Nontoxic antimicrobial micellar systems based on mono- and dicationic Dabco-surfactants and furazolidone: Structure-solubilization properties relationships

Permeability, anti-inflammatory and anti-VEGF profiles of steroidal-loaded cationic nanoemulsions in retinal pigment epithelial cells under oxidative stress

Age-related macular degeneration (AMD) is defined as a degenerative, progressive and multifactorial disorder that affects the macula with a complex etiology. The retinal pigment epithelium is a monolayer of cells that has the function to separate the surface of the choroid from the neural retina that is involved in the signal transduction leading to vision. The blood-aqueous barrier and the blood retinal barrier limit the permeation of drugs into the retina and thereby reducing their efficacy. Triamcinolone acetonide (TA) is widely used as anti-inflammatory and immunomodulatory drug that promotes the inhibition of the inflammatory processes. The factors that stimulate or inhibit angiogenesis in AMD create a local balance that is responsible for the growth of sub-retinal neovascularization. In AMD, the main angiogenic stimulus is the vascular endothelial growth factor (VEGF). In this work, nanoemulsions with cationic surfactants (mono- and dicationic DABCO and quinuclidine) were produced to deliver TA, and were found to reduce the production of tumor necrosis factor alpha (TNF-α), which stimulates the choroidal neovascularization development by upregulating the VEGF production, and consequently decreased the VEGF levels. Our results support the potential use of mono- and dicationic DABCO and quinuclidine-based cationic nanoemulsions for the delivery of TA in the treatment of AMD.

DABCO-Customized Nanoemulsions: Characterization, Cell Viability and Genotoxicity in Retinal Pigmented Epithelium and Microglia Cells

Quaternary derivatives of 1,4-diazabicyclo[2.2.2]octane (DABCO) and of quinuclidine surfactants were used to develop oil-in-water nanoemulsions with the purpose of selecting the best long-term stable nanoemulsion for the ocular administration of triamcinolone acetonide (TA). The combination of the best physicochemical properties (i.e., mean droplet size, polydispersity index, zeta potential, osmolality, viscoelastic properties, surface tension) was considered, together with the cell viability assays in ARPE-19 and HMC3 cell lines. Surfactants with cationic properties have been used to tailor the nanoemulsions’ surface for site-specific delivery of drugs to the ocular structure for the delivery of TA. They are tailored for the eye because they have cationic properties that interact with the anionic surface of the eye.

Acetoin modulates conformational change of surfactin: Interfacial assembly and crude oil-washing performance

Due to its special structure, the cyclic lipopeptide surfactin showed remarkable responsiveness to stimuli such as pH, temperature and metal ions. However, few studies investigated the effect of fermented by-products on the conformational change and interfacial assembly of surfactin. Here, the effect of acetoin, a primary metabolite of Bacillus subtilis, on the conformational change and interfacial assembly of surfactin was studied in detail. Surface tension measurements showed that the critical micelle concentration (CMC) of surfactin increased from 1.14 × 10^-5 to 4.32 × 10^-5 M in the presence of acetoin. Moreover, acetoin has increased the interfacial tension of surfactin aqueous solution-crude oil from 1.08 mN/m to 3.01 mN/m. Circular dichroism (CD) spectra and dynamic light-scattering (DLS) further demonstrated that acetoin had induced the conformational transition of surfactin from β-sheet to β-turn structure, and caused surfactin forming some larger micelle aggregations. Afterwards, it was further found that acetoin decreased the oil sand cleaning efficiency of surfactin from 59.7% to 6.6%, and deteriorated the O/W emulsion stability and altered the silicate wettability toward less water wet state. Based on the experimental results, a possible mechanism of the interaction between surfactin and acetoin was proposed.

Bi-functional sterically hindered phenol lipid-based delivery systems as potential multi-target agents against Alzheimer's disease via an intranasal route

