Publications by authors named "Juan Oyarzo"

8 Publications

  • Page 1 of 1

Tuning the Covering on Gold Surfaces by Grafting Amino-Aryl Films Functionalized with Fe(II) Phthalocyanine: Performance on the Electrocatalysis of Oxygen Reduction.

Molecules 2021 Mar 15;26(6). Epub 2021 Mar 15.

Universidad de Santiago de Chile (USACH), Faculty of Chemistry and Biology, Department of Chemistry of the Materials, Soft Matter Research and Technology Center, SMAT-C. Av. Libertador B. O'Higgins 3363, Box 40, Correo 33, Santiago 9170022, Chile.

Current selective modification methods, coupled with functionalization through organic or inorganic molecules, are crucial for designing and constructing custom-made molecular materials that act as electroactive interfaces. A versatile method for derivatizing surfaces is through an aryl diazonium salt reduction reaction (DSRR). A prominent feature of this strategy is that it can be carried out on various materials. Using the DSRR, we modified gold surface electrodes with 4-aminebenzene from 4-nitrobenzenediazonium tetrafluoroborate (NBTF), regulating the deposited mass of the aryl film to achieve covering control on the electrode surface. We got different degrees of covering: monolayer, intermediate, and multilayer. Afterwards, the ArNO end groups were electrochemically reduced to ArNH and functionalized with Fe(II)-Phthalocyanine to study the catalytic performance for the oxygen reduction reaction (ORR). The thickness of the electrode covering determines its response in front of ORR. Interestingly, the experimental results showed that an intermediate covering film presents a better electrocatalytic response for ORR, driving the reaction by a four-electron pathway.
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http://dx.doi.org/10.3390/molecules26061631DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7998582PMC
March 2021

Evaluation of trypanocidal properties of ferrocenyl and cyrhetrenyl N-acylhydrazones with pendant 5-nitrofuryl group.

J Inorg Biochem 2021 Jun 23;219:111428. Epub 2021 Mar 23.

Departament de Química Inorgànica i Orgànica, Secció de Química Inorgànica, Facultat de Química, Universitat de Barcelona, Martí i Franqués 1-11, E-08028 Barcelona, Spain. Electronic address:

Four N-acylhydrazones of general formulae [R-C(O)-NH-N=C(R)(5-nitrofuryl)] with (R = ferrocenyl or cyrhetrenyl and R = H or Me) are synthesized and characterized in solution and in the solid-state. Comparative studies of their stability in solution under different experimental conditions and their electrochemical properties are reported. NMR studies reveal that the four compounds are stable in DMSO‑d and complementary UV-Vis studies confirm that they also exhibit high stability in mixtures DMSO:HO at 37 °C. Electrochemical studies show that the half-wave potential of the nitro group of the N-acylhydrazones is smaller than that of the standard drug nifurtimox and the reduction process follows a self-protonation mechanism. In vitro studies on the antiparasitic activities of the four complexes and the nifurtimox against Trypanosoma cruzi and Trypanosoma brucei reveal that: i) the N-acylhydrazones have a potent inhibitory growth activity against both parasites [EC in the low micromolar (in T. cruzi) or even in the nanomolar (in T. brucei) range] and ii) cyrhetrenyl derivatives are more effective than their ferrocenyl analogs. Parallel studies on the L rat skeletal myoblast cell line have also been conducted, and the selectivity indexes determined. Three of the four N-acylhydrazones showed higher selectivity towards T. brucei than the standard drug nifurtimox. Additional studies suggest that the organometallic compounds are bioactivated by type I nitroreductase enzymes.
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http://dx.doi.org/10.1016/j.jinorgbio.2021.111428DOI Listing
June 2021

Novel multifunctional and multitarget homo- (Fe) and heterobimetallic [(Fe,M) with M = Re or Mn] sulfonyl hydrazones.

Dalton Trans 2020 Sep;49(35):12249-12265

Laboratorio de Química Inorgánica y Organometálica, Departamento de Química Analítica e Inorgánica, Facultad de Ciencias Químicas, Universidad de Concepción, Edmundo Larenas 129, Casilla 160-c, Concepción, Chile.

The synthesis and characterization of the novel ferrocenyl sulfonyl hydrazide [Fe(η5-C5H5){(η5-C5H4)-S(O)2-NH-NH2}] (2) is reported. Additional studies on its reactivity using acetone or the ferrocenyl-, cyrhetrenyl- or cymantrenyl-aldehydes have allowed us to isolate and characterize [Fe(η5-C5H5){(η5-C5H4)-S(O)2-NH-N[double bond, length as m-dash]CMe2}] (3), the bis(ferrocenyl) derivative [Fe(η5-C5H5){[(η5-C5H4)-S(O)2-NH-N[double bond, length as m-dash]CH-(η5-C5H4)]Fe(η5-C5H5)}] (4) and the heterodimetallic compounds [Fe(η5-C5H5){[(η5-C5H4)-S(O)2-NH-N[double bond, length as m-dash]CH-(η5-C5H4)]M(CO)3}] with M = Re (5a) or Mn (5b). The X-ray crystal structures of compounds 3, 5a and 5b are also reported. A comparative study of their electrochemical and spectroscopic properties is also described. Additional computational calculations based on the DFT methodology have allowed us to elucidate the effect produced by the replacement of the terminal -NH2 (in 2) by the -N[double bond, length as m-dash]CMe2 (in 3) and -N[double bond, length as m-dash]CHR (in 4, 5a and 5b) moieties on the electronic distribution and to explain the differences detected in their electrochemical properties and absorption spectra. In vitro cytotoxicity studies of compounds 2, 4, 5a and 5b on the HCT-116 (colon), MCF7 and MDA-MB231 (breast) cancer cell lines reveal that compound 2 has no significant activity (IC50 > 100 μM), while its derivatives 4, 5a and 5b proved to be active in the three cancer cell lines selected in this study. The growth inhibition potency of compounds 5a and 5b against the triple negative MDA-MB231 breast cancer cell line is similar (or slightly) greater than that of cisplatin. Moreover, compounds 2, 4, 5a and 5b are less toxic than cisplatin in the normal and non-tumoral BJ fibroblasts, and the heterodimetallic complexes 5a and 5b with selective index >2.1 show an outstanding selective toxicity towards the MDA-MB231 cancer cells.
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http://dx.doi.org/10.1039/d0dt01756fDOI Listing
September 2020

Challenges in the clinical implementation of a biopsychosocial model for assessment and management of orofacial pain.

J Oral Rehabil 2020 Jan 3;47(1):87-100. Epub 2019 Sep 3.

Department of Oral Diagnostic Sciences, School of Dental Medicine, University at Buffalo, Buffalo, NY, USA.

Distress, suffering and care-seeking behaviour are characteristics of pain-related disease and illness. Pain that transitions from an acute to a chronic phase carries with it the potential of further effects: these include a worsening of the disease or illness; high-impact chronic pain; and substantial personal, societal and economic burden. The biopsychosocial model directly addresses these multiple processes, yet clinical frameworks supporting this model are not universally implemented. This paper explores barriers to clinical implementation of a full biopsychosocial framework for temporomandibular disorders (TMD) and other oro-facial pain (OFP) conditions. In June 2016, INfORM invited OFP researchers to a workshop designed to optimise the DC/TMD Axis-II. Workshop groups identified five sources of implementation barriers: (1) cultures and societies, (2) levels-of-care settings, (3) health services, (4) cross-cultural validity of self-report instruments and (5) provider and patient health literacy. Three core problems emerged: (A) mental health aspects are seldom fully considered, thus impairing the recognition of illness, (B) training in use of validated multi-axial assessment protocols is under-rated and insufficiently used, and (C) clinical assessment often fails to recognise that sensory and emotional dimensions are fundamental aspects of pain. To improve patient care, these barriers and problems require action. Most importantly, TMD/OFP educators and researchers need to coordinate globally and (i) be educated in the biopsychosocial model, (ii) implement evidence-based biopsychosocial guidelines for assessment and management of OFP conditions at their institutions, (iii) incorporate this model in undergraduate and postgraduate dental curricula and (iv) be responsive to stakeholders, including regulatory authorities and practitioners.
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http://dx.doi.org/10.1111/joor.12871DOI Listing
January 2020

Impact of the Regularization Parameter in the Mean Free Path Reconstruction Method: Nanoscale Heat Transport and Beyond.

Nanomaterials (Basel) 2019 Mar 11;9(3). Epub 2019 Mar 11.

Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and The Barcelona Institute of Science and Technology (BIST), Campus UAB, 08193 Bellaterra, Barcelona, Spain.

The understanding of the mean free path (MFP) distribution of the energy carriers in materials (e.g., electrons, phonons, magnons, etc.) provides a key physical insight into their transport properties. In this context, MFP spectroscopy has become an important tool to describe the contribution of carriers with different MFP to the total transport phenomenon. In this work, we revise the MFP reconstruction technique and present a study on the impact of the regularization parameter on the MFP distribution of the energy carriers. By using the L-curve criterion, we calculate the optimal mathematical value of the regularization parameter. The effect of the change from the optimal value in the MFP distribution is analyzed in three case studies of heat transport by phonons. These results demonstrate that the choice of the regularization parameter has a large impact on the physical information obtained from the reconstructed accumulation function, and thus cannot be chosen arbitrarily. The approach can be applied to various transport phenomena at the nanoscale involving carriers of different physical nature and behavior.
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http://dx.doi.org/10.3390/nano9030414DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6473983PMC
March 2019

A novel type of organometallic 2-R-2,4-dihydro-1H-3,1-benzoxazine with R = [M(η-CH)(CO)] (M = Re or Mn) units. Experimental and computational studies of the effect of substituent R on ring-chain tautomerism.

