Blocked diisocyanates as reactive coupling agents: Application to pine fiber-polypropylene composites

In this paper, composites from polypropylene and Kraft pulp (from Pinus radiata) were prepared. Phenyl isocyanate, unblocked and phenol blocked derivatives of 4,4`-methylenebis (phenyl isocyanate) (MDI) were used as coupling agents and the mechanical properties of the obtained composites analyzed. The results showed that the addition of such compatibilizers readily improved the tensile and flexural strengths of the composites. However, no significant variation in the mechanical properties was observed for composite formulations comprising different isocyanate compounds. Accordingly, the chemical structure of isocyanate derivatives did not affect extensively the mechanical properties of MDI-coupled pine fiber reinforced composites. These results were similar to those obtained in previous studies regarding the efficiency of organosilane coupling agents. In comparison to monoreactive isocyanates, the addition of MIDI increased considerably the mechanical properties of pine fiber-polypropylene composites. The mechanical anchoring of polymeric PP chains onto the irregular reinforcement surface supported this result. Non-isothermal DSC analysis showed a slowing effect of MDI on the crystallization kinetics of the coupled composites. This may have been the result of diminished polymer chain mobility in the matrix due to mechanical anchoring onto the fiber surface. Considering these results, the occurrence of strong bonds between the composite components was stated, rather than the unique existence of Van der Waals interactions among the non-polar structures. (c) 2008 Elsevier Ltd. All rights reserved.

Bonding of Composite Resin to Alumina and Zirconia Ceramics with Special Emphasis on Surface Conditioning and Use of Coupling Agents

Dental oxide ceramics have been inspired by their biocompability and mechanical properties which have made durable all-ceramic structures possible. Clinical longevity of the prosthetic structures is dependent on effective bonding with luting cements. As the initial shear bond strength values can be comparable with several materials and procedures, long-term durability is affected by ageing. Aims of the current study were: to measure the shear bond strength of resin composite-to-ceramics and to evaluate the longevity of the bond; to analyze factors affecting the bond, with special emphasis on: the form of silicatization of the ceramic surface; form of silanization; type of resin primer and the effect of the type of the resin composite luting cement; the effect of ageing in water was studied regarding its effect to the endurance of the bond. Ceramic substrates were alumina and yttrium stabilized zirconia. Ceramic conditioning methods included tribochemical silicatization and use of two silane couplings agents. A commercial silane primer was used as a control silane. Various combinations of conditioning methods, primers and resin cements were tested. Bond strengths were measured by shear bond strength method. The longevity of the bond was generally studied by thermocycling the materials in water. Additionally, in one of the studies thermal cycling was compared with long-term water storaging. Results were analysed statistically with ANOVA and Weibull analysis. Tribochemical treatment utilizing air pressure of 150 kPa resulted shear bond strengths of 11.2 MPa to 18.4 MPa and air pressure of 450 kPa 18.2 MPa to 30.5 MPa, respectively. Thermocycling of 8000 cycles or four years water storaging both decreased shear bond strength values to a range of 3.8 MPa to 7.2 MPa whereas initial situation varied from 16.8. Mpa to 23.0 MPa. The silane used in studies had no statistical significance. The use of primers without 10-MDP resulted spontaneous debonding during thermocycling or shear bond strengths below 5 MPa. As conclusion, the results showed superior long-term bonding with primers containing 10-MDP. Silicatization with silanizing showed improved initial shear bond strength values which considerably decreased with ageing in water. Thermal cycling and water storing for up to four years played the major role in reduction of bond strength, which could be due to thermal fatigue of the bonding interface and hydrolytic degradation of the silane coupled interface.

