The effect of monomers and of micellar and vesicular forms of non-ionic surfactants (Solulan C24 and Solulan 16) on Caco-2 cell monolayers

Niosomes: A Smart Drug Delivery System for Brain Targeting

Niosomes are lipid-based nanovesicles that have the potential to act as drug-delivery vehicles for a variety of agents. They are effective drug delivery systems for both ASOs and AAV vectors, with advantages such as improved stability, bioavailability, and targeted administration. In the context of brain-targeted drug delivery, niosomes have been investigated as a drug delivery system for brain targeting, but more research is needed to optimize their formulation to improve their stability and release profile and address the challenges of scale-up and commercialization. Despite these challenges, several applications of niosomes have demonstrated the potential of novel nanocarriers for targeted drug delivery to the brain. This review briefly overviews the current use of niosomes in treating brain disorders and diseases.

A novel niosome formulation for encapsulation of anthocyanins and modelling intestinal transport

The bioavailability of drugs can be improved by regulating the structural properties, particularly lipoid systems, such as niosomes, can increase cellular uptake. Herein, we optimized double emulsion and niosomal formulations for encapsulating anthocyanin-rich black carrot extract. Nanoparticles obtained by selected formulation were characterized in terms of morphology, particle size, drug encapsulation efficiency, in vitro release and cytotoxicity. The optimum conditions for niosomal formulation were elicited as 30 mg of cholesterol, 150 mg of Tween 20 and feeding time of 1 min at a stirring rate of 900 rpm yielding the lowest average particle size of 130 nm. In vitro release data showed the majority of the encapsulated anthocyanins were released at the end of 10 h. A mathematical model was developed to estimate the absorption of anthocyanins released from niosomes and cytotoxicity was assessed against neuroblastoma. Overall, these findings suggest that niosomal vesicles might be suitable delivery systems for anthocyanins.

Porous Inorganic Drug Delivery Systems-a Review

Innovative methods and materials have been developed to overcome limitations associated with current drug delivery systems. Significant developments have led to the use of a variety of materials (as excipients) such as inorganic and metallic structures, marking a transition from conventional polymers. Inorganic materials, especially those possessing significant porosity, are emerging as good candidates for the delivery of a range of drugs (antibiotics, anticancer and anti-inflammatories), providing several advantages in formulation and engineering (encapsulation of drug in amorphous form, controlled delivery and improved targeting). This review focuses on key selected developments in porous drug delivery systems. The review provides a short broad overview of porous polymeric materials for drug delivery before focusing on porous inorganic materials (e.g. Santa Barbara Amorphous (SBA) and Mobil Composition of Matter (MCM)) and their utilisation in drug dosage form development. Methods for their preparation and drug loading thereafter are detailed. Several examples of porous inorganic materials, drugs used and outcomes are discussed providing the reader with an understanding of advances in the field and realistic opportunities.

Cytotoxicity and genotoxicity of lipid nanocapsules

Lipid nanocapsules (LNCs) offer a promising method for the entrapment and nanovectorisation of lipophilic molecules. This new type of nanocarrier, formulated according to a solvent-free process and using only regulatory-approved components, exhibits many prerequisites for being well tolerated. Although toxicological reference values have already been obtained in mice, interaction of LNCs at the cell level needs to be elucidated. LNCs, measuring from 27.0±0.1nm (25nm LNCs) and 112.1±1.8nm (100nm LNCs) and with a zeta potential between -38.7±1.2mV and +9.18±0.4mV, were obtained by a phase inversion process followed by post-insertion of carboxy- or amino-DSPE-PEG. Trypan blue, MTS and neutral red uptake (NRU) assays were performed to evaluate the cytotoxicity of LNCs on mouse macrophage-like cells RAW264.7 after 24h of exposure. The determination of 50% lethal concentration (LC50) showed a size effect of LNCs on toxicity profiles: LC50 ranged from 1.036mg/L (MTS) and 0.477mg/mL (NRU) for 25nm LNCs, to 4.42mg/mL (MTS) and 2.18mg/mL (NRU) for 100nm LNCs. Surfactant Solutol® HS15 has been shown to be the only constituent to exhibit cytotoxicity; its LC50 reached 0.427mg/mL. Moreover, LNCs were not more toxic than their components in simple mixtures. At sublethal concentration, 100nm LNCs only were able to induce a significant production of nitric oxide (NO) by RAW264.7 cells, as assessed by the Griess reaction. Again, surfactant was the only component responsible for an increased NO release (1.8±0.2-fold). Genotoxicity assays revealed no DNA damage on human lymphocytes in both the in vitro Comet and micronucleus assays using 4-hour and 24-hour treatments, respectively.

