Free Bilirubin Research Articles

Paper-based potentiometric sensing of free bilirubin in blood serum

Bilirubin is predominantly formed in the liver as a result of breakdown of hemoglobin. Knowing the concentration of bilirubin in serum is important in evaluating the health of the liver, and for the diagnosis of hyperbilirubinemia (a condition that afflicts approximately 60% of full-term and 80% of pre-term newborns). This paper describes the design and fabrication of a potentiometric sensor for the determination of free bilirubin in serum. The sensor has a polymeric ion-selective membrane, and selectively measures free ionic bilirubin (“unbound” bilirubin – i.e., bilirubin not complexed to albumin or other complexing agents), in the presence of other anions — chloride, phosphate, pyruvate, deoxycholate, and lactate — also present in serum. The linear response range of the sensor (1.0 mM to 0.10 μM bilirubin, measured in a sodium phosphate buffer with pH 8.6) covers the clinically-relevant concentration of bilirubin in serum (5–500 μM). Free bilirubin could be detected in human blood serum with this potentiometric sensor. The components of the potentiometric bilirubin sensor were embedded in a paper-based device to provide a sensor that is disposable and easy to use, and thus is suitable for applications at the point-of-care. The paper-based potentiometric bilirubin sensor exhibited a response range of 5.0–0.10 mM (sufficient to cover the clinically-relevant concentration of bilirubin in serum). Only 15 μL of sample is required for measurement of the concentration of free bilirubin, and the analysis can be performed in less than two minutes.

Portable and Label-Free Detection of Blood Bilirubin with Graphene-Isolated-Au-Nanocrystals Paper Strip.

Point-of-care testing (POCT) devices represent a growing field that aims to develop low-cost, rapid, sensitive diagnostic testing platforms that are portable and self-contained. Surface-enhanced Raman spectroscopy (SERS) is an approach has shown high potential in POCT technology. However, the specificity or ability to uniquely detect a desired biomarker in complex biological samples is a key factor for translating SERS technologies to POCT. Herein, we fabricated cellulose SERS strips (CS) decorated with novel plasmonic nanoparticles, termed graphene-isolated-Au-nanocrystals (GIANs), for the portable detection of complex biological samples. This CS@GIANs SERS strip was used to detect free bilirubin (BR) in the blood of newborns, a biomarker of jaundice, without sample labeling or prepreparation. CS@GIANs showed superior affinity to hydrophobic BR molecules compared to typical SERS substrate, which reduced the steric hindrance effect from the nonspecific binding of BR with serum albumin in blood and improved sensitivity. Meanwhile, with the separation property of cellulose chromatography papers, CS@GIANs showed superior anti-interference to other biomolecules that had been previously adsorbed on the SERS strip. Moreover, the SERS signal from the graphitic shell of GIANs could be used as a stable internal calibration standard, which improved the reproducibility and accuracy of Raman analysis. Such a cellulose SERS strip holds high potential for enhancing current efforts in the development of rapid and low-cost point-of-care diagnostic testing.

Serum free bilirubin is a potential biomarker of endogenous antioxidant capacity of human vascular endothelium

Bilirubin is a potent endogenous antioxidant with anti-inflammatory and anti-thrombotic effects. It is also in a negative correlation with the risk of cardiovascular disease, such as ischemic heart disease, hypertension, type II diabetes, metabolic syndrome and obesity. In our study, we first proved that bilirubin is not only in the serum, but also endogenously present in the endothelial cells of the vessels, which are crucial in maintaining the normal vascular function. With the development of new HPLC-Thermal Lens Spectroscopy analysis methods, we could quantitatively determine the low levels of bilirubin in endothelial cells. We found that intracellular contents of bilirubin can be increased by induction of genes for its synthesis (evidence that bilirubin is endogenous in endothelium) and/or if the content of bilirubin in the extracellular medium is increased. The intracellular antioxidative ability of bilirubin (EC50 = 11 nM) was also determined, which is in the concentration range of measured free bilirubin in serum (10–15 nM). This means that extracellular and intracellular free bilirubin concentrations are in dynamic equilibrium, providing an accessible biomarker for the assessment of the endothelial oxidative stress status.

High efficiency 3D nanofiber sponge for bilirubin removal used in hemoperfusion.

