloxamer molecules (polymers) and liposomes, which have one or more transport agents inside them. Poloxamer is sometimes called pluronics. The poloxamers that are used most often are polyoxyethylene (POE), polypropylene oxide (PPO), and co-polymers of POE with three different molecular masses. (Figure 2). Two water-soluble polyoxyethylene (POE) groups connect the Polypropyleneoxide groups that don't dissolve in water. Polymers with hydrophobic POE groups on both sides of the PPO units may cause steric friction, which protects the surface of the lipid bilayer. Because of this, they can be used to stabilise and emulsify.⁵

Figure 2. Types of poloxamers.

Figure 3: Types of phospholipid.

Cholesterol:

Vesicles include cholesterol, which is a crucial component. The addition of cholesterol significantly enhances the stability of the vesicle. The composition of cholesterol affects the entrapment of drugs in vesicles. As cholesterol levels rise, the capacity of vesicles to capture and retain medications also increases. The addition of cholesterol increases choline head group distance impairs electrostatic and hydrogen bonding interactions.⁶A high cholesterol level, the entrapment efficiency is significantly reduced. The bilayer is disrupted when a certain amount of cholesterol is introduced, resulting in a decrease in drug entrapment⁷.

Lipid core:

The composition of this substance consists mostly of lipids. Compounds that happen naturally include fat, wax, sterols, and vitamins A, D, E, and K that dissolve in fat. Lipids are used in detection, immunity, and cell biology. The lipid core might be composed of one or many lipids. The hydrophilic-lipophilic balance (HLB), melting point, and composition of fatty acids are characteristics of lipids that contribute to their ability to withstand water. In order to extend the lifespan of pharmaceuticals, Lipids having a higher melting point and a lower hydrophilic-lipophilic balance (HLB) are used.Higher HLB lipids enhance the rapid release and improved bioavailability of drugs.⁸

Negatively charged particles:

Phosphatidylinositol is a phospholipid that has a negative charge. Negatively charged particles hinder particle aggregation, coalescence, flocculation, and fusion⁹.

Phosphatidylcholine:

Phosphatidylcholine is the main ingredient of lecithin. Phosphatidylcholine (PC) is the most commonly utilised phospholipid¹⁰. It is not very soluble in water. Depending on temperature and moisture, phospholipids in water may form lamellar structures, micelles, or bilayer sheets. This specific Amphipathic surfactant. Soy and egg yolk membranes contain it. Soy lecithin and egg lecithin are two different types of lecithin based on their origins. The amount of drug entrapment in the vesicle rises significantly with the addition of lecithin.¹¹.

Surfactants:

The selection of surfactants is done on the basis of certain characteristics, especially the hydrophilic-lipophilic balance (HLB). It evaluates surfactant vesicle formation. Venicle formation is aided by 4–8 HLBs. Surfactant temperature affects medication vesicle containment. In the intervals when the phase transition temperature is highest, drug entrapment is most noticeable. The medication escapes the lipid vesicle due to high phase transition temperature and low permeability. Because of their high hydrophilic-lipophilic balance (HLB) scores, Span-40 and Span-60 have lower surface free energy. As a consequence, bigger vesicles exposed to the dissolving liquid on a wider surface area form¹². ECO-40, sometimes referred to as ethoxylated castor oil, has a maximum of 40 ethylene oxide (EO) units. Eight to forty EO groups are linked to the triglyceride side chain hydroxyl group in hydrogenated ethoxylated castor oil (HECO). HECO and ECO-40 are regarded as very potent surfactants.^13,14

Formulation:

Cryptosomes include liposomes and poloxamer.To stop the liposomes from sticking to the cells, some of the poloxamer molecules are injected onto the surface of the liposome in the form of micelles above the critical micellar temperature. Lower than the critical micellar temperature, poloxamer molecules decompose into monomers, influencing the liposome's ability to attach to adjacent cells and allowing it to cling to surrounding cells. To release pharmaceuticals selectively, they must be incorporated into monomers; moreover, liposomes must be retained in the target location or very near it by freezing. There are many ways to make liposomes (Figure 4). Standard processes such as extrusion and sonication may be used to create lipid vesicles. They may also be produced via detergent dialysis, freeze-thawing, and reverse-phase evaporation. Cryptosomes are made by adding poloxamer molecules to liposomes at various stages.¹¹

It is treated with molecules of poloxamer before the liposomes are inserted. The main ingredients utilised to make liposomes stealthy are polyethylene glycol and poloxamer or polymer. Consequently, cryptosomes are produced. PEGs between 1000 and 5000 molecular weight circulate lengthy and harder to digest by MPS. The plasma membrane's structural component, phosphatidylcholine, is the most often utilised phospholipid in formulations. It contains lipophilic phosphatidyl and hydrophilic choline moieties and polyphenolics.¹⁵.

