Drying of a plasmid containing formulation: chitosan as a protecting agent

Area of Science:

• Biomaterials Science
• Gene Delivery Systems
• Polymer Chemistry

Background:

• Developing efficient gene delivery systems requires methods to extend their lifespan.
• Chitosan is a safe, biocompatible, and accessible carrier for gene delivery.
• Stabilization processes are crucial for maintaining the efficacy of gene delivery vectors.

Purpose of the Study:

• To evaluate chitosan's ability to maintain transfection efficiency during spray-drying and freeze-drying.
• To assess the impact of common excipients on the stability of chitosan-DNA nanocomplexes.
• To determine the protective effects of low molecular weight chitosan (LMWC) on DNA structure during these drying processes.

Main Methods:

• Chitosan's molecular weight was reduced to create low molecular weight chitosan (LMWC).
• LMWC was complexed with plasmid DNA (pDNA) to form nanocomplexes.
• Nanocomplex suspensions were processed using spray-drying or a modified freeze-drying technique in the presence of lactose or leucine.
• Key properties including size, polydispersity, zeta potential, DNA integrity, and transfection efficiency were analyzed.

Main Results:

• Both freeze-drying and spray-drying maintained the size distribution of most nanocomplexes.
• LMWC protected plasmid DNA (pDNA) supercoiled structure effectively in both drying methods.
• DNA degradation was more pronounced in spray-dried samples with lower N/P ratios.
• Transfection efficiency was preserved similarly by both drying techniques, even at lower N/P ratios.

Conclusions:

• Low molecular weight chitosan (LMWC) effectively protects DNA structure and transfection efficiency during spray-drying and freeze-drying.
• The presence of leucine did not significantly alter the properties of the processed nanocomplexes.
• These findings suggest LMWC is a promising stabilizer for gene delivery vectors, enhancing their shelf-life and applicability.