Nanoparticles An Overview

Nanoparticles are sub-nano-sized colloidal structures composed of synthetic or semi-synthetic polymers.

Its size ranges from 1-100nm.

One can distinguish two types  of nanoparticles
1.Nanospheres

2.Nanocapsule

Nanospheres - matrix systems.

Nanocapsules - which are reservoir systems composed of a polymer membrane surrounding an oily or aqueous core.

Advantages of Nanoparticles:

·         More uniform effect of the drug

·         Reduction in the frequency of the dosages

·         Site specific targeting

·         Various routes of administration

·         Better drug utilization and less side effects

Disadvantages of Nanoparticles:

•       High cost

•       Productivity more difficult

•       Reduced ability to adjust the dose

•       Highly sophisticated technology

•       Requires skills to manufacture

•       Difficult to maintain stability of dosage form.

Polymers used in preparation of nanoparticles:

NATURAL HYDROPHILIC

Eg: proteins

       Polysaccharides

SYNTHETIC HYDROPHOBIC

Eg: polyesters          

       Polystyrene

Methods of preparation

A:  Amphiphilic  Macromolecules Cross Linking

1) Heat crosslinking.

2) Chemical crosslinking.

B: Polymerization  Methods 

1) Emulsion polymerization

2) Dispersion polymerization

3) Interfacial condensation polymerization

4) Interfacial complexation

C : Polymer precipitation methods

1) Solvent evaporation method

2) Solvent displacement

3) Salting out

A : Molecular crosslinking in emulsion

B : Polymerization Methods:

Emulsion polymerization :

It consists of

a) Micellar nucleation and polymerization :

     Monomer is insoluble in continuous phase.(O/W phase)

     Aqueous phase

b)Homogenous nucleation and polymerization :

     Monomer is soluble in continuous phase.(W/O phase)  

      Organic phase.

Dispersion polymerization:

Interfacial polymer condensation:

C : Polymer Precipitation Methods:

The polymer precipitation occurs as a consequence of solvent evaporation which can be brought about by increasing solubility of organic solvent in external medium by adding alcohol (Eg. Isopropanolol)

  They are 3 types

1. Solvent evaporation method
2. Solvent displacement
3. Salting out

1.       Solvent Evaporation Method

   2. Solvent Displacement Method

3. Salting out of Polymer:

                                                                             

Evaluation of nanoparticles

1.         Paricle size :

·           Photon correlation spectroscopy(PCS) : For smaller particle.

·           Laser diffractometric : For larger particle.

·           Electron microscopy (EM) : Required coating of conductive material such as gold & limited to dry sample.

·           Transmission electron microscopy (TEM) : Easier method & Permits differntiation among nanocapsule & nanoparticle .

·           Atomic force microscope

·           Laser force microscope

·           Scanning electron microscope

2.Density :

  Helium or air using a gas pycnometer

  Density gradiant centrifugation

3. Molecular weight :

    Gel permeation chromatography using refractive index detector.

 4. Structure & Crystallinity :

    X-ray diffraction Thermoanalytical method such as,

         1) Differential scanning calorimetry

         2) Differential thermal analysis

         3) Thermogravimetry

5. Surface charge:

    Surface charge of particle can be determined by measuring particle velocity in electrical field.

6. Invitro release :

   Diffusion cell

   Recently introduced modified Ultra-filtration tech.

   Media used : phosphate buffer

7. Nanoparticle yield  

% yield=          (Actual weight of product)

                      ______________________                  X 100

                 (Total weight of excipient and Drug)