Liposomes — microscopic phospholipid bubbles with a bilayered membrane structure — have received a lot of attention during the past 30 years as pharmaceutical carriers of great potential. More recently, many new developments have been seen in the area of liposomal drugs — from clinically approved products to new experimental applications, with gene delivery and cancer therapy still being the principal areas of interest. For further successful development of this field, promising trends must be identified and exploited, albeit with a clear understanding of the limitations of these approaches.

Recent advances with liposomes as pharmaceutical carriers.

Transepithelial/transendothelial electrical resistance (TEER) is a widely accepted quantitative technique to measure the integrity of tight junction dynamics in cell culture models of endothelial and epithelial monolayers. TEER values are strong indicators of the integrity of the cellular barriers before they are evaluated for transport of drugs or chemicals. TEER measurements can be performed in real time without cell damage and generally are based on measuring ohmic resistance or measuring impedance across a wide spectrum of frequencies. The measurements for various cell types have been reported with commercially available measurement systems and also with custom-built microfluidic implementations. Some of the barrier models that have been widely characterized using TEER include the blood–brain barrier (BBB), gastrointestinal (GI) tract, and pulmonary models. Variations in these values can arise due to factors such as temperature, medium formulation, and passage number of cells. The aim of this article ...

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TEER Measurement Techniques for In Vitro Barrier Model Systems

Poloxamer 407 copolymer (ethylene oxide and propylene oxide blocks) shows thermoreversible properties, which is of the utmost interest in optimising drug formulation (fluid state at room temperature facilitating administration and gel state above sol-gel transition temperature at body temperature promoting prolonged release of pharmacological agents). Pharmaceutical evaluation consists in determining the rheological behaviour (flow curve or oscillatory studies), sol-gel transition temperature, in vitro drug release using either synthetic or physiological membrane and (bio)adhesion characteristics. Poloxamer 407 formulations led to enhanced solubilisation of poorly water-soluble drugs and prolonged release profile for many galenic applications (e.g., oral, rectal, topical, ophthalmic, nasal and injectable preparations) but did not clearly show any relevant advantages when used alone. Combination with other excipients like Poloxamer 188 or mucoadhesive polymers promotes Poloxamer 407 action by optimising sol-gel transition temperature or increasing bioadhesive properties. Inclusion of liposomes or micro(nano)particles in Poloxamer 407 formulations offers interesting prospects, as well. Besides these promising data, Poloxamer 407 has been held responsible for lipidic profile alteration and possible renal toxicity, which compromises its development for parenteral applications. In addition, new findings have demonstrated immuno-modulation and cytotoxicity-promoting properties of Poloxamer 407 revealing significant pharmacological interest and, hence, human trials are in progress to specify these potential applications.

A Review of Poloxamer 407 Pharmaceutical and Pharmacological Characteristics

動注化学療法における pharmacokinetics と臨床

https://uhra.herts.ac.uk/bitstream/handle/2299/15972/Microencapsulation_of_Probiotics_For_Gastrointestinal_Delivery_.pdf?sequence=2

Microencapsulation of probiotics for gastrointestinal delivery.

http://pharmaquest.weebly.com/uploads/9/9/4/2/9942916/cntrl_jrnl1.pdf

Administration of resveratrol: What formulation solutions to bioavailability limitations?

https://www.hal.inserm.fr/inserm-00924338/document

Citrulline: From metabolism to therapeutic use

Purpose
Although probiotics are of a major potential therapeutic interest, their efficacy is usually limited by poor bioavailability of viable microorganisms on site. The aim of this study was to protect the probiotic Saccharomyces boulardii from degradation in order to ensure a greater number of viable yeast in the colon.

Increased intestinal delivery of viable Saccharomyces boulardii by encapsulation in microspheres.

The rheological behavior of a poloxamer 20% thermoreversible gel with morphine or without was studied. Its behavior was newtonian below the transition temperature and became non newtonian above this temperature. The non newtonian part was best fitted with the Herschel-Bulkley equation in comparison with the Casson equation. The sol-gel transition was associated with a drastic increment of the apparent viscosity and a brutal modification of the Herschel-Bulkley equation parameters. Likewise, the oscillatory parameters (the lag phase, the storage modulus and the loss modulus) revealed the great influence of the temperature on the viscoelastic properties of the sample. Different rheological methods have been described in order to determine the transition temperature usable for the control of preparations. The temperature interval corresponding to the sol-gel transition ranged between 22-25°C for the solution with morphine and between 23-26°C for the solution without. Thereby, the addition of morphine...

Rheological study of a thermoreversible morphine gel

Objectives: The purpose of the study was to gel a rectal solution of short-chain fatty acids to decrease the loss of active materials in the colonic lumen and thereby optimize their absorption. Methods: Five thermogels were prepared with poloxamer 407 at concentrations ranging from 17% to 20%. Their viscosities were measured at room temperature and 37°C, and their gelling temperatures were determined. The adhesive properties of each gel were assessed in vitro at 37°C. Short-chain fatty acid release was studied using Guyot cells. Results: From the threshold concentration of 17.5%, the solutions, Newtonian at room temperature (50–80 mPa · s), gelled at 37°C. The higher the concentration, the higher the viscosity (1750 to 49,000 mPa · s), the lower the gelling temperature (27.6°C to 23.4°C), and the stronger the work of adhesion (2.2 to 4.5 mJ). Short-chain fatty acid release from the 18% polymer gel was decreased by 60% compared to the rectal solution. Conclusion: The 18% poloxamer 407 concentration provide...

Jean-Claude Chaumeil

Papers

Administration of resveratrol: What formulation solutions to bioavailability limitations?

Citrulline: From metabolism to therapeutic use

Increased intestinal delivery of viable Saccharomyces boulardii by encapsulation in microspheres.

Rheological study of a thermoreversible morphine gel

Poloxamer 407 as a thermogelling and adhesive polymer for rectal administration of short-chain fatty acids.