RESUMEN

Bone tissue engineering has been very promising. The use of scaffolds of synthetic and natural materials is an alternative to combine the advantages of both types of materials. This study aimed to evaluate electrospun polymeric matrices of pure PLLA or associated with 5% or 10% of chitosan particles loaded or not with DCPA in bone proliferation and differentiation of periodontal ligament stem cells (PDLSC). The particles and matrices were characterized by scanning electron microscopy. PDLSC were isolated from periodontal ligament fragments of human permanent teeth using the explant technique. Cell proliferation assay (Alamar Blue) was performed from 1 to 21 days of culture in clonogenic medium and Alizarin Red assay was performed after 21 days of culture in osteogenic medium. The data were analyzed using Kruskal-Wallis test, and the comparison between media was given by the Student-Newman-Keuls test (α = 0.05). On days 1 and 7 there were no statistical difference between materials regarding cell proliferation (p>0.05). The materials with 5 and 10% chitosan / DCPA showed greater proliferation than PLLA control on days 14 and 21 and the material with 10% pure chitosan was greater than the control in 21 days. Regarding the alizarin red assay, PLLA 5% chitosan, PLLA 5 and 10% chitosan / DCPA showed a greater degree of mineralization than the control and the PLLA 10% chitosan material, and they were similar to each other. We conclude that PLLA 5 and 10% chitosan / DCPA materials were able to increase both, cell proliferation and differentiation of PDLSC in bone cells. Key words:Chitosan, PLLA, polymeric matrix, electrospinning.

RESUMEN

Chitosan particles loaded with dibasic calcium phosphate anhydrous (DCPA) is a promising strategy for combining antimicrobial and osteoconduction properties in regenerative medicine. However, mostly micrometer-sized particles have been reported in the literature, limiting their use and reducing their effect in the biomedical field. We have recently overcome this limitation by developing submicrometer-sized particles with electrospray technique. The objective of this study was to understand how the process parameters control the size and properties of submicrometer chitosan particles loaded with DCPA. Solutions of 10 mg/mL chitosan and 2.5 mg/mL DCPA in a 90% acetic acid were electrosprayed under three distinct flow rate conditions: 0.2, 0.5, and 1.0 mL/h. The particles were crosslinked in a glutaraldehyde atmosphere and characterized in terms of their morphology, inorganic content, zeta potential, and minimum inhibitory concentration (MIC) against S. mutans. All conditions showed particles with two similar morphologies: one small-sized with a spherical shape and another larger-sized with a bi-concave shape. All generated a broad particle size distribution, with a similar mean size of ~ 235 nm. The addition of DCPA decreased the zeta potential for all the samples, but it was above 30 mV, indicating a low aggregation potential. The lower flow rate showed the worst efficacy for DCPA incorporation. Antimicrobial activity was greater in chitosan/DCPA particles with flow rate of 0.5 mL/h. It can be concluded that the flow rate of 0.5 mL/h presents the best compromise solution in terms of morphology, zeta potential, MIC, and inorganic content.

Asunto(s)

Antiinfecciosos , Quitosano , Tamaño de la Partícula , Fosfatos de Calcio , Antiinfecciosos/farmacología

RESUMEN

BACKGROUND: The regeneration of dental pulp, especially in cases of pulp death of immature teeth, is the goal of the regenerative endodontic procedures (REPs) that are based on tissue engineering principles, consisting of stem cells, growth factors, and scaffolds. Photobiomodulation therapy (PBMT) showed to improve dental pulp regeneration through cell homing approaches in preclinical studies and has been proposed as the fourth element of tissue engineering. However, when a blood clot was used as a scaffold in one of these previous studies, only 30% of success was achieved. The authors pointed out the instability of the blood clot as the regeneration shortcoming. Then, to circumvent this problem, a new scaffold was developed to be applied with the blood clot. The hypothesis of the present study was that an experimental injectable chitosan hydrogel would facilitate the three-dimensional spatial organization of endogenous stem cells in dental pulp regeneration with no interference on the positive influence of PBMT. METHODS: For the in vitro analysis, stem cells from the apical papilla (SCAPs) were characterized by flow cytometry and applied in the chitosan scaffold for evaluating adhesion, migration, and proliferation. For the in vivo analysis, the chitosan scaffold was applied in a rodent orthotopic dental pulp regeneration model under the influence of PBMT (660 nm; power output of 20 mW, beam area of 0.028 cm2, and energy density of 5 J/cm2). RESULTS: The scaffold tested in this study allowed significantly higher viability, proliferation, and migration of SCAPs in vitro when PBMT was applied, especially with the energy density of 5 J/cm2. These results were in consonance to those of the in vivo data, where pulp-like tissue formation was observed inside the root canal. CONCLUSION: Chitosan hydrogel when applied with a blood clot and PBMT could in the future improve previous results of dental pulp regeneration through cell homing approaches.

