By Mark Bondin (B.Sc. Pharmaceutical Studies 3rd Year)
Medicines are our friends! They are there at our side when we are sick and to help us get better again. But it isn’t as simple as it seems. When one takes a dose of medicine and it starts to circulate in the body, the rate with which it is going to be eliminated is slightly different in every patient.
Why is this you may ask?
Well, every individual is unique with his/her own special genetic make-up which ultimately translates to the expression of proteins in the body. The idea is that a slightly different gene will encode for the expression of an enzyme which is not perfectly similar with that which other patients have. Consequently, a different rate of action of these enzymes is observed - it can either work too fast or else work too slowly. If the enzyme works too fast then the enzyme could be metabolised (deactivated) before it has enough time to induce an effect in the body. If it was to be broken down too slowly, then its effect in the body could be prolonged and also result in accumulation of the drug in the body - both of which are undesired effects. Therefore we can say that we have a dosing range for our drug, within which we can safely administer the drug without worrying of side-effects relating to drug concentration.
A way of how we can keep this in check is by constantly monitoring the drug concentration in the body as it is circulating around in the blood. This enables health professionals to decide whether it would be best to increase or decrease the dose for that particular medicine. But it isn’t as easy as it sounds as the procedures which are in use today are very expensive and tend to take a long time for the results to be produced.
Scientists at the EPFL (École Polytechnique Fédérale de Lausanne) in Switzerland have come up with an ingenious way of how to monitor the concentration of drugs and it involves the use of light. The process involves administering Luminescent Proteins to the patient before the drug is administered and a single drop of blood is used to check for the colour changes which represent the relative concentration of drug present.
This class of bio-sensors is referred to as LUCiferase-based Indicators of Drugs or LUCID’s and has been tested successfully with 6 different types of molecules: 3 immunosuppressants, 1 anti-epileptic, 1 antiarrhythmic and 1 anticancer molecule. This process has also been proven to be effective in in-vitro (laboratory) testing and the anti-cancer molecule was effectively tested on human blood samples. With all of the molecules mentioned above, a stable signal was given off by the LUCID molecule for 10 minutes.
The molecule complex is made up of 4 primary components:
· A Receptor protein which binds the molecules of the target drug,
· A small molecule which is similar to the target drug which can bind to the target receptor,
· A light emitting enzyme called Luciferase,
· A fluorophore molecule which can modify the colour of the Luciferase light when it comes close to it.
When there is no drug around it, the receptor and the small drug-like molecule bind together. This will result in the fluorophore binding very close to the Luciferase molecule, thus resulting in the emission of a red light. When the actual molecule is present, it tends to bind to the receptor more efficiently than the previously mentioned molecule and thus pushes the drug-like molecule away. The conformational change which occurs here will cause the fluorophore molecule to be slightly displaced and thus the colour will be observed to change from red to blue. Depending on the relative amount of the drug which is present the blue colour will intensify to give a more intense shade of blue.
How is the procedure conducted?
1) The patient initially takes the LUCID molecule and then follows up with the intake of the medicine.
2) After a pre-determined time has passed, a single drop of blood is taken from the patient by using a finger-prick method. Note that the amount of time required to wait for the taking of the blood sample is different for each drug depending on the route through which it was administered. For example a tablet takes a longer time to get into the blood circulation than if it were to be given via intra-venous administration directly into the blood.
3) The drop of blood is placed on a piece of paper and is inserted in a dark box and a traditional point-and-shoot digital camera is used to take a picture of the drop of blood through a slit which is cut in the dark box.
4) The picture is then analysed via a colour measuring software to generate an average measurement, based on the intensity of the colour.
5) The measurement acquired is then compared to a standard drug-concentration curve, and the relative drug concentration is determined.
This technique proves to be very simple, cheap and effective when compared to the drug monitoring techniques which are currently being used today. It is also advantageous as a technique as it can be done by the patient himself in the comfort of his home, without consuming too much time.
Link to video put up by the EPFL team to explain the concept and practicality of procedure: https://www.youtube.com/watch?v=8sRY4wO36Sc
1) Griss R, Schena A, et.al. Bioluminescent sensor proteins for point-of-care therapeutic drug monitoring. Nature Chemical Biology. [Internet] July 2014. [Cited 25th October 2014]; Volume 10, pages: 598-603. Available at: