In vitro assessment of interaction between lidocaine hydrochloride and irrigating solutions on root canal dentin: a scanning electron microscope study / Evaluación in vitro de la interacción entre el clorhidrato de lidocaína y las soluciones de irrigación en la dentina del conducto radicular: un estudio con microscopio electrónico de barrid

Aim: To investigate the precipitate formed from the interaction between 2% lidocaine hydrochloride with adrenaline (LA) with 2.5% sodium hypochlorite (NaOCl) and 0.2% chitosan nanoparticles on root canal dentin, using scanning electron microscopy (SEM). Material and Methods: Sixty mandibular premolars were decoronated, and the root length standardised. The specimens were randomly distributed into the following groups: Group 1 (control): 2% LA mixed with sterile water without root canal instrumentation, Group 2: 2% LA with 2.5% NaOCl in water without root canal instrumentation, and Group 3: 2% LA with 0.2% chitosan nanoparticles in water without root canal instrumentation. Teeth specimens were split and subjected to SEM analysis at cervical, middle, and apical root thirds. On observing precipitate formation in Group 2, 10 premolars were decoronated and treated with 2% LA and 2.5% NaOCl and subjected to root canal instrumentation. Results: Group 1 and Group 3 showed patent dentinal tubules and no precipitate formation. Group 2 showed precipitate blocking dentinal tubules in all the three sections, and the precipitate could not be removed completely after cleaning and shaping. Conclusion: NaOCl forms an insoluble precipitate on interaction with local anaesthetic solution that cannot be removed after chemo-mechanical preparation. Chitosan nanoparticles do not form any such precipitate and show patent dentinal tubules. Hence, chitosan can be used as a flushing irrigant.

Objetivo: Investigar el precipitado formado a partir de la interacción entre el clorhidrato de lidocaína al 2% con adrenalina (LA), el hipoclorito de sodio al 2,5% (NaOCl) y nanopartículas de quitosano al 0,2% en la dentina del conducto radicular, mediante microscopía electrónica de barrido (SEM). Material y Métodos: Se decoraron 60 premolares mandibulares y se estandarizó la longitud de la raíz. Los especímenes se distribuyeron aleatoriamente en los siguientes grupos: Grupo 1 (control): 2% la que fue mezclado con agua estéril sin instrumentación del conducto radicular, Grupo 2: 2% LA con 2,5% de NaOCl sin instrumentación del conducto radicular y Grupo 3: 2 % LA con 0,2% de nanopartículas de quitosano sin instrumentación del conducto radicular. Las muestras de dientes se dividieron y se sometieron a análisis SEM en los tercios radiculares cervical, medio y apical. Al observar la formación de precipitado en el Grupo 2, 10 premolares fueron decorados y tratados con LA al 2% y NaOCl al 2,5% y sometidos a instrumentación de conductos radiculares. Resultado: El Grupo 1 y el Grupo 3 mostraron túbulos dentinarios permeables y sin formación de precipitados. El grupo 2 mostró precipitado que bloqueaba los túbulos dentinarios en las tres secciones, y el precipitado no se pudo eliminar por completo después de limpieza y conformación. Conclusión: el NaOCl forma un precipitado insoluble al interactuar con la solución anestésica local que no se puede eliminar después de la preparación quimiomecánica. Las nanopartículas de quitosano no forman ningún precipitado de este tipo y muestran túbulos dentinarios permeables. Por lo tanto, el quitosano se puede utilizar como irrigante para el lavado.

Synthesis and characterization of chitosan encapsulated zinc oxide (ZnO) nanocomposite and its biological assessment in pepper (Capsicum annuum) as an elicitor for in vitro tissue culture applications.

Nanotechnology paves the way for introducing nanoscale fertilizers, pesticides, and elicitors. This study intends to address the synthesis of chitosan/zinc oxide nanocomposite (CS-ZnONP) and its biological assessment in in-vitro conditions. The zinc oxide nanoparticles (ZnONPs) were successfully coated with the chitosan (CS) polymer through a cost-effective approach. Transmission electron microscopy and Fourier transform infrared spectroscopy assessments proved the surface capping of chitosan polymer on ZnONP. The nanocomposite was more capable of improving growth and biomass than the bare ZnONPs. The application of the nanocomposite increased the concentration of chlorophylls (51%), carotenoids (70%), proline (2-fold), and proteins (about 2-fold). The supplementation of culture medium with the nanomaterials upregulated enzymatic antioxidant biomarkers (catalase and peroxidase). The activity of the phenylalanine ammonia-lyase enzyme also displayed a similar significant upward trend in response to the nano-supplements. The CS-ZnONP treatment considerably enhanced the accumulation of alkaloids (60.5%) and soluble phenols (40%), implying stimulation in secondary metabolism. The micropropagation test revealed that the CS-ZnONP treatment improved the organogenesis performance. Overall, the nanocomposite can be considered a highly potent biocompatible elicitor.

