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Encapsulation Flashcards

1
Q

What is encapsulation?

A

Process in which tiny particles or droplets are surrounded by a coating

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2
Q

What are the 2 types of encapsulation?

A

microencapsulation:

  1. reservoir type
  2. matrix type (disperse drug all over)
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3
Q

When is nanoencapsulation used?

A 
1nm-1um
~ imaging - phase contrast
~ injectable drug delivery systems
~ vaccine
~ bactericides/ microbiological uses

e.g. Silver: Preservatives, for disinfectants
Gold - inert, once in particle; change surface pprty stick onto surfaces; inc phase contrast when doing imaging

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4
Q

When is microencapsulation used?

A
  • reasonable payload
  • hold nutrients, enzymes, cells, etc.
  • offers protection, diffusion barrier
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5
Q

What is macroencapsulation?

A
  • high payload possible
  • consistent production quality
  • multi-particulate drug delivery system
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6
Q

What are the properties of nanoencapsulation?

A

Properties: low payload, limited protection/stability, highly permeable

Deliver small amt of active; tend to be very sensitive/ difficult to manage
Produce small scale and need to be protected/stored at low temp to prevent degradation

If highly potent molecule/bioactive e.g. Antigen or some mRNA - stability is a problem
It is also permeable

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7
Q

How are polymeric nanoparticles produced for viable commercial production?

A

Nanoporous membrane extrusion (NME)

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8
Q

Why encapsulate?

A
  1. protection against moisture, oxygen, light
  2. prolong shelf life (confer stability)
  3. Prevent premature release and pre-reaction
  4. Mask undesirable taste, odour, and/or colour
  5. Provide controlled release - rate, target, timed, delayed (zero order)
  6. Convert liquid into solid (ease of handling)
  7. Reduce flammability
  8. Improve safety and handling

provides isolation, entrapment structuration, protection or controlled release of a sensitive or reactive material (flavour, fragrance, bioactive) from surrounding/environment.

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9
Q

How does dripping/extrusion works?

A
  • congeal: droplets from nozzle/orifice into inhospitable medium to cause coagulation/ cross-linking
  • or vibrate; break liquid stream into droplets
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10
Q

How does coacervation works (liquid-based formation)? And what are the uses?

A
  • manipulation of pH, temp, solubility, ionic interactions
  • separation of liquid phase of coating material from a polymeric solution and encapsulating the core particles by a uniform polymeric layer
    e. g. gelatin-gum; gelatin-acacia; gelatin-sodium alginate
  • well-established batch process
  • require skillful operatory/operation
  • often contains gelatin (others: caesin, soy proteins, chitosan, starches, gums, etc.)

Use: carbonless paper, pesticide, fragrances, liquid, crystals, detergents, paint stabilisers, adhesives, etc.

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11
Q

How does emulsification works (liquid-based formation)? What are the uses/applications?

A
  • utilisation of surfactants and surface activity (emulsion-based)
  • formation by water-organic solvent mixtures with surfactant
    e. g. sodium alginate soln in iso-octane + surfactants, hardened using calcium chloride (to form a cross-linked matrix system)

Applications:

  • protects drug from environment
  • masks unpleasant taste and odour
  • reduces drug volatility
  • reduces gastric irritation by drug
  • separates incompatible components
  • controls drug release
  • produces chemoembolization agents
  • produces microbioreactors

Encapsulate cells; removal of toxic pollutants e.g. Mercury, if use calcium alginate microsphere, calcium ion exchange with mercury

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12
Q

Why coating of cores containing active ingredients API is important in macroencapsulation?

A
  • Modification of drug release: delayed/sustained release (0 order)
  • Protection of drug: taste masking, moisture/gas barrier, UV protection, add colour
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13
Q

What are the different coated dosage form systems and its uses?

A

100microns and above

Coated particle: taste masking, stability enhancement

Coated pellet: multi-drug delivery system; multi-unit pellet system (MUPS) tablet

Coated tablet: decorative & identification; enteric-coated; sustained release coated; osmotic pump

Coated capsule: not common, enteric release, prolonged-release

  • release of drug in planned, predictable, slower-than-normal manner
  • drug delivers at planned and controlled rate
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14
Q

What are the advantages of controlled release systems?

