W/O/W multiple emulsions of insulin containing a protease inhibitor and an absorption enhancer: preparation, characterization and determination of stability towards proteases in vitro

Innovative multiple nanoemulsion (W/O/W) based on Chilean honeybee pollen improves their permeability, antioxidant and antibacterial activity

Beehive derivatives, including honeybee pollen (HBP), have been extensively studied for their beneficial health properties and potential therapeutic use. Its high polyphenol content gives it excellent antioxidant and antibacterial properties. Today its use is limited due to poor organoleptic properties, low solubility, stability, and permeability under physiological conditions. A novel edible multiple W/O/W nanoemulsion (BP-MNE) to encapsulate the HBP extract was designed and optimized to overcome these limitations. The new BP-MNE has a small size (∼100 nm), a zeta potential greater than +30 mV, and efficiently encapsulated phenolic compounds (∼82%). BP-MNE stability was measured under simulated physiological conditions and storage conditions (4 months); in both cases, stability was promoted. The formulation's antioxidant and antibacterial (Streptococcus pyogenes) activity was analyzed, obtaining a higher effect than the non-encapsulated compounds in both cases. In vitro permeability was tested, observing a high permeability of the phenolic compounds when they are nanoencapsulated. With these results, we propose our BP-MNE as an innovative solution to encapsulate complex matrices, such as HBP extract, as a platform to develop functional foods.

Intestinal permeation enhancers for oral peptide delivery

Intestinal permeation enhancers (PEs) are one of the most widely tested strategies to improve oral delivery of therapeutic peptides. This article assesses the intestinal permeation enhancement action of over 250 PEs that have been tested in intestinal delivery models. In depth analysis of pre-clinical data is presented for PEs as components of proprietary delivery systems that have progressed to clinical trials. Given the importance of co-presentation of sufficiently high concentrations of PE and peptide at the small intestinal epithelium, there is an emphasis on studies where PEs have been formulated with poorly permeable molecules in solid dosage forms and lipoidal dispersions.

Nanomaterials, Autophagy, and Lupus Disease

Nanoscale materials hold great promise in the therapeutic field. In particular, as carriers or vectors, they help bioactive molecules reach their primary targets. Furthermore, by themselves, certain nanomaterials-regarded as protective-can modulate particular metabolic pathways that are deregulated in pathological situations. They can also synergistically improve the effects of a payload drug. These properties are the basis of their appeal. However, nanoscale materials can also have intrinsic properties that limit their use, and this is the case for certain types of nanomaterials that influence autophagy. This property can be beneficial in some pathological settings, but in others, if the autophagic flux is already accelerated, it can be deleterious. This is notably the case for systemic lupus erythematosus (SLE) and other chronic inflammatory diseases, including certain neurological diseases. The nanomaterial-autophagy interaction therefore must be treated with caution for therapeutic molecules and peptides that require vectorization for their administration.

Infrared laser triggered release of bioactive compounds from single hard shell microcapsules

Thermal microscopy combines laser-induced heating and real time imaging. Temperature jumps release bioactive compounds from temperature sensitive single microcapsules.

Structural stability of green fluorescent proteins entrapped in polyelectrolyte nanocapsules

Molecules of a green fluorescent protein mutant, GFPmut2, have been immobilized in nanocapsules, assemblies of charged polyelectrolyte multilayers, with the aim to study the effect of protein-polyelectrolyte interactions on the protein stability against chemical denaturation. GFPmut2 proteins turn out to be stabilized and protected against the denaturating action of small chemical compounds. The nanocapsule protective effect on GFPmut2 is likely due to protein interactions with the negatively charged polymers, that induce an increase in the local rigidity of the protein nano-environment. This suggestion is supported by Fluorescence Polarization measurements on GFPmut2 proteins bound to the NC layers.

In vitro and in vivo evaluation of a novel oral insulin formulation

AIM

To develop a stable self-emulsifying formulation for oral delivery of insulin.

METHODS

Caco-2 cell line and diabetic beagles were used as in vitro and in vivo models to study the absorption mechanism and the hypoglycemic efficacy of the formulation. In addition, various physicochemical parameters of the formulation such as droplet size, insulin encapsulation efficiency and stability were evaluated.

RESULTS

This formulation enabled changes in barrier properties of Caco-2 monolayers, as referred by transepithelial electrical resistance (TEER) and apparent permeability coefficients (P(app)) of the paracellular marker ranitidine (20-fold greater than control) but not transcellular marker propranolol, suggesting that the opening of tight junctions was involved. In diabetic beagle dogs, the bioavailability of this formulation was up to 15.2% at a dose of 2.5 IU/kg in comparison with the hypoglycemic effect of native insulin (0.5 IU/kg) delivered by subcutaneous injection.

CONCLUSION

This formulation, recently approved by the China State Food and Drug Administration to enter clinical trials, was stable, degradation-protected and absorption-enhanced, and provided a promising formulation for oral insulin delivery.

