The effect of hematocrit on in vitro bilirubin photoalteration

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.

The effectiveness of phototherapy using blue-green light for neonatal hyperbilirubinemia - Danish clinical trials

The effectiveness of phototherapy for neonatal hyperbilirubinemia based on Danish clinical trials is presented. Randomized controlled trials on the quality of light showed that blue-green fluorescent light (peak emission at 490 nm) was more efficient than blue fluorescent light (peak emission at 452 nm); blue-green light-emitting diode (LED) light (peak emission at 478 nm) was more efficient than blue LED light (peak emission at 459 nm); and blue-green LED light (peak emission at 497 nm) was equivalent to blue LED light (peak emission at 459 nm). Bilirubin-reducing effects correlated with irradiance, dependent on hemoglobin concentration, and independent of rotating infants. Phototherapy from both above and below was more efficient than therapy applied only from above at high levels of irradiance. In conclusion, we estimate and recommend the use of blue-green LED light (peak emission at 480 nm) rather than blue light (peak emission at 460 nm) for treating of neonatal hyperbilirubinemia.

Sixty years of phototherapy for neonatal jaundice - from serendipitous observation to standardized treatment and rescue for millions

A breakthrough discovery 60 years ago by Cremer et al. has since changed the way we treat infants with hyperbilirubinemia and saved the lives of millions from death and disabilities. "Photobiology" has evolved by inquiry of diverse light sources: fluorescent tubes (wavelength range of 400-520 nm; halogen spotlights that emit circular footprints of light; fiberoptic pads/blankets (mostly, 400-550 nm range) that can be placed in direct contact with skin; and the current narrow-band blue light-emitting diode (LED) light (450-470 nm), which overlaps the peak absorption wavelength (458 nm) for bilirubin photoisomerization. Excessive bombardment with photons has raised concerns for oxidative stress in very low birthweight versus term infants treated aggressively with phototherapy. Increased emphasis on prescribing phototherapy as a "drug" that is dosed cautiously and judiciously is needed. In this historical review, we chronicled the basic to the neurotoxic components of severe neonatal hyperbilirubinemia and the use of standardized interventions.

Newborns bilirubin concentration determined by different methods in relation to hematocrit and albumin level

Background

Monitoring of bilirubin is essential during early neonatal life. Bilirubin in high concentration is toxic to the brain and might cause irreversible neurological damage. Several different methods for bilirubin determination are available nowadays, but inconsistent results may be obtained. The study aimed to compare dry chemistry methods with vanadate oxidation method for bilirubin determination in relation to hematocrit and albumin level in neonates and infants.

Methods

The study included 98 consecutive serum samples from newborns and infants (47 boys and 51 girls, mean age 19 ± 15 days) treated in the University Children's Hospital in Krakow. Total bilirubin (TBil) and neonatal bilirubin (NBil) concentration were measured by dry chemistry analyser (Vitros 4600, Ortho Clinical Diagnostics Inc.). Total bilirubin (TBil_V) was also measured using vanadate oxidation method (Cormay, Poland). Albumin concentration and blood morphology have been routinely determined in all children.

Results

No significant differences between the mean value of NBil (69.00 ± 67.76 μmol/L), TBil (81.26 ± 70.13 μmol/L) and TBilV (75.90 ± 60.62 μmol/L) were noticed. High coefficient correlation between NBil and TBil as well as between NBil and TBil_V were noticed (Pearson's analysis, r = 0.99, r = 0.97, respectively; p < 0.0001 in both cases). There was a positive correlation between the difference (TBil_V - NBil) and hematocrit (p < 0.009, r = 0.2664).

Conclusions

In newborns and infants the same method for bilirubin determination should be used when the concentration of bilirubin is monitored. When using vanadate oxidation method for bilirubin determination, hematocrit value should be taken into account when results are interpreted.

The effect of light wavelength on in vitro bilirubin photodegradation and photoisomer production

BACKGROUND

The action spectrum for bilirubin photodegradation has been intensively studied. However, questions still remain regarding which light wavelength most efficiently photodegrades bilirubin. In this study, we determined the in vitro effects of different irradiation wavelength ranges on bilirubin photodegradation.

METHODS

In our in vitro method, normalized absolute irradiance levels of 4.2 × 10¹⁵ photons/cm²/s from light-emitting diodes (ranging from 390-530 nm) and 10-nm band-pass filters were used to irradiate bilirubin solutions (25 mg/dL in 4% human serum albumin). Bilirubin and its major photoisomer concentrations were determined; the half-life time of bilirubin (t_1/2) was calculated for each wavelength range, and the spectral characteristics for bilirubin photodegradation products were obtained for key wavelengths.

RESULTS

The in vitro photodegradation of bilirubin at 37 °C decreased linearly as the wavelength was increased from 390 to 500 nm with t_1/2 decreasing from 63 to 17 min, respectively. At 460 ± 10 nm, a significantly lower rate of photodegradation and thus higher t_1/2 (31 min) than that at 500 nm (17 min) was demonstrated.

CONCLUSION

In our system, the optimum bilirubin photodegradation and lumirubin production rates occurred between 490 and 500 nm. Spectra shapes were remarkably similar, suggesting that lumirubin production was the major process of bilirubin photodegradation.

