Interaction of ciprofloxacin and probe compounds with palygorskite PFl-1

The adsorption of ciprofloxacin (CIP) as well as probe compounds, phenylpiperazine (PP) (NH) and fluorochloroquinolone carboxylic acid (FCQCA) (COOH), on palygorskite (PFl-1) obeyed the Langmuir isotherm at pH 2, 7, and 11 except the FCQCA adsorption at pH 2. The CIP and PP adsorption onto PFl-1 was 98-160 mmol/kg. In neutral solution the total amount of exchangeable cations desorbed correlated with the adsorbed amount of CIP and PP well with a slope of 0.9-1, indicating a cation-exchange mechanism. A low amount of FCQCA adsorption of 27-57 mmol/kg was observed and the amount of exchangeable cations desorbed negatively correlate with the amount of FCQCA adsorbed as influenced by surface complexation or cation bridging. FTIR band shifting due to the ring-stretch vibration of PP and the keto-carbonyl group stretching of FCQCA suggested strong interactions as PP and FCQCA absorbed on PFl-1 in neutral solution. In the interaction of CIP with PFl-1, the piperazine-amine group played an important role in cation-exchange interaction in acidic to neutral solution, while the deprotonated keto carbonyl group actively partook in cation bridging or surface complexation with metal cations adsorbed on PFl-1 when the CIP was in anionic form in alkaline solution.

[Photodegradation of Ciprofloxacin Hydrochloride in the Aqueous Solution Under UV]

Effects of ciprofloxacin hydrochloride (CIP) initial concentration, Pb (NO3) 2, Cd (NO3) 2, PbCl2 and CdCl2 on the photodegradation of CIP using UV irradiation were investigated. The experiments results showed that UV irradiation could lead to effective removal of CIP, but there was no CIP degradation in dark. The photodegradation rate of CIP reduced with increasing initial concentration under UV irradiation. Pb(NO3)2 and Cd(NO3)2 (except for the experiment group of 0.006 mmol x L(-1)) could enhance CIP photodegradation, and the half-life of CIP gradually increased with increasing molar ratio between heavy metal and CIP ( with the decreasing concentration of nitrate). With increasing molar ratio (with the decreasing concentration of chlorate), PbCl2 and CdCl2 first promoted and then inhibited the CIP photodegradation.

Optimization and modelling using the response surface methodology (RSM) for ciprofloxacin removal by electrocoagulation

In this study, response surface methodology (RSM) was used to investigate the effects of different operating conditions on the removal of ciprofloxacin (CIP) by the electrocoagulation (EC) with pure iron electrodes. Box-Behnken design was used for the optimization of the EC process and to evaluate the effects and interactions of process variables such as applied current density, process time, initial CIP concentration and pH on the removal of CIP by the EC process. The optimum conditions for maximum CIP removal (86.6%) were found as pH = 4; Co = 5 mg.L(1-); Id = 4.325 mA.cm(2-); tprocess = 10 min. The model adequacy and the validity of the optimization step were confirmed with additional experiments which were performed under the proposed optimum conditions. The predicted CIP removal as 86.6% was achieved at each experiment by using the optimum conditions. These results specify that the RSM is a useful tool for optimizing the operational conditions for CIP removal by the EC process.

Kinetic study of antibiotic ciprofloxacin ozonation by MWCNT/MnO2 using Monte Carlo simulation

Kinetic Monte Carlo simulation was used to investigate kinetics of antibiotic ciprofloxacin degradation by direct and heterogeneous catalytic (MnO2 and carbon nano-tube loaded with MnO2) ozonation. The reaction kinetic mechanisms of each system have been obtained. The rate constant values for the each step of the reaction mechanisms were attained as adjustable parameters by kinetic Monte Carlo simulation. The carbon nano-tube loaded with MnO2 plays important role as catalyst in the ciprofloxacin ozonation by increasing reactivity of ozone and ciprofloxacin drug on the surface of carbon nano-tube. Optimized amount of ozone and catalysts were obtained via studying the effect of inlet ozone concentration and initial amount of catalyst on the rate of ciprofloxacin degradation using Monte Carlo simulation. The simulation results of this study have reasonably agreement with the present experimental data for the ozonation of ciprofloxacin drug.