Sugarcane bagasse cellulose/HDPE composites obtained by extrusion

Natural fibers used in this study were both pre-treated and modified residues from sugarcane bagasse. Polymer of high density polyethylene (HDPE) was employed as matrix in to composites, which were prodUced by mixing high density polyethylene with cellulose (10%) and Cell/ZrO(2)center dot nH(2)O (10%), using an extruder and hydraulic press. Tensile tests showed that the Cell/ZrO(2)center dot nH(2)O (10%)/HDPE composites present better tensile strength than cellulose (10%)/HDPE composites. Cellulose agglomerations were responsible for poor adhesion between fiber and matrix in cellulose (10%)/HDPE composites. HDPF/natural fibers composites showed also lower tensile strength in comparison to the polymer. The increase in Young`s modulus is associated to fibers reinforcement. SEM analysis showed that the cellulose fibers insertion in the matrix Caused all increase of defects, which were reduced When modified cellulose fibers were Used. (C) 2008 Elsevier Ltd. All rights reserved.

Cellulose modified fibres in cement based composites

The objective of the present work is to evaluate the effect of surface modification of cellulose pulp fibres on the mechanical and microstructure of fibre-cement composites. Surface modification of the cellulose pulps was performed with Methacryloxypropyltri-methoxysilane (MPTS) and Aminopropyltri-ethoxysilane (APTS) in an attempt to improve their durability into fibre-cement composites. The surface modification showed significant influence on the microstructure of the composites on the fibre-matrix interface and in the mineralization of the fibre lumen as seen by scanning electron microscopy (SEM) with back-scattered electron (BSE) detector. Accelerated ageing cycles decreased modulus of rupture (MOR) and toughness (TE) of the composites. Composites reinforced with MPTS-modified fibres presented fibres free from cement hydration products, while APTS-modified fibres presented accelerated mineralization. Higher mineralization of the fibres led to higher embrittlement of the composite after accelerated ageing cycles. These observations are therefore very useful for understanding the mechanisms of degradation of fibre-cement composites. (C) 2009 Elsevier Ltd. All rights reserved.

Mean intrinsic tensile properties of stone groundwood fibers from softwood

Stone groundwood (SGW) is a fibrous matter commonly prepared in a high yield process, and mainly used for papermaking applications. In this work, the use of SGW fibers is explored as reinforcing element of polypropylene (PP) composites. Due to its chemical and superficial features, the use of coupling agents is needed for a good adhesion and stress transfer across the fiber-matrix interface. The intrinsic strength of the reinforcement is a key parameter to predict the mechanical properties of the composite and to perform an interface analysis. The main objective of the present work was the determination of the intrinsic tensile strength of stone groundwood fibers. Coupled and non-coupled PP composites from stone groundwood fibers were prepared. The influence of the surface morphology and the quality at interface on the final properties of the composite was analyzed and compared to that of fiberglass PP composites. The intrinsic tensile properties of stone groundwood fibers, as well as the fiber orientation factor and the interfacial shear strength of the current composites were determined

Kytkentäaineet puumuovikomposiiteissa

Puumuovikomposiittien valmistuksessa yhdistetään kaksi toisistaan eroavaa materiaalia jolloin saadaan aikaan materiaalien ominaisuuksien ainutlaatuinen yhdistelmä. Polymeerimateriaaleina käytetään pääasiassa erilaisia kestomuoveja. Kuitumateriaaleina voidaan käyttää puujauhetta, sahanpurua, paperin- ja kartongin valmistuksessa käytettävää sellua, nanoselluloosaa tai muita puukuitumateriaaleja. Polaarisen puukuidun ja polaarittoman muovimateriaalin välinen materiaalien rajapinnan adheesio on yleensä riittämätöntä, mikä vaikuttaa lopputuotteen ominaisuuksien heikkenemiseen. Kyseinen ongelma on pyritty ratkaisemaan käyttämällä erilaisia kytkentäaineita. Tässä työssä keskitytään käsittelemään erilaisia puumuovikomposiittien kytkentäaineita, niiden toimintaa sekä vaikutuksia lopputuotteeseen. Lisäksi työssä esitellään myös puumuovikomposiittien valmistusmateriaaleja ja valmistusprosesseja.

