A novel antibiotic wastewater degradation technique combining cavitating jets impingement with multiple synergetic methods

Antibiotics degradation remains a longstanding challenge in wastewater treatment. Towards this objective, we have developed a novel technique combining cavitating jets impingement with multiple synergetic methods, i.e., UV/Fenton, analogous Fenton, and photocatalytic oxidation in the present work. Three kinds of antibiotics namely amoxicillin, doxycycline and sulfadiazine sodium, are selected as model pollutants. Individual application of cavitating jets impingement is firstly conducted to evaluate the effects of jets impinging forms and nozzle inlet pressure. The effects of impingement on promoting antibiotics degradation and weakening the coalescing effects of cavitation bubbles are confirmed. Perpendicular double cavitating jets impingement is proved to be the most effective impinging form and brought a COD (chemical oxidation demand) reduction of 30.04% with the impinging effect index 1.22 at jet inlet pressure 10 MPa. Increasing the jet inlet pressure can improve the COD reduction and the effectiveness of impingement. Subsequently, UV/Fenton process is introduced to intensify the degradation process. The effects of important parameters are investigated by means of orthogonal experiments and the maximum COD reduction is up to 71.16% under the optimum conditions. Then, analogous Fenton process and photocatalytic oxidation are adopted for further enhancing the COD reduction. Different approaches used in the present work are assessed in view of multiple aspects. With COD reduction of 79.92%, the combination of cavitating jets impingement, UV/Fenton, analogous Fenton and photocatalytic oxidation is proved to be optimum method for antibiotic wastewater treatment.

Magnetically-responsive, multifunctional drug delivery nanoparticles for elastic matrix regenerative repair

Arresting or regressing growth of abdominal aortic aneurysms (AAAs), localized expansions of the abdominal aorta are contingent on inhibiting chronically overexpressed matrix metalloproteases (MMPs)-2 and -9 that disrupt elastic matrix within the aortic wall, concurrent with providing a stimulus to augmenting inherently poor auto-regeneration of these matrix structures. In a recent study we demonstrated that localized, controlled and sustained delivery of doxycycline (DOX; a tetracycline-based antibiotic) from poly(lactic-co-glycolic acid) nanoparticles (PLGA NPs), enhances elastic matrix deposition and MMP-inhibition at a fraction of the therapeutically effective oral dose. The surface functionalization of these NPs with cationic amphiphiles, which enhances their arterial uptake, was also shown to have pro-matrix regenerative and anti-MMP effects independent of the DOX. Based on the hypothesis that the incorporation of superparamagnetic iron oxide NPs (SPIONs) within these PLGA NPs would enhance their targetability to the AAA site under an applied external magnetic field, we sought to evaluate the functional effects of NPs co-encapsulating DOX and SPIONs (DOX-SPION NPs) on elastic matrix regeneration and MMP synthesis/activity in vitro within aneurysmal smooth muscle cell (EaRASMC) cultures. The DOX-SPION NPs were mobile under an applied external magnetic field, while enhancing elastic matrix deposition 1.5-2-fold and significantly inhibiting MMP-2 synthesis and MMP-2 and -9 activities, compared to NP-untreated control cultures. These results illustrate that the multifunctional benefits of NPs are maintained following SPION co-incorporation. Additionally, preliminary studies carried out demonstrated enhanced targetability of SPION-loaded NPs within proteolytically-disrupted porcine carotid arteries ex vivo, under the influence of an applied external magnetic field. Thus, this dual-agent loaded NP system proffers a potential non-surgical option for treating small growing AAAs, via controlled and sustained drug release from multifunctional, targetable nanocarriers.

STATEMENT OF SIGNIFICANCE

Proactive screening of high risk elderly patients now enables early detection of abdominal aortic aneurysms (AAAs). There are no established drug-based therapeutic alternatives to surgery for AAAs, which is unsuitable for many elderly patients, and none which can achieve restore disrupted and lost elastic matrix in the AAA wall, which is essential to achieve growth arrest or regression. We have developed a first generation design of polymer nanoparticles (NPs) for AAA tissue localized delivery of doxycycline, a modified tetracycline drug at low micromolar doses at which it provides both pro-elastogenic and anti-proteolytic benefits that can augment elastic matrix regenerative repair. The nanocarriers themselves are also uniquely chemically functionalized on their surface to also provide them pro-elastin-regenerative & anti-matrix degradative properties. To provide an active driving force for efficient uptake of intra-lumenally infused NPs to the AAA wall, in this work, we have rendered our polymer NPs mobile in an applied magnetic field via co-incorporation of super-paramagnetic iron oxide NPs. We demonstrate that such modifications significantly improve wall uptake of the NPs with no significant changes to their physical properties and regenerative benefits. Such NPs can potentially stimulate structural repair in the AAA wall following one time infusion to delay or prevent AAA growth to rupture. The therapy can provide a non-surgical treatment option for high risk AAA patients.

