Antibacterial Agent-Loaded, Novel In Situ Forming Implants Made with Poly(Isosorbide Sebacate) and Dimethyl Isosorbide as a Solvent for Periodontitis Treatment

Isosorbide-based aliphatic polyesters are a promising class of biodegradable polymers for biomedical applications, representing an attractive alternative to poly(α-hydroxy acids). Derived from the bio-based bicyclic diol, they combine structural rigidity, tunable hydrophilicity, and enhanced biocompatibility, making them suitable for drug delivery and sustainable medical devices. In this study, we developed novel in situ forming implant (ISFI) formulations composed of poly(isosorbide sebacate) (PISEB) and dimethyl isosorbide (DMI), and evaluated their applicability for local delivery of doxycycline hyclate (DOXY), minocycline hydrochloride (MIN), and/or eugenol (EUG). Basic characteristics of new ISFI formulations were investigated. Rheological analysis demonstrated that the liquid formulations exhibited shear-thinning behavior, which is advantageous for ISFI systems. However, the MIN-loaded formulation exhibited excessively rapid drug release, with a pronounced initial burst (86.4 ± 5.9%) within 24 h, whereas the DOXY-loaded system showed a lower burst of 41.1 ± 5.9% over the same period. The effect of EUG addition on depot morphology and antibiotic release profiles was also assessed. In vitro drug release studies demonstrated that EUG reduced the release rate of both antibiotics, increasing and prolonging their antibacterial activity. Eugenol co-released with antibiotics also reduced the pro-inflammatory effect of the released antibiotic doses by more than tenfold.