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

• We performed a plasma-mediated surface modification of PDMS.
• An antibacterial copolymer (photozyme) was covalently bound to PDMS surface.
• Surface functionalization was demonstrated at each step.
• Antibacterial properties of coated PDMS were preliminarily investigated.
• We showed coating potential antibacterial activity against gram-positive bacteria.

Polydimethylsiloxane (PDMS) finds applications in pharmaceutical and medical devices, due to its biocompatibility and biodurability. This work was aimed at grafting chitosan–Rose Bengal (CH.RB) on PDMS substrates to reduce the risks of bacterial infection during surgical application. PDMS was activated with argon plasma and functionalized with acrylic acid to introduce carboxyl moieties for further covalent coupling reaction with 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 colorimetric method. The appearance of ATR-FTIR absorption peaks at 3100–3700, 1726 and 1633 cm− 1 in the PDMS-pAAc ATR-FTIR spectrum suggested the introduction of carboxyl groups, whereas the peaks at 1651 and 1590 cm− 1 in the ATR-FTIR spectrum of CH.RB functionalized PDMS (PDMS-pAAc-CH.RB) evidenced the amide bond formation. Analysis of deconvoluted C1s peak in XPS spectra confirmed surface chemical modification at each functionalization step. Surface wettability was affected by surface functionalization: PDMS was hydrophobic (111°), whereas PDMS-pAAc and PDMS-pAAc-CH.RB were hydrophilic (55° and 58° respectively). PDMS-pAAC-CH.RB antibacterial activity was preliminarily investigated using planktonic cells of Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 6538.