Amphiphile Verbindungen der 14. Gruppe - Synthese, Eigenschaften und Anwendungen von Organosilanolen

Im Rahmen dieser Dissertation wurde an der Darstellung stabiler, amphiphiler Silantriole gearbeitet. Es ist gelungen eine kontinuierliche Reihe sukzessive um CH2-Einheiten verlängerter Silantriole des Typs H3C(CH2)nC(CH3)2Si(OH)3 (n = 1-5) durch eine vierstufige Synthesesequenz ausgehend von n-Alkylbromiden herzustellen und zum Teil röntgenographisch zu untersuchen. Ihre oberflächenaktiven Eigenschaften in wässrigen Lösungen konnten erstmals mittels Oberflächenspannungsmessungen belegt werden. Durch gezielte Kondensationsreaktionen mit Trifluoressigsäure wurden ausgehend von den oben beschriebenen Silantriolen selektiv die entsprechenden Disiloxan-Tetrole erhalten und ebenfalls zum Teil durch Röntgenstrukturanalysen charakterisiert. Als weitere Kondensationsprodukte der Silantriole konnten die ersten Octasilsesquioxane mit tertiären Kohlenstoff-Substituenten durch Umsetzungen mit n-Bu4NF selektiv und in hohen Ausbeuten erhalten und ebenfalls röntgenographisch identifiziert werden. Es wurde an der Darstellung Aryl-substituierter Silantriole RSi(OH)3 (R = Mesityl-, Xylyl- und Tetramethyl-phenyl-) gearbeitet. Diese zeichnen sich jedoch durch ihre hohe Instabilität in Lösung und im Festkörper aus und konnten zum Teil nur zusammen mit ihren primären Kondensationsprodukten erhalten werden. Darüber hinaus wurden stabile Silandiole des Typs R(t-Bu)Si(OH)2 (R = n-Butyl und n-Pentyl) sowie das (o-CF3C6H4)2Si(OH)2 in hohen Ausbeuten und selektiv synthetisiert. Die Festkörpereigenschaften des (o-CF3C6H4)2Si(OH)2 sowie seiner Vorstufe (o-CF3C6H4)2SiCl2 konnten durch Kristallstrukturanalysen genauer untersucht werden. In der Arbeit wurden die ersten Anwendungen von Silanolen als Silan-Kupplungsreagenzien bei der Oberflächenmodifizierung von Glas beschrieben. Im Gegensatz zu gängigen säureassistierten Beschichtungen zeichnen sich diese Silanol-Beschichtungen durch eine deutlich höhere Hydrophobizität aus. Dies konnte durch Kontaktwinkel- und Zeta-Potential-Messungen bestätigt werden. Durch Röntgenreflektivitäts- und Sarfus-Messungen ist die Ausbildung von Monolagen im Falle von t-BuSi(OH)3-beschichteten Oberflächen plausibel. Die Oberflächenmorphologie der Silantriol-Beschichtungen wurde mittels AFM-Messungen untersucht. Die Si(OH)3-Funktion konnte in der vorliegenden Arbeit als ein neues Pharmakophor etabliert werden. Die Silantriole CySi(OH)3, TerSi(OH)3 und CH3CH2C(CH3)2Si(OH)3 (Cy = Cyclohexyl, Ter = Terphenyl) sind in der Lage das Enzym Acetylcholinesterase reversibel zu hemmen. Dabei zeigt das CySi(OH)3 mit 45 % relativ zur Kontrolle die höchste Inhibition.

Modificació de fibres de jute per l'elaboració de plàstics reforçats reciclables

El treball que s'ha dut a terme es centra en la recerca d'agents modificants per a fibres cel·lulòsiques capaços de reduir la polaritat de les funcions alcohol de la seva estructura per formació de funcions ester. Les fibres de jute se sotmeten a reacció en un sistema tancat provist d'atmòsfera de nitrogen a fi d'evitar reaccions laterals que no són del nostre interés.L'obtenció dels resultats perseguits està lligat a les condicions experimentals aplicades durant les reaccions. La influència de les diferents variables escollides facilitarà en major o menor grau la reacció entre les molècules d'agent d'acoblament i cel·lulosa vinculades. Una gran part de l'atenció es centrarà en l'estudi de l'etapa de modificació, sobretot en l'efectivitat dels reactius addicionats per la reacció amb els grups hidroxil. Un cop comparats els experiments realitzats tant amb clorur d'oleïl com amb anhídrid metacrílic, es conclou que la majoria de condicions provades permeten assolir valors de modificació prou significatius. L'excepció ve donada quan la temperatura utilitzada és de 20ºC, llavors les mateixes condicions que a una temperatura de 60ºC condueixen cap a resultats poc satisfactoris. La reactivitat per part dels dos agents d'acoblament utilitzats no ha estat la mateixa. Els resultats per condicions experimentals del mateix tipus han conduït cap a valors força diferents. Pel que fa a la determinació dels paràmetres òptims es conclou que les variables amb les que el grau de modificació millora considerablement són: una temperatura de 60ºC, 10% de catalitzador respecte la quantitat de clorur d'oleïl o anhídrid addicionada, relació OH reactiu estequiomètrica 1:1 i 40mL de solvent. Un cop modificada la fibra, se sotmet a reacció amb el monòmer estirè. Es comprova que el grau de polimerització segueix el valor de modificació prèviament obtingut, a menor quantitat de funcions alcohol lliures major interacció amb el monòmer estirè. Les propietats inicials de la fibra no es corresponen amb les obtingudes després del tractament, l'increment de la resistència a l'atac de microorganismes i a l'absorció d'humitat s'explica per una reducció de la presència de funcions alcohol polars i per la capa d'estirè polimeritzat per unió amb els dobles enllaços introduïts amb els agents d'acoblament. Pel que fa referència a les dues tècniques de caracterització més utilitzades, l'anàlisis elemental permet quantificar d'una manera precisa la reacció de la fibra amb els agents d'acoblament i la posterior reacció de la fibra modificada amb el monòmer estirè. La caracterització per espectroscopia d'infraroig permet comprovar qualitativament la reactivitat del clorur d'oleïl i qualitativament-quantitativament la de l'anhídrid metacrílic amb les funcions alcohol de la cel·lulosa present en les fibres de jute. Els pics més característics apareguts seran utilitzats per avaluar la reactivitat de la funció carbonílica del reactiu modificant amb l'estructura cel·lulòsica i del doble enllaç de la cel·lulosa modificada amb la matriu polimèrica.

Surface esterification of cellulose fibres: Processing and characterisation of low-density polyethylene/cellulose fibres composites

Low-density polyethylene was filled with cellulose fibres from sugar cane bagasse obtained from organosolv/supercritical carbon dioxide pulping process. The fibres were also used after chemical modification with octadecanoyl and dodecanoyl chloride acids. The morphology, thermal properties, mechanical properties in both the linear and nonlinear range, and the water absorption behaviour of ensuing composites were tested. The evidence of occurrence of the chemical modification was checked by X-ray photoelectron spectrometry. The degree of polymerisation of the fibres and their intrinsic properties (zero tensile strength) were determined. It clearly appeared that the surface chemical modification of cellulose fibres resulted in improved interfacial adhesion with the matrix and higher dispersion level. However, composites did not show improved mechanical performances when compared to unmodified fibres. This surprising result was ascribed to the strong lowering of the degree of polymerisation of cellulose fibres (as confirmed by the drastic decrease of their zero tensile strength) after chemical treatment despite the mild conditions used. (c) 2007 Elsevier Ltd. All rights reserved.

