Unraveling the mechanism of octenidine and chlorhexidine on membranes: Does electrostatics matter?

Abstract

The increasing problem of antibiotic resistance in bacteria requires the development of new antimicrobial candidates. There are several well-known substances with commercial use, but their molecular mode of action is not fully understood. In this work, we focus on two commonly used antimicrobial agents from the detergent family-octenidine dichloride (OCT) and chlorhexidine digluconate (CHX). Both of them are reported to be agents selectively attacking the cell membrane through interaction inducing membrane disruption by emulsification. They are believed to present electrostatic selectivity toward charged lipids. In this study, we tested this hypothesis and revised previously proposed molecular mechanisms of action. Employing a variety of techniques such as molecular dynamics, z potential with dynamic light scattering, vesicle fluctuation spectroscopy, carboxyfluorescein leakage measurement, and fluorescence trimethylammonium-diphenylhexatriene-and diphenylhexatrienebased studies for determination of OCT and CHX membrane location, we performed experimental studies using two model membrane systems-zwitterionic PC and negatively charged PG (18:1/18:1):PC (16:0/18:1) 3:7, respectively. These studies were extended by molecular dynamics simulations performed on a three-component bacterial membrane model system to further test interactions with another negatively charged lipid, cardiolipin. In summary, our study demonstrated that detergent selectivity is far more complicated than supposed simple electrostatic interactions. Although OCT does disrupt the membrane, our results suggest that its primary selectivity was more linked to mechanical properties of the membrane. On the other hand, CHX did not disrupt membranes as a primary activity, nor did it show any sign of electrostatic selectivity toward negatively charged membranes at any stage of interactions, which suggests membrane disruption by influencing more discrete membrane properties.

Mechanistic Understanding from Molecular Dynamics in Pharmaceutical Research 2: Lipid Membrane in Drug Design

“…Levofloxacin [236][237][238], Clarithromycin [236], Isoniazid N -acylated derivatives [239], Rifampicin [234,240], Mangostin [241], Trimethoprim [242], Negamycin [243] Potential antibiotic Kanamycin A [133], nTZDpa and its derivatives [244], Cholic acid derived amphiphiles [245], γ-terpineol [246], Bithionol [247] Antimicrobial compound Chlorhexidine [248][249][250], Triclosan [251], Octenidine [250] Antiparasitic Praziquantel [252] Antiviral drugs Darunavir [253], Amantadine [254][255][256], Spiro[pyrrolidine-2,2 -adamantane] [254,255], 20,30-dideoxyadenosine (Didanosine) [242], Saffron [257] Antifungal drug Itraconazole, [184,186,187,258], Nystatin [259], Amphotericin B [260] Rheumatoid arthritis Lapatinib [213] Nonsteroidal antiinflammatory drugs, inhibitor of cyclooxygenase-1 and -2…”

A Systematic Approach: Molecular Dynamics Study and Parametrisation of Gemini Type Cationic Surfactants

“…Finally, data from both geometry and a Hessian matrix were used for parametrisation of modelled particles and the force fields creation. This approach was successfully used beforehand to create force fields for various particles [18,50,51]. In Supporting Materials (SM) we have delivered the detailed base of modelled 250 particles (see Microsoft Excel datasheet) with optimised force fields (see included zip file).…”

“…As previously stated, Gemini molecules are well-known for their antimicrobial activity. It was considered by Epand et al [21] as well as shown in the OCT studies, that this effect is related to membrane disruption [18]. The effect of those Gemini molecules on the membrane properties was assessed to determine the properties that most likely correspond to the antimicrobial effect.…”

“…Specifically, those from Saccharide (Sch) and Alkyl Bispyridinamine (Alk) group. In our previous work we highlighted that mechanical parameter such as bending rigidity play an important role in OCT mode of action [18]. To this end we selected this parameter as a likely and promising candidate that correspond to antimicrobial activity.…”

“…The studies reporting the interactions and the effect of Gemini on membranes-with particular emphasis on their properties and potential rupture-are scarce in the literature. There are only available few studies on commercially available Gemini surfactants such as octenidine (OCT) [18][19][20]. This is quite surprising as membrane destruction was emphasised as one of the potential targets for antimicrobial effect [21,22].…”