Colloidal drug formulations can explain "bell-shaped" concentration-response curves

Drug efficacy does not always increase sigmoidally with concentration, which has puzzled the community for decades. Unlike standard sigmoidal curves, bell-shaped concentration-response curves suggest more complex biological effects, such as multiple-binding sites or multiple targets. Here, we investigate a physical property-based mechanism for bell-shaped curves. Beginning with the observation that some drugs form colloidal aggregates at relevant concentrations, we determined concentration-response curves for three aggregating anticancer drugs, formulated both as colloids and as free monomer. Colloidal formulations exhibited bell-shaped curves, losing activity at higher concentrations, while monomeric formulations gave typical sigmoidal curves, sustaining a plateau of maximum activity. Inverting the question, we next asked if molecules with bell-shaped curves, reported in the literature, form colloidal aggregates at relevant concentrations. We selected 12 molecules reported to have bell-shaped concentration-response curves and found that five of these formed colloids. To understand the mechanism behind the loss of activity at concentrations where colloids are present, we investigated the diffusion of colloid-forming dye Evans blue into cells. We found that colloidal species are excluded from cells, which may explain the mechanism behind toxicological screens that use Evans blue, Trypan blue, and related dyes.

Enhanced oral absorption of hydrophobic and hydrophilic drugs using quaternary ammonium palmitoyl glycol chitosan nanoparticles

As 95% of all prescriptions are for orally administered drugs, the issue of oral absorption is central to the development of pharmaceuticals. Oral absorption is limited by a high molecular weight (>500 Da), a high log P value (>2.0) and low gastrointestinal permeability. We have designed a triple action nanomedicine from a chitosan amphiphile: quaternary ammonium palmitoyl glycol chitosan (GCPQ), which significantly enhances the oral absorption of hydrophobic drugs (e.g., griseofulvin and cyclosporin A) and, to a lesser extent, the absorption of hydrophilic drugs (e.g., ranitidine). The griseofulvin and cyclosporin A C(max) was increased 6- and 5-fold respectively with this new nanomedicine. Hydrophobic drug absorption is facilitated by the nanomedicine: (a) increasing the dissolution rate of hydrophobic molecules, (b) adhering to and penetrating the mucus layer and thus enabling intimate contact between the drug and the gastrointestinal epithelium absorptive cells, and (c) enhancing the transcellular transport of hydrophobic compounds. Although the C(max) of ranitidine was enhanced by 80% with the nanomedicine, there was no appreciable opening of tight junctions by the polymer particles.

Polyamine aza-cyclic compounds demonstrate anti-proliferative activity in vitro but fail to control tumour growth in vivo

