Using Firefly Squid Bioluminescence for Early Diagnosis of Diabetic Nephropathy


The firefly squid (Watasenia scintillans) is a luminous species found in the Sea of Japan, exhibiting strong blue luminescence mainly from the fourth arm. Especially in Toyama Bay, bioluminescence of firefly squid can be observed with the naked eye every spring when they come to the beach to spawn (Figure 1). In this article, we proved that a compound called luciferin, which the firefly squid possesses, can measure the albumin concentration in urine of diabetic patients by using its luminescence in reaction with albumin.

Background and Results

In the body of luminescent organisms, luciferase protein reacts with its substrate, luciferin, to emit light. Firefly squid, like other luminescent organisms, are thought to emit blue light through a reaction between luciferase and luciferin. In this study, the authors discovered the unexpected fact that firefly squid luciferin emits light not only by reacting with luciferase, but also with albumin, a protein present in the blood. When albumin reacted withluciferin in buffer, luminescence was proportional to albumin concentration over a wide range (Figure 2). This indicates that the concentration of albumin in the liquid can be measured using firefly squid luciferin.

In diabetic nephropathy, a complication of diabetes mellitus, it is known that trace amounts of albumin leak into the urine from the stage without symptoms, and treatment at this stage is considered important to prevent progression. In other words, techniques for quantifying urinary albumin are necessary for the prevention of diabetic nephropathy.

The authors investigated the possibility of quantifying albumin in urine using firefly squid luciferin. As a result, it was found that albumin can be quantified by precipitating the protein in a urine sample by acetone precipitation. The quantitative data obtained were compared with the method for measuring albumin concentration using antibodies, and the results showed a high correlation between the two methods, indicating that this method is comparable to the conventional method. This is the first report of firefly squid being useful for medical measurements.

This work was supported by the FIRSTBANK of Toyama Scholarship Foundation Research Grant.

Original article information


International Journal of Molecular Sciences


A New Method for Albuminuria Measurement Using a Specific Reaction between Albumin and the Luciferin of the Firefly Squid Watasenia scintillans


Tetsuya Ishimoto, Takuya Okada, Shiho Fujisaka, Kunimasa Yagi, Kazuyuki Tobe , Naoki Toyooka and Hisashi Mori