Tumor-Targeted Anti-VEGF RNAi Capable of Sequentially Responding to Intracellular Microenvironments for Potent Systemic Tumor Suppression

Polymeric-Micelle-Based Delivery Systems for Nucleic Acids

Nucleic acids can modulate gene expression specifically. They are increasingly being utilized and show huge potential for the prevention or treatment of various diseases. However, the clinical translation of nucleic acids faces many challenges due to their rapid clearance after administration, low stability in physiological fluids and limited cellular uptake, which is associated with an inability to reach the intracellular target site and poor efficacy. For many years, tremendous efforts have been made to design appropriate delivery systems that enable the safe and effective delivery of nucleic acids at the target site to achieve high therapeutic outcomes. Among the different delivery platforms investigated, polymeric micelles have emerged as suitable delivery vehicles due to the versatility of their structures and the possibility to tailor their composition for overcoming extracellular and intracellular barriers, thus enhancing therapeutic efficacy. Many strategies, such as the addition of stimuli-sensitive groups or specific ligands, can be used to facilitate the delivery of various nucleic acids and improve targeting and accumulation at the site of action while protecting nucleic acids from degradation and promoting their cellular uptake. Furthermore, polymeric micelles can be used to deliver both chemotherapeutic drugs and nucleic acid therapeutics simultaneously to achieve synergistic combination treatment. This review focuses on the design approaches and current developments in polymeric micelles for the delivery of nucleic acids. The different preparation methods and characteristic features of polymeric micelles are covered. The current state of the art of polymeric micelles as carriers for nucleic acids is discussed while highlighting the delivery challenges of nucleic acids and how to overcome them and how to improve the safety and efficacy of nucleic acids after local or systemic administration.

Virus-like siRNA construct dynamically responsive to sequential microenvironments for potent RNA interference

Cytoplasmic transportation of therapeutic nucleic acids is deemed as an onerous task with aim of precise knockdown towards the targeted genes. Pertaining to the programed functionalities of natural virus in circumventing the biological barriers, we tailored multifaceted chemistries into manufacture of synthetic siRNA delivery vehicles in resembling the functionalities of viral vectors to dynamically tackle with a sequential of biological obstacles encountered in the journey of systemic anti-tumor RNAi therapy. Once harnessing ligands with RGD motif for specific internalization into subcellular endosomal compartments of the tumor cells, the architecture of the proposed delivery vehicles was subjected to facile transformation responsive to pH stimuli in acidic endosomal compartments. The external biocompatible PEGylation palisade was consequently detached, unveiling the cytomembrane-lytic cationic components to commit disruptive potencies to the anionic endosomal membranes for translocation of siRNA conjugates into cytosol. Eventually, liberation of active siRNA could be accomplished due to its responsiveness to the strikingly high level of glutathione in cytosol, thereby contributing to potent RNAi. Hence, our elaborated virus-mimicking platform has demonstrated significant anti-tumor efficacy through systemic administration of anti-angiogenic RNAi payloads, which inspired prosperous potentials in a variety of therapeutic applications.

Polymeric RNAi Constructs Tailored with Appreciable Transcellular Trafficking Functions for Potential Suppression of Parathyroid Hormone Production

Polymeric small interfering RNA (siRNA) conjugate was elaborated to sequentially circumvent the predefined biological barriers encountered in the journey of transcellular delivery of siRNA into cytosol. Herein, classic ring-opening polymerization was employed for synthesis of well-defined poly(amino acid) derivatives possessing an array of carboxyl groups in an attempt to resemble the structural characteristics of hyaluronan. Furthermore, the hyaluronan-like synthetic was conjugated with a multiple of siRNA through a glutathione (GSH)-responsive disulfide linkage. The siRNA conjugate appeared to utilize the hyaluronan-specific receptors of CD44 for cell internalization, indicating similar functionalities to our hyaluronan-mimicking synthetic. Furthermore, the carboxyl groups of hyaluronan-like synthetics were designed to be selectively detached in subcellular acidic endosomes/lysosomes and transform into the cytomembrane-disruptive flanking ethylenediamine moieties, which appeared to be crucial in facilitating translocation of siRNA payloads from entrapment and degradation in lysosomes toward the cytosol. Eventually, active siRNA could be smoothly released from the synthetic due to the GSH cleavage disulfide linkage (disulfide), consequently accounting for potent RNA knockdown activities (>90%) toward cancerous cells. In addition, appreciable knockdown of parathyroid hormone was also achieved from our proposed siRNA conjugates in parathyroid cells. Hence, the elaborated siRNA conjugate showed tremendous potential in treatment of hyperparathyroidism, and could be developed further for systemic RNA interference (RNAi) therapeutics. Moreover, this study could also be the first example of a synthetic mimic to hyaluronan acquiring its functionalities, which could have important implications for further development of biomimic materials in pursuit of biomedical applications.