A novel flow injection spectrophotometric method using plant extracts as green reagent for the determination of doxycycline

A novel flow injection spectrophotometric method was developed for the determination of doxycycline in pharmaceutical preparations using iron(III) contained in extracts from plants. The assay was based on the complex formed between doxycycline and iron(III) characterized by an absorption maximum at 435nm. The calibration graphs obtained over the doxycycline concentration range 5-250μgmL^-1 gave correlation coefficients of 0.9979, 0.9987 and 0.9987 with the three green reagents prepared from Senna alata (L.) Roxb. (S. alata), Polygonum hydropiper L. (P. hydropiper) or Diplazium esculentum (Retz.) Sw. (D. esculentum), respectively. The relative standard deviations of the repeatability was <2.00%. The percentage recoveries were in the range of 98.27-101.03%. Doxycycline contents obtained by this new method and by the reference methods reported in literature were in agreement at 95% confidence level with the paired t-test. The sample throughput was 36h^-1 for each green reagent.

Nanoparticulate delivery of agents for induced elastogenesis in three-dimensional collagenous matrices

The degradation of elastic matrix in the infrarenal aortic wall is a critical parameter underlying the formation and progression of abdominal aortic aneurysms. It is mediated by the chronic overexpression of matrix metalloprotease (MMP)-2 and MMP-9, leading to a progressive loss of elasticity and weakening of the aortic wall. Delivery of therapeutic agents to inhibit MMPs, while concurrently coaxing cell-based regenerative repair of the elastic matrix represents a potential strategy for slowing or arresting abdominal aortic aneurysm growth. Previous studies have demonstrated elastogenic induction of healthy and aneurysmal aortic smooth muscle cells and inhibition of MMPs, following exogenous delivery of elastogenic factors such as transforming growth factor (TGF)-β1, as well as MMP-inhibitors such as doxycycline (DOX) in two-dimensional culture. Based on these findings, and others that demonstrated elastogenic benefits of nanoparticulate delivery of these agents in two-dimensional culture, poly(lactide-co-glycolide) nanoparticles were developed for localized, controlled and sustained delivery of DOX and TGF-β1 to human aortic smooth muscle cells within a three-dimensional gels of type I collagen, which closely simulate the arterial tissue microenvironment. DOX and TGF-β1 released from these nanoparticles influenced elastogenic outcomes positively within the collagen constructs over 21 days of culture, which were comparable to that induced by exogenous supplementation of DOX and TGF-β1 within the culture medium. However, this was accomplished at doses ~20-fold lower than the exogenous dosages of the agents, illustrating that their localized, controlled and sustained delivery from nanoparticles embedded within a three-dimensional scaffold is an efficient strategy for directed elastogenesis. Copyright © 2014 John Wiley & Sons, Ltd.

Effect of iron ion on doxycycline photocatalytic and Fenton-based autocatatalytic decomposition

Doxycycline plays a key role in Fe(III)-to-Fe(II) redox cycling and therefore in controlling the overall reaction rate of the Fenton-based process (H2O2/Fe(III)). This highlights the autocatalytic profile of doxycycline degradation. Ferric iron reduction in the presence of doxycycline relied on doxycycline-to-Fe(III) complex formation with an ensuing reductive release of Fe(II). The lower ratio of OH-to-contaminant in an initial H2O2/Fe(III) oxidation step than in that of classical Fenton (H2O2/Fe(II)) decreased the doxycycline degradation rate. The quantum yield of doxycycline in direct UV-C photolysis was 3.1 × 10(-3) M E(-1). In spite of doxycycline-Fe(III) complexes could produce the adverse effect on the doxycycline degradation in the UV/Fe(III) system some acceleration of the rate was observed upon irradiation of the Fe(III)-hydroxy complex. Acidic reaction media (pH 3.0) and the molar ratio of DC/Fe(III) = 2/1 favored the complex formation. Doxycycline close degradation rates and complete mineralization achieved for 120 min (Table 1) with both UV/H2O2 and UV/H2O2/Fe(III) indicated the unsubstantial role of the reduction of Fe(III) to Fe(II) in UV/H2O2/Fe(III) system efficacy. Thus, factors such as doxycycline's ability to form complexes with ferric iron and the ability of complexes to participate in a reductive pathway should be considered at a technological level in process optimization, with chemistry based on iron ion catalysis to enhance the doxycycline oxidative pathway.