The accumulation of bilirubin in the body could cause nervous system diseases and even endanger life in severe cases for people with liver damage or metabolic obstruction. Hemoperfusion has been considered as one of the most efficient treatments to remove extra bilirubin. Although, the current bilirubin adsorbents could adsorb the free bilirubin effectively, the albumin-bound bilirubin in plasma is hard to remove. Here, we develop a 3D nanofiber sponge fabricated by combination of electrospinning and improved gas-foaming techniques. The amino groups and BSA molecules were immobilized on the fiber surface as the affinity groups to adsorb bilirubin. The 3D nanofiber sponges have layered structure and significantly higher porosity than two-dimensional nanofiber membranes. The special 3D structure renders the sponge fully contact with the adsorbed liquid and reduces the diffusion distance of the adsorbate, thus increases the sponge's adsorption rate. The BSA immobilized nanofiber sponge showed large adsorption capacity in both aqueous solution (maximum adsorption capacity was 36.8237 mg/g) and plasma (maximum adsorption capacity was 25.2908 mg/g), rapid adsorption rate (achieved adsorption equilibrium in 60 min) and well blood compatibility.

Ultrasensitive free bilirubin detection in whole blood via counting quantum dots aggregates at single nanoparticle level

Here we report a versatile strategy for detecting bilirubin by harnessing the cationic polymer polyethylenimine induced aggregation of human serum albumin-modified quantum dots. These aggregates are easily discriminated from the individual QD by single molecule spectral imaging microscopy and correlated to the bilirubin concentration. The proposed method can selectively detect bilirubin with a detection limit as low as 0.6 nM. Remarkably, this method has been successfully applied to the trace detection of free bilirubin in human whole blood and serum samples with satisfactory results.

Au nanoparticles functionalized 3D-MoS2 nanoflower: An efficient SERS matrix for biomolecule sensing

Fabrication of Molybdenum disulfide (MoS2) nanostructures and surface functionalization with noble metal nano particles is an emerging field of research as it has potential applications in electronic devices and chemical sensing. Here we report application of gold nanoparticles (AuNPs) decorated MoS2 nanoflowers (Au-MoS2 NFs) as an efficient bio-sensor. MoS2 NFs, synthesized using green synthesis process, are further functionalized with AuNPs to tune their physical properties and make them more appropriate for biological applications. The abundant ‘hot-spots’ created by AuNPs through localization of electromagnetic field endows the Au-MoS2 hybrid structure as an excellent substrate for biochemical sensing through surface enhanced Raman scattering (SERS). The sensing efficiency of the SERS substrate is examined using Rh6G as probe molecule with concentration as low as 10–12 M. Main emphasis is given in detecting free bilirubin, an important component of human blood, using SERS technique. Au-MoS2 NF SERS substrate exhibits high sensitivity, stability and excellent reproducibility in sensing bilirubin from high level (10−3 M) to picomolar level. The concentration (C) dependent SERS intensity (I) is found to follow the general relationship I = Cα, with α ranging from 0.09 to 0.12. The substrate shows excellent selectivity and reliability while sensing of free bilirubin performed in human serum in the presence of crucial interferences such as dextrose, cholesterol and phosphate. In the present study, this Au-MoS2 hybrid offers a new potential biosensing technology for free bilirubin detection and is anticipated to be applied for clinic diagnosis.

Exchange transfusion in initial phase of acute encephalopathy bilirubin of a 7-day old neonate: a case report

Hyperbilirubinemia is a common problem in neonatal period, occurring in 60-70% of term and 80% of preterm infants in the first week of life. The elevation of free unconjugated bilirubin can enter the central nervous system which is noxious to neuron and increase the risk of acute bilirubin encephalopathy (ABE). Risk factors of encephalopathy bilirubin or kernicterus with hemolytic disease such as ABO or Rhesus haemolytic disease, G6PD deficiency. The incidence of ABE is about 0.9/100 000. Clinically bilirubin encephalopathy can be devided into 2 phase, acute and chronic phase. The initial of acute phase is noted by lethargy, hypotonia, decreased movement and poor suck, the symptoms will get worsen if the baby doesn’t get adequte therapy. The main of management ABE is exchange transfusion and continues phototherapy to reduce bilirubin level and prevent further hemolysis.We report a case of exchange transfusion in initial phase of acute encephalopathy bilirubin in a 7-day old neonate with ABO incompatibility, whom had icterus since the first day of life. Other complaints are poor feeding, lethargy and hoarsness of cry since one day before admitted to hospital. He was born from mother with O blood type and positive rhesus. The patient had B blood type with positive rhesus, coomb test was positive and the total bilirubin was 41.49 mg/dL, direct bilirubin was 2.8 mg/dl and indirect bilirubin was 38.69 mg/dL. The patient was treated with exchange transfusion, intensive phototherapy. Â