A
  • 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 (fewer dosage units used)
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15
Q

What are 5 coating processes for pharmaceuticals?

A
  1. Compression: specialised tablet press, with capability of multi-layer compression (tab-in-tab)
  2. Pan coating: popular and well-established method to coat tablets
  3. Air suspension: Wurster coating to coat small particles (e.g. pellets)
  4. Spray coating: spray dryers convert liquid feeds to dry powders (for coating)
  5. Melt coating: hot melt extrusion or spray congealing (prilling) (niche tech)
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16
Q

How to design sustained drug release pellet?

A

Diffusion barrier coating (outermost) and Drug layer: polymer and drug (middle) - application by fluid bed coating

Drug layer: polymer and drug and Nonpareil bead (sugar/ microcrystalline cellulose) (innermost) - Drug-loaded pellet may be prepared by extrusion-spheronisation

~ Nonpareils used as cores to be layered with drug, then overcoated with diffusion barrier polymer coat
~ Drug-loaded pellets are prepared by extrusion-spheronisation, then overcoated with a diffusion barrier polymer coat

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17
Q

What are the steps for core production by extrusion-spheronisation? (for the drug-loaded pellets, not for the non-pareils)

A
  1. dry blending
  2. wet massing
  3. extrusion
  4. spheronisation
  5. drying
  6. coating
18
Q

How is fluid bed drying and coating carried out?

(2 layers for the nonpareils: first layer: drug and polymer; second layer: diffusion barrier coating)
( 1 layer for the drug-loaded pellets: outer layer: diffusion barrier coating)

A
  1. Bottom-spray - Wurster coating: for coating pellets (widely used); dry at top
  2. OR Side/centrifugal spray systems; very efficient coaters for particles
  3. OR top spray; often used for granulation rather than coating; coating efficiency is inferior to bottom or side spray systems
19
Q

How does pellet coating systems with ‘envelope’ air works?

A
  • three-component nozzle
  • bottom spray or side spray
  • spray onto pellet
  • envelope air concept around spray nozzle extends spray into coating substrate bed and minimises local over-wetting; can be used to pattern spray dispersion; FlexStream side nozzle can be removed for cleaning during process run
  • envelope air: prevents air from hitting the floor of the container, ensure spraying into pellets
20
Q

What are the properties of GIT? How does pellets interact with the GIT?

A

Pellets can pass closed pylorus port; not dependent of GER

~ Stomach: 1/3-3h transit time; 8L gastric juice, pH 1-3

~ SI: 2-7h transit time; 9L intestinal juice, pH 5-7.5

~ Colon: 20-36h transit time; 1L liquid juice; 0.15L liquid, pH 7.2

Tablet are larger needs to be break down before it escapes
Reduced GER requirements for pellets
But pellets must have a coat - coat will disintegrate in the stomach first

21
Q

What are the uses of spray drying?

A

Convert solutions; suspensions and emulsions to dry powders

Inhalation products

Highly efficient and versatile
Fast and continuous drying process
Stabilised on a large industrial scale

22
Q

What are the advantages of spray drying?

A
  • reduce volume, liquid to dry form
  • ease dosing, handling and transport
  • improved chemical and biological stability
  • defined shape and size
  • porous and high specific surface, easy dissolution
23
Q

How to prepare spray dried microparticles for suspensions and solutions?

A

Spraying of suspensions: insoluble active a solution of shell material

Spraying of a solution: active and shell material as a liquid

coating of small particles: 10-200um

24
Q

What are the functional principles of spray drying?

A

Atomised droplets –> contacts hot drying gas –> dry surface forms (heat + evaporation of water) –> dry particle

solid
shrivelled
hollow
cenosphere
particle distribution
25
Q

What are some nozzle designs for spray drying?

A

2-fluid

3-fluid

Ultrasonic (no air)

Pressure (no air, liquid is pressurised)

Rotary atomiser (no pressured air here, rotate at high speed) (10-12 thousand revolutions
High speed
Centrifugal force
Liquid pass through slot and broken down)

26
Q

What are the spray drying fundamentals in terms of particle size distribution?

