the lab

At the 254th ACS conference in Washington DC

This is a guest post by Sumaira Ashraf.

Last month, I got the opportunity to attend and present my work at the 254th ACS conference held in Washington DC. The session was organized by Raphaël Lévy, Niveen Khashab, and Zhihong Nie. I presented preliminary data regarding my work on multimodal imaging probes for stem cell tracking. I enjoyed the conference but was disappointed by some of the talks. Many speakers  exaggerate their results to impress their audience and hype the worth of their work. I did wonder if it is productive to point out mistakes as no one seems interested in correcting them, but, instead, they might become your lifelong rivals. Here is an example. I know from practical experience that liposomes loaded with small molecule dyes cannot be used as long-term imaging modality because within 24 hrs of loading ~99% signal intensity is lost due to leakage from the liposomal cavity. But speakers presented quantitative imaging data based on these approaches. I wanted to point this problem out but I did not want to get involved in never ending discussion where no one will be ready to admit their errors. Eventually, I did not say anything.

Of course, my own work with polylelectrolyte capsules has some limitations as well: while they are good candidates for protecting imaging probes from intracellular degradation and intracellular species from potentially toxic probes, the limit of detection depends on the amount of contrast agent delivered which still remain low. In my current experiments, I need to overcome this limitation by modifying or choosing an alternate approach.

The Kavli lectures were really very informative… but I could not attend the full talk of the 2nd speaker because the air conditioning was set at a temperature so low that I could not tolerate it: I was forced to leave this interesting lecture. The industry exhibition downstairs the convention centre was massive and fun. I particularly liked the Bruker stall which had good explanation of NMR, mass spectrometers, etc., (covering theoretical and experimental data evaluation). There were other advantages to the visit of the exhibition: chocolates, bags, T- shirts, ice cream (prepared in liquid nitrogen within 3 minutes), lunch, free L’Oréal products, and lucky draw (especially when you win; I won a Swag Bag of merchandise from the ACS Store worth USD$75.00). I was lucky to see the solar eclipse through the cover glasses provided by the conference.

I missed the opportunity to visit the reflecting pool near Lincoln memorial and some interesting museums due to time limitation. I am looking forward to some forthcoming opportunity to see them.

I came back with some thoughts to work with new nanocomposites (recent work presented in one of the talk by Amit Joshi; based on doping materials rather than combining them inside big capsules or attaching via linkers) for multimodal imaging which might have potential to overcome the flaws associated with above mentioned materials. But I need to try… without trying one cannot be sure of anything.

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Gold nanorods to shine light on the fate of implanted stem cells

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Joan Comenge

This is a guest post by Joan Comenge

Our work regarding the use of gold nanorods as contrast agents for photoacoustic tracking of stem cells has been just published (or here*). You can find all the technical details of the work there, so I will try to explain here the work for the readers who are not very familiar with our field.

It is important to have the appropriate tools to evaluate safety and efficacy of regenerative medicine therapies in preclinical models before they can be translated to the clinics. This is why there is an interest in developing new imaging technologies that enable real time cell tracking with improved sensitivity and/or resolution. This work is our contribution to this field.

To distinguish therapeutic cells from the patient’s own cells (or here from the mouse’s own cell),  the therapeutic cells have to be labelled before they are implanted. It is well known, that biological tissue is more transparent to some regions of the light spectrum than others. This fact is very easy to try at home (or at your favourite club): if you put your hand under a green light, no light will go through it, whilst doing the same under a red light the result will be very different. That means that red light is less absorbed by our body. Near infrared light is even less absorbed and this is why this region of the spectrum is ideal for in vivo imaging. Therefore, we made our cells to absorb strongly in the near infrared so we can easily distinguish them.

Gold nanoparticles of different sizes and shapes (synthesis and picture by Joan Comenge).

Gold nanoparticles of different sizes and shapes (synthesis and picture by Joan Comenge).

To do this, we labelled cells with gold nanoparticles. Interestingly, the way gold nanoparticles interact with light depends on how their electrons oscillate. That means that size and shape of the nanoparticles determine their optical properties, and this is one of the reasons why we love to make different shapes of nanoparticles. In particular, gold nanorods strongly absorb in the near infrared and they are ideal contrast agents for in vivo imaging.

Capture

Figure reproduced from: The production of sound by radiant energy; Science 28 May 1881; DOI: 10.1126/science.os-2.49.242

We have now cells that interact with light in a different way than the tissue. The problem is that light is scattered by tissue, so resolution is rapidly lost as soon as you try to image depths beyond 1 mm. Obviously, this is not the best for in vivo imaging. Luckily for us, Alexander Graham Bell realised 130 years ago that matter emits sounds when is irradiated by a pulsed light. This is known as the photoacoustic effect and it has been exploited recently for bioimaging. Photoacoustic imaging combines the advantages of optical imaging (sensitivity, real-time acquisition, molecular imaging) and the good resolution of ultrasound imaging because ultrasounds (or phonons), contrarily to photons, are not scattered by biological tissue.
GNR-35.2Si3 in cells_16

Silica-coated gold nanorods inside cells

To optimise the performance of our gold nanorods, we coated them with silica. Silica is glass and therefore it protects the gold core without interfering with its optical properties. This protection is required to maintain gold nanorods isolated inside cells since nanorods are entrapped in intracellular vesicles, where they are very packed. The absence of a protective coating ultimately would result in a broader and less intense absorbance band, which would be translated to a less intense photoacoustic signal and consequently a lower sensitivity in cell detection. This of special importance in our system, a photoacoustic imaging system developed by iThera Medical which uses a  multiwavelength excitation to later deconvolute the spectral information of the image to find your components of interest. Thus, narrow absorption bands helps to improve the detection sensitivity even further. With this we demonstrated that we were able to monitor a few thousand nanorods labelled-cells with a very good 3D spatial resolution for 15 days. This allowed for example to see how a cell cluster changed with time, see how it grows or which regions of the cell cluster shows the highest cell density. In addition, this work opens the door to new opportunities such as  multilabelling using gold nanorods of different sizes and consequently different optical properties to observe simultaneously different type of cells. We also believe that not only stem cell therapies, but also other fields that are interested in monitoring cells such as cancer biology or immunology can benefit from the advances described in our work.

