Correlation of Physicochemical and Antimicrobial Properties of Liposomes Loaded with (+)‐Usnic Acid

Abstract

+)-Usnic acid (UA) is a natural substance that displays pharmacological activity, but it is barely soluble in water, so it was included in liposomes in order to study its properties. First, the effects of phospholipid structure and loading methodology on UA entrapment efficacy were evaluated. Then, the physicochemical and biological properties (UA delivery efficacy to Staphylococcus aureus bacterial cells) of different liposome formulations containing structurally related amphiphiles derived from L-prolinol were fully investigated. Entrapment efficiency of UA with passive loading by incubation was 80-100 molar percentage, which is related to lipophilicity of the drug and to the packing and fluidity of the bilayer. Some of the investigated formulations show the potential of UA in delivery systems (minimum inhibitory concentration of liposomal UA: 8 μg/mL) and even subtle variations of the molecular structure of lipids can significantly affect the liposomes' physicochemical properties and efficiency of drug release. μL of liposomes not previously incubated with bacteria (blank sample) and 2970 μL of Mueller-Hinton medium used in biological experiments.

UV Properties and Loading into Liposomes of Quinoline Derivatives

“…In fact, differences in the lipid chain length and/or in the degree of unsaturation affected the features of the aggregates they form [36,37]. Moreover, in a previous work, we observed that subtle variations of the polar headgroup and/or of the alkyl chain region of minor components of liposome formulations influenced the antibacterial activity of the active principle included in the vesicle bilayer [38]. Scheme 2.…”

Quatsomes Formulated with l-Prolinol-Derived Surfactants as Antibacterial Nanocarriers of (+)-Usnic Acid with Antioxidant Activity

“…35 Briefly, for the antibacterial susceptibility, 100 μL of a bacterial suspension in a 0.9% saline solution (NaCl) at a concentration of 5 × 10 –5 CFU/mL was added to the wells of a 96-well microtiter plate containing 100 μL of 2-fold serially diluted free UA and quatsomes loaded with UA (with both loading methodologies) in cation-adjusted Mueller–Hinton broth. The experiments were then carried out as reported in ref ( 10 ).…”

“…In a previous investigation, liposomes containing analogous structurally related l -prolinol derivatives showed a good ability to efficiently deliver UA to S. aureus bacterial cells. 10 Because the biological activity of UA in some cases can be related to the antioxidant one, 26 we assessed also the antioxidant effectiveness of quatsomes/UA. In fact, we previously showed that this property can significantly vary as a function of the composition of the systems in which it is included.…”

Cyclic and Acyclic Amine Oxide Alkyl Derivatives as Potential Adjuvants in Antimicrobial Chemotherapy against Methicillin-Resistant Staphylococcus aureus with an MDR Profile

“…They are zwitterionic amphiphilic compounds at physiological pH, bearing a strong polar N–O bond with a high electron density on the oxygen atom [ 37 ]. In particular, these surfactants, coming from selective modification of their amphiphilic molecular structure, have opened the scenario to a plethora of systems [ 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 ], providing different superstructures by their self-assembly and co-assembly with other materials. They show multifunctional capabilities and are used in several industrial applications, such as washing-up products and laundry detergents, foaming and wetting agents, softeners and thickeners, besides being components of hair and body care products [ 46 , 47 , 48 ].…”