Dalton Trans 2019 Jan;48(3):1023-1039

Instituto de Química, Pontificia Universidad Católica de Valparaíso, Casilla 4059, Valparaíso, Chile.

The syntheses, characterization, X-ray crystal structures, electrochemical properties and anticancer and antichagasic activities of the first examples of 2-substituted 2,4-dihydro-1H-3,1-benzoxazines with half-sandwich organometallic arrays, [M(η5-C5H4)(CO)3] (M = Re or Mn), at position-2 are described. Experimental and computational studies based on DFT calculations on the open forms [Schiff bases of general formulae R-CH[double bond, length as m-dash]N-C6H4-2-CH2OH] (5), with R = ferrocenyl (a), phenyl (b), cyrhetrenyl (c) or cymantrenyl (d), and their tautomeric forms (2-substituted 2,4-dihydro-1H-3,1 benzoxazines) have allowed us to establish the influence of substituents a-d and solvents on: (a) the extent of tautomeric equilibria (5a-5d) ↔ (6a-6d) and (b) their electrochemical properties and the electronic distribution on the open and closed forms. Despite the formal similarity between 6c and 6d, their anticancer and antiparasitic activities are markedly different. Compound 6d is inactive in the HCT116, MDA-MB231 and MCF7 cancer cell lines, but 6c shows moderate activity in the latter cell line, while the Mn(i) complex (6d) is a more potent anti-Trypanosoma cruzi agent than its Re(i) analogue (6c).
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http://dx.doi.org/10.1039/c8dt03265cDOI Listing
January 2019

Isomeric and hybrid ferrocenyl/cyrhetrenyl aldimines: a new family of multifunctional compounds.

Dalton Trans 2018 Jan;47(5):1635-1649

Instituto de Química, Pontificia Universidad Católica de Valparaíso, Casilla 4059, Valparaíso, Chile.

The synthesis and characterization of two novel and isomeric hybrid ferrocenyl/cyrhetrenyl aldimines [(η-CH)Fe{(η-CH)-CH[double bond, length as m-dash]N-(η-CH)}Re(CO)] (1) and [(η-CH)Fe{(η-CH)-N[double bond, length as m-dash]CH-(η-CH)}Re(CO)] (2) are reported. Their X-ray crystal structures reveal that both adopt the E form. However, molecules of 1 and 2 differ in the relative arrangement of the "Fe(η-CH)" and "Re(CO)" units (anti in 1 and syn in 2). This affects the type of intermolecular interactions, the assembly of the molecules and therefore their crystal architecture. Comparative studies of their electrochemical, spectroscopic and photo-physical properties have allowed us to clarify the effect produced by the location of the organometallic arrays (ferrocenyl or cyrhetrenyl) on electronic delocalization, the proclivity of the metals to undergo oxidation and their emissive properties. Theoretical studies based on Density Functional Theory (DFT) calculations on the two compounds have also been carried out in order to rationalize the experimental results and to assign the bands detected in their electronic spectra. The cytotoxic activities of compounds 1 and 2 against human adenocarcinoma cell lines [breast (MCF7 and MDA-MB-231) and colon (HCT-116)] reveal that imine 2 has a greater inhibitory growth effect than 1 and it is ca. 1.8 times more potent than cisplatin in the triple negative MDA-MB 231 and in the cisplatin resistant HCT-116 cell lines. A comparative study of their effect on the normal and non-tumour human skin fibroblast BJ cell lines is also reported.
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http://dx.doi.org/10.1039/c7dt04142jDOI Listing
January 2018

Caries-free subjects have high levels of urease and arginine deiminase activity.

J Appl Oral Sci 2014 Jun;22(3):235-40

Institute for Research in Dental Sciences, Faculty of Dentistry, University of Chile, Santiago, Chile.

Objectives: This study investigated the relationship between urease and arginine deiminase system (ADS) activities and dental caries through a cross-sectional study.

Material And Methods: Urease and ADS activities were measured in saliva and plaque samples from 10 caries-free subjects and 13 caries-active. Urease activity was obtained from the ammonia produced by incubation of plaque and saliva samples in urea. ADS activity was obtained from the ammonia generated by the arginine-HCl and Tris-maleate buffer. Specific activity was defined as micromoles of ammonia per minute per milligram of protein. Shapiro-Wilk statistical test was used to analyze the distribution of the data, and Mann-Whitney test was used to determine the significance of the data.

Results: The specific urease activity in saliva and plaque was significantly higher in individuals with low DMFT scores. ADS activity in saliva (6.050 vs 1.350, p=0.0154) and plaque (8.830 vs 1.210, p=0.025) was also higher in individuals with low DMFT scores.

Conclusions: Caries-free subjects had a higher ammonia generation activity by urease and arginine deiminase system for both saliva and plaque samples than low caries-active subjects. High levels of alkali production in oral environment were related to caries-free subjects.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4072275PMC
http://dx.doi.org/10.1590/1678-775720130591DOI Listing
June 2014