Drug interaction and location in liposomes: correlation with polar surface areas

Investigation of miltefosine-model membranes interactions at the molecular level for two different PS levels modeling cancer cells

Miltefosine (MLT) is a broad-spectrum drug included in the alkylphospholipids (APL) used against leishmania and various types of cancer. The most crucial feature of APLs is that they are thought to only kill cancerous cells without harming normal cells. However, the molecular mechanism of action of APLs is not completely understood. The increase in the phosphatidylserine (PS) ratio is a marker showing the stage of cancer and even metastasis. The goal of this research was to investigate the molecular effects of miltefosine at the molecular level in different PS ratios. The effects of MLT on membrane phase transition, membrane orders, and dynamics were studied using DPPC/DPPS (3:1) and DPPC/DPPS (1:1) multilayer (MLV) vesicles mimicking DPPS ratio variation, Differential Scanning Calorimetry (DSC), and Fourier Transform Infrared spectroscopy (FTIR). Our findings indicate that miltefosine is evidence at the molecular level that it is directed towards the tumor cell and that the drug's effect increases with the increase of anionic lipids in the membrane depending on the stage of cancer.

Unravelling the interactions between small molecules and liposomal bilayers via molecular dynamics and thermodynamic modelling

Lipid-based drug delivery systems hold immense promise in addressing critical medical needs, from cancer and neurodegenerative diseases to infectious diseases. By encapsulating active pharmaceutical ingredients - ranging from small molecule drugs to proteins and nucleic acids - these nanocarriers enhance treatment efficacy and safety. However, their commercial success faces hurdles, such as the lack of a systematic design approach and the issues related to scalability and reproducibility. This work aims to provide insights into the drug-phospholipid interaction by combining molecular dynamic simulations and thermodynamic modelling techniques. In particular, we have made a connection between the structural properties of the drug-phospholipid system and the physicochemical performance of the drug-loaded liposomal nanoformulations. We have considered two prototypical drugs, felodipine (FEL) and naproxen (NPX), and one model hydrogenated soy phosphatidylcholine (HSPC) bilayer membrane. Molecular dynamic simulations revealed which regions within the phospholipid bilayers are most and least favoured by the drug molecules. NPX tends to reside at the water-phospholipid interface and is characterized by a lower free energy barrier for bilayer membrane permeation. Meanwhile, FEL prefers to sit within the hydrophobic tails of the phospholipids and is characterized by a higher free energy barrier for membrane permeation. Flory-Huggins thermodynamic modelling, small angle X-ray scattering, dynamic light scattering, TEM, and drug release studies of these liposomal nanoformulations confirmed this drug-phospholipid structural difference. The naproxen-phospholipid system has a lower free energy barrier for permeation, higher drug miscibility with the bilayer, larger liposomal nanoparticle size, and faster drug release in the aqueous medium than felodipine. We suggest that this combination of molecular dynamics and thermodynamics approach may offer a new tool for designing and developing lipid-based nanocarriers for unmet medical applications.

Cancer Immunotherapy Using Bioengineered Micro/Nano Structured Hydrogels

Hydrogels, a class of materials with a 3D network structure, are widely used in various applications of therapeutic delivery, particularly cancer therapy. Micro and nanogels as miniaturized structures of the bioengineered hydrogels may provide extensive benefits over the common hydrogels in encapsulation and controlled release of small molecular drugs, macromolecular therapeutics, and even cells. Cancer immunotherapy is rapidly developing, and micro/nanostructured hydrogels have gained wide attention regarding their engineered payload release properties that enhance systemic anticancer immunity. Additionally, they are a great candidate due to their local administration properties with a focus on local immune cell manipulation in favor of active and passive immunotherapies. Although applied locally, such micro/nanostructured can also activate systemic antitumor immune responses by releasing nanovaccines safely and effectively inhibiting tumor metastasis and recurrence. However, such hydrogels are mostly used as locally administered carriers to stimulate the immune cells by releasing tumor lysate, drugs, or nanovaccines. In this review, the latest developments in cancer immunotherapy are summarized using micro/nanostructured hydrogels with a particular emphasis on their function depending on the administration route. Moreover, the potential for clinical translation of these hydrogel-based cancer immunotherapies is also discussed.

Surfactant vesicles for enhanced antitoxoplasmic effect of norfloxacin: in vitro and in vivo evaluations

The goal was to scrutinize niosomes as potential carriers for enhanced efficacy of norfloxacin against Toxoplasma gondii RH strain. This was assessed in vitro and in vivo. Standard niosomes of Span 60 and cholesterol were prepared. Gelucire 48/16 or Tween 80 was incorporated as hydrophilic fluidizer. The prepared vesicles were characterized for shape, size, viscosity and norfloxacin release. The in vitro anti-Toxoplasma was assessed by monitoring tachyzoites viability after incubation with niosomes. In vivo efficacy of niosomes encapsulated norfloxacin was evaluated on infected mice. Transmission electron micrographs showed nano-sized spherical vesicles. Norfloxacin release varied with niosomal composition to show faster liberation in presence of fluidizing agent. The half maximum effective concentration of norfloxacin against tachyzoites (EC50) was significantly reduced after niosomal encapsulation compared with simple drug solution with no significant difference between vesicular formulations. Tachyzoite count in the peritoneal fluid of infected mice was reduced by 45.2, 90.8, 88.3 and 84% after treatment with simple drug dispersion, standard niosomes, Gelucire containing and Tween containing vesicles, respectively compared to infected untreated mice. These results correlate with the in vitro data and reflects the efficacy of niosomes. The study introduced surfactant vesicles as a tool for enhanced efficacy of norfloxacin against toxoplasma.

