Photo: Issy and Molly with Pawan Jolly in the department of electronic & electrical engineering
Within the department we were working with the Biosensor group. During our time there we were given lots of opportunities organised by our supervisor, Pawan Jolly, to experience and learn about research science. We visited chemistry, electronics and the nanofabrication labs and were kindly shown around by other post graduates who explained to us their work. It was very interesting to know how the researchers were working on the development of diagnostic tools for cancer diagnosis where one of the main focus was Prostate Cancer (PCa) diagnosis. It was also fascinating how the different groups around the Europe has come together on a common platform to work on the diagnosis of PCa and the network was called PROSENSE (http://www.prosense-itn.eu/).
Within the PROSENSE project, we individually fabricated DNA based biosensor for PCa, observed the absorbance of light by gold nanoparticles using spectrophotometer and used localised surface plasmon resonance technique (LSPR) among other things.
On the 24th Aug 2015, we started with preparation of buffers namely trisma base and sodium acetate and a bovine serum albumin (BSA) as a protein for our biosensor. The next day we adjusted the pH of the buffer using a pH meter, which detects the ion concentration of a solution, to raise or lower the pH of the buffers bases and acids were used.
As we were working with DNA, everything used must be extremely clean. So first we prepared our gold working electrodes by cleaning it using techniques like sonication, polishing with aluminium oxide in a figure of eight motion. As we wanted our surface to be very clean, electrochemical cleaning was performed in sulphuric acid as an electrolyte with a three electrode configuration using cyclic voltammetry. The silver reference electrode is kept in a salt bridge in order to protect it from the acid, the platinum counter electrode goes straight into the solution and the gold working electrode again goes into the solution. The electrode are connected up to a potentiostat that will cycle a voltage through them and causes oxidation and reduction of the gold surface and hence, removes dirt from the surface of the working electrode. In our experiment the next step was to fill caps with a light sensitive solution together with probe (receptors to capture DNA) and electrode was dipped in it, they were then left overnight.
Next we produced two separate electrolytes using potassium(II) hexacyanoferrate and potassium(III) hexacyanoferrate salts mixed with our prepared buffer solution. Then we placed our electrodes into the same buffer solution that was being used in our electrolytes. Firstly for each electrode we carried out cyclic voltammetry again. After the first run some of the electrodes had DNA attached and the others had a protein attached and depending on the length of time the electrodes were allowed to sit in the solution they should decrease the oxidation peaks as they interfere with the flow of electrons. We also carried out the programme electrochemical impedance spectroscopy (EIS) which measures the amount of resistance of the system this is affected by not only the surface modification because of binding but also the ion concentration in the electrolyte. With capture of DNA, we observed the increase in resistance and also the decrease in the oxidation peaks in the CV. By the end, we successfully developed our own DNA based biosensor for detection of circulating DNA in blood for Prostate cancer.
All in all, we had a great time and can’t thank enough everyone who took the time to talk to us about their respective fields. Most of all a massive thanks to Pawan, for having the patience of a saint and showing us the “realities” of research in the field of science.