KSEF RDE: Scale-up of DNA Encapsulatation Processes

Abstract The objective of this proposal is to develop proof-of-concept data for using static mixers to generate uniform particle size distributions of DNA/polymer complexes for delivering gene therapy and other applications. There have been recent reports of sub-micron complexes of DNA that could provide safe and efficient delivery methods. Examples include: the encapsulation of DNA globules by biodegradable polymers (Liang, Hsiao et al. 2006), diblock copolymers containing amino groups (Mu, Ma et al. 2004; Zhang, Wang et al. 2005), cationic surfactant micelles (Zhu and Evans 2006), self-assembly of chitosan with surfactants (Grant, Cho et al. 2006), and chitosan-stearic acid micelles for gene delivery (Hu, Zhao et al. 2006). Several of these technologies are based on the critical micelle concentrations for self-assembly. Liquid-liquid mixing to form submicron particles can be done using conventional stirred tank agitation, pipe flow systems, colloid mills, ultrasonic mixers, and static mixers. Static mixers (not yet mentioned in the literature) seem particularly well suited to solving the scaleup challenges from the bench to full scale production because they are low shear devices requiring small equipment volumes, can readily be adapted for a variety of flow rates, and can be cleaned and sterilized easily. If the formation of the DNA/polymer complexes is rapid in experimental time, it is likely that the diameters of the complexes will be related to dimensionless numbers (Weber, Reynolds) of the flow system (Thakur, Vial et al. 2003). Should the flocculation process be rate-controlling, the Peclet number of the flow might be the important correlating tool (if so, then new correlations would have to be developed for the particle size distributions). The key research result would be a figure demonstrating the correlation between appropriate dimensionless numbers and the average complex size. Technical Narrative Introduction and Expected significance of the work: Project summary The objective of this proposal is to develop proof-of-concept data for using static mixers to generate uniform particle size distributions of DNA/polymer complexes in aqueous media for delivering gene therapy and other applications. There have been recent reports of sub-micron complexes of DNA that could provide safe and efficient delivery methods. Examples include: the encapsulation of DNA globules by biodegradable polymers, diblock copolymers containing amino groups, cationic surfactant micelles, self-assembly of chitosan with surfactants, and chitosan-stearic acid micelles for gene delivery. Liquid-liquid mixing to form submicron particles can be done using conventional stirred tank agitation, pipe flow systems, colloid mills, ultrasonic mixers, and static mixers. Static mixers (not yet mentioned in the literature) seem particularly well suited to solving the scale-up challenges from the bench to full scale production because they are low shear devices requiring small equipment volumes, can readily be adapted for a variety of flow rates, and can be cleaned and sterilized easily. This study is intended to provide preliminary data for an NIH STIR submission by Goldstream Labs, so only a small portion of the operating variable ranges will be explored. The formation of the DNA/polymer complexes should be rapid, and it is likely that the diameters of the complexes will be related to dimensionless numbers (Weber, Reynolds) of the flow system. The Peelet number could be the correlating factor should the flocculation process be rate-controlling. It also is likely that complexing process is heavily dependent on the volume ratio of the DNA and polymer components, which would lead to new correlations. The key research result would be a figure demonstrating the correlation between appropriate dimensionless numbers and the average KSEF-1513-RDE-010 Page 4