Controlled Antibiotics Release System through Simple Blended Electrospun Fibers for Sustained Antibacterial Effects

Implantation of sustained antibacterial system after abdominal surgery could effectively prevent complicated intra-abdominal infection. In this study, a simple blended electrospun membrane made of poly(D,L-lactic-co-glycolide) (PLGA)/poly(dioxanone) (PDO)/Ciprofloxacin hydrochloride (CiH) could easily result in approximately linear drug release profile and sustained antibacterial activity against both Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). The addition of PDO changed the stack structure of PLGA, which in turn influenced the fiber swelling and created drug diffusion channels. It could be a good candidate for reducing postoperative infection or be associated with other implant to resist biofilm formation.

Preparation of a specific bamboo based activated carbon and its application for ciprofloxacin removal

The studied bamboo based activated carbon (BbAC) with high specific surface area (SSA) and high micro pore volume was prepared from bamboo scraps by the combined activation of H3PO4 and K2CO3. The BbAC was characterized based on the N2 adsorption isotherm at 77K. The results showed that the SSA and pore volume of BbAC increased with increasing impregnation ratio and reached maxima at the impregnation ratio of 3:1 at 750°C. Under these optimal conditions, the BbAC obtained could have a maximum SSA of 2237 m(2)/g and a maximum total pore volume of 1.23 cm(3)/g with the micro pore ratio of more than 90%. The adsorption performance of ciprofloxacin (CIP) on the BbAC was determined at 298 K. The Langmuir and Freundlich models were employed to describe the adsorption equilibrium and the kinetic data were fitted by pseudo first-order and pseudo second-order kinetic models. The results showed that the Langmuir model and the pseudo second-order kinetic model presented better fittings for the adsorption equilibrium and kinetics data, respectively. The maximum adsorption amount of CIP (613 mg/g) on the BbAC was much higher than the report in the literature. Conclusively, the BbAC could be a promising adsorption material for CIP removal from water.

Kinetics and Mechanisms of Ciprofloxacin Oxidation on Hematite Surfaces

Adsorption of antibiotics at mineral surfaces has been extensively studied over the past 20 years, yet much remains to be learned on their interfacial properties and transformation mechanisms. In this study, interactions of Ciprofloxacin (CIP), a fluoroquinolone antibiotic with two sets of synthetic nanosized hematite particles, with relatively smooth (H10, 10-20 nm in diameter) and roughened (H80, 80-90 nm in diameter) surfaces, were studied by means of liquid chromatography (LC), mass spectrometry (MS), and spectroscopy (vibration and X-ray photoelectron). Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy provides evidence for inner-sphere bidentate complex formation of CIP at hematite surfaces in 0.01 M NaCl, irrespective of pH and particle size. ATR-FTIR spectroscopy also revealed that the sorbed mother CIP molecule decayed to other surface species over a period of at least 65 h. This was supported by the detection of three daughter products in the aqueous phase by LC/MS. The appearance of NH3(+) groups during the course of these experiments, revealed by cryogenic XPS, provides further evidence that CIP oxidation proceeds through an opening of piperazine ring via N-dealkylation. Additional in vacuo FTIR experiments under temperature-programmed desorption also showed that oxidation of sorbed byproducts were effectively degraded beyond 450 °C, a result denoting considerably strong (inter)molecular bonds of both mother and daughter products. This work also showed that rougher, possibly multidomainic particles (H80) generated slower rates of CIP decomposition but occurring through more complex schemes than at smoother particle surfaces (H10). This work thus uncovered key aspects of the binding of an important antibiotic at iron oxide surfaces, and therefore provided additional constraints to our growing understanding of the fate of emerging contaminants in the environment.

