A Novel Method for Measuring Serum Unbound Bilirubin Levels Using Glucose Oxidase-Peroxidase and Bilirubin-Inducible Fluorescent Protein (UnaG): No Influence of Direct Bilirubin

175 Years of Bilirubin Testing: Ready for Point-of-Care?

Bilirubin was first detected in blood in 1847 and since then has become one of the most widely used biomarkers for liver disease. Clinical routine bilirubin testing is performed at the hospital laboratory, and the gold standard colorimetric test is prone to interferences. The absence of a bedside test for bilirubin delays critical clinical decisions for patients with liver disease. This clinical care gap has motivated the development of a new generation of bioengineered point-of-care bilirubin assays. In this Perspective, recently developed bilirubin assays are critically discussed, and their translational potential evaluated.

First report on the regulation and function of carbon metabolism during large sclerotia formation in medicinal fungus Wolfiporia cocos

The medicinal fungus Wolfiporia cocos colonizes and then grows on the wood of Pinus species, and utilizes a variety of Carbohydrate Active Enzymes (CAZymes) to degrades wood for the development of large sclerotia that is mostly built up of beta-glucans. Some differentially expressed CAZymes were revealed by comparisons between the mycelia cultured on potato dextrose agar (PDA) and sclerotia formed on pine logs in previous studies. Here, different profile of expressed CAZymes were revealed by comparisons between the mycelia colonization on pine logs (Myc.) and sclerotia (Scl.b). To further explore the regulation and function of carbon metabolism in the conversion of carbohydrates from Pine species by W. cocos, the transcript profile of core carbon metabolism was firstly analyzed, and it was characterized by the up-regulated expression of genes in the glycolysis pathway (EMP) and pentose phosphate pathway (PPP) in Scl.b, as well as high expression of genes in the tricarboxylic acid cycle (TCA) in both Myc. and Scl.b stages. The conversion between glucose and glycogen and between glucose and β-glucan was firstly identified as the main carbon flow in the differentiation process of W. cocos sclerotia, with a gradual increase in the content of β-glucan, trehalose and polysaccharide during this process. Additionally, gene functional analysis revealed that the two key genes (PGM and UGP1) may mediate the formation and development of W. cocos sclerotia possibly by regulating β-glucan synthesis and hyphal branching. This study has shed light on the regulation and function of carbon metabolism during large W. cocos sclerotium formation and may facilitate its commercial production.

Noninvasive direct bilirubin detection by spectral analysis of color images using a Mini-LED light source

Urine test paper is a standard, noninvasive detection method for direct bilirubin, but this method can only achieve qualitative analysis and cannot achieve quantitative analysis. This study used Mini-LEDs as the light source, and direct bilirubin was oxidized to biliverdin by an enzymatic method with ferric chloride (FeCl₃) for labeling. Images were captured with a smartphone and evaluated for red (R), green (G), and blue (B) colors to analyze the linear relationship between the spectral change of the test paper image and the direct bilirubin concentration. This method achieved noninvasive detection of bilirubin. The experimental results demonstrated that Mini-LEDs can be used as the light source to analyze the grayscale value of the image RGB. For the direct bilirubin concentration range of 0.1-2 mg/dL, the green channel had the highest coefficient of determination coefficient (R²) of 0.9313 and a limit of detection of 0.56 mg/dL. With this method, direct bilirubin concentrations higher than 1.86 mg/dL can be quantitatively analyzed with the advantage of rapid and noninvasive detection.

Petukhov P, Kurilova OV, Ilinsky VV, Trakhtman PE, Dadali EL, Samokhodskaya LM, Kamalov AA, Kost OA. Blood ACE Phenotyping for Personalized Medicine: Revelation of Patients with Conformationally Altered ACE

Background: The angiotensin-converting enzyme (ACE) metabolizes a number of important peptides participating in blood pressure regulation and vascular remodeling. Elevated blood ACE is a marker for granulomatous diseases and elevated ACE expression in tissues is associated with increased risk of cardiovascular diseases. Objective and Methodology: We applied a novel approach -ACE phenotyping-to find a reason for conformationally impaired ACE in the blood of one particular donor. Similar conformationally altered ACEs were detected previously in 2-4% of the healthy population and in up to 20% of patients with uremia, and were characterized by significant increase in the rate of angiotensin I hydrolysis. Principal findings: This donor has (1) significantly increased level of endogenous ACE inhibitor in plasma with MW less than 1000; (2) increased activity toward angiotensin I; (3) M71V mutation in ABCG2 (membrane transporter for more than 200 compounds, including bilirubin). We hypothesize that this patient may also have the decreased level of free bilirubin in plasma, which normally binds to the N domain of ACE. Analysis of the local conformation of ACE in plasma of patients with Gilbert and Crigler-Najjar syndromes allowed us to speculate that binding of mAbs 1G12 and 6A12 to plasma ACE could be a natural sensor for estimation of free bilirubin level in plasma. Totally, 235 human plasma/sera samples were screened for conformational changes in soluble ACE. Conclusions/Significance: ACE phenotyping of plasma samples allows us to identify individuals with conformationally altered ACE. This type of screening has clinical significance because this conformationally altered ACE could not only result in the enhancement of the level of angiotensin II but could also serve as an indicator of free bilirubin levels.

