Publications by authors named "Mariana P Serrano"

13 Publications

  • Page 1 of 1

Review of biosensing with whispering-gallery mode lasers.

Light Sci Appl 2021 Feb 26;10(1):42. Epub 2021 Feb 26.

Department of Physics and Astronomy, Living Systems Institute, University of Exeter, Exeter, EX4 4QD, UK.

Lasers are the pillars of modern optics and sensing. Microlasers based on whispering-gallery modes (WGMs) are miniature in size and have excellent lasing characteristics suitable for biosensing. WGM lasers have been used for label-free detection of single virus particles, detection of molecular electrostatic changes at biointerfaces, and barcode-type live-cell tagging and tracking. The most recent advances in biosensing with WGM microlasers are described in this review. We cover the basic concepts of WGM resonators, the integration of gain media into various active WGM sensors and devices, and the cutting-edge advances in photonic devices for micro- and nanoprobing of biological samples that can be integrated with WGM lasers.
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http://dx.doi.org/10.1038/s41377-021-00471-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7910454PMC
February 2021

Oxidation of tyrosine: Antioxidant mechanism of l-DOPA disclosed.

Free Radic Biol Med 2021 Mar 29;165:360-367. Epub 2021 Jan 29.

Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CCT La Plata-CONICET. Casilla de Correo 16, Sucursal 4, (1900) La Plata, Argentina. Electronic address:

Tyrosine is an amino acid related to crucial physiological events and its oxidation, that produce beneficial or detrimental effects on biological systems, has been extensively studied. Degradation of tyrosine often begins with the loss of an electron in an electron transfer reaction in the presence of a suitable electron acceptor. The reaction is facilitated by excited states of the acceptor in photosensitized processes. Several products of tyrosine oxidation have been described, the main ones being 3,4-dihydroxy-l-phenylalanine (commonly known as DOPA) and tyrosine dimers. Here, we report tyrosine recovery from tyrosyl radical, after one-electron oxidation, in the presence of DOPA. We propose that under high oxidative stress the oxidation of tyrosine may be controlled, in part, by one of its oxidation products. Also, we present strong evidence of antioxidant action of DOPA by preventing tyrosine dimerization, one of the most serious oxidative protein modifications, and the origin of structural modifications leading to the loss of protein functionality.
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http://dx.doi.org/10.1016/j.freeradbiomed.2021.01.037DOI Listing
March 2021

Fabrication and Characterization of Hollow Microcapsules from Polyelectrolytes Bearing Thymine Pendant Groups for Ultraviolet-B (UVB)-Induced Crosslinking.

Chempluschem 2019 05;84(5):504-511

Instituto de Bionanotecnología del NOA (INBIONATEC) CONICET, Universidad Nacional de Santiago del Estero (UNSE), RN9, Km 1125, G4206XCP, Santiago del Estero, Argentina.

DNA - bioinspired polyelectrolytes poly[vinylbenzylthymine (VBT)-4-vinylbenzyltriethylammonium chloride (VBA)] and poly[vinylbenzylthymine (VBT)-4-vinylphenylsufonate (VPS)] were used for the preparation of hollow microcapsules (HMC) using the layer-by-layer method and CaCO microspheres as removable molds. Stable aqueous suspensions of spherical-shaped HMCs with a shell composed of six layers of VBA-based polyelectrolytes were obtained, of approximately (7.0±1.5) μm diameter and a shell thickness of 1 μm. Ultraviolet-B irradiation of the HMC suspensions induces an efficient crosslinking between adjacent polyelectrolyte chains through the formation of thymine photodimers, such as the cyclobutane pyrimidine dimer (CPD) and the (6-4) pyrimidine-pyrimidone photoproduct (6-4PP). This process resulted in a reduction of the average interstitial mesh size of the HMC shells, modulating their permeability properties and increasing the mechanical stability of the HMC without a noticeable modification of size and shape. Thus, the DNA-bioinspired polyelectrolytes are promising materials for the preparation of UVB-responsive HMCs.
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http://dx.doi.org/10.1002/cplu.201900131DOI Listing
May 2019

Evidence of the effectiveness of Resveratrol in the prevention of guanine one-electron oxidation: possible benefits in cancer prevention.

Phys Chem Chem Phys 2019 Jul;21(29):16190-16197

Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata (UNLP), CCT La Plata-CONICET, Diagonal 113 y 64, (1900) La Plata, Argentina.

