Quantum yields for laser photocyclization of bilirubin in the presence of human serum albumin. Dependence of quantum yield on excitation wavelength

SpeCamX: mobile app that turns unmodified smartphones into multispectral imagers

We present the development of SpeCamX, a mobile application that enables an unmodified smartphone into a multispectral imager. Multispectral imaging provides detailed spectral information about objects or scenes, but its accessibility has been limited due to its specialized requirements for the device. SpeCamX overcomes this limitation by utilizing the RGB photographs captured by smartphones and converting them into multispectral images spanning a range of 420 to 680 nm without a need for internal modifications or external attachments. The app also includes plugin functions for extracting medical information from the resulting multispectral data cube. In a clinical study, SpeCamX was used to implement an augmented smartphone bilirubinometer, predicting blood bilirubin levels (BBL) with superior performance in accuracy, efficiency and stability compared to default smartphone cameras. This innovative technology democratizes multispectral imaging, making it accessible to a wider audience and opening new possibilities for both medical and non-medical applications.

Blue-Green (~480 nm) versus Blue (~460 nm) Light for Newborn Phototherapy-Safety Considerations

We have previously shown that the phototherapy of hyperbilirubinemic neonates using blue-green LED light with a peak wavelength of ~478 nm is 31% more efficient for removing unconjugated bilirubin from circulation than blue LED light with a peak wavelength of ~452 nm. Based on these results, we recommended that the phototherapy of hyperbilirubinemic newborns be practiced with light of ~480 nm. Aim: Identify and discuss the most prominent potential changes that have been observed in the health effects of phototherapy using either blue fluorescent- or blue LED light and speculate on the expected effects of changing to blue-green LED light phototherapy. Search the phototherapy literature using the terms neonate, hyperbilirubinemia, and phototherapy in the PubMed and Embase databases. Transitioning from blue fluorescent light to blue-green LED light will expose neonates to less light in the 400-450 nm spectral range, potentially leading to less photo-oxidation and geno-/cytotoxicity, reduced risk of cancer, and decreased mortality in extremely low-birthweight neonates. The riboflavin level may decline, and the increased production and retention of bronze pigments may occur in predisposed neonates due to enhanced lumirubin formation. The production of pre-inflammatory cytokines may rise. Hemodynamic responses and transepidermal water loss are less likely to occur. The risk of hyperthermia may decrease with the use of blue-green LED light and the risk of hypothermia may increase. Parent-neonate attachment and breastfeeding will be positively affected because of the shortened duration of phototherapy. The latter may also lead to a significant reduction in the cost of phototherapy procedures as well as the hospitalization process.

Action spectrum of phototherapy in hyperbilirubinemic neonates

BACKGROUND

Phototherapy with blue light matching plasma absorption spectrum of the bilirubin-albumin complex with peak at 460 nm is standard treatment of neonatal hyperbilirubinemia.

AIM

To demonstrate clinically the action (efficacy) spectrum of phototherapy in hyperbilirubinemic neonates, through determination of the fraction of total serum bilirubin (TSB) decreased by phototherapy with peak emission wavelengths ≥478 nm (blue-green) compared with that of light of 459/452 nm (blue).

METHODS

TSB values were compiled from three earlier trials, in which hyperbilirubinemic neonates were randomized to receive 24 h of either blue-green light (478/490/497 nm) (intervention groups) or blue light (459/452/459 nm) (control groups) with equal irradiance and exposed body surface areas. Ratios (efficacy) between the decrease in TSB between intervention and control groups were calculated and graphed versus peak wavelengths, demonstrating the course of the action spectrum.

RESULTS

Calculated efficacy ratios were 1.31, 1.18, and 1.04 for light with peak wavelengths of 478, 490, and 497 nm, respectively. The action spectrum increases from 452/459 to maximum at 478 nm, from where it decreases to 1.18 and finally to 1.04.

CONCLUSION

For optimal phototherapeutic treatment, neonates need to be exposed to light with peak wavelength some 20 nm longer than is presently used.

IMPACT

The action (efficacy) spectrum of phototherapy for hyperbilirubinemic neonates has its peak wavelength at 478 nm. The peak wavelength of this action spectrum is 20 nm longer than the wavelength presently believed to be most efficient. The peak is also different from the peak found in vitro. For optimal phototherapeutic effect, neonates need to be treated with light of wavelengths some 20 nm longer than are presently used.

Microfluidic photoreactor to treat neonatal jaundice

While in most cases, jaundice can be effectively treated using phototherapy, severe cases require exchange transfusion, a relatively risky procedure in which the neonate's bilirubin-rich blood is replaced with donor blood. Here, we examine extracorporeal blood treatment in a microfluidic photoreactor as an alternative to exchange transfusion. This new treatment approach relies on the same principle as phototherapy but leverages microfluidics to speed up bilirubin removal. Our results demonstrate that high-intensity light at 470 nm can be used to rapidly reduce bilirubin levels without causing appreciable damage to DNA in blood cells. Light at 470 nm was more effective than light at 505 nm. Studies in Gunn rats show that photoreactor treatment for 4 h significantly reduces bilirubin levels, similar to the bilirubin reduction observed for exchange transfusion and on a similar time scale. Predictions for human neonates demonstrate that this new treatment approach is expected to exceed the performance of exchange transfusion using a low blood flow rate and priming volume, which will facilitate vascular access and improve safety.