Activation of Manganese Oxidants with Bisulfite for Enhanced Oxidation of Organic Contaminants: The Involvement of Mn(III)

MnO4(-) was activated by HSO3(-), resulting in a process that oxidizes organic contaminants at extraordinarily high rates. The permanganate/bisulfite (PM/BS) process oxidized phenol, ciprofloxacin, and methyl blue at pHini 5.0 with rates (kobs ≈ 60-150 s(-1)) that were 5-6 orders of magnitude faster than those measured for permanganate alone, and ∼5 to 7 orders of magnitude faster than conventional advanced oxidation processes for water treatment. Oxidation of phenol was fastest at pH 4.0, but still effective at pH 7.0, and only slightly slower when performed in tap water. A smaller, but still considerable (∼3 orders of magnitude) increase in oxidation rates of methyl blue was observed with MnO2 activated by HSO3(-) (MO/BS). The above results, time-resolved spectroscopy of manganese species under various conditions, stoichiometric analysis of pH changes, and the effect of pyrophosphate on UV absorbance spectra suggest that the reactive intermediate(s) responsible for the extremely rapid oxidation of organic contaminants in the PM/BS process involve manganese(III) species with minimal stabilization by complexation. The PM/BS process may lead to a new category of advanced oxidation technologies based on contaminant oxidation by reactive manganese(III) species, rather than hydroxyl and sulfate radicals.

Electrochemical incineration of the antibiotic ciprofloxacin in sulfate medium and synthetic urine matrix

The degradation of 100 mL of 0.245 mM of the antibiotic ciprofloxacin in 0.05 M Na2SO4 at pH 3.0 has been studied by electrochemical oxidation with electrogenerated H2O2 (EO-H2O2), electro-Fenton (EF), UVA photoelectro-Fenton (PEF) and solar PEF (SPEF). Electrolyses were performed with a stirred tank reactor using either a boron-doped diamond (BDD) or Pt anode and an air-diffusion cathode. In EF, PEF and SPEF, ciprofloxacin was rapidly removed due to its oxidation with (•)OH formed from Fenton's reaction between added Fe(2+) and H2O2 generated at the cathode. The larger electrochemical incineration of the antibiotic was achieved by SPEF with BDD with 95% mineralization thanks to the additional attack by hydroxyl radicals formed from water oxidation at the BDD anode surface and the photolysis of final Fe(III)-oxalate and Fe(III)-oxamate species from sunlight. Up to 10 primary intermediates and 11 hydroxylated derivatives were identified by LC-MS, allowing the proposal of a reaction sequence for ciprofloxacin mineralization. A different behavior was found when the same antibiotic concentration was oxidized in a synthetic urine matrix with high urea content and a mixture of PO4(3-), SO4(2-) and Cl(-) ions. Since Fenton's reaction was inhibited in this medium, only EO and EO-H2O2 processes were useful for mineralization, being the organics mainly degraded by HClO formed from Cl(-) oxidation. The EO process with a BDD/stainless steel cell was found to be the most powerful treatment for the urine solution, yielding 96% ciprofloxacin removal and 98% mineralization after 360 min of electrolysis at optimum values of pH 3.0 and current density of 66.6 mA cm(-2). The evolution of released inorganic ions was followed by ion chromatography.

Sulfamethoxazole and ciprofloxacin removal using a horizontal-flow anaerobic immobilized biomass reactor

The antibiotics sulfamethoxazole (SMTX) and ciprofloxacin (CIP) are commonly used in human and veterinary medicine, which explains their occurrence in wastewater. Anaerobic reactors are low-cost, simple and suitable technology to wastewater treatment, but there is a lack of studies related to the removal efficiency of antibiotics. To overcome this knowledge gap, the objective of this study was to evaluate the removal kinetics of SMTX and CIP using a horizontal-flow anaerobic immobilized biomass reactor. Two different concentrations were evaluated, for SMTX 20 and 40 μg L(-1); for CIP 2.0 and 5.0 μg L(-1). The affluent and effluent analysis was carried out in liquid chromatography/tandem mass spectrometry (LC-MS/MS) with the sample preparation procedure using an off-line solid-phase extraction. This method was developed, validated and successfully applied for monitoring the affluent and effluent samples. The removal efficiency found for both antibiotics at the two concentrations studied was 97%. Chemical oxygen demand (COD) exhibited kinetic constants that were different from that observed for the antibiotics, indicating the absence of co-metabolism. Also, though the antibiotic concentration was increased, there was no inhibitory effect in the removal of COD and antibiotics.

