Prevention of Candida albicans biofilm formation by covalently bound dimethylaminoethylmethacrylate and polyethylenimine.

Candida albicans biofilms are a major cause of voice prosthesis deterioration in laryngectomized patients. The aim of this study was to produce a surface capable of inhibiting C. albicans biofilm formation. Dimethylaminoethylmethacrylate (DMAEMA) and polyethylenimine (PEI) moieties were covalently bound to the surface of polydimethylsiloxane (PDMS) or polymethylmethacrylate (PMMA) and subsequently quaternized. Physicochemical characterization of the grafted surfaces was carried out and their effect on C. albicans cell numbers was assessed using a modified Robbins device to grow the biofilms. Covalently bound quaternized polyDMAEMA (polyDMAEMAq) and PEI (PEIq) inhibited biofilm growth, with reductions up to 92%. Our approach may show promise for future application in medical devices such as catheters and prostheses.

Candida albicans biofilm formation on peptide functionalized polydimethylsiloxane.

In order to prevent biofilm formation by Candida albicans, several cationic peptides were covalently bound to polydimethylsiloxane (PDMS). The salivary peptide histatin 5 and two synthetic variants (Dhvar 4 and Dhvar 5) were used to prepare peptide functionalized PDMS using 4-azido-2,3,5,6-tetrafluoro-benzoic acid (AFB) as an interlinkage molecule. In addition, polylysine-, polyarginine-, and polyhistidine-PDMS surfaces were prepared. Dhvar 4 functionalized PDMS yielded the highest reduction of the number of C. albicans biofilm cells in the Modified Robbins Device. Amino acid analysis demonstrated that the amount of peptide immobilized on the modified disks was in the nanomole range. Poly-d-lysine PDMS, in particular the homopeptides with low molecular weight (2500 and 9600) showed the highest activity against C. albicans biofilms, with reductions of 93% and 91%, respectively. The results indicate that the reductions are peptide dependent.

Inhibition of Candida albicans biofilm formation by antimycotics released from modified polydimethyl siloxane.

Unlike various disinfectants, antifungals have not been commonly incorporated so far in medical devices, such as catheters or prostheses, to prevent biofilm formation by Candida spp. In the present study, five antimycotics were added to polydimethyl siloxane (PDMS) disks via admixture (nystatin) or impregnation (trimethylsilyl-nystatin (TMS-nystatin), miconazole, tea tree oil (TTO), zinc pyrithione). Nystatin-medicated PDMS disks exhibited a concentration-dependent inhibitory effect on biofilm formation in a microtiter plate (MTP) but not in a Modified Robbins Device (MRD). This observation, together with HPLC data and agar diffusion tests, indicates that a small fraction of free nystatin is released, which kills Candida albicans cells in the limited volume of a MTP well. In contrast, biofilm inhibition amounted to more than one log unit in the MRD on disks impregnated with miconazole, TTO, and zinc pyrithione. It is hypothesized that the reduction in biofilm formation by these compounds in a flow system occurs through a contact-dependent effect.

Polypropylene grafted with smart polymers (PNIPAAm/PAAc) for loading and controlled release of vancomycin.

New smart surface-modified polypropylene (PP) was prepared for improving the loading and the sustained delivery of vancomycin and, thus, reducing the risk of biofilm formation when used as component of biomedical devices. Isothermal titration calorimetry (ITC) served for screening the most suitable monomers for grafting; the drug preferentially bonding to ionized acrylic acid (AAc). A net-PP-g-PNIPAAm-inter-net-PAAc was synthesized by first grafting and cross-linking of N-isopropylacrylamide onto PP films and then interpenetrating a second network by redox polymerization and cross-linking of AAc. PP-g-PAAc slabs were prepared by grafting AAc and, optionally, cross-linking. The amount and composition of grafted polymer (FTIR-ATR), morphology (SEM), temperature- and pH-responsiveness (swelling measurements), thermal behavior (DSC), friction coefficient (rheometry), drug loading and release rate, and effect against methicillin-resistant Staphylococcus aureus (MRSA) biofilms (modified robbins device) were evaluated. Grafting of AAc notably decreased the friction coefficient from 0.28+/-0.03 to 0.05+/-0.02 and enhanced the vancomycin loading (up to 2.5mg/cm(2)). Drug-loaded films showed a pH-dependent release rate, sustaining the release in pH 7.4 aqueous media at 37 degrees C for several hours. All drug-loaded films reduced biofilm formation by MRSA; the anti-biofilm effect being statistically significant (91.7% reduction, alpha<0.05) for PP-g-PAAc with the thinnest grafting layer.

Efficacy of silver-releasing rubber for the prevention of Pseudomonas aeruginosa biofilm formation in water.

The aim of the present study was to evaluate the efficacy of Elastoguard silver-releasing rubber in preventing Pseudomonas aeruginosa biofilm formation in water. Biofilm formation by P. aeruginosa under various conditions in an in vitro model system was compared for silver-releasing and conventional rubber. Under most conditions tested, the numbers of sessile cells attached to silver-releasing rubber were considerably lower with reference to conventional rubber, although the effect diminished with increasing volumes. The release of silver also resulted in a decrease in planktonic cells. By exposing both materials simultaneously to conditions for biofilm growth, it became obvious that the antibiofilm effect was due to a reduction in the number of planktonic cells, rather than to contact-dependent killing of sessile cells. The data demonstrate that the use of silver-releasing rubber reduces P. aeruginosa biofilm in water and reduces the number of planktonic cells present in the surrounding solution.