A

Pressure nozzle atomization: narrow distribution)

Rotary atomizer: Intermediate distribution

2-fluid nozzle atomization (fountain): broader distribution

27
Q

What is the concept of spray prilling (congealing)?

And what are the uses?

A

Uses COLD air instead of hot air
Hot melt spray in cold air
E.g. Palm oil stearic acid

  • for food and pharma products, also cooling, chilling, and congealing
  • confined to ‘smaller’ sizes (compared to fertilisers/chemical products) with d50 in 200-1500um (0.2-1.5mm) range

Use: preparing meltable powders (lubricants); taste masking, controlled release products

28
Q

What are the two types of capsules?

A

Hard gelatin capsule

Soft gelatin capsule

29
Q

What are the issues with capsules (soft and hard)?

A
  • Gelatin is an animal protein; religious sensitives, objections; may be associated with animal disease, animal rights, green-house gas
  • moisture-sensitive
  • properties may change with adsorbed constituents e.g. aldehydes
30
Q

What are the fill capacity of capsules (hard gelatin)?

A
  • Sizes: 5(0.13); 4(0.20); 3(0.27); 2(0.37); 1(0.48); 0(0.67); 00(0.95); 000(1.36)
    ( ) vol in ml
    Popular sizes: 0-4
    Can have self-locking mechanisms

Capsule fill weight depends on tapped density

Capsule filled wt = Tapped Density x Capsule Volume
Good fill depends on good flow properties

31
Q

What are some alternatives for non-protein based capsules (vegetarian capsules)?

A
  • Hydroxyproplymethyl HPMC
  • pullulan (Water soluble polysacc)
  • HPMC and carrageenan
  • alginate
32
Q

How do we assess capsule quality?

A
  • assay
  • uniformity of dosage units
  • disintegration
  • dissolution
33
Q

What kind of shapes and sizes soft gelatin capsules come in?

A
  • round
  • oval
  • oblong
  • tube
34
Q

What are the advantages of softgel capsules?

A
  • no compression stage, can contain poorly compressible drug
  • liquid fill avoids powder flow and mixing problems
  • avoid O2 or moisture degradation of drugs during long term storage; protected by gelatin shell
  • for poorly water soluble drugs, in a liquid vehicle, emulsified in GIT as fine droplets
35
Q

What are some critical formulation tips when making soft capsules?

A

When filling matrix, should avoid:

  • emulsions, may crack (prefer medium W/O emulsions; as water will dissolve with gelatin O/W not preferrable)
  • Surfactants (high); affect gelatin integrity
  • pH <2.5, hydrolysis of gelatin
  • pH >7.5, tanning effect on gelatin, insolubility
  • aldehydes, cross-linking, tanning effect (darker; pigments released?)
36
Q

What should we take note for the bioavailability from capsules?

A
  • Dissolution of gelatin shell (puncturing) quickly disperses content into the intestinal liquid and bioavailability should be good, similar to liquid or powder/granule preparations
  • discharge of capsule content depends on flow of materials within, can be problematical for hydrophobic materials –> thus, add surface active agent to aid wetting and discharge
37
Q

For a repeat action preparation (sustained dose), what kind of coating does pellets have?

A

Pellets with pulsatile release coatings

e.g. prompt dose –> first sustaining dose –> second sustaining dose

38
Q

What are some methods for multiparticulate drug delivery system?

A
  • extrusion-spheronisation (drug-loaded pellets)
  • fluid bed drying and coating (for the layers: diffusion barrier coating and drug layer for nonpareils)
  • pellet coating systems with ‘envelope air’ (seen in bottom and side spraying)
39
Q

What is the difference between spray drying and spray priling (congealing)?

A

spray drying involves hot drying gas

spray congealing involves cold air

40
Q

What are the machines for the production of capsules?

A

hard gelatin capsules: FEC40 aka Fette Compacting

soft gelatin capsules: soft gel technology

41
Q

What are some techniques for encapsulation?

A
  • dripping/extrusion
    ~ congealing
    ~ vibration

liquid-based formation:

  • coacervation
  • emulsification

Solid (16 decks)

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