Liposome preparations are artificially made lipid vesicles consisting primarily of phospholipids and cholesterol. They are organised as bilayers with some consisting of a single bilayer and others, several. They may therefore be classified as unilamellar or multilamellar based on the number of bilayers. They measure on average about 400 nm in diameter.
One of the methods used in forming the vesicles is known as sonication. Here, the lipid suspension containing cholesterol and phospholipids is hydrated and made to swell so as to separate the various bilayers. As the bilayers separate, they form large lipid vesicles. These are later broken down into smaller units by use of an instrument known as a sonicator. The sonicator delivers high levels of energy to the large molecules and breaks them down within 5 to 10 minutes.
Another technique that may be used is known as extrusion. In this technique, the suspension is first subjected to cyclical freezing and thawing. The aim of this is to improve the homogeneity in the size of the final vesicles obtained. The other alternative is to pass the vesicles through a series of progressively decreasing pores. The large particles are gradually decreased in size and they become smaller and finer.
A number of factors are known to cause a variation in the size of vesicles. These include among others, the duration for which the vesicles are processed, the amount of energy applied, composition and proportion of the lipids and the the tuning of the sonicator. The vesicles have a lot of similarities with cell membranes due to the presence of phospholipids and cholesterol. Both have a hydrophobic and hydrophilic ends.
The uses of lipid vesicles continue to increase by the day. Clinically, they play a central role in the delivery of drugs to various targets. They are now widely preferred over viral vectors for a number of reasons. One of the greatest advantages that they have is the fact that they are not immunogenic and rarely cause allergic reactions. This has been a big problem with the viral vectors. Another significant strength is that they are easier to synthesise and put to use.
The available drug formulations are used in the treatment of a wide variety of disease processes. The drugs include cytarabine (an anticancer agent), liposomal amphotericin B, a highly potent antifungal agent, liposomal IRIV vaccine, morphine and doxorubicin among others. Many other drug formulations are in different phases of clinical trials.
Another major area of application is in the administration of nutrients. These may either be deficient in the diet or there may be difficulties in their absorption particularly due to a low bioavailability. One of the commonest nutrients that are delivered in this manner is vitamin C. Other uses of liposome encapsulation include the use in the delivery of pesticides, enzymes and in the fixation of dyes to textiles.
If the successes being seen in research involving liposome preparations is anything to go by, then the future is very bright as regards the use of these vesicles. The lack of serious side effects associated with their use is a very encouraging fact. There have been a few reports suggesting that there may be cellular toxicity particularly in prolonged or heavy uses but these are just isolated cases. Another cause for concern is the presence of inhibitors in serum which could potentially reduce the effectiveness.
One of the methods used in forming the vesicles is known as sonication. Here, the lipid suspension containing cholesterol and phospholipids is hydrated and made to swell so as to separate the various bilayers. As the bilayers separate, they form large lipid vesicles. These are later broken down into smaller units by use of an instrument known as a sonicator. The sonicator delivers high levels of energy to the large molecules and breaks them down within 5 to 10 minutes.
Another technique that may be used is known as extrusion. In this technique, the suspension is first subjected to cyclical freezing and thawing. The aim of this is to improve the homogeneity in the size of the final vesicles obtained. The other alternative is to pass the vesicles through a series of progressively decreasing pores. The large particles are gradually decreased in size and they become smaller and finer.
A number of factors are known to cause a variation in the size of vesicles. These include among others, the duration for which the vesicles are processed, the amount of energy applied, composition and proportion of the lipids and the the tuning of the sonicator. The vesicles have a lot of similarities with cell membranes due to the presence of phospholipids and cholesterol. Both have a hydrophobic and hydrophilic ends.
The uses of lipid vesicles continue to increase by the day. Clinically, they play a central role in the delivery of drugs to various targets. They are now widely preferred over viral vectors for a number of reasons. One of the greatest advantages that they have is the fact that they are not immunogenic and rarely cause allergic reactions. This has been a big problem with the viral vectors. Another significant strength is that they are easier to synthesise and put to use.
The available drug formulations are used in the treatment of a wide variety of disease processes. The drugs include cytarabine (an anticancer agent), liposomal amphotericin B, a highly potent antifungal agent, liposomal IRIV vaccine, morphine and doxorubicin among others. Many other drug formulations are in different phases of clinical trials.
Another major area of application is in the administration of nutrients. These may either be deficient in the diet or there may be difficulties in their absorption particularly due to a low bioavailability. One of the commonest nutrients that are delivered in this manner is vitamin C. Other uses of liposome encapsulation include the use in the delivery of pesticides, enzymes and in the fixation of dyes to textiles.
If the successes being seen in research involving liposome preparations is anything to go by, then the future is very bright as regards the use of these vesicles. The lack of serious side effects associated with their use is a very encouraging fact. There have been a few reports suggesting that there may be cellular toxicity particularly in prolonged or heavy uses but these are just isolated cases. Another cause for concern is the presence of inhibitors in serum which could potentially reduce the effectiveness.
About the Author:
You can visit the website www.clodrosome.com for more helpful information about The Benefits Of Using Liposome Preparations
No comments:
Post a Comment