Asunto(s)

Quitosano , Pulpa Dental , Terapia por Luz de Baja Intensidad , Regeneración , Andamios del Tejido/química , Animales , Células Cultivadas , Quitosano/química , Quitosano/farmacología , Pulpa Dental/citología , Pulpa Dental/efectos de los fármacos , Pulpa Dental/efectos de la radiación , Humanos , Hidrogeles/química , Masculino , Ratas , Ratas Wistar , Regeneración/efectos de los fármacos , Regeneración/efectos de la radiación , Células Madre/citología , Células Madre/efectos de los fármacos , Células Madre/efectos de la radiación , Ingeniería de Tejidos

RESUMEN

This study assessed the disinfection using 70% ethanol; H2O2-quaternary ammonium salt mixture; 0.1% sodium hypochlorite and autoclaving of four 3D-printed face shields with different designs, visor materials; and visor thickness (0.5-0.75 mm). We also investigated their clinical suitability by applying a questionnaire to health workers (HW) who used them. Each type of disinfection was done 40 times on each type of mask without physical damage. In contrast, autoclaving led to appreciable damage.

Asunto(s)

COVID-19/prevención & control , Desinfectantes/farmacología , Desinfección/métodos , Equipo de Protección Personal/virología , Impresión Tridimensional , SARS-CoV-2 , COVID-19/epidemiología , Recolección de Datos , Diseño de Equipo , Etanol/farmacología , Personal de Salud , Humanos , Peróxido de Hidrógeno/farmacología , Hipoclorito de Sodio/farmacología

RESUMEN

The development of products for topical applications requires analyses of their skin effects before they are destined for the market. At present, the ban on animal use in several tests makes the search for in vitro models (such as artificial skin) necessary to characterize the risks involved. In this work, tissue engineering concepts were used to manufacture collagen-free three-dimensional scaffolds for cell growth and proliferation. Two different human skin models-reconstructed human epidermis and full-thickness skin-were developed from electrospun scaffolds using synthetic polymers such as polyethylene terephthalate, polybutylene terephthalate, and nylon 6/6. After the construction of these models, their histology was analyzed by H&E staining and immunohistochemistry. The results revealed a reconstructed epidermal tissue, duly stratified, obtained from the nylon scaffold. In this model, the presence of proteins involved in the epidermis stratification process (cytokeratin 14, cytokeratin 10, involucrin, and loricrin) was confirmed by immunohistochemistry and Western blot analysis. The nylon reconstructed human epidermis model's applicability was evaluated as a platform to perform irritation and corrosion tests. Our results demonstrated that this model is a promising platform to assess the potential of dermal irritation/corrosion of chemical products.

RESUMEN

Cellulose triacetate (CTAB) synthesized by cellulose extracted from sugarcane bagasse, and commercial cellulose acetate (CA) were used to produce nanofiber membranes contained bromelain by electrospinning technique. About 1.3 g of cellulose acetate per gram of bagasse were obtained, and both CTAB and CA was characterized by analysis of Fourier Transform Infrared Spectroscopy (FTIR) and Differential Scanning Calorimetry (DSC). The nanofiber membranes were produced by electrospinning process testing the following conditions: voltage 25 kV, flow rate 4 mL/h and distance 10 cm, using acetone/ dimethylformamide (DMF) (85:15 m/ m) to 15% cellulose triacetate (70% CA + 30% CTAB) or CA solutions. Scanning Electron Microscopy (SEM) was used to nanofiber membranes characterization. Bromelain was immobilized on the nanofiber membranes by crosslinking with glutaraldehyde and directly in the electrospinning step, the highest activity recovery was about 675% and in vitro controlled release tests were performed to semi-quantitatively evaluate the release of the enzyme bromelain thus demonstrating complete release process in 3 days.

