ARTICLE | doi:10.20944/preprints201810.0406.v1
Online: 18 October 2018 (07:54:20 CEST)
Platinum(II) complexes have been found to be effective against cancer cells. Cisplatin curbs cell replication by interacting with the deoxyribonucleic acid (DNA), eventually leading to cell death and reducing cell proliferation. In order to investigate the ability of platinum complexes to affect cancer cells, two examples from the class of polyflurophenylorganoamidoplatinum(II) complexes were synthesised and tested on isolated DNA. The two compounds trans-[N,N’-bis(1,2,3,5,6-pentafluorophenyl)ethane-1,2-diaminato(1-)](2,3,4,5,6-pentafluorobenzoato)(pyridine)platinum(II) (PFB), and trans-[N,N’-bis(1,2,3,5,6-pentafluorophenyl)ethane-1,2-diaminato(1-)](2,4,6-trimethylbenzoato)(pyridine)platinum(II) (TMB) were compared with cisplatin through their reaction with DNA. Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) spectroscopy was applied to analyse the interaction of the Pt(II) complexes with DNA in the hydrated, dehydrated and rehydrated state. These were compared with control DNA in acetone/water (PFB, TMB) and isotonic saline (cisplatin) under the same conditions. Principle Component Analysis (PCA) was applied to compare the ATR-FTIR spectra of the untreated control DNA with spectra of PFB and TMB treated DNA samples. Disruptions in the conformation of DNA treated with the Pt(II) complexes upon rehydration were mainly observed by monitoring the position of the IR-band around 1711 cm-1 assigned to the DNA base-stacking vibration. Furthermore, other intensity changes in the phosphodiester bands of DNA at ~1234 cm-1 and 1225 cm-1 and shifts in the dianionic phosphodiester vibration at 966 cm-1 were observed. The isolated double stranded DNA (dsDNA) or single stranded DNA (ssDNA) showed different structural changes when incubated with the studied compounds. PCA confirmed PFB had the most dramatic effect by denaturing both dsDNA and ssDNA. Both compounds, along with cisplatin, induced changes in DNA bands at 1711, 1088, 1051 and 966 cm-1 indicative of DNA conformation changes. The ability to monitor conformational change with infrared spectroscopy paves the way for a sensor to screen for new anticancer therapeutic agents.
ARTICLE | doi:10.20944/preprints201812.0216.v2
Online: 22 January 2019 (17:54:09 CET)
Potato is a starchy, tuberous crop from the perennial Solanum tuberosum having high nutritional values. This paper is the first analytical approach to quantify Pt and Rh in vegetal food. In this study a total of 38 different potatoes samples produced in Europe and one in Australia were investigated. Determinations of Pt and Rh in potatoes samples were carried out by Differential Pulse Voltammetry (DPV/a) for platinum and by Adsorptive Stripping Voltammetry (AdSV) for Rh using standard addition procedure. Because no certified reference potatoes containing platinum and rhodium are available, we used addition standard method. The quantification limits for Pt and Rh are 0.007 and 0.0008 μg Kg−1 respectively. Considering all the potatoes samples, concentrations of Pt and Rh vary in the ranges from 0.007 to 109 μg Kg−1 (sample n° 6 potatoes grown in Sicily) and from 0.0008 to 0.030 μg Kg−1 (sample n°23 of potatoes grown in Emilia Romagna) respectively. For both metals, in many cases the concentrations fall near the quantification limit. In all the samples, platinum is always more abundant than rhodium and their ratio meanly is 14500, which is much greater than that of the earth's crust (about 100).
ARTICLE | doi:10.20944/preprints201810.0454.v1
Online: 19 October 2018 (14:15:28 CEST)
Trans platinum complexes have been the landmark in unconventional drugs prompting the development of innovative structures that might exhibit chemical and biological profiles different to cisplatin. Iodido complexes made a new turning point in the platinum drug design field since their cytotoxicity was reevaluated and reported. In this new study, we have synthesized and evaluated diodido complexes bearing aliphatic amines and pyridines in trans configuration. X-ray diffraction support the structural characterization. Their cytotoxicity has been evaluated in tumor cell lines such as SAOS-2, A375, T-47D and HCT116. Moreover, we report their solution behavior and reactivity with biological models. UVA irradiation induces an increase in their reactivity towards model nucleobase 5´-GMP in early stages, and promotes the release of the pyridine ligand (spectator ligand) at longer reaction times. Density Functional calculations have been performed and the results are compared with our previous studies with other iodido derivatives.
ARTICLE | doi:10.20944/preprints202105.0391.v1
Subject: Medicine & Pharmacology, Allergology Keywords: ovarian cancer; platinum resistance; prognostic factors
Online: 17 May 2021 (14:36:50 CEST)
Ovarian cancer (OC) represents the most common and lethal gynecologic malignancy, due to its increased incidence and mortality rate. It is usually diagnosed in advanced stages and, even though surgery and platinum-based treatment are initially efficient, recurrences emerge in over 70% of cases. Although there are multiple options of chemotherapy drugs from which to choose, little is known regarding the best strategy for prolonged survival. Thus, the aim of this study was to assess the effect that most frequently used chemotherapeutic regimens have upon time-to-treatment-failure (TTF) from the first line and beyond, considering clinical and biological factors which influence the treatment outcome of platinum-resistant recurrent OC. We retrospectively analyzed data from 78 patients diagnosed with platinum-resistant OC, who underwent chemotherapy-based treatment with or without anti-angiogenic therapy at OncoHelp Oncology Center, Romania (January 2016 - February 2021). Our study identified positive predictive factors for TTF related to anthropometry (age over 60 for patients treated with topotecan with or without bevacizumab), renal function (creatinine levels between 0.65 and 1 mg/dl for patients treated with regimens containing bevacizumab and pegylated liposomal doxorubicin) and treatment choice (bevacizumab in combination with pegylated liposomal doxorubicin or topotecan used from the first line and beyond).
ARTICLE | doi:10.20944/preprints201810.0485.v1
Subject: Materials Science, Surfaces, Coatings & Films Keywords: bandgap; doping; palladium; platinum; stoichiometric NiO
Online: 22 October 2018 (10:02:55 CEST)
This paper presents computational study of non-stoichiometric nickel oxide in a 32-cell NiO system to model and validate localized heating effects due to nanosecond laser irradiation. Variation in Bandgap of NiO is studied as a function of varying concentrations of native defects ranging from 0 to 25%. It is observed that there is a slight increase in the bandgap from 3.8 eV for stiochiometric NiO to 3.86 eV for Ni-rich NiO and to 3.95 eV for O-rich NiO. It is hence deduced that the experimental laser irradiation leads to simultaneous reduction of Ni2+ ions and oxidation of NiO as the number of laser pulses increase. As well, a detailed study on the effects of doping nickel family elements, i.e. palladium (Pd) and platinum (Pt) in stoichiometric NiO is presented. A bandgap decrease from 3.8 eV for pure NiO to 2.5 eV for Pd-doping and 2 eV for Pt-doping for varying doping concentrations ranging from 0–25% Pd, Pt respectively is observed.
ARTICLE | doi:10.20944/preprints202011.0628.v1
Subject: Chemistry, Analytical Chemistry Keywords: Heavy Metal; Chronoamperometric; Platinum Electrode; Rotating Disk
Online: 25 November 2020 (10:03:38 CET)
Pollution by heavy metals is one of the most severe environmental issues that threaten global sustainability. This review presents a recent advance in electrochemical sensors for heavy metal detection Rotating Disk Platinum Electrode are discussed. This study on the production of a modern natural water electrochemical antimony (II) and cupper (II) test include the use of platinum electrode. Antimony and cupper were pre-concentrated on the modified electrode surface and adsorbed to the surface, oxidizing at E = 540 mV and E = 85 mV, respectively. After 20 min of accumulation, time the best-defined anodic peak was obtained of surface. The precision was tested by carrying out chronoamperometric measurements at a concentration of Sb+2 and Cu+2 8.5x10-8 M and 9.5x10-7 M, respectively.
ARTICLE | doi:10.20944/preprints202005.0072.v1
Online: 5 May 2020 (11:01:06 CEST)
This study on the production of a modern natural water electrochemical antimony (II) test include the use of platinum platinum electrode electrodes. Antimony (II) was pre-concentrated on the modified electrode surface and adsorbed to the surface, oxidizing at E = -680 mV. Compared to the platinum electrode, the platinum nanoelectrode exhibited superior performance and, unexpectedly, received a higher electrochemical response. After 25 min of accumulation, time the best-defined anodic peak was obtained with 0.2 mol L-1 KNO3 pH 5.0. Using these parameters, the L-1 Sb 2 + calibration plot was linear over range 1 = 10−8 to 5x10−6 mol. The precision was tested by carrying out eight replicate measurements at a concentration of 2.5x10−5 mol. L-1; the variance coefficient was 2.9%. The method was applied to analyte determination in water samples from the river. Other metal ion attack on Sb's (II) voltammetric response has been studied. In the SEM image, the nanoparticle electrode was clearly observed and characterized by X-ray diffraction and cyclic voltammetry
ARTICLE | doi:10.20944/preprints201905.0045.v2
Subject: Engineering, Energy & Fuel Technology Keywords: fuel cell; carbon nanotube; catalyst; platinum-ruthenium
Online: 29 December 2019 (07:06:08 CET)
Due to low working temperature, high energy density and low pollution, proton exchange fuel cells have been investigated under different operating conditions in different applications. Using platinum catalysts in methanol fuel cells leads to increasing the cost of this kind of fuel cell which is considered as a barrier to the commercialism of this technology. For this reason, a lot of efforts have been made to reduce the loading of the catalyst required on different supports. In this study, carbon black (CB) and carbon nanotubes (CNT) have been used as catalyst supports of the fuel cell as well as using the double-metal combination of platinum-ruthenium (PtRu) as anode electrode catalyst and platinum (Pt) as cathode electrode catalyst. The performance of these two types of electro-catalyst in the oxidation reaction of methanol has been compared based on electrochemical tests. Results showed that the carbon nanotubes increase the performance of the micro-fuel cell by 37% at maximum power density, compared to the carbon black. Based on thee-electrode tests of chronoamperometry and voltammetry, it was found that the oxidation onset potential of methanol for CNT has been around 20% less than CB, leading to the kinetic improvement of the oxidation reaction. The current density of methanol oxidation reaction increased up to 62% in CNT sample compared to CB supported one, therefore the active electrochemical surface area of the catalyst has been increased up to 90% by using CNT compared to CB which shows the significant rise of the electrocatalytic activity in CNT supported catalyst. Moreover, the resistance of the CNT supported sample to poisonous intermediate species has been found 3% more than CB supported one. According to the chronoamperometry test results, it was concluded that the performance and sustainability of the CNT electro-catalyst show remarkable improvement compared to CB electro-catalyst in the long term.
ARTICLE | doi:10.20944/preprints201810.0157.v1
Subject: Chemistry, Other Keywords: Antitumoral activity; platinum; N-heterocyclic carbene; polyethyleneimine.
Online: 8 October 2018 (16:05:07 CEST)
The high interest in N-heterocyclic platinum carbene complexes in cancer research stems from their high cytotoxicity to human cancer cells, their stability, as well as their ease of functionalization. However, the development of these new molecules as anticancer agents still faces multiple challenges, in particular solubility in aqueous media. Here, we synthesized platinum-NHC bioconjugates that combine water-solubility and cytotoxicity by using polyethyleneimine as polymer carrier. We showed that the activity of these conjugates is modulated by the size of the polymer and the overall density of metal ions onto polymer chains. They displayed an effective activity after only 45 minutes of exposure in vitro correlated with a quick uptake by the cells as shown by the use of various fluorescent-tagged derivatives.
ARTICLE | doi:10.20944/preprints202007.0561.v1
Subject: Chemistry, Electrochemistry Keywords: perfluorooctanoic acid; emerging contaminant; defluorination; platinum; electro-oxidation
Online: 23 July 2020 (12:36:19 CEST)
Perfluorooctanoic acid (PFOA), C7F15COOH, has been widely employed over the past fifty years, causing an environmental problem due to its dispersion and low biodegradability. Furthermore, the high stability of this molecule, conferred by the high strength of the C-F bond makes it very difficult to remove. In this work, electrochemical techniques are applied for PFOA degradation in view to study the influence of the cathode on defluorination. For this purpose, boron doped diamond (BDD), Pt, Zr and stainless steel have been tested as cathodes working with BDD anode at low electrolyte concentration (3.5 mM) to degrade PFOA at 100 mg/L. Among these cathodic materials, Pt improves the defluorination reaction. The electro-degradation of a PFOA molecule starts by a direct exchange of one electron at the anode and then follows a complex mechanism involving reaction with hydroxyl radicals and adsorbed hydrogen on the cathode. It is assumed that Pt acts as an electrocatalyst, enhancing PFOA defluorination by the reduction reaction of perfluorinated carbonyl intermediates on the cathode. The defluorinated intermediates are then more easily oxidized by HO• radicals. Hence, high mineralization (xTOC: 76.1%) and defluorination degrees (xF-: 58.6%) were reached with Pt working at current density j = 7.9 mA/cm2. This BDD-Pt system reaches a higher efficiency in terms of defluorination for a given electrical charge than previous works reported in literature. Influence of the electrolyte composition and initial pH are also explored.
ARTICLE | doi:10.20944/preprints202005.0069.v1
Subject: Chemistry, Analytical Chemistry Keywords: Platinum Electrode; Nanoparticle; Heavy metal; Square Wave Voltammetry
Online: 5 May 2020 (10:45:05 CEST)
The copper deposition on the platinum and palladium nanoelectrode has been studied using cyclic voltammetry. The use of nanoelectrode platinum and palladium are defined in the study of heavy metals. The noble nanoelectrode of metal has a typical silicone processing structure. In comparison to the nanoelectrodes, the geometry of the electrode series is complex and balanced. Nanoelectrodes of platinum are found effective in detecting heavy metal. There was regular analysis of the use of the sensors. The identification constraints down to the ng /L level was accomplished by refined electrode geometry and the stripping procedures. The process was used for the study of water sample determination. Another heavy metal ion attack voltammetric reaction was studied. The SEM picture clearly observed and characterized the nanoparticle electrode by X-ray diffraction and cyclic voltammetry.
ARTICLE | doi:10.20944/preprints202004.0260.v1
Subject: Engineering, Biomedical & Chemical Engineering Keywords: Ear-EEG; laser structuring; porous platinum; Berger effect
Online: 16 April 2020 (07:39:35 CEST)
The interest in dry EEG electrodes has increased in recent years and especially as everyday suitability earplugs for measuring drowsiness or focus of auditory attention. However, the challenge is still the need for a good electrode material, which is reliable and can be easily processed for highly personalized applications. Laser processing as used here is a fast and very precise method to produce personalized electrode configurations that meet the high requirements of in-ear EEG electrodes, for example. The arrangement of the electrodes on the very flexible and compressible mats allows an exact alignment of the electrodes to the ear mold and contributes to a high wearing comfort, as no edges or metal protrusions are present. For better transmission properties, an adapted coating process for surface enlargement of platinum electrodes is used, which allows easy control of the thickness and growth form of the porous layer. The porous platinum-copper alloy is chemically very stable, shows no exposed copper residues and enlarges the effective surface area by 40. In a proof-of-principle experiment, these porous platinum electrodes could be used to measure the Berger effect in a dry state using just one ear of a test person. Their signal-to-noise ration and frequency transfer function is comparable to gel-based silver/silver chloride electrodes.
ARTICLE | doi:10.20944/preprints201807.0392.v1
Subject: Chemistry, Electrochemistry Keywords: electrodeposition; platinum; highly oriented pyrolytic graphite; 2D growth
Online: 20 July 2018 (16:08:11 CEST)
We discuss the electrodeposition of two-dimensional (2D) Pt-nanostructures on HOPG achieved under constant applied potential versus a Pt counter electrode (Eappl = ca. - 2.2 V vs RHE). The deposition conditions are discussed in terms of the electrochemical behavior of the electrodeposition precursor (H2PtCl6). We performed cyclic voltammetry (CV) of the electrochemical Pt deposit on HOPG and on Pt substrates to study the relevant phenomena that affect the morphology of Pt deposition. Under conditions where the Pt deposition occurs and H2 evolution is occurring at the diffusion-limited rate (- 0.3 V vs RHE), Pt forms larger structures on the surface of HOPG, and the electrodeposition of Pt is not limited by diffusion. This indicates the need for large overpotentials to direct the 2D growth of Pt. Investigation of the possible effect of Cl- showed that Cl- deposits on the surface of Pt at low overpotentials, but strips from the surface at potentials more positive than the electrodeposition potential. The CV of Pt on HOPG is a strong function of the nature of the surface. We propose that during immersion of HOPG in the electrodeposition solution (3 mM H2PtCl6, 0.5 M NaCl, pH 2.3) Pt islands are formed spontaneously, and these islands drive the growth of the 2D nanostructures.
ARTICLE | doi:10.20944/preprints202210.0183.v1
Subject: Materials Science, Nanotechnology Keywords: platinum; high-index facets; carbon support; glucose oxidation; electrocatalysts
Online: 13 October 2022 (02:23:07 CEST)
Catalyst with high catalytic activity and good stability are desirable in the electrocatalytic oxidation of glucose. Herein, Pt concave nanocubes with high-index facets (HIFs) supported by carbon black (Pt CNC/CB) are prepared through a hydrothermal method. The experimental results demonstrate that the peak current densities in different potential regions on the Pt CNC/CB anode are 0.22, 0.20, and 0.60 mA cm−2, respectively. The glucose oxidation reaction shows superior performances in basic and neutral conditions than in acid conditions. Better stability is achieved by Pt CNC/CB than Pt concave nanocubes (Pt CNCs). Abundant surface defects with low-coordinated atom numbers, such as the steps, kinks, and edges, are served as active sites in the electrocatalytic oxidation of glucose. With the addition of carbon black, the catalytic activity can be improved by facilitating the full exposure of the active surface defects on the HIFs of Pt CNCs. Moreover, to address the aggregation of Pt CNCs, caused by the high surface energy of HIFs, the introduction of carbon material is an effective way to preserve the HIFs, and thus enhance the stability of the catalyst. Hence, the prepared Pt CNC/CB electrocatalyst has great potential to be applied in the electrooxidation of glucose.
ARTICLE | doi:10.20944/preprints202103.0123.v1
Subject: Materials Science, Biomaterials Keywords: fly ash waste; platinum nanoparticles; industrial dyes; adsorption; photodegradation
Online: 3 March 2021 (10:03:12 CET)
New materials are obtained by transforming fly ash wastes into a valuable composite, with tandem adsorption and photodegradation properties. Mild hydrothermal synthesis, from titanium dioxide, Platinum nanoparticles and zeolite materials obtained from a waste, fly ash, as support, was involved in the composite preparation. The Platinum nanoparticles extended the photocatalytic activity of the composite in Visible range (Eg = 2.1 eV). The efficiency of tandem adsorption and photocatalytic activity of the new composite were evaluated to 80.70% for Bemacid Blau and 93.89% for Bemacid Rot, after 360 min, the irradiation time, with H2O2 addition.
ARTICLE | doi:10.20944/preprints201906.0011.v1
Subject: Earth Sciences, Other Keywords: Platinum; Light Rare Earths Elements; Sedimentary ore deposit: SEDEX
Online: 3 June 2019 (09:12:09 CEST)
This paper describe the influence of the Rift Molango during the mineralization of elements of the platinum group and some light rare earths elements in a sedimentary exhalative ore deposit.
ARTICLE | doi:10.20944/preprints202005.0402.v2
Subject: Chemistry, Analytical Chemistry Keywords: electrical conductivity; volcanic tuff; cyclic voltammetry; conductivity nanoparticle; platinum electrode
Online: 18 February 2021 (10:00:10 CET)
This paper has experimentally measured volcanic tufa electrical conductance. The calculations are carried out in accordance with the potential of cyclic voltammetry in a constant state. The cyclic voltammograms nanoelectrode platinum prepared electrochemically were examined in the range -0.2 to 1.2 V vs. AgCl [Cl-]:1.0 M in the presence and absence of volcanic tuff in the aqueous solution of 1.0 M HCl. The cyclic voltammetry studies show that the Nano platinum film suffers degradation when the potential exceeds +0.85 V, and below this potential, it is quite stable. The redox reaction of the electrode is reversible. The nanoparticle platinum synthesized at low temperature and high acid concentration exhibits higher electronic conductivities. It has been observed that, relative to area under the peak aggregate tests, the use of volcanic concrete was showing a large increase in electrical conductivity. It was shown that with cyclic voltammetry, three well-defined anode peak could be achieved at a power of 0.0, 0.4 and 0.6 V versus Ag/AgCl.
ARTICLE | doi:10.20944/preprints201803.0020.v1
Subject: Earth Sciences, Geology Keywords: rare earths; platinum; SEDEX ore body; rift mega structure; transgression
Online: 2 March 2018 (08:58:08 CET)
This work shows the preliminary description of the origin of a sedimentary - exhalative outcrop of Jurassic Lower Pliensbachian. The location of this deposit was achieved by applying an examination based in the identification of sedimentary transgressions of heterochronies ages and the identification of a Rift – type mega –structure. According with the methodology, it was carried out a study of the discordant relationships between two types of sediments: continental and marine. According the characterization, it was noted the existence of light rare earths, in values that show positive anomalies in comparison with the distribution of elements in upper continental crust according to the Clarke , reflecting so a felsic affinity of the mineral deposit. Also, positive anomalies of platinum and Pd, were determined with marginal contents of Au and Ag; and finally the base metals Zn, Pb and Cu were detected in low contents, which could be due to the presence of altered shale. According to the sedimentary lithology found, which was of siliciclastic type; to the exhalative roots observed during the fieldwork; the presence of quartz minerals such as biotite and muscovite; the presence of minerals of hydrothermal remobilization like chalcopyrite with some base metals, altered shale, as well as sulfur deficiency; this mineral reservoir could be defined as a SEDEX – type.
ARTICLE | doi:10.20944/preprints202207.0310.v1
Subject: Physical Sciences, Condensed Matter Physics Keywords: ab-initio; DFT calculations; 2D materials; MoS2; optical properties; platinum; FPMD
Online: 21 July 2022 (03:24:52 CEST)
Using first-principles molecular dynamics (FPMD), we performed numerical simulations at 300 K to explore the interaction of a 2D MoS2 surface and a platinum atom, calculating the optical properties of the resulting material. The pristine MoS2 is a semiconductor with a gap of around 1.8 eV. The Pt atom is chemisorbed by the surface with an adsorption energy of −1.718 eV. With the adsorption of the Pt atom, the material remains a semiconductor, and its energy band gap reduces to 1.04 eV. But changes in the material's energy band structure imply substantial changes in its optical properties. The energy band structure of the 2D MoS2 with a sulfur vacancy VS shows that the material becomes a conductor, and there are significant changes in its optical properties. We also found that the Pt atom chemisorbs in a sulfur vacancy of the material, with an adsorption energy of −4.1164 eV. After the adsorption of Pt atoms in the sulfur vacancy, the material becomes a semiconductor with a band gap of 1.06 eV, and the changes in the optical absorption and reflectivity are significant.
ARTICLE | doi:10.20944/preprints201801.0256.v1
Subject: Earth Sciences, Geochemistry & Petrology Keywords: n-alkanes, platinum, catalyst, soil, humic acid, Freetown Intrusion, Sierra Leone
Online: 26 January 2018 (16:11:36 CET)
Soil above a platinum-group element (PGE)-bearing horizon within the Freetown Layered Intrusion, Sierra Leone contains anomalous concentrations of n-alkanes (CnH2n+2) in the range C14 to C22 not readily attributable to an algal or lacustrine origin. Longer chain n-alkanes (C23 to C31) in the soil were derived from the breakdown of leaf litter beneath the closed canopy humid tropical forest. Spontaneous breakdown of the longer chain n-alkanes to form C14-22 n-alkanes without biogenic or abiogenic catalysts is unlikely as the n-alkanes are stable. In the Freetown soil, the catalytic properties of the PGE (Pt in particular) may lower the temperature at which oxidation of the longer chain n-alkanes can occur. Reaction between these n-alkanes and Pt species such as Pt2+(H2O)2(OH)2 and Pt4+(H2O)2(OH)4 can bend and twist the alkanes, and significantly lower the Heat of Formation. Acknowledging the possibility of microbial catalysis and the difficulty of identifying a direct organic geochemical source of the lighter n-alkanes, this paper explores the theoretical potential for abiogenic Pt species catalysis as a mechanism of breakdown of the longer n-alkanes to form C14-22 alkanes. This novel mechanism could substantiate the presence of the PGE in solution predicted by soil geochemistry and illustrate processes involving the PGE. Graphical Abstract
ARTICLE | doi:10.20944/preprints201612.0065.v1
Subject: Chemistry, Organic Chemistry Keywords: monodisperse silica nanospheres; supported platinum(IV) complex; peptide; intramolecular disulfide; reusability
Online: 12 December 2016 (17:54:08 CET)
Some peptide-based drugs including oxytocin, vasopressin, ziconotide, pramlintide, nesiritide, and octreotide, contain one intramolecular disulfide bonds. A novel and reusable monodispersed silica nanosphere-supported Pt(IV) complex (SiO2@TPEA@Pt(IV)) was synthesized via a four-step procedure and used for formation of intramolecular disulfide bonds in peptides. TEM and chemical mapping results for the Pt(II) intermediates and for SiO2@TPEA@Pt(IV) show that the silica nanospheres possess a monodisperse spherical structure and contain uniformly distributed Si, O, C, N, Cl, and Pt. The valence state of Pt on the silica nanospheres was characterized by XPS. The Pt(IV) loaded on SiO2@TPEA@Pt(IV) was 0.15 mmol/g, as determined by UV-vis spectrometry. Formation of intramolecular disulfides in six dithiol-containing peptides of variable lengths by use of SiO2@TPEA@Pt(IV) was investigated and the relative oxidation yields were determined by HPLC. In addition, peptide 1 (Ac-CPFC-NH2) was utilized to study the reusability of SiO2@TPEA@Pt(IV). No significant decrease in the relative oxidation yield was observed after ten reaction cycles. Moreover, the structure of SiO2@TPEA@Pt(IV) after being used ten cycles was determined to be similar to its initial one, demonstrating the cycling stability of the complex.
REVIEW | doi:10.20944/preprints202108.0037.v1
Subject: Medicine & Pharmacology, Oncology & Oncogenics Keywords: ovarian cancer; checkpoint inhibitors; ICIs; immunotherapy; PARP; avelumab; pembrolizumab; nivolumab; bevacizumab; platinum
Online: 2 August 2021 (13:01:35 CEST)
Background: Ovarian cancer (OC) represents the eighth most common cancer and the fifth leading cause of cancer-related deaths among the female population. In the advanced setting, chemotherapy represents the first-choice treatment, despite a high recurrence rate. In the last ten years, immunotherapy based on immune checkpoint inhibitors (ICIs) has profoundly modified the therapeutic scenario of many solid tumors. We sought to summarize the main findings regarding the clinical use of ICIs in the OC. Methods: We searched the PubMed, Embase, and Cochrane Databases, and conference abstracts from international congresses (such as ASCO, ESMO, SGO) for clinical trials, focusing on ICIs both as monotherapy and as combinations in the advanced OC. Results: 20 studies were selected, of which 16 were phase I or II and 4 phase III trials. ICIs targeting PD1 (nivolumab, pembrolizumab), PD-L1 (avelumab, atezolizumab, durvalumab), and CTLA4 (ipilimumab, tremelimumab) were employed. No significant survival improvement was achieved; conversely, early terminations due to futility or toxicity were recorded. Combinations with chemotherapy, anti-VEGF, and, overall, PARP-inhibitors seem feasible and enhance the response rate and survival, notwithstanding a worse safety profile. Conclusions: The identification of biomarkers with a predictive role for ICIs’ efficacy is mandatory. Moreover, genomic and immune profiling of the OC might lead to an improved treatments selection and design of tailored trials.
ARTICLE | doi:10.20944/preprints202006.0342.v1
Subject: Chemistry, Analytical Chemistry Keywords: Heavy metal; Platinum electrode; Ion beam sputtering deposition; Nanoparticle; IBSD; Ion detection
Online: 28 June 2020 (19:31:19 CEST)
An electrochemical sensing platinum nanoparticle in the tantalum electrode is provided by means of an Ion Beam Sputtering Deposition (IBSD). The electrode was made with a Pt solution, sputtered simultaneously with hydrochloric acid corrosion on tantalum substrate. In the study of heavy metal ions, for example, the platinum nanoparticle electrodes as prepared were used Square wavelength voltammetry (OSWV) Hg2+, Cu2+ and Ag2+. The porous electrodes were observed in a broader range by the Pt nanostructure electrode for heavy metal ions. Furthermore, the susceptibility to detection has been shown to be saturated as the thickness of the layer electrode exceeded 50 nm. For Hg2+ 0,003-1 M, for Cu2+ 0,005-3 M and for Ag2+ the linear detection scale is 0,009-4 M. There has also been good reusability and repeatability. In addition, a scan electron microscope (SEM) used to study platinum electrode forming process and nanostructure. This electrode will have interesting applications in sensing systems.
ARTICLE | doi:10.20944/preprints202006.0179.v1
Subject: Chemistry, Analytical Chemistry Keywords: Heavy metal; Platinum electrode; Ion beam sputtering deposition; Nanoparticle; IBSD; Ion detection
Online: 14 June 2020 (14:46:10 CEST)
Today, contamination from heavy metals in the atmosphere is a global concern. Efficient detection techniques are therefore necessary if heavy metal exposure levels in different media are to be determined. The voltammetry method for in situ detection of heavy metal ions is a very sensitive electrochemical method. This thesis explores emerging developments in electrode alteration, materials production and experimental optimization. An electrochemical sensing platinum nanoparticle in the tantalum electrode is provided by means of an Ion Beam Sputtering Deposition (IBSD). The electrode was made with a Pt solution, sputtered simultaneously with hydrochloric acid corrosion on tantalum substrate. In the study of heavy metal ions, for example, the platinum nanoparticle electrodes as prepared were used Square wavelength voltammetry (OSWV) Hg2+, Cu2+ and Ag2+. The porous electrodes were observed in a broader range by the Pt nanostructure electrode for heavy metal ions. Furthermore, the susceptibility to detection has been shown to be saturated as the thickness of the layer electrode exceeded 50 nm. For Hg2+ 0,003-1 M, for Cu2+ 0,005-3 M and for Ag2+ the linear detection scale is 0,009-4 M. There has also been good reusability and repeatability. In addition, a scan electron microscope (SEM) used to study platinum electrode forming process and nanostructure. This electrode will have interesting applications in sensing systems.
