pH-sensitive packaging of cationic particles by an anionic block copolymer shell

Area of Science:

• Biomaterials Science
• Gene Therapy
• Polymer Chemistry

Background:

• Cationic non-viral vectors are promising for gene delivery but face challenges with toxicity and systemic application.
• Polyethylene glycol (PEG) shielding improves biocompatibility but often reduces transfection efficiency.
• Developing effective, non-toxic gene delivery systems with enhanced cellular uptake and endosomal escape is crucial.

Purpose of the Study:

• To design and evaluate a novel multicomponent polymer system for enhanced gene delivery.
• To utilize a pH-responsive block copolymer as a shielding agent to improve biocompatibility and transfection efficiency.
• To assess the performance, stability, and toxicity of the developed system in vitro and in vivo.

Main Methods:

• Synthesis of cationic hydrophobic particles (PBMD) and a pH-responsive block copolymer (PNC) for shielding.
• Characterization of PNC-shielded particles, including size, stability, and pDNA complexation.
• Evaluation of in vitro transfection efficiency in adherent (HEK293T) and suspension (K-562) cells.
• Assessment of cytotoxicity in human erythrocytes and K-562 cells.
• Pilot in vivo study on mouse bone marrow blood cells.

Main Results:

• PNC-shielded particles demonstrated stable pDNA complexation and remained below 200 nm in diameter.
• The system showed pH-dependent behavior, preventing erythrocyte interaction at pH 7.4 but enabling membrane leakage at pH 6.
• Transfection efficiency in HEK293T and K-562 cells was comparable or superior to commercial linear poly(ethylenimine) (LPEI).
• Cytotoxicity was significantly reduced, particularly in K-562 cells and erythrocytes.
• In vivo studies showed slightly enhanced cell transfection in mouse bone marrow cells compared to naked pDNA.

Conclusions:

• The developed multicomponent polymer system, featuring pH-responsive shielding, offers a promising approach for efficient and safe gene delivery.
• The pH-sensitive polymer (PNC) provides biocompatibility and stability while facilitating endosomal escape for high transfection rates.
• This system overcomes limitations of traditional PEGylation, offering a viable alternative for both in vitro and in vivo gene transfection applications.