"This system is a cheap, effective solution for customising drug dosage in patients across a whole array of diseases," said Rudolf Griss from Ecole Polytechnique Federale de Lausanne in Switzerland.
Monitoring the drug concentration in patients is critical for effective treatment, especially in cases of cancer, heart disease, epilepsy and immunosuppression after organ transplants.
However, current methods are expensive, time-consuming and require dedicated personnel and infrastructure away from the patient.
The new bio sensor molecule can quickly and accurately measure drug concentration in a patient's system without requiring anything more complicated than a regular digital camera.
The molecule is the result of innovative protein engineering and organic chemistry, and has been shown to work on a range of common drugs for cancer, epilepsy and immunosuppression.
The sensor molecule works by binding the drug circulating in the patient's bloodstream and changing colour accordingly.
The doctor or the patient can record the signal very easily by putting a drop of sample like blood onto a piece of paper, placing it in a dark box and photographing it with a conventional camera.
The photograph can then be analysed by colour-measuring software to generate an average measurement.
The findings appeared in the journal Nature Chemical Biology.