Effect of silica coating combined to a MDP-based primer on the resin bond to Y-TZP ceramic

The aim of this study was to evaluate the influence of silica coating and 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-based primer applications upon the bonding durability of a MDP-based resin cement to a yttrium stabilized tetragonal zirconia (Y-TZP) ceramic. Ninety-six Y-TZP tabs were embedded in an acrylic resin (free surface for adhesion: 5 x 5 mm(2)), ground finished and randomly divided into four groups (N = 24) according to the ceramic surface conditioning: (1) cleaning with isopropanol (ALC); (2) ALC + phosphoric acid etching + MDP-based primer application (MDP-primer); (3) silica coating + 3-methacryloyloxypropyl trimethoxysilane (MPS)-based coupling agent application (SiO(2) + MPS-Sil); and (4) SiO(2) + MDP-primer. The MDP-based resin cement was applied on the treated surface using a cylindrical mold (diameter=3 mm). Half of the specimens from each surface conditioning were stored in distilled water (37 C, 24 h) before testing. Another half of the specimens were stored (90 days) and thermo-cycled (12,000x) during this period (90d/TC) before testing. A shear bond strength (SBS) test was performed at a crosshead speed of 0.5 mm/min. Two factors composed the experimental design: ceramic conditioning strategy (in four levels) and storage condition (in two levels), totaling eight groups. After 90d/TC (Tukey; p < 0.05), SiO(2) + MDP-primer (24.40 MPa) promoted the highest SBS. The ALC and MDP-primer groups debonded spontaneously during 90d/TC. Bonding values were higher and more stable in the SiO2 groups. The use of MDP-primer after silica coating increased the bond strength. (C) 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part 8: Appl Biomater 95B: 69-74, 2010.

Materiais híbridos argila-poli(metil metacrilato) obtidos através do método grafting

Pós-graduação em Química - IQ

The mechanochemical modification of polyolefins using reactive modifier systems

The principal objective of this work was to improve the mechanical properties of glass fibre reinforced polypropylene (PP) composites by the mechanochemical modification of the PP. The modification of the PP was carried out by reactive processing of the PP with a modifier in a Buss Ko-Kneader. Two main types of modifier were evaluated one type based on N-substituted maleimides the others based on 2-allylamino-4,6-dichloro-1,3,5-triazine (ACCT). The modification of the PP was carried out in two stages. Firstly the PP was reactively processed with the modifier and a free radical initiator. The objective of this stage was to bind the modifier to the PP. In the second stage the modified PP was reactively processed with the glass fibre. The objective in this stage was to form a chemical bond between the bound modifier and the silane coupling agent on the surface of the glass. Two silane coupling agents were evaluated these had a aliphatic chloro group and an aliphatic amino group respectively available for reaction with the modifier. The modifiers synthesised for this work had two main functional groups. The first was a double bond for free radical addition to the PP. The second was an organic group chosen for its potential reactivity to the silane coupling agent. A preliminary investigation was carried out using maleic anhydride (MA) as the modifier, this is reactive to the amino silane coupled glass. Studies of a commercially available system were also carried out for comparison purposes. During the work it was found that the amino silane coupled glass fibres produced, without any modification being made to the PP, mechanical properties comparable to the commercial system. Further any modification added to the amino silane system failed to improve the mechanical performance and in some cases acted in the opposite fashion. This failure was evident even when a chemical bond between glass fibre and PP could be shown. In the case of the chloro silane coupled glass fibres the mechanical properties of the composite without modification were poorer than those of the commercial system. It was found that the mechanical properties of these systems could be enhanced by the modifiers, however, no system tested significantly out performed the commercial system. Of the two modifier systems tested those based on the n-substituted maleimides were more successful at enhancing mechanical properties than those based on ACCT. This was attributed to the Poor chemical binding of the ACCT based modifiers to the PP. During the work it was found that several of the modifiers improved the properties of the PP when no glass fibres were present, particularly the % elongation and impact strength. It is possible that these modifiers could be used to improve the impact performance of PP, this may be of particular interest in recycling. These modifiers have only been tested for improving the properties of glass fibre composites. The N-substituted maleimide based modifiers could be used as compatibleisers for alloys of PP and other polymers. These could function by the formation of the bond with PP via the double bond whilst the group attached to the nitrogen atom could react with the alloying polymer.