Over the past few years, the interest in Resveratrol (3,4',5,-trihydroxystilbene, RSV) has increased due to the evidence found of its antioxidant action that protects biomolecules and cells from oxidative damage. The interest has been further exacerbated by the natural presence of RSV in some fruits and derivatives, especially in red wine. In this paper we present evidence of RSV capacity in protecting a deoxynucleotide, an essential constituent of DNA, from one-electron oxidation. This article evaluates the mechanism responsible for the antioxidant action of RSV, after one-electron oxidation of 2'-deoxyguanosine 5'-monophosphate (dGMP), by kinetic analysis during steady-state irradiation and laser flash photolysis experiments. Results showed that RSV protects dGMP by recovering the nucleotide from its radical, which is formed after the reaction of dGMP with the triplet excited state of the photosensitizer. In the absence of RSV, dGMP is irremediably oxidized, and if the damage occurs in dGMP located in DNA molecules, the consequences can be as serious as mutations and subsequent carcinogenic lesions.
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http://dx.doi.org/10.1039/c9cp03027aDOI Listing
July 2019

Quenching of the Singlet and Triplet Excited States of Pterin by Amino Acids.

Photochem Photobiol 2019 01 5;95(1):220-226. Epub 2018 Dec 5.

Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CCT La Plata-CONICET, La Plata, Argentina.

Unconjugated oxidized pterins accumulate in the skin of patients suffering from vitiligo and, under UVA irradiation, photosensitize the oxidation of amino acids. In this work, we study the interaction of the singlet and triplet excited states of pterin (Ptr), the parent compound of oxidized pterins, with four oxidizable amino acids: tryptophan (Trp), tyrosine (Tyr), histidine (His) and methionine (Met). Steady-state and time-resolved fluorescence measurements and laser flash photolysis experiments were performed to investigate the quenching of the Ptr excited states by the amino acids in aqueous solution. The singlet excited states of Ptr are quenched by Met mainly via a dynamic process and by Trp via a combination of dynamic and static processes. His does not quench singlet excited states of Ptr, and quenching by Tyr could not be investigated due to the low solubility of this amino acid. The triplet excited states of Ptr are quenched by the four studied amino acids, and the corresponding bimolecular quenching rate constants are in the range of diffusion controlled limit. The assessment of the results in the context of the Ptr-photosensitization of amino acids suggests that triplet excited state of Ptr is the species that initiates the photochemical processes.
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http://dx.doi.org/10.1111/php.13046DOI Listing
January 2019

Photophysical and Photochemical Properties of 3-methylpterin as a New and More Stable Pterin-type Photosensitizer.

Photochem Photobiol 2018 09 20;94(5):881-889. Epub 2018 May 20.

Departamento de Química, Facultad de Ciencias Exactas, Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Universidad Nacional de La Plata (UNLP), La Plata, Argentina.

Pterin derivatives are heterocyclic compounds which are present in different biological systems. Neutral aqueous solutions of pterins present acid-base and keto-enol equilibria. These compounds, under UV-A radiation fluoresce, undergo photooxidation, generate reactive oxygen species and photoinduce the oxidation of biological substrates. As photosensitizers, they may act through different mechanisms, mainly through an electron transfer-initiated process (type-I mechanism), but they also produce singlet molecular oxygen ( O ) upon irradiation (type-II mechanism). In general, upon UV-A excitation two triplet states, corresponding to the lactim and lactam tautomers, are formed, but only the last one is the responsible for the photosensitized reactions of biomolecules. We present a study of the photochemical properties of 3-methylpterin (3-Mep) which, in contrast to most pterin derivatives, exists only in the lactam form. Also an improvement in the synthesis of 3-Mep is reported. The spectroscopic properties 3-Mep in aqueous solution were similar to those of the unsubstituted pterin derivative (Ptr) in its acid form, such as absorption, fluorescent and phosphorescent emission spectra. Experiments using 2'-deoxyguanosine 5'-monophosphate (dGMP) as oxidizable target demonstrated that methylation at C-3 position of the pterin moiety does not affect significantly the efficiency of photosensitization, but results in a more photostable sensitizer.
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http://dx.doi.org/10.1111/php.12931DOI Listing
September 2018

Thymidine radical formation via one-electron transfer oxidation photoinduced by pterin: Mechanism and products characterization.

Free Radic Biol Med 2016 07 3;96:418-31. Epub 2016 May 3.

Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata (UNLP), CCT La Plata-CONICET, Diagonal 113 y 64, 1900 La Plata, Argentina. Electronic address:

UV-A radiation (320-400nm), recognized as a class I carcinogen, induces damage to the DNA molecule and its components through different mechanisms. Pterin derivatives are involved in various biological functions, including enzymatic processes, and it has been demonstrated that oxidized pterins may act as photosensitizers. In particular, they accumulate in the skin of patients suffering from vitiligo, a chronic depigmentation disorder. We have investigated the ability of pterin (Ptr), the parent compound of oxidized pterins, to photosensitize the degradation of the pyrimidine nucleotide thymidine 5'-monophosphate (dTMP) in aqueous solutions under UV-A irradiation. Although thymine is less reactive than purine nucleobases, our results showed that Ptr is able to photoinduce the degradation of dTMP and that the process is initiated by an electron transfer from the nucleotide to the triplet excited state of Ptr. In the presence of molecular oxygen, the photochemical process leads to the oxidation of dTMP, whereas Ptr is not consumed. In the absence of oxygen, both compounds are consumed to yield a product in which the pterin moiety is covalently linked to the thymine. This compound retains some of the spectroscopic properties of Ptr, such as absorbance in the UV-A region and fluorescence properties.
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http://dx.doi.org/10.1016/j.freeradbiomed.2016.04.196DOI Listing
July 2016

