Nucleic Acid Carriers Based on Precise Polymer Conjugates

Polymer polydispersity, random conjugation of functional groups, and poorly understood structure–activity relationships have constantly hampered progress in the development of nucleic acid carriers. This review focuses on the synthetic concepts for the generation of precise polymers, site-specific conjugation strategies, and multifunctional conjugates for nucleic acid transport. Dendrimers, defined peptide carriers, sequence-defined polyamidoamines assembled by solid-phase supported synthesis, and precise lipopeptides or lipopolymers have been characterized for pDNA and siRNA delivery. Conjugation techniques such as click chemistries and peptide ligation are available for conjugating polymers with functional transport elements such as targeting or shielding domains and for direct covalent modification of therapeutic nucleic acids in a site-specific mode

Nucleic Acid Carriers Based on Precise Polymer Conjugates

Polymer polydispersity, random conjugation of functional groups, and poorly understood structure–activity relationships have constantly hampered progress in the development of nucleic acid carriers. This review focuses on the synthetic concepts for the generation of precise polymers, site-specific conjugation strategies, and multifunctional conjugates for nucleic acid transport. Dendrimers, defined peptide carriers, sequence-defined polyamidoamines assembled by solid-phase supported synthesis, and precise lipopeptides or lipopolymers have been characterized for pDNA and siRNA delivery. Conjugation techniques such as click chemistries and peptide ligation are available for conjugating polymers with functional transport elements such as targeting or shielding domains and for direct covalent modification of therapeutic nucleic acids in a site-specific mode

New Sequence-Defined Polyaminoamides with Tailored Endosomolytic Properties for Plasmid DNA Delivery

Heterogeneity of polymeric carriers is one of the most elusive obstacles in the development of nonviral gene delivery systems, concealing interaction mechanisms and limiting the use of structure–activity relationship studies. In this report, novel sequence-defined polyaminoamides, prepared by solid-phase assisted synthesis, were used to establish first structure–activity relationships for polymer-based plasmid DNA delivery. By combining a cationic building block with hydrophobic modifications and bioreversible disulfide cross-linking sites, transfection polymers with tailored lytic and DNA binding properties were designed. These polymers demonstrated clear correlation between structure and performance in lysis and DNA binding assays. In vitro studies showed negligible toxicity and highly efficient gene transfer, demonstrating the potential of this platform in the fast, combinatorial development of new transfection polymers

Nanosized Multifunctional Polyplexes for Receptor-Mediated SiRNA Delivery

Although our understanding of RNAi and our knowledge on designing and synthesizing active and safe siRNAs significantly increased during the past decade, targeted delivery remains the major limitation in the development of siRNA therapeutics. On one hand, practical considerations dictate robust chemistry reproducibly providing precise carrier molecules. On the other hand, the multistep delivery process requires dynamic multifunctional carriers of substantial complexity. We present a monodisperse and multifunctional carrier system, synthesized by solid phase supported chemistry, for siRNA delivery in vitro and in vivo. The sequence-defined assembly includes a precise cationic (oligoethanamino)amide core, terminated at the ends by two cysteines for bioreversible polyplex stabilization, at a defined central position attached to a monodisperse polyethylene glycol chain coupled to a terminal folic acid as cell targeting ligand. Complexation with an endosomolytic influenza peptide-siRNA conjugate results in nanosized functional polyplexes of 6 nm hydrodynamic diameter. The necessity of each functional substructure of the carrier system for a specific and efficient gene silencing was confirmed. The nanosized polyplexes showed stability in vivo, receptor-specific cell targeting, and silencing of the EG5 gene in receptor-positive tumors. The nanosized appearance of these particles can be precisely controlled by the oligomer design (from 5.8 to 8.8 nm diameter). A complete surface charge shielding together with the high stability result in good tolerability in vivo and the absence of accumulation in nontargeted tissues such as liver, lung, or spleen. Due to their small size, siRNA polyplexes are efficiently cleared by the kidney

Solid-phase-assisted synthesis of targeting peptide-PEG-oligo(ethane amino)amides for receptor-mediated gene delivery.

In the forthcoming era of cancer gene therapy, efforts will be devoted to the development of new efficient and non-toxic gene delivery vectors. In this regard, the use of Fmoc/Boc-protected oligo(ethane amino)acids as building blocks for solid-phase-supported assembly represents a novel promising approach towards fully controlled syntheses of effective gene vectors. Here we report on the synthesis of defined polymers containing the following: (i) a plasmid DNA (pDNA) binding domain of eight succinoyl-tetraethylenpentamine (Stp) units and two terminal cysteine residues; (ii) a central polyethylene glycol (PEG) chain (with twenty-four oxyethylene units) for shielding; and (iii) specific peptides for targeting towards cancer cells. Peptides B6 and c(RGDfK), which bind transferrin receptor and αvβ3 integrin, respectively, were chosen because of the high expression of these receptors in many tumoral cells. This study shows the feasibility of designing these kinds of fully controlled vectors and their success for targeted pDNA-based gene transfer

New Sequence-Defined Polyaminoamides with Tailored Endosomolytic Properties for Plasmid DNA Delivery

Heterogeneity of polymeric carriers is one of the most elusive obstacles in the development of nonviral gene delivery systems, concealing interaction mechanisms and limiting the use of structure–activity relationship studies. In this report, novel sequence-defined polyaminoamides, prepared by solid-phase assisted synthesis, were used to establish first structure–activity relationships for polymer-based plasmid DNA delivery. By combining a cationic building block with hydrophobic modifications and bioreversible disulfide cross-linking sites, transfection polymers with tailored lytic and DNA binding properties were designed. These polymers demonstrated clear correlation between structure and performance in lysis and DNA binding assays. In vitro studies showed negligible toxicity and highly efficient gene transfer, demonstrating the potential of this platform in the fast, combinatorial development of new transfection polymers

Nanosized Multifunctional Polyplexes for Receptor-Mediated SiRNA Delivery

Although our understanding of RNAi and our knowledge on designing and synthesizing active and safe siRNAs significantly increased during the past decade, targeted delivery remains the major limitation in the development of siRNA therapeutics. On one hand, practical considerations dictate robust chemistry reproducibly providing precise carrier molecules. On the other hand, the multistep delivery process requires dynamic multifunctional carriers of substantial complexity. We present a monodisperse and multifunctional carrier system, synthesized by solid phase supported chemistry, for siRNA delivery <i>in vitro</i> and <i>in vivo</i>. The sequence-defined assembly includes a precise cationic (oligoethanamino)amide core, terminated at the ends by two cysteines for bioreversible polyplex stabilization, at a defined central position attached to a monodisperse polyethylene glycol chain coupled to a terminal folic acid as cell targeting ligand. Complexation with an endosomolytic influenza peptide-siRNA conjugate results in nanosized functional polyplexes of 6 nm hydrodynamic diameter. The necessity of each functional substructure of the carrier system for a specific and efficient gene silencing was confirmed. The nanosized polyplexes showed stability <i>in vivo</i>, receptor-specific cell targeting, and silencing of the EG5 gene in receptor-positive tumors. The nanosized appearance of these particles can be precisely controlled by the oligomer design (from 5.8 to 8.8 nm diameter). A complete surface charge shielding together with the high stability result in good tolerability <i>in vivo</i> and the absence of accumulation in nontargeted tissues such as liver, lung, or spleen. Due to their small size, siRNA polyplexes are efficiently cleared by the kidney