Directed self-assembly

Question 1

Give 3 types of strong interactions/bonds

Answer 1

Covalent bonding, ionic bonding, metallic bonding

Question 2

Give 3 types of weak interactions

Answer 2

Van der Waals forces
H-bonding
Pi-pi-stacking
London dispersion forces

Question 3

What is the difference between strong and weak interactions?

Answer 3

The strong interaction they share electrons and orbitals, while the weak interactions are based on dipole interactions

Question 4

What is self-assembly and what is directed self assembly?

Answer 4

Self-assembly is the process by which nanoparticles organize into ordered structures

This organization can be directed, where the system is ‘helped’ into assembly. This can be done with templates or chemical agents. The direction can be done externally/physically or internally/chemically

Question 5

List 3 methods for externally directed self-assembly

Answer 5

Electrical field
Magnetic field
Templates
Flow

Question 6

List 3 methods for internally directed self-assembly

Answer 6

Temperature
pH
metal ions
redox
solvent exchange - polarity

Question 7

Can you give some examples of how self-assembly can be used to design nanostructures for life sciences applications?

Answer 7

Micelles, liposomes produced by solvent exchange

Question 8

Explain how self-assembled peptide amphiphiles are formed and how they can be used in life sciences?

Answer 8

Self assembly, core principles as micelles. Need molecule amphiphilic, polar and non-polar part

Critical concentration - increase concentration above threshold –> self assemble

Water solution with molecules polar head, hydrophobic tail - molecules while orient. Head outside, tails in the core. Continue to increase c, change packing - may change the shape.

Structure is affected by pH and charge from the different regions 1-4 affect, bulky group of peptide sequence near tail –> helical structure

Question 9

What are the different structural components of amphiphilic peptide monomers? Explain the role of 4 different regions in such structures

Answer 9

1. Long hydrophobic tail – drive the self-assembly
2. Short peptide sequence – prevent spherical structures with H-bonds and β-sheets. Can also affect shape –> bulky groups;)
3. Charged AA (2-3) (pH/ionic strength dependent) – in situ switch used for drug delivery and controls solubility.
4. Bioactive/biosignalling group (exposed part) – can signal or attach to cells.

Question 10

Give an example of structural variation of amphiphilic peptide monomers that produces helical structures as opposed to regular rod-like structures

Answer 10

incoproration of bulky amino acid groups in region 2 –> formation of twisted ribbons which make helical structures upon storage, in the absence of other stimuli.

Question 11

What is the function of region 4 in self-assembled amphiphilic peptide structures? Provide some examples of how its properties can be used for different applications

Answer 11

Region 4 can be designed in a way that promotes mineralization
- Can bind to stuff,
- design for bone regeneration. Template for bone regeneration

Question 12

Explain directed self-assembly using the example of mesoporous silica materials? What is controlling the geometry and size of the pores in mesoporous silica.

Answer 12

A number of factors influence the properties of the formed silica:
* Source of silica
* Type of surfactant
* pH and composition of the reaction mixture
* Temperature
* Time
* Calcination conditions