L9 Artificial Cells Flashcards
Re Quiz 8 Week 11
In the context of fabricating artificial counterparts, what are “Cells”?
They’re basically biological machines that can carry out a series of biochemical reactions, and it is designed in such a way that these biochemical reactions either (1) don’t interfere with each other, or (2) reactions themselves interact with each other in a controlled manner (and of course, these reactions are heavily dependent upon both the surrounding ambient conditions and the reactant concentrations)
- Name TWO functions or features of cells that could be replicated using artificial/synthetic means. (2 marks)
- Compartmentalisation - separating the ‘individual reactions’ from one another
- ‘Platforms’ for catalysis/enzymatic reactions to generate energy (not just energy, but other biomolecule products)
-
Cellular membrane - the function of the cell membrane is allow diffusion/permeability of molecules, also just structure (to house everything in, and also to station certain proteins/enzymes within or on the membrane itself)
* Regarding:*
Genetic expression (ambitious feasibly to be done artificially) - ‘genetic expression’ is a specific example of a biological ‘reaction’, and it is complicated at this stage to be replicated with artificial/synthetic means
Homeostasis (similar issue with above).
Note**: received correct mark for ‘Liposomes’
- Name THREE applications (or potential applications) of artificial cells, either in biomedicine, or otherwise. (3 marks)
- Nanosensors
- Drug delivery
- Enzyme and gene therapy
- Cell and stem cell therapy
My answers (marked correct):
- Glaucoma therapy
- In vitro modelling for cell culture studies
- Tissue Engineering –> Regenerative MEdicine
- One example to make ‘artificial cells’ is through the hypotonic treatment and extrusion of the red blood cell (RBC) core to produce RBC-membrane derived vesicles, which can then encapsulate nanopolymeric cores.
(a) Is this either a ‘top-down’ or ‘bottom-up’ approach in developing artificial cells? (1 mark)
(b) What is the main benefit of this particular example of encapsulating polymeric nanocores with RBC-membrane derived vesicles? (1 mark)
Key concept: Extraction, or simplification of real cells.
a) Top-Down - Reducing complexity of the red blood cell
b) Appear similar to RBCs (exhibit some of the key characteristics of living cells); no immune reaction/evade the immune system (if the immune system sees a particle with a coating (the immune system cells look at the surface only) - a coating that is non-foreign, it would just leave it alone as if it was non-foreign.
(My answer: “Surface coating” with a biologically-derived membrane = improved biocompatibility)
- Which of the following statements is TRUE regarding liposomes and polymersomes? (of the TEN statements, SEVEN are true)
(A) Both liposomes and polymersomes have both hydrophilic and hydrophobic domains.
(B) Polymersomes have lower chemical versatility than liposomes.
(C) Polymersomes can be made into single unilamellar, large unilamellar, and giant unilamellar vesicles, similar to liposomes.
(D) Liposomes generally have thinner membranes than polymersomes.
(E) Liposomes have higher lateral fluidity than polymersomes.
(F) Polymersomes have lower membrane permeability than liposomes.
(G) Liposomes can have molecules within both the hydrophobic membrane layer and the hydrophilic core, whereas polymersomes can only have molecules in the hydrophobic membrane layer.
(H) Polymersomes generally have higher physical and chemical stability versus liposomes.
(I) Polymersomes are biocompatible.
(J) Liposomal membranes can be functionalized with molecules, whereas polymersome membranes cannot be functionalized with molecules.
Note: Polymersomes are ‘stronger’ versions of liposomes. Instead of glycophospholipids in liposomes, in polymersomes, the membrane is made of polymers with each ends hydrophilic and the ‘body’ is hydrophobic. As a result, the membranes of polymersomes tend to be thicker.
True:
(A) Both liposomes and polymersomes have both hydrophilic and hydrophobic domains.
(C) Polymersomes can be made into single unilamellar, large unilamellar, and giant unilamellar vesicles, similar to liposomes.
(D) Liposomes generally have thinner membranes than polymersomes.
(E) Liposomes have higher lateral fluidity than polymersomes.
(F) Polymersomes have lower membrane permeability than liposomes. True - liposomes tend to have lower membrane permeability
(H) Polymersomes generally have higher physical and chemical stability versus liposomes.
(I) Polymersomes are biocompatible.
FALSE:
(B) Polymersomes have lower chemical versatility than liposomes. (polymersomes have higher chemical versatility - we can control properties of these polymers more readily; liposomes on the other hand are lipid molecules that can’t readily be modified to the degree of synthetic polymer)
(G) Liposomes can have molecules within both the hydrophobic membrane layer and the hydrophilic core, whereas polymersomes can only have molecules in the hydrophobic membrane layer. (false, polymersomes can also have molecules in the hydrophilic core)
(J) Liposomal membranes can be functionalized with molecules, whereas polymersome membranes cannot be functionalized with molecules. (false, polymersomes can be functionalized too)
- TRUE or FALSE? Hollow capsules formed by layer-by-layer technique can only be formed using synthetic polymers.
FALSE
You can use different ‘building blocks’.
- TRUE or FALSE? Hollow capsules formed by layer-by-layer technique can only be spherical in shape.
FALSE
If you change the shape of the initial core, you can change the shape of the resultant hollow capsules.
- One of the strategies used to develop artificial cell through a ‘bottom-up’ approach mentioned in the lecture was the use of “capsosomes”, which are in essence polymer capsules that contain liposomes.
(a) List ONE function of the polymer capsule component of the capsosome, in the context of its use as an artificial cell. (1 mark)
(b) List ONE function of the liposome component of the capsosome, in the context of its use as an artificial cell. (1 mark)
(c) TRUE or FALSE? The number of liposome layers in capsosomes is limited to one layer. (1 mark)
(a) Functions of polymer capsule component of the capsosome:
- Protection of the inner contents
- Allow permeability/transfer of molecules through the membranes
- Interaction with the surrounding molecules/environment
- Provide physical structure
- My answer: Functionalisation for cell-targeting
(b) Functions of the liposome component of the capsosome:
- Provide compartmentalized platform for enzymatic reactions (also provide some control over in and out)
- Mimic the functionality (i.e. biochemical/enzymatic reactions) of the normal cells
- (NB: Incorrect to put “endo/exocytosis”)
(c) FALSE:“The number of liposome layers in capsosomes is limited to one layer.”
- You can have multiple layers
- Liposomes are also not just limited to between layers, but also in the actual cavity of polymer capsules as well.
Why do you think inorganic NP are not generally explored in the context of artificial cells?
Better biocompatibility of organic v inorganic
Cells are vesicular, and its organelles are also vesicular, so imagine trying to use predominantly solid NP to mimic cells….
Cells also allow for permeability/transfer of molecules in and out (so artificial cells are often limited to polymeric shell-based structures, because allow for movement of in/out of molecules)