ARTICLE | doi:10.20944/preprints202008.0667.v1
Subject: Chemistry, Medicinal Chemistry Keywords: Ovarian cancer; drug resistance; apoptosis; proteomics; combination; cytotoxicity; artemisinin; oleanolic acid; platinum drugs; cisplatin
Online: 30 August 2020 (12:06:32 CEST)
Background: In the present study, cisplatin, artemisinin and oleanolic acid were evaluated alone and in combination, on human ovarian A2780, A2780ZD0473R and A2780cisR cancer cell lines with aim of overcoming cisplatin resistance and side effects. Methods: Cytotoxicity was assessed by MTT reduction assay. CI values were used as a measure of combined drug effect. MALDI TOF/TOF MS/MS and 2-DE gel electrophoresis were used to identify protein biomarkers in ovarian cancer and to evaluate combination effects. Results: Synergism from combinations was dependent on concentration and sequence of administration. Generally, bolus was most synergistic. 49 proteins differently expressed by 2 ≥ fold were: CYPA, EIF5A1, Op18, p18, LDHB, P4HB, HSP7C, GRP94, ERp57, mortalin, IMMT, CLIC1, NM23, PSA3,1433Z, and HSP90B were down-regulated, whereas hnRNPA1, hnRNPA2/B1, EF2, GOT1, EF1A1, VIME, BIP, ATP5H, APG2, VINC, KPYM, RAN, PSA7, TPI, PGK1, ACTG and VDAC1 were up-regulated, while TCPA, TCPH, TCPB, PRDX6, EF1G, ATPA, ENOA, PRDX1, MCM7, GBLP, PSAT, Hop, EFTU, PGAM1, SERA and CAH2 were not-expressed in A2780cisR cells. The proteins were found to play critical roles in cell cycle regulation, metabolism and biosynthetic processes and drug resistance and detoxification. Conclusion: Results indicate that appropriately sequenced combinations of cisplatin with ART and OA may provide a means to reduce side effects and circumvent platinum resistance.
ARTICLE | doi:10.20944/preprints202102.0068.v1
Subject: Medicine & Pharmacology, Allergology Keywords: cost-effectiveness; pembrolizumab; etoposide-platinum; extensive-stage small-cell lung cancer; small cell lung cancer.
Online: 1 February 2021 (18:10:59 CET)
Background: The phase III KEYNOTE-604 study confirmed the benefit of pembrolizumab combined with chemotherapy in the first-line treatment of extensive-stage small-cell lung cancer(ES-SCLC). Intergrated the clinical benefits of pembrolizumab and its high cost into account, this study aim to assess the cost-effectiveness of adding pembrolizumab to standard first-line etoposide-platinum (EP) for patients with ES-SCLC from the the US payer perspective. Methods: A Markov model was developed to compared the costs and quality-adjusted life-years (QALYs) of pembrolizumab plus EP and placebo plus EP over a 10-year time horizon. Clinical efficacy, treatment utilization and safety data were pooled from the KEYNOTE-604 trial. Utilities were obtained from published resources. Costs were mainly collected from Medicare in 2020. Sensitivity analyses were performed to examined the robustness of our model. Results: Adding pembrolizumab to standard first-line EP, resulted in better effectiveness than the use of EP alone for ES-SCLC by 0.22 QALYs. Pembrolizumab plus EP was dominated economically by placebo plus EP, leading to an incremental cost-effectiveness ratio(ICER) of $334,373/ QALY. Deterministic sensitivity analyses indicated that the uncertainty in model parameters exerts no substantial effect on our results. Probability sensitivity analysis indicated that probabilities for pembrolizumab plus EP being cost-effective within a wide rang of willingness to pay were modest. Conclusion: From the US payer perspective, the first-line treatment for ES-SCLC with pembrolizumab plus EP was not cost-effective compare with placebo plus EP. Although pembrolizumab combination chemotherapy was beneficial to the survival of ES-SCLC, price reduction may be the necessary measure to improve its cost-effectiveness.
ARTICLE | doi:10.20944/preprints201811.0492.v1
Subject: Chemistry, Electrochemistry Keywords: single atom catalysis; carbon-supported catalysts; platinum-group metals; aberration-corrected scanning transmission electron microscopy
Online: 20 November 2018 (09:19:06 CET)
Nanoparticles of platinum-group metals (PGM) on carbon supports are widely used as catalysts for a number of chemical and electrochemical conversions on laboratory and industrial scale. The newly emerging field of single atom catalysis focuses on the ultimate level of metal dispersion, i.e. atomically dispersed metal species anchored on the substrate surface. However, the presence of single atoms in traditional nanoparticle-based catalysts remains largely overlooked. In this work we use aberration-corrected scanning transmission electron microscope to investigate four commercially available nanoparticle-based PGM/C catalysts (PGM = Ru, Rh, Pd, Pt). We show that in addition to nanoparticles, single atoms are also present on the surface of carbon substrates. These observations raise questions about the role that single atoms play in conventional nanoparticle PGM/C catalysts. We critically discuss the observations with regard to the quickly developing field of single atom catalysis.
TECHNICAL NOTE | doi:10.20944/preprints201810.0322.v1
Subject: Earth Sciences, Geology Keywords: platinum-group elements, silver, gold, Pd-tellurides, porphyry Cu-Mo, Rio Blanco –Los Bronces, Chile.