Cationic polyamines such as the poly(propylenimine) dendrimers (DAB16) are anti-tumour agents (Dufes et al., 2005, Cancer Res 65:8079-8084). Their mechanism of action is poorly understood, but the lack of in vivo toxicity suggests cancer specificity. To explore this polyamine pharmacophore we cross-linked the aza-cyclic compound, hexacyclen, with 1,4-dibromobutane or 1,8-dibromooctane to yield the polyamines [poly(butylhexacyclen)--CL4] or [poly(octylhexacyclen)--CL8] respectively, both free of primary amines. We characterised the compounds and their respective nanoparticles and examined their interaction with the putative targets of the cationic polyamines: the cell membrane and DNA. Like DAB 16, CL4 and CL8 bind plasmid DNA and all three compounds interrupted the cell cycle of A431 epidermoid carcinoma cells in the S-phase. Additionally all three compounds disrupted erythrocyte membranes, with CL8 and DAB 16 being more active, in this respect, than CL4. CL4 (IC(50) =775.1 µg mL(-1)) and CL8 (IC(50) =8.4 µg mL(-1)), in a similar manner to DAB 16, were anti-proliferative against A431 cells; although unlike DAB 16, CL4 and CL8 were not tumouricidal against A431 xenografts in mice, indicating that primary amines may play an important role in the in vivo activity of DAB 16.

Preparation and Characterization of Propylthiouracil Niosomes

Propylthiouracil, a lyophobic drug with an antiproliferative activity, was formulated into niosomes using various classes of nonionic surfactants. Feasibility of vesicle formation by the sonication method was evaluated. Size and size distribution was measured by laser diffraction. Entrapment and drug release over 24 h were monitored by UV spectrophotometric method at 275 nm. The results revealed that niosomes readily formed from various compositions of nonionic surfactant and cholesterol, with or without a stabilizer. Entrapment of PTU in niosomes depended on bilayer composition. The release of PTU from all niosomal formulations studied was retarded and followed the first-order kinetics. Degree of slow release had a negative correlation with drug entrapment. The release rate also depended on the physical state of the bilayer. The results of this study indicate that PTU niosomes were able to control the release of PTU and might be of value to develop further into topical formulations.

Effect of charged and non-ionic membrane additives on physicochemical properties and stability of niosomes

The aim of this study was to investigate an influence of different types of membrane additives including negative charge (dicetylphosphate, DCP), positive charge (stearylamine, STR) and non-ionic molecule (cholesteryl poly-24-oxyethylene ether, SC24) on the physicochemical properties of drug-free and drug-loaded niosomes. Salicylic acid having different proportions of ionized and unionized species at different pH was selected as a model drug. The niosomes were composed of 1:1 mole ratio of Span 60: cholesterol as vesicle forming agents. The results show that incorporation of salicylic acid to the niosomes did not affect zeta potential values; however, addition of the membrane additives changed the zeta potential depending on the type of the additives. Transmission electron microscopy revealed that niosomes had unilamellar structure. The particle sizes of all developed niosomes were between 217 to 360 nm. The entrapment efficiency (%E.E.) of all salicylic acid niosomes at pH 3 was higher than that of niosomes at pH 5, indicating that salicylic acid in unionized form was preferably incorporated in niosomes. Furthermore, the positively charged niosomes showed the highest %E.E. of salicylic acid owing to electrostatic attraction between STR and salicylic acid. After 3 months of storage at 4 degrees C, the particle size of the niosomes remained in the nanosize range except for DCP salicylic acid niosomes at pH 3 whose size increased due to an instability of DCP at low pH. In addition, all niosomes showed no leakage of the salicylic acid after 3 months of storage indicating the good stability.

Enhanced transport of a novel anti-HIV agent--cosalane and its congeners across human intestinal epithelial (Caco-2) cell monolayers

PURPOSE

Cosalane is a potent inhibitor of HIV replication with activity against a broad range of viral targets. However, oral bioavailability of this highly lipophilic compound is extremely poor (<1%). The purpose of this study is to screen a variety of permeation enhancers (cyclodextrin derivatives, cremophor EL, bile salts and mixed micelles) for their ability to enhance the transport of cosalane and its analogs/prodrugs across Caco-2 cell monolayers.

METHODS

Cosalane and its different analogs/prodrugs were synthesized and their physicochemical properties were determined. Caco-2 cells were cultured at a density of 66,000 cells/cm(2) either on collagen coated clear polyester membranes or Transwell inserts. Side-bi-side diffusion cells and Transwell inserts were employed to study for the transport of cosalane and its analogs/prodrugs with various permeation enhancers across Caco-2 cell monolayers.