NAD+ attenuates bilirubin-induced augmentation of voltage-gated calcium currents in neurons of the ventral cochlear nucleus

Nicotinamide adenine dinucleotide (NAD+) is a ubiquitous molecule with wide-ranging roles in several cell processes, such as regulation of calcium homeostasis and protection against cell injuries. However, the roles of NAD+ in neuroprotection is poorly understood. The main neurons in ventral cochlear nucleus (VCN) are highly susceptible to bilirubin-associated excitotoxicity. We investigated the effects of NAD+ on VCN neurons by whole cell patch-clamp recordings. We found that NAD+ effectively reverses and inhibits bilirubin-mediated enhancement of voltage-gated calcium (VGCC) currents in VCN neurons. Moreover, NAD+ itself did not affect VGCC currents. These results collectively suggest that NAD+ may be neuroprotective by attenuating Ca²⁺ influx to suppress bilirubin-induced intracellular Ca²⁺ overloads. Our research provides a basis for evaluation of NAD+ as a promising therapeutic target for bilirubin encephalopathy and excitotoxicity associated with other neurological disorders.

Photomedicine based on heme-derived compounds

Photoimaging and phototherapy have become major platforms for the diagnosis and treatment of various health complications. These applications require a photosensitizer (PS) that is capable of absorbing light from a source and converting it into other energy forms for detection and therapy. While synthetic inorganic materials such as quantum dots and gold nanorods have been widely explored for their medical diagnosis and photodynamic (PDT) and photothermal (PTT) therapy capabilities, translation of these technologies has lagged, primarily owing to potential cytotoxicity and immunogenicity issues. Of the various photoreactive molecules, the naturally occurring endogenous compound heme, a constituent of red blood cells, and its derivatives, porphyrin, biliverdin and bilirubin, have shown immense potential as noteworthy candidates for clinically translatable photoreactive agents, as evidenced by previous reports. While porphyrin-based photomedicines have attracted significant attention and are well documented, research on photomedicines based on two other heme-derived compounds, biliverdin and bilirubin, has been relatively lacking. In this review, we summarize the unique photoproperties of heme-derived compounds and outline recent efforts to use them in biomedical imaging and phototherapy applications.

Neonatal hyperbilirubinemia and the role of unbound bilirubin

BACKGROUND

Neonatal jaundice occurs in more than 80% of newborn infants. Although mild jaundice is physiologic and possibly neuroprotective, severe hyperbilirubinemia can lead to neurologic dysfunction and death. Hyperbilirubinemia is due to an imbalance between bilirubin production and the developing excretory capacity in the first days of life. Management utilizes total serum bilirubin (TSB) levels, although recent advances suggest a role for unbound bilirubin.

GOALS

The goal of this review is to examine bilirubin biology, toxicology, and clinical effects, discuss preventive and therapeutic measures, describe neurodevelopmental consequences, and propose that, with the advent of new technology, unbound bilirubin is the optimal measurement for the management.

METHODS

Comprehensive review on neonatal hyperbilirubinemia.

RESULTS

Neonatal hyperbilirubinemia can be prevented by tin mesoporphyrin to limit heme oxygenase activity, a key enzyme in bilirubin production, or restricting bilirubin's absorption from the gastrointestinal tract. Treatment modalities include removing bilirubin from the body by exchange transfusion, binding to immunoglobulin, or converting it to a water-soluble isomer with phototherapy. While these approaches have evolved during the past decades, the diagnosis, intervention indications, and prognosis have consistently relied on TSB concentration despite its poor ability to predict an outcome.

CONCLUSIONS

Total serum bilirubin is inadequate to optimize care of the term and preterm infant with hyperbilirubinemia. A rapid, accurate, and more effective indicator of bilirubin neurotoxicity is needed to manage jaundiced infants and for the universal screening of newborn infants. Future measurements of free bilirubin unattached to albumin will improve the management of neonatal hyperbilirubinemia.

Biosensors and biomarkers for determining gestational diabetes mellitus and jaundice in children

Gestational diabetes and jaundice are the correlated diseases predominantly found in mother and newborn child. Jaundice is a neonatal complication with an increased risk when mother has gestational diabetes. Mothers with diabetes at an early stage of gestational age are at higher risk for hyperbilirubinemia (jaundice) and hypoglycemia. So, it is mandatory to monitor the condition of diabetes and jaundice during the pregnancy period for a healthy child and safest delivery. On the other hand, nanotechnology has displayed a rapid advancement that can be implemented to overcome these issues. The development of high-performance diagnosis using appropriate biomarkers provides their efficacy in the detection gestational diabetes and jaundice. This review covers the aspects from a fast-developing field to generate nanosensors in the nanosized dimensions for the applications to overcome these complications by coupling diagnostics with biomarkers. Further, the serum-based biomarkers have been discussed for these inborn complications and also the diagnosis with the current trend.