Online: 15 October 2018 (14:48:55 CEST)
Porphyry copper-molybdenum deposits (PCDs) are the world’s most important source of copper, molybdenum and rhenium. Previous studies have reported that some PCDs can have sub-economic to economic grades of critical metals, i.e., those elements that are both essential for modern societies and subject to the risk of supply restriction (e.g., platinum group elements (PGE), rare earth elements (REE), In, Co, Te, Ge, Ga, among others). Even though some studies have reported measured concentrations of Pd and Pt in PCDs, their occurrence and mineralogical form remain poorly constrained. Furthermore, these reconnaissance studies have focused predominantly on porphyry Cu-Au deposits, but very limited information is available for porphyry Cu-Mo systems. In this contribution, we report the occurrence of critical metal (Pd, Pt, Au, Ag, and Te) inclusions in copper sulfides from the world’s largest PCD, the supergiant Río Blanco-Los Bronces deposit in central Chile. Field emission scanning electron microscope (FESEM) observations of chalcopyrite and bornite from the potassic alteration zone reveal the presence of micro- to nano-sized particles (<1-10 μm) of noble metals, most notably Pd, Au, and Ag. The high-resolution data show that these inclusions are mostly tellurides, such as merenskyite [PdTe2], Pd-rich hessite [Ag2Te], sylvanite [(Ag, Au)Te2] and petzite [Ag3AuTe2]. The data point to Pd (and probably Pt) partitioning in copper sulfides during the high-temperature potassic alteration stage, opening new avenues of research aimed at investigating not only the mobility of PGE during mineralization and partitioning into sulfides, but also at evaluating the potential of porphyry Cu-Mo deposits as a source for noble metals.
ARTICLE | doi:10.20944/preprints201907.0215.v1
Subject: Chemistry, Medicinal Chemistry Keywords: Platinum, N-heterocyclic carbene ligand, anticancer activity, DNA interaction, optical tweezers technique, liquid phase AFM microscop
Online: 18 July 2019 (10:17:27 CEST)
A platinum (II) complex stabilized by a pyridine and a N-heterocyclic carbene ligand featuring an anthracenyl moiety was prepared. The compound was fully characterized and its molecular structure was determined by single-crystal X-ray diffraction. The compound demonstrated high in vitro antiproliferative activities against cancer cell lines with IC50 ranging from 10 to 80 nM. The presence of the anthracenyl moiety on the NHC Pt complex was used as a luminescent tag to probe the metal interaction with the nucleobases of the DNA through a pyridine-nucleobase ligand exchange. Such interaction of the platinum complex with DNA was corroborated by optical tweezers techniques and liquid phase AFM microscopy. The results revealed a two-state interaction between the platinum complex and the DNA strands. This two-state behaviour was quantified from the different experiments due to contour length variations. At 24h incubation, the stretching curves revealed multiple structural breakages, and AFM imaging revealed a highly compact and dense structure of platinum complexes bridging the DNA strands.
ARTICLE | doi:10.20944/preprints202002.0345.v1
Subject: Chemistry, Electrochemistry Keywords: platinum electrocatalys; PtCu/C; oxygen electroreduction; methanol electrooxidation; catalyst activity; durability; fuel cell life tests; de-alloyed catalysts; PEM FC
Online: 24 February 2020 (03:56:11 CET)
Behavior of supported alloyed and de-alloyed platinum-copper catalysts, which contained 14% - 27% wt. of Pt, was studied in the reactions of methanol electrooxidation (MOR) and oxygen electroreduction (ORR) in 0.1 M HClO4 solutions. Alloyed PtCux/C catalysts were prepared by a multistage sequential deposition of copper and platinum onto a Vulcan XC72 dispersed carbon support. De-alloyed PtCux-y/C catalysts were prepared by PtCux/C materials pretreatment in acid solutions. The effects of the catalysts initial composition and the acid treatment condition on their composition, structure, and catalytic activity in MOR and ORR were studied. Functional characteristics of platinum-copper catalysts were compared with those of commercial Pt/C catalysts when tested, both in an electrochemical cell and in H2/Air membrane-electrode assembly (MEA). It was shown that the acid pretreatment of platinum-copper catalysts practically does not have negative effect on their catalytic activity, but it reduces the amount of copper passing into the solution during the subsequent electrochemical study. The activity of platinum-copper catalysts in the MOR and the current-voltage characteristics of the H2/Air PEMFC MEAs measured in the process of their life tests were much higher than those of the Pt/C catalysts.
REVIEW | doi:10.20944/preprints201611.0120.v1
Subject: Medicine & Pharmacology, Oncology & Oncogenics Keywords: pNENs; 2010 WHO classification; Ki-67 index; mitotic count; pNEC; tumor differentiation; whole-exome sequence data; everolimus; sunitinib; platinum regimen
Online: 24 November 2016 (10:59:33 CET)
Pancreatic neuroendocrine neoplasms (pNENs) are rare tumors accounting for only 1-2% of all pancreatic tumors. pNENs are pathologically heterogeneous and are categorized into three groups (neuroendocrine tumor: NET G1, NET G2 and neuroendocrine carcinoma: NEC) on the basis of Ki-67 proliferation index and mitotic count according to the 2010 WHO classification of gastroenteropancreatic NENs. NEC in this classification includes both histologically well-differentiated and poorly differentiated subtypes, and modification of the WHO 2010 classification is under discussion based on genetic and clinical data. Genomic analysis has revealed NETs G1/G2 have genetic alterations in chromatin remodeling genes such as MEN1, DAXX and ATRX, whereas NECs have an inactivation of TP53 and RB1, and these data suggest that different treatment approaches would be required for NET G1/G2 and NEC. While there are promising molecular targeted drugs, such as everolimus or sunitinib, for advanced NET G1/G2, treatment stratification based on appropriate predictive and prognostic biomarkers is becoming an important issue. The clinical outcome of NEC is still dismal, and a more detailed understanding of the genetic backround together with preclinical studies to develop new agents, including those already under investigation for SCLC, will be needed to improve the prognosis.