Sphingosomes and sphingolipids

Sphingosomes are similar in structure to liposomes but in sphingosomes, lipids namely sphingolipids are responsible for making up the bilayer of sphingosomes.

Figure: Sphingolipids

(Murray S. Webb et al.) The formulations have enhanced stability and thus are used in methods for improved drug delivery and effective treatment.

Sphingolipids:
They belong to a class of lipids i.e. Membrane lipids. Sphingolipids come from the combination of sphingosine (a long chain base), which is an amino alcohol (and aliphatic in nature), and fatty acid.It is the simplest sphingolipid and is also referred to as sphingoid base. They have a head, which is polar in nature, and two tails, which are nonpolar.

The following mnemonic will help you a lot in remembering the structure of shingosine.

Sphingolipids are present in plasma membranes.

Types of sphingolipids:

1. Ceramide:
It consists of Fatty acid chain and sphingosine linked through amide linkage. It is ordinarily present in all sphingolipids.

These are the precursors of glycolipids and phospholipids having a wide range of function in the tissues.

2. Sphingophosphlipids
    a. Sphingomyelin
    It consists of Phosphoethanolamine or phosphocholine and 1-hydroxy group of a ceramide linked through ester linkage.Sphingomyelin is structurally similar to phosphatidylcholine but biologically and physically it is different.

3. Glycosphingolipids:
     a. Cerebrosides
     b. Sulfatides (Sulfated cerebrosides)
     c. Globosides
     d. Gangliosides

Synthesis of sphingolipids:
Synthesis of sphingolipids takes place in Endoplasmic reticulum. Following is the pathway for the synthesis of sphingolipids.

In the first step, Palmitoyl-CoA alongwith serine results into beta ketosphinganine to sphinganine to N-acylsphinganine to Ceramide containing sphingosine to Cerebroside and sphingomyelin.

Sphingomyelin cycle:
Sphingomyelin cycle is used to show a relationship between the metabolic products of sphingolipids.

Free sphingosine and certain other long chain bases work as mediators for many of the cellular processes. Sphingosine 1-phosphate and ceramide 1-phosphate increases mitosis.

Degradation of sphingolipids:
These are degraded by lysosomal enzymes.

Presence of sphingolipids in Micro-organisms:
Sphingolipids are also found in some genera of bacteria like sphingomonas and sphingobacterium.

Uses of sphingolipids:
They work as the site of adhesion of extracellular proteins. Sphingolipids are important in cell recognition and signal transmission/transduction.
Sphingolipids form the myelin sheath around the nerves in central nervous system.

Diseases in which sphingolipids are involved:
1. Microbial infections
2. Diabetes
3. Alzheimer's disease
4. Certain cancers
5. Some diseases of the respiratory and cardiovascular systems and
6. Some of the neurological syndromes

References:
Murray S. Webb, Marcel B. Bally, Lawrence D. Mayer, James J. Miller, Paul G. Tardi, Sphingosomes for enhanced drug delivery. Patent number: 5814335.

Further Reading:
Delivery System Handbook for Personal Care and Cosmetic Products : Technology, Applications and Formulations (Breakthroughs in Personal Care and Cosmetic Technology) by Meyer R. Rosen

Encyclopedia of Pharmaceutical Technology by James Swarbrick

Hannun, Y. A. 1994. The sphingomyelin cycle and the second messenger function of ceramide. Journal of Biological Chemistry, Vol. 269, No. 5.

http://lipidlibrary.aocs.org/lipids/introsph/index.htm

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Industrial Pharmacy

Industrial is the part of Pharmacy in relation to the manufacturing and Quality control of Pharmaceutical products which include a diverse range of items. It is different from Hospital Pharmacy in that Hospital Pharmacist is in direct contact with patient. he has to examine the patient medication history and is well aware of pharmacology. On the other hand, Industrial pharmacist is well aware of how a product is to be prepared. He has good knowledge of pharmaceutics.

Further Reading:
The Theory and Practice of Industrial Pharmacy by Leon Lachman, Joseph L. Kanig and Herbert A. Lieberman

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Retail Pharmacy

Retail Pharmacy is the place where there is the sale of Medicines (health related products and in some cases other items of daily use) directly to the customers (consumers).

Further Reading:
Marketing and retail Pharmacy by Colin Gilligan, Robin Lowe and Peter Cattee

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Hospital Pharmacy

Hospital Pharmacy concerns with dealing of in-patient and out-patient pharmacists in a hospital setting.

