Photodegradation kinetics for bilirubin sensing: New solutions for old problems

Abstract

Blood bilirubin levels monitoring is essential for the management of liver disease and neonatal hyperbilirubinemia. Whilst highly accurate, the existing bilirubin measurement techniques do not lend themselves to point-of-care (PoC) applications. To address this challenge, PoC devices using optical methods (mainly transcutaneous technique), have been demonstrated for bilirubin levels determination. Beyond its distinct absorption features used for optical measurements, bilirubin is known for its unique property of a non-catalytic degradation under blue light illumination. This is indeed the basis of blue light phototherapy used to treat or alleviate neonatal jaundice. This work investigates the feasibility of measuring bilirubin concentration using both multi-wavelength (MWL) and photodegradation kinetics approaches. Multi wavelength approach was investigated by correlating the optical responses with the concentration of bilirubin. The degradation approach was investigated by assessing the changes in bilirubin's spectrophotometric characteristics induced by blue light (470 nm) irradiation as a function of optical energy density (up to 3 J/cm2). The solid-state full-range spectroscopy (absorbance, reflectance, photoluminescence, and Raman) and a PoC testing on a system-on-chip are used and a new kinetic model describing the degradation reaction is proposed. Results show that the optical responses and photodegradation features correlated well with bilirubin concentration with R-square greater than 0.9. Additionally, the techniques' performance was examined using the merits of accuracy, precision, sensitivity, and specificity parameters (all are greater than 90%). Our analyses suggest that the method is sufficiently enough to provide reliable indications of bilirubin levels. The proposed technique may offer a portable, miniaturized, and facile mean for in-vitro and in-vivo bilirubin monitoring and estimation.