Fleroxacin uptake in ischaemic limb tissue

Antibiotic application to patients with ischaemia of lower limbs may be indicated to avoid or treat infection of soft tissues. Fleroxacin, a fluoroquinolone, active against various Gram-negative and Gram-positive organisms may be used for this purpose. We evaluated the diffusion of fleroxacin into bone, subcutaneous fat, muscle and tendon tissues of lower limb tissue after a 400 mg i.v. dose. Concentrations in ischaemic tissues were similar to those found in non-ischaemic sites. Since the maximum antibiotic levels found were lower than the MICs of various pathogens relevant for infection, we suggest to increase the dose used for this peri-operative prophylaxis to 800 mg.     

Efficient approach to acyloxymethyl esters of nalidixic acid and in vitro evaluation as intra-ocular prodrugs

Various alkylcarbonyloxymethyl esters of nalidixic acid ranging from 3 to 15 carbon units in the pro-moiety have been prepared and assessed as potential prodrugs. Their chromatographic retention factors k', silicone oil solubilities and in vitro conversion to nalidixic acid by a commercial esterase were determined together with their in vitro antimicrobial activity and cytotoxicity. The preliminary results suggest that silicone oil may have potential for the intra-ocular delivery of antibacterial compounds. Moreover, the in vitro release rate can be controlled by the lipophilicity of the prodrug.     

Synthesis and antibacterial properties of beta-diketone acrylate bioisosteres of pseudomonic acid A.

A series of beta-diketone acrylate bioisosteres 4 of pseudomonic acid A 1 have been synthesized and evaluated for their ability to inhibit bacterial isoleucyl-tRNA synthetase and act as antibacterial agents. A number of analogues have excellent antibacterial activity. Selected examples were shown to afford good blood levels and to be effective in a murine infection model.     

Human mesenchymal stromal cells can uptake and release ciprofloxacin,acquiring in vitro anti-bacterial activity

Background aimsTraditional antibiotic therapy is based on the oral or systemic injection of antibiotics that are often unable to stop a deep infection (eg, osteomyelitis). We studied whether or not bone marrow stromal cells (BM-MSCs) are able to uptake and release ciprofloxacin (CPX), a fluoroquinolone considered the drug of choice for the treatment of chronic osteomyelitis because of its favorable penetration into poorly vascularized sites of infection.MethodsHuman bone marrow stromal cells (BM-MSCs) were primed with CPX (BM-MSCsCPX) according to a methodology previously standardized in our laboratory for paclitaxel (PTX). The anti-microbial activity of CPX released from BM-MSCs cells (BM-MSCsCPX-CM) or supernatant from cell lysate (BM-MSCsCPX-LYS) was evaluated by agar dilution and microdilution methods on three bacterial strains (Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa). To investigate whether or not primed cells (BM-MSCsCPX) were able to directly act on the bacterial growth, co-colture was performed by mixing E. coli suspension to an increasing number of BM-MSCsCPX. The anti-bacterial activity was determined as number of BM-MSCsCPX that completely inhibited bacterial growth.ResultsThe results demonstrated that BM-MSCsCPX are able to uptake and then release CPX in the conditioned medium. The loaded antibiotic maintains its active form throughout the process as tested on bacteria.ConclusionsOur findings suggest that CPX-loaded MSCs may represent an important device for carrying and delivering CPX (and perhaps other antibiotics) into infected deep microenvironments; they could be used for local application and by systemic infusion when their homing capacity into the bone is cleared.     

Modulation of receptor-mediated signal transduction by diacylglycerol mimetics in astrocytes

1. When rat astrocytes in primary culture were incubated with bradykinin, inositol phosphate formation and arachidonic acid release were stimulated. 2. By themselves, phorbol esters inhibited inositol phosphate formation, but phorbol esters and other cell-permeant diacylglycerol analogues stimulated arachidonic acid release. Preincubation of the cells with phorbol esters or diacylglycerol analogues blocked bradykinin-stimulated inositol phosphate formation but augmented bradykinin-stimulated arachidonic acid release. 3. The present results suggest that, in astrocytes, bradykinin activates at least two signal transduction pathways bradykinin stimulates a phosphatidylinositol-specific phospholipase C leading to enhanced inositol phosphate formation, and bradykinin stimulates a second phospholipase to enhance arachidonic acid release. The pathways may be distinguished using phorbol esters and other diacylglycerol mimetics. 4. The possibility is raised that diacylglycerol, formed in response to bradykinin, may serve as a transducer of receptor-receptor interactions by altering the ability of receptors to stimulate phospholipase activity.     