Changes in total serum bilirubin during phototherapy in late preterm and term infants with non-haemolytic hyperbilirubinemia

BACKGROUND

There is no standardized method for total serum bilirubin (TSB) monitoring during phototherapy for neonatal hyperbilirubinemia and national guidelines give heterogeneous indications.

AIM

To assess the hypothesis that TSB values do not exceed exsanguino-transfusion (EXT) threshold during phototherapy and that it is possible to decrease its monitoring frequency in jaundiced infants.

STUDY DESIGN

We carried out a prospective observational study in which changes in TSB during phototherapy for non-haemolytic hyperbilirubinemia were recorded in a cohort of late preterm and term infants. TSB values after 6, 12, 18, and 24 h of phototherapy were compared to the EXT threshold matched to infants' gestational and postnatal age according to the specific nomogram of the Italian Society of Neonatology guidelines.

RESULTS

We studied 105 infants who started phototherapy at a mean age of 89 ± 37 h when mean TSB was 17.1 ± 2.5 mg/dL. We found that TSB decreased during phototherapy and the difference between mean TSB and EXT threshold progressively increased during phototherapy; TSB exceeded EXT threshold in none of our patients (0%).

CONCLUSIONS

Our study demonstrates that differences between mean TSB and EXT threshold increased during phototherapy in late preterm and term infants with non-haemolytic hyperbilirubinemia; in none of our patients TSB exceeded EXT threshold. Our findings support the possibility of safely decreasing TSB monitoring during phototherapy, thus limiting noxious painful stimuli in neonates.

Double versus single intensive phototherapy with LEDs in treatment of neonatal hyperbilirubinemia

OBJECTIVE

We investigate whether double phototherapy reduces total serum bilirubin concentration faster than single light during intensive phototherapy with high levels of irradiance using light-emitting diodes.

STUDY DESIGN

Eighty-three infants with gestational age ⩾33 weeks and uncomplicated hyperbilirubinemia were randomized to either double (n=41) or single phototherapy (n=42) for 24 h. The mean irradiance was 64.8 μW cm^-2 nm^-1 from above and 39 μW cm^-2 nm^-1 from below.

RESULTS

The percentage decreases of total serum bilirubin after 12 h of double vs single phototherapy were (mean (95% confidence interval (CI))) 39% (37 to 42) vs 30% (27 to 32), respectively (P<0.001). After 24 h, the decreases were 58% (56 to 61) vs 47% (44 to 50), respectively (P<0.001). The results were still significant after adjustment for confounding. The only side effect was loose stools.

CONCLUSION

Even with intensive phototherapy increasing spectral power by increasing the irradiated body surface area, the efficacy of phototherapy is improved.

The impact of hemoglobin on the efficacy of phototherapy in hyperbilirubinemic infants

BackgroundPhototherapy is the routine treatment for neonatal hyperbilirubinemia. Absorption of light in the skin transforms the native Z,Z-bilirubin to photobilirubins. This study investigates whether the hemoglobin concentration has an impact on efficacy of phototherapy, expressed by the decline of total serum bilirubin concentration (TsB).MethodsA trial was conducted on 93 infants, gestational age ≥33 weeks, with uncomplicated hyperbilirubinemia. The infants were treated with conventional phototherapy using LED light for 24 h. The median light irradiance was 66.8 μW/cm²/nm.ResultsThe median decrease in TsB after 24 h was 121 (57-199) μmol/l; the median hemoglobin was 12.0 (7.0-14.7) mmol/l. There was a significant effect of hemoglobin concentration on the decrease in TsB of -3.61 μmol/mmol hemoglobin (P=0.022), after adjusting for initial TsB and postnatal age. That is, assuming the same initial TsB and postnatal age, for each mmol/l increase in hemoglobin, the decrease in TsB was 3.61 μmol/l smaller. In our hemoglobin range, the decrease in TsB is reduced by 28 μmol/l (23%).ConclusionIncreasing hemoglobin levels led to a decrease in the efficacy of phototherapy. Our data provide additional support for the conclusion that the transformation of bilirubin to photobilirubins takes place mainly in the superficial capillaries of the skin.

Efficient Photocatalytic Bilirubin Removal over the Biocompatible Core/Shell P25/g-C3N4 Heterojunctions with Metal-free Exposed Surfaces under Moderate Green Light Irradiation

Highly-monodispersed g-C₃N₄/TiO₂ hybrids with a core/shell structure were synthesized from a simple room temperature impregnation method, in which g-C₃N₄ was coated through self-assembly on the commercially available Degussa P25 TiO₂ nanoparticles. Structural and surface characterizations showed that the presence of g-C₃N₄ notably affected the light absorption characteristics of TiO₂. The g-C₃N₄/TiO₂ heterojunctions with metal-free exposed surfaces were directly used as biocompatible photocatalysts for simulated jaundice phototherapy under low-power green-light irradiation. The photocatalytic activity and stability of g-C₃N₄/TiO₂ were enhanced relative to pure P25 or g-C₃N₄, which could be ascribed to the effective Z-scheme separation of photo-induced charge carriers in g-C₃N₄/TiO₂ heterojunction. The photoactivity was maximized in the 4 wt.% g-C₃N₄-coated P25, as the bilirubin removal rate under green light irradiation was more than 5-fold higher than that under the clinically-used blue light without any photocatalyst. This study approves the future applications of the photocatalyst-assisted bilirubin removal in jaundice treatment under moderate green light which is more tolerable by humans.