Ruthenium Complexes with Protic Ligands: Influence of the Position of OH Groups and π Expansion on Luminescence and Photocytotoxicity

Protic ruthenium complexes using the dihydroxybipyridine (dhbp) ligand combined with a spectator ligand (N,N = bpy, phen, dop, Bphen) have been studied for their potential activity vs. cancer cells and their photophysical luminescent properties. These complexes vary in the extent of π expansion and the use of proximal (6,6'-dhbp) or distal (4,4'-dhbp) hydroxy groups. Eight complexes are studied herein as the acidic (OH bearing) form, [(N,N)₂Ru(n,n'-dhbp)]Cl₂, or as the doubly deprotonated (O^- bearing) form. Thus, the presence of these two protonation states gives 16 complexes that have been isolated and studied. Complex 7_A, [(dop)₂Ru(4,4'-dhbp)]Cl₂, has been recently synthesized and characterized spectroscopically and by X-ray crystallography. The deprotonated forms of three complexes are also reported herein for the first time. The other complexes studied have been synthesized previously. Three complexes are light-activated and exhibit photocytotoxicity. The log(D_o/w) values of the complexes are used herein to correlate photocytotoxicity with improved cellular uptake. For Ru complexes 1-4 bearing the 6,6'-dhbp ligand, photoluminescence studies (all in deaerated acetonitrile) have revealed that steric strain leads to photodissociation which tends to reduce photoluminescent lifetimes and quantum yields in both protonation states. For Ru complexes 5-8 bearing the 4,4'-dhbp ligand, the deprotonated Ru complexes (5_B-8_B) have low photoluminescent lifetimes and quantum yields due to quenching that is proposed to involve the ³LLCT excited state and charge transfer from the [O₂-bpy]^2- ligand to the N,N spectator ligand. The protonated OH bearing 4,4'-dhbp Ru complexes (5_A-8_A) have long luminescence lifetimes which increase with increasing π expansion on the N,N spectator ligand. The Bphen complex, 8_A, has the longest lifetime of the series at 3.45 μs and a photoluminescence quantum yield of 18.7%. This Ru complex also exhibits the best photocytotoxicity of the series. A long luminescence lifetime is correlated with greater singlet oxygen quantum yields because the triplet excited state is presumably long-lived enough to interact with ³O₂ to yield ¹O₂.

Ruthenium pincer complexes for light activated toxicity: Lipophilic groups enhance toxicity

Nine ruthenium CNC pincer complexes (1-9) were tested for anticancer activity in cell culture under both dark and light conditions. These complexes included varied CNC pincer ligands including OH, OMe, or Me substituents on the pyridyl ring and wingtip N-heterocyclic carbene (NHC) groups which varied as methyl (Me), phenyl (Ph), mesityl (Mes), and 2,6-diisopropylphenyl (Dipp). The supporting ligands included acetonitrile, Cl, and 2,2'-bipyridine (bpy) donors. The synthesis of complexes 8 and 9 is described herein and are fully characterized by spectroscopic (1H NMR, IR, UV-Vis, MS) and analytical techniques. Single crystal X-ray diffraction results are reported herein for 8 and 9. The other complexes (1-7) are reported elsewhere. The four most lipophilic ruthenium complexes (6, 7, 8, and 9) showed the best activity vs. MCF7 cancer cells with complexes 6 and 9 showing cytotoxicity and complex 7 and 8 showing light activated photocytotoxicity. The distribution of these compounds between octanol and water is reported as log(Do/w) values, and increasing log(Do/w) values correlate roughly with improved activity vs. cancer cells. Overall, lipophilic wingtip groups (e.g. Ph, Mes, Dipp) on the NHC ring and a lower cationic charge (1+ vs. 2+) appears to be beneficial for improved anticancer activity.

Permeation enhancers loaded bilosomes for improved intestinal absorption and cytotoxic activity of doxorubicin

The clinical utility of doxorubicin is compromised due to dose related toxic side effects and limited oral bioavailability with no oral formulation being marketed. Enhancement of intestinal absorption and magnification of cytotoxicity can overcome these limitations. Accordingly, the objective was to probe penetration enhancers, bilosomes and their combinations for enhanced intestinal absorption and improved cytotoxicity of doxorubicin. Piperine and dipyridamole were tested as enhancers alone or encapsulated in bilosomes comprising Span60, cholesterol and bile salts. Bilosomes were nanosized spherical vesicles with negative zeta potential and were able to entrap doxorubicin with efficiency ranging from 45.3 % to 53 %. Intestinal absorption studies utilized in-situ rabbit intestinal perfusion which revealed site dependent doxorubicin absorption correlating with regional distribution of efflux transporters. Co-perfusion with the enhancer increased intestinal absorption with further augmentation after bilosomal encapsulation. The latter increased the % fraction absorbed by 4.5-6 and 1.8-2.5-fold from jejuno-ileum and colon, respectively, depending on bilosomes composition. Additionally, doxorubicin cytotoxicity against breast cancer cells (MCF-7) was significantly improved after bilosomal encapsulation and the recorded doxorubicin IC₅₀ value was reduced from 13.3 μM to 0.1 μM for the best formulation. The study introduced bilosomes encapsulating absorption enhancers as promising carriers for enhanced cytotoxicity and oral absorption of doxorubicin.

Events at the Interface: How Do Interfaces Modulate the Dynamics and Functionalities of Guest Molecules?

Chemical and biological interfaces are of various types, which could be between two materials of the same and/or different states, two phases of the same material, biological substrates and the outer environment, surfactant or polymeric membranes and the bulk, and so forth. Small-molecule guests frequently interact with such interfaces that decide their functionalities. The structural and behavioral properties undergo considerable characteristic changes, which control their final course of action in the targeted application. This Perspective will discuss mainly the chemical interfaces constituted by the surfactants, polymers, lipids, and nucleic acids and their impacts on the dynamics of small-molecule guests. Some specific and interesting phenomena and future prospects will be elucidated in this Perspective.

Drug–Membrane Interaction as Revealed by Spectroscopic Methods: The Role of Drug Structure in the Example of Rifampicin, Levofloxacin and Rapamycin

We have investigated the nature of the interaction of small organic drug molecules with lipid membranes of various compositions. Using infrared spectroscopy and differential scanning calorimetry methods, we studied the role of the structure of the active molecule in interaction with the membrane using the example of dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylcholine:cardiolipin (DPPC:CL) liposomes. We discovered the key role of the heterocycle in interaction with the polar part of the bilayer and the network of unsaturated bonds in interaction with the hydrophobic part. For rifampicin and levofloxacin, the main binding sites were phosphate and carbonyl groups of lipids, and in the case of anionic liposomes we found a slight penetration of rifampicin into the hydrophobic part of the bilayer. For rapamycin, experimental confirmation of the localization of the molecule in the region of fatty acid chains was obtained, and perturbation in the region of phosphate groups was demonstrated for the first time. The process of phase transition of liposomal forms of rifampicin and levofloxacin was studied. DPPC liposomes accelerate the phase transition when loaded with a drug. DPPC:CL liposomes are less susceptible to changes in the phase transition rate.

Bilosomes as Nanoplatform for Oral Delivery and Modulated In Vivo Antimicrobial Activity of Lycopene

Owing to the disseminating resistance among pathogenic bacteria, especially Klebsiella pneumoniae, there is a high need for alternate compounds with antibacterial activity. Herein, lycopene was isolated from Lycopersicon esculentum L. Molecular docking approach was employed to explore lycopene binding affinity to selected vital proteins of K. pneumoniae with the binding mechanisms being investigated. This proposed a promising antibacterial activity of lycopene. However, the pharmacological use of lycopene is hampered by its poor solubility and limited oral bioavailability. Accordingly, bilosomes were fabricated for oral lycopene delivery. The computed entrapment efficiency, mean vesicular size, and zeta potential values for the optimized formulation were 93.2 ± 0.6%, 485.8 ± 35.3 nm, and −38.3 ± 4, respectively. In vitro drug release studies revealed controlled lycopene release from constructed bilosomes, with the drug liberation being based on the Higuchi kinetics model. Transmission electron microscopic evaluation of bilosomes revealed spherical nanovesicles free from aggregates. Moreover, the in vitro and in vivo antibacterial activity of lycopene and its constructed formulations against multidrug-resistant K. pneumoniae isolates were explored. The optimized bilosomes exhibited the lowest minimum inhibitory concentrations ranging from 8 to 32 µg/mL. In addition, scanning electron microscopy revealed remarkable deformation and lysis of the bilosomes-treated bacterial cells. Regarding in vivo investigation, a lung infection model in mice was employed. The tested bilosomes reduced the inflammation and congestion in the treated mice’s lung tissues, resulting in normal-sized bronchioles and alveoli with very few congested vessels. In addition, it resulted in a significant reduction in pulmonary fibrosis. In conclusion, this study investigated the potential activity of the naturally isolated lycopene in controlling infections triggered by multidrug-resistant K. pneumoniae isolates. Furthermore, it introduced bilosomes as a promising biocompatible nanocarrier for modulation of oral lycopene delivery and in vivo antimicrobial activity.

High-Resolution Ultrasound Spectroscopy for the Determination of Phospholipid Transitions in Liposomal Dispersions

High-resolution ultrasound spectroscopy (HR-US) is a spectroscopic technique using ultrasound waves at high frequencies to investigate the structural properties of dispersed materials. This technique is able to monitor the variation of ultrasound parameters (sound speed and attenuation) due to the interaction of ultrasound waves with samples as a function of temperature and concentration. Despite being employed for the characterization of several colloidal systems, there is a lack in the literature regarding the comparison between the potential of HR-US for the determination of phospholipid thermal transitions and that of other common techniques both for loaded or unloaded liposomes. Thermal transitions of liposomes composed of pure phospholipids (dimyristoylphosphatidylcholine, DMPC; dipalmitoylphosphatidylcholine, DPPC and distearoylphosphatidylcholine, DSPC), cholesterol and their mixtures were investigated by HR-US in comparison to the most commonly employed microcalorimetry (mDSC) and dynamic light scattering (DLS). Moreover, tramadol hydrochloride, caffeine or miconazole nitrate as model drugs were loaded in DPPC liposomes to study the effect of their incorporation on thermal properties of a phospholipid bilayer. HR-US provided the determination of phospholipid sol-gel transition temperatures from both attenuation and sound speed that are comparable to those calculated by mDSC and DLS techniques for all analysed liposomal dispersions, both loaded and unloaded. Therefore, HR-US is proposed here as an alternative technique to determine the transition temperature of phospholipid membrane in liposomes.