Figure 4: Preparation method.

METHODS OF PREPARATION:

Method for removing detergents:

Adding detergent to phospholipid creates micellar. Adsorption or column chromatography separates the detergent from the mix or combination. The concentration of phospholipids in the micelle rises, causing the lipids to come closer together and create a vesicle with a single bilayer¹⁶. Measure the absorption of detergent by agitating a solution containing a mixture of organic compounds using polystyrene absorbers like XAD-2 Mani and Bio-Modes SM2. One major benefit of using detergent absorbers is their ability to effectively eliminate low CMC detergents that are not fully reduced.This approach is also used in the manufacture of liposomes.¹⁷

Phase-reversal evaporation:

There are two separate steps to the procedure. Water in oil is combined with the phospholipid and buffer to create an emulsion. The organic layer is next extracted and separated at lower pressure. Sonication or other mechanical techniques are used to disperse the phospholipid layer and the water, resulting in emulsification. As the phospholipid-coated water droplets approach each other, the organic layer is removed using a vacuum, resulting in a gel-like matrix.When subjected to a vacuum, the organic phase further decreases in volume, leading to the formation of a uniform paste. The LUVs in this mixture are held in suspension. This approach can provide a medication integration efficiency of 60-65 percent. Therefore, it may be used to connect both diminutive and substantial molecules¹⁸. By using this method, a viscousniosome dispersion may be thinned with PBS and heated on a water bath at 60°C for 10 minutes to yield niosomes.¹⁹

Sonication method:

Cholesterol, lipids, and phosphatidylcholine were mixed in chloroform using 3–4 drops of methanol in a round-bottomed flask, using different molar ratios.After carefully measuring the appropriate amount of the drug, it was incorporated into the concoction.The organic layer was then evaporated to complete dryness using a rotary evaporator at reduced pressure. Consequently, a lipid coating developed around sides of the round bottom containers.²⁰

Cryptosomal drug release:

Cell membranes and other bilayer membranes are combined with the phospholipid bilayer of cryptosomes to release the contents of the liposomes. Two strategies for accomplishing this task endocytosis and cell-surface adsorption. Endocytosis involves the bilayer of lipids combining with the cell membrane to expel things. The movement of liposomal contents occurs due to their attachment to the surface of the cell.

Cryptosome uses and applications:

· Cryptosomes has the capability to transport biologically active substances.

· Ciprofloxacin therapy for pneumonia caused by Klebsiellapneumoniae may be improved by employing liposomes that have a sustained-release property and are coated with polyethylene glycols (PEG), which allows them to circulate in the body for a longer period of time.

· Doxil, a liposomal doxorubicin formulation with polyethylene glycols, was tested in mouse tumours, demonstrates superior therapeutic efficiency, longer circulation duration, and increased accumulation time compared to free (unencapsulated) doxorubicin (DOX). Enhanced drug accumulation is linked to increased liposome durability in malignant effusions.

· It has the capacity to be used for medication administration, tumourvisualisation, and treatment.^.[21]

· It has improved the administration of drugs in solid tumours and breast cancer.

· A drug delivery strategy that uses cryptosomes is based on ligand-gated mechanisms ²².

CONCLUSION:

Enhancing dose formulations in order to enhance the duration of their effects or their half-life is one of scientists' biggest challenges. Cryptosomes are among the most effective medication delivery mechanisms through the vesicles due to their high level of stability, long circulation, extended half-life, and decreased identification and absorption through the macrophages²³. After systemic distribution, this liposomal vesicle, adorned with a surface coating, remains in circulation for a significant duration. Due to this method, there has been a significant increase in drug usage, development, and discovery^.24 A variety of novel medication delivery through vesicles methods utilizing a phospholipid bilayer and lipid core have attracted interest as a result of them. Vesicular systems, which employ vesicles, are often used as transporters or additives in many applications. It may serve as a vehicle for physiologically active chemicals. Research has shown its advantageous effects in the field of tumor imaging and treatment. In the future, particles with cryptosome-like attributes will synergize with other technologies to significantly contribute to the sophisticated transportation of pharmaceuticals for diagnostic purposes and precise administration of treatment.^.[25].The clinical acceptability of increased medication delivery to disease areas, achieved by the capacity to prolong circulation residence durations, is now being realized. ²⁶

FUTURE PERSPECTIVE:

The lipid vesicles have a surface coat made up of phosphatidylcholine (pc) and a polyoxoyethylene derivative of phosphatidylethanolamine that is appropriate for the purpose. Possessing the ability to use ligands for the purpose of directing drugs to specific targets.²⁷

CONFLICT OF INTEREST:

The author says there are no competing interests.

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Received on 21.07.2023 Modified on 07.03.2024

Research J. Pharm. and Tech 2024; 17(11):5666-5670

DOI: 10.52711/0974-360X.2024.00863