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.

Standardization of phototherapy for neonatal hyperbilirubinemia using multiple-wavelength irradiance integration

BACKGROUND

Phototherapy with radiation of 460-490 nm wavelengths provides the most potent therapeutic effect for neonatal jaundice. However, the efficacy of phototherapy has been estimated using single-wavelength detectors with sensitivity at approximately 460 nm. Cyclobilirubin formation capacity (CFC), which comprises the sum of the irradiance values from three wavelengths multiplied by their specific coefficients, has been proposed as an alternative marker to evaluate the efficacy of phototherapy. This study aimed to test whether two types of phototherapy devices with distinct spectral characteristics provide similar therapeutic effects on adjustment of device-to-patient distances to deliver similar CFCs.

METHODS

Using a three-wavelength spectroradiometer, CFCs and footprints of the light-emitting diode and fluorescent tube devices were assessed. Having determined the device-specific distances that ensured similar CFCs, 32 newborn infants, requiring phototherapy for hyperbilirubinemia, were randomized into the light-emitting diode and fluorescent tube groups. The total serum bilirubin levels before and after phototherapy were assessed.

RESULTS

The light-emitting diode and fluorescent tube devices had comparable CFCs at distances of 60 and 50 cm, respectively. Phototherapy reduced the total serum bilirubin levels from 18.1 to 14.6 mg/dL and from 19.1 to 15.1 mg/dL in the light-emitting diode and fluorescent tube groups, respectively. The two groups did not differ significantly with respect to the patients' clinical backgrounds, serum bilirubin levels, or changes before and after phototherapy.

CONCLUSION

At similar CFCs, the two phototherapy devices reduced the total serum bilirubin levels by comparable amounts. Hence, determining CFCs may help predict phototherapy efficacy. This may ensure better safety and greater efficacy of the treatment for newborn infants.

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.

Phototherapy for neonatal hyperbilirubinemia

Approximately 60 years ago in England, phototherapy for neonatal hyperbilirubinemia was used in clinical practice. It was introduced in Japan approximately 50 years ago. At that time, the mechanism underlying the serum bilirubin concentration decrease by phototherapy was still unknown. The mechanism was identified by chemists, biochemists, and pediatricians. Clarification started with the report that unconjugated bilirubin was excreted into bile after photoirradiation in Gunn rats. After confirmation of the molecular structure of bilirubin on X-ray analysis, the mechanism for bile excretion of unconjugated bilirubin was verified based on geometric configurational photoisomers in the Gunn rat. Finally, the reaction and excretion of structural bilirubin photoisomers was proved to be the main mechanism for the decrease in serum bilirubin during phototherapy for neonatal hyperbilirubinemia, which differs from the mechanism in the Gunn rat. The most effective and safest light source and the optimal method to evaluate phototherapy, however, remain unknown. Moreover, as for bronze baby syndrome, which is a well-known adverse reaction to phototherapy, the etiology is unclear. Hence, we review phototherapy for hyperbilirubinemia including a fundamental understanding of the bilirubin photochemical reactions, and discuss the subclinical carcinogenic risk of phototherapy and the increased mortality rate of extremely low-birthweight infants due to aggressive phototherapy, which is becoming an increasing problem.

Bilirubin isomer distribution in jaundiced neonates during phototherapy with LED light centered at 497 nm (turquoise) vs. 459 nm (blue)

BACKGROUND

Phototherapy using blue light is the treatment of choice worldwide for neonatal hyperbilirubinemia. However, treatment with turquoise light may be a desirable alternative. Therefore, the aim of this randomized, controlled study was to compare the bilirubin isomer distribution in serum of jaundiced neonates after 24 h of therapy with narrow-band (LED) light centered at 497 nm (turquoise) vs. 459 nm (blue), of essentially equal irradiance.

MATERIALS

Eighty-three neonates (≥33 wk gestational age) with uncomplicated hyperbilirubinemia were included in the study. Forty neonates were exposed to light centered at 497 nm and 43 infants with light centered at 459 nm. Irradiances were 5.2 × 10(15) and 5.1 × 10(15) photons/cm(2)/s, respectively.

RESULTS

After 24 h of treatment no significant differences in serum concentrations of total bilirubin isomers and Z,Z-bilirubin were observed between the 2 groups. Interestingly, concentrations of Z,E-bilirubin, and thus also total bilirubin isomers formed during therapy, were highest for infants receiving light centered at 459 nm, while the concentration of E,Z-bilirubin was highest for those receiving light centered at 497 nm. No significant difference was found between concentrations of E,Z-lumirubin.

CONCLUSION

Therapy with LED light centered at 497 nm vs. 459 nm, applied with equal irradiance on the infants, resulted in a different distribution of bilirubin isomers in serum.

A Pharmacologic View of Phototherapy

A pharmacologic view of phototherapy for neonatal jaundice is presented. By considering the photons of therapy light as molecules of a drug, this view connects therapeutic efficacy with photon wavelength, photon dose, dose rate and regimen, efficiency of photon absorption by bilirubin, quantum yields of photoproducts, and their metabolic courses. Based on this view, recommendations to ultimately improve efficacy and safety are presented. Special attention is given to phototherapy regimens for low gestational age, low birthweight infants.