Bicelles as a carrier for bioactive compounds in beverages: application to nerolidol, an active sesquiterpene alcohol

ABSTRACT

Nerolidol is a natural sesquiterpene alcohol with promising but limited application in food and pharmaceutical fields due to several factors including low photostability and low aqueous solubility. Recently, several carriers loading nerolidol were prepared and tested in fresh orange juice. Lipid vesicles loading nerolidol did not exhibit satisfactory organoleptic properties in this beverage. Hence, DMPC/DHPC bicelles were prepared as a new phospholipid-based carrier for nerolidol at different molar ratios. The bicelle suspensions were characterized in terms of homogeneity, particles size, and morphology. The optimal formulation (phospholipid:nerolidol molar ratio 100:1) was selected based on transparent appearance, homogeneity, and particle size (~ 45 nm). Besides, it showed a high encapsulation efficiency of nerolidol and a high incorporation rate of phospholipids. Transmission electron microscopy analysis demonstrated the formation of bicelles. The bicelles membrane fluidity was assessed by 1,6-diphenyl-1,3,5-hexatriene fluorescence anisotropy and differential scanning calorimetry analysis. The membrane fluidity of bicelles appeared to increase in the presence of nerolidol in a concentration dependent manner. To our knowledge this is the first study dealing with the encapsulation of an essential oil component in bicelles.

GRAPHIC ABSTRACT

Prolonged anesthesia and decreased toxicity of enantiomeric-excess bupivacaine loaded in ionic gradient liposomes

Bupivacaine is the most employed local anesthetic in surgical procedures, worldwide. Its systemic toxicity has directed the synthesis of the less toxic, S(-) enantiomer. This work describes a formulation of ionic gradient liposomes (IGL) containing _S75BVC, an enantiomeric excess mixture of 75% S(-) and 25% R(+) bupivacaine. IGL prepared with 250 mM (NH₄)₂SO₄ in the inner aqueous core of phosphatidylcholine and cholesterol (3:2 mol%) vesicles plus 0.5% _S75BVC showed average sizes of 312.5 ± 4.5 nm, low polydispersity (PDI < 0.18), negative zeta potentials (-14.2 ± 0.2 mV) and were stable for 360 days. The encapsulation efficiency achieved with IGL_S75BVC (%EE = 38.6%) was higher than with IGL prepared with racemic bupivacaine (IGL_RBVC, %EE = 28.3%). TEM images revealed spherical vesicles and µDSC analysis provided evidence on the interaction of the anesthetic with the lipid bilayer. Then, in vitro - release kinetics and cytotoxicity- and in vivo - toxic effects in Zebrafish and biochemical/histopathological analysis plus analgesia in Wistar rats - tests were performed. IGL_S75BVC exhibited negligible toxicity against Schwann cells and Zebrafish larvae, and it did not affect biochemical markers or the morphology of rat tissues (heart, brain, cerebellum, sciatic nerve). The in vitro release of _S75BVC from IGL was extended from 4 to 24 h, justifying the prolonged anesthetic effect measured in rats (~9 h). The advantages of IGL_S75BVC formulation over IGL_RBVC and plain bupivacaine formulations (prolonged anesthesia, preferential sensorial blockade, and no toxicity) confirm its potential for clinical use in surgical anesthesia.

In vitro phototoxicity of zinc phthalocyanine (ZnPc) loaded in liposomes against human breast cancer cells

In this study, zinc phthalocyanine (ZnPc) was encapsulated in liposomes (Phosphatidylcholine (PC) from soybean lecithin (95% phosphatidylcholine, 5% lysophosphatidylcholine), and phosphatidic acid) obtained by a reverse-phase evaporation method. Liposomes were characterized and cytotoxicity and phototoxicity assays were performed using mouse embryo fibroblast (NIH3T3) and human breast cancer (MDAMB231), respectively. ZnPc was successfully encapsulated in liposomes ([Formula: see text]80%), presenting single populations with sizes of [Formula: see text]300 nm and negative zeta potential (-35 to -40 mV). The release profile at different pH presented a biphasic release controlled by the Fickian diffusion mechanism. The cytotoxicity assays carried out on NIH3T3 cells showed that the liposomes provided good protection for ZnPc, and did not affect the viability of non-cancerous cells. In contrast, free ZnPc significantly reduced non-cancerous cell viability at higher concentrations. ZnPc loaded in liposomes ensured a higher phototoxic effect on the MDAMB231 cells at all concentrations tested when exposed to low light dose.

Predicting topical drug clearance from the skin

For topical drug products that target sites of action in the viable epidermal and/or upper dermal compartment of the skin, the local concentration profiles have proven difficult to quantify because drug clearance from the viable cutaneous tissue is not well characterised. Without such knowledge, of course, it is difficult-if not impossible-to predict a priori whether and over what time frame a topical formulation will permit an effective concentration of drug within the skin 'compartment' to be achieved. Here, we test the hypothesis that valuable information about drug disposition, and specifically its clearance, in this experimentally difficult-to-access compartment (at least, in vivo) can be derived from available systemic pharmacokinetic data for drugs administered via transdermal delivery systems. A multiple regression analysis was undertaken to determine the best-fit empirical correlation relating clearance from the skin to known or easily calculable drug properties. It was possible, in this way, to demonstrate a clear relationship between drug clearance from the skin and key physical chemical properties of the drug (molecular weight, log P and topological polar surface area). It was further demonstrated that values predicted by the model correlated well with those derived from in vitro skin experiments.

