Synergistic Antibacterial Effects of Metallic Nanoparticle Combinations.

Metallic nanoparticles have unique antimicrobial properties that make them suitable for use within medical and pharmaceutical devices to prevent the spread of infection in healthcare. The use of nanoparticles in healthcare is on the increase with silver being used in many devices. However, not all metallic nanoparticles can target and kill all disease-causing bacteria. To overcome this, a combination of several different metallic nanoparticles were used in this study to compare effects of multiple metallic nanoparticles when in combination than when used singly, as single elemental nanoparticles (SENPs), against two common hospital acquired pathogens (Staphylococcus aureus and Pseudomonas. aeruginosa). Flow cytometry LIVE/DEAD assay was used to determine rates of cell death within a bacterial population when exposed to the nanoparticles. Results were analysed using linear models to compare effectiveness of three different metallic nanoparticles, tungsten carbide (WC), silver (Ag) and copper (Cu), in combination and separately. Results show that when the nanoparticles are placed in combination (NPCs), antimicrobial effects significantly increase than when compared with SENPs (P < 0.01). This study demonstrates that certain metallic nanoparticles can be used in combination to improve the antimicrobial efficiency in destroying morphologically distinct pathogens within the healthcare and pharmaceutical industry.

Gyrospun antimicrobial nanoparticle loaded fibrous polymeric filters.

A one step approach to prepare hybrid nanoparticle embedded polymer fibres using pressurised gyration is presented. Two types of novel antimicrobial nanoparticles and poly(methylmethacrylate) polymer were used in this work. X-ray diffraction analysis of the nanoparticles revealed Ag, Cu and W are the main elements present in them. The concentration of the polymer solution and the nanoparticle concentration had a significant influence on the fibre diameter, pore size and morphology. Fibres with a diameter in the range of 6-20µm were spun using 20wt% polymer solutions containing 0.1, 0.25 and 0.5 wt% nanoparticles under 0.3MPa working pressure and a rotational speed of 36,000rpm. Continuous, bead-free fibre morphologies were obtained for each case. The pore size in the fibres varied between 36 and 300nm. Successful incorporation of the nanoparticles in polymer fibres was confirmed by energy dispersive x-ray analysis. The fibres were also gyrospun on to metallic discs to prepare filters which were tested for their antibacterial activity on a suspension of Pseudomonas aeruginosa. Nanoparticle loaded fibres showed higher antibacterial efficacy than pure poly(methylmethacrylate) fibres.

Rheology and pressurised gyration of starch and starch-loaded poly(ethylene oxide).

This work investigates the rheology and spinning of starch and starch-loaded poly(ethylene oxide) (PEO) by pressurised gyration in order to prepare nanofibres. The spinning dope's rheological properties played a crucial role in fibre formation. Newtonian behaviour is observed in 1-20 wt% starch suspensions and non-Newtonian behaviour is found in all the PEO-starch mixtures. Pressurised gyration of the starch suspensions produced beads only but PEO-starch mixtures generated fibres. The fibre diameter of the PEO-starch samples is shown to be a function of polymer concentration and rotating speed of the gyration system. Fibre formation can only be facilitated below a certain working pressure. The concentration of starch in the PEO-starch mixtures is crucial in defining whether beaded or continuous fibres were generated and this is related to the composition of the spinning dope. FT-IR, XRD and microscopy studies indicated very good miscibility of starch and PEO in the nanofibres. The storage modulus of the PEO-starch were also studied as a function of temperature (30-150°C) and showed interesting results but it was not possible to deduce general trends valid for the entire temperature range.

Antimicrobial properties of electrically formed elastomeric polyurethane-copper oxide nanocomposites for medical and dental applications.

With the rapidly advancing field of nanotechnology having an impact in several areas interfacing life and physical sciences, the potential applications of nanoparticles as antimicrobial agents have been realized and offer great opportunities in addressing several viral and bacterial outbreak issues. Polyurethanes (PUs) are a diverse class of polymeric materials which also have applications in several areas of biomedical science ranging from blood contact devices to implantable dental technologies. In this report, copper oxide (CuO) nanoparticles (mean size ∼50 nm) are embedded into a PU matrix via two electrical fabrication processes. To elucidate the antimicrobial activity, a range of different loading compositions of CuO within the PU matrix (0%, 1%, 5%, and 10% w/w) are electrospun to form thin porous films (thickness < 10 µm). After washing, the films are tested for their antimicrobial properties against methicillin-resistant Staphylococcus aureus (MRSA). Significant reduction of populations was demonstrated with 10% w/w CuO over a 4-h period. This approach demonstrates the potential of generating tailored antimicrobial structures for a host of applications, such as designer filters, patterned coatings, breathable fabrics, adhesive films (as opposed to sutures), and mechanically supporting structures.