Effect of phototherapy with turquoise vs. blue LED light of equal irradiance in jaundiced neonates

BACKGROUND

Blue light with peak emission around 460 nm is the preferred treatment of neonatal hyperbilirubinemia. However, studies using fluorescent light tubes have suggested that turquoise light with peak emission at 490 nm may be more efficient. At present, the predominant light source for phototherapy is light emitting diodes (LEDs). Hence, the aim of this study was to compare the bilirubin-reducing effect in jaundiced neonates treated either with turquoise or with blue LED light with peak emission at 497 or 459 nm, respectively, with equal irradiance on the infants.

METHODS

Infants with gestational age ≥33 wk and uncomplicated hyperbilirubinemia were randomized to either turquoise or blue LED light and were treated for 24 h. The mean irradiance footprint at skin level was 5.2 × 10(15) and 5.1 × 10(15) photons/cm(2)/s, respectively.

RESULTS

Forty-six infants received turquoise light and 45 received blue light. The median (95% confidence interval) decrease of total serum bilirubin was 35.3% (32.5; 37.3) and 33.1% (27.1; 36.8) for infants treated with turquoise and blue lights, respectively. The difference was nonsignificant (P = 0.53). The decrease was positively correlated to postnatal age and negatively to birth weight.

CONCLUSION

Using LED light of equal irradiance, turquoise and blue lights had equal bilirubin-reducing effect on hyperbilirubinemia of neonates.

The Biological Effects of Bilirubin Photoisomers

Although phototherapy was introduced as early as 1950’s, the potential biological effects of bilirubin photoisomers (PI) generated during phototherapy remain unclear. The aim of our study was to isolate bilirubin PI in their pure forms and to assess their biological effects in vitro. The three major bilirubin PI (ZE- and EZ-bilirubin and Z-lumirubin) were prepared by photo-irradiation of unconjugated bilirubin. The individual photoproducts were chromatographically separated (TLC, HPLC), and their identities verified by mass spectrometry. The role of Z-lumirubin (the principle bilirubin PI) on the dissociation of bilirubin from albumin was tested by several methods: peroxidase, fluorescence quenching, and circular dichroism. The biological effects of major bilirubin PI (cell viability, expression of selected genes, cell cycle progression) were tested on the SH-SY5Y human neuroblastoma cell line. Lumirubin was found to have a binding site on human serum albumin, in the subdomain IB (or at a close distance to it); and thus, different from that of bilirubin. Its binding constant to albumin was much lower when compared with bilirubin, and lumirubin did not affect the level of unbound bilirubin (Bf). Compared to unconjugated bilirubin, bilirubin PI did not have any effect on either SH-SY5Y cell viability, the expression of genes involved in bilirubin metabolism or cell cycle progression, nor in modulation of the cell cycle phase. The principle bilirubin PI do not interfere with bilirubin albumin binding, and do not exert any toxic effect on human neuroblastoma cells.

The effects of phototherapy on eosinophil and eosinophilic cationic protein in newborns with hyperbilirubinemia

Newborns with jaundice requiring or not requiring phototherapy (PT) are at greater risk of developing asthma later in life. In this study, we investigated the effect of PT treatment on eosinophil and eosinophilic cationic protein (ECP) levels in newborns with severe hyperbilirubinemia. Thirty newborns diagnosed with severe hyperbilirubinemia and exposed to light-emitting diode (LED) PT were enrolled into the study. Total serum bilirubin (TSB) levels, complete blood count and serum ECP concentrations were measured before and after PT. TSB and hemoglobin (Hb) counts were lower after PT (p = 0.001). There was no difference between leukocyte, lymphocyte, neutrophil and platelet count before and after PT. Eosinophil levels were increased after PT, although not significantly. ECP levels were higher after PT (p = 0.006). It may be speculated that newborns treated with LED PT, increased ECP might play a role in developing allergic diseases later in life.

Fluorescence excitation spectrum of bilirubin in blood: a model for the action spectrum for phototherapy of neonatal jaundice

A recent report (Lamola et al. 2013 Pediatric Research, 74, 54-60) presents a semiempirical model for facile calculation of an action spectrum for bilirubin photochemistry in vivo using the most current knowledge of the optics of neonatal skin. The calculations indicate that competition for phototherapy light by hemoglobin in the skin is the predominant factor that defines the spectrum of light absorbed by bilirubin. If the latter is correct, a valid physical analog of the calculated spectrum is the excitation spectrum of bilirubin in blood. The fluorescence excitation spectrum was recorded and, indeed, found to be very similar to the calculated spectrum. Both spectra exhibit maxima near 476 nm and widths at half height of about 50 nm. This result supports the conclusion that light between 460 and 490 nm is most effective for phototherapy of neonatal jaundice.

The effect of hematocrit on the efficacy of phototherapy for neonatal jaundice

BACKGROUND

The therapeutic phototherapy action spectrum ranges from 420 to 500 nm. However, a recent report of improved efficacy of fluorescent "turquoise" light (~490 nm) as compared with blue light (~450 nm) underscores the need to define an optimal action spectrum for precision-targeted phototherapy using very narrow wavelength ranges.

