Cécile Poirier

Drug solubilization and in vitro toxicity evaluation of lipoamino acid surfactants

To improve solubilization of a water insoluble anticancer drug, novel surfactants were synthesized. All surfactants derived from lysine, with a so-called nitrilo triacetic acid (NTA) polar head, and differed from the length and saturation degree of their hydrophobic moieties: C19:0-NTA, C20:4-NTA, C25:0-NTA and C25:4-NTA. Self-assembling properties and critical micellar concentration (CMC) values were determined using pyrene fluorescence and cytotoxicity using MTT and LDH assays on endothelial cells. Surfactant haemolytic activity and drug solubilization capacity were also evaluated. All surfactants self-assemble with low CMC values from 0.012 to 0.430 mg/mL. Cytotoxicity assays showed that C20:4-NTA and C25:0-NTA were less cytotoxic than polysorbate 80. Unsaturations and alkane chain length have a marked influence on toxicity. Saturated surfactants had a similar haemolytic activity, explained by their low CMC values and the linear configuration of their hydrophobic tail. C20:4-NTA and C25:4-NTA were less haemolytic than polysorbate 80. Furthermore, C19:0-NTA, C25:0-NTA and C25:4-NTA increased drug solubility from <0.15 μg/mL up to 7 mg/mL, with 46% (w/w) drug loading, due to their linear and flexible hydrophobic chain configuration, as evidenced by molecular modelling. Although these solubilizers are promising, a compromise between drug solubilization and toxicity remains to be found.

Performance of magnetic chitosan–alginate core–shell beads for increasing the bioavailability of a low permeable drug

This work reports the synthesis and performance of magnetic chitosan-alginate core-shell beads for oral administration of small molecules in order to increase their bioavailability. For this purpose, we designed magnetic core-shell beads suitable for oral delivery that are resistant in acidic media (stomach pH), mucoadhesive, exhibit a superparamagnetic behavior and a very high entrapment efficiency. Ex vivo experiments were performed in Ussing chambers, to emphasize the effect of magnetic accumulation. The amount of drug permeated through the membrane exhibited a threefold increase with our novel drug delivery system. According to a correlation law, our ex vivo model showed that the adsorbed fraction (FA) in human is expected to reach 70% when using the magnetic retention system which is a great improvement when compared to the controls (FA=20%).

Physicochemical characterization and toxicity evaluation of steroid-based surfactants designed for solubilization of poorly soluble drugs

To overcome poor water-solubility of new drug candidates, four innovative surfactants based on naturally-occuring hydrophilic and hydrophobic moities were designed and synthesized: cholesteryl-glutamic acid, cholesteryl-poly[N-2-hydroxyethyl-l-glutamine] (PHEG), ursodeoxycholanyl-PHEG (UDCA-PHEG) and ursodeoxycholanyl-poly-l-glutamic acid (UDCA-PGA). Their self-assembling capacity was evaluated using pyrene fluorescence measurements which allow to determine their critical aggregation concentration (CAC). Size measurements were carried out using dynamic light scattering (DLS). Surfactant cytotoxicity was investigated on human umbilical vein endothelial cells (HUVEC) by determining tetrazolium salt (MTT) activity and lactate dehydrogenase (LDH) release. In addition, surfactant haemolytic activity was assessed using rat red blood cells (RBCs). Finally, the ability of these surfactants to solubilize a model poorly soluble drug was quantified. Surfactant self-assembly, cytotoxicity and solubilization properties were compared to those obtained with polysorbate 80, a model solubilizer. Except for cholesteryl-glutamic acid, surfactants were water-soluble. UDCA-PGA was not able to self-assemble or to increase significantly drug solubility. Results showed that cholesteryl-PHEG and UDCA-PHEG were self-assembling with low CAC values (17 and 120μg/ml) into nano-structures with mean diameters of 13 and 250nm, respectively. Cholesteryl-PHEG was the most efficient surfactant in increasing drug solubility (2mg/ml) but exhibited a similar or higher toxicity than polysorbate 80. UDCA-PHEG did not present any cytotoxicity but was far less efficient to solubilize the drug (0.2mg/ml). These results evidence interesting properties of cholesteryl-PHEG and UDCA-PHEG as novel solubilizers.

Optimization of magnetic retention in the gastrointestinal tract: Enhanced bioavailability of poorly permeable drug

&NA; Oral administration of low permeable drugs remains a challenge as they do not cross biological membrane efficiently and therefore exhibit a poor bioavailability. Herein, the effect of magnetic retention on the circulation and bioavailability of magnetic beads in the gastrointestinal tract in the presence of an external magnetic field is evaluated. Retention efficiency is imaged using magnetic resonance and near infrared techniques. The effect on bioavailability is then evaluated in a pharmacokinetic study. Iron oxide nanoparticles, the drug (dipeptidyl peptidase‐IV inhibitor) and a fluorophore (Alexa Fluor‐750) are co‐encapsulated in chitosan‐alginate core‐shell beads. Retention of these beads is induced by the presence of an external permanent magnet on the abdomen of rats. After single administration of magnetic beads containing 20 mg/kg of drug to fasted rats, a 2.5‐fold increase in drugs bioavailability is observed in the presence of an external magnetic field, significantly higher than the same dose administered to rats without the field or for the drug in aqueous solution. Retention of the magnetic carriers in the presence of an external magnet proves to accumulate these carriers in a specific localization of the intestine leading to a significant improve in the drugs bioavailability. Graphical abstract Magnetic retention of core‐shell chitosan‐alginate beads containing iron oxide nanoparticles is investigated for bioavailability improvement of a low permeable drug. The efficiency of magnetic retention in the intestine is observed by Magnetic Resonance and Near Infra‐red imaging. The impact on drugs bioavailability as well as the toxicity of these magnetic carriers is then studied in vivo in the gastro intestinal tract. Figure. No caption available.