Nele De Smet

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.

Modification of polydimethylsiloxane surfaces using benzophenone.

New biocompatible materials have been obtained by different modifications of polydimethylsiloxane (PDMS) surfaces. PDMS is of great interest for several biomedical applications. For some applications the native silicone does not provide an optimal performance. PDMS attracts proteins and salts. To reduce protein adhesion and salt deposition selected monomers were grafted by radical polymerization on the silicone surface. The conditions for surface modifications of PDMS using benzophenone as UV initiator were optimized. The modified surfaces were characterized properly using different methods. The effect of surface modifications on the albumin, as model protein, deposition was tested in an in vitro model.

Biocompatibility properties of surface-modified poly(dimethylsiloxane) for urinary applications.

An electronic sensor system for urinary bladder pressure monitoring requires an imbedding into a biocompatible, flexible, and liquid-impermeable material. Poly(dimethylsiloxane) (PDMS) was selected in the present set-up as packaging material because it fulfills the abovementioned requirements. However, the surface of PDMS is hydrophobic and causes undesired interactions with salts, proteins, and cells present in urine. To reduce possible interactions of urine salts in the urinary bladder, monomers, [2-(methacryloyloxy)ethyl]-dimethyl-3-sulfopropyl-ammonium hydroxide (sulfobetaine) and 2-acrylamido-2-methylpropyl sulfonic acid, were grafted onto the surface through oxygen plasma treatment. A reduction in salt deposition between the pure PDMS and the modified PDMS was observed both in vitro (artificial urine flow over the surface) and in vivo (implants into the urinary bladder of experimental pigs). Additionally, a 10-fold reduction in salt deposition was observed in vitro due to grafting of the monomers onto the surface. These modified PDMS materials proved also to be biocompatible in cell cultures, which was further confirmed by histological screening of the bladder tissue after implantation in an in vivo pig model.