Encapsulation and Capsules Flashcards
What is the definition of encapsulation, and what are the different encapsulation technologies available?
encapsulation is the process in which tiny particles or droplets are surrounded by a coating.
types:
1. nanoencapsulation: used for vaccines, injectable drug delivery systems or imaging-phase contrast
2. microencapsulation: reasonable payload, holds nutrients, enzymes and cells.
3. macroencapsulation: high payload possible, consistent product quality, used for multi-particulate drug delivery.
What are the properties of nanoencapsulation?
- low payload
- limited protection/stability
- highly permeable
- can be prepared by top-down or bottom-up method
What is one application of nanoencapsulation?
viable commercial production of polymeric nanoparticles
What are some reasons for encapsulation?
- protection against moisture, oxygen and light
- prolong shelf-life, increasing stability
- prevent dose dumping
- mask undesirable taste, odor or colour
- convert liquid into solid form (ease of handling)
- reduce flammability, improving safety
What are some techniques for encapsulation?
- Emulsification
- Spray drying
- Fluid bed coating
- Extrusion
- Coacervation
- Solvent change/removal
What are the properties of dripping/extrusion?
- nozzle drips starter seed/capsule containing bioactive substance into inhospitable medium.
- inhospitable medium coats substance.
What are the properties of coacervation?
liquid phase of coating material from a polymeric solution is separated.
- core particles are encapsulated by a uniform polymeric layer.
- this is achieved through the manipulation of pH , temperature, solubility and ionic surfactants.
- e.g. gelatin-gum, gelatin-acacia, gelatin-sodium alginate
What are some advantages and limitations of coacervation?
Advantages:
- uses batch process which is a well-established method
- wide variety of biopolymers can be used, most common one (gelatin) is easily accessible as well.
Disadvantage:
- require skilful operator/operation
What are the properties of emulsification?
- formation by water-organic solvent mixtures with emulsion
- e.g. sodium alginate solution in iso-octane + surfactants, hardened using calcium chloride
What are some applications of emulsification?
- protects drug from the environment
- masks unpleasant taste and odour
- reduce drug volatility
- reduce gastric irritation by drug
- controlled drug release
What is macro encapsulation, and what is it used for?
- macro encapsulation refers to the coating of cores containing active ingredient to modify drug release (delayed/sustained release), as well as to - protect drug >> taste masking >> moisture/gas barrier >> UV protection >> Add colour
What are the different coated dosage form systems?
- coated particle : popular in taste masking, stability enhancement
- coated pellet: multi-particulate drug delivery system
- coated tablet: decorative and identification, enteric-coated
- coated capsule: not common, used for enteric or prolonged release
What is a controlled release system?
- release of drug from dosage form that occurs in planned, predictable and slower-than-normal manner.
- drug is delivered at a specific planned and controlled rate.
What are the advantages of controlled release systems?
- extended daytime and night-time activity of the drug
- potential for reduced incidence of side effects
- reduced dosage frequency
- increased patient compliance
- potential lower daily cost to patient
What are the different coating processes for pharmaceuticals?
- compression
- pan coating
- air suspension
- spray coating
- melt coating
What is the design of a sustained drug release pellet?
- diffusion barrier coating
- drug layer: polymer and drug
- nonpareil bead (sugar/MCC)
- nonpareils are used as cores that are coated by drug and polymer, which are obtained from extrusion and spheronization.
- diffusion barrier coating is made by fluid bed coating.
How would you describe pellet coating systems with “envelope” air?
Envelope air comes out of nozzle via bottom or side spray, coats substrate bed and minimises local over-wetting.
How long does a drug remain in the GI tract?
7-10 hours
What are the properties of spray drying, and what is it used for?
- liquid containing API is sprayed into a column that contains vents to allow hot air to access and evaporate the liquid, before it cools to become a powder.
- during the process of spraying small particles can be coated.
- both suspensions and solutions can be sprayed.
- used as a simple one-step process to convert liquid solutions into dry powders.
What are the advantages of spray drying?
- reduce volume, liquid to dry form
- ease of dosing, handling and transport
- improved chemical and biological stability
- porous and highly specific surface, easy dissolution
What can you say about the size distribution for a two-fluid nozzle, a rotary atomiser and a pressure nozzle?
- pressure nozzle: narrow distribution
- two-fluid nozzle: extensively used, middle size distribution
What are the different types of capsules?
- hard gelatin capsules
- capsule consists of two parts, a cap and a body, that fit one inside the other. - soft gelatin capsule:
- soft elastic gelatin capsule or softgel that consists of a unit of continuous gelatin shell surrounding a liquid fill material.
What are some issues with capsules?
- problems with gelatin:
1. it is an animal protein and there may be religious sensitivities, may be associated with animal diseases, animal rights and greenhouse gas emission.
2. moisture-sensitive
3. properties may change with adsorbed constituents (e.g. aldehydes)
How do you determine the fill capacity of hard gelatin capsules?
- Hard gelatin capsules have 5 sizes, popular sizes range from 0-4.
- capsule fill weight depends on tapped density.
- capsule fill weight = [tapped density] x [capsule volume]
- good fill depends on good flow properties of feed.
Examples of non-protein based capsules
HPMC, alginate
What are the tests in which one can evaluate capsule quality?
- assay
- uniformity of dosage units
- disintegration
- dissolution
What are the different shapes of soft gelatin capsules?
round, oval, oblong, tube
What are the advantages of soft gelatin capsules?
- no compression stage, can contain poorly compressible drug
- liquid fill avoids powder flow and mixing problems
- prevents oxygen or moisture degradation of drug during long term storage
- ideal for poorly water soluble drugs
What are some things to avoid in the fill content of softgel capsules?
- emulsions (may crack)
- high concentration of surfactants
- pH<2.5, hydrolysis of gelatin
- pH >7.5, gelatin may tan
- aldehydes, cross-linking or tanning effect