Release of antiseptics from the aqueous compartments of a w/o/w multiple emulsion

A w/o/w multiple emulsion drug carrier system has been developed for local vaginal therapy. To improve its efficacy and to extend the antimicrobial spectrum activity of benzalkonium chloride (CBZ), which is introduced in the external aqueous phase, chlorhexidine digluconate (CHD) was added to the internal aqueous phase of the multiple emulsions. The minimal bactericidal concentrations (MBC) for the association of CHD and CBZ in emulsion were determined towards Escherichia coli and Staphylococcus aureus. The main release mechanism considered for the CHD encapsulated in the inner phase was a swelling-breakdown phenomenon which followed dilution of the emulsion under hypo-osmotic conditions. In order to demonstrate this release, the bactericidal effect of multiple emulsions undiluted and diluted 1-5 and 1-10 in hypo-osmotic conditions at two CHD concentrations was evaluated. To validate and quantify this release, rheological and release kinetics studies were used. The bactericidal activity of combination CBZ-CHD in the emulsion was synergistic on the two bacterial strains and the release of encapsulated CHD in the internal phase was obtained following its dilution in hypo-osmotic conditions. Vaginal administration could be carried out following dilution at 1-5 in sterile water for multiple emulsions containing the lower concentration of CHD.

Complex dispersions of multilamellar vesicles: a promising new carrier for controlled release and protection of encapsulated molecules

Multilamellar vesicles called Spherulites have recently been discovered and are being developed for encapsulation applications. In this study, we present new systems of Spherulites called complex dispersions. These are prepared by dispersing Spherulites within an oily medium, and then emulsifying this oily dispersion of Spherulites within an aqueous solvent. The ability of complex dispersions to reduce the release of encapsulated ions under variable osmotic dilutions was evaluated and compared with Spherulites directly dispersible in an aqueous medium, and with multiple emulsions. An advantage of complex dispersions over Spherulites is to present an additional oily barrier. Indeed, this barrier retarded the release of encapsulated ions. Complex dispersions also proved to be less sensitive to osmotic pressure than multiple emulsions. It appeared that the dilution of a complex dispersion formulated with no external aqueous phase containing a hydrophilic surfactant provided the slowest release of encapsulated ions. Furthermore, this formulation maintained a difference of pH between the internal and external aqueous phases for a few hours. In conclusion, these new systems of Spherulites known as complex dispersions show great potential for pharmaceutical applications such as controlled release and protection of encapsulated substances.

pH compartmented w/o/w multiple emulsion: a diffusion study

In order to develop w/o/w emulsions characterized by two separate aqueous phases of different pH, a preliminary study was carried out to obtain a better insight into the possible diffusion processes taking place between an inner acidic aqueous phase and an external phase of higher pH (pH approximately 6). In fact, such systems could be of great interest for pharmaceutical use. For this purpose, a model emulsion was formulated. The study of pH and conductivity showed that acidic species transport take place between the two aqueous compartments. The three main release mechanisms that might be responsible for this passage across the oil phase were investigated: breakdown of oil globules, facilitated transport by surfactant micelles across the oil phase or by Fickian diffusion. It appears that this last mechanism was involved. In order to control this diffusion process, an alkaline species, octadecylamine was introduced in the oil phase. This compound could form an ion pair with the lactate ion at the interface of the external aqueous phase and the oil phase, thus, limiting the acidification of the external aqueous phase.

Oral delivery of synthetic eel calcitonin, elcatonin, in rats

This study was designed to develop an oral dosage form of elcatonin (EC), a hypocalcemic peptide. The EC absorption was estimated by the reduction in plasma calcium concentrations. When EC was orally coadministered with nitroso-N-acetyl-D,L-penicillamine (SNAP, 4.0 mg) and 0.02% Carbopol solution or with taurocholate (20 mM) and 0.02% Carbopol solution, the lowering effect was increased compared with that after EC alone, but the F values (0.32 and 0.30%) were extremely small. The oral administration of the mucoadhesive emulsion, which was prepared by coating the W/O/W emulsion with 0.1% Carbopol, enhanced the calcium lowering effect, with the F value of 0.43%. The strong mucoadhesion of the mucoadhesive emulsion to the gastrointestinal mucosa was observed. A capsule containing EC (500 microg), taurocholate (6 mg) and lyophilized Carbopol (3.5 mg) administered orally gave a sustained but comparatively small calcium lowering effect. In the in vitro enzymatic hydrolysis experiment, EC was more rapidly hydrolyzed in the intestinal fluid than in the mucosal extract. The combination of 20 mM taurocholate with 0.02% Carbopol showed the greatest inhibitory effect in both fluid and extract. These data indicated that EC was effectively absorbed through the intestinal wall, but the peptide was dominantly degraded by proteolytic enzymes in the GI tract. These results will offer a potential approach to the oral delivery of EC.

Basic study for stabilization of w/o/w emulsion and its application to transcatheter arterial embolization therapy

Stabilization of w/o/w emulsion and its application to transcatheter arterial embolization (TAE) therapy are reviewed. W/o/w emulsion was stabilized by making inner aqueous phase hypertonic, addition of chitosan in inner phase, and techniques of phase-inversion with porous membrane. Lipiodol w/o/w emulsion for TAE therapy was prepared by using a two-step pumping emulsification procedure. The procedure is so easy that the emulsion could be prepared even during the surgical operation. The deposition after hepatic arterial administration of the emulsion was detected by an X-ray CT scanner. The concentration of epirubicin hydrochloride (EPI) in liver was increased and its residence was prolonged by encapsulating it in the w/o/w emulsion. The toxic effects of EPI and lipiodol on the normal hepatic cells were reduced. The w/o/w emulsion prepared by us is a suitable formulation for the TAE therapy.