Asunto(s)

Bromelaínas/química , Celulosa/análogos & derivados , Electroquímica/métodos , Nanofibras/química , Saccharum/química , Rastreo Diferencial de Calorimetría , Celulosa/química , Enzimas Inmovilizadas/química , Microscopía Electrónica de Rastreo , Espectroscopía Infrarroja por Transformada de Fourier

RESUMEN

Octacalcium phosphate (OCP) was synthesized yielding a combination of OCP and hydroxyapatite (HA) with a ratio of 90:10 (OCP/HA). A method was developed to functionalize the surface of the apatite using lauroyl chloride to improve the dispersion of the mineral phase in a poly(L-lactide) (PLLA) polymeric matrix. Infrared spectra and thermal gravimetric analysis confirmed the presence of laurate on the surface of calcium phosphate (CaP) particles. Neat HA particles were also functionalized with lauryl chloride for comparative purposes. PLLA/OCP/HA-laurate (PLLA/OCP/HA-L) and PLLA/HA-laurate (PLLA/HA-L) composites were fabricated by electrospinning method. The presence of the functional groups resulted in significant improvement of the dispersion of OCP/HA and HA particles into the polymeric matrix, allowing inclusion of up to 40% of mineral phase. Electrospun fibrous biocomposites of PLLA/CaP containing up to 40% in mineral phase were obtained without compromising their mechanical properties. Measurements of mass loss and calcium release in vitro showed that OCP/HA is more soluble than HA. The bioactivity of the composites was investigated by simulated body fluid test (SBF). Although both PLLA/OCP/HA-L and PLLA/HA-L fibers can form CaP crystals on their surface after exposition in SBF, the results demonstrate a significant enhancement in mineralization when OCP/HA is the mineral phase in the composite instead neat HA. Furthermore, the obtained PLLA/OCP/HA-L electrospun fibers favored the proliferation and differentiation of stem cells from human exfoliated deciduous teeth and mouse calvaria-derived preosteoblastic cells into mineralized osteoblasts. This new material is proposed as fast degrading CaP biocomposite for bone and teeth applications.

Asunto(s)

Materiales Biocompatibles/química , Materiales Biocompatibles/farmacología , Fosfatos de Calcio/química , Diferenciación Celular/efectos de los fármacos , Poliésteres/química , Células Madre/citología , Células Madre/efectos de los fármacos , Células 3T3 , Animales , Cinética , Ratones , Ratones Endogámicos BALB C , Osteogénesis/efectos de los fármacos

RESUMEN

The development of a biodegradable material with antimicrobial properties for local applications is required in the prevention and treatment of infectious diseases. The objective of this study was to produce blends of poly-L-lactide acid (PLLA) synthetic polymer associated with several antimicrobials, as an alternative in the prevention and treatment of infections, as well as to evaluate its cytotoxicity, release of antimicrobials and inhibit bacteria growth. Blends of PLLA added with 20% Amoxicillin, Metronidazole, Clindamycin or Azithromicyn were used to produce Films (F) or Meshs (M) by casting and electrospinning methods, respectively. Standardized discs of the films and meshs were stored in buffer solutions (pH 5 or 7.4) and aliquots were analyzed by high performance chromatography (HPLC) during 168 hours. Cytotoxicity on human gingival fibroblasts was tested after 24, 48 and 72h by MTT reaction. The antimicrobial capacity was determined against P. gingivalis and S. pyogenes. The specimens were weighed after 3 and 6 months of storage for degradation analysis. SEM was performed to control interfaces and degradation. Antimicrobials presented a continuous and exponential drug release. Analysis showed that both M and F were able to inhibit S. pyogenes and P. gingivalis growth, indicating the release of active antimicrobial agents. The products were not toxic to the fibroblasts. Amoxicillin-film showed more degradation than PLLA at both pHs (p < 0.05), whereas Azithromycin-meshes were more degraded than PLLA at pH 7.4 (p < 0.05). PLLA association with antimicrobials is biocompatible and may represent a potential tool for the local delivery of antimicrobials.

