In vitro production of bilirubin photoisomers by light irradiation using neoBLUE

Background: The light-emitting diode is used as one of the new light sources for phototherapy. NeoBLUE (Atom Medical, Tokyo, Japan) incorporates blue light-emitting diodes for the treatment of neonatal hyperbilirubinemia. The authors compared the in vitro efficacy of neoBLUE with conventional phototherapy devices. Methods: The three light devices used included neoBLUE and two conventional phototherapy devices with six blue–white (BW) or six green (GR) fluorescent tubes. A bilirubin/human serum albumin solution (15 mg/dL) in 200 × 300 mm elliptical bag was irradiated with each three light device. The average light intensity of neoBLUE, BW and GR was 22.5, 10.2 and 2.6 μW/cm2 per nm, respectively, for the irradiated area. Bilirubin photoisomers and native bilirubin were measured by high-performance liquid chromatography. Results: In neoBLUE, BW and GR, the respective production rate of cyclobilirubin was 6.0, 3.7 and 3.9 × 10−2 mg/dL/min, and the respective (4Z, 15E)-bilirubin/(4Z, 15Z)-bilirubin ratio after irradiation was 0.44, 0.33 and 0.12; the (4Z, 15Z)-bilirubin reduction rate at 20 min after irradiation was 60, 68 and 82%, respectively. The reduction rate of (4Z, 15Z)-bilirubin correlated with the (4Z, 15E)-bilirubin/(4Z, 15Z)-bilirubin ratio. Conclusion: Phototherapy using the neoBLUE under high level may be clinically more effective than therapy using the conventional light source from the results of the production rate of cyclobilirubin.