Peptidomimetic ligands for tuning integrin-mediated signalling: rational design, synthesis and theranostic applications

Integrins are α/β-heterodimeric transmembrane adhesion receptors that mediate cell-cell and cell-ECM interactions. Integrins are bidirectional signalling receptors that respond to external signals (“outside-in” signalling) and in parallel, transduce internal signals to the matrix (“inside-out” signalling), to regulate vital cellular functions including migration, survival, growth and differentiation. Therefore, dysregulation of these tightly regulated processes often results in uncontrolled integrin activation and abnormal tissue expression that is responsible for many diseases. Because of their important roles in physiological and pathological events, they represent a validated target for therapeutic and diagnostic purposes. The aim of the present Thesis was focused on the development of peptidic ligands for α4β1 and αvβ3 integrin subtypes, involved in inflammatory responses (leukocytes recruitment and extravasation) and cancer progression (angiogenesis, tumor growth, metastasis), respectively. Following the peptidomimetic strategy, we designed and synthesized a small library of linear and cyclic hybrid α/β-peptidomimetics based on the phenylureido-LDV scaffolds for the treatment of chronic inflammatory autoimmune diseases. In order to implement a fast and non-invasive diagnostic method for monitoring the course of the inflammatory processes, a flat glass-surface of dye-loaded Zeolite L-crystal nanoparticles was coated with bioactive α4β1-peptidomimetics to detect specific integrin-expressing cells as biomarkers of inflammatory diseases. Targeted drug delivery has been considered a promising alternative to overcome the pharmacokinetic limitations of conventional anticancer drugs. Thus, a novel Small-Molecule Drug Conjugate was synthesized by connecting the highly cytotoxic Cryptophycin to the tumor-targeting RGDfK-peptide through a protease-cleavable linker. Finally, in view to making the peptide synthesis more sustainable and greener, we developed an alternative method for peptide bonds formation employing solvent-free mechanochemistry and ultra-mild minimal solvent-grinding conditions in common, inexpensive laboratory equipment. To this purpose, standard amino acids, coupling agents and organic-green solvents were used in the presence of nanocrystalline hydroxyapatite as a reusable, bio-compatible inorganic basic catalyst.