Predictors of red blood cell transfusion and its association with prognosis in patients undergoing extracorporeal membrane oxygenation.

Few data are available on the potential benefits and risks of red blood cell transfusion in patients undergoing extracorporeal membrane oxygenation. The aim of this study was to identify the determinants and prognosis of red blood cell transfusion in patients undergoing extracorporeal membrane oxygenation, with a special focus on biological parameters during extracorporeal membrane oxygenation treatment. We conducted a single-center retrospective cohort study including all consecutive patients who underwent extracorporeal membrane oxygenation between January 2010 and December 2015. The 201 evaluated patients received a median of 0.9 [0.5-1.7] units of red blood cell per day. Significant and clinically relevant variables that best correlated with units of red blood cell transfused per day of extracorporeal membrane oxygenation were lower median daily prothrombin time in percentage (Quick) ( t = -0.016, p < 0.0001), higher median daily free bilirubin level ( t = 0.016, p < 0.0001), and lower pH ( t = -2.434, p < 0.0001). In multivariate analysis, red blood cell transfusion was associated with a significantly higher rate of in-intensive care unit mortality (per red blood cell unit increment; adjusted odds ratio: 1.07, 95% confidence interval: 1.02-1.12, p = 0.005). It was also associated with higher rates of acute renal failure ( p = 0.025), thromboembolic complications ( p = 0.0045), and sepsis ( p = 0.015). This study suggests that red blood cell transfusion may be associated with a higher mortality rate and with severe complications. However, we cannot conclude a direct causal relationship, as red blood cell transfusion may be only a marker of poor outcome. We recommend that physicians correct acidosis and hemolysis in patients undergoing extracorporeal membrane oxygenation whenever possible.

Bilirubin binding in jaundiced newborns: from bench to bedside?

Bilirubin-induced neurologic dysfunction (BIND) is a spectrum of preventable neurological sequelae in jaundiced newborns. Current total plasma bilirubin (BT) concentration thresholds for phototherapy and/or exchange transfusion poorly predict BIND. The unbound (free) bilirubin (Bf) measured at these BT thresholds provides additional information about the risk for BIND. Bf can be readily adapted to clinical use by determining Bf population parameters at current BT thresholds. These parameters can be established using a plasma bilirubin binding panel (BBP) consisting of BT, Bf, and two empiric constants, the maximum BT (BTmax) and the corresponding equilibrium association bilirubin constant (K). BTmax and K provide the variables needed to accurately estimate Bf at BT < BTmax to obtain Bf at threshold BT in patient samples. Once Bf population parameters are known, the BBP in a newborn can be used to identify poor bilirubin binding (higher Bf at the threshold BT compared with the population) and increased risk of BIND. The BBP can also be used in jaundice screening to better identify the actual BT at which intervention would be prudent. The BBP is used with current BT thresholds to better identify the risk of BIND and whether and when to intervene.

Voltammetric determination of bilirubin on disposable screen printed carbon electrode

Disposable screen printed carbon electrodes have been developed for the quantitative determination of free bilirubin. The electrodes were fabricated using graphite carbon ink and characterized with microscopy, spectroscopy and diffraction studies. The carbon ink for printing is made of graphite nanoparticles of size around 50 nm. Electrochemical oxidation of bilirubin was carried out voltammetrically in Trizma buffer of pH 8.5. The sensor showed a dynamic detection range of 5–600 μM and a sensitivity of 95 μAμM−1 cm−2. The SPCE showed superior performance than many of the reported sensors in terms of dynamic range, sensitivity and oxidation potential. Molecules such as ascorbic acid, uric acid, dopamine, glucose, creatinine and ethanol were tested using SPCE and found to be non interfering with the detection of creatinine in the physiological conditions. The sensor was tested using bilirubin spiked serum samples and found that it is giving response to free bilirubin. The sensor was also used to study the affinity of free bilirubin to albumin and displacement of bilirubin from albumin by ibuprofen.

