Macromolecules Flashcards
what are macromolecules
They are large molecules. This include proteins, lipid, nucleic acids and carbohydrates
uses of macromolecules
Replacement therapy
Supplement therapy
Therapeutic antibodies
Site specific carriers- recognise delivery site
Examples of peptide and protein macromolecules
Colony stimulating factors Interferons and interleukins Enzymes Hormones Recombinant protein vaccines Growth factor: tissue/bone growth and neurotropic factors
Examples of peptide and protein macromolecules
Colony stimulating factors Interferons and interleukins Enzymes Hormones Recombinant protein vaccines Growth factor: tissue/bone growth and neurotropic factors Monoclonal antibodies Recombinant soluble receptors
What are the barriers to manufacturing and delivery peptides and proteins
- In vitro stability barrier
- Metabolic barriers
- Absorption barriers
What are the 3 categories of in vitro stability barriers?
Instability due to reactive side chains
Degradation caused by environmental` factors
Manufacturing process
List some reactive side chains/reactions that alter side chains
Transpeptidation Deamination Side-chain hydrolysis Proteolysis Disulfide exchange b-elimination Oxidation Racemization
Environmental factors that cause degradation
Temp: increase flexibility of molecules so more collisions therefore more aggregation
pH: neutralizes charge
Ionic strength
Pressure
Detergents: can lead to aggregation if wrong amount is used.
What are the manufacturing process that determine in vitro stability
- Determine degradation routes
- Choose adequate additives
- Test stability of the solution
- (development of a solid formulation)
What 2 methods are used when developing solid formulations
- Lyophilization/freeze drying
2. Spray dry
How does freeze drying/lyophilization work?
sublimination of water (water form solid stage into vapour)
How does spray drying work
It is the atomization of a solution into hot air to dry it.
Benefits of freeze drying
Allows for the desorption of bound water so little water remains in the powder.
Problems with freeze drying
Irreversible aggregation can occur
denaturing
What are the solutions to the problem faced in freeze drying?
Add cryoprotectant and other additives
List some cryoprotectants
Sugars: sucrose, mannitol, sorbitol
Polymers: Dextrant, PVC, and PEG
others: Bovine serum albumin/BSA and AA
When would spray drying be used instead of freeze drying?
When making nasal and pulmonary formulations
What are the metabolic barriers of macromolecules?
Enzyme degradation.
- site of enzyme degradation include:
= GI lumen: Pancreatic enzymes against larger peptides
= Brush boarders: Protease cleave oligopeptides (small bioactive peptides)
= Intracellular degradation:(lysosomes occurs in other intracellular organelles )
What are the absorption barriers?
Too Large: cannot bass tight junction
Too hydrophilic: cannot pass through hydrophobic cell membrane
What are the 4 types of transport that occurs and what are problems with them in relation to macromolecules?
Paracellular: Size
Passive: Size and hydrophilicity
Active transport: size
Endocytosis: enzymatic degradation in lysosomes
What characteristics do absorption enhancers need to have?
Be pharmacologically inactive
Be specific in its action
Carry the intact drug to the site of absorption- not affect integrity
Prolong its residence time at the absorbing surface- prolong contact
Reversible increase the permeability of the mucosal epithelium
Do not damage the epithelium
What are the 5 classes of absorption enhancers?
Surfactants AA Derivative Ca2+ chelators Fatty acids polymers
Types of surfactants and name some examples
Non-ionic (polysorbate 80) can be packed densely
Cationic
Anionic (SDS, sodium dodecyl sulfate): work better than non-ionic depending on MW
Mechanism of actions of surfactants
shortening of microvilli of the cells
actin disbandment
structural separation of the tight junctions
damage to the apical cell membrane by detergent-like action, the monomeric form adsorbs and penetrates the plasma membrane leading to removal of membrane constituents
What is the proposed mechanism of AA derivatives
condensation with the macromolecular drug and facilitation of its absorption into the lymphatic system
the condensation complex might reduce the hydrophilicity of the drug
MOA of Ca2+ chelators
- disruption of actin filaments, contraction of the junction-associated microfilament cytoskeleton
- disruption of adherens junctions
- diminished cell adhesion
- activation of protein kinases
- chelation of serosal Ca2+
How do fatty acids aid with the absorption of macromolecules?
They can interact with the cell membrane.
C10-C12 is the ideal length.
Why are polymers mostly used?
- Safe: not absorbed therefore no systemic side effects
- Mucoadhesion: prolong contact time between drug and site of absorption
- Protection from enzymatic degradation: steric hindrance
- Physically entrap the drug
What is Chitosan and what properties does it have ?
It is a polysaccharide obtained from crabs and shrimps as chitin
- Biocompatible
- Slowly biodegradable
- Semi-Natural polymer
- Only protonated chitosan are effective : this means they are pH dependent
What is poly acrylic acid and what propertied do they have?
A synthetic polymer
Mucoadhesive
Enzyme inhibitor: chelation of Ca2+ and Zn2+ ions that are cofactors needed for the proteolytic activity of the enzymes
Absorption enhancer: facilitates the paracellular transport of macromolecules
How does polyacrylic acid and chitosan work
They both work in the paracellular route.
Where can tight junction be found in the body
Epithelial lining of digestive system, ducts, cavities of glands, liver, pancreas capillary, walls urinary bladder , BBB, nasal mucosa
What is the function of the tight junction?
1; prevent passage of molecules and ions through the space between cells, providing control over what substances are allowed through.
2: block the movement of integral membrane proteins between the surfaces of the cell maintaining their specific function: e.g., receptor-mediated endocytosis at the apical surface and exocytosis at the basolateral surface.
What is the definition of a mucoadhesive
- A molecule that sticks to mucosa (not mucus).
- Bio-adhesives are synthetic or biological and can stick to a biological structure or tissue
What is mucous made up of
95% water
0.5-5% glycoproteins
1% minerals, salts and lipids
0.5-1% free proteins
What is the function of mucus?
protect, lubricate and have site function: the stomach as mucus to protect it from the acid
Why are mucoadhesive used
They increase the time that the drugs in contact with the absorbing mucosa and increase the chance of absorption.
What is the mechanism of mucoadhesion
- wetting and swelling, the polymer comes into contact with the biological tissue 🡪 hydrophilicity
- interpenetration and entanglement of polymer chains and mucin macromolecules 🡪high molecular weight and chain flexibility
- formation of strong bonding between the entangled chains 🡪numerous hydrogen bond forming groups
How do mucoadhesive promote oral drug bioavailability
- localising the drug in a specific site
- promoting intimate contact between drug and absorbing mucosa
- prolonging the residence time in the GIT
- protecting the drug from dilution and possible degradation
What are the factors that affect mucoadhesion
Molecular weight- strength increases above 100,000. range form 200,000-1,000,000
Flexibility- for entanglement. More flexible = better efficacy
Hydration: required for mucoadhesive polymer to expand and create a macromolecular mesh
Cross-link density: increased density of cross linking means a reduced absorption of water into polymer network and so decreases rate of interruption between polymer and mucin
Charge
Concentration
