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.
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 popularly used technique is known as extrusion. In this technique, the suspension is subjected to a cyclical process of freezing and thawing that eventually results in the breakdown of the large vesicles. Homogenous of size is achieved after a few cycles. Another variant of the same is the passage of the vesicles through progressively decreasing pores until very fine particles are obtained.
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 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.
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 popularly used technique is known as extrusion. In this technique, the suspension is subjected to a cyclical process of freezing and thawing that eventually results in the breakdown of the large vesicles. Homogenous of size is achieved after a few cycles. Another variant of the same is the passage of the vesicles through progressively decreasing pores until very fine particles are obtained.
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 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.
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.
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