Call for more transparency in manufacturers declarations on serum indices: On behalf of the Working Group for Preanalytical Phase (WG-PRE), European Federation of Clinical Chemistry and Laboratory Medicine (EFLM)

The presence of interfering substances like free hemoglobin, bilirubin or lipids compromises sample quality and potentially affects laboratory analysis and test results. Recently, the use of serum indices for objectively assessing sample quality has become commonplace and many preanalytical platforms, as well as clinical chemistry and coagulation analyzers, are now equipped with this analytical feature. Nevertheless, some important drawbacks remain in this practice, mainly pertaining the measurement procedure, the approach for reporting interference data, the definition of objective thresholds of interference after which test results may be biased, and the lack of harmonized practices for describing how interference cut-offs have been identified. Therefore, this document aims to discuss these important caveats and propose some reliable solutions that may be adopted by manufacturers for increasing worldwide harmonization of serum indices.

Unbound bilirubin measurements by a novel probe in preterm infants

Background: Hyperbilirubinemia occurs in over 80% of newborns and severe bilirubin toxicity can lead to neurological dysfunction and death, especially in preterm infants. Currently, the risk of bilirubin toxicity is assessed by measuring the levels of total serum bilirubin (TSB), which are used to direct treatments including immunoglobulin administration, phototherapy, and exchange transfusion. However, free, unbound bilirubin levels (Bf) predict the risk of bilirubin neurotoxicity more accurately than TSB.Objective: To examine Bf levels in preterm infants and determine the frequency with which they exceed reported neurotoxic thresholds.Methods: One hundred thirty preterm infants (BW 500–2000 g; GA 23–34 weeks) were enrolled and Bf levels measured during the first week of life by the fluorescent Bf sensor BL22P1B11-Rh. TSB and plasma albumin were measured by standard techniques. Bilirubin-albumin dissociation constants (Kd) were calculated based on Bf and plasma albumin.Results: Five hundred eighty samples were measured during the first week of life, with an overall mean Bf of 13.6 ± 9.0 nM. A substantial number of measurements exceeded potential toxic thresholds levels as reported in the literature. The correlation between Bf and TSB was statistically significant (r2 0.17), but this weak relationship was lost at high Bf levels. Infants <28-week gestations had more hearing screening failures than infants ≥28-week gestation.Conclusions: Unbound (free) bilirubin values are extremely variable during the first week of life in preterm infants. A significant proportion of these values exceeded reported neurotoxic thresholds.

To evaluate the correlation between the change of immune system function before and after the treatment of malignant obstructive type jaundice treated with biliary stent.

To evaluate the correlation between the change of immune system function before and after the treatment of malignant obstructive type jaundice (MOJ) treated with a biliary stent. 148 patients who were admitted to the Department of Digestive System for malignant obstructive jaundice were selected according to the standardized criterion. Amongst the total sample size, 78 were male patients and 70 were female patients, with an average age of (43.6 ± 5.5) years. After admission, the patients completed the blood routine examination and received biliary stent treatment to relieve the sign and symptoms of jaundice. Follow-up observation included total white blood cells, CD4+T cell count, CD8+T cell count, the ratio of CD4+/CD8, neutrophil counts neutrophils percentage, total bilirubin, free bilirubin, alanine aminotransferase (ALT), and inflammatory factors. After three weeks of follow-up visit, CD4+T lymphocyte absolute value of patients markedly increased compared with that of pre-operation, and the difference had statistical significance (p < 0.05). The total bilirubin, free bilirubin, ALT, and inflammatory factors, such as hs-CRP, TNF-α in plasma of patients was significantly lower than that before the operation and the difference was statistically significant (p < 0.05). After six weeks of follow-up visit, the ratio of CD4+/CD8+ increased and the difference had statistical significance (p < 0.05) compared with that before biliary stent implantation. However, the white blood cell and neutrophil granulocyte did not improve significantly. It was found that CD4+/CD8+T lymphocyte had relation with the level of hs-CRP. The patients with the (MOJ) treated with implanted biliary stent revealed relive in the obstruction of the biliary tract, which will further significantly improve the cholestasis. The ratio of CD4+/CD8+T lymphocyte increased, which will improve the immune system function of the patients, decreases the possibility of infection, and improves the overall survival quality.