[Synthesis and antitumor activity of fluoroquinolon-3-yl-s-triazole sulfide ketones and their derivatives from ciprofloxacin]

To discover an efficient strategy for the conversion of the antibacterial activity of fluoroquinolones into the antitumor activity, the three series of C-3 s-triazole-based derivatives including sulfide ketones (6a-6g), thiosemicarbazones (7a-7g) and fused heterocyclic thiazolotriazoles (8a-8g) were synthesized from ciprofloxacin (1), respectively. The structures were characterized by elemental analysis and spectral data. The antitumor activity was tested against three tumor cell lines (Hep-3B, Capan-1 and HL60) using the MTT assay. The three types of compounds all exhibited stronger anti-proliferative activities than ciprofloxacin in the test. The order of their activities was in compounds 7>8>6, and the order of selectivity against cancer cell lines was Capan-1, Hep-3B and HL60. Meanwhile, the SAR revealed that some compounds with electron-drawing group substituted such as fluoro- and nitro-phenyl compounds (6f, 7f, 8f) and (6g, 7g, 8g) displayed more significant activity than the control compounds, especially the IC50 values of thiosemicarbazone compounds 7f and 7g against Capan-1 was comparable to doxorubicin. Thus, a five-membered triazole as the C-3 bioisostere modified with the functionalized side-chain of sulfide-ketone thiosemicarbazone warrants special attention and further investigation.

Radiolytic decomposition of ciprofloxacin using γ irradiation in aqueous solution

Gamma irradiation-induced decomposition of ciprofloxacin (CIP) was elucidated with different additives, such as CO3 (2-), NO3 (-), NO2 (-), humic acid, methanol, 2-propanol, and tert-butanol. The results show that low initial concentration and acidic condition were favorable for CIP removal during γ irradiation. By contrast, radiolytic decomposition of CIP was inhibited with the addition of anions and organic additives. As a strong carcinogen, Cr(6+) was especially mixed with CIP to produce combined pollution. It is noteworthy that the removal of the mixture of CIP and Cr(6+) presented a synergistic effect; the degradation efficiency of the two pollutants was markedly improved compared to that of the single pollutant during γ irradiation. Based on the results of quantum chemical calculations and LC-MS analysis, we determined seven kinds of degradation intermediates and presented the CIP degradation pathways, which were mainly attributed to the oxidation process of hydroxyl radicals OH· and the direct decomposition of CIP molecules.

Sunlight-induced degradation of fluoroquinolones in wastewater effluent: Photoproducts identification and toxicity

The photodegradation of Ciprofloxacin (CIP), Enrofloxacin (ENR), Danofloxacin (DAN), Marbofloxacin (MAR) and Levofloxacin (LEV), five widely used fluoroquinolones (FQs), was studied in urban WWTP secondary effluent, under solar light. The degradation profiles and the kinetic constants were determined at the micrograms per litre levels (20-50 μg L(-1)). The photo-generated products were identified by high-pressure liquid chromatography coupled to electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS). The toxicity of the photoproducts was assessed by Vibrio fischeri light emission inhibition assay performed on irradiated and not-irradiated FQs solutions, at environmentally significant concentrations. Attention was focused on the evaluation of the photoproducts contribution to the overall biotoxic effect of these emerging pollutants. Data from chronic exposure experiments (24-48 h) were primarily considered. Results confirmed the major usefulness of chronic toxicity data with respect to the acute assay ones and proved the not negligible biotoxicity of the FQs photodegradation products.