METHODS

We used a current semi-empirical model of the optical properties of skin for robust calculations of the fraction of light absorbed by bilirubin at various wavelengths that could be confounded by hemoglobin (Hb), melanin, and skin thickness. Applying assumptions regarding the wavelength dependence of bilirubin photochemistry, "action spectra" were assembled from the calculated values.

RESULTS

All the calculated action spectra displayed a peak between 472 and 480 nm (most at 476 nm), which is a significant shift from the well-reported 460 nm absorption peak of bilirubin. Of note, the relative amplitudes of the action spectra showed an inverse relationship with hematocrit (Hct).

CONCLUSION

We speculate that a narrow range of light at 476 nm would be 60% more effective than blue (broadband) fluorescent lamps. Because Hb serves as a major competitor of bilirubin for light absorption, the calculations also predict that the efficacy of phototherapy is dependent on the Hct. A high Hct could reduce therapeutic efficiency.

Efficacy of light-emitting diode versus other light sources for treatment of neonatal hyperbilirubinemia: a systematic review and meta-analysis

Various light-emitting diode (LED) phototherapy devices have been trialled on the assumption of a more effective spectral distribution of the light emitted. We reviewed the current literature to determine whether LED is more effective than other types of phototherapy. Eligible studies were randomized controlled trials of LED versus other phototherapies. Studies were found to be of medium quality based on a components approach. Data were statistically aggregated within a very homogeneous population (term or late preterm neonates). Results appeared robust at sensitivity analysis. Five hundred and eleven neonates were included in the meta-analysis. LED and other phototherapy devices appeared to be equally effective in reducing total serum bilirubin (TSB) in term or late preterm neonates. The pooled mean TSB rate of decrease was 3.269 μmol/L/h (0.191 mg/dL/h) and 3.074 μmol/L/h (0.18 mg/dL/h) in the LED and conventional arms, respectively [average difference in TSB rate of decrease = 0.194 μmol/L/h (0.011 mg/dL/h) in favour of LED phototherapy; p = 0.378].

CONCLUSION

No significant difference in TSB rate of decrease was detected between LED and other types of phototherapy. Further randomized controlled trials are needed to ascertain whether LED phototherapy may be more effective when increasing the spectral power, or in certain selected subpopulations.

Phototherapy to prevent severe neonatal hyperbilirubinemia in the newborn infant 35 or more weeks of gestation

OBJECTIVE

To standardize the use of phototherapy consistent with the American Academy of Pediatrics clinical practice guideline for the management of hyperbilirubinemia in the newborn infant 35 or more weeks of gestation.

METHODS

Relevant literature was reviewed. Phototherapy devices currently marketed in the United States that incorporate fluorescent, halogen, fiber-optic, or blue light-emitting diode light sources were assessed in the laboratory.

RESULTS

The efficacy of phototherapy units varies widely because of differences in light source and configuration. The following characteristics of a device contribute to its effectiveness: (1) emission of light in the blue-to-green range that overlaps the in vivo plasma bilirubin absorption spectrum (~460-490 nm); (2) irradiance of at least 30 μW · cm(-2) · nm(-1) (confirmed with an appropriate irradiance meter calibrated over the appropriate wavelength range); (3) illumination of maximal body surface; and (4) demonstration of a decrease in total bilirubin concentrations during the first 4 to 6 hours of exposure. RECOMMENDATIONS (SEE APPENDIX FOR GRADING DEFINITION): The intensity and spectral output of phototherapy devices is useful in predicting potential effectiveness in treating hyperbilirubinemia (group B recommendation). Clinical effectiveness should be evaluated before and monitored during use (group B recommendation). Blocking the light source or reducing exposed body surface should be avoided (group B recommendation). Standardization of irradiance meters, improvements in device design, and lower-upper limits of light intensity for phototherapy units merit further study. Comparing the in vivo performance of devices is not practical, in general, and alternative procedures need to be explored.

Early isomerization of bilirubin in phototherapy of neonatal jaundice

Neonatal jaundice is usually treated with phototherapy that converts bilirubin to more polar stereoisomers. These should theoretically be less able to cross the blood-brain barrier. The rates of photoisomer formation and concentrations accumulating in the circulation may have a bearing on the risk of kernicterus. The purpose of this study was to determine the rate of appearance of the major 4Z, 15E photoisomer of bilirubin during the early stages of phototherapy. Twenty jaundiced neonates were treated with phototherapy, and blood samples were drawn before and at approximately 15, 30, 60, and 120 min (10 infants) or at approximately 15, 60, 120, and 240 min (10 infants) after beginning phototherapy. Blood samples were analyzed for total serum bilirubin (TSB) and the 4Z, 15E photoisomer of bilirubin. Significant (p<0.0001) formation of the 4Z, 15E photoisomer was detectable within 15 min. The change in TSB from time 0 was insignificant at 120 min but reached significance at 240 min (p<0.001). The 4Z, 15E bilirubin constituted up to 20-25% of TSB at 2 h and may not have peaked by 4 h. Further studies are needed to determine whether this early shift in balance between bilirubin isomers with different polarities may impact the risk of bilirubin encephalopathy even before TSB starts to fall.

