Purpose: The objective of this work was to utilize a continuous flash nano-precipitation (FNP) process to produce self-assembled clofazimine (CFZ)-loaded nanoparticles. This work is part of an effort among the collaborators to implement and scale up the FNP process for low-cost manufacturing of nanoformulation drugs.
Methods: FNP SUSPENSION. The drug-loaded zein nanoparticles (Zein-NP) were manufactured through a multi-inlet vortex mixer (MIVM). Zein-NP suspension was prepared by mixing pH 7.4 citrate buffer, 1 mg/mL casein in pH 7.4 citrate buffer, 6 mg/mL zein in 60%ethanol and 6 mg/mL CFZ in acetone in a MIVM at flow rates of 14.75, 14.75, 4.92 and 4.92 mL/min, respectively. The Reynolds number (Re) at this flow rate was 6579. Zein-NP suspension could be continuously produced by using 4 constant flow pumps.
SPRAY-DRIED FNP. Then, the Zein-NP suspension was fed directly into a spray drier to obtain Zein-NP spray-dried powder. The spray-dried powder was characterized by TGA, SEM, PLM, XRPD, encapsulation efficiency (EE), drug loading (DL) and particle size.
Results: Experiments were conducted and showed that nanoparticles can be produced via a continuous FNP process using an MIVM mixer. The achievable particle size depends on the Reynolds number (Re). The particle size became smaller as the Re was increased, until the Re was around 4000, where the particle size became independent of Re. At optimized flow rates (Re > 4000) using the selected formulation, the mean particle size of Zein-NP suspension was ~200 nm with a narrow distribution (P.I. of 0.061). The FNP suspension particle size was sufficiently stable under ambient condition, increasing slightly after 22 hours to ~390 nm. Furthermore, the stability of Zein-NP suspension could be prolonged for several days by adding an equal volume of water immediately after production; the addition of water served to decrease the level of organic solvent, which helped ‘harden’ the particles and prevent aggregation. After spray drying, a red Zein-NP powder was obtained. The spray dried powder could be easily re-dispersed in water to give a particle size of 238 nm (P.I. = 0.191). Zein-NP showed irregular shape with depression under SEM. The amorphous state of the powder was observed by PLM and XRPD, which revealed that CFZ was successfully encapsulated within nanoparticles. EE% and DL% of Zein-NP were determined to be 99.0% and 18.0%, respectively. A weight loss of 2.6% at 100oC, as analyzed by TGA, could be attributed to residual solvents. Zein-NPs were stable for 6 month at 25⁰C Hence, it was feasible to prepare CFZ nanoparticles via a continuous FNP process and to prepare spray-dried NP powder with the desired physical properties for further processing.
Conclusion: This study confirmed the implementation of FNP process at the lab-scale and paved the way for scaled-up production of Zein-NP at the pilot-scale for GMP drug product manufacturing.
Jing Li– Senior Scientist, STA Pharmaceutical
Hanpeng Chen– Senior Scientist, STA Phamaceutical
Liang Mao– Associate Director, STA Pharmaceutical, Shanghai, Shanghai
Vadim Klyushnichenko– Vice President, Calibr
Jie Feng– Princeton University
Yingyue Zhang– Postdoctoral Research Associate, Princeton University, Franklin Park
Simon McManus– Princeton University
Chester Markwalter– Princeton University
Kurt Ristroph– Princeton University
Chang Tian– Princeton University
Robert Prud'homme– Professor, Princeton University