colloids part 1

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Colloids – Dispersed systems:

Colloids – Dispersed systems At the end of the class students will be able to understand. 1. Importance of colloids in pharmaceutical product development. 2. Definition, types of colloids, their differences and applications. 3. Preparation and Purification of colloids. 4. Properties of colloids: optical, electrical and kinetic. 5. Stabilization of colloids.


Colloids The dispersed-phase particles have a diameter of between approximately 1 and 1000 nanometers .  Such particles are normally invisible in an optical microscope, though their presence can be confirmed with the use of an  ultra microscope or an electro microscope. Eg: Homogeneous mixtures with a dispersed phase in this size range may be called  Colloidal aerosols ,  Colloidal emulsions ,  Colloidal foams , Colloidal dispersions , or  Hydrosols .

Examples of pharmaceutical colloids:

Examples of pharmaceutical colloids Silver colloid ( germicidal ) Iron- dextran injection (official and used in treatment of anemia administered intramuscularly) Iron-sorbitol injection (consists of citrate, sorbitol and dextran complexed to ferric ions) etc.

Dosage forms as colloids:

Dosage forms as colloids

Size of colloids. Electron Microscopic view:

Size of colloids. Electron Microscopic view colloidal gold

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Medium / Phases Dispersed phase Gas Liquid Solid Continuous medium Gas NONE (All gases are mutually miscible) Liquid aerosol Examples: fog,  mist, hair sprays Solid aerosol Examples: smoke,  cloud, air particulates Liquid Foam Example: whipped cream, Shaving cream Emulsion Examples: milk,  mayonnaise,  hand cream Sol Examples: pigmented ink, blood Solid Solid foam Examples: aerogel,  pumice Gel Examples: agar,  gelatin jelly  Solid sol Example: cranberry glass Examples of colloids

Characteristics of dispersed phase of colloidal system:

Characteristics of dispersed phase of colloidal system 1. Particle shape: The shapes of particles in dispersion depend on the method of preparation and affinity of particles to the dispersion medium. Shape of the colloids is spherical but oblate, ellipsoid, long rods and coiled threads, branched threads are also found some time.

Characteristics of dispersed phase of colloidal system:

Characteristics of dispersed phase of colloidal system 2. Surface area : As the size of colloidal particles is of the order of a few µm they have larger surface area. They show better solubility due to increased surface area. 3. Surface charges : Colloidal particles possess charges on their surface, when the size of the particle is small they tend to locate at surface. Example : Acacia and tragacanth- negative charged Gelatin and aluminum - positive charged.


COLLOID SHAPE A. Spheres & globules Short rods Oblate ellipsoids & flakes Long rods & threads Loosely coiled threads Branched threads

Characteristics of dispersed phase of colloidal system.:

Characteristics of dispersed phase of colloidal system. Due to the charges on the particles they move continuously in random motion and they colloid with each other, like charges on the particles create repulsion . Such repulsion keeps the particles as individual entities and distribute uniformly and stability is also improved . The colloids are classified as positive or negative colloids based on their particle charges. Collision of colloidal particles Aggregation of particle- attraction Individual particle- repulsion

Pharmaceutical applications of colloids:

Pharmaceutical applications of colloids 1. Therapy: Some colloidal dispersions show better therapeutic action and are used in treatment. Examples: Silver – germicidal - Colloidal silver has been approved as a disinfectant for hospitals and medical centers . Copper – anticancer: for the site specific delivery of anticancer drug which can reduce the side effects of the anti cancer drugs. Colloidal Copper is a great adjunct to health and beauty , a stimulant for the brain , an artery and blood cleanser and antioxidant as well as a collagen booster. Mercury – Antisyphilis

Pharmaceutical applications of colloids:

Pharmaceutical applications of colloids 2. Absorption : Colloidal sulfur shows better and faster absorption compared to a coarse dispersion of sulfur . 3. Solubility : Solubility of drugs is improved by using colloidal systems containing surface active agents. Eg: Solubilization of sulfonamides and Phenobarb ital. 4. Stability: Dispersions of surface active agents (association colloids) are used to improve the stability of drugs in liquid forms. Colloidal dispersions of molecules (gelatin) and synthetic Polymers ( methylcellulose) (HPMC) are applied as coating solutions on tablets and granules.

Pharmaceutical applications of colloids:

Pharmaceutical applications of colloids 5.Targeting of drugs to specific organs : Colloids are used in targeting the drugs to specific body organs. Eg: Carrier systems such as liposome, niosome, and nanoparticles. 6. Colloidal systems that are official and meant for Parenteral use : (a) Iron Dextran injection, B.P : Contains Dextran complexes with ferric ions (IM route) in the treatment of anemia. (b) Iron sorbitol injection, B.P : Contains sorbitol, Dextran and citric acid complexes with ferric ions.

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