Co-encapsulation of sodium diethyldithiocarbamate (DETC) and zinc phthalocyanine (ZnPc) in liposomes promotes increases phototoxic activity against (MDA-MB 231) human breast cancer cells

There has been considerable interest in the development of novel photosensitisers for photodynamic therapy (PDT). The use of liposomes as drug delivery systems containing simultaneously two or more drugs is an attractive idea to create a new platform for PDT application. Therefore, the aim of this study was to evaluate the synergistic effect of diethyldithiocarbamate (DETC) and zinc phthalocyanine (PDT) co-encapsulated in liposomes. The reverse-phase evaporation method resulted in the successful encapsulation of DETC and ZnPc in liposomes, with encapsulation efficiencies above 85 %, mean size of 308 nm, and zeta potential of - 36 mV. The co-encapsulation decreased the cytotoxic effects in mouse embryo fibroblast (NIH3T3) cells and inhibited damage to human erythrocytes compared to free DETC + ZnPc. In addition, both the free drugs and co-encapsulated ones promoted more pronounced phototoxic effects on human breast cancer cells (MDA-MB231) compared to treatment with ZnPc alone. This synergistic effect was determined by DETC-induced decreases in the antioxidant enzyme activity of superoxide dismutase (SOD) and glutathione (GSH).

Biophysical characterization of lutein or beta carotene-loaded cationic liposomes

The interactions between carotenoids and membrane constituents are vital for understanding the mechanism of their dynamic action. Lutein and beta-carotene were loaded separately into the bilayer of dipalmitoylphosphatidylcholine (DPPC) mixed at a molar ratio with l-α-phosphatidylethanolamine derived from sheep brain (cephalin) and stearylamine (SA) to form cationic liposomes. The molecular interaction between lutein or beta-carotene with cationic liposomes was studied using transmission electron microscopy (TEM), dynamic light scattering (DLS), differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) spectroscopy. Encapsulation efficiency (EE %) and in vitro drug release were determined. The DLS measurements confirmed the mono-dispersity of all samples. TEM results revealed that liposomal samples were oval-shaped and there was a change in their morphology and size upon encapsulation of lutein or beta-carotene. Beta-carotene was observed to adhere to the boundary surface within the liposomal assembly with external morphological alterations. EE% of lutein and beta-carotene exceeded 98.8 ± 0.3% and 87 ± 4%, respectively. Lutein doped with cationic liposomes shows better in vitro release stability (about 30%) than beta-carotene (about 45%) between the 3^rd and the 6^th hour manifested by lower leakage rate percentage of lutein which would lead to higher lutein retention. The incorporated lutein resulted in broadening and shifting of the major endothermic peak of the co-liposomes, while the incorporation of beta-carotene did not induce a noticeable shift. An FTIR study was employed to reveal structure alterations in the vesicles after the encapsulation of lutein or beta-carotene into liposomes. Encapsulation of lutein or beta-carotene into liposomes induced a change in the frequency of the symmetric and asymmetric CH₂ stretching bands in the acyl chain that may influence the order of the membrane.

The interactions between carotenoids and membrane constituents are vital for understanding the mechanism of their dynamic action.

Thermodynamics of selective serotonin reuptake inhibitors partitioning into 1,2-dioleoyl-sn-glycero-3-phosphocholine bilayers

Knowledge of thermodynamics of lipid membrane partitioning of amphiphilic drugs as well as their binding site within the membrane are of great relevance not only for understanding the drugs' pharmacology but also for the development and optimization of more potent drugs. In this study, the interaction between two representatives of selective serotonin reuptake inhibitors, including paroxetine and sertraline, and large unilamellar vesicles (LUVs) composed of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) was investigated by second derivative spectrophotometry and Fourier transform infrared spectroscopy (FTIR) to determine the driving force of the drug partitioning across lipid membranes. It was found that temperature increase from 25 to 42 °C greatly enhanced the partitioning of paroxetine and sertraline into DOPC LUVs, and sertraline intercalated into the lipid vesicles to a greater extent than paroxetine in the temperature range examined. The partitioning of both drugs into DOPC LUVs was a spontaneous, endothermic and entropy-driven process. FTIR measurements suggested that sertraline could penetrate deeply into the acyl tails of DOPC LUVs as shown by the considerable shifts in the lipid's CH₂ and C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> O stretching modes induced by the drug. Paroxetine, however, could reside closer to the head groups of the lipid since its presence caused a larger shift in the PO₂⁻ bands of DOPC LUVs. The findings reported here provide valuable insights into the influence of small molecules' chemical structure on their molecular interaction with the lipid bilayer namely their possible binding sites within the lipid bilayer and their thermodynamics profiles of partitioning, which could benefit rational drug design and drug delivery systems.

Paroxetine and sertraline have the same thermodynamics profile of phospholipid bilayer partitioning but different location within the lipid bilayer.

