(583g) Development of a Continuous Inline Monitored Lab Plant Based on the Microfluidizer® Technology for the Production of Nanoparticles

Nanodrug delivery systems offer the potential for encapsulating a range of active pharmaceutical ingredients and transporting them safely to the desired site of action. However, to fully exploit their potential, the production of these systems on an industrial scale needs to be improved. Manufacturing is typically performed via time-consuming and error-prone multi-step batch processes that are costly, difficult to scale and hard to control. This, however, poses the risk of producing products of lesser quality with associated safety concerns. On the one hand, this is due to a lack of process understanding of the individual manufacturing steps. On the other hand, process parameters and product quality are not sufficiently controlled during manufacturing, so existing strategies do not meet the requirements for quality and flexibility. This clearly shows that a continuous production line that is as flexible as possible, is urgently needed to keep pace with advances in medicine. Only in this way, can nanotechnology be further advanced as a drug delivery platform for innovative drugs such as intracellular targets.

The focus of this study is the development of a top-down production strategy with the scalable Microfluidizer^® (MF) technology, which allows particles to be processed under constant and identical process conditions regardless of scale. To enable solvent-free manufacturing of lipid-based nanoparticles, the LM20 Microfluidizer^® processor (Microfluidics, Westwood, USA) was adapted to allow process temperatures ranging from 5 to 70 °C. Moreover, it was equipped with a double-walled stainless steel feed vessel that was temperature-controlled via a water bath. Likewise, the Interaction Chamber™ and the conveying/feeding lines were thermo-regulated via an external water bath. To avoid massive temperature fluctuations, the unheated areas of the system were thermally insulated. Solidification of the nano-lipid droplets requires a subsequent cooling step in a continuous way. Accordingly, after each homogenization cycle, dispersions were transferred either back to the feed tank or to the cooling unit via a temperature-controlled pump. The cooling unit consisted of a cooling coil with defined dimensions and an external water bath that allowed controlled cooling under defined conditions. Finally, inline monitoring of particle sizes was performed using the NanoFlowSizer (InProcess-LSP, Oss, The Netherlands) and the zeta potential was determined online via electrophoretic dynamic light scattering. To test the established set-up and screen it for critical parameters, different solid lipids (i.e., Precirol^® ATO 5, Gelucire^® 43/01, both from Gattefossé, Saint Priest, France) and a liquid lipid (i.e., Labrafac™ lipophile WL 1349, Gattefossé) were used. Solid lipid nanoparticles (SLN) consist of a solid lipid and a stabilizer (Tween 80), and nanostructured lipid carriers (NLC) comprise a solid and a liquid lipid in a specific ratio, plus a stabilizer. Material attributes on processability and product characteristics (i.e., thermal behavior, material interactions, miscibilities, solid state) were determined via Differential Scanning Calorimetry (DSC, 204F1 Phoenix, Netzsch GmbH, Selb, Germany) and RAMAN spectroscopy (Perkin Elmer, Waltham, USA). Design of experiments (DoE) studies were performed as suggested by the MODDE^® software. For particle preparation, lipid mixtures were pre-emulsified via high-shear (12000 rpm; 30 sec) and transferred to the MF set-up. The homogenization pressure and time were adjusted (i.e., 500-1500 bar; 1-10 min). Moreover, the influence of different cooling rates (i.e., 4-10 °C/min) and the final product temperature (i.e., 4-25 °C) on product quality were investigated. Particle size and particle size distribution were selected as response. In-line acquired results were compared to off-line assessed data via dynamic light scattering (DLS; Litesizer 500, Anton Paar GmbH, Graz, Austria). Statistical analysis was performed via the MODDE^® software, considering values for R² (i.e., model fit), Q² (i.e., prediction precision), model validity and reproducibility.

DSC studies revealed that required process temperatures were only affected by the melting temperatures (T_m) of the solid bulk materials, as T_m of Precirol^® (60.3 ± 0.5 °C) and Gelucire^® 43/01 (43.1 ± 0.3 °C) were shifted by less than 2 °C through the addition of the liquid lipid. As a result, required MF process temperatures of 70 °C for Precirol^® and 55 °C for Gelucire^® 43/01 formulations were evaluated. Statistical data analysis showed that the particle size was dependent on the matrix composition and homogenization time, whereas the homogenization pressure had only a minor effect. The cooling strategy (i.e., time, temperature) of the tested compositions did not show a significant influence on the product quality in terms of size and size distribution. Overall, meaningful results were obtained as the statistical analysis showed R² and Q² values of more than 0.5 and a difference of less than 0.3. Optimized process conditions yielded particles with a size <200 nm and a narrow distribution (i.e., PdI <0.1). In addition, in-line measured particle sizes were in accordance with off-line data. Finally, DSC and RAMAN studies revealed that all lipid nanoparticle formulations were in the crystalline state and did not show different polymorphic forms. In summary, by using the newly established continuous nanomanufacturing line, solvent-free SLN and NLC could be successfully fabricated and monitored in terms of their size and zeta potential in- and online.