A multifunctional composite of an antibacterial higher-valent silver metallopharmaceutical and a potent wound healing polypeptide: a combined killing and healing approach to wound care

The present study relates to a combined killing and healing approach for the treatment of infected wounds. Herein we report a multifunctional, including antimicrobial and wound healing, composite containing a conjugate of a bi-valent silver polydiguanide that demonstrated high antibacterial activity in vitro and a potent wound healing polypeptide, histatin-1, for the treatment of infected wounds. The synthesis of silver(II) chlorhexidine [Ag(II)CHX] was accomplished by the oxidation of Ag(I), followed by the complexation of the oxidized metal with chlorhexidine (CHX), whereas the metal complex conjugate of the solid phase-synthesized histatin polypeptide (Hst-1), Hst-1-[Ag(II)CHX], was realized by mixing the starting materials in aqueous solution. The change in the Hst-1 structure upon binding with the silver complex was examined by circular dichroism spectroscopy. The wound healing applicability of the histatin polypeptide and its metal complex conjugate was tested using the synthesized Hst-1 and Hst-1-[Ag(II)CHX] complex on 3T3-L1 preadipocytes in a cell-spreading assay. The antibacterial activity of the silver metal complex and its Hst-1 conjugate was tested against several gram positive and gram negative bacteria, including Methicillin-resistant Staphylococcus aureus (MRSA) and Methicillin-resistant coagulase negative staphylococcus (MRCNS) by a broth microdilution method. The results of these experiments revealed that the polypeptide and silver(II) polydiguanide complex retained their individual wound healing and antimicrobial activity even in their conjugate. The conjugate of an antibacterial higher-valent silver polydiguanide complex with a potent wound healing polypeptide (Hst-1) showed promise as a new multifunctional therapeutic wherein the killing and healing functions of the constituent materials are preserved together for the development of new-generation wound-care agents.