Cellular uptake of protic ruthenium complexes is influenced by pH dependent passive diffusion and energy dependent efflux

The lipophilic vs. hydrophilic properties of three protic ruthenium compounds were studied as a function of pH. Specifically, we measured Log(D_o/w) values for [(N,N)₂Ru(6,6'-dhbp)]²⁺ complexes (where N,N = 2,2'-bipyridine (1_A), 1,10-phenanthroline (2_A), 2,3-dihydro-[1,4]dioxino[2,3-f][1,10]phenanthroline (3_A) and 6,6'-dhbp is the diprotic 6,6'-dihydroxy-2,2'-bipyridine ligand) from pH 4.0 to 8.0. This study allowed us to demonstrate that as the ligand is deprotonated at higher pH values the resulting neutral charge on the complex improves its lipophilic properties. Thus, improved uptake by passive diffusion is expected with protic ligands on Ru(II). Furthermore, cellular studies have demonstrated that passive diffusion is the dominant pathway for cellular uptake. However, metabolic inhibition has also shown that energy dependent efflux reduces the amount of the ruthenium complex (as measured by mean fluorescence intensity) in the cells. These compounds have been shown by fluorescence microscopy to accumulate in the nuclei of cancer cells (MCF7, MDA-MB-231, and HeLa). Taken together, this data shows that uptake is required for toxicity but uptake alone is not sufficient. The greatest light activated toxicity appears to occur in breast cancer cell lines with relatively moderate uptake (MCF7 and MDA-MB-231) rather than the cell line with the greatest uptake of complex 3_A (normal breast cell line MCF-10A).

Impact of Additives on the Microstructural Properties of DIDMAMS Bilayers: Studied by Molecular Dynamics Simulations

To further understand the mechanism of the impact of perfume raw materials (PRMs) such as allyl heptoate (AHT) and cashmeran (CMR) on distearoyl isopropyl dimethylammonium methyl sulfate (DIDMAMS) bilayers, 90 ns molecular dynamics simulations were conducted to investigate the structure of bilayers consisting of DIDMAMS and PRMs at 350 K on the molecular scale. Structural properties such as density profiles, order parameters, radial distribution functions (RDFs), and bilayer thickness were analyzed. The bilayers appear to be the structure of the ripple phase whether PRMs are added or not. The RDF and density profiles show that CMR molecules tend to locate in the region close to head groups and AHT molecules prefer to uniformly distribute among hydrocarbon chains. The special distribution of CMR molecules results in hydrocarbon chains twining around CMR molecules. The existence of CMR molecules between bilayers and the consequent highest bilayer thickness may be the main cause of higher viscosity. We expect that this work can help to screen stable vesicular formula and understand the relationship between microstructures of the vesicles and macroscopic fluidic properties.

Plant antimicrobial polyphenols as potential natural food preservatives

BACKGROUND

The growing demand for natural food preservatives in the last decade has promoted investigations on their application for preserving perishable foods. In this context, the present review is focused on discussing the prospective application of plant extracts containing phenolics or isolated plant phenolics as natural antimicrobials in foods. Plant essential oils are outside the scope of this review since utilization of their antimicrobial activity for food preservation has been extensively reviewed.

RESULTS

Although the exact antimicrobial mechanisms of action of phenolic compounds are not yet fully understood, it is commonly acknowledged that they have diverse sites of action at the cellular level. Antimicrobial phenolics can be added directly to the formulation of perishable food products or incorporated into food-contact materials to release them in the immediate zone of perishable foods. Edible coatings or active food packaging materials can thus be used as carriers of plant bioactive compounds.

CONCLUSION

These materials could be an interesting delivery system to improve the stability of phenolics in foods and to improve the shelf life of perishable foods. This review will thus provide an overview of current knowledge of the antimicrobial activity of phenolic-rich plant extracts and of the promises and limits of their exploitation for the preservation of perishable foods. © 2018 Society of Chemical Industry.

Advances and challenges in liposome digestion: Surface interaction, biological fate, and GIT modeling

During the past 50 years, there has been increased interest in liposomes as carriers of pharmaceutical, cosmetic, and agricultural products. More recently, much progress has been made in the use of surface-modified formulas in experimental food matrices. However, before the viability and the applications of nutrients in liposomal form in the edible field can be determined, the digestion behavior along the human gastrointestinal tract (GIT) must be clarified. In vitro digestion models, from static models to dynamic mono-/bi-/multi-compartmental models, are increasingly being developed and applied as alternatives to in vivo assays. This review describes the surface interactions of liposomes with their encapsulated ingredients and with external food components and updates the biological fate of liposomes after ingestion. It summarizes current models for the human stomach and intestine that are available and their relevance in nutritional studies. It highlights limitations and challenges in the use of these models for liposomal colloid system digestion and discusses crucial factors, such as enzymes and bile salts, that affect liposomal bilayer degradation.