Asunto(s)

Antiinfecciosos/farmacología , Materiales Biocompatibles/farmacología , Viabilidad Microbiana/efectos de los fármacos , Poliésteres/farmacología , Polímeros/farmacología , Porphyromonas gingivalis/efectos de los fármacos , Streptococcus pyogenes/efectos de los fármacos , Antiinfecciosos/química , Materiales Biocompatibles/química , Técnicas de Cultivo de Célula , Combinación de Medicamentos , Humanos , Ensayo de Materiales , Polímeros/química , Mallas Quirúrgicas

RESUMEN

Magnetic scaffolds with different charge densities were prepared using magnetic nanoparticles (MNP) and xanthan gum (XG), a negatively charged polysaccharide, or hydroxypropyl methylcellulose (HPMC), an uncharged cellulose ether. XG chains were crosslinked with citric acid (cit), a triprotic acid, whereas HPMC chains were crosslinked either with cit or with oxalic acid (oxa), a diprotic acid. The scaffolds XG-cit, HPMC-cit and HPMC-oxa were characterized by scanning electron microscopy (SEM), inductively coupled plasma atomic emission spectroscopy (ICP-AES), superconducting quantum interference device (SQUID) magnetometry, contact angle and zeta-potential measurements. In addition, the flux of Ca2+ ions through the scaffolds was monitored by using a potentiometric microsensor. The adhesion and proliferation of murine fibroblasts (NIH/3T3) on XG-cit, XG-cit-MNP, HPMC-cit, HPMC-cit-MNP, HPMC-oxa and HPMC-oxa-MNP were evaluated by MTT assay. The magnetic scaffolds presented low coercivity (<25Oe). The surface energy values determined for all scaffolds were similar, ranging from 43mJm-2 to 46mJm-2. However, the polar component decreased after MNP incorporation and the dispersive component of surface energy increased in average 1mJm-2 after MNP incorporation. The permeation of Ca2+ ions through XG-cit-MNP was significantly higher in comparison with that on XG-cit and HPMC-cit scaffolds, but through HPMC-cit-MNP, HPMC-oxa and HPMC-oxa-MNP scaffolds it was negligible within the timescale of the experiment. The adhesion and proliferation of fibroblasts on the scaffolds followed the trend: XG-cit-MNP>XG-cit>HPMC-cit, HPMC-cit-MNP, HPMC-oxa, HPMC-oxa-MNP. A model was proposed to explain the cell behavior stimulated by the scaffold charge, MNP and Ca2+ ions permeation.

Asunto(s)

Calcio/metabolismo , Derivados de la Hipromelosa/farmacología , Campos Magnéticos , Nanopartículas de Magnetita/química , Polisacáridos Bacterianos/farmacología , Andamios del Tejido/química , Animales , Calcio/química , Adhesión Celular/efectos de los fármacos , Proliferación Celular/efectos de los fármacos , Células Cultivadas , Derivados de la Hipromelosa/química , Iones/química , Iones/metabolismo , Ratones , Estructura Molecular , Células 3T3 NIH , Polisacáridos Bacterianos/química

RESUMEN

Abstract The development of a biodegradable material with antimicrobial properties for local applications is required in the prevention and treatment of infectious diseases. The objective of this study was to produce blends of poly-L-lactide acid (PLLA) synthetic polymer associated with several antimicrobials, as an alternative in the prevention and treatment of infections, as well as to evaluate its cytotoxicity, release of antimicrobials and inhibit bacteria growth. Blends of PLLA added with 20% Amoxicillin, Metronidazole, Clindamycin or Azithromicyn were used to produce Films (F) or Meshs (M) by casting and electrospinning methods, respectively. Standardized discs of the films and meshs were stored in buffer solutions (pH 5 or 7.4) and aliquots were analyzed by high performance chromatography (HPLC) during 168 hours. Cytotoxicity on human gingival fibroblasts was tested after 24, 48 and 72h by MTT reaction. The antimicrobial capacity was determined against P. gingivalis and S. pyogenes. The specimens were weighed after 3 and 6 months of storage for degradation analysis. SEM was performed to control interfaces and degradation. Antimicrobials presented a continuous and exponential drug release. Analysis showed that both M and F were able to inhibit S. pyogenes and P. gingivalis growth, indicating the release of active antimicrobial agents. The products were not toxic to the fibroblasts. Amoxicillin-film showed more degradation than PLLA at both pHs (p < 0.05), whereas Azithromycin-meshes were more degraded than PLLA at pH 7.4 (p < 0.05). PLLA association with antimicrobials is biocompatible and may represent a potential tool for the local delivery of antimicrobials.

