Surface modification of poly(dimethylsiloxane) by two-step plasma treatment for further grafting with chitosan–Rose Bengal photosensitizer

Polydimethylsiloxane (PDMS) finds applications in pharmaceutical and medical devices, due to its biocompatibilityand biodurability. This work was aimed at grafting chitosan–Rose Bengal (CH.RB) on PDMS substratesto reduce the risks of bacterial infection during surgical application. PDMS was activated with argonplasma and functionalized with acrylic acid to introduce carboxyl moieties for further covalent coupling reactionwith CH.RB amino groups. The accessible carboxylic groups on the acrylic acid functionalized PDMS(PDMS-pAAc) surface were quantified to be 1.9 ± 0.1 μg/cm2 by toluidine blue-O colorimetricmethod. The appearanceof ATR-FTIR absorption peaks at 3100–3700, 1726 and 1633 cm−1 in the PDMS-pAAc ATR-FTIR spectrumsuggestedthe introduction of carboxyl groups, whereas the peaks at 1651 and 1590 cm−1 in the ATR-FTIRspectrum of CH.RB functionalized PDMS (PDMS-pAAc-CH.RB) evidenced the amide bond formation. Analysis ofdeconvoluted C1s peak in XPS spectra confirmed surface chemical modification at each functionalization step.Surface wettability was affected by surface functionalization: PDMS was hydrophobic (111°), whereasPDMS-pAAc and PDMS-pAAc-CH.RB were hydrophilic (55° and 58° respectively). PDMS-pAAC-CH.RB antibacterialactivity was preliminarily investigated using planktonic cells of Escherichia coli ATCC 25922 andStaphylococcus aureus ATCC 6538.