Sensitive detection of free bilirubin in blood serum using β-diketone modified europium-doped yttrium oxide nanosheets as a luminescent sensor.

Free bilirubin, when present in excess in the human body, can cause a multitude of diseases and disorders and even be fatal; hence, detecting it is of paramount importance. Herein, we report a luminescence quenching-based non-enzymatic method for the convenient, reliable, and rapid detection of free bilirubin in blood serum samples using sensing films (nanosheets/PS, nanosheets-tta/PS, and nanosheets-dbt/PS) as luminescent sensors. The luminescence intensity of the sensing films is linearly related to the free bilirubin concentration. Nanosheets-tta/PS demonstrated excellent sensing properties for the sensitive and reliable detection of free bilirubin in the range of 0.0–60.0 μM with a correlation coefficient of 0.9915, as compared to nanosheets/PS or nanosheets-dbt/PS. The limit of detection for the determination of free bilirubin was 41 nM. This method can be used to design a sensor-based test spot as a medical detection device for the visual detection of free bilirubin.

Bilirubin-Induced Oxidative Stress Leads to DNA Damage in the Cerebellum of Hyperbilirubinemic Neonatal Mice and Activates DNA Double-Strand Break Repair Pathways in Human Cells.

Unconjugated bilirubin is considered a potent antioxidant when present at moderate levels. However, at high concentrations, it produces severe neurological damage and death associated with kernicterus due to oxidative stress and other mechanisms. While it is widely recognized that oxidative stress by different toxic insults results in severe damage to cellular macromolecules, especially to DNA, no data are available either on DNA damage in the brain triggered by hyperbilirubinemia during the neonatal period or on the activation of DNA repair mechanisms. Here, using a mouse model of neonatal hyperbilirubinemia, we demonstrated that DNA damage occurs in vivo in the cerebellum, the brain region most affected by bilirubin toxicity. We studied the mechanisms associated with potential toxic action of bilirubin on DNA in in vitro models, which showed significant increases in DNA damage when neuronal and nonneuronal cells were treated with 140 nM of free bilirubin (Bf), as determined by γH2AX Western blot and immunofluorescence analyses. Cotreatment of cells with N-acetyl-cysteine, a potent oxidative-stress inhibitor, prevented DNA damage by bilirubin, supporting the concept that DNA damage was caused by bilirubin-induced oxidative stress. Bilirubin treatment also activated the main DNA repair pathways through homologous recombination (HR) and nonhomologous end joining (NHEJ), which may be adaptive responses to repair bilirubin-induced DNA damage. Since DNA damage may be another important factor contributing to neuronal death and bilirubin encephalopathy, these results contribute to the understanding of the mechanisms associated with bilirubin toxicity and may be of relevance in neonates affected with severe hyperbilirubinemia.

Facile hydrothermal synthesis of branched polyethylenimine grafted electrospun polyacrylonitrile fiber membrane as a highly efficient and reusable bilirubin adsorbent in hemoperfusion

Bilirubin is a pathogenic toxin in the blood of patients with liver failure, and bilirubin adsorbents have been applied to remove the extra bilirubin in hemoperfusion. However, the developing of high-performance adsorbents with satisfying removal ability, physical/chemical stability, biocompatibility and hemocompatibility still needs to be explored. In this study, branched polyethylenimine (bPEI) grafted electrospun polyacrylonitrile (PAN) fiber membrane (bPEIPANFM) was fabricated via a green hydrothermal process. The hydrothermal temperature, hydrothermal time and the weight ratio of bPEI to PAN were investigated to seek the optimal bilirubin adsorption capacity. The results revealed that bPEIPANFM (hydrothermal temperature at 160 °C, hydrothermal time at 10 h and the weight ration of bPEI to PAN at 10:1) showed the best removal ability toward bilirubin. Batch adsorption experiments for both free bilirubin solution and bovine serum albumin (BSA)-bonded bilirubin solution were studied. The maximum adsorption capacity of bPEIPANFM toward BSA-bonded bilirubin was 112.87 mg/g, which is higher than those of many reported adsorbents. After ten regeneration cycles, the removal efficiency could still maintain 95%. Moreover, the bPEIPANFM also exhibited excellent biocompatibility and hemocompatibility. These obtained results demonstrate that this study may provide a new adsorbent for removing bilirubin in hemoperfusion applications.