Asunto(s)

Humanos , Poliésteres/farmacología , Polímeros/farmacología , Streptococcus pyogenes/efectos de los fármacos , Materiales Biocompatibles/farmacología , Porphyromonas gingivalis/efectos de los fármacos , Viabilidad Microbiana/efectos de los fármacos , Antiinfecciosos/farmacología , Polímeros/química , Mallas Quirúrgicas/efectos adversos , Materiales Biocompatibles/química , Ensayo de Materiales , Técnicas de Cultivo de Célula , Combinación de Medicamentos , Antiinfecciosos/química

RESUMEN

Polypyrrole (PPy) was electropolymerized in xanthan hydrogels (XCA), resulting in electroactive XCAPPy scaffolds with (15 ± 3) wt.% PPy and (40 ± 10) µm thick. The physicochemical characterization of hybrid XCAPPy scaffolds was performed by means of cyclic voltammetry, swelling tests, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analyses (TGA), scanning electron microscopy (SEM), atomic force microscopy (AFM) and tensile tests. XCAPPy swelled~80% less than XCA. FTIR spectra and thermal analyses did not evidence strong interaction between PPy and XCA matrix. XCAPPy presented a porous stratified structure resulting from the arrangement of PPy chains parallel to XCA surface. Under stress XCAPPy presented larger strain than neat XCA probably due to the sliding of planar PPy chains. The adhesion and proliferation of fibroblasts onto XCA and XCAPPy were evaluated in the absence and in the presence of external magnetic field (EMF) of 0.4T, after one day, 7 days, 14 days and 21 days. Fibroblast proliferation was more pronounced onto XCAPPy than onto XCA, due to its higher hydrophobicity and surface roughness. EMF stimulated cell proliferation onto both scaffolds.

Asunto(s)

Polímeros/química , Polisacáridos Bacterianos/química , Pirroles/química , Ingeniería de Tejidos/métodos , Andamios del Tejido/química , Células Cultivadas , Fibroblastos/citología , Humanos , Campos Magnéticos

RESUMEN

In this work xanthan-nanohydroxyapatite (XnHAp) and its equivalent strontium substituted (XnHApSr) were synthesized by the precipitation of nanohydroxyapatite in xanthan aqueous solution, characterized and compared to conventional hydroxyapatite particles (HAp). XnHAp and XnHApSr were less crystalline than HAp, as revealed by X-ray diffraction. Xanthan chains enriched the surface of XnHAp and XnHApSr particles, increasing the zeta potential values from -(7±1)mV, determined for HAp, to -(17±3)mV and -(25±3)mV, respectively. This effect led to high colloidal stability of XnHAp and XnHApSr dispersions and acicular particles (140±10)nm long and (8±2)nm wide, as determined by scanning electron microscopy and atomic force microscopy. XnHAp and XnHApSr particles were added to xanthan hydrogels to produce compatible nanocomposites (XCA/XnHAp and XCA/XnHApSr). Dried nanocomposites presented surface energy, Young's modulus and stress at break values comparable to those determined for bare xanthan matrix. Moreover, adding XnHAp or XnHApSr nanoparticles to xanthan hydrogel did not influence its porous morphology, gel content and swelling ratio. XCA/XnHAp and XCA/XnHApSr composites proved to be suitable for osteoblast growth and particularly XCA/XnHapSr composites induced higher alkaline phosphatase activity.

Asunto(s)

Durapatita/química , Nanocompuestos/química , Polisacáridos Bacterianos/química , Animales , Línea Celular , Proliferación Celular/efectos de los fármacos , Módulo de Elasticidad , Hidrogeles/química , Hidrogeles/metabolismo , Hidrogeles/toxicidad , Ratones , Nanocompuestos/toxicidad , Osteoblastos/citología , Porosidad , Estrés Mecánico

RESUMEN

Acellular biological tissues, including bovine pericardium (BP), have been proposed as biomaterial for tissue engineering. BP is usually modified chemically to improve mechanical and biological properties using glutaraldehyde, the standard reagent for preservation of fresh bioprosthetic materials. Glutaraldehyde-fixed BP (Glut-BP), the most widely used material in heart valve manufacture, has been associated with calcification in vivo. In an attempt to reduce this issue and maintain its biocompatibility, this study assesses the physical properties and cytotoxicity of lyophilized BP treated with poly (vinylpyrrolidone-co-acrolein) (PVPAC-BP), a novel copolymer, as a substitute for glutaraldehyde. For that, PVPAC-BP surface ultrastructure, elastic function, water uptake and tissue calcification were evaluated. For the analysis of biocompatibility, fibroblasts (3T3-L1) and endothelial cells (HUVEC) were cultured on PVPAC-BP, Untreated-BP and Glut-BP. Nitric oxide (NO) release assay, fluorescence and SEM images of endothelial cells adhered on scaffolds were also performed. As results, the data show some advantages of PVPAC-BP over the Glut-BP. The PVPAC-BP maintains partially the original ultrastructure and elastic properties, improves scaffold hydration, and presents less calcium phosphate deposits. The cells demonstrated strong attachment, high proliferation rate, and formation of a monolayer on PVPAC-BP. Attached cells were also able to release NO de-monstrating regular metabolism. In conclusion, PVPAC may be considered as a promising alternative to BP treatment improving the efficiency of cell attachment and proliferation and also avoid immunogenicity.

Asunto(s)

Acroleína/farmacología , Bioprótesis , Supervivencia Celular/efectos de los fármacos , Glutaral/farmacología , Prótesis Valvulares Cardíacas , Pericardio/citología , Povidona/análogos & derivados , Povidona/química , Povidona/farmacología , Células 3T3-L1 , Acroleína/química , Animales , Materiales Biocompatibles , Calcinosis/patología , Fosfatos de Calcio/química , Bovinos , Adhesión Celular/efectos de los fármacos , Perros , Elasticidad , Células Endoteliales/efectos de los fármacos , Fluorescencia , Liofilización , Ratones , Microscopía Electrónica de Rastreo , Óxido Nítrico/química , Pericardio/efectos de los fármacos , Propiedades de Superficie , Ingeniería de Tejidos , Andamios del Tejido , Agua/química

RESUMEN

We describe a fast and simple method to prepare composite films of magnetite nanoparticles and xanthan networks. The particles are distributed close to hybrid film surface, generating a coercivity of 27 ± 2 Oe at 300 K. The proliferation of fibroblast cells on the hybrid composites was successful, particularly when an external magnetic field was applied.

Asunto(s)

Fibroblastos/citología , Fibroblastos/metabolismo , Magnetismo , Nanopartículas de Magnetita/química , Polisacáridos Bacterianos/química , Proliferación Celular , Técnicas Químicas Combinatorias , Fibroblastos/química , Propiedades de Superficie , Factores de Tiempo

RESUMEN

In this work xanthan chains were crosslinked by esterification reaction at 165 °C either in the absence or in the presence of citric acid. Higher crosslinking density was obtained using citric acid, as evidenced by its lower swelling degree. Tensiometry, a very precise and sensitive technique, was applied to study swelling rates and diffusion mechanisms of water, which was initially quasi-Fickian, controlled by wicking properties, changing to Fickian or Anomalous, depending on hydrogel composition. Hydrogels swelling degree increased at high pH values, due to electrostatic repulsion and ester linkages rupture. Equilibrium swelling degree was affected by salts, depending on gel composition and kind of salt. Effects could be explained by interaction between ions and polymeric chains, EPA/EPD ability of water or osmotic gradient.

Asunto(s)

Hidrogeles/química , Polisacáridos Bacterianos/química , Polisacáridos Bacterianos/síntesis química , Técnicas de Química Sintética , Ácido Cítrico/química , Difusión , Concentración de Iones de Hidrógeno , Agua/química

RESUMEN

We previously reported that intraerythrocytic malaria parasites have their development synchronized by melatonin and other products of tryptophan catabolism (i.e. serotonin, N-acetylserotonin and tryptamine). Here, we show that N(1)-acetyl-N(2)-formyl-5-methoxykynuramine (AFMK), a product of melatonin degradation, synchronizes Plasmodium chabaudi and Plasmodium falciparum. The synchronization is abrogated with a melatonin receptor antagonist, luzindole. We established quantitatively that a differential AFMK production occurred within the intraerythrocytic stages of rodent malaria parasite Plasmodium chabaudi (ring, trophozoite and schizont), when the infected erythrocytes were previously incubated with melatonin. Measurement of AFMK formation in P. chabaudi after incubation with melatonin at a concentration of 500 nmol/L revealed the following values for AFMK production: ring 0.1 +/- 0.1 nmol/L, trophozoite 22.9 +/- 0.5 nmol/L, schizont 29 +/- 5 nmol/L. Confocal and spectrofluorophotometer experiments with isolated parasites and infected-RBC, loaded with calcium indicator Fluo-4 showed that AFMK elicits an increase in the cytosol calcium concentration in these parasites. Our data suggest that AFMK could have an important role in modulating the cell cycle of malaria parasites mainly in the late stages (trophozoite and schizont).

Asunto(s)

Ciclo Celular/efectos de los fármacos , Eritrocitos/metabolismo , Kinuramina/análogos & derivados , Plasmodium chabaudi/efectos de los fármacos , Plasmodium falciparum/efectos de los fármacos , Animales , Eritrocitos/parasitología , Kinuramina/metabolismo , Kinuramina/farmacología , Melatonina/metabolismo , Ratones , Ratones Endogámicos BALB C

RESUMEN

The use of poly(N-vinyl-2-pyrrolidone) (PVP) hydrogel-supported luminol chemiluminescence (CL) for the automatic determination of hydrogen peroxide and the quantification of the antiradical capacity of Trolox is described. The hydrogel containing luminol and hemin is prepared directly on a 96-well microplate and can be stored for up to 3 months without significant decrease in CL quantum yields. Furthermore, this system can also be used as a secondary light standard for the calibration of microplate luminometers.

Asunto(s)

Hidrogeles/química , Peróxido de Hidrógeno/análisis , Mediciones Luminiscentes/instrumentación , Luminol/química , Povidona/química , Antioxidantes/química , Antioxidantes/farmacología , Automatización , Calibración , Cromanos/química , Cromanos/farmacología , Hemina/química , Mediciones Luminiscentes/métodos , Estructura Molecular

RESUMEN

The chemiluminescent oxidation of luminol by hydrogen peroxide in the presence of hemin is revisited in an UV-C cross-linked PVP hydrogel. Chemiluminescence properties such as initial light intensity (I(0)), area of emission (S) and observed rate constants (k(obs)) are studied, varying the concentration of all reactants using a multivariate factorial approach.

Asunto(s)

Hemina/química , Hidrogeles/síntesis química , Luminiscencia , Luminol/química , Povidona/química , Reactivos de Enlaces Cruzados/química , Análisis Factorial , Hemina/efectos de la radiación , Hidrogeles/química , Peróxido de Hidrógeno/química , Concentración de Iones de Hidrógeno , Cinética , Luminol/efectos de la radiación , Estructura Molecular , Oxidación-Reducción , Povidona/efectos de la radiación , Rayos Ultravioleta

RESUMEN

Photoacid generators (PAG) are chemical systems where light absorption renders strong acid formation, typically with quantum yields greater than one. Many compounds bearing halogen atoms are reported to produce hydrogen halides upon photolysis. Here, alpha-chloroxylene derivatives (ortho, meta and para) were subject of a photolysis study in order to: (i) determine the operative mechanism, (ii) identify the products formed and (iii) quantify the amount of HCl formed. Product structure and quantum yields of HCl formation where determined for the photolysis of alpha-chloro-o-xylene (1), alpha-chloro-m-xylene (2), alpha-chloro-p-xylene (3), alpha, alpha'-dichloro-o-xylene (4), alpha, alpha'-dichloro-m-xylene (5) and alpha, alpha'-dichloro-p-xylene (6) in apolar (benzene, cumene, ethylbenzene, toluene and isooctane) and polar (methanol, n-propanol, isopropyl alcohol) solvents. Some of these compounds were analysed by laser flash photolysis in argon-purged isooctane as solvent to examine the possible reaction intermediates involved. The observed products are derived from typical radical reactions like recombination, dimerization and hydrogen abstraction from the starting compound or from solvents. The formation of HCl is expected as the result of C-Cl homolysis followed by hydrogen abstraction by chlorine atom. The results showed yields ranging from 1.2 to 18, depending on the conditions used. These numbers indicate the potential use of these compounds as PAG systems for the deep UV region.