Doxycycline inclusion in β-cyclodextrin increases in vitro antibiotic activity on Staphylococcus aureus and osteoblast viability Menezes AC*, Peñaranda DFS, Bonilla JC, Trajano VCC, Gontijo SML, Denadai AML, Sinisterra RD, Cortes ME Odontologia Restauradora - UNIVERSIDADE FEDERAL DE MINAS GERAIS Doxycycline (Dx) is an antibiotic derived from tetracycline being commonly used in the treatment of periodontal disease. Inclusion complexes have been prepared with beta-cyclodextrin (βCD) in order to avoid bacterial resistance and chemical instability. In this study, we evaluated the in vitro antimicrobial activity of doxycycline:beta-cyclodextrin (Dx:βCD, 1:1 molar ratio) inclusion compound. For this, minimum inhibitory concentration (MIC) against Staphylococcus aureus (S. aureus, ATCC 27664) and its interaction with cellular membrane (zeta potential quantification; ZP) were assessed. Also, Dx:βCD citotoxicity on osteoblast was quantified by MTT metabolism (tetrazolium salt). Our data have shown that MIC values of Dx:βCD were six-fold higher than Dx alone, suggesting that inclusion of Dx improved its antimicrobial activity. In agreement, we showed that Dx:βCD compound displayed a significant increased binding on S. aureus membrane, as revealed by reduced ZP values (Dx isoelectrical point:1 mg/mL; Dx:βCD: 0.16 mg/mL). Also, inclusion of Dx to βCD led to significant increasing in osteoblast viability in comparison to Dx alone. We concluded that when doxycycline was complexed with βCD a more effective inhibition on S. aureus growth was achieved, with no cytotoxic effects on osteoblasts. Also, Dx interaction with S. aureus membrane was enhanced following βCD inclusion, suggesting that the improved antimicrobial efficacy of βCD compounds may be explained by a closer Dx-bacteria membrane interaction. (Apoio: CAPES)