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Strongly Adhesive and Antimicrobial Peptide-Loaded, Alginate–Catechol-Based Gels for Application against Periimplantitis

Background: Periimplantitis is a disease linked to oral virulent bacteria such as P. gingivalis that grow in dental implants surrounding tissues and between implants and abutments. Antimicrobial gels previously described to fill these sites lose their effectiveness and resorb over time. Objective: Characterization of biophysical and antimicrobial properties of an original hydrogel, Alginate–Catechol (Alg–Cat), combined to D-Cateslytin (D-CTL). Methods: Gelation kinetics, frequency and strain sweep measurements were performed by rheology. Antibacterial activity of the gels was tested against P. gingivalis, and the MIC was determined. Peptides released from the gels were purified by HPLC and characterized by MALDI–TOF mass spectrometry. The behavior of bacteria in contact with the gel was observed using optical and electronic microscopy (SEM and TEM). Results: Gelation was fast and was achieved in 2 min with a storage modulus between 25 and 30 Pa. The gels were stable under strain and showed an adhesive potential reinforced with aging at 18 h (5.4 kPa) under a slow retraction speed (4 J·m−2 at 10 µm/s) with a mixed rupture profile (adhesive/cohesive). The MIC of D-CTL inside the Alg–Cat gel against P. gingivalis was equal to 470 µg·mL−1 after 24 h. Peptides recovered in the supernatant and inside the gel were fragmented, most of them conserving the ⍺-helix active site. No bacteria were visualized at the surface and inside the gel after 24 h. This gel is promising for clinical application for the prevention of periimplantitis.