Unraveling the Degradation Mechanism of Purine Nucleotides Photosensitized by Pterins: The Role of Charge-Transfer Steps.

Chemphyschem 2015 Jul 28;16(10):2244-52. Epub 2015 May 28.

Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata (UNLP), CCT La Plata-CONICET, Casilla de Correo 16, Sucursal 4, (1900) La Plata (Argentina).

Photosensitized reactions contribute to the development of skin cancer and are used in many applications. Photosensitizers can act through different mechanisms. It is currently accepted that if the photosensitizer generates singlet molecular oxygen ((1) O2 ) upon irradiation, the target molecule can undergo oxidation by this reactive oxygen species and the reaction needs dissolved O2 to proceed, therefore the reaction is classified as (1) O2 -mediated oxidation (type II mechanism). However, this assumption is not always correct, and as an example, a study on the degradation of 2'-deoxyguanosine 5'-monophosphate photosensitized by pterin is presented. A general mechanism is proposed to explain how the degradation of biological targets, such as nucleotides, photosensitized by pterins, naturally occurring (1) O2 photosensitizers, takes place through an electron-transfer-initiated process (type I mechanism), whereas the contribution of the (1) O2 -mediated oxidation is almost negligible.
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http://dx.doi.org/10.1002/cphc.201500219DOI Listing
July 2015

Type I photosensitization of 2'-deoxyadenosine 5'-monophosphate (5'-dAMP) by biopterin and its photoproduct formylpterin.

Photochem Photobiol 2013 Nov-Dec;89(6):1456-62. Epub 2013 Aug 3.

Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata (UNLP), CCT La Plata-CONICET, La Plata, Argentina.

Biopterin (Bip) and its photoproducts 6-formylpterin (Fop) and 6-carboxypterin (Cap) accumulate in the skin of patients suffering from vitiligo, a chronic depigmentation disorder where the protection against UV radiation fails because of the lack of melanin. These compounds absorb in the UV-A inducing a potential photosensitizing action that can cause damage to DNA and other biomolecules. In this work, we have investigated the capability of these pterin derivatives (Pt) to act as photosensitizers under UV-A irradiation for the degradation of 2'-deoxyadenosine 5'-monophosphate (5'-dAMP) in aqueous solutions, as model DNA target. Steady-state and time-resolved experiments were performed and the effect of pH was evaluated. The results showed that photosensitized degradation of 5'-dAMP was only observed under acidic conditions, and a mechanistic analysis revealed the participation of the triplet excited state of the pterin derivatives ((3)Pt*) by electron transfer yielding the corresponding pair of radical ions (Pt(•-) and 5'-dAMP(•+)), with successive photosensitizer recovery by electron transfer from Pt(•-) to O2. Finally, 5'-dAMP(•+) participates in subsequent reactions to yield degradation products.
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http://dx.doi.org/10.1111/php.12134DOI Listing
June 2015

Tryptophan oxidation photosensitized by pterin.

Free Radic Biol Med 2013 Oct 5;63:467-75. Epub 2013 Jun 5.

Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas, Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CCT La Plata-CONICET, Boulevard 113 y 64, 1900 La Plata, Argentina.

Pterins are normal components of cells and they have been previously identified as good photosensitizers under UV-A irradiation, inducing DNA damage and oxidation of nucleotides. In this work, we have investigated the ability of pterin (Ptr), the parent compound of oxidized pterins, to photosensitize the oxidation of another class of biomolecules, amino acids, using tryptophan (Trp) as a model compound. Irradiation of Ptr in the UV-A spectral range (350 nm) in aerated aqueous solutions containing Trp led to the consumption of the latter, whereas the Ptr concentration remained unchanged. Concomitantly, hydrogen peroxide (H₂O₂) was produced. Although Ptr is a singlet oxygen ((1)O₂) sensitizer, the degradation of Trp was inhibited in O₂-saturated solutions, indicating that a (1)O₂-mediated process (type II oxidation) was not an important pathway leading to Trp oxidation. By combining different analytical techniques, we could establish that a type I photooxidation was the prevailing mechanism, initiated by an electron transfer from the Trp molecule to the Ptr triplet excited state, yielding the corresponding radical ions (Trp(·+)/Trp(-H)· and Ptr(·-)). The Trp reaction products that could be identified by UPLC-mass spectrometry are in agreement with this conclusion.
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http://dx.doi.org/10.1016/j.freeradbiomed.2013.05.044DOI Listing
October 2013

Photosensitizing properties of biopterin and its photoproducts using 2'-deoxyguanosine 5'-monophosphate as an oxidizable target.

