The University Jaume I (UJI) has patented a new fluorescent chemical sensor that is capable of detecting citric acid at low concentrations more rapidly and cheaply than the current optical sensors.
The molecule, which has been designed by the Sensors and Supramolecular Photochemistry research group at the UJI, has potential applications in the food and pharmaceutical industries, as well as for diagnosing certain diseases.
The molecule works as a light indicator and emits higher or lower intensity fluorescent light depending on the amount of citric acid present in the sample. In other words, the less citric acid there is present, the less light will be produced, and vice versa. One of the main advantages of the newly designed sensor is its high sensitivity, which allows one citric acid molecule to be detected among millions of water molecules through fluorescence. The systems used today to optically analyse citric acid (the most important being the citrate lyase enzymatic method) are between one hundred and one thousand times less sensitive.
Another advantage of the sensor patented by the UJI is its increased fluorescence intensity. “With the complexes developed it is possible to achieve gains of up to 1500% in fluorescence intensity in the presence of citrate. This implies multiplying the signal by a factor of 15, which results in very reliable measurements,” explains Francisco Galindo, co-author of the research study.
Furthermore, the molecules designed react with the sample immediately, while in the case of the traditional citrate lyase enzyme method it is necessary to wait up to 30 minutes to obtain the results. “This advantage in the data acquisition speed can be very important when it comes to developing automatic real-time measurement systems, such as those required in food quality control to detect possible defects in the manufacturing quality of a given product, or in urgent medical urine or blood tests for the rapid diagnosis of diseases associated with the presence of citric acid,” the researchers point out.
In fact, the food and pharmaceutical sectors are the main targets of the applications offered by the new fluorescent sensor developed at the UJI. Citric acid is an important component in numerous pharmaceutical preparations, foods, drinks and various industrial products. For example, in the food industry it is important to know the amount of citric acid that is present in products derived from fruits such as oranges or lemons.
In the pharmaceutical industry, citric acid is used as a stabiliser in various formulations, as a drug component and as an anticoagulant in blood for transfusions.
In the medical domain, the new fluorescent sensor can be useful to determine pathological levels of citric acid, that is, it would potentially serve as a tool for diagnosing disease. “The relationship between low citric acid concentrations and cancer processes, such as that of prostate tumours, is well known. The relationship between the absence of citric acid in urine and the likelihood of developing kidney stones is also well known,” the researchers at the UJI explain. Up till now, citric acid has generally been determined by nuclear magnetic resonance in the case of prostate cancer or by the citrate lyase method in the case of kidney stones.
The research was conducted by the researchers Francisco Galindo, Santiago V. Luis, María Isabel Burguete and Laura Vigara, from the Department of Inorganic and Organic Chemistry at the UJI.