Electrogeneration of polymer films functionalized by fluoroquinolone models for the development of antibiotic immunosensor

Fluoroquinolones are antibacterial agents, effective against Gram positive and Gram negative bacteria. With the aim of detecting fluoroquinolones rapidly and easily, fluoroquinolone models of ciprofloxacin functionalized by pyrrole or amino groups were synthesized. The electrochemical behavior of the pyrrole derivatives and their electropolymerization properties were investigated in organic media. In parallel, the amino derivative was chemically grafted onto an electropolymerized polypyrrole film. The resulting polymer has been incubated with anticiprofloxacin antibody, leading to the antibody immobilization by an immunoreaction with the ciprofloxacin model. The impedance behavior of the modified electrode was then examined towards the effect of ciprofloxacin.     

Liquid chromatographic separation of the enantiomers of fluoroquinolone antibacterials on a chiral stationary phase based on a chiral crown ether

A chiral stationary phase (CSP) recently developed by bonding (diphenyl-substituted 1,1'-binaphthyl) crown ether to silica gel for the liquid chromatographic separation of enantiomers was applied to the resolution of investigational fluoroquinolone antibacterial agents including gemifloxacin (formerly LB20304a). All fluoroquinolone compounds used in this study were resolved quite well on the CSP. Especially, the resolution of gemifloxacin and its analogs on the CSP was excellent and even greater than that on the commercial Crownpak CR(+). The resolution was found to be dependent on the type and the content of organic, acidic, and inorganic modifiers added to the mobile phase and on the column temperature.     

Formation of conjugates from ciprofloxacin and norfloxacin in cultures of Trichoderma viride

The formation of conjugates from two antibacterial fluoroquinolone drugs, ciprofloxacin and norfloxacin, was observed in cultures of Trichoderma viride that had been grown in sucrose-peptone broth and extracted 16 d after dosing with the drugs. Both conjugates were purified by high-performance liquid chromatography and found to be optically active. They were identified by mass and proton nuclear magnetic resonance spectra as 4-hydroxy-3-oxo-4-vinylcyclopent-1-enyl ciprofloxacin and 4-hydroxy-3-oxo-4-vinylcyclopent-1-enyl norfloxacin. The transformation of veterinary fluoroquinolones in the presence of fungi may have ecological significance.     

Bi-Functionalization of a Calcium Phosphate-Coated Titanium Surface with Slow-Release Simvastatin and Metronidazole to Provide Antibacterial Activities and Pro-Osteodifferentiation Capabilities

Coating the surface of titanium implants or other bone graft substitute materials with calcium phosphate (Ca-P) crystals is an effective way to enhance the osteoconduction of the implants. Ca-P coating alone cannot confer pro-osteodifferentiation and antibacterial capabilities on implants; however, it can serve as a carrier for biological agents which could improve the performance of implants and bone substitutes. Here, we constructed a novel, bi-functional Ca-P coating with combined pro-osteodifferentiation and antibacterial capabilities. Different concentrations of metronidazole (MNZ) and simvastatin (SIM) were integrated into biomimetic Ca-P coatings on the surface of titanium disks. The biological effects of this bi-functional biomimetic coating on human bone marrow mesenchymal stem cells (hBMMSCs), human adipose derived stromal cells (hASCs), and Porphyromonas gingivalis were assessed in vitro. We observed that Ca-P coatings loaded with both SIM and MNZ display favorable release kinetics without affecting cell proliferation or attachment. In the inhibition zone test, we found that the bi-functional coating showed lasting antibacterial effects when incubated with Porphyromonas gingivalis for 2 and 4 days. Moreover, the osteodifferentiation of hBMMSCs and hASCs were increased when cultured on this bi-functional coating for 7 and 14 days. Both drugs were loaded onto the Ca-P coating at specific concentrations (10⁻⁵ M SIM; 10⁻² M MNZ) to achieve optimal release kinetics. Considering the safety, stability and low cost of SIM and MNZ, this novel bi-functional Ca-P coating technique represents a promising method to improve the performance of metal implants or other bone substitute materials, and can theoretically be easily translated to clinical applications.     

Potential lactoferrin activity against pathogenic viruses

Lactoferrin (LF) is an 80-kDa globular glycoprotein with high affinity for metal ions, particularly for iron. This protein possesses many biological functions, including the binding and release of iron and serves as one of the important components of the innate immune system, where it acts as a potent inhibitor of several pathogens. LF has efficacious antibacterial and antiviral activities against a wide range of Gram-positive and Gram-negative bacteria and against both naked and enveloped DNA and RNA viruses. In its antiviral pursuit, LF acts predominantly at the acute phase of the viral infection or even at the intracellular stage, as in hepatitis C virus infection. LF inhibits the entry of viral particles into host cells, either by direct attachment to the viral particles or by blocking their cellular receptors. This wide range of activities may be attributed to the capacity of LF to bind iron and its ability to interfere with the cellular receptors of both hosts and pathogenic microbes.     

Biosensitive and antibacterial coatings on metallic material for medical applications

Metallic materials are commonly used for load-bearing implants and as internal fixation devices. It is customary to use austenitic stainless steel, especially surgical grade type 316L SS as temporary and Ti alloys as permanent implants. However, long-term, poor bonding with bone, corrosion, and release of metal ions, such as chromium and nickel occur. These ions are powerful allergens and carcinogens and their uncontrolled leaching may be avoided by surface coatings. Therefore, bioactive glasses (BGs) became a vital biomedical material, which can form a biologically active phase of hydroxycarbonate apatite on their surface when in contact with physiological fluids. To reduce the high coefficient of friction and the brittle nature of BGs, polymers are normally incorporated to avoid the high-temperature sintering/densification of ceramic-only coatings. For medical application, electrophoretic deposition (EPD) is now used for polymer (organic) and ceramic (inorganic) components at room temperature due to its simplicity, control of coating thickness and uniformity, low cost of equipment, ability to coat substrates of intricate shape and to supply thick films in composite form, high purity of deposits as well as no phase transformation during coating. Although extensive research has been conducted on polymer/inorganic composite coatings, only some studies have reported multifunctional properties, such as biological antibacterial activity, enhanced cell adhesion, controlled drug release ability, and mechanical properties. This review will focus on biodegradable coatings, including zien, chitosan, gelatin, cellulose loaded with antibacterial drugs/metallic ions/natural herbs on biostable substrates (PEEK/PMMA/PCL/PLLA layers), which have the potential of multifunctional coating for metallic implants.     

Tricyclic GyrB/ParE (TriBE) Inhibitors: A New Class of Broad-Spectrum Dual-Targeting Antibacterial Agents

Increasing resistance to every major class of antibiotics and a dearth of novel classes of antibacterial agents in development pipelines has created a dwindling reservoir of treatment options for serious bacterial infections. The bacterial type IIA topoisomerases, DNA gyrase and topoisomerase IV, are validated antibacterial drug targets with multiple prospective drug binding sites, including the catalytic site targeted by the fluoroquinolone antibiotics. However, growing resistance to fluoroquinolones, frequently mediated by mutations in the drug-binding site, is increasingly limiting the utility of this antibiotic class, prompting the search for other inhibitor classes that target different sites on the topoisomerase complexes. The highly conserved ATP-binding subunits of DNA gyrase (GyrB) and topoisomerase IV (ParE) have long been recognized as excellent candidates for the development of dual-targeting antibacterial agents with broad-spectrum potential. However, to date, no natural product or small molecule inhibitors targeting these sites have succeeded in the clinic, and no inhibitors of these enzymes have yet been reported with broad-spectrum antibacterial activity encompassing the majority of Gram-negative pathogens. Using structure-based drug design (SBDD), we have created a novel dual-targeting pyrimidoindole inhibitor series with exquisite potency against GyrB and ParE enzymes from a broad range of clinically important pathogens. Inhibitors from this series demonstrate potent, broad-spectrum antibacterial activity against Gram-positive and Gram-negative pathogens of clinical importance, including fluoroquinolone resistant and multidrug resistant strains. Lead compounds have been discovered with clinical potential; they are well tolerated in animals, and efficacious in Gram-negative infection models.     

Fabrication and characterization of chlorhexidine gluconate loaded poly(vinyl alcohol)/45S5 nano-bioactive glass nanofibrous membrane for guided tissue regeneration applications

Polymeric barrier membranes are used in periodontal applications to prevent fibroblastic cell migration into the cavities of bone tissue and to properly guide the proliferation of tissues. In this study, the fabrication, characterization, bioactivity, and in vitro biological properties of polyvinyl alcohol-based nanofibrous membranes containing nano-sized 45S5 bioactive glass (BG) loaded with chlorhexidine (CH) gluconate with biocompatible, bioactive, and antibacterial properties for using as dental barrier membranes were investigated. Nanofibrous membranes with an average fiber diameter, pore size, and porosity of 210 nm, 24.73 μm, and 12.42%, respectively, were loaded with 1% and 2% CH, and the release profile was investigated. The presence of BG in the membranes promoted fibroblastic proliferation and the presence of CH provided antibacterial properties. Nanofibrous membranes exhibit a high ability to restrict bacterial growth while fulfilling the necessary conditions for use as a dental barrier thanks to their low swelling rates, significant surface bioactivities, and appropriate degradation levels.     

Pseudomonas aeruginosa quorum-sensing signal molecules interfere with dendritic cell-induced T-cell proliferation

Pseudomonas aeruginosa releases a wide array of toxins and tissue-degrading enzymes. Production of these malicious virulence factors is controlled by interbacterial communication in a process known as quorum sensing. An increasing body of evidence reveals that the bacterial signal molecule N -(3-oxododecanoyl)- l -homoserine lactone (OdDHL) exhibits both quorum-sensing signalling and immune-modulating properties. Recently, yet another quorum-sensing signal molecule, the Pseudomonas quinolone signal (PQS), has been shown to affect cytokine release by mitogen-stimulated human T cells. In the present article we demonstrate that both OdDHL and PQS decrease the production of interleukin-12 (IL-12) by Escherichia coli lipopolysaccharide-stimulated bone marrow-derived dendritic cells (BM-DCs) without altering their IL-10 release. Moreover, BM-DCs exposed to PQS and OdDHL during antigen stimulation exhibit a decreased ability to induce T-cell proliferation in vitro . Collectively, this suggests that OdDHL and PQS change the maturation pattern of stimulated DCs away from a proinflammatory T-helper type I directing response, thereby decreasing the antibacterial activity of the adaptive immune defence. OdDHL and PQS thus seem to possess dual activities in the infection process: as inducers of virulence factors as well as immune-modulators facilitating the infective properties of this pathogen.     

Membrane Phosphatase and Active Transport of Cations

HYDROLYSIS of ATP by the cell membrane cation transport system seems to involve a sodium-dependent phosphorylation of an intermediate followed by a potassium-activated release of inorganic phosphate¹. The K-activated and glycoside-sensitive phosphatase activity found in most cell membranes may be the expression of the ability of the cation transport system to hydrolyse phosphate esters other than the phosphorylated intermediate formed from ATP.     

Externally Controlled Triggered-Release of Drug from PLGA Micro and Nanoparticles

Biofilm infections are extremely hard to eradicate and controlled, triggered and controlled drug release properties may prolong drug release time. In this study, the ability to externally control drug release from micro and nanoparticles was investigated. We prepared micro/nanoparticles containing ciprofloxacin (CIP) and magnetic nanoparticles encapsulated in poly (lactic-co-glycolic acid) PLGA. Both micro/nanoparticles were observed to have narrow size distributions. We investigated and compared their passive and externally triggered drug release properties based on their different encapsulation structures for the nano and micro systems. In passive release studies, CIP demonstrated a fast rate of release in first 2 days which then slowed and sustained release for approximately 4 weeks. Significantly, magnetic nanoparticles containing systems all showed ability to have triggered drug release when exposed to an external oscillating magnetic field (OMF). An experiment where the OMF was turned on and off also confirmed the ability to control the drug release in a pulsatile manner. The magnetically triggered release resulted in a 2-fold drug release increase compared with normal passive release. To confirm drug integrity following release, the antibacterial activity of released drug was evaluated in Pseudomonas aeruginosa biofilms in vitro. CIP maintained its antimicrobial activity after encapsulation and triggered release.     

High-performance liquid chromatographic separation of fluoroquinolone enantiomers: a review

Fluoroquinolones are antibacterial agents widely used clinically. In recent years, there has been an important development of new derivatives, and more than 7000 analogues have been described today. Different fluoroquinolones (FQ) have one or two chiral centers in their chemical structure and are available as racemates, diastereoisomers, or pure enantiomers. The clinical and pharmaceutical uses of these compounds need effective analytical procedures for quality control and pharmacodynamic and pharmacokinetic studies. This review article focuses on the high-performance liquid chromatographic separation of fluoroquinolone stereoisomers by the use of derivatization methods and ligand exchange (LE) or chiral liquid chromatography.     

The relationship between lysosomal enzyme release and protein phosphorylation in human monocytes stimulated by phorbol esters and opsonized zymosan

Since it was established that phorbol esters bind to and activate protein kinase C, a proposed mechanism of action for these compounds has been the phosphorylation of specific protein substrates (Niedel, J. E., Kuhn, L. J., and Vandenbark, G. R. (1983) Proc. Natl. Acad. Sci. U.S.A. 80, 36-40; Castagna, M., Takai, Y., Kaibuchi, K., Sano, K., Kikkawa, U., and Nishizuka, Y. (1982) J. Biol. Chem. 257, 7847-7851). To better understand this proposed relationship, we investigated the ability of a series of phorbol esters to elicit lysosomal enzyme release (LER) and specific substrate phosphorylation in human monocytes. In this system, phorbol 12-myristate 13-acetate stimulated the secretion of the lysosomal enzyme N-acetyl-beta-D-glucosaminidase in both a time- and concentration-dependent manner. Furthermore, the ability of a series of phorbol esters to stimulate LER was characterized and found to be in good agreement with the relative order of these compounds to stimulate the phosphorylation of four endogenous protein substrates. Phorbol ester-stimulated protein phosphorylation was examined in intact cell preparations and found to be concentration and structure-dependent. The phosphoproteins (pp) were designated pp28, pp55, pp61, and pp66 corresponding to their molecular masses in kilodaltons. These findings are consistent with the hypothesis that phorbol ester-mediated effects are the result of protein kinase C activation and subsequent protein phosphorylation. Finally, opsonized zymosan was found to elicit a concentration-dependent stimulation of N-acetyl-beta-D-glucosaminidase release similar in magnitude and time course to phorbol ester-stimulated LER. Opsonized zymosan also stimulated the phosphorylation of two phosphoproteins (pp61 and pp66) in a concentration-dependent manner. Specific phosphorylation of pp61 and pp66 by both secretagogues, phorbol 12-myristate 13-acetate and opsonized zymosan, suggests these two proteins may be key to the functional response of LER in human monocytes.     

Fluoroquinolones and their importance in modern chemotherapy of infectious diseases

Experimental and clinical data on antibacterial drugs belonging to fluorine derivatives of quinolone carboxylic acid (quinolones of the third generation) were summarized. Brief characteristics of their antibacterial activity and experimental data on chemotherapeutic activity of pefloxacin, a fluoroquinolone on models of septicopyemia and meningoencephalitis in experiments with mice infected by P. aeruginosa, Staphylococcus and Klebsiella are presented. High efficacy of pefloxacin was shown and its advantages over dioxidine and gentamicin on the model of meningoencephalitis were revealed. The main indications to the use of fluoroquinolones, possible adverse reactions and contraindications to the use of the drugs of that group are described.