What are the similarities and differences between magnetic, gold and quantum dot nanoparticles?
These particles are all classed as inorganic particles, which can all be utilised in biomedical applications. They differ in terms of their inherent material and size dependent physiochemical properties, for example, their optical and magnetic properties.
What are the main bioapplications that nanoparticles are used for?
We know that nanoparticles less than several hundred nm can easily enter cells (with less than 50 nm entering most cells), whilst those under 20 nm can move through the blood vessels and permeate adjacent tissue, and also cross the blood brain barrier.
Using this knowledge, nanotechnology has now reached the stage whereby we can create and design nanoparticles for use in biomedicine, in particular diagnostics (imaging) and therapeutic delivery (eg. drug/gene delivery).
What are the key considerations when designing a nanoparticle-peptide conjugate to target a cell type?
When designing nanoparticles for biomedical purposes, the particle needs to be inert, stable in biological fluids and easy to functionalise.
If you are considering targeting a specific cell or tissue type in the body, you need to deliberate using a particle ligand or conjugate, which will recognise a receptor on that cell surface and bind to it.
Chemists are currently developing excellent techniques to attach multiple conjugates onto the particle surface, which allows this multifunctional approach.
How do you test whether the nanoparticle-peptide conjugates target the correct cell type in vitro?
Simply incubating your particles with a range of cell types in culture, including your target cells, can help determine the efficacy of targeting.
Subsequent analysis of particle uptake into cells will verify if you have been successful with your targeting.
What is the difference between a 2D and 3D culture system? Which more accurately reflects the in vivo situation?
Traditional 2D, or monolayer cell culture is an excellent tool for simple studies and provides us with a wealth of information regarding cell interactions with materials.
However cells in the body reside in a dynamic 3D environment, whereby they synthesise and surround themselves with an extracellular matrix (or tissue). Therefore, cells cultured in 3D systems better reflect the in vivo environment.
Please can you outline the project you are currently working on which focuses on the delivery of siRNA loaded nanoparticles for cancer cell treatments?
We are part of a larger EU grant working with colleagues in Spain, Portugal, Germany and Italy. The project is focused on using gold nanoparticles to delivery therapeutic fragments of siRNA to silence a specific gene in cancer cells.
The target gene, c-myc, is a transcription factor which, along with its other roles, drives forwards cell proliferation. The gene is up-regulated in cancer cells, allowing the cells to rapidly proliferate and grow.
If we can silence, or knock down, this gene, then it follows that the cancer cells will lose the ability to grow.
The project has been very successful, following nanoparticle synthesis by Dr. Jesus de la Fuente in Zaragoza (Spain), we have observed gene knockdown in several caner cell lines at the gene, protein and gross cell proliferation levels, indicating the promise of such nanoparticle tools in therapeutics.
How do you make sure that the siRNA locates near the nucleus?
The gold nanoparticles used are multifunctional in that they have several conjugates attached. The siRNA is thiolated, so can bond directly to the gold core, in addition there is PEG (polyethylene glycol) to both passivate the particles in biological media and to act as a platform for further conjugate attachment.
A further conjugate used was tat peptide, which is a short amino acid borrowed from the HIV-1 virus, which allows cell entry and nuclear localisation – helping to act essentially as a taxi to ferry the particles into the cell and locate to near the nucleus (which is where the intracellular machinery ‘in charge’ of silencing is found).
Could you please explain the other project that you are currently working on which is using magnetic fields to augment the delivery of magnetic nanoparticles into 3D tissue equivalents?
The use of magnetic fields to pull magnetic nanoparticles into cells has been used for some years now, and is termed magnetofection. We routinely use this method to increase cell delivery of magnetic particles.
However we are also interested in the notion of magnetic targeting in vivo, using an external magnetic field (eg. the pulling of drug loaded magnetic particles injected into the blood stream to a site in the body using a magnet).
Therefore, we have also been using magnetic fields with 3D cell cultures as simple tissue equivalent models to determine if a magnetic field can be used to help pull particles into tissues.
We have shown that small fields can significantly increase the depth of penetration into a ‘tissue’, illustrating the potential in vivo.
What further research plans do you have for the bioapplications of nanoparticles?
We are using nanoparticles in many different areas. With regards to magnetic nanoparticles, following established magnetofection techniques (ie. increased cell loading in monolayer), we are using magnetic fields to move the particle-loaded cells in 2D and 3D.
This allows us to cluster the cells in distinct groups, for example using mesenchymal stem cells (MSCs) and developing mimic MSC niche model systems.
We are also involved in using magnetic nanoparticles for cancer hyperthermia treatment studies in 3D culture, whereby we can test the potential of particle loaded cells to be heated via exposure to an alternating magnetic field.
This work is based on the fact that cancer cells are susceptible to temperatures above 40oC, so if we can use magnetic particles as nanoscale heaters inside cancer cells, we can induce cell death.
With regards to gold nanoparticles, we are continuing to look at siRNA in cancer treatment and extend out knowledge as to how and where the events are happening inside the cell.
In addition, we are also looking at silencing specific microRNAs in MSCs, which we have shown are critical for differentiation, with a view to artificially controlling differentiation via nanoparticle delivery.
What impact do you think nanoparticles will have on medicine in the future?
I think that nanoparticles have great potential in nanomedicine. A great deal of this is due to the clever functionalisation and synthesis our colleagues in chemistry can do, which enables us cell biologists to use particles as tools to target and control cell behaviour.
They are already used for imaging techniques, and I believe they have a great future in therapeutics.
Where can readers find more information on your research?
On our Centre for Cell Engineering web pages at Glasgow University (http://www.gla.ac.uk/researchinstitutes/biology/research/cellengineering/#d.en.182497) or via our science publications.
About Dr Catherine Berry
Dr. Catherine Berry is a lecturer in Cell Engineering in the Institute of Molecular, Cell and Systems Biology at the Univeristy of Glasgow.
Since completion of her Smith & Nephew supported PhD at the IRC in Biomedical Materials in London, she moved to Glasgow in 2001 as a PDRA concentrating on the interaction of inorganic nanoparticles with cells in monolayer and 3D culture models.
In 2006 she was awarded a Dorothy Hodgkin Royal Society fellowship focusing on gold, magnetic and quantum dot nanoparticle targeting in vitro followed by her lectureship in 2012, working part time with three small children.
During this time she has built up strong international academic links and also maintains several contacts in national and international industries.
Dr. Berry has a successful publication record with both her academic and industrial collaborators (majority as lead author or group leader; H-index 22) and throughly enjoys the interdiscplinary environment of her work.