Nano-formulation for topical treatment of precancerous lesions: skin penetration, in vitro, and in vivo toxicological evaluation

With the aim of improving the topical delivery of the antineoplastic drug 5-fluorouracil (5FU), it was loaded into ultradeformable liposomes composed of soy phosphatidylcholine and sodium cholate (UDL-5FU). The liposome populations had a mean size of 70 nm without significant changes in 56 days, and the ultradeformable formulations were up to 324-fold more elastic than conventional liposomes. The interaction between 5FU and the liposomal membrane was studied by three methods, and also release profile was obtained. UDL-5FU did penetrate the stratum corneum of human skin. At in vitro experiments, the formulation was more toxic on a human melanoma-derived than on a human keratinocyte-derived cell line. Cells captured liposomes by metabolically active processes. In vivo toxicity experiments were carried out in zebrafish (Danio rerio) larvae by studying the swimming activity, morphological changes, and alterations in the heart rate after incubation. UDL-5FU was more toxic than free 5FU. Therefore, this nano-formulation could be useful for topical application in deep skin precancerous lesions with advantages over current treatments. This is the first work that assessed the induction of apoptosis, skin penetration in a Saarbrücken penetration model, and the toxicological effects in vivo of an ultradeformable 5FU-loaded formulation.

Treatment merits of Latanoprost/Thymoquinone - Encapsulated liposome for glaucomatus rabbits

Elevation of the intraocular pressure (IOP) is recognized as a risk factor for glaucoma development. Latanoprost (LAT) is a prostaglandin analog used to reduce the (IOP). Thymoquinone (TQ) is a major bioactive ingredient of Nigella sativa. The aim of this study was to develop novel liposomal drug carriers for ocular delivery of LAT, TQ and a mixture of them to investigate their IOP lowering efficacy upon subconjunctival injection in glaucoma-induced rabbit's eye. The aim of the present work extends also to study the effect of the different liposome formulations on the aqueous humor oxidative stress. Liposome samples were prepared using thin film hydration method. The physiochemical properties of the prepared drugs were characterized. The IOP was recorded for 70 rabbits using Schiotz-tonometer. Malondialdehyde (MDA), reduced glutathione (GSH), catalase (CAT) activities and total antioxidant activity of the aqueous humor were estimated. Fourier transform infrared and differential scanning calorimetric studies confirmed the interaction between the drug and the vesicles, which resulted in high drug encapsulation efficiency ≥88%. The size of the prepared liposomes was less than 10 μm which make them suitable in ophthalmic applications. The sustained effect was achieved by liposome samples of Lip (LAT) and Lip (LAT + TQ) which were able to reduce the IOP significantly up to 84 h. Morever, the treatment of glaucomatous rabbits with liposome formulations containing TQ in their preparation [Lip (TQ) and Lip (LAT + TQ)] greatly improved the ocular tissue-induced histopathological lesions. None of the prepared liposome formulations succeeded to improve the glaucoma-induced oxidative stress damage.

Ultradeformable Liposomes: a Novel Vesicular Carrier For Enhanced Transdermal Delivery of Procyanidins: Effect of Surfactants on the Formation, Stability, and Transdermal Delivery

The aims of this work were to develop a novel vesicular carrier, procyanidins, ultradeformable liposomes (PUDLs), to expand the applications for procyanidins, and increase their stability and transdermal delivery. In this study, we prepared procyanidins ultradeformable liposomes using thin film hydration method and evaluated their encapsulation efficiency, vesicle deformability, storage stability, and skin permeation in vitro. The influence of different surfactants on the properties of PUDLs was also investigated. The results obtained showed that the PUDLs containing Tween 80 had a high entrapment efficiency (80.27 ± 0.99%), a small particle size (140.6 ± 19 nm), high elasticity, and prolonged drug release. Compared with procyanidins solution, the stability of procyanidins in PUDLs improved significantly when stored at 4, 25, and 30°C. The penetration rate of PUDLs was 6.25-fold greater than that of procyanidins solution. Finally, the results of our study suggested that PUDLs could increase the transdermal flux, prolong the release and improve the stability of procyanidins, and could serve as an effective dermal delivery system for procyanidins.

Methotrexate and Cytarabine-Loaded Nanocarriers for Multidrug Cancer Therapy. Spectroscopic Study

Determining the properties of nanoparticles obtained by novel methods and defining the scope of their application as drug carriers has important practical significance. This article presents the pioneering studies concerning high degree incorporation of cytarabine (AraC) and methotrexate (MTX) into liposome vesicles. The main focus of this study were cytarabine-methotrexate-dipalmitoylphosphatidylcholine (DPPC) interactions observed in the gel and fluid phases of DPPC bilayers. The proposed new method of use the Transmittance_2919/2850 ratio presented in our research is sensitive to subtle changes in conformational order resulting from rotations, kinks and bends of the lipid chains. The transition temperatures characterized by Fourier Transform Infrared Spectroscopy (FT-IR) were consistent with the results obtained by Differential Scanning Calorimetry (DSC). Transmission Electron Microscopy (TEM) was used in order to determine the size and shape of the liposomes obtained. The mutual interactions occurring between the drugs studied and the phospholipids were analyzed using the Nuclear Magnetic Resonance (NMR).

The Localization of Phenolic Compounds in Liposomal Bilayers and Their Effects on Surface Characteristics and Colloidal Stability

The interactions with and effects of five chemically distinct, bioactive phenolic compounds on the lipid bilayers of model dipalmitoylphosphatidylcholine (DPPC) liposomes were investigated. Complementary analytical techniques, including differential scanning calorimetry (DSC) and phosphorus and proton nuclear magnetic resonance spectroscopy (NMR), were employed in order to determine the location of the compounds within the bilayer and to correlate location with their effects on bilayer characteristics and liposomal stability. As compared to the phenolic compounds localized in the glycerol region of the DPPC head group within the bilayer, which enhanced the colloidal stability of the liposomes, compounds located closer to the center of the bilayer reduced vesicle stability as a function of time. Molecules present in the upper region of liposomal DPPC acyl chains (C₁-C₁₀) inhibited liposomal aggregation and size increase, perhaps due to tighter packing of adjoining DPPC molecules and increased surface exposure of DPPC phosphate head groups. These data may be useful for designing liposomal systems containing hydrophobic phenols and other small molecules, selecting appropriate analytical methods for determining their location within liposomal bilayers, and predicting their effects on liposome characteristics early in the liposome formulation development process.