RESULTS

Permeabilities of EH-3-39, EH-3-55 and EH-3-57 significantly improved compared to that of cosalane in the presence of bile salt, sodium desoxycholate. Among the various cyclodextrins studied, hydroxypropyl beta cyclodextrin (HP-beta-CD) and dimethyl beta cyclodextrin (DM-beta-CD) exhibited 22.3-fold and 19-fold permeability enhancement of cosalane respectively across Caco-2 cell monolayers. Sodium desoxycholate (10 mM) also showed a remarkable (105-fold) enhancement on the permeability of cosalane (P(app) 11.72+/-3.31 x 10(-6) cm/s) without causing any measurable cellular damage. Cremophor EL resulted in higher transport of 14C mannitol. The mechanism of enhancement effect can be mainly attributed to the alteration of membrane fluidity by cyclodextrin and opening of tight junctions by cremophor EL.

CONCLUSIONS

Among the enhancers tested, 10 mM sodium desoxycholate and HP-beta-CD appear to be viable candidates for further development of an oral formulation of cosalane and its congeners.

Charge-dependent interaction of self-emulsifying oil formulations with Caco-2 cells monolayers: binding, effects on barrier function and cytotoxicity

A positively charged self-emulsifying oil formulation (SEOF), aimed to enhance oral bioavailability of drugs poorly soluble in water, was recently developed. In the present study the Caco-2 cell model was used for the investigation of the charge-dependent interactions of this SEOF with human intestinal epithelial cells. The positively charged emulsions affected the barrier properties of the cell monolayer at high concentrations and reduced the cell viability. However, at the dilution with aqueous phase used in the present study (1:2000), the positively charged SEOF did not induce any detectable cytotoxic effect. The binding of the fluorescent dye DiIC(18)(3) was much higher from the positively charged SEOF, compared to the negatively charged formulation, suggesting an increased closer adhesion of the droplets to the cell surface due to the electrostatic attraction. No transepithelial transport of this compound across Caco-2 cell monolayers was observed with any SEOF formulation.

Mechanistic studies on surfactant-induced membrane permeability enhancement

PURPOSE

To gain some mechanistic understanding of surfactant-induced membrane permeabilization and identify a surfactant physical property that can be used as a predictor for intestinal membrane permeability enhancement.

METHODS

The maximum surface pressures (piCMC) of series of anionic and non-ionic surfactants as indicators of surface activity were determined using a bubble surface tensiometer, and related to in vivo intestinal membrane permeability and acute damage data of the same surfactants from a previous work. Phospholipid bilayers with constant surface pressures and monolayers with different surface pressures were used as model membranes to systematically study membrane permeability enhancement and membrane penetration of surfactants at different concentrations.

RESULTS

Surfactants that did not permeabilize or acutely damage the intestinal wall generally exhibited a piCMC < 25 dyne/cm. Permeability enhancement and acute damage increased as piCMC increased beyond 25 dyne/cm. This critical threshold value at around 25 dynes/cm was also observed with in vitro experiments using phospholipid vesicles and monolayers. Data support the hypothesis that the threshold phenomenon originates from the interfacial tension at the membrane/water interface, which controls the surface adsorption process of surfactant molecules onto the membrane.

CONCLUSIONS

For a surfactant to permeabilize and acutely damage the intestinal wall, it must exhibit a surface pressure of greater than 25 dynes/cm. This threshold value is related to an intrinsic property, surface pressure, of the phospholipid membranes. Since the surfactant surface pressure is a property of the surfactant monomer, partition of the surfactant monomer, not the micelle, into the membrane is an obligate step in membrane permeabilization. Above the surfactant critical micelle concentration, CMC, micelles may act as a depot to continuously replace aqueous surfactant monomers taken up by the membrane. For some surfactants above CMC, sufficient number of monomers can partition into the membrane to cause solubilization of membrane lipids in surfactant micelles.