Molecular Ellipticity of Circulating Albumin-Bilirubin Complex Associates With Mortality in Patients With Severe Alcoholic Hepatitis

Hyperbilirubinemia and hypoalbuminemia are features of hepatic dysfunction that associate with disease severity. This is because hepatic insufficiency causes hypoalbuminemia, which indirectly increases the circulating levels of free bilirubin. Circular dichroism (CD) spectroscopy can be used to quantify the molecular ellipticity (ME) of the albumin-bilirubin complex, and might associate with the severity or outcome of severe alcoholic hepatitis (SAH). We performed a cross-sectional study of 265 patients with SAH admitted in the Department of Hepatology, Institute of Liver and Biliary Sciences in New Delhi, India from January 2014 through January 2016. Blood samples were collected and patients were followed for 12 months or death. The molar ratios of bilirubin: albumin and albumin-bilirubin complexes were determined for a discovery cohort (30 patients who survived the study period and 60 patients who did not survive) and compared with those of 60 patients with alcoholic cirrhosis and 30 healthy individuals (controls). Optical activities of albumin-bilirubin complexes in blood samples were determined by CD spectroscopy and compared among groups. Findings were validated in a separate cohort of 150 patients with SAH from the same institute. We studied the correlation between ME and albumin binding capacity (ABiC). The molar ratio of bilirubin: albumin was higher in patients with SAH than with alcoholic cirrhosis or controls (P < .05). Patients with SAH had different CD spectra and higher ME than the other groups (P < .01); ME correlated with model for end-stage liver disease score (with and without Na) and discriminant function (r2 > .3; P < .01). ME values above a cut off of 1.84 mdeg predicted 3-month mortality in patients with SAH with an area under receiver operating characteristic curve of 0.87 (95% CI, 0.79-0.95), a 77% positive predictive value, and a 90% negative predictive value. The hazard ratio and concordance index of ME values for 3-month mortality in patients with SAH was 10% higher than the hazard ratio and concordance index of model for end-stage liver disease score. In patients with SAH, there was an inverse correlation between ME and ABiC (r2 > 0.7; P < .01). We observed a significant reduction in ABiC with increasing levels of bilirubin invitro prepared albumin-bilirubin complex. In a cross-sectional study of patients with SAH, we associated ME of the albumin-bilirubin complex, measured by CD spectroscopy, with outcomes of patients with SAH. Increased loading of bilirubin on albumin could explain reduced albumin function. Bilirubin removal by albumin dialysis might benefit patients with SAH.

Nano-Encapsulation of Bilirubin in Pluronic F127–Chitosan Improves Uptake in β Cells and Increases Islet Viability and Function after Hypoxic Stress

Pancreatic islet transplantation is the only curative, noninvasive treatment for type 1 diabetes mellitus; however, high rates of cell death in the immediate postimplantation period have limited the success of this procedure. Bilirubin, an endogenous antioxidant, can improve the survival of murine pancreatic allografts during hypoxic stress but has poor solubility in aqueous solutions. We hypothesized that nano-encapsulation of bilirubin in pluronic 127–chitosan nanoparticle bilirubin (nBR) would improve uptake by murine pancreatic islet cells and improve their viability following hypoxic stress. Nano-bilirubin was synthesized, and drug release characteristics were studied in vitro. Cellular uptake of nBR was compared to free bilirubin (fBR) in an insulinoma cell line (INS-R3) model using confocal-like structured illumination microscopy. Next, C57BL/6 mouse islets were treated with concentrations of 0 to 20 μM of nBR, fBR, or empty nanoparticle (eNP), prior to incubation under standard or hypoxic conditions. Islet viability and function were compared between treatment groups. Release of bilirubin was greatest from nBR suspended in protein-rich solution. Increased, selective uptake of nBR by INS-R3 cells was demonstrated. Cell death after hypoxic stress was significantly decreased in murine islets treated with 5 μM nBR (18.5% ± 14.1) compared to untreated islets (33.5% ± 17.5%; P = 0.019), with reduction in central necrosis. Treatment group had a significant effect on glucose stimulation index [SI], (P = 0.0137) and islets treated with 5 μM nBR had the highest SI overall. Delivery of bilirubin using pluronic F127–chitosan NP improves uptake by murine islets compared to fBR and offers dose-dependent protective effects following hypoxic stress.