Colloidal carriers for extended absorption window of furosemide

Objectives

The aim was to investigate the potential of self-microemulsifying drug delivery systems (SMEDDS) and niosomes as carriers for widening the gastrointestinal absorption window of furosemide (model acidic drug).

Methods

The drug was incorporated in SMEDDS and was encapsulated into niosomes. The intestinal absorption was monitored at two anatomical sites (duodenum and jejuno-ileum). This employed in situ rabbit intestinal perfusion technique.

Key findings

Perfusion of drug solution (control) revealed poor intestinal permeability with per cent fraction absorbed (%Fa) from the duodenum and jejuno-ileum being 1.3 and 0.6 % per cm, respectively. Formulation of furosemide as SMEDDS increased the %Fa from the duodenum and jejuno-ileum to reach 1.7 and 1 % per cm, respectively. Niosomal encapsulation increased the %Fa from duodenum and jejuno-ileum to record 1.9 and 1.2 % per cm, respectively. The increase in the %Fa was also revealed as a reduction in the length required for 95 % absorption of the drug which was reduced from 557.2 to 245.8 cm and to 279.8 cm after delivery as niosomes or SMEDDS, respectively, in case of jejuno-ileum. The same trend was recorded with the duodenum.

Conclusion

The recorded results highlighted the potential for SMEDDS and niosomes for widening the absorption window of acidic drugs after oral administration.

Preformulation Studies of a Liposomal Formulation Containing Sirolimus for the Treatment of Dry Eye Disease

PURPOSE

The aim of this study was to develop and characterize a liposomal product containing sirolimus to be administered subconjunctivally for the treatment of nonresponsive keratoconjunctivitis sicca (KCS) or dry eye.

METHODS

Formulations were prepared using an ethanol injection method and an adaptation of the heating method in pursuance of the most suitable methodology for future industrial production. Liposomes were loaded with either a high dose of 1 mg/mL of sirolimus or a less toxic dose of 0.4 mg/mL. The effects of critical process and formulation parameters were investigated. Liposomes were characterized in terms of size, zeta potential, polydispersity, differential scanning calorimetry, morphology, entrapment efficiency, phospholipid content, thermal stability, and sterility. The formulation was evaluated clinically in dogs with spontaneous KCS.

RESULTS

Sterile liposomal dispersions with sizes ranging from 140 to 211 nm, were successfully obtained. High entrapment efficiency of 93%-98% was achieved. The heating method allowed an easier production of liposomes with high entrapment efficiency, to significantly shorten production time and the elimination of the use of alcohol. The poor stability of the obtained liposomes in aqueous dispersion made the inclusion of a lyophilization step necessary to the manufacturing process. In vivo testing of the liposomal sirolimus formulations in the spontaneous KCS dog model have produced promising results, particularly with a sirolimus dose of 1 mg/mL, indicating the need for further development and study of proposed formulations in the treatment of canine KCS. Clinical improvement in tear production in dogs with spontaneous KCS treated with the 1 mg/mL dose product was observed.

CONCLUSIONS

The heating method allowed easier production of high entrapment efficiency liposomes to significantly shorten production time and the elimination of the use of alcohol. Tear production was increased in dogs administered with the formulation.

Solid lipid nanoparticles of clotrimazole silver complex: An efficient nano antibacterial against Staphylococcus aureus and MRSA

New and effective strategies to transform current antimicrobials are required to address the increasing issue of microbial resistance and declining introduction of new antibiotic drugs. In this context, metal complexes of known drugs and nano delivery systems for antibiotics are proving to be promising strategies. The aim of the study was therefore to synthesize a silver complex of clotrimazole and formulate it into a nano delivery system for enhanced and sustained antibacterial activity against susceptible and resistant Staphylococcus aureus. A silver complex of clotrimazole was synthesized, characterized and further encapsulated into solid lipid nanoparticles to evaluate its antibacterial activity against S. aureus and methicillin-resistant S. aureus (MRSA). An in vitro cytotoxicity study was performed on HepG2 cell lines to assess the overall biosafety of the synthesized clotrimazole silver complex to mammalian cells, and was found to be non-toxic to mammalian cells (cell viability >80%). The minimum inhibitory concentrations (MIC) of clotrimazole and clotrimazole-silver were 31.25 and 9.76 μg/mL against S. aureus, and 31.25 and 15.62 against MRSA, respectively. Clotrimazole SLNs exhibited MIC values of 104 and 208 μg/mL against both MSSA and MRSA at the end of 18 and 36 h, respectively, but thereafter completely lost its antibacterial activity. Clotrimazole-silver SLNs had an MIC value of 52 μg/mL up to 54 h, after which the MIC value was 104 μg/mL against both strains at the end of 72 h. Thus, clotrimazole-silver SLNs was found to be an efficient nanoantibiotic.