Photoisomers: obfuscating factors in clinical peroxidase measurements of unbound bilirubin?

OBJECTIVES

The objectives of the study were to measure the effect of 4Z,15E-bilirubin on peroxidase free bilirubin measurements and to review the literature on this topic.

METHODS

4Z,15E-Bilirubin was generated in situ in serum or serum albumin solution through controlled irradiation of isomerically pure 4Z,15Z-bilirubin IXalpha, under conditions in which the total amount of bilirubin remained constant. Reactions were monitored by difference spectroscopy, to ensure that solutions were not irradiated beyond the initial photostationary state and that concentrations of other isomers were kept to a minimum. Prepared in this way, 10% to 25% of the total bilirubin in the final solutions was in the form of the 4Z,15E-isomer. Free bilirubin in the solutions was measured with a peroxidase method, before and after irradiation. The use of bovine serum albumin as a surrogate for human albumin in in vitro studies also was investigated.

RESULTS

The findings of previous studies are not altogether consistent, with a common flaw in several being the failure to measure photoisomer concentrations. For bilirubin in serum albumin solution, conversion of approximately 25% of the 4Z,15Z-isomer to 4Z,15E-bilirubin led to a much smaller decrease (<20%) in the apparent free bilirubin concentration; for bilirubin in serum, conversion of approximately 15% of the 4Z,15Z-isomer to photoisomers resulted in a much larger increase ( approximately 40%). Irradiation of bilirubin in bovine serum albumin solution generated a very different array of photoisomers than that observed in human albumin solutions.

CONCLUSIONS

The effect of photoisomers on the accuracy and specificity of free 4Z,15Z-bilirubin measurements remains uncertain. In a clinical setting, free bilirubin measurements need to be interpreted with caution when samples contain photoisomers. Irradiated bovine albumin solutions of isomerically impure bilirubin used in previous studies are poor models for investigating the effects of phototherapy in humans and the albumin binding of photoisomers.

Randomized controlled trial of light-emitting diode phototherapy

OBJECTIVE

We wished to compare the efficacy of light-emitting diode (LED) phototherapy with special blue fluorescent (BB) tube phototherapy in the treatment of neonatal hyperbilirubinemia.

STUDY DESIGN

We randomly assigned 66 infants >or=35 weeks of gestation to receive phototherapy using an LED device or BB. In addition to phototherapy from above, all infants also received phototherapy from below using four BB tubes or a fiberoptic pad.

RESULT

After 15+/-5 h of phototherapy, the rate of decline in the total serum bilirubin (TSB) was 0.35+/-0.25 mg/dl/h in the LED group vs 0.27+/-0.25 mg/dl/h in the BB group (P=0.20).

CONCLUSION

LED phototherapy is as effective as BB phototherapy in lowering serum bilirubin levels in term and near-term newborns.

Therapeutic effect of turquoise versus blue light with equal irradiance in preterm infants with jaundice

AIM

To compare the efficiency of turquoise light with that of TL52 blue in treatment of preterm infants with jaundice at the same level of body irradiance.

METHODS

Infants with gestational age 28-37 weeks and non-haemolytic hyperbilirubinemia were treated for 24 h with either turquoise light (OSRAM L18W/860 fluorescent lamps) or blue light (Philips TL20W/52 fluorescent lamps). The concentrations of serum total bilirubin and bilirubin isomers were measured by the Vitros routine method and by HPLC, respectively.

RESULTS

The decrease in serum concentrations of total bilirubin, total bilirubin isomers and the toxic Z,Z-bilirubin was greatest for infants treated with turquoise light. Further, the increase in Z,E-bilirubin was smaller and there was a trend towards a higher rise in E,Z-bilirubin.

CONCLUSIONS

Turquoise light has a greater bilirubin reducing effect than TL52 blue light with equal irradiance, expressed both by serum total bilirubin, total bilirubin isomers and Z,Z-bilirubin, i.e. the turquoise spectral range is more efficient than the blue. This is in accordance with deeper penetration into the skin, lower production of the Z,E-bilirubin and greater production of E,Z-bilirubin and lumirubin, in infants under turquoise light. This suggests, given equal irradiances, that light in the turquoise spectral range is preferable to the TL52 blue in treatment of newborn jaundiced infants.

Formation of photoproducts and cytotoxicity of bilirubin irradiated with turquoise and blue phototherapy light

AIM

To compare a new turquoise ("green") fluorescent phototherapy lamp (490 nm) with a conventional blue phototherapy lamp (450 nm) with respect to cytotoxicity and photochemical effects of bilirubin.

METHODS

Mouse lymphoma cells (L5178Y-R) in the presence of bilirubin solutions were exposed to phototherapy light. Occurrence of necrosis and apoptosis, reduction of mitotic index and inhibited cell growth was assayed by appropriate methods. The presence of bilirubin and its photoisomers was measured by high-pressure liquid chromatography analysis and absorption spectroscopy.

