Allied Innovative Systems (ALLIS) is a strategic partner of Industrial Sonomechanics, LLC (New York, NY, USA) in the development of Barbell Horn Ultrasonic Technology (BHUT). BHUT is an innovative tool for preparation of pharmaceutical nanoemulsions, liposomes and other nano-scale drug delivery systems.

Below we provide a brief description of BHUT and several applications.

Pharmaceutical Nanoemulsions and Liposomes

BACKGROUND

Pharmaceutical companies are under constant pressure to develop new, more effective drug formulations and improve their existing products. At the same time, there is a continuous struggle in the industry to maintain commercial viability and reduce time-to-market. It is now generally recognized that nanoemulsion and liposome-based formulations of marketed drugs can provide very effective novel therapies and enhance existing product lines, while reducing drug development costs and improving safety margins.

Liposomes are spherical, self-closed structures formed by one or several concentric lipid bilayers with an aqueous phase inside and in between the lipid bilayers. Some attractive properties of liposomes include their biocompatibility and ability to entrap water-soluble (hydrophilic) pharmaceutical agents in their internal water compartment and water-insoluble (hydrophobic) pharmaceuticals in their membrane. There are approximately a dozen liposomal drugs currently on the market, including anticancer agent Doxorubicin, in both polyethylene glycol (PEG) liposomes (Doxil from Ben Venue Laboratories) and in non-pegylated liposomes (Myocet from Enzon Pharmaceuticals). This agent is is approved for the treatment of solid tumors in patients with breast-carcinoma metastases and is also widely used off-label.

Quality and uniformity of nanoemulsions and liposomes are critically important, particularly for intravenous administration.  According to United States Pharmacopeia (USP), two parameters must be within specification in order to insure low toxicity and high physical stability of nanoemulsions and liposomes: 1) lipid globule mean droplet size (MDS) must be less than 500 nanometers (nm) and 2) the number of lipid globules with MDS exceeding 5 microns (mm) (PFAT5) must be less than 0.05%. This is of great significance for infusion safety: higher amounts (> 0.05%) of outsized (> 5 mm) lipid droplets are associated with instability; moreover, intravenously administered lipid droplets exceeding 5 um have been shown to cause adverse effects, in particular emboli in the lungs.

CURRENT METHODS OF PRODUCTION

Production of nanoemulsions and liposomes requires significant energy deposition and intense shear forces. Although low-energy emulsification methods do exist, they are impractical for the industrial-scale manufacture and have the disadvantage of requiring high concentrations of surfactants (in case of nanoemulsions) and toxic solvents (in case of liposomes), which must be removed before administering. The energy necessary for the emulsification process must, therefore, be provided by mechanical agitation such as stirring, high shear mixing, high-pressure homogenization or high-amplitude (high-intensity) ultrasound. The latter two methods have been demonstrated to be superior to all others, being able to produce nanoemulsions and liposomes with particles much smaller than 500 nm in diameter and narrow size distributions.

Although they are very costly, extremely energy intensive and difficult to service, high-pressure homogenizers are currently almost exclusively used for the industrial production of pharmaceutical nanoemulsions and liposomes.

PRODUCTION WITH HIGH-AMPLITUDE ULTRASOUND

High-amplitude ultrasound is a viable alternative to high-pressure homogenization. Intense shear forces necessary for the nanoemulsification are generated by ultrasonic cavitation, which produces violently and asymmetrically imploding vacuum bubbles and causes micro-jets that disperse and break up particles down to the nanometer scale. Known for many decades, this effect has been extensively studied and successfully used in small-scale production of pharmaceutical nanoemulsions and liposomes. However, prior to the introduction of Barbell Horn Ultrasonic Technology (BHUT), ultrasonic liquid processors could not effectively compete with high-pressure homogenizers in this market because they were not able to generate sufficiently high-amplitude (70 - 120 microns) ultrasonic vibrations on the industrial scale. Conventional high-power ultrasonic technology inherently forces all processes to run either at a small scale and high amplitude or a large scale and low amplitude, not allowing for the possibility of implementing high amplitudes on industrial scale. Thus, despite its potential, the ultrasonic method has mainly been restricted to laboratory investigations.

WHY ISM ULTRASONIC TECHNOLOGY?

Industrial Sonomechanics, LLC, (ISM) has successfully overcome the aforementioned limitation by developing BHUT, which permits constructing industrial ultrasonic systems able to operate at extremely high ultrasonic amplitudes (up to about 200 microns). The output tip areas of the incorporated Barbell horns and the resulting productivity rates of the systems are more than 10 times higher than those of any conventional ultrasonic device operating at high amplitudes.

ISM's Barbell horn-based high-amplitude industrial ultrasonic processors can be used for the commercial-scale production of the highest-quality nanoemulsions and liposomes, while offering many advantages over high-pressure homogenizers. These include significantly lower equipment costs, smaller number of wetted parts (easier cleaning, less wear and simpler servicing), no need to use a separate rotor-stator high-shear mixer to prepare a preliminary emulsion, as well as a much more practicable aseptic processing. In addition, it is much easier to create an ultrasonic system design that eliminates the need for multiple passes of the liquid through the system, which has not been possible with any high-pressure homogenizer.

The data presented below was collected in cooperation with Industrial Sonomechanics, LLC (New York, NY, USA)

Nanoemulsions similar to those presented in Examples 1 and 2 (in Table 2 on the left - Emulsions 1 and 2) were prepared with the oil phase containing 0.05 mg/ml of ZnPC with and without preliminary dissolution of ZnPC in ethanol (final ethanol concentration did not exceed 2%). In this case, either ZnPC powder or its ethanol solution was added to the oil phase. In order to examine the effect of filtration on the size of the droplets, the nanoemulsions were filtered using a 0.445 micron filter. Both filtered and unfiltered nanoemulsions were analyzed and compared.

As can be seen from Table 2, the mean droplet diameters for ZnPC-containing and plain Emulsions 1 and 2 are approximately the same, all significantly lower than 500 nm. Other most significant results obtained for Emulsions 1, 2 and Liposomes include: 1) The addition of ethanol to Emulsions 1 and 2 does not significantly change droplet size; 2) The droplet sizes for filtered (through a 0.445 micron filter) and unfiltered Emulsion 2 are practically the same; 3) The absorbance and fluorescence spectra obtained for ZnPC-containing Emulsions 1 and 2 coincide with those for solutions of ZnPC in pure soybean oil; and 4) The concentration of metals in all prepared emulsions and liposomes is below the detection limit of the X-ray energy-dispersive spectroscopy method used for metal content measurements.