Microcapsule:Microcapsule is a spherical particle with sizevarying from 50nm to 2mm, containing acore substance.
The microspheres are characteristically free flowing powders consisting of proteinsor synthetic polymers, which are biodegradable in nature, and ideally having aparticle size less than 200 micrometer. Polymers of both natural and syntheticorigin can be used.
• Synthetic non-biodegradable materials used arePMMA, Acrolein etc and biodegradablematerials used are Lactides and glycolides andtheir copolymers.• Proteins like albumins, gelatin andcarbohydrates like starch, glucose, chitosanetc are also used.
Prerequisites for Ideal Micro particulate carriers: o Longer duration of action o Increase of Therapeutic efficiency. o Biocompatibility o Sterilizability o Relative Stability o Water solubility or dispersability
Methods of Preparation Preparation methods Emulsion Polymerization techniques Single Double Normal and Emulsion Emulsion Interfacial
Drug Release Kinetics Liberation due to Polymer erosion Self diffusion through the pore. Release from the surface of the polymer Pulsed delivery initiated by application of an oscillating or sonic field
Preparation of Microspheres Aq. Soln of 8% w/v acrolein 0.5% sodium bisulphite polyglutaraldehyde conjugate pH adjusted to 10.5 Dialysis and centrifugation Microspheres
CharacterizationParticle Size and shape:• The most widely used procedures are conventional light microscopy and scanning electron microscopy.• Confocal laser scanning microscopy is a non destructive visualization technique.• Confocal fluorescence microscopy is used for Structural characterization.
Capture Efficiency It is the percent entrapment determined by allowingwashed microspheres to lyse. The lysate is subjected to the determination of active constituents. % entrapment = Actual content ________________ * 100 Theoretical content
Density determination is done by using a multivolume pychnometer. Micro electrophoresis is an apparatus used to measure electrophoretic mobilityof microspheres. Surface associated amino acid residue isdetermined by C – Acetic acid conjugate. The accuracy depends on the timeallowed for conjugation.
Polymeric Carrier for Antigens ANTIGEN POLYMER USED PREPARATION METHOD Staphylococcus dl- PLGA Solvent evaporation enterotoxin B Diphtheria toxoid dl- PLGA W/O/W emulsion Hepatitis B Surface Phase Separation antigen PGA emulsion Tetanus toxoid PLA, PLGA Emulsion Bovine serum albumin PLA Adsorption
StabilityStability is affected by many factors such as:o Polymero Moistureo Lyophilizationo pHo Shearingo Temperatureo Rotationo Salt
Advantages Improved antigenicity by adjuvant action. Modulation of antigen release Stabilization of antigens.
Efficient transport across microvascularbarrier can be achieved by: Magnetic dragging of the magnetic microparticles directly through endothelium and basement membrane. Facilitated transport of specific ligand drug conjugates or coated microspheres across endothelium as a result of ligand binding to luminal surface antigen or receptors. Transient regional opening of endothelium function combined with vascular infusion of drug carrier that becomes sequestered in the extracellular complex.