RESULTS

At constant and equal light irradiances, the cytotoxic effects in the presence of bilirubin bound to human serum albumin showed that the green lamp caused significantly less necrosis (n = 4, p < 0.05) and less inhibition of cell multiplication (n = 3, p < 0.05) than the blue lamp. A slightly lower apoptotic fraction, although not statistically significant, was observed in cells exposed to the blue lamp. Photo-oxidation of bilirubin was more prominent with blue light irradiation. The photoequilibria between geometric isomers of bilirubin were different for the two lamps; more geometric photoisomers were formed by blue irradiation (n = 6, p < 0.05). The amounts of the most water-soluble isomers (presumably mainly lumirubin) were rather similar for the two lamps.

CONCLUSION

The two lamps were similar in the formation of therapeutically relevant photoproducts, but the blue lamp showed potential in forming more photo-oxidation products and in causing more severe cellular damage in the presence of bilirubin.

A dynamic model for bilirubin binding to human serum albumin

Site-directed mutagenesis of human serum albumin was used to study the role of various amino acid residues in bilirubin binding. A comparison of thermodynamic, proteolytic, and x-ray crystallographic data from previous studies allowed a small number of amino acid residues in subdomain 2A to be selected as targets for substitution. The following recombinant human serum albumin species were synthesized in the yeast species Pichia pastoris: K195M, K199M, F211V, W214L, R218M, R222M, H242V, R257M, and wild type human serum albumin. The affinity of bilirubin was measured by two independent methods and found to be similar for all human serum albumin species. Examination of the absorption and circular dichroism spectra of bilirubin bound to its high affinity site revealed dramatic differences between the conformations of bilirubin bound to the above human serum albumin species. The absorption and circular dichroism spectra of bilirubin bound to the above human serum albumin species in aqueous solutions saturated with chloroform were also examined. The effect of certain amino acid substitutions on the conformation of bound bilirubin was altered by the addition of chloroform. In total, the present study suggests a dynamic, unusually flexible high affinity binding site for bilirubin on human serum albumin.

Effect of intravenous bilirubin infusion on biliary phospholipid secretion, hepatic P-glycoprotein expression, and biliary cytotoxicity in pigs

BACKGROUND

Infusion of large intravenous bilirubin loads in bile acid-depleted pigs reduces P-glycoprotein-dependent biliary phospholipid secretion and increases the cytotoxicity of bile. The reasons for the diminution of biliary phospholipid secretion and the increase in biliary cytotoxicity are not known. This study was undertaken to determine whether the bilirubin-induced lowering of biliary phospholipid secretion is associated with alterations in hepatic P-glycoprotein (P-gp) expression and to determine why bilirubin infusions increase biliary cytotoxicity.

METHODS

Hepatic bile was collected from bile acid-depleted pigs before and during intravenous bilirubin infusion. Hepatic P-gp expression was measured with protein blot analysis, using the P-gp-specific antibody C219. Biliary cytotoxicity was assayed against erythrocytes. The biliary phospholipid fatty acid profile was determined by means of gas chromatography.

RESULTS

Bilirubin infusions lowered biliary phospholipid secretion by 69% without changing hepatic P-gp expression, suggesting that bilirubin infusions have an inhibitory effect on hepatic P-gp activity. Bilirubin infusions did not cause P-gp losses into bile. An unequivocal, proportional relationship (r2 = 0.80) pertained between cytotoxicity and the bile acid to phospholipid ratio in bile secreted before and during bilirubin infusion and in phosphatidylcholine-supplemented bile. Unconjugated bilirubin in bile did not contribute to biliary cytotoxicity. Biliary phospholipids were always phosphatidylcholine >> phosphatidylethanolamine, mainly of C16:0, 18:2 and C16:0, 18:1 fatty acid configuration.

CONCLUSIONS

Intravenous bilirubin loads reduce biliary phospholipid secretion without changing hepatic P-gp expression. Bilirubin infusions increase biliary cytotoxicity by augmenting the biliary bile acid to phospholipid ratio.

Bilirubin photoisomerization products in serum and urine from a Crigler-Najjar type I patient treated by phototherapy

The relative compositions of the photoisomers of bilirubin-1X alpha (4Z, 15Z-bilirubin) in serum and urine of a patient with Crigler-Najjar type I syndrome treated by phototherapy are reported. High-performance liquid chromatography analysis reveals the presence of high serum levels of the configurational bilirubin photoisomer (4Z,15E-bilirubin) before the beginning of phototherapy (between 12 and 16% of the total bilirubin). The configurational photoisomer value increases during phototherapy with blue fluorescent lamps up to a photoequilibrium of about 25%, similar to that obtained in a bilirubin solution in vitro irradiated by the same lamps. This evidence suggests an inefficient serum excretion of the 4Z,15E-bilirubin. Indeed, its average half-life in serum of the Crigler-Najjar patient is found to be about 8 h. No detectable traces of the bilirubin structural isomer, lumirubin, are found in the serum. On the other hand, lumirubin represents the dominant bilirubin isomer excreted in the urine, as both 15Z and 15E configurations. Smaller amounts of 4Z,15E-bilirubin, 4E,15Z-bilirubin and native 4Z,15Z-bilirubin are observed in urine. The presence in urine of 4Z,15Z-bilirubin is probably due to a fast reversion of the configurational photoisomers to their native form. The half-life of the configurational photoisomers in urine kept at 38 degrees C is found to be of the order of a few minutes. Our study indicates that in Crigler-Najjar type I patients, mechanisms exist to excrete all bilirubin photoisomers. The lumirubin pathway seems to contribute markedly to bilirubin excretion in the urine, as occurs in jaundiced babies under phototherapy. However, the contribution of configurational isomers cannot be neglected.