Phys Chem Chem Phys 2012 Sep 23;14(33):11657-65. Epub 2012 Jul 23.

Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata (UNLP), CCT La Plata-CONICET, La Plata, Argentina.

UV-A radiation (320-400 nm) induces damage to the DNA molecule and its components through photosensitized reactions. Biopterin (Bip) and its photoproducts 6-formylpterin (Fop) and 6-carboxypterin (Cap) accumulate in the skin of human beings suffering from vitiligo, a depigmentation disorder where the protection against UV radiation fails because of the lack of melanin. This study was aimed to evaluate the photosensitizing properties of oxidized pterins present in the skin and to elucidate the mechanisms involved in the photosensitized oxidation of purine nucleotides by pterins in vitro. For this purpose, steady-state and time-resolved experiments in acidic (pH 5.0-5.8) aqueous solution were performed using Bip, Fop and Cap as photosensitizers and the nucleotide 2'-deoxyguanosine 5'-monophosphate (dGMP) as an oxidizable target. The three pterin derivatives are able to photosensitize dGMP, being Fop the most efficient sensitizer. The reactions proceed through two competing pathways: (1) electron transfer from dGMP to triplet excited-state of pterins (type I mechanism) and (2) reaction of dGMP with (1)O(2) produced by pterins (type II mechanism). Kinetic analysis revealed that the electron transfer pathway is the main mechanism and the interaction of dGMP with the triplet excited-state of pterins and the formation of the corresponding dGMP radicals were demonstrated by laser flash photolysis experiments. The biological implications of the results obtained are also discussed.
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http://dx.doi.org/10.1039/c2cp41476gDOI Listing
September 2012

Emission properties of dihydropterins in aqueous solutions.

Phys Chem Chem Phys 2011 Apr 15;13(16):7419-25. Epub 2011 Mar 15.

INIFTA, Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CCT La Plata-CONICET., C.C. 16, Suc. 4, (1900) La Plata, Argentina.

Pterins belong to a class of heterocyclic compounds present in a wide range of living systems and accumulate in the skin of patients affected by vitiligo, a depigmentation disorder. The study of the emission of 7,8-dihydropterins is difficult because these compounds are more or less unstable in the presence of O(2) and their solutions are contaminated with oxidized pterins which have much higher fluorescence quantum yields (Φ(F)). In this work, the emission properties of six compounds of the dihydropterin family (6-formyl-7,8-dihydropterin (H(2)Fop), sepiapterin (Sep), 7,8-dihydrobiopterin (H(2)Bip), 7,8-dihydroneopterin (H(2)Nep), 6-hydroxymethyl-7,8-dihydropterin (H(2)Hmp), and 6-methyl-7,8-dihydropterin (H(2)Mep)) have been studied in aqueous solution. The fluorescence characteristics (spectra, Φ(F), lifetimes (τ(F))) of the neutral form of these compounds have been investigated using the single-photon-counting technique. Φ(F) and τ(F) values obtained lie in the ranges 3-9 × 10(-3) and 0.18-0.34 ns, respectively. The results are compared to those previously reported for oxidized pterins.
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http://dx.doi.org/10.1039/c0cp02912bDOI Listing
April 2011

Photodimerization of 7,8-dihydroneopterin in aqueous solution under UV-A irradiation.

Photochem Photobiol 2011 Jan-Feb;87(1):51-5. Epub 2010 Nov 12.

Departamento de Química, Facultad de Ciencias Exactas, Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Universidad Nacional de La Plata, CCT La Plata-CONICET, La Plata, Argentina.

7,8-Dihydroneopterin (H(2) Nep) is secreted during the oxidative burst of stimulated macrophages. The photochemistry of H(2) Nep was investigated in neutral aqueous solutions exposed to UV-A radiation (320-400nm) at room temperature. The kinetics were followed by UV/Vis spectrophotometry and HPLC, whereas the photoproducts were analyzed by electrospray ionization mass spectrometry. Excitation of H(2) Nep leads to the formation of isomeric dimers with molecular masses equal to exactly twice the molecular mass of the reactant. The corresponding quantum yield of H(2) Nep consumption (Φ(-R) =(3.8±0.5)×10(-2)) was independent of O(2) and reactant concentrations. Mechanistic implications are discussed.
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http://dx.doi.org/10.1111/j.1751-1097.2010.00833.xDOI Listing
April 2011