NANOPARTICLES IN DIAGNOSIS AND IMAGING Flashcards
What molecule is used in PET scans?
2-deoxy-2-(18F)fluoro-D-glucose [FDG]
What molecule is used in MRI scan?
Chelated gadolinium
What molecule is used in Computer Tomography (CT) ?
Iodinated small molecules
Why nanoparticles used in imaging?
- Nanoparticles also have a high avidity as they can be coated with multiple copies of ligands (due to high surface area) which will allow multiple binding interactions with cellular target moieties - increasing their association constant by 4 to 5 orders of magnitude
This allows more np to accumulate at the site
Increases signal to noise ratio - allows cancerous tissues to be better highlighted
- Most nanoparticle imaging agents are also larger than 10 nm and are therefore not typically cleared renally from the circulation;
- Allows them to have longer circulation times when compared with small molecules (i.e. after days vs minutes)
- Useful as it permits repeated imaging without the need for further NP administration
What nanoparticles are used in pregnancy testing?
GOLD (AU) NANOPARTICLES
- Colloidal suspension of submicrometre-size NPs of gold in a fluid, usually water
- An intense red colour (f particles less than 100nm) or
- Blue/purple (for larger particle than a 100nm)
How does a pregnancy test work?
In pregnancy test:
- The test’s active ingredient
- Gold NP appear red because of the way they interact with light and size
o Give the indicator strip its colour
Monoclonal antibodies
- Designed to identify hCG
- Visualising it with gold NP. They attach themselves to the gold if hCG is present
- Move up the strip until they rerach the indicator
Put URINE in
HCG
Lots of antibodies – different coloured
In control line (should always work) – should always see this line. Brown antibodies – they are detecting little bit of orange antibody with gold NP
The urine with HCG, HCG binds only of the top of the orange antibody which then flows and only recognises brown antibodies
Still has gold on it
Able to see the pink colour due to gold on surface
HCG binding to orange antibodies with gold on them, and then bind to purple antibodies which only recognises HCG. And still have gold to visualise it.
If you don’t have HCG, won’t get binding process. = Not pregnant
Positive – hormone will bind to purple and then can see pink.
What are 2 nanomaterials used in MRI?
- Small nanomaterials consisting of iron oxide core crystals surrounded by a stabilising polymer or polysaccharide shell (something on surface to stabilise them – if remove they will stabilise)
- 2 most commonly studied iron oxides have been magnetite (Fe3O4) and maghemite (g-Fe2O3)
What are MRI contrast agents?
- MRI contrast agents are a group of contrast media used to improve the visibility of internal body structures in magnetic resonance imaging (MRI)
The most commonly used compounds for contrast enhancement are gadolinium-based
Such MRI contrast agents shorten the relaxation times of atoms within body tissues following oral or intravenous administration
Describe the use of SPIONS AS CONTRAST AGENTS FOR MRI OF INFECTION AND INFLAMMATION
- Phagocytosis by macrophages of injected SPIONs Hypo-intensity of macrophage-infiltrated tissues in contrast-enhanced MR images (can look at tissues infiltrates with macrophages)
- SPIONs as contrast agents are therefore useful for the in vivo MRI detection of macrophage infiltration
- This technique has been used to identify active infection in patients with septic arthritis and osteomyelitis
What is SPECT/CT?
-Single photon emission computed tomography (SPECT- CT) is where two different types of scans are taken and the images or pictures from each are fused or merged together
- SPECT is a non-invasive nuclear imaging test
o It uses radioactive tracers that are injected into the blood. (Uses strong radiation) - The fused scan can
provide more precise information about how different parts of the body function and more clearly identify problems such as tumours (lumps) or Alzheimer’s disease.
What are quantum dots?
- Tiny particles or nanocrystals of a semiconducting material with diameters in the range of 2-10 nanometers (10-50 atoms)
- Cadmium selenide
- Fluorescent nanoparticles
Colour light emitted is directly related to its size - Smaller dots appear blue larger ones more red
How is quantum dots used in cancer diagnosis?
- Sentinel lymph node (SLN) mapping is an important cancer surgery (cancer cells go into lymph nodes).
o A sentinel lymph node is defined as the which cancer cells are most likely to spread from a primary tumour. If patient signs of metastasis (early) look at SLN.
Describe MULTISPECTRAL OPTOACOUSTIC TOMOGRAPHY (MSOT)
- new technique for whole-body imaging of bio-chemical markers in small animals
- MSOT illuminates tissue with light pulses at multiple wavelengths and detects the acoustic waves (sound waves generated) generated by the thermelastic expansion of the environment surrounding by absorbing molecules. (need to know that you have light and you get some sound)
o Acoustic waves are a type of longitudinal waves that propagate by means of adiabatic compression and decompression
o Adiabatic: without transfer of heat or matter
o Acoustic: relating to sound or the sense of hearing
- allows high resolution imaging of photo-absorbers deep within tissue, beyond the classical depth (deep within a tissue) and resolution limitations of conventional optical imaging
Gold Nanoparticles
- Due to plasmon resonance, gold nanoparticles exhibit strong optoacoustic responses (due to plasmon resilience due to absorbance of light)
o Plasmons are the oscillations of free electrons that are the consequence of the formation of an electromagnetic waves
o Main issue: Due to the typically long retention times in tissues. Want them to be excreted from body aswell!
What is Indocyanine Green (ICG)?
is a cyanine dye used in medical diagnostics
- It is used for determining cardiac output, hepatic function and live blood flow, and for ophthalmic angiography
