Define nanomaterial.
They are structures that are used at the nanoscale (<100nm dimension or diameter)
Why are nanomaterials so desirable?
– Include nanofibres, nanotubes as well as spherical structures with a diameter of <100nm.
– Their small size allows them to be engineered to display desirable characteristics:-
o High strength, reactivity, conductivity
o High surface area allows them to be very reactive.
o Small size allows them to be effective in entering organs
What are the uses of engineered nanomaterials?
o Medicine -- Implants and prosthetics -- Antimicrobial properties -- Drug carriers/drug deliver -- Tissue engineering -- Molecular imaging o Antibacterial sprays o Cosmetics o Clothing o Food – e.g. low calorie food products. Can be dangerous as a lot of these haven’t been tested to see if they can cause harm. o Structural engineering o Construction o Dental o Air conditioners o Sport goods
Describe the general features of the fullerenes.
- Fullerene development derives from discovery of the bucky ball (C60), a spherical molecule of 60 carbon atoms that forms a hollow sphere 1nm in diameter.
- Fullerenes were then discovered as a family of similar spherical structures with differences in their size (i.e. number of atoms).
- Third allotropic form of carbon – discovered in 1985.
- Fullerenes are non-toxic and can be functionalised to make them water-soluble.
Describe the features of carbon nanotubes. How can they be functionalised?
– Rolled up sheets of carbon atoms that naturally occur in soot.
– Discovered in 1991 – usually few nm in diameter but vary greatly in their length.
– Can be single or multi walled. Can exist as tubes, wires and fibres.
– Stronger than any material in the universe.
– Properties include:
• High tensile strength
• Electrical and heat conductivity
• Ductility
• Chemical inactivity
– They are simple to chemically functionalise –
• Create abrasions in their walls (by exposing to damage – usually corrosion) that breaks some of the C=C bonds and then attach various functional groups.
• These groups can be antibodies and cytoxic agents for cancer therapy, quantum dots to highlight the cancer cells. The CNT will enter cell and deliver the cytotoxic agent.
• Temperature sensors can also be used to detect the cancer cells.
Describe the features of nanosilver. What are its dangers?
- Very portent antimicrobial agent.
- Ancient nanomaterial – Hippocrates noticed healing properties of silver and it was used to store water, wine and liquids to preserve them.
- In early 20th century it was used in creams as an antibiotic and used in dressings for burns etc.
- It adsorbs to biomolecules – so it can be used to remove environmental waste, blood, and in mucosal membranes.
- Now used in wound dressings, tubing, face masks, clothes, household goods etc.
– However there are dangers -
• Silver can accumulate in body, mainly in skin leading to particles darkening in sunlight (as they are photo-sensitive) leading to grey discoloration of the skin known as agyria.
• This is irreversible and the only way to prevent is to avoid the sunlight.
Describe the features of nanogold.
- Uses – electromagnetics, drug delivery and early diagnosis of cancer, environmental detoxification and water purification, visual properties – electron microscopy
- Colour emitted depends on size of the gold – smaller particles are more red, while larger are more blue/purple.
- A smaller gold particle aligns closer with the cell – better for drug delivery.
Describe the general features of quantum dots.
- Nanoscale crystals of semiconductor material that fluoresce when excited by light. Usually cadmium (the semi-conductor) that is coated in zinc.
- The size of the QD will determine the wavelength they emit light.
- So a different size will release different colour- smaller are blue, larger are red.
- Mulitocolor coding can be carried out by incorporating QDs of different sizes into microbeads. 6 different colours and 10 intensities means up to 1 million nucleic acid/protein sequences can be coded.
- QDs are highly uniform and reproducible.
- However cadmium limits their use as it can be harmful (?)
- Used in cellular imaging, drug delivery, LEDs, lasers.
- Can be functionalised – DNA, peptides, can be modified to hydrophobic/hydrophilic.
Describe the process of atomic force microscopy. What are its uses and disadvantages?
- It images cell topography by scanning a probe against surface to identify its contours.
- The interaction between needle and surface is measured and this data is then used to produce an image.
- Cantilever – usually a silica beam 100-500um in length and 0,5um in diameter. Its angle determines the resolution of the image produces
o Uses
- Can be used to study a wide range of molecules and cells in native environment and processes unlike EM which can only image dead cells.
- Examine specimens in aqueous solutions – determine mutant types from looking at structural differences at the surface
- Bacteria imaging
However it can damage eukaryotic cells as tip is rigid and can kill live cells.
Describe the features of scanning ion conductance microscopy. What are its advantages and disadvantages?
- Developed in late 80s – can be used to image in vitro and in vivo live cells at the nanoscale.
- Images non-conductive material bathed in electrolyte. It has an electrically charged nanopipette that is filled with electrolyte of an opposite charge.
- As the pipette is lowered to surface of material, the ion conductance will generally fall as there is less space for the ions to flow.
- The tip rolls over the cell surface and current changes will feedback to computer to give the height values to give you the topopgraphy of structural surface.
- The tip is kept a distance from damaging the cell.
o Advantages
- Scan surfaces of live cells with high resolution
- Can study changes of topography that are occurring during cell’s life
- Measure cell volume and height
- Study dynamics of cell surface structures – e.g. phagocytosis – real time processes such as distribution of viral particles on cell surface.
o Disadvantages
– Limited to relatively flat surfaces since the probe rolls across the specimen.
Describe the features of Hopping probe ion conductance microscopy.
- Variation of SICM – the reference current is first measured while the probe is away from the specimen.
- Then the pipette approaches until the current is reduced by a predefined amount which is recorded as the height of the sample at this imaging point.
- Allows non-flat surfaces to be examined as it doesn’t roll around surface like in SICM.