Synthesis of ciprofloxacin dimers for evaluation of bacterial permeability in atypical chemical space

We describe the synthesis and evaluation of a library of variably-linked ciprofloxacin dimers. These structures unify and expand on the use of fluoroquinolones as probes throughout the antibiotic literature. A dimeric analog (19) showed enhanced inhibition of its intracellular target (DNA gyrase), and translation to antibacterial activity in whole cells was demonstrated. Overall, cell permeation was governed by physicochemical properties and bacterial type. A principal component analysis demonstrated that the dimers occupy a unique and privileged region of chemical space most similar to the macrolide class of antibiotics.

Stimulus-Responsive, Biodegradable, Biocompatible, Covalently Cross-Linked Hydrogel Based on Dextrin and Poly(N-isopropylacrylamide) for in Vitro/in Vivo Controlled Drug Release

A novel stimulus-sensitive covalently cross-linked hydrogel derived from dextrin, N-isopropylacrylamide, and N,N'-methylene bis(acrylamide) (c-Dxt/pNIPAm), has been synthesized via Michael type addition reaction for controlled drug release application. The chemical structure of c-Dxt/pNIPAm has been confirmed through Fourier transform infrared (FTIR) spectroscopy and (1)H and (13)C NMR spectral analyses. The surface morphology of the hydrogel has been studied by field emission scanning electron microscopic (FE-SEM) and environmental scanning electron microscopic (E-SEM) analyses. The stimulus responsiveness of the hydrogel was studied through equilibrium swelling in various pH media at 25 and 37 °C. Rheological study was performed to measure the gel strength and gelation time. Noncytotoxicity of c-Dxt/pNIPAm hydrogel has been studied using human mesenchymal stem cells (hMSCs). The biodegradability of c-Dxt/pNIPAm was confirmed using hen egg lysozyme. The in vitro and in vivo release studies of ornidazole and ciprofloxacin imply that c-Dxt/pNIPAm delivers both drugs in a controlled way and would be an excellent alternative for a dual drug carrier. The FTIR, powder X-ray diffraction (XRD), and UV-vis-near infrared (NIR) spectra along with the computational study predict that the drugs remain in the matrix through physical interaction. A stability study signifies that the drugs (ornidazole ∼97% and ciprofloxacin ∼98%) are stable in the tablet formulations for up to 3 months.

Genetic Basis and Functional Consequences of Differential Expression of the CmeABC Efflux Pump in Campylobacter jejuni Isolates

The CmeABC multidrug efflux transporter of Campylobacter jejuni plays a key role in antimicrobial resistance and is suppressed by CmeR, a transcriptional regulator of the TetR family. Overexpression of CmeABC has been observed in laboratory-generated mutants, but it is unknown if this phenotype occurs naturally in C. jejuni isolates and if it has any functional consequences. To answer these questions, expression of cmeABC in natural isolates obtained from broiler chickens, turkeys and humans was examined, and the genetic mechanisms and role of cmeABC differential expression in antimicrobial resistance was determined. Among the 64 C. jejuni isolates examined in this study, 43 and 21 were phenotypically identified as overexpression (OEL) and wild-type expression (WEL) levels. Representative mutations of the cmeABC promoter and/or CmeR-coding sequence were analyzed using electrophoretic mobility shift assays and transcriptional fusion assays. Reduced CmeR binding to the mutated cmeABC promoter sequences or decreased CmeR levels increased cmeABC expression. Several examined amino acid substitutions in CmeR did not affect its binding to the cmeABC promoter, but a mutation that led to C-terminal truncation of CmeR abolished its DNA-binding activity. Interestingly, some OEL isolates harbored no mutations in known regulatory elements, suggesting that cmeABC is also regulated by unidentified mechanisms. Overexpression of cmeABC did not affect the susceptibility of C. jejuni to most tested antimicrobials except for chloramphenicol, but promoted the emergence of ciprofloxacin-resistant mutants under antibiotic selection. These results link CmeABC overexpression in natural C. jejuni isolates to various mutations and indicate that this phenotypic change promotes the emergence of antibiotic-resistant mutants under selection pressure. Thus, differential expression of CmeABC may facilitate Campylobacter adaptation to antibiotic treatments.

