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Abstract Urinary tract infections (UTIs) are the most common bacterial infections and uropathogenic Escherichia coli (UPEC) is the main etiological agent of UTIs. UPEC can persist in bladder cells protected by immunological defenses and antibiotics and intracellular behavior leads to difficulty in eradicating the infection. The aim of this paper is to design, prepare and characterize surfactant-based nanocarriers (niosomes) able to entrap antimicrobial drug and potentially to delivery and release antibiotics into UPEC-infected cells. In order to validate the proposed drug delivery system, gentamicin, was chosen as “active model drug” due to its poor cellular penetration. The niosomes physical–chemical characterization was performed combining different techniques: Dynamic Light Scattering Fluorescence Spectroscopy, Transmission Electron Microscopy. Empty and loaded niosomes were characterized in terms of size, ζ-potential, bilayer features and stability. Moreover, Gentamicin entrapped amount was evaluated, and the release study was also carried out. In addition, the effect of empty and loaded niosomes was studied on the invasion ability of UPEC strains in T24 bladder cell monolayers by Gentamicin Protection Assay and Confocal Microscopy. The observed decrease in UPEC invasion rate leads us to hypothesize a release of antibiotic from niosomes inside the cells. The optimization of the proposed drug delivery system could represent a promising strategy to significatively enhance the internalization of antimicrobial drugs.

Most clinical isolates of both Staphylococcus aureus and Staphylococcus epidermidis show the capacity to adhere to abiotic surfaces and to develop biofilms resulting in a contribution to chronic human skin infections. Antibiotic resistance and poor biofilm penetration are the main causes of ineffective therapeutic treatment in killing bacteria within biofilms. A possible strategy could be represented by drug delivery systems, such as nanoemulsions (composed of bioactive oil, surfactant and water phase), which are useful for enhancing the drug permeation of a loaded drug inside the biofilm and its activity. Phytochemical characterization of Pistacia lentiscus oil (LO) by direct infusion Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) allowed the identification of bioactive compounds with antimicrobial properties, including fatty acids and phenolic compounds. Several monoterpenes and sesquiterpenes have been also detected and confirmed by gas chromatography–mass spectrometric (GC-MS) analysis, together providing a complete metabolomic profiling of LO. In the present study, a nanoemulsion composed of LO has been employed for improving Levofloxacin water solubility. A deep physical–chemical characterization of the nanoemulsion including hydrodynamic diameter, ζ-potential, morphology, entrapment efficiency, stability release and permeation studies was performed. Additionally, the antimicrobial/antibiofilm activity of these preparations was evaluated against reference and clinical Staphylococcus spp. strains. In comparison to the free-form antibiotic, the loaded NE nanocarriers exhibited enhanced antimicrobial activity against the sessile forms of Staphylococcus spp. strains.

Mycobacterium abscessus (Mabs) is a dangerous non-tubercular mycobacterium responsible for severe pulmonary infections in immunologically vulnerable patients, due to its wide resistance to many different antibiotics which make its therapeutic management extremely difficult. Drug nanocarriers as liposomes may represent a promising delivery strategy against pulmonary Mabs infection, due to the possibility to be aerosolically administrated and to tune their properties in order to increase nebulization resistance and retainment of encapsulated drug. In fact, liposome surface can be modified by decoration with mucoadhesive polymers to enhance its stability, mucus penetration and prolong its residence time in the lung. The aim of this work is to employ Chitosan or ε-poly-L-lysine decoration for improving the properties of a novel liposomes composed by hydrogenated phosphatidyl-choline from soybean (HSPC) and anionic 1,2-Dipalmitoyl-sn-glycero-3-phosphorylglycerol sodium salt (DPPG) able to entrap Rifampicin. A deep physicochemical characterization of polymer-decorated liposomes shows that both polymers improve mucoadhesion without affecting liposome features and Rifampicin entrapment efficiency. Therapeutic activity on Mabs-infected macrophages demonstrates an effective antibacterial effect of ε-poly-L-lysine liposomes with respect to chitosan-decorated ones. Altogether, these results suggest a possible use of ε-PLL liposomes to improve antibiotic delivery in the lung.

Infections caused by bacterial biofilms represent a global health problem, causing considerable patient morbidity and mortality in addition to an economic burden. Escherichia coli, Staphylococcus aureus, and other medically relevant bacterial strains colonize clinical surfaces and medical devices via biofilm in which bacterial cells are protected from the action of the immune system, disinfectants, and antibiotics. Several approaches have been investigated to inhibit and disperse bacterial biofilms, and the use of drug delivery could represent a fascinating strategy. Ciprofloxacin (CIP), which belongs to the class of fluoroquinolones, has been extensively used against various bacterial infections, and its loading in nanocarriers, such as niosomes, could support the CIP antibiofilm activity. Niosomes, composed of two surfactants (Tween 85 and Span 80) without the presence of cholesterol, are prepared and characterized considering the following features: hydrodynamic diameter, ζ-potential, morphology, vesicle bilayer characteristics, physical-chemical stability, and biological efficacy. The obtained results suggest that: (i) niosomes by surfactants in the absence of cholesterol are formed, can entrap CIP, and are stable over time and in artificial biological media; (ii) the CIP inclusion in nanocarriers increase its stability, with respect to free drug; (iii) niosomes preparations were able to induce a relevant inhibition of biofilm formation.