Synthesis, characterization, and assessment of cationic and anionic dye adsorption performance of functionalized silica immobilized chitosan bio-polymer.

The functionalization of polymers is still an efficient scheme to provide materials with new properties. In this paper, 4-methyl-2-(naphthalen-2-yl)-N-propylpentanamide-functionalized ethoxy-silica was successfully immobilized onto chitosan bio-polymer spherical beads to improve their adsorption characteristics. The interaction between the polymer and the functionalized silica was analyzed using FT-IR spectroscopy and SEM analysis. FT-IR investigation suggested that the interaction between chitosan and functionalized silica occurred through hydrogen bonding. The morphology of the prepared composite gel beads exhibited a spherical shape surface covered by silica particles. The unfunctionalized and functionalized beads were studied for the adsorption of methylene blue (MB) and Acid blue 25 (AB25) from water. The influence of pH, time, dye concentration, and temperature on the adsorption characteristics was investigated. The results showed that the highest adsorption amount of dyes was reached using the functionalized chitosan beads under the following conditions; pH = 5 for AB25 and pH = 6 for MB, time = 120 min, and T = 20 °C. The adsorbed yield of MB using the composite beads increased three times more than the capacity of chitosan beads and it was improved 1.4 times in the case of AB25. The mean free energy values (74.53-223.61 kJ mol-1), computed from the Dubinin-Radushkevich model suggested the chemi-sorption nature of the adsorption phenomenon.

Preparation and Characterization of Quaternized Chitosan Derivatives and Assessment of Their Antioxidant Activity.

Chitosan (CS) is an abundant and renewable polysaccharide that is reported to exhibit a great variety of beneficial properties. However, the poor solubility of chitosan in water limits its applications. In this paper, we successfully synthesized single N-quaternized (QCS) and double N-diquaternized (DQCS) chitosan derivatives, and the resulting quaternized materials were water-soluble. The degree of quaternization (DQ) of QCS and DQCS was 0.8 and 1.3, respectively. These derivatives were characterized by FTIR, ¹H NMR, 13C NMR, TGA, and SEM. Moreover, the antioxidant activity of the chitosan was evaluated by free radical scavenging ability (against DPPH-radical, hydroxyl-radical, and superoxide-radical) and ferric reducing power. Our results suggested that the antioxidant abilities were in the order of DQCS > QCS > CS, which was consistent with the number of quaternized groups. These data demonstrate that the number of quaternized groups of chitosan derivatives contributes to their antioxidant activity. Therefore, DQCS, with a higher number of quaternized groups and higher positive charge density, is endowed with high antioxidant activity, and can be used as a candidate material in food and pharmaceutical industries.

Preparation and Bioactivity Assessment of Chitosan-1-Acetic Acid-5-Flurouracil Conjugates as Cancer Prodrugs.

5-fluorouracil (5-FU) is a specific anti-cancer agent that is generally used to treat gastrointestinal, colorectal, and breast cancer. In this work, chitosan (CS) was extracted from local fish scales using an established method. 5-FU was then converted to 1-acetic acid-5-fluorouracil (FUAC) and reacted with this CS to prepare chitosan-1-acetic acid-5-fluorouracil (CS-FUAC) conjugates as a colon-specific prodrug. All compounds were characterized by Proton nuclear magnetic resonance (¹H-NMR), Fourier-transform infrared (FTIR), and UV-visible spectroscopy. The synthesized compound was subjected to a chemical stability study in phosphate buffer (0.2 M, pH 7.4) and in KCl/HCl buffer (0.2 M, pH 1.2) at different time intervals (0-240 min) and incubation at 37 °C. This revealed a significantly greater stability and a longer half-life for the CS-FUAC than for FUAC. Hemolytic activity results indicated a much lower toxicity for CS-FUAC than for 5-FU and supported consideration of CS-FUAC for further biological screening and application trials. The percentage of FUAC in the conjugates was determined by subjecting the prodrug to treatment in basic media to hydrolyze the amide bond, followed by absorbency measurements at 273 nm. The cytotoxicity studies of the conjugates were also evaluated on human colorectal cancer cell line (HT-29), which showed that the conjugates are more cytotoxic than the free drug. Therefore, CS-FUAC conjugates can be considered to represent potential colon-specific drug delivery agents, with minimal undesirable side effects, for colon cancer therapy.

