Liposome preparations consist of artificial spherical vesicles whose main chemical components are phospholipids and cholesterol organised in two layers. The process of forming this bilayer is known as sonication. Based on the structure, the vesicles may be classified as either multilammellar or unilamellar. The former have several bilayers while the latter has just a single bilayer. Most vesicles measure less than 400nm in diameter.
The phospholipids and the cholesterol are first put into a suspension. They are hydrated to make them swell and separate into various bilayers. They self-close to form large vesicles that have to be modified by some techniques. One of these techniques is known as sonication. Here, an instrument known as a sonicator is used to provide high energy that is used to break down the large vesicles into smaller ones. This is achieved within five to ten minutes.
Apart from sonication, the other method that can be used for formation of lipid vesicles is known as extrusion. In this method, phospholipid and cholesterol suspensions undergo a continuous process of freezing and thawing so as to improve the homogeneity of size of final vesicles. Alternatively, the suspension may be passed through a filter of large pore sizes before subsequently being passed through one with smaller pores so as to yield finer particles.
The sizes of the vesicles will slightly depending on among other factors, duration of the process, energy used, the composition of the suspension used and the tuning of the sonicator. Regardless of the size, the vesicles have been found to bear very close resemblance to the cell membranes in structure. Both cell membranes and lipid vesicles have phospholipid heads that are hydrophilic and fatty acid tails that are hydrophobic. Their physical properties are like those of surfactants.
Lipid vesicles have gained wide clinical usage in recent times. They now play a very important role in drug delivery systems and are rapidly replacing viral vectors. This is due to the various advantages that they have over the viral systems. One of these advantages is that they are rarely immunogenic and hence are unlikely to cause immunological reactions which are fairly common with viral vectors. Another major advantage is the fact that they can be synthesized more easily than the vectors.
Many drugs that utilize lipid vesicles are in use today. These include, among others, liposomal amphotericin B, a potent antifungal agent, liposomal cytarabine (a drug used for treatment of malignant meningitis and other cancers), liposomal IRIV vaccine (used for hepatitis A and influenza), doxorubicin and morphine. There are many more others that are the subject of research.
Another common application of the vesicles is in the delivery of various nutrients. Many of these nutrients are either deficient in the diet or are difficult to absorb because of a low bioavailability. Vitamin C is frequently administered through lipid encapsulation. Pesticides are applied to plants using the same principle. Other areas of liposome encapsulation application include delivery of enzymes and the fixing of dyes to textiles.
There are many other uses of liposome preparations. Most of these are still the subject of research that is aimed at increasing their efficiency. The most encouraging news is that, no serious side effects related to the use of these preparations have been reported. There are some concerns, however, that they have a potential to cause cellular toxicity especially when taken in large quantities. The presence of inhibitors in serum may be another downside since these may inhibit the potency of the vesicles.
The phospholipids and the cholesterol are first put into a suspension. They are hydrated to make them swell and separate into various bilayers. They self-close to form large vesicles that have to be modified by some techniques. One of these techniques is known as sonication. Here, an instrument known as a sonicator is used to provide high energy that is used to break down the large vesicles into smaller ones. This is achieved within five to ten minutes.
Apart from sonication, the other method that can be used for formation of lipid vesicles is known as extrusion. In this method, phospholipid and cholesterol suspensions undergo a continuous process of freezing and thawing so as to improve the homogeneity of size of final vesicles. Alternatively, the suspension may be passed through a filter of large pore sizes before subsequently being passed through one with smaller pores so as to yield finer particles.
The sizes of the vesicles will slightly depending on among other factors, duration of the process, energy used, the composition of the suspension used and the tuning of the sonicator. Regardless of the size, the vesicles have been found to bear very close resemblance to the cell membranes in structure. Both cell membranes and lipid vesicles have phospholipid heads that are hydrophilic and fatty acid tails that are hydrophobic. Their physical properties are like those of surfactants.
Lipid vesicles have gained wide clinical usage in recent times. They now play a very important role in drug delivery systems and are rapidly replacing viral vectors. This is due to the various advantages that they have over the viral systems. One of these advantages is that they are rarely immunogenic and hence are unlikely to cause immunological reactions which are fairly common with viral vectors. Another major advantage is the fact that they can be synthesized more easily than the vectors.
Many drugs that utilize lipid vesicles are in use today. These include, among others, liposomal amphotericin B, a potent antifungal agent, liposomal cytarabine (a drug used for treatment of malignant meningitis and other cancers), liposomal IRIV vaccine (used for hepatitis A and influenza), doxorubicin and morphine. There are many more others that are the subject of research.
Another common application of the vesicles is in the delivery of various nutrients. Many of these nutrients are either deficient in the diet or are difficult to absorb because of a low bioavailability. Vitamin C is frequently administered through lipid encapsulation. Pesticides are applied to plants using the same principle. Other areas of liposome encapsulation application include delivery of enzymes and the fixing of dyes to textiles.
There are many other uses of liposome preparations. Most of these are still the subject of research that is aimed at increasing their efficiency. The most encouraging news is that, no serious side effects related to the use of these preparations have been reported. There are some concerns, however, that they have a potential to cause cellular toxicity especially when taken in large quantities. The presence of inhibitors in serum may be another downside since these may inhibit the potency of the vesicles.
About the Author:
When you want to see details regarding liposome, you can click on the links at www.clodrosome.com today. More information is available at http://www.clodrosome.com now.
No comments:
Post a Comment