Light-induced morphological transition between unconjugated bilirubin photoisomers

Molecular Simulation Studies on the Interactions of Bilirubin at Different States with a Lipid Bilayer

The unconjugated bilirubin (BR) may penetrate through the cell membrane and cause a severe cytotoxicity. However, the molecular mechanism underlying the penetration of BR into the cell membrane is still largely unknown. In this work, we systematically investigate the interaction of BR and a lipid bilayer under different conditions by using all-atom molecular dynamics simulations. It is found that BR at the Z,Z conformation can easily enter into the interior of the lipid bilayer due to its hydrophobicity. However, when BR transforms from the Z,Z conformation to the E,E conformation (after the blue-light emission), its penetration ability is greatly reduced (especially at its ionized state). This study may offer useful physical insights into the effect of phototherapy on the penetration behavior and the cytotoxicity of the unconjugated BR.

A novel optical assay system for bilirubin concentration measurement in whole blood

As a biomarker for liver disease, bilirubin has been utilized in prognostic scoring systems for cirrhosis. While laboratory-based methods are used to determine bilirubin levels in clinical settings, they do not readily lend themselves to applications outside of hospitals. Consequently, bilirubin monitoring for cirrhotic patients is often performed only intermittently; thus, episodes requiring clinical interventions could be missed. This work investigates the feasibility of measuring bilirubin concentration in whole porcine blood samples using dual-wavelength transmission measurement. A compact and low-cost dual-wavelength transmission measurement setup is developed and optimized to measure whole blood bilirubin concentrations. Using small volumes of whole porcine blood (72 L), we measured the bilirubin concentration within a range corresponding to healthy individuals and cirrhotic patients (1.2-30 mg/dL). We demonstrate that bilirubin levels can be estimated with a positive correlation (R-square > 0.95) and an accuracy of 1.7 mg/dL, with higher reliability in cirrhotic bilirubin concentrations (> 4 mg/dL) critical for high-risk patients. The optical and electronic components utilized are economical and can be readily integrated into a miniature, low-cost, and user-friendly system. This could provide a pathway for point-of-care monitoring of blood bilirubin outside of medical facilities (e.g. patients home).