Sticky nanoparticles: a platform for siRNA delivery by a bis(zinc(II) dipicolylamine)-functionalized, self-assembled nanoconjugate

Delivering the goods: Multifunctional, self-assembled, polymeric nanoparticles for the simultaneous delivery of small-molecule drugs and siRNA have been synthesized. The nanoparticles are composed of biodegradable hyaluronic acid, for tumor targeting and cellular delivery, and a high siRNA binding affinity is provided by a Zn(II)-dipicolylamine analogue as an artificial phosphate-binding receptor (see scheme).     

Polymeric‐Micelle‐Based Nanomedicine for siRNA Delivery

Small interfering RNAs (siRNAs) are a rapidly emerging class of innovative nucleic acid medicines for the treatment of diseases such as cancer. However, significant hurdles hamper their clinical application, including poor cellular uptake, instability under physiological conditions, off‐target effects, and possible immunogenicity. The development of suitable delivery systems that protect and efficiently transport siRNA to targeted cells has been pursued. Nanoparticle‐based vectors have been widely investigated as potential candidates for effective siRNA delivery. Among the different nanoparticles, polymeric micelles, which are self‐assembled nanoparticles composed of amphiphilic materials with a core‐shell structure, have attracted great attention in recent years. Polymeric micelles in the range of several tens to hundreds of nanometers can be prepared, regulated, and modified relatively easily. The outer hydrophilic segments can prolong the in vivo lifetime of siRNA to achieve effective accumulation in tumors and can also be modified with cationic charges that interact electrostatically with siRNA and be introduced with different moieties to target specific cells. The inner cores can improve the stability of micelles and serve as payloads for hydrophobic drugs. Here, the barriers impeding siRNA delivery, the different polymeric micelles of siRNA developed to date, their gene silencing or therapeutic activity, and advanced applications for the co‐delivery of drugs and siRNA by these delivery systems are reviewed.     

Synthesis, physicochemical and biological properties of oligonucleotides incorporated with amino-isonucleosides

Antisense oligonucleotides(ASONs) and siRNAs have been applied extensively for the regulation of cellular and viral gene expression,and RNAi is currently one of the most promising new approaches for anti-tumor and anti-viral therapy.In order to improve bioactivity properties and physicochemical properties of siRNA,we synthesized a novel class of ASONs II-VII incorporated with amino-isonucleoside(isoA1 and isoA2) for investigation on basic physicochemical properties.Then we designed amino-isonucleoside(isoA1,isoA2 and isoT1) incorporated siRNA 2-7.Some meaningful results have been obtained from the physicochemical property experiments in ASONs.In RNAi potency experiments,we investigated RNAi potency of each strand of the siRNA.These amino-isonucleosides incorporated siRNAs showed promising bioactivity properties and had position specificity.Reduced off target effect from sense strand loading in siRNA application was observed.     

Polymeric micelleplexes for improved photothermal endosomal escape and delivery of siRNA

Effective endosomal escape is required for practical application of nucleic acid therapeutics. In this study, we prepared siRNA micelleplexes with photothermally triggered endosomal escape and improved gene silencing activity in vitro. The micelleplexes were prepared from cholesterol‐modified and CXCR4‐inhibiting poly(amido amine)s (PAMD‐Ch). Near‐infrared dye IR780 was encapsulated in cationic PMAD‐Ch micelles, which then were used to form IR780 micelleplexes with siRNA. The micelleplexes displayed improved gene silencing efficiency upon laser irradiation, which was attributed to enhanced endosomal escape because of the photothermal effects of the encapsulated IR780. The IR780 micelleplexes retained the CXCR4 antagonism and inhibition of cancer cell invasion of the parent PAMD. Overall, this study validates codelivery of IR780 in siRNA micelleplexes as promising photothermally controlled siRNA delivery approach.     

一种新型聚乙烯亚胺(PEI)载体的制备及表征

设计一种新型的用于传输小干扰核糖核酸(siRNA)聚乙烯亚胺-聚类丙交酯功能聚合物。首先合成一类含功能基团羧基的丙交酯衍生物,对其进行了1 H NMR、GPC、DSC表征,功能基团的密度可以通过与丙交酯共聚的单体的物质的量来调控,利用羧基与聚乙烯亚胺(PEI)分子上的氨基偶合,将小分子量PEI通过共价键连接到可生物降解的高分子主链骨架上,这种方法提供了一条途径来解决分子量与细胞毒性以及转染效率之间相互矛盾的关系。本文进一步研究了此体系在负载siRNA前后粒径及zeta电位的变化,颗粒粒径分布在50~500nm之间,Zeta电位在-9~-35mV之间。     

Engineered Hsp Protein Nanocages for siRNA Delivery

The efficient delivery of small interfering RNA (siRNA) to tumor cells still remains a great challenge. Of the various nanocarriers, protein nanocages have attracted extensive interest due to their unique structure and suitable characteristics derived from their proteinaceous nature. However, most reported protein nanocages that are developed are based on virus capsid proteins, which may raise safety concerns, including those related to gene mutation and carcinogenesis. The development of nonviral protein‐based systems for siRNA delivery is greatly needed. In this study, a novel siRNA delivery system based on heat shock protein (Hsp) nanocages is developed by a genetic engineering method. The delivery system could condense siRNA into stable complexes and protect the condensed siRNA from degradation. A cellular uptake analysis shows that siRNA is introduced into tumor cells mediated by Hsp‐R9 nanocages. Green fluorescent protein (GFP) expression in HeLa‐EGFP cells is significantly downregulated by Hsp‐R9/siRNA complexes. The results indicate that Hsp nanocages may be a good platform for siRNA delivery into tumor cells.     

Potential Use of Dendrimer/α-Cyclodextrin Conjugate as a Novel Carrier for Small Interfering RNA (siRNA)

RNA interference (RNAi) is the mechanism of gene silencing-mediated messenger RNA degradation by small interference RNA (siRNA), which becomes a powerful tool for genetic analysis and novel gene therapy. However, one of the major obstacles for siRNA delivery is the difficulty to cross the biological membrane due to its hydrophilicity and high molecular weight. