Efficacy of antimicrobial polymer coatings in an animal model of bacterial infection associated with foreign body implants.

OBJECTIVES: To assess support discs, comprising polyethylene terephthalate (PET), coated with different polymer/levofloxacin combinations for antimicrobial activity in an animal model of infection, in order to explore the use of specific polymer coatings incorporating levofloxacin as a means of reducing device-related infections. METHODS: Aliphatic polyester-polyurethanes containing different ratios of poly(lactic acid) diol and poly(caprolactone) diol were prepared, blended with levofloxacin and then used to coat support discs. The in vitro levofloxacin release profiles from these discs were measured in aqueous solution. Mice were surgically implanted with the coated discs placed subcutaneously and infection was initiated by injection of 10(6) cfu of Staphylococcus aureus into the subcutaneous pocket containing the implant. After 5, 10, 20 and 30 days, the discs were removed, and the number of bacteria adhering to the implant and the residual antimicrobial activity of the discs were determined. RESULTS: In vitro, the release of levofloxacin from the coated discs occurred at a constant rate and then reached a plateau at different timepoints, depending on the polymer preparation used. In vivo, none of the discs coated with polymer blends containing levofloxacin was colonized by S. aureus, whereas 94% of the discs coated with polymer alone were infected. All discs coated with levofloxacin-blended polymers displayed residual antimicrobial activity for at least 20 days post-implantation. CONCLUSIONS: Bioerodable polyester-polyurethane polymer coatings containing levofloxacin can prevent bacterial colonization of implants in an intra-operative model of device-related infections.

Intra-articular Treatment of Osteoarthritis with Diclofenac-Conjugated Polymer Reduces Inflammation and Pain.

The most common treatment for osteoarthritis is daily oral administration of a nonsteroidal anti-inflammatory drug such as diclofenac. This daily dosage regime is often associated with severe side effects. In this study, we explored the potential of utilizing a high molecular weight cross-linked polyurethane polymer covalently linked to diclofenac (C-DCF-PU) for intra-articular administration. We aim to exploit the advantages of local drug delivery by developing an implant with improved efficacy and reduced side effects. The polymer was synthesized from a diclofenac-functionalized monomer unit in a simple one-pot reaction, followed by cross-linking. In vitro drug release studies showed zero-order drug release for 4 days, followed by a gradual decline in drug release rate until diclofenac was depleted after 15 days. The cross-linked polymer was triturated to yield an injectable microgel formulation for administration. Whole animal fluorescence imaging of the rhodamine-labeled C-DCF-RH-PU showed good retention of the polymer in the knee joints of healthy rats, with approximately 30% of the injected dose still present 2 weeks post intra-articular administration. In a reactivation arthritis animal model, the C-DCF-RH-PU formulation reduced pain and significantly reduced inflammation after a short lag phase, showing that this drug delivery system warrants further development for long-term treatment of osteoarthritis with the benefit of reduced side effects.

Precise control of drug loading and release of an NSAID-polymer conjugate for long term osteoarthritis intra-articular drug delivery.

A facile synthesis method of polymer diclofenac conjugates (PDCs) based on biocompatible polyurethane chemistry that provides a high drug loading and offers a high degree of control over diclofenac (DCF) release kinetics is described. DCF incorporating monomer was reacted with ethyl-l-lysine diisocyanate (ELDI) and different amounts of polyethylene glycol (PEG) in a one-step synthesis to yield polymers with pendent diclofenac distributed along the backbone. By adjusting the co-monomers feed ratio, the drug loading could be tailored accordingly to give DCF loading of up to 38 w/w%. The release rate could also be controlled easily by changing the amount of PEG in the backbone. Above 10 w/w% of PEG, the in vitro DCF release studies in physiological conditions showed an apparent zero-order profile without an initial burst effect for up to 120 days. The PDCs described may be suitable for long-term intra-articular (IA) delivery for the treatment of osteoarthritis (OA).

The Hydrolysis of Diclofenac Esters: Synthetic Prodrug Building Blocks for Biodegradable Drug-Polymer Conjugates.

Degradation reactions on diclofenac-monoglycerides (3a,b), diclofenac-(p-hydroxybenzoate)-2-monoglyceride (3c), diclofenac (1), and diclofenac lactam (4) were performed at 37 °C in isotonic buffer solutions (apparent pH range 1-8) containing varying concentrations of acetonitrile (ACN). The concentration remaining of each analyte was measured versus time. Diclofenac-monoglycerides and diclofenac-(p-hydroxybenzoate)-2-monoglyceride (3c) were both found to undergo facile and complete hydrolysis in pH 7.4 isotonic phosphate buffer/10% ACN. Under mildly acidic, neutral or alkaline conditions, diclofenac-(p-hydroxybenzoate)-2-monoglyceride (3c) had the fastest hydrolysis rate (t1/2 = 3.23 h at pH 7.4), with simultaneous formation of diclofenac lactam (4) and diclofenac (1). Diclofenac-monoglycerides (3a,b) hydrolyzed more slowly under the same conditions, to again yield both diclofenac (1) and diclofenac lactam (4). There was also transesterification of diclofenac-2-monoglyceride (3b) to its regioisomer, diclofenac-1-monoglyceride (3a) across the pH range. Diclofenac was shown to be stable in neutral or alkaline conditions but cyclized to form the lactam (4) in acidic conditions. Conversely, the lactam (4) was stable under acidic conditions but was converted to an unknown species under alkaline or neutral conditions.

Recreational drug use within the employees of the mariculture and seafood industry in South Australia.

A study of recreational drug use among workers in the Port Lincoln mariculture and seafood industries was conducted by self report questionnaire. High rates of cannabis and alcohol use were revealed during the shore based fish farming season. The occupational health and safety implications of these findings in one of Australia's most dangerous industries are significant. Further research could inform the development of industry specific harm minimisation policies.