Protein in nanomaterials Flashcards
Why protein-based nanomaterials?
- Biodegradable –> proteases and hydrolysis
- High drug binding capacity –>Many binding/conjugation methods both covalent and non-covalent. Hydrophobic drug binding and reduces drug toxicity
- Useful intrinsic properties of proteins –> bind hydrophobic molecules (Like drug) and can act as target, protection and functionality.
- Biocompatible –> Water soluble and low toxicity
- Abundant renewable sources –> Proteins are retrieved from several different sources:
- Expression in bacteria
-Expression in mammalian cell lines
- Retrieval from plants
- Retrieval from animal sources
GRAS
Generally recognized as safe
All-protein particles example
An example of an all-protein particle is Abraxane. This particle consists out of paclitaxel (drug) which is surrounded with albumin. Albumin is nutrients for the tumor so naturally the particle will find it way to the tumor. The particle will be taken up via albumin gp60 mediated transcytosis.
Desolvation
A desolvating agent like alcohol or acetone is added to an aqueous solution of protein under stirring. The protein will dehydrate, and this will change its form from stretched to coil.
Coacervation
A salt is added to a protein in solution, this reduces the solubility of the protein. This will lead to a transparent solution at the top and a polymer rich dense phase at the bottom. very similar to desolvation but makes use of changing solubility of proteins mostly regarding pH and ionic strength.
Emulsification
The solvent is homogenized with high speed followed by the evaporation of the solvent. The evaporation is done under continuous magnetic stirring or under reduced pressure. After this the solidified nanoparticles will be collected by ultracentrifugation.
Nanoprecipitation
Two mixable solvents are used. where both protein and drug must be soluble in one solvent and insoluble in the other one. Nanoprecipitation occurs by rapid desolvation of the protein when the protein solution is added to the non-solvent.
Nanospray
Spray drying, as shown by its name, is a technique used to dry liquids into particles under a continuous process
Self-assembly
Protein micelles can be created spontaneously when the individual protein chains are dissolved in a n aqueous solution beyond the threshold concentration (Critical micelle concentration or CMC) and critical solution temperature (CMT) to form nanosized aggregates.
Why crosslinking?
To increase the stability of all protein particles
Examples: Glutaraldehyde and NHS-maleimide bifunctional molecule
Manipulating a protein
- Incorporation of non-canonical amino acids via residue specific or site-specific incorporation
- CRISPR-Cas9: Promotes genome editing using DSB (Dubbel strand Breakage) at target loci
Upon DSB there can be 2 repair systems:
- Homology directed repair (HDR) –> can result in insertion of wanted DNA strand
- Non-homologous end joining ( NHEJ) –> Can result in frame shift and subsequently knock-out
Protein material as targeting unit
Antibodies
* Chimeric ab
* Humanized ab
* Completely human ab (‘newest’)
Cell penetrating peptides
CPPs can translocate through various biological membranes. In comparison to other cells they have low toxicity, dose-dependent efficiency and efficiency for a variety of cell types.
Examples of non-specific CPPs:
TAT –> HIV-1 virus derived. Has a lot of positive amino acids ( K and R). Supposedly mostly non-endocytosis uptake with small cargo
Oligo-arginine –> Peptide composed of only arginine
Targeting peptides
- RGD –> tripeptide derived from fibronectin and cell recognition integrin
- Somatostatins peptide analogues –> are synthetic compounds that mimic the actions of the natural hormone somatostatin. somatostatins are GPCRs associated with tumors
- LHRH (luteinizing hormone releasing hormone) –> A LHRH targeting peptide is a short chain of amino acids that specifically binds to the LHRH receptor
- Angiopep-2 –> derived from ligands for lipoprotein receptor-related protein-1 (LRP-1). LRP-1 is expressed on the blood-brain-barrier (BBB).
Phage display
They make use of bacteria phages where the gene encoding for the protein is inserted. The bacteria will express the protein on the surface. A library of phages is used where different proteins are expressed. These phages are exposed to the wanted target (receptor) and only some of the protein phages will interact with these receptors. The non-binding phages are washed away. The phages that are binned are recovers by a elution step for example affinity chromatography.
Sequence alignment
Check which sequence is well kept in proteins with similar function Using known amino acid/DNA sequences
It involves arranging the sequences in a way that highlights their similarities and differences, with the goal of identifying evolutionary relationships and determining the functional or structural similarities between them.
ELISA (Enzyme linked immuno sorbent assay)
to find binding of a target protein/peptide to certain proteins
Bacteriophage
is a virus ( for a bacteria) and contains DNA/nuclei acids (viral genome) on the inside.
Virus
Many different types and forms and contain a viral genome. They make use of the host cells machinery to multiply.
Viral capsid self-assembly
Capsid self-assembly
- Often upon environmental trigger
- Often N-and/or C-terminus of CP is involved
Scaffolding protein-assisted capsid self-assembly
- Proteins introducing protein-protein interactions between capsids during assembly
- Scaffolding protein function:
Initiation by nucleation
increasing effective concentration CPs
directing assembly into correct quaternary structure
inserting or ejecting other proteins to the assemblies
making sure capsids are not being filled with nonspecific proteins
stabilization of the procapsid
Nucleic acid packaging and nucleic acid-assisted capsid assembly
- Often the case for ssRNA viruses
- Often simultaneous nucleic acid packing and capsid packing/assembly
Virus like particles (VLPs)
Is a type of vaccine that mimics the structure of a virus but does not contain any genetic material, making it non-infectious
* there are a lot of CPs able to assemble without nucleic acids present
* protein cage of virion
* without natural cargo (nucleic acids)
* So no infection/danger
Why VLPs?
- Specific structure
- Highly repetitive surface induces strong b cell response
- Size of VLPs is ideal for uptake APCs
Elastin-like polypeptides
- Synthetic sequence
- coacervates in similar way as tropoelastin
- Val-Pro-Gly-Val-Gly (VPGVG)
LCST behavior ( lower critical solution temperature)
- These crosslinked troppoelastin (elastin) form a fibrillar structure/coacervate upon going through the Tt
- below Tt –> non-polar residues hydrated by waterlayer
- above Tt –> non-polar side chains (hydrophobic regions) make contacts (thereby releasing/liberating the ‘bound’ water)
ELPs show LCST behavior
- changing guest residue –> change in Tt
- increase in hydrophobicity –> decreases Tt
- increase in ELP length –> decrease Tt
- Also increase in salt concentration –> decrease Tt
ELP based nanoparticles
- ELP block copolymer
- Crosslinked ELPs
- ELP-hybrid
