Coating of bioactive glasses with chitosan: The effects of the glass composition and coating method on the surface properties, including preliminary in vitro results.

Two bioactive glasses were coated with chitosan: SCNB belongs to the SiO 2 -CaO-Na 2 O system, and SCNA has the addition of Al 2 O 3 to enhance chemical stability. Different coating methods were compared: direct physical attachment, surface activation through tresyl chloride, and polydopamine as a linker. The samples were characterized through SEM-EDS, contact angle measurements, FTIR, zeta potential titrations, tape tests, in vitro precipitation of hydroxylapatite (bioactivity), and cell cultures (RAW 264.7 and UMR-106) on some selected samples. Direct physical attachment (in acetic acid) or use of polydopamine allowed complete surface coverage, while it dropped to one-quarter on both glasses by using tresyl chloride. The coating had a contact angle of about 80° and it well showed typical functional groups (FTIR). The coatings on SCNA were chemically and mechanically stable (classified as 4-5B by the tape tests, partially maintained after soaking for 14 days), and showed an isoelectric point around 8. On SCNB, the coatings were unstable (classified as 0-3B, dissolved during soaking) but bioactivity was preserved. The coating affected the biological outcome of SCNA with M0/M1 polarization (1 day) and reduced viability of macrophages (3 days), while osteoblastic cells showed poor adhesion but maintained cell viability and osteogenic potential (3–7 days). [Display omitted] • Bioactive glasses could be coated with chitosan. • Direct physical attachment or use of polydopamine allowed complete surface coverage. • A chemically stable bioactive glass allowed stable coating. • A coated reactive bioactive glass was still bioactive but the coating was unstable. • The coating affected the macrophages' and osteoblasts' response. [ABSTRACT FROM AUTHOR]