## 6 Combining Active and Passive Antibiofilm Strategies
The diblock copolymer was prepared by group transfer polymerization (GTP). GTP is a controlled living polymerization technique that allows polymerization of acrylate monomers in the presence of a silyl ketene acetal as an initiator and nucleophilic or electrophilic catalysts [121]. More specifically, the synthesis started with polymerization of the first monomer that is 2-(dimethylamino)ethyl methacrylate (DMA) initiated by 1-methoxy-1-trimethysiloxy-2-methyl-1-propene (MTS) and conducted in the presence of tetra-\(n\)-butyl ammonium dibenzoate (TBABB) as a nucleophilic oxyanion catalyst [122] under rigorously anhydrous conditions in an inert nitrogen atmosphere. Polymerization of the resulted living PDMA homopolymer was continued further with the second monomer that is 2-(diisopropylamino)ethyl methacrylate (DPA)and eventually the living diblock copolymer was quenched by adding methanol. Selective betailization of the DMA residues in the PDMA-\(b\)-PDPA diblock copolymer was achieved by treatment with 10 mol % excess (based on DMA residues) of 1,3-propane sulfone at room temperature. Scheme 14 depicts the whole synthetic pathway used to prepare the \(\beta\)PDMA-\(b\)-PDPA diblock copolymer [119; 120; 123]. The diblock copolymer was dissolved in 1 mM NaH\({}_{2}\)PO\({}_{4}\) buffer at pH 3.0 to achieve a final concentration of 0.1-0.2 mg/mL. Micellization occurred upon the gradual addition of a 0.1 M NaOH solution up to pH 7.5. Self-assembled monolayers of \(\beta\)PDMA-\(b\)-PDPA micelles were prepared using a simple dip-coating technique by immersing the silicon wafer or glass slides substrates into an aqueous solution of the diblock copolymer at pH 7.5 for 3 h. The deposition process was driven electrostatically through attractions between the quaternized amino groups of the zwitterionic \(\beta\)-PDMA-coronal chains and the partially negatively charged silanol groups of the substrate. To evaluate the adhesion of _S. aureus_ on substrates modified with these zwitterionic micellar coatings, the authors performed a series of complementary tests including viable cell counting, microscopic fluorescence assays using live/dead staining, and phase-contrast imaging as well as crystal violet staining assay. The outcomes of these tests revealed the capacity of \(\beta\)PDMA-\(b\)- PDPA micellar monolayers to reduce biofilm formation by 45% and short-term adhesion of bacterial cells by up to 95% as compared to control unmodified substrates. Moreover, the authors prepared \(\beta\)-PDMA-\(b\)-PDPA micelles loaded with the hydrophobic antimicrobial agent triclosan [120]. First, triclosan was dissolved in ethanol at a concentration of 2.5 mg/mL and 1 mL of this solution was diluted 200-fold in a 1 mM NaH\({}_{2}\)PO\({}_{4}\) buffer at pH 3.0. Next, the \(\beta\)-PDMA-\(b\)-PDPA diblock copolymer was introduced in the above solution, and micellization was induced by raising the pH to 7.5. Multilayer coatings were fabricated by LbL assembly of \(\beta\)PDMA-\(b\)-PDPA micelles and poly(sodium 4-styrene sulfonate) (PSS) at pH 7.5. The build-up of triclosan containing multilayered films was achieved through alternate immersion of silicon wafers or glass slides into solutions of triclosan-loaded \(\beta\)PDMA-\(b\)-PDPA micelles and PSS with rinsing after each immersion step. The first deposited layer was always the zwitterionic copolymer micelles layer. The number of layers in the multilayered coatings was found to be of crucial importance for the anti-adhesive properties against _S. aureus_, the best results at physiological pH being obtained for a three-layer film configuration [120]. Three-layer films also displayed significant anti-adhesive properties at pH 7.5 against _E. coli_. Furthermore, pH-triggered smart triclosan released from the multilayer films was achieved by dropping the environmental pH to 5.5. pH lowering results in gradual protonation of the amine groups in the hydrophobic PDPA core, which renders them hydrophilic, thereby causing disassembly of the micellar aggregates and release of the encapsulated triclosan.