Doxycycline Degradation by the Oxidative Fenton Process

Doxycycline is a broad-spectrum tetracycline occurring in domestic, industrial, and rural effluents, whose main drawback is the increasing emergence of resistant bacteria. This antibiotic could be degraded by the so-called Fenton process, consisting in the oxidation of organic pollutants by oxygen peroxide (H2O2) in the presence of Fe2+. Experiments were performed according to an experimental Rotational Central Composite Design to investigate the influence of temperature (0–40.0°C), H2O2concentration (100–900 mg/L), and Fe2+concentration (5–120 mg/L) on residual doxycycline and total organic carbon concentrations. Whereas the final residual doxycycline concentration ranged from 0 to 55.8 mg/L, the oxidation process proved unable to reduce the total organic carbon by more than 30%. The best operating conditions were concentrations of H2O2and Fe2+of 611 and 25 mg/L, respectively, and temperature of 35.0°C, but the analysis of variance revealed that only the first variable exerted a statistically significant effect on the residual doxycycline concentration. These results suggest possible application of this process in the treatment of doxycycline-containing effluents and may be used as starting basis to treat tetracycline-contaminated effluents.

Tetracycline: production, waste treatment and environmental impact assessment

The frequent occurrence of pharmaceuticals in the aquatic environment requires an assessment of their environmental impact and their negative effects in humans. Among the drugs with high harmful potential to the environment are the antibiotics that reach the environment not only, as may be expected, through the effluents from chemical and pharmaceutical industries, but mainly through the sewage and livestock; because around 25 to 75% of the ingested drugs are excreted in unchanged form after the passage through the Gastro-Intestinal Tract. Tetracycline has high world consumption, representing a human consumption of about 23 kg/day in Brazil in 2007. At the moment, researches are being made to develop new tetracycline that incorporate heavy metals (Hg, Cd, Re, Pt, Pd) to their structures in order to increase their bactericidal effect. The conventional wastewater treatment plants are not able to degrade complex organic molecules to reduce their toxicity and improve their biodegradability. For this reason new technologies, i.e., the advanced oxidation processes, are being developed to handle this demand. The objectives of this study are to review the literature on the processes of obtaining tetracycline, presenting its waste treatment methods and evaluation of their environmental impact.

Bioactive implant surface with electrochemically bound doxycycline promotes bone formation markers in vitro and in vivo

OBJECTIVES

The objective of this study was to demonstrate a successful binding of Doxy hyclate onto a titanium zirconium alloy surface.

METHODS

The coating was done on titanium zirconium coins in a cathodic polarization setup. The surface binding was analyzed by SEM, SIMS, UV-vis, FTIR and XPS. The in vitro biological response was tested with MC3T3-E1 murine pre-osteoblast cells after 14 days of cultivation and analyzed in RT-PCR. A rabbit tibial model was also used to confirm its bioactivity in vivo after 4 and 8 weeks healing by means of microCT.

RESULTS

A mean of 141 μg/cm(2) of Doxy was found firmly attached and undamaged on the coin. Inclusion of Doxy was documented up to a depth of approximately 0.44 μm by tracing the (12)C carbon isotope. The bioactivity of the coating was documented by an in vitro study with murine osteoblasts, which showed significantly increased alkaline phosphatase and osteocalcin gene expression levels after 14 days of cell culture along with low cytotoxicity. Doxy coated surfaces showed increased bone formation markers at 8 weeks of healing in a rabbit tibial model.

SIGNIFICANCE

The present work demonstrates a method of binding the broad spectrum antibiotic doxycycline (Doxy) to an implant surface to improve bone formation and reduce the risk of infection around the implant. We have demonstrated that TiZr implants with electrochemically bound Doxy promote bone formation markers in vitro and in vivo.

