Bio- interactions of nanomaterials
Biodegradble
A substance that can breakdown naturally into harmless products through the action of living things (Being decomposed by bacteria or other living organisms). For biomedical applications it is obligatory to use bio-degradable or at least biocompatible polymers as building block. Examples include: Polycaprolactone (PCL) or Poly(lactic acid) (PLA) Oligo- and polypeptides.
Biocompatible
A substance that is not harmful/toxic to living tissue and does not interfere with natural processes in living tissue.
Polymers in clinical use
Are polymers which are already used in the medical field for treatment.
Opsonins
An antibody or substance that binds to foreign cells and makes them (the foreign cells) more vulnerable to phagocytosis. Phagocytosis is a process where a phagocyte captures a virus or infected cell and breaks it down.
Stealth behavior
Stealth behavior is the behavior in which the liposome is not detected by the RES by the PEG mantle, which results in a prolonged circulation time. Always neutral or negatively charged, positively charged cells will be taken up by macrophages.
Effect of polymer glass transition
• Amorphous polymers have a glass transition temperature (Tg) which is the transition from glassy to rubbery state.
• Below Tg: polymers have lower mobility: they are hard and brittle (similar to glass)
Above Tg: polymers have higher mobility: they are flexible and softer (similar to rubber)
Factors that influence Tg:
• Molecular weight (higher Mw lowers chain end concentration, yielding higher Tg)
• Molecular structure (inflexible side groups reduce mobility and increase Tg)
• Chemical cross-linking (more cross-links reduces mobility and increases Tg)
• Polar groups (polar groups cause forces between molecules, increasing Tg)
Polybutadiene is an example of a polymer with a low Tg and is often used in drug delivery research in the form of polybutadiene-b-polyethyleneglycol (Pbd-b-PEG)
Effect of pKa of polymer side groups
Polymer side groups with low pKa have the tendency to become protonated in low pH solution. Therefore, this can be used to (dis)assemble polymersomes upon pH change. Important use as drug release mechanism Fe zwitteronic or ionizable blocks.
Peptosome
A peptosome is a type of liposome, which is a spherical vesicle made up of a lipid bilayer. However, unlike a traditional liposome, a peptosome also contains peptides (short chains of amino acids) within its lipid bilayer.
Reticuloendothelial System (RES)
The Reticuloendothelial System (RES) is a network of cells and organs in the body that helps in the defense against foreign substances, such as bacteria and viruses. The system consists of specialized cells called macrophages, which are found in various organs throughout the body, including the liver, spleen, and lymph nodes.
Macrophages play a crucial role in this process, as they are able to recognize and bind to these foreign substances through specialized receptors on their cell surface. Once bound, the macrophages will engulf the foreign particles in a process called phagocytosis. The engulfed particles are then broken down by enzymes within the macrophage and eliminated from the body.
ReticuloEndothelial cells are able to perform phagocytosis or foreign materials and/or particles
Use of lower critical solution temperature
Property of polymers where they go from soluble state to insoluble. Above this temp. polymersomes form, below they dissolve. This happens because of self-assembly of the hydrophobic parts, creating a membrane. ENTROPY OF WATER