Photochemical behavior of antibiotics impacted by complexation effects of concomitant metals: a case for ciprofloxacin and Cu(II)

Many water bodies, especially those adjacent to aquaculture and livestock breeding areas, are contaminated by both antibiotics and transition metals. However, the effects of the interaction between antibiotics and transition metals on the environmental behavior and the ecotoxicology of antibiotics are largely unknown. We hypothesized that antibiotics may coordinately bind with metal ions, and this complexation may affect the environmental photochemical behavior of antibiotics. We took ciprofloxacin (CIP) and Cu(ii) as a case, and employed simulated sunlight experiments and density functional theory calculations to investigate the underlying reaction mechanisms. The results showed that monovalent cationic ciprofloxacin (H2CIP(+)) that is predominant in the normal pH range (6-9) of surface waters can chelate with hydrated Cu(ii) to form [Cu(H2CIP)(H2O)4](3+). Compared with H2CIP(+), [Cu(H2CIP)(H2O)4](3+) has different molecular orbitals, and atomic charge distribution. As a result, [Cu(H2CIP)(H2O)4](3+) showed dissimilar light absorption properties, slower direct photolytic rates, lower (1)O2 generation ability and weaker reactivity towards (1)O2. Due to the Cu(ii) complexation, the apparent photodegradation of H2CIP(+) was inhibited, and the photolytic pathways and product distribution were altered. This study implies that for an accurate ecological risk assessment of antibiotics under transition metal co-contamination conditions, the effects of metal complexation should be considered.

Parameters influencing ciprofloxacin, ofloxacin, amoxicillin and sulfamethoxazole retention by natural and converted calcium phosphates

The retention of four antibiotics, ciprofloxacin, ofloxacin, amoxicillin and sulfamethoxazole by a natural phosphate rock (francolite) was studied and compared with a converted hydroxyapatite powder. The maximum sorption capacities were found to correlate with the molecular weight of the molecules. The mechanisms of sorption depended mostly on the charge of the antibiotic whereas the kinetics of the process was sensitive to their hydrophobic/hydrophilic character. The two materials showed slightly distinct affinities for the various antibiotics but exhibited similar maximum sorption capacities despite different specific surface areas. This was mainly attributed to the more pronounced hydrophobic character of the francolite phase constituting the natural phosphate. These data enlighten that the retention properties of these mineral phases depend on a complex interplay between the inter-molecular and molecule-solid interactions. These findings are relevant to understand better the contribution of calcium phosphates in the fate and retention of antibiotics in soils.

Ciprofloxacin adsorption on graphene and granular activated carbon: kinetics, isotherms, and effects of solution chemistry

Ciprofloxacin (CIP) is a commonly used antibiotic and widely detected in wastewaters and farmlands nowadays. This study evaluated the efficacy of next-generation adsorbent (graphene) and conventional adsorbent (granular activated carbon, GAC) for CIP removal. Batch experiments and characterization tests were conducted to investigate the adsorption kinetics, equilibrium isotherms, thermodynamic properties, and the influences of solution chemistry (pH, ionic strength, natural organic matter (NOM), and water sources). Compared to GAC, graphene showed significantly faster adsorption and reached equilibrium within 3 min, confirming the rapid access of CIP into the macroporous network of high surface area of graphene as revealed by the Brunner-Emmet-Teller measurements analysis. The kinetics was better described by a pseudo-second-order model, suggesting the importance of the initial CIP concentration related to surface site availability of graphene. The adsorption isotherm on graphene followed Langmuir model with a maximum adsorption capacity of 323 mg/g, which was higher than other reported carbonaceous adsorbents. The CIP adsorption was thermodynamically favourable on graphene and primarily occurred through π - π interaction, according to the FTIR spectroscopy. While the adsorption capacity of graphene decreased with increasing solution pH due to the speciation change of CIP, the adverse effects of ionic strength (0.01-0.5 mol L(-1)), presence of NOM (5 mg L⁻¹), and different water sources (river water or drinking water) were less significant on graphene than GAC. These results indicated that graphene can serve as an alternative adsorbent for CIP removal in commonly encountered field conditions, if proper separation and recovery is available in place.

