No abstract

Mediastinitis occurs after cardiac surgery and is a major threat to patient’s life due to postoperative bleeding and deep sternal wound infection. Major challenge in treating this condition is that it demands a material that should adhere to the applied site and act as both a hemostatic and an antibacterial agent. On the basis of this we have developed an in situ forming tissue adhesive chitin–fibrin (CH-FB) gel with tigecycline loaded gelatin nanoparticles (tGNPs) for controlling bleeding and preventing bacterial infection. Spherical shaped tGNPs (231 ± 20 nm) were prepared and characterized. In situ forming tGNPsCH-FB gel was formed using a dual syringe applicator in which one syringe was loaded with a mixer of fibrinogen solution, chitin gel, and tGNPs; the other syringe was loaded with a mixture of thrombin solution, chitin gel, and tGNPs. Both these mixtures were injected together. In situ gel formed within a minute and exhibited excellent tissue adhesive property. tGNPsCH-FB gel was found to be cyto-compatible against human umbilical vein endothelial cells (HUVECs). Sustained release of tigecycline from tGNPsCH-FB gel was found to occur over 21 days. In vitro antibacterial activity of tGNPsCH-FB gel was tested against Staphylococcus aureus, methicillin-resistant Staphylococcus aureus (MRSA), Escherichia coli (E. coli), and their clinical isolates. Furthermore, in vivo hemostatic potential of tGNPsCH-FB gel was evaluated in deep organ injuries created in Sprague–Dawley rats. The developed gel exhibited rapid blood clotting potential by achieving hemostasis within 154 and 84 s under femoral artery (pressured) and liver (oozing) bleeding conditions. Hence, these findings exhibit the potential application of the developed tGNPsCH-FB gel to adhere at surgical site for controlling bleeding and prevent bacterial infection after cardiac surgery.

Major autolysin (Atl) of Staphylococcus aureus is a cell surface associated peptidoglycan hydrolase with amidase and glucosaminidase domains. Atl enzymes (amidase and glucosaminidase) are known to participate in biofilm formation and also can bind with host matrices. Earlier studies demonstrated the binding of Atlwithfibronectin, thrombospondin 1, vitronectin and heat shock cognate protein Hsc70. Here, we have shown, Atl mediates attachment of S.aureus to heparin and gelatine as well. The atl mutant strain demonstrated around 2.5 fold decreased adherence with fibronectin, gelatin and heparin coated microtiter plates. The microscopic studies confirmed the reduced binding of atl mutant with them compared to its parental wild type and complemented mutant strains. Amidase and glucosaminidase were expressed as N -terminal histidine tagged proteins from Escherichia coli , purified and refolded. We found refolded amidase bind with fibronectin, gelatin and heparin; whereas refolded glucosaminidase binds with only fibronectin and heparin but not gelatin. These results reemphasize Atl as one of the crucial proteins from Staphylococcus that facilitate their binding with multiple host cellular components during colonization and infection.

No abstract