Reducing Size with a Microfluidizer

The unit operation of size reduction is usually monitored through particle size analysis. Numerous technologies are available to perform size reduction, homogenization, or both. Microfluidizer is one technology that is used to reduce the size of suspensions and emulsions in an efficient way. In this article, a lab-scale Microfluidizer was used to process an emulsion and liposomes formulation, and a Entegris Nicomp dynamic light scattering (DLS) system was used to study the size reduction process.

Microfluidizer Technology

Microfluidics’ Microfluidizer was used to process the target samples in this study. The sample present in an inlet reservoir is taken by the Microfluidizer, and an intensifier pump creates pressures of up to 40,000 psi to push the sample via the interaction chamber.

This interaction chamber exposes the sample to strong, continuous impact and high shear rates. Following this, the sample is cooled, and the nanoscale particles are either reclaimed for use or recirculated for numerous passes to obtain the required homogeneous particle size distribution. This Microfluidizer method can be repeated and can be scaled up from lab to commercial processing volumes.

Figure 1. The Microfluidizer process

Figure 2. Y single slotted (left) and multi-slotted (right) interaction chambers

Materials and Equipment Used

All of the samples considered in this study were processed on the bench top unit, LV1 Microfluidizer (Figure 3). This unit was designed to provide milliliter-scale Microfluidizer quality nanotechnology processing, with many uses in the biotechnology, pharmaceutical, and other industries.

Figure 3. The LV1 Microfluidizer

A laser diffraction analyzer was used to make the measurements to monitor the size reduction for the before processing results, and a Entegris Nicomp DLS system (Figure 4) was used to make the measurements for the post processing analysis.

Figure 4. The Nicomp DLS system

An oil-in-water emulsion was the initial sample that mimics a drug delivery vehicle. The scattered phase includes 1.5 wt% surfactant and 5 wt% Squalane. The following formula was used to create dispersion:

• Tween 80 = 0.75%
• DI Water = 93.5%
• Span 85 = 0.75%
• Squalane = 5%

Before processing on the Microfluidizer, a rotor-stator mixer (IKA T25) was used to mix the sample for a period of 5 minutes. The LV1 Microfluidizer processor was then used to create the nanoemulsions. Using the F12Y chamber operating at 20k psi Sample 329A was processed, and using the F12Y chamber operating at 30k psi Sample 329B was processed. Both samples were processed at the selected pressure for one and five passes via the Microfluidizer. The following formula was used to generate the second sample, liposomes:

• Lipoid S 100 = 1.5%
• DI Water = 93.5%
• Soybean Oil = 5%

Before processing on the Microfluidizer, a rotor-stator mixer (IKA T25) was used to mix the sample for 5 minutes. The LV1 Microfluidizer processor was then used to produce the liposomes. Sample 329C was processed using the F12Y chamber operating at 20k psi, and Sample 329D was processed using the F12Y chamber operating at 30k psi. Both samples were processed at the selected pressure for one, two and five passes via the Microfluidizer.

Results: Nanoemulsion

The nanoemulsion sample was measured after mixing by rotor-stator but before processing by the Microfluidizer by laser diffraction to have a median size (Dv50) = 8.5 μm, or 8500 nm. Using the Microfluidizer, the sample was subsequently processed at 20k psi and finally determined by the Nicomp DLS system following one and five passes. The results are depicted in Figures 5 and 6, and Table 1.

Figure 5 displays the processed results in light blue (right Y axis) and the unprocessed to processed size reduction in orange (left Y axis). Table 1 shows the polydispersity index PI and intensity weighted mean diameter.

Figure 5. Nanoemulsion sample 329A, unprocessed and 1 and 5 passes, 20k psi.

Figure 6. Nanoemulsion sample 329A, 1 and 5 passes, 20k psi.

Table 1. Nanoemulsion sample 329A, 1 and 5 passes, 20k psi

Subsequently, the Microfluidizer was used to process the sample at 30k psi, and the same was determined by the Nicomp DLS system following one and five passes. The results are illustrated in Figures 7 and 8 and Table 2.

Figure 7. Nanoemulsion sample 329B, unprocessed and 1 and 5 passes, 30k psi

Figure 8. Nanoemulsion sample 329B, 1 and 5 passes, 30k psi

Table 2. Nanoemulsion sample 329B, 1 and 5 passes, 30k psi

Results: Liposomes

The rotor-stator mixer was used to mix the liposome sample and the same was measured. However, this was done prior to processing by the Microfluidizer by laser diffraction to possess a median size (Dv50) = 8.9 µm. The Microfluidizer was then used to process the sample 329C at 20k psi and determined by the Nicomp DLS system following one, two, and five passes. The results are displayed in Figures 9 and 10 and Table 3. Figure 8 depicts the processed results in maroon (right Y axis) and the unprocessed to processed size reduction in blue (left Y axis).

Figure 9. Liposome sample 329C, unprocessed, and processed at 1, 2, and 5 passes, 20k psi

Figure 10. Liposome sample 329C, 1, 2, and 5 passes

Table 3. Liposome sample 329C after 1, 2 and 5 passes, 20k psi

Again, the Microfluidizer was used to process the liposome sample 329D at 30k psi and determined by the Nicomp DLS system following one, two, and five passes. The results are depicted in Figures 11 and 12 and Table 4.

Figure 11. Liposome sample 329D, unprocessed, 1, 2, and 5 passes, 30k psi.

Figure 12. Liposome sample 329D, 1, 2, and 5 passes, 30k psi

Table 4. Liposome sample 329D, 1, 2, and 5 passes, 30k psi

Conclusion

This article has shown how the LV1 Microfluidizer is a simple and efficient technology that can be used for producing liposome and nanoemulsion samples. Size distributions turn out to be tighter and smaller after processing via the Microfluidizer. A major advantage of carrying out lab scale processing and formulation experiments is that with the help of the Microfluidizer the process can be ramped up to commercial scale without any major complications or any need for extra development work. The Nicomp DLS system was shown to be a simple and effective instrument for monitoring the size reduction using the Microfluidizer.

This information has been sourced, reviewed and adapted from materials provided by Entegris

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