Highly Sensitive and Selective Sensing of Free Bilirubin Using Metal–Organic Frameworks-Based Energy Transfer Process

Free bilirubin, a key biomarker for jaundice, was detected with a newly designed fluorescent postsynthetically modified metal organic framework (MOF) (UIO-66-PSM) sensor. UiO-66-PSM was prepared based on the aldimine condensation reaction of UiO-66-NH2 with 2,3,4-trihydroxybenzaldehyde. The fluorescence of UIO-66-PSM could be effectively quenched by free bilirubin via a fluorescent resonant energy transfer process, thus achieving its recognition of free bilirubin. It was the first attempt to design a MOF-based fluorescent probe for sensing free bilirubin. The probe exhibited fast response time, low detection limit, wide linear range, and high selectivity toward free bilirubin. The sensing system enabled the monitor of free bilirubin in real human serum. Hence, the reported free bilirubin sensing platform has potential applications for clinical diagnosis of jaundice.

Supplementation with Phycocyanobilin, Citrulline, Taurine, and Supranutritional Doses of Folic Acid and Biotin-Potential for Preventing or Slowing the Progression of Diabetic Complications.

Oxidative stress, the resulting uncoupling of endothelial nitric oxide synthase (eNOS), and loss of nitric oxide (NO) bioactivity, are key mediators of the vascular and microvascular complications of diabetes. Much of this oxidative stress arises from up-regulated nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity. Phycocyanobilin (PhyCB), the light-harvesting chromophore in edible cyanobacteria such as spirulina, is a biliverdin derivative that shares the ability of free bilirubin to inhibit certain isoforms of NADPH oxidase. Epidemiological studies reveal that diabetics with relatively elevated serum bilirubin are less likely to develop coronary disease or microvascular complications; this may reflect the ability of bilirubin to ward off these complications via inhibition of NADPH oxidase. Oral PhyCB may likewise have potential in this regard, and has been shown to protect diabetic mice from glomerulosclerosis. With respect to oxidant-mediated uncoupling of eNOS, high-dose folate can help to reverse this by modulating the oxidation status of the eNOS cofactor tetrahydrobiopterin (BH4). Oxidation of BH4 yields dihydrobiopterin (BH2), which competes with BH4 for binding to eNOS and promotes its uncoupling. The reduced intracellular metabolites of folate have versatile oxidant-scavenging activity that can prevent oxidation of BH4; concurrently, these metabolites promote induction of dihydrofolate reductase, which functions to reconvert BH2 to BH4, and hence alleviate the uncoupling of eNOS. The arginine metabolite asymmetric dimethylarginine (ADMA), typically elevated in diabetics, also uncouples eNOS by competitively inhibiting binding of arginine to eNOS; this effect is exacerbated by the increased expression of arginase that accompanies diabetes. These effects can be countered via supplementation with citrulline, which efficiently enhances tissue levels of arginine. With respect to the loss of NO bioactivity that contributes to diabetic complications, high dose biotin has the potential to “pinch hit” for diminished NO by direct activation of soluble guanylate cyclase (sGC). High-dose biotin also may aid glycemic control via modulatory effects on enzyme induction in hepatocytes and pancreatic beta cells. Taurine, which suppresses diabetic complications in rodents, has the potential to reverse the inactivating impact of oxidative stress on sGC by boosting synthesis of hydrogen sulfide. Hence, it is proposed that concurrent administration of PhyCB, citrulline, taurine, and supranutritional doses of folate and biotin may have considerable potential for prevention and control of diabetic complications. Such a regimen could also be complemented with antioxidants such as lipoic acid, N-acetylcysteine, and melatonin—that boost cellular expression of antioxidant enzymes and glutathione—as well as astaxanthin, zinc, and glycine. The development of appropriate functional foods might make it feasible for patients to use complex nutraceutical regimens of the sort suggested here.