New lipid-based nanomaterials and multi-target directed ligands (MTDLs) based on sterically hindered phenol, containing a quaternary ammonium moiety (SHP-s-R, with s = 2,3) of varying hydrophobicity (R = CH2Ph and CnH2n+1, with n = 8, 10, 12, 16), have been prepared as potential drugs against Alzheimer's disease (AD). SHP-s-R are inhibitors of human cholinesterases with antioxidant properties. The inhibitory potency of SHP-s-R and selectivity ratio of cholinesterase inhibition were found to significantly depend on the length of the methylene spacer (s) and alkyl chain length. The compound SHP-2-16 showed the best IC50 for human AChE and the highest selectivity, being 30-fold more potent than for human BChE. Molecular modeling of SHP-2-16 binding to human AChE suggests that this compound is a dual binding site inhibitor that interacts with both the peripheral anionic site and catalytic active site. The relationship between self-assembly parameters (CMC, solubilization capacity, aggregation number), antioxidant activity and a toxicological parameter (hemolytic action on human red blood cells) was investigated. Two sterically hindered phenols (SHP-2-Bn and SHP-2-R) were loaded into L-α-phosphatidylcholine (PC) nanoparticles by varying the SHP alkyl chain length. For the brain AChE inhibition assay, PC/SHP-2-Bn/SHP-2-16 nanoparticles were administered to rats intranasally at a dose of 8 mg kg-1. The Morris water maze experiment showed that scopolamine-induced AD-like dementia in rats treated with PC/SHP-2-Bn/SHP-2-16 nanoparticles was significantly reduced. This is the first example of cationic SHP-phospholipid nanoparticles for inhibition of brain cholinesterases realized by the use of intranasal administration. This route has promising potential for the treatment of AD.

Cationic Surfactants: Self-Assembly, Structure-Activity Correlation and Their Biological Applications

The development of biotechnological protocols based on cationic surfactants is a modern trend focusing on the fabrication of antimicrobial and bioimaging agents, supramolecular catalysts, stabilizers of nanoparticles, and especially drug and gene nanocarriers. The main emphasis given to the design of novel ecologically friendly and biocompatible cationic surfactants makes it possible to avoid the drawbacks of nanoformulations preventing their entry to clinical trials. To solve the problem of toxicity various ways are proposed, including the use of mixed composition with nontoxic nonionic surfactants and/or hydrotropic agents, design of amphiphilic compounds bearing natural or cleavable fragments. Essential advantages of cationic surfactants are the structural diversity of their head groups allowing of chemical modification and introduction of desirable moiety to answer the green chemistry criteria. The latter can be exemplified by the design of novel families of ecological friendly cleavable surfactants, with improved biodegradability, amphiphiles with natural fragments, and geminis with low aggregation threshold. Importantly, the development of amphiphilic nanocarriers for drug delivery allows understanding the correlation between the chemical structure of surfactants, their aggregation behavior, and their functional activity. This review focuses on several aspects related to the synthesis of innovative cationic surfactants and their broad biological applications including antimicrobial activity, solubilization of hydrophobic drugs, complexation with DNA, and catalytic effect toward important biochemical reaction.

Soft Cationic Nanoparticles for Drug Delivery: Production and Cytotoxicity of Solid Lipid Nanoparticles (SLNs)

The surface properties of nanoparticles have decisive influence on their interaction with biological barriers (i.e., living cells), being the concentration and type of surfactant factors to have into account. As a result of different molecular structure, charge, and degree of lipophilicity, different surfactants may interact differently with the cell membrane exhibiting different degrees of cytotoxicity. In this work, the cytotoxicity of two cationic solid lipid nanoparticles (SLNs), differing in the cationic lipids used as surfactants CTAB (cetyltrimethylammonium bromide) or DDAB (dimethyldioctadecylammonium bromide), referred as CTAB-SLNs and DDAB-SLNs, respectively, was assessed against five different human cell lines (Caco-2, HepG2, MCF-7, SV-80, and Y-79). Results showed that the cationic lipids used in SLN production highly influenced the cytotoxic profile of the particles, with CTAB-SLNs being highly cytotoxic even at low concentrations (IC50 < 10 µg/mL, expressed as CTAB amount). DDAB-SLNs produced much lower cytotoxicity, even at longer exposure time (IC50 from 284.06 ± 17.01 µg/mL (SV-80) to 869.88 ± 62.45 µg/mL (MCF-7), at 48 h). To the best of our knowledge, this is the first report that compares the cytotoxic profile of CTAB-SLNs and DDAB-SLNs based on the concentration and time of exposure, using different cell lines. In conclusion, the choice of the right surfactant for biological applications influences the biocompatibility of the nanoparticles. Regardless the type of drug delivery system, not only the cytotoxicity of the drug-loaded nanoparticles should be assessed, but also the blank (non-loaded) nanoparticles as their surface properties play a decisive role both in vitro and in vivo.