Hydrogels

(To study Sphingolipids Click here)

It is also referred to as "Aquagel".

An extremely hydrated polymer gel i.e. colloidal gel giving a jelly like appearance. The polymer chain holds many times its weight in trapped water [1] which can be upto 99%. Hydrogel has water as the dispersion medium or continuous phase.

(N. A. Peppas et al.) Hydrogels resemble, to a large extent, a biological tissue as they are hydrophilic and have the ability to imbibe large amounts of water and other biological fluids. They have a three dimensional macromolecular network. They are insoluble due to chemical and/or physical crosslinking as entaglements and crystallites. The crosslinks are formed by covalent bonds.
Components of hydrogel:
Hydrogel is made by the combination of a hydrophilic component and water i.e.

Hydrogel = Hydrophilic component +  Water

Types:
Hydrogels are
1. natural (Methylcelloluse and agarose)
2. synthetic (Polyacrylamide and polymetha-acrylamide)

(E. Tichy et al.) Two different types of hydrogels:

1. One based on Carbomer.

2. Second based on Polyacrylamide.

Two factors responsible for the extent of swelling and for retaining the water content are as follows:

1. The hydrophilicity of the polymer chain.

2. The crosslinking density. [2]

Properties of Hydrogels:
(Stephen D. Bruck) Properties that can be used to differentiate the hydrogels are

1. Permeability and diffusion co-effecients

2. Some role of quasiorganized water within the hydrogels.

3. Porosity.

4. Presence of functional groups.

5. Types and number of crosslinks.

6. Chemical entities.

Uses:
Hydrogels are very absorbent in nature.
They are also used in sustained release drug delivery systems.

References:
[1]http://www.nature.com/nrmicro/journal/v2/n2/glossary/nrmicro821_glossary.html

[2] 7.2, Engineering Materials For Biomedical Applications (Biomaterials Engineering and Processing Series) by Teoh Swee Hin

E. Tichy, Z. Vitkova, B. Cupkova, Effect of beta-(1,3)-glucan on rheological properties and stability of topical formulations. Die Pharmazie, 2006 Dec;61(12): Pages 1050-1.

N. A. Peppas, P. Bures, W. Leobandung and H. Ichikawa, Hydrogels in pharmaceutical formulations. European Journal of Pharmaceutics and Biopharmaceutics , Volume 50, Issue 1, 3 July 2000, Pages 27-46

Stephen D. Bruck, Aspects of three types of hydrogels for biomedical applications. Journal of Biomedical Materials Research(Volumes 1-23), Volume 7 Issue 5, Pages 387 - 404

Further Reading:
Biodegradable Hydrogels for Drug Delivery by Haesun Park, Kinam Park and Waleed S. W. Shalaby

Hydrogels and Biodegradable Polymers for Bioapplications (Acs Symposium Series, 627) by Raphael M. Ottenbrite, Samuel J. Huang and Kinam Park

Copyright (c), 2008, jeepakistan.blogspot.com

Medicine

A substance used to cure a disease or any other disturbance in the body.

Pharmaceutics

The art and science of preparing and dispensing drugs and medicines as well as developing the suitable dosage form of the medicine to be used by the patient.

Branches of Pharmaceutics:
1. Biopharmaceutics
2. Physical Pharmacy
3. Pharmaceutical Chemistry
4. Pharmacogenomics
5. Pharmaceutical Technology
6. Pharmaceutical formulation
7. Radiopharmaceutics

Types of Pharmacy:
1. Hospital Pharmacy
2. Industrial Pharmacy
3. Retail Pharmacy
4. Community Pharmacy
5. Clinical Pharmacy
6. Veterinary Pharmacy
7. Internet Pharmacy
8. Compounding Pharmacy

5-fluorouracil

Mechanism of action:

5-FU is a cytostatic drug that causes the inhibition of the formation of DNA through the inhibition of Thymidylate synthesis. [1]

Uses of 5-Fluorouracil (5-FU):

It is used as an anti-cancer agent and anti-scarring agent. [1]

References:

[1] New concept in glaucoma treatment by Faezah Sarfarazi. United States Patent, 5304561.

Further Reading:

Copyright (c), 2008, jeepakistan.blogspot.com

Vesicles

Introduction:
Small packets or bubbles that are used for the transport of materials within a cell and across the cell membrane.

Classification of Vesicles:
We can classify the vesicles on the following factors:
1. Structure
2. Liposomal preparation
1. Classification on the basis of structure
There are following types of vesicles on the basis of structure:

a. Small unilamellar vesicles; abbreviated as SUV. Size ranges from 20-100 nanometer.
b. Medium sized unilamellar vesicles; abbreviated as MUV.
c. Large unilamellar vesicles; abbreviated as LUV. Size is greater than 100 nanometer.
d. Oligolamellar vesicles; abbreviated as OLV. Size ranges from 0.1-1 micrometer.
e. Multilamellar large vesicles; abbreviated as MLV. Size is greater than 0.5 micrometer.
f. Giant unilamellar vesicles; abbreviated as GUV. Size is greater than 1 micrometer.
g. Unilamellar vesicles; abbreviated as UV. All size range.
h. Multivesicular vesicles; abbreviated as MVV. Size is large, usually greater than 1 micrometer.

2. Classification on the basis of liposomal preparations

There are following types of vesicles on the basis of liposomal preparations:
 a. Vesicles made by reverse phase evaporation method:
      i. Oligolamellar vesicles (also known as single vesicles); abbreviated as REV
      ii. Multilamellar vesicles ; abbreviated as MLV-REV
 b. Stable plurilamellar vesicles; SPLV
 c. Vesicles prepared by extrusion methods; abbreviated as VET
 d. Frozen and thawed multilamellar vesicles; abbreviated as FATMLV

 e. Dehydration-rehydration vesicles; abbreviated as DRV

Lamella

A thin layer of tissue.

Unilamellar

Having a single layer of lamella.