Tuberculosis remains one of the world’s deadliest infectious diseases, accounting for nearly 1.3 million deaths every year. Tuberculosis treatment is challenging because of the toxicity, decreased bioavailability at the target site of the conventional drugs and, most importantly, low adherence of patients; this leads to drug resistance. Here, we describe the development of suitable nanocarriers with specific physicochemical properties to efficiently deliver two potent antimycobacterial compounds. We prepared nanoemulsions and niosomes formulations and loaded them with two different MmpL3 inhibitors previously identified (NEs + BM635 and NIs + BM859). NEs + BM635 and NIs + BM859 were deeply characterized for their physicochemical properties and anti-mycobacterial activity. NEs + BM635 and NIs + BM859 showed good hydrodynamic diameter, ζ-Potential, PDI, drug-entrapment efficiency, polarity, and microviscosity and stability. Even though both formulations proved to perform well, only NIs + BM859 showed potent antimycobacterial activity against M. tuberculosis (MIC = 0.6 µM) compared to that of the free compound. This is most probably caused by the fact that BM635, being highly hydrophobic, encounters maximum hindrance in diffusion, whereas BM859, characterized by high solubility in aqueous medium (152 µM), diffuses more easily. The niosomal formulation described in this work may be a useful therapeutic tool for tuberculosis treatment, and further studies will follow to characterize the in vivo behavior of the formulation.

Treatment of pulmonary infections caused by Mycobacterium abscessus are extremely difficult to treat, as this species is naturally resistant to many common antibiotics. Liposomes are vesicular nanocarriers suitable for hydrophilic and lipophilic drug loading, able to deliver drugs to the target site, and successfully used in different pharmaceutical applications. Moreover, liposomes are biocompatible, biodegradable and nontoxic vesicles and nebulized liposomes are efficient in targeting antibacterial agents to macrophages. The present aim was to formulate rifampicin-loaded liposomes (RIF–Lipo) for lung delivery, in order to increase the local concentration of the antibiotic. Unilamellar liposomal vesicles composed of anionic DPPG mixed with HSPC for rifampicin delivery were designed, prepared, and characterized. Samples were prepared by using the thin-film hydration method. RIF–Lipo and unloaded liposomes were characterized in terms of size, ζ-potential, bilayer features, stability and in different biological media. Rifampicin’s entrapment efficiency and release were also evaluated. Finally, biological activity of RIF-loaded liposomes in Mycobacterium abscessus-infected macrophages was investigated. The results show that RIF-lipo induce a significantly better reduction of intracellular Mycobacterium abscessus viability than the treatment with free drug. Liposome formulation of rifampicin may represent a valuable strategy to enhance the biological activity of the drug against intracellular mycobacteria.

Hyaluronic acid (HA) is one of the most used biopolymers in the development of drug delivery systems, due to its biocompatibility, biodegradability, non-immunogenicity and intrinsic-targeting properties. HA specifically binds to CD44; this property combined to the EPR effect could provide an option for reinforced active tumor targeting by nanocarriers, improving drug uptake by the cancer cells via the HA-CD44 receptor-mediated endocytosis pathway. Moreover, HA can be easily chemically modified to tailor its physico-chemical properties in view of specific applications. The derivatization with cholesterol confers to HA an amphiphilic character, and then the ability of anchoring to niosomes. HA-Chol was then used to coat Span® or Tween® niosomes providing them with an intrinsic targeting shell. The nanocarrier physico-chemical properties were analyzed in terms of hydrodynamic diameter, ζ-potential, and bilayer structural features to evaluate the difference between naked and HA-coated niosomes. Niosomes stability was evaluated over time and in bovine serum. Moreover, interaction properties of HA-coated nanovesicles with model membranes, namely liposomes, were studied, to obtain insights on their interaction behavior with biological membranes in future experiments. The obtained coated systems showed good chemical physical features and represent a good opportunity to carry out active targeting strategies.

The chemopreventive potential of Resveratrol (RV) against bladder cancer and its mechanism of action have been widely demonstrated. The physicochemical properties of RV, particularly its high reactivity and low solubility in aqueous phase, have been limiting factors for its bioavailability and in vivo efficacy. In order to overcome these limitations, its inclusion in drug delivery systems needs to be taken into account. In particular, oil-in-water (O/W) nanoemulsions (NEs) have been considered ideal candidates for RV encapsulation. Since surfactant and oil composition can strongly influence NE features and their application field, a ternary phase diagram was constructed and evaluated to select a suitable surfactant/oil/water ratio. The selected sample was deeply characterized in terms of physical chemical features, stability, release capability and cytotoxic activity. Results showed a significant decrease in cell viability after the incubation of bladder T24 cancer cells with RV-loaded NEs, compared to free RV. The selected NE formulation was able to preserve and improve RV cytotoxic activity by a more rapid drug uptake into the cells. O/W NEs represent an effective approach to improve RV bioavailability.

Satureja montana essential oil (SEO) presents a wide range of biological activities due to its high content of active phytochemicals. In order to improve the essential oil’s (EO) properties, oil in water nanoemulsions (NEs) composed of SEO and Tween-80 were prepared, characterized, and their antimicrobial and antibiofilm properties assayed against Escherichia coli strains isolated from healthy chicken. Since surfactant and oil composition can strongly influence NE features and their application field, a ternary phase diagram was constructed and evaluated to select a suitable surfactant/oil/water ratio. Minimal inhibitory concentration and minimal bactericidal concentration of NEs, evaluated by the microdilution method, showed that the SEO NE formulation exhibited higher inhibitory effects against planktonic E. coli than SEO alone. The quantification of biofilm production in the presence of NEs, assessed by crystal violet staining and scanning electron microscopy, evidenced that sub-MIC concentrations of SEO NEs enable an efficient reduction of biofilm production by the strong producer strains. The optimized nanoemulsion formulation could ensure food safety quality, and counteract the antibiotic resistance of poultry associated E. coli, if applied/aerosolized in poultry farms.