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978-3-8439-0569-5, Reihe Pharmazeutische Technologie
Julia Christina Kasper
Lyophilization of Nucleic Acid Nanoparticles - Formulation Developement, Stabilization Mechanisms, and Process Monitoring
336 Seiten, Dissertation Ludwig-Maximilians-Universität München (2012), Softcover, A5
In the general introduction of this thesis provides a summary of the lyophilization process in brief and discusses recent advances and further challenges in lyophilization with a strong focus on the freezing step during lyophilization. Moreover, the demand and the challenge to develop lyophilized, long-term stable formulations of pDNA and siRNA polymeric nanoparticles (polyplexes) was highlighted.
In a first step, a micro-mixer method was established for the preparation of polyplexes in order to guarantee their defined size and quality. Secondly, a lyophilized, long-term stable pDNA/LPEI polyplex formulation was developed the first time by selecting an appropriate buffer system and by introducing higher Mw excipients for sufficient particle stabilization at low osmotic pressure during freezing and drying. Moreover, the effect of freezing on the stability of polyplexes was thoroughly investigated by the aid of a controlled ice nucleation method. It was found that the time span particles spend in the low viscous state after ice nucleation, determined by initial sample viscosity and applied freezing rate, is the predominant factor in the stabilization of nanoparticles during freezing. In a next step, lyophilized, long-term stable formulations for siRNA/oligoamino-amide polyplexes based on two different oligomers were developed. In this case, siRNA polyplexes maintained particle size and gene silencing efficiency in absence or the presence of only low amounts of stabilizers, depending on the polymer used.. Finally, an optical fiber system (OFSs) was evaluated as novel process monitoring tool during lyophilization. The OFS showed several advantages compared to conventional thermo sensors, which turn the OFS into a highly attractive monitoring tool during lyophilization.
In conclusion, in this thesis it was shown that an up-scaled preparation method in combination with subsequent lyophilization is a promising approach to reproducibly achieve long-term stable pDNA or siRNA polyplexes maintaining particle size and biological activity at pharmaceutically defined high quality. The results demonstrated that formulation development, highly dependent on the used type of polymer or nucleic acid, and process development in combination with appropriate process monitoring needs always to be performed hand in hand. All in all, this thesis makes an essential contribution in order to move closer from a promising biotechnological approach towards clinic-friendly drugs.