Preparation and Characterization of Novel Cationic Chitosan Derivatives Bearing Quaternary Ammonium and Phosphonium Salts and Assessment of Their Antifungal Properties.

Chitosan is an abundant and renewable polysaccharide, its derivatives exhibit attractive bioactivities and the wide applications in various biomedical fields. In this paper, two novel cationic chitosan derivatives modified with quaternary phosphonium salts were successfully synthesized via trimethylation, chloride acetylation, and quaternization with tricyclohexylphosphine and triphenylphosphine. The structures and properties of synthesized products in the reactions were characterized by FTIR spectroscopy, ¹H-NMR, 31P-NMR, elemental and thermogravimetric analysis. The antifungal activities of chitosan derivatives against four kinds of phytopathogens, including Phomopsis asparagi, Watermelon fusarium, Colletotrichum lagenarium, and Fusarium oxysporum were tested using the radial growth assay in vitro. The results revealed that the synthesized cationic chitosan derivatives showed significantly improved antifungal efficiency compared to chitosan. It was reasonably suggested that quaternary phosphonium groups enabled the obviously stronger antifungal activity of the synthesized chitosans. Especially, the triphenylphosphonium-functionalized chitosan derivative inhibited the growth of Phomopsis asparagi most effectively, with inhibitory indices of about 80% at 0.5 mg/mL. Moreover, the data demonstrated that the substituted groups with stronger electron-withdrawing ability relatively possessed greater antifungal activity. The results suggest the possibility that cationic chitosan derivatives bearing quaternary phosphonium salts could be effectively employed as novel antifungal biomaterials for application in the field of agriculture.

Radiosynthesis and assessment of ocular pharmacokinetics of (124)I-labeled chitosan in rabbits using small-animal PET.

PURPOSE: The polysaccharide chitosan is a unique material for the design of ocular drug-delivery vehicles. The aim of this study was to radiolabel chitosan with iodine-124 ((124)I) for measurement of ocular pharmacokinetics in rabbits using small-animal positron emission tomography (PET). PROCEDURES: Crl:CHBB (HM) rabbits received one drop (35 µL) of either a formulation containing chitosan (0.5%, w/v) spiked with (124)I-labeled chitosan ([(124)I]chitosan) (n = 4) or a control solution of sodium [(124)I]iodide in buffer (n = 2) in the conjunctival sac of the right eye. Radioactivity distribution in the head region was measured at five different time points between 0 and 22 h after topical application. Regions of interest were manually defined in the reconstructed PET images, and activity concentration was quantified as percent applied dose (AD) per cubic centimeter tissue. RESULTS: Clear differences were observed in the ocular pharmacokinetics of the two formulations. At 3 h after application, ocular activity uptake was 0.5 ± 0.1%AD/cc for sodium [(124)I]iodide, compared to 4.7 ± 5.3%AD/cc for the [(124)I]chitosan formulation. CONCLUSIONS: We were able to show that ocular pharmacokinetics of (124)I-labeled ophthalmic formulations can be measured with small-animal PET and that [(124)I]chitosan had approximately a 2-fold increased ocular retention through the study period compared to sodium [(124)I]iodide.

Toward drug delivery into the brain: synthesis, characterization, and preliminary in vitro assessment of alkylglyceryl-functionalized chitosan nanoparticles.

A series of O-substituted alkylglyceryl chitosans with systematically varied degrees of grafting was prepared through synthetic steps that involved the protection of amino moieties via phthaloylation and employed for the formulation of aqueous nanoparticulate systems that may be capable of delivering drugs to the brain. Dynamic light scattering studies have shown that nanoparticles with physiologically relevant aqueous stabilities may be prepared following the partial quaternization of these alkylglyceryl-modified chitosans. Preliminary in vitro tests using a mouse-brain endothelial cell model have indicated the efficient cellular uptake of these nanoparticles and identified butylglyceryl chitosan and butylglyceryl N,N,N-trimethyl chitosan as promising materials for the formulation of colloidal systems that could act as drug carriers into the brain.