Fast screening and confirmation of doping agents by UHPLC-QTOF-MS/MS

Introduction: The general strategy to perform anti-doping analysis starts with a screening followed by a confirmatory step when a sample is suspected to be positive. The screening step should be fast, generic and able to highlight any sample that may contain a prohibited substance by avoiding false negative and reducing false positive results. The confirmatory step is a dedicated procedure comprising a selective sample preparation and detection mode. Aim: The purpose of the study is to develop rapid screening and selective confirmatory strategies to detect and identify 103 doping agents in urine. Methods: For the screening, urine samples were simply diluted by a factor 2 with ultra-pure water and directly injected ("dilute and shoot") in the ultrahigh- pressure liquid chromatography (UHPLC). The UHPLC separation was performed in two gradients (ESI positive and negative) from 5/95 to 95/5% of MeCN/Water containing 0.1% formic acid. The gradient analysis time is 9 min including 3 min reequilibration. Analytes detection was performed in full scan mode on a quadrupole time-of-flight (QTOF) mass spectrometer by acquiring the exact mass of the protonated (ESI positive) or deprotonated (ESI negative) molecular ion. For the confirmatory analysis, urine samples were extracted on SPE 96-well plate with mixed-mode cation (MCX) for basic and neutral compounds or anion exchange (MAX) sorbents for acidic molecules. The analytes were eluted in 3 min (including 1.5 min reequilibration) with a S1-25 Ann Toxicol Anal. 2009; 21(S1) Abstracts gradient from 5/95 to 95/5% of MeCN/Water containing 0.1% formic acid. Analytes confirmation was performed in MS and MS/MS mode on a QTOF mass spectrometer. Results: In the screening and confirmatory analysis, basic and neutral analytes were analysed in the positive ESI mode, whereas acidic compounds were analysed in the negative mode. The analyte identification was based on retention time (tR) and exact mass measurement. "Dilute and shoot" was used as a generic sample treatment in the screening procedure, but matrix effect (e.g., ion suppression) cannot be avoided. However, the sensitivity was sufficient for all analytes to reach the minimal required performance limit (MRPL) required by the World Anti Doping Agency (WADA). To avoid time-consuming confirmatory analysis of false positive samples, a pre-confirmatory step was added. It consists of the sample re-injection, the acquisition of MS/MS spectra and the comparison to reference material. For the confirmatory analysis, urine samples were extracted by SPE allowing a pre-concentration of the analyte. A fast chromatographic separation was developed as a single analyte has to be confirmed. A dedicated QTOF-MS and MS/MS acquisition was performed to acquire within the same run a parallel scanning of two functions. Low collision energy was applied in the first channel to obtain the protonated molecular ion (QTOF-MS), while dedicated collision energy was set in the second channel to obtain fragmented ions (QTOF-MS/MS). Enough identification points were obtained to compare the spectra with reference material and negative urine sample. Finally, the entire process was validated and matrix effects quantified. Conclusion: Thanks to the coupling of UHPLC with the QTOF mass spectrometer, high tR repeatability, sensitivity, mass accuracy and mass resolution over a broad mass range were obtained. The method was sensitive, robust and reliable enough to detect and identify doping agents in urine. Keywords: screening, confirmatory analysis, UHPLC, QTOF, doping agents

mitoKATP channel activation in the postanoxic developing heart protects E-C coupling via NO-, ROS-, and PKC-dependent pathways.

Whereas previous studies have shown that opening of the mitochondrial ATP-sensitive K(+) (mitoK(ATP)) channel protects the adult heart against ischemia-reperfusion injury, it remains to be established whether this mechanism also operates in the developing heart. Isolated spontaneously beating hearts from 4-day-old chick embryos were subjected to 30 min of anoxia followed by 60 min of reoxygenation. The chrono-, dromo-, and inotropic disturbances, as well as alterations of the electromechanical delay (EMD), reflecting excitation-contraction (E-C) coupling, were investigated. Production of reactive oxygen species (ROS) in the ventricle was determined using the intracellular fluorescent probe 2',7'-dichlorofluorescin (DCFH). Effects of the specific mitoK(ATP) channel opener diazoxide (Diazo, 50 microM) or the blocker 5-hydroxydecanoate (5-HD, 500 microM), the nitric oxide synthase (NOS) inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME, 50 microM), the antioxidant N-(2-mercaptopropionyl)glycine (MPG, 1 mM), and the PKC inhibitor chelerythrine (Chel, 5 microM) on oxidative stress and postanoxic functional recovery were determined. Under normoxia, the baseline parameters were not altered by any of these pharmacological agents, alone or in combination. During the first 20 min of postanoxic reoxygenation, Diazo doubled the peak of ROS production and, interestingly, accelerated recovery of ventricular EMD and the PR interval. Diazo-induced ROS production was suppressed by 5-HD, MPG, or L-NAME, but not by Chel. Protection of ventricular EMD by Diazo was abolished by 5-HD, MPG, L-NAME, or Chel, whereas protection of the PR interval was abolished by L-NAME exclusively. Thus pharmacological opening of the mitoK(ATP) channel selectively improves postanoxic recovery of cell-to-cell communication and ventricular E-C coupling. Although the NO-, ROS-, and PKC-dependent pathways also seem to be involved in this cardioprotection, their interrelation in the developing heart can differ markedly from that in the adult myocardium.