Large intravenous loads of bilirubin photoconversion products, in contrast to bilirubin, do not cause cholestasis in bile acid-depleted pigs

BACKGROUND

Large intravenous bilirubin infusions in bile acid-depleted pigs (BADP) destroy hepatocyte canalicular membrane microvilli (CMV) and cause cholestasis. This study examines whether bilirubin photoconversion product infusions do the same.

METHODS

The effects of systemic infusion of 135 mumol.kg-1 body weight bilirubin photoconversion products on CMV density and choleretic response to intraportal bile acid infusion were studied in BADP. Furthermore, the effects of 135 mumol.kg-1 b.w. bilirubin infusion, either through an arteriovenous bilirubin photoconversion shunt device (PCD) or intravenously, were measured in PCD-connected BADP.

RESULTS

Intravenous bilirubin photoconversion product infusions affected neither the CMV density nor the choleretic response to cholic acid infusion, and neither did bilirubin infusion through the PCD. In contrast, intravenous bilirubin infusion caused canalicular injury and cholestasis in four of six PCD-connected BADP.

CONCLUSION

Bilirubin photoconversion products do not destroy CMV or cause cholestasis in BADP. A bilirubin photoconversion shunt device can confer cholestasis protection to bilirubin-loaded BADP.

Influence of photoisomers in bilirubin determinations on Kodak Ektachem and Hitachi analysers in neonatal specimens study of the contribution of structural and configurational isomers

We compared data obtained with the Kodak Ektachem and Hitachi 717 Analysers and HPLC from 83 neonates under phototherapy. Total bilirubin values determined with the Kodak and Hitachi are in good agreement, but we observed a large discrepancy in the results for conjugated (Kodak) and direct (Hitachi) bilirubin. HPLC revealed that all the samples contained configurational isomers, while only 7.7% and 30.8% contained conjugated bilirubin and structural isomers, respectively. We developed a device for the specific and quantitative production of configurational or structural isomers, by irradiation with blue or green light. In vitro, total bilirubin values are coherent for the routine analysers in the presence of configurational or structural isomers. With configurational isomers, unconjugated bilirubin (Kodak) is lower than total bilirubin (Kodak), and conjugated bilirubin (Kodak) is always equal to zero, so the apparatus gives a false positive response for delta bilirubin. In contrast, the direct bilirubin (Hitachi) is constant. Furthermore, in the presence of structural isomers, unconjugated bilirubin (Kodak) is unexpectedly higher than total bilirubin (Kodak), conjugated bilirubin (Kodak) is proportional to the quantity of these isomers, and direct bilirubin (Hitachi) is constant. The contribution of photoisomers in bilirubin measurements is discussed.

Cells, bilirubin and light: formation of bilirubin photoproducts and cellular damage at defined wavelengths

Cultured cells from one human and one murine cell line were treated with bilirubin and irradiated with visible light of different wavelengths, either from phototherapy lamps or from a Xenon/Mercury lamp equipped with a monochromator. Bilirubin bound to human serum albumin was also irradiated with light. After irradiation, the bilirubin and its photoisomers were extracted and analysed with High Pressure Liquid Chromatography. The formation of single strand breaks in the DNA of treated cells was studied using a fluorescence marker. Cytotoxicity in the mouse skin cell line was measured by loss of the ability to form visible colonies in vitro. Green light exposure favours the production of lumirubin, while blue light causes more DNA damage and cytotoxicity. Green light may be more efficient and safer than shorter wavelength exposure when treating jaundiced newborns with phototherapy.

Quantum yield and skin filtering effects on the formation rate of lumirubin

Photocyclization of bilirubin to lumirubin in the skin of jaundiced infants exposed to blue-green light irradiation is considered to be the most important process for bilirubin elimination from the organism. The quantum yield phi LR of the bilirubin-->lumirubin photoreaction has been recently measured and found to vary with the excitation wavelength, with a peak at about 520 nm. The quantum yield phi ZE for the strongly competing reversible configurational photoisomerization of bilirubin has also been recently shown to be wavelength dependent and to decrease significantly in the long-wavelength part of the absorption band of bilirubin. These new data are taken into account to model the bilirubin photochemistry in vivo by using a simplified skin optical model based on the Kubelka-Munk theory. The rate kappa LR of formation of lumirubin has been evaluated for the case of a four-layer skin and for monochromatic and narrow-band coloured fluorescent lamps. The effects of long-wavelength increase in phi LR, decrease in phi ZE and skin optical losses all combine to shift significantly the optimal rate of formation of lumirubin towards the green. These results suggest that a significant improvement in phototherapy might be obtained with the introduction of new lamps emitting in the blue-green spectral region between 490 and 510 nm.