Relevance of microstructure for the early antibiotic release of fresh and pre-set calcium phosphate cements

Calcium phosphate cements (CPCs) have great potential as carriers for controlled release and vectoring of drugs in the skeletal system. However, a lot of work still has to be done in order to obtain reproducible and predictable release kinetics. A particular aspect that adds complexity to these materials is that they cannot be considered as stable matrices, since their microstructure evolves during the setting reaction. The aims of the present work were to analyze the effect of the microstructural evolution of the CPC during the setting reaction on the release kinetics of the antibiotic doxycycline hyclate and to assess the effect of the antibiotic on the microstructural development of the CPC. The incorporation of the drug in the CPC modified the textural and microstructural properties of the cements by acting as a nucleating agent for the heterogeneous precipitation of hydroxyapatite crystals, but did not affect its antibacterial activity. In vitro release experiments were carried out on readily prepared cements (fresh CPCs), and compared to those of pre-set CPCs. No burst release was found in any formulation. A marked difference in release kinetics was found at the initial stages; the evolving microstructure of fresh CPCs led to a two-step release. Initially, when the carrier was merely a suspension of α-TCP particles in water, a faster release was recorded, which rapidly evolved to a zero-order release. In contrast, pre-set CPCs released doxycycline following non-Fickian diffusion. The final release percentage was related to the total porosity and entrance pore size of each biomaterial.

Multifunctional nanoparticles for doxycycline delivery towards localized elastic matrix stabilization and regenerative repair

Abdominal aortic aneurysms (AAAs) are abnormal expansions of the aortic wall, typically characterized by chronic up-regulation of matrix metalloproteases (MMPs)-2 and -9. These MMPs degrade elastin and elastic matrix within the aortic wall, leading to a progressive loss of elasticity of the abdominal aorta as the condition progresses. Doxycycline (DOX) is a tetracycline-based antibiotic which has shown significant promise in delaying and slowing the growth of AAAs in both clinical studies and animal models. However, it has been found to inhibit elastic matrix deposition by vascular cells at dosages in the μg ml(-1) range, which is typically observed in the circulation, in addition to systemic side effects, following oral dosage. In this paper, we describe the development of DOX-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles for localized, controlled and sustained DOX delivery towards AAA therapy. Further, we demonstrate that surface functionalization of these nanoparticles with cationic amphiphiles not only imparts them with a positive charge for potentially enhanced aortic uptake, but also enables enhanced elastin binding via hydrophobic interactions, as well as up-regulating activity of the elastin crosslinking enzyme lysyl oxidase. In addition to the DOX released from the nanoparticles being effective in inhibiting MMP-2 production and activity, we also demonstrate that surface functionalization of the nanoparticles cationic amphiphiles may also play a role in MMP-2 inhibition via (i) electrostatic interactions with negatively charged residues in the active-site of MMP-2 or (ii) steric blockade of the active site on account of the presence of two dodecyl chains in the DMAB molecule. Thus, in addition to enhanced aortic uptake and retention illustrated in studies by other groups, we have demonstrated that cationic functionalization of PLGA nanoparticles enhances elastogenic outcomes by targeted binding to elastin, as well as their potential to inhibit elastolysis. These results establish their multifunctionality as a localized delivery system for AAA therapy. Overall, this delivery system has the potential to enhance regenerative outcomes at sites of proteolytic matrix disruption/degradation by enabling targeted, controlled and long-term release of therapeutic agents.

Sensitive and selective spectrophotometric assay of doxycycline hyclate in pharmaceuticals using Folin-Ciocalteu reagent

A spectrophotometric method for the determination of doxycycline (DOX) is described. The method is based on the formation of blue colored chromogen due to reduction of tungstate and/or molybdate in Folin-Ciocalteu (F-C) reagent by DOX in alkaline medium. The colored species has an absorption maximum at 770 nm and the system obeys Beer's law over the concentration range 0.75-12.0 μg mL-1 DOX. The apparent molar absorptivity is 2.78 × 104 L mol-1 cm-1. The limit of quantification and detection values are reported to be 0.20 and 0.08 μg mL-1, respectively. Over the linear range applicable, the accuracy and precision of the method were evaluated on intra-day and inter-day basis. The reported mean accuracy value was 101.0 ± 1.7 %, the relative error was ≤ 2.7 % and the relative standard deviation was ≤ 2.5 %. Application of the proposed method to bulk powder and commercial pharmaceutical tablets is also presented. No significant difference was obtained between the results of the proposed method and the official BP method. The procedure described in this paper is simple, rapid, accurate and precise.