References:


Further Reading:
Hospital Pharmacy

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Micro-encapsulation

Physical Methods of Encapsulation
1. Spray drying
2. Spray chilling
3. Rotary disk atomization
4. Fluid bed coating
5. Stationary nozzle coextrusion
6. Centrifugal head coextrusion
7. Submerged nozzle coextrusion
8. Pan coating
9. Air Suspension coating
10. Vibrational nozzle

Chemical Methods of Encapsulation
1. Phase separation
2. Solvent evaporation
3. Solvent extraction
4. Interfacial polymerization
5. Simple and complex coacervation
6. In-situ polymerization:
"In situ" means "in place". This is sometimes referred to as in between "in-vivo" and "in-vitro". In-situ polymerization is used to disperse nanocomposites or nanoparticles properly into monomer or monomer solution and the resulting mixture is polymerized. [1]
Examples of nanocomposites prepared by in-situ polymerization:
(Feng Yang et al.)Polyamide 6/silica nanocomposites
(Changchun Zeng et al.) Poly(methyl methacrylate) and Polystyrene/Clay Nanocomposites

7. Liposome technology
8. Nanoencapsulation
9. Matrix polymerization

References:
[1] Page 112, Nanocomposite science and technology by Pulickel M. Ajayan, Linda S. Schadler, Paul V. Braun. 2006.

Changchun Zeng and L. James Lee, Poly(methyl methacrylate) and Polystyrene/Clay Nanocomposites Prepared by in-Situ Polymerization. Macromolecules, 2001, 34 (12), Pages 4098 -4103.

Feng Yang, Yuchun Ou, Zhongzhen Yu. Polyamide 6/silica nanocomposites prepared by in situ polymerization. Journal of Applied Polymer Science, Volume 69 Issue 2, Pages 355 - 361

Further Reading:
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In vitro and in vivo correlation

The word "correlation" is used for the relationship between two variables. The strength of the relationship (linear) between the variables is given by "r".

(D. Brockmeier et al.)Change in pH, formulation agitation, Motility and Absorption rate constant of gastrointestinal tract are helpful in determining the in vitro in vivo biphasic linear correlation.
(K. Ishii et al.)Novel approaches by the use of Mathematical deconvolution method (Deconvolution is an algorithm based process for the reversal of effects of convolution. It is used for the techniques of signal processing and image processing. It uses fourier transform mathematics to restore a blurred image to an unblurred state as much as possible. It is used in optimization techniques by the researchers.) have been used for the study of in vitro and in vivo correlation studies. It has been found that kappa d shows better correlation between in vitro and in vivo data for ibuprofen capsules as compared to dissolution time at 50 % (t50%).

Reza A. Fassihi et al. found that triple layer model shows good correlation between in vitro and in vivo results.

H. Lennernäs et al. in their studies found that passivley or rapidly transported drugs show comparable permeability co-efficients in vitro (in Caco-2 monolayers) and in vivo (in human jejunum) whereas actively transported drugs show slow carrier mediated transport rates in vitro than in vivo.

References:
D. Brockmeier, H.J. Dengler, D. Voegele. In vitro--in vivo correlation of dissolution, a time scaling problem? Transformation of in vitro results to the in vivo situation, using theophylline as a practical example. European Journal of Clinical Pharmacology 1985;28(3), Pages 291-300.

H. Lennernäs, , K. Palm, U. Fagerholm and P. Artursson, Comparison between active and passive drug transport in human intestinal epithelial (caco-2) cells in vitro and human jejunum in vivo. International Journal of Pharmaceutics, Volume 127, Issue 1, 15 January 1996, Pages 103-107.

K. Ishii, Y. Saitou, R. Yamada, S. Itai, M. Nemoto. Novel approach for determination of correlation between in vivo and in vitro dissolution using the optimization technique. Chemical and Pharmaceutical bulletin (Tokyo). 1996 Aug;44(8):1550-5.

Reza A. Fassihi, Wolfgang A. Ritschel, Multiple-layer, direct-compression, controlled-release system: In vitro and in vivo evaluation.
Journal of Pharmaceutical Sciences, 2006, Volume 82 Issue 7, Pages 750 - 754.

Further Reading:
Pharmaceutical Principles of Solid Dosage Forms by Jens T. Carstensen

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Surfactants

Surfactants are the substances which allow the mixing of oil with water. They allow to reduce interfacial tecnsion.

There are four different types of surfactants:

1. Amphoteric Surfactants.
2. Cationic Surfactants.
3. Anionic Surfactants.
4. Non-ionic Surfactants.

References:


Further Reading:
Applied Surfactants: Principles and Applications by Tharwat F. Tadros

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