Evaluation of the quantum yield for E-->Z isomerization of bilirubin bound to human serum albumin. Evidence of internal conversion processes competing with configurational photoisomerization

The quantum yield (phi zz) for the E--> photoisomerization of bilirubin (BR) bound to human serum albumin (HSA) under laser light irradiation has been evaluated with absorbance spectroscopy implemented by the high-performance liquid chromatography technique. The value at 458 nm is about 0.2, four times smaller than the value previously reported in the literature. As for the Z-->E configurational and the structural photoisomerization processes, the quantum yield varies with excitation wavelength, from 0.23 in the blue to 0.16 in the green. The sum of the quantum yields of the Z<-->E configurational photoisomerization reactions is 0.2-0.3 in the blue-green spectral region, thus giving direct evidence of the existence of internal conversion processes of the BR-HSA complex which compete with configurational photoisomerization. An evaluation of the quantum yields of the Z<-->E reactions for filtered broad-band light excitation in the 390-530 nm spectral region from data already published in the literature is also reported. Good agreement with our data of the quantum yields phi ZZ and phi ZE is found, despite the diversity of the experimental procedures in the two cases.

Bilirubin bound to cells does not form photoisomers

Cultured cells from one human and one murine cell line were incubated with bilirubin by different methods that allowed bilirubin to be bound to cells. The cells were irradiated with visible light of different wavelengths. Bilirubin bound to human serum albumin was also irradiated with light. After irradiation, bilirubin and its photoisomers were extracted and analyzed by HPLC. No photoisomers were found in samples of irradiated cells, while the types and amounts of photoisomers that were expected from the literature were found in samples of irradiated bilirubin/albumin mixtures. We conclude that the formation of therapeutically active photoisomers during phototherapy most probably does not take place in skin cells, but most likely in bilirubin bound to albumin in the vessels or in the interstitial space.

Wavelength-dependent quantum yield for Z----E isomerization of bilirubin complexed with human serum albumin

The quantum yield, phi ZE, for configurational photoisomerization (4Z,15Z----4Z,15E) of bilirubin bound non-covalently to human serum albumin was determined (at 23 +/- 2 degrees C) by laser excitation and chromatographic analysis of products. Values obtained for photoexcitation at 465 nm were about one-half those previously reported. The quantum yield was dependent on excitation wavelength, decreasing from a value of 0.109 +/- 0.010 for excitation at 457.9 nm to a value of 0.054 +/- 0.005 for excitation at 514.5 nm. The wavelength dependence is consistent with rapid transfer of excitation energy between the two non-identical pyrromethenone chromophores of bilirubin in the singlet excited state. Since the quantum yields for photoisomerization and luminescence of bilirubin bound to serum albumin at room temperature are both low, internal conversion processes, rather than Z----E configurational isomerizations, are probably the major pathways for deactivation of photo-excited bilirubin.

Quantum yields for the cyclization and configurational isomerization of 4E,15Z-bilirubin

Extraction of a solution of bilirubin configurational isomers in chloroform with an aqueous solution of human serum albumin was found to remove selectively the 4Z,15E-isomer. This phenomenon was used to develop a method for the purification of the 4E,15Z-isomer of bilirubin. The quantum yield for the cyclization and configurational isomerization of the 4E,15Z-isomer bound to a molar excess of human serum albumin was measured at 450 and 510 nm. The quantum yield for cyclization to form lumirubin was 0.12 and 0.19 at 450 and 510 nm, respectively. The quantum yield for configurational isomerization to form 4Z,15Z-bilirubin was 0.03 and 0.05 at 450 and 510 nm. An analysis of previously published data on the quantum yield for the formation of lumirubin from 4Z, 15Z-bilirubin bound to human serum albumin suggests that all of the formation of lumirubin may occur via consecutive photochemical processes with the 4E,15Z-isomer as an intermediate.

Single-strand breaks in the DNA of human cells exposed to visible light from phototherapy lamps in the presence and absence of bilirubin

Clinical evidence indicates that phototherapy of hyperbilirubinaemia in newborn infants is a safe and efficient form of therapy. The short-term side effects are not serious and seem to be well controlled. There are few long-term follow-up studies of phototherapy-treated infants. Therefore one cannot completely exclude the possibility that side effects can be found in future studies. With this background we undertook the present study of possible genotoxic effects of phototherapy. Human cells of the established glioblastoma cell line TMG-1 were used. The cells were exposed to visible light in the presence of different concentrations of bilirubin or in the absence of bilirubin. DNA was unwound in alkaline solution and the induction of strand breaks was assayed by a method taking advantage of the fluorescence from the dye Hoechst 33258. Blue light induced single-strand breaks in the DNA of cells in culture in the absence of bilirubin. During irradiation of bilirubin solutions with blue and green phototherapy light, long-lived toxic photoproducts were formed under in vitro conditions. At high and clinically relevant bilirubin concentrations, the effects of blue and green light were relatively similar. At low concentrations, there was a smaller effect of green light as expected from the absorption spectrum of bilirubin. It remains to be seen whether the genotoxic effect observed in the present studies can occur in vivo.

New trends in photobiology (invited review). Recent advances in bilirubin photophysics

The high photosensibility of bilirubin represents the main reason why neonatal jaundice is treated with light. The relaxation processes of excited bilirubin appear to be governed by complex mechanisms which are not fully known. At room temperature, radiationless channels, such as Z----E configurational photoisomerizations and internal conversions, contribute mostly to the deactivation of singlet excited bilirubin. Exciton coupling processes between the two pyrromethenone chromophores constituting the molecule may play a crucial role in bilirubin photophysics.