[Radiolytic Decomposition of Ciprofloxacin Hydrochloride in Aqueous Solution Using γ Irradiation]

Effects of initial concentrations, pH values, different additives and composite pollutants on ciprofloxacin hydrochloride removal using γ irradiation were investigated. The experiments results showed γ irradiation could effectively remove ciprofloxacin hydrochloride; low initial concentration and strongly acidic condition were favorable for CIP removal using γ irradiation; the degradation of CIP was inhibited upon the addition of CO3(2-) and methanol, which indicated that the degradation of CIP might be mainly ascribed to *OH oxidation and the direct decomposition of CIP molecules induced by irradiation. BrO3- showed a synergistic effect with CIP in degradation of the composite pollutants when mixed together with CIP for γ irradiation, and the removal rates of both pollutants were improved. At an absorbed dose of 400 Gy, the removal rates of CIP and BrO3- were increased by 18.74% and 1.81%, respectively. The removal rates of TOC and COD were 15.22% and 61.44%, respectively, when the 100 mg x L(-1) CIP was degraded by γ irradiation at the absorbed dose of 6 000 Gy.

Comparison of bond strength of self-etch adhesive to pulp chamber dentin after placement of calcium hydroxide and various antibiotic pastes

OBJECTIVE

The aim of this study was to evaluate the effect of calcium hydroxide, double antibiotic paste (DAP) and triple antibiotic paste (TAP) with minocycline, cefaclor and amoxicillin on the micro tensile bond strength (µTBS) of self-etch adhesive to pulp chamber dentin.

MATERIALS AND METHODS

Sixty mandibular first molars were cut horizontally and randomly divided into a control group and five experimental groups, which received an intra-canal dressing, as follows: calcium hydroxide, DAP, TAP with minocycline, TAP with cefaclor and TAP with amoxicillin. After storing the specimens for 4 weeks, the medicaments were removed by irrigation with 10 mL each of the following solution: 2.5% NaOCl, 17% EDTA and distilled water. A self-etch adhesive (Clearfil S3 Bond, Okayama, Japan) was applied and composite resin (Clearfil Majesty Posterior, Kuraray Medical Inc., Japan) was placed into the cavity. A µTBS test was performed on each specimen using a universal test machine.

RESULTS

The DAP reduced the µTBS of self-etch adhesive compared to the control group, calcium hydroxide and TAP with minocycline and with cefaclor (p < 0.05). However, the other medicaments did not result in a decreased µTBS of self-etch adhesive to pulp chamber dentin as compared to the control group (p > 0.05).

CONCLUSIONS

The use of DAP resulted in a reduced µTBS of self-etch adhesive to pulp chamber dentin.

Dextrin and poly(acrylic acid)-based biodegradable, non-cytotoxic, chemically cross-linked hydrogel for sustained release of ornidazole and ciprofloxacin

Herein, novel biodegradable, stimulus-responsive, chemically cross-linked and porous hydrogel has been synthesized to evaluate its applicability as an efficient carrier for sustained release of ornidazole and ciprofloxacin. The cross-linked hydrogel (c-Dxt/pAA) has been developed from dextrin and poly(acrylic acid) using N,N'-methylene bis(acrylamide) cross-linker via Michael-type addition reaction. With the variation of reaction parameters, various c-Dxt/pAA hydrogels have been synthesized to optimize the best one. c-Dxt/pAA hydrogel has been characterized using various physicochemical characterization techniques. The hydrogel demonstrates significant pH and temperature sensitivity. Gel characteristics and gel kinetics have been performed through the measurement of rheological parameters. The hydrogel shows noncytotoxic behavior toward human mesenchymal stem cells. Biodegradation study predicts that c-Dxt/pAA is degradable in nature. The in vitro release of ornidazole and ciprofloxacin suggests that the hydrogel released both the drugs in a controlled manner with extensive stability up to 3 months. The results suggest that c-Dxt/pAA is probably a promising candidate for controlled release of ornidazole and ciprofloxacin.