You can find the original publication here (or here*).
All the datasets are available via Figshare.

This work was supported by the UK Regenerative Medicine Platform Safety and efficacy, focusing on imaging technologies. Joan Comenge was funded by the People Programme (Marie Curie Actions) of the European Union’s Seventh Framework Programme. The in vivo imaging was done in the Centre for Preclinical Imaging, the Electron Microscopy in the Biomedical EM unit and the Optical Microscopy in the Centre for Cell Imaging.

* the alternative link is to 50 free e-prints; the link will be removed once the paper is fully open access (in a couple of days).

day3_200k

Cluster of gold nanorod-labelled cells imaged by photoacoustic imaging three days after implantation in mice.

Looking for a beautiful PhD?

Scientific research can be dispiriting at times, when experiments won’t work and even the coffee machine decides not to cooperate. And I can’t promise such times won’t happen in this project ever.

But, in addition to great science and collaboration with an active and interesting industrial partner, this PhD is about beautiful images (full of informative scientific content that we will exploit of course!). In preliminary work which form the basis of this collaborative project, Aurelia Bioscience Matt Vassey prepared samples which were imaged by Marie Held with our light sheet microscope in the Centre for Cell Imaging:

MED-72-T-P-stack_MIP

Human-induced Pluripotent Stem Cells growing on an electrospun scaffold. Sample prepared by Matt Vassey (Aurelia Bioscience Ltd, Nottingham), imaging by Marie Held (Institute of Integrative Biology, Liverpool)

You can find the formal advert here:

Our understanding of the biology of the cell has been informed by decades of studies of cells growing in two-dimensional cell layers. Real biological systems however are 3-dimensional and it has become clear that there are significant differences in terms of gene expression and response to treatments. This project explores new opportunities for growing and imaging cells in 3 dimensions and their impact on the biology of the cell. It offers an array of opportunities to the student for scientific development and close collaboration between an academic and industrial partnership. The extensive multidisciplinary nature of the project would involve interaction with biologists, materials scientists, biophysicists, pharmacologists and industrial biotechnologists and would suit an ambitious applicant with a strong interest in technology development and biotechnology.

At this stage, you should, either apply by sending me an email explaining why you are interested with your CV attached (yes, I know it is obvious, but still), or, help me find a lucky enthusiastic student for this project! [unfortunately, nationality/residency funding conditions apply]. Deadline for application is 12/02, however, apply as soon as possible!

Other things we do in the group here.

Supervision and Lab philosophy

Two interesting links for members of the team and beyond.

First, an inspiring lab philosophy, via Twitter

 

Second, some thoughts on student supervision by Dr. K.

Last week two ladies arrived in our lab, let’s call them X and Y. Two weeks before that a male student arrived as well, Mr Z. Somehow, they all ended up under my supervision.

Read on.

Impressions from a French Symposium

This is a guest post by Elena Colangelo, PhD student in the group.
One week ago I was leaving for Strasbourg, for the E-MRS Spring Meeting. I started my PhD in October and I was curious to discover what a conference looks like.
In particular two aspects of this French week have impressed me.

The symposium Q

Lara Bogart and Fred Currell (Queen University Belfast) in Strasbourg, May 2013

Lara Bogart and Fred Currell (Queen University Belfast) in Strasbourg, May 2013

The symposia (literally “to drink together”) were social events of great importance for Greeks and Romans. They used to debate on a variety of topics while eating and drinking; the discussion was guided by the symposiarch who had also to decide how strong the wine served would have been accordingly to the depth of the theme discussed. During the symposia new friendships were built on common interests and enjoyable time spent together. I found that the spirit and the organization of the symposium Q “Bionanomaterials for imaging, sensing and actuating” in the Strasbourg conference was pretty much the same. The talks have been enjoyable and sometimes the discussions have been really exciting. At the same time the atmosphere on Wednesday evening was not far from Alcaeus’s drinking poem (fr. 346):

Let’s drink! Why are we waiting for the lamps? Only an inch of daylight left.
Lift down the large cups, my friends, the painted ones;
for wine was given to men by the son of Semele and Zeus
to help them forget their troubles. Mix one part of water to two of wine,
pour it in up to the brim, and let one cup push the other along…

Leaving Italy

After my graduation I decided to leave Italy because I was seeing the problems in the academic world as irremediable and irreversible. I have been more than happy to meet at the conference so many Italian researchers that are working there. They were complaining about issues they face because of the stuck situation, but at the same time they were not thinking that it is yet the time to give up and to move somewhere else. From The Moon and the Bonfires by Cesare Pavese:

One needs a town, if only for the pleasure of leaving it. A town means not being alone, knowing that in the people, the trees, the soil, there is something of yourself, that even when you’re not there it stays and waits for you. But it isn’t easy to live there and not be restless.

Elena, Lara and Dan in La Petite France, Strasbourg, May 2013

Elena, Lara and Dan in La Petite France, Strasbourg, May 2013