Monitoring of antimicrobial drug chloramphenicol release from electrospun nano-and microfiber mats using UV imaging and bacterial bioreporters

New strategies are continuously sought for the treatment of skin and wound infections due to increased problems with non-healing wounds. Electrospun nanofiber mats with antibacterial agents as drug delivery systems provide opportunities for the eradication of bacterial infections as well as wound healing. Antibacterial activities of such mats are directly linked with their drug release behavior. Traditional pharmacopoeial drug release testing settings are not always suitable for analyzing the release behavior of fiber mats intended for the local drug delivery. We tested and compared different drug release model systems for the previously characterized electrospun chloramphenicol (CAM)-loaded nanofiber (polycaprolactone (PCL)) and microfiber (PCL in combination with polyethylene oxide) mats with different drug release profiles. Drug release into buffer solution and hydrogel was investigated and drug concentration was determined using either high-performance liquid chromatography, ultraviolet-visible spectrophotometry, or ultraviolet (UV) imaging. The CAM release and its antibacterial effects in disc diffusion assay were assessed by bacterial bioreporters. All tested model systems enabled to study the drug release from electrospun mats. It was found that the release into buffer solution showed larger differences in the drug release rate between differently designed mats compared to the hydrogel release tests. The UV imaging method provided an insight into the interactions with an agarose hydrogel mimicking wound tissue, thus giving us information about early drug release from the mat. Bacterial bioreporters showed clear correlations between the drug release into gel and antibacterial activity of the electrospun CAM-loaded mats

Pinus sylvestris L. and other conifers as natural sources of ascorbic acid

Context: There is a widespread opinion that needles of conifers are a good source of ascorbic acid and may help to cure and prevent scurvy. Aims: To determine the content of ascorbic acid in needles and shoots of Pinus sylvestris, Picea abies, Juniperus communis and several other conifers. Methods: Ascorbic acid content was analyzed by HPLC: aminocolumn 250 mm x 4.6 mm, 5 µm; mobile phase acetonitrile and 0.05 M KH2PO4 (75:25), flow rate 1.0 mL/min, detection at 266 nm. Results: The fresh needles contained more (10.8 x 10-3%) of ascorbic acid than the fresh shoots (5.4 x 10-3%) of the same P. sylvestris tree. In needles collected during one year with monthly intervals from the same pine tree the content of vitamin C varied from 0.5 x 10-3% to 15.7 x 10-3%. The needles gathered in winter from November to March contained much more of ascorbic acid (5.2-15.7 x 10-3%) than needles collected during warmer season (0.5-2.8 x 10-3%). The fresh needles of compared conifers (n=11) contained ascorbic acid from 0% (Tuja occidentalis) to 15.0 x 10-3% (Tsuga canadensis), needles of J. communis contained ascorbic acid a little more (13.3 x 10-3%) than needles of P. sylvestris, P. abies and Microbiota decussata (9.0-10.8 x 10-3%). Conclusions: The concentration of ascorbic acid in needles and shoots of studied conifers is rather low if compared to other natural sources of vitamin C. Fresh plant material of P. sylvestris, P. abies and J. communis contained more ascorbic acid than frozen material. The concentration of ascorbic acid in needles of these three trees was higher than in shoots

Electrospun Amphiphilic Nanofibers as Templates for In Situ Preparation of Chloramphenicol-Loaded Liposomes

The hydration of phospholipids, electrospun into polymeric nanofibers and used as templates for liposome formation, offers pharmaceutical advantages as it avoids the storage of liposomes as aqueous dispersions. The objective of the present study was to electrospin and characterize amphiphilic nanofibers as templates for the preparation of antibiotic-loaded liposomes and compare this method with the conventional film-hydration method followed by extrusion. The comparison was based on particle size, encapsulation efficiency and drug-release behavior. Chloramphenicol (CAM) was used at different concentrations as a model antibacterial drug. Phosphatidylcoline (PC) with polyvinylpyrrolidone (PVP), using ethanol as a solvent, was found to be successful in fabricating the amphiphilic composite drug-loaded nanofibers as well as liposomes with both methods. The characterization of the nanofiber templates revealed that fiber diameter did not affect the liposome size. According to the optical microscopy results, the immediate hydration of phospholipids deposited on the amphiphilic nanofibers occurred within a few seconds, resulting in the formation of liposomes in water dispersions. The liposomes appeared to aggregate more readily in the concentrated than in the diluted solutions. The drug encapsulation efficiency for the fiber-hydrated liposomes varied between 14.9 and 28.1% and, for film-hydrated liposomes, between 22.0 and 77.1%, depending on the CAM concentrations and additional extrusion steps. The nanofiber hydration method was faster, as less steps were required for the in-situ liposome preparation than in the film-hydration method. The liposomes obtained using nanofiber hydration were smaller and more homogeneous than the conventional liposomes, but less drug was encapsulated

Interactions between Chloramphenicol, Carrier Polymers, and Bacteria–Implications for Designing Electrospun Drug Delivery Systems Countering Wound Infection

Antibacterial drug-loaded electrospun nano- and microfibrous dressings are of major interest as novel topical drug delivery systems in wound care. In this study, chloramphenicol (CAM)-loaded polycaprolactone (PCL) and PCL/poly­(ethylene oxide) (PEO) fiber mats were electrospun and characterized in terms of morphology, drug distribution, physicochemical properties, drug release, swelling, cytotoxicity, and antibacterial activity. Computational modeling together with physicochemical analysis helped to elucidate possible interactions between the drug and carrier polymers. Strong interactions between PCL and CAM together with hydrophobicity of the system resulted in much slower drug release compared to the hydrophilic ternary system of PCL/PEO/CAM. Cytotoxicity studies confirmed safety of the fiber mats to murine NIH 3T3 cells. Disc diffusion assay demonstrated that both fast and slow release fiber mats reached effective concentrations and had similar antibacterial activity. A biofilm formation assay revealed that both blank matrices are good substrates for the bacterial attachment and formation of biofilm. Importantly, prolonged release of CAM from drug-loaded fibers helps to avoid biofilm formation onto the dressing and hence avoids the treatment failure