Enhanced adsorptive removal of selected pharmaceutical antibiotics from aqueous solution by activated graphene

Activated graphene adsorbents (G-KOH) were synthesized by a one-step alkali-activated method, with a high specific surface area (SSA) and a large number of micropores. As a result, the SSA of the final product greatly increases to ∼512.6 m(2)/g from ∼138.20 m(2)/g. The resulting G-KOH was used firstly as an adsorbent for the removal of ciprofloxacin (CIP) in aqueous solutions. Experimental results indicated that G-KOH has excellent adsorption capacity (∼194.6 mg/g). The alkali-activation treatment introduced oxygen-containing functional groups on the surface of G-KOH, which would be beneficial to improving the adsorption affinity of G-KOH for the removal of CIP. Kinetic regression results showed that the adsorption kinetic was more accurately represented by a pseudo-second-order model. The overall adsorption process was jointly controlled by external mass transfer and intra-particle diffusion, and intra-particle diffusion played a dominant role. A Langmuir isotherm model showed a better fit with adsorption data than a Freundlich isotherm model for the adsorption of CIP on G-KOH. The remarkable adsorption capacity of CIP onto G-KOH can be attributed to the multiple adsorption interaction mechanisms (hydrogen bonding, π-π electron donor-acceptor interactions, and electrostatic interactions). Results of this work are of great significance for environmental applications of activated graphene with higher SSA as a promising adsorbent for organic pollutants from aqueous solutions.

[Adsorption characteristics of typical PPCPs onto river sediments and its influencing factors]

A batch equilibrium method was used to investigate the adsorption characteristics of ciprofloxacin (CIP), tetracycline (TC), sulfamethoxazole (SMX) and triclosan (TCS) onto Huangpu River sediments. Effects of adsorption time, initial concentration, solution pH and temperature on the adsorption process were studied. The results showed that the adsorption process of these PPCPs onto sediments was a two-step process: a rapid adsorption followed by a slow balance. The equilibrium time was about 4 h. The pH value had a significant effect on the adsorption of CIP, TC and TCS, whereas the effect on SMX adsorption was negligible. The kinetic results indicated that the adsorption processes followed the pseudo-second-order model, with adsorption rate in the range of 4.89 x 10(-3)-1.96 x 10(-2) kg x (min x mg)(-1). Adsorption isotherms were well described by the Freundlich and linear equations. As temperature increased, the amount of SMX and TC adsorbed increased, whereas CIP and TCS decreased. CIP, TC and TCS had a strong tendency to adsorb onto sediments, while the adsorption of SMX was unfavorable. When the initial concentration of PPCPs was 10 mg x L(-1), the equilibrium adsorption capacities of CIP, TC, SMX and TCS reached 702.8, 733.1, 54.7 and 695.0 mg x kg(-1), respectively.

Montmorillonite enhanced ciprofloxacin transport in saturated porous media with sorbed ciprofloxacin showing antibiotic activity

Antibiotic ciprofloxacin (CIP) is immobile in the subsurface but it has been frequently detected in the aquatic system. Therefore it is important to investigate the factors impacting CIP's mobilization in aquifer. Laboratory columns packed with sand were used to test colloid-facilitated CIP transport by 1) using kaolinite or montmorillonite to mobilize presorbed-CIP in a column or 2) co-transporting with CIP by pre-mixing them before transport. The Langmuir model showed that CIP sorption by montmorillonite (23gkg(-1)) was 100 times more effective than sand or kaolinite. Even with strong CIP complexation ability to Fe/Al coating on sand surface, montmorillonite promoted CIP transport, but not kaolinite. All presorbed-CIP by sand was mobilized by montmorillonite after 3 pore volumes through co-transporting of CIP with montmorillonite. The majority of CIP was fixed onto the montmorillonite interlayer but still showed inhibition of bacteria growth. Our results suggested that montmorillonite with high CIP sorption ability can act as a carrier to enhance CIP's mobility in aquifer.