Influence of vitamins and food on the fluorescence spectrum of human urine

OBJECTIVES

Fluorescence spectroscopy of human urine is a method with the potential to gain importance as a diagnostic tool in the medical field, e.g., for measuring Coproporphyrin III (CPIII) as an indicator of cancer and acute types of porphyria. Food can change human urine's color, which could influence the urine fluorescence spectrum and the detection of CPIII in urine. To determine if there is a noticeable influence on the urine fluorescence spectrum or on the detection of CPIII in urine, 16 vitamin supplements, and three food items were tested. Such investigation may also prevent false interpretation of measured data.

METHODS

Urine samples were collected before and after (overnight, ca. 8 h) intake of each test substance. Samples were investigated by fluorescence spectrum analysis. At excitation wavelengths from 300 to 500 nm and emission wavelengths from 400 to 700 nm excitation-emission-matrices were measured. Data obtained from urine before intake were compared to the data from overnight urine. Furthermore, the investigation of any interference with the CPIII concentration was performed at an excitation wavelength of 407 ± 3 nm and emission wavelengths of 490-800 nm.

RESULTS

Only vitamin B2, but none of the other tested substances, showed noticeable influence on the urine fluorescence spectrum. None of the tested substances showed noticeable interference with the recovery rate of CPIII.

CONCLUSIONS

The correct interpretation of measured data by fluorescence spectroscopy is possible with the exception if vitamin B2 supplementation was performed; thus, the consumption of vitamin B2 supplements before fluorescence testing of the patient's urine should be avoided and/or must be requested. CPIII concentrations could reliably be measured in all cases.

Rational Design of Photosynthesis-Inspired Nanomedicines

The sun is the most abundant source of energy on earth. Phototrophs have discovered clever strategies to harvest this light energy and convert it to chemical energy for biomass production. This is achieved in light-harvesting complexes, or antennas, that funnel the exciton energy into the reaction centers. Antennas contain an array of chlorophylls, linear tetrapyrroles, and carotenoid pigments spatially controlled by neighboring proteins. This fine-tuned regulation of protein-pigment arrangements is crucial for survival in the conditions of both excess and extreme light deficit. Photomedicine and photodiagnosis have long been utilizing naturally derived and synthetic monomer dyes for imaging, photodynamic and photothermal therapy; however, the precise regulation of damage inflicted by these therapies requires more complex architectures. In this Account, we discuss how two mechanisms found in photosynthetic systems, photoprotection and light harvesting, have inspired scientists to create nanomedicines for more effective and precise phototherapies. Researchers have been recapitulating natural photoprotection mechanisms by utilizing carotenoids and other quencher molecules toward the design of photodynamic molecular beacons (PDT beacons) for disease-specific photoactivation. We highlight the seminal studies describing peptide-linked porphyrin-carotenoid PDT beacons, which are locally activated by a disease-specific enzyme. Examples of more advanced constructs include tumor-specific mRNA-activatable and polyionic cell-penetrating PDT beacons. An alternative approach toward harnessing photosynthetic processes for biomedical applications includes the design of various nanostructures. This Account will primarily focus on organic lipid-based micro- and nanoparticles. The phenomenon of nonphotochemical quenching, or excess energy release in the form of heat, has been widely explored in the context of porphyrin-containing nanomedicines. These quenched nanostructures can be implemented toward photoacoustic imaging and photothermal therapy. Upon nanostructure disruption, as a result of tissue accumulation and subsequent cell uptake, activatable fluorescence imaging and photodynamic therapy can be achieved. Alternatively, processes found in nature for light harvesting under dim conditions, such as in the deep sea, can be harnessed to maximize light absorption within the tissue. Specifically, high-ordered dye aggregation that results in a bathochromic shift and increased absorption has been exploited for the collection of more light with longer wavelengths, characterized by maximum tissue penetration. Overall, the profound understanding of photosynthetic systems combined with rapid development of nanotechnology has yielded a unique field of nature-inspired photomedicine, which holds promise toward more precise and effective phototherapies.

Triplet state spectra and dynamics of geometric isomers of carotenoids

The observation of preferential binding of cis-carotenoids in purple bacterial photosynthetic reaction centers versus trans-isomers in antenna pigment protein complexes has led to the hypothesis that the natural selection of stereoisomers has physiological significance. In order to test this hypothesis, we have undertaken a systematic series of investigations comparing the optical spectroscopic properties and excited state dynamics of cis and trans isomers of carotenoids. The present work compares the triplet state spectra, lifetimes, and energy transfer rates of all-trans-spheroidene and 13,14-locked-cis-spheroidene, the latter of which is incapable of isomerizing to the all-trans configuration, and therefore provides a unique opportunity to examine the triplet state properties of a structurally stable cis molecule. The data reveal only small differences in spectra, decay dynamics, and transfer times and suggest there is little intrinsic advantage in either triplet energy transfer or triplet state decay arising from the inherently different isomeric forms of cis compared to trans carotenoids.

The design and synthesis of artificial photosynthetic antennas, reaction centres and membranes

Artificial antenna systems and reaction centres synthesized in our laboratory are used to illustrate that structural and thermodynamic factors controlling energy and electron transfer in these constructs can be modified to optimize performance. Artificial reaction centres have been incorporated into liposomal membranes where they convert light energy to vectorial redox potential. This redox potential drives a Mitchellian, quinone-based, proton-transporting redox loop that generates a Deltamu H(+) of ca. 4.4 kcal mol(-1) comprising DeltapH ca. 2.1 and Deltapsi ca. 70 mV. In liposomes containing CF(0)F(1)-ATP synthase, this system drives ATP synthesis against an ATP chemical potential similar to that observed in natural systems.

Energy transfer reactions involving carotenoids: quenching of chlorophyll fluorescence

Carotenoids have a key role in photosynthesis in photosynthetic systems, transferring excitation energy to chlorophyll (Chl) during light harvesting. These pigments also protect the photosynthetic apparatus from photodamage by quenching the Chl triplet state and singlet oxygen. In addition, in higher plants and some algae, a number of xanthophylls also have the ability to deactivate excited Chl under conditions of excess excitation via the operation of the xanthophyll cycle (violaxanthin<-->antheraxanthin<-->zeaxanthin or diadinoxanthin<-->diatoxanthin). The formation of zexanthin (or diatoxanthin) can be clearly correlated with the non-photochemical quenching of Chl fluorescence, and is now recognized as a major photoprotective process in higher plants and a number of algal genera. The interconversion of these xanthophylls in response to a changing light environment alters the extent of their carbon-carbon double bond conjugation, which, in turn, affects the excited state energies and lifetimes of the carotenoids and may also alter their structure/conformation and hydrophobicity. The possible roles of these photophysical and physicochemical changes in the mechanism(s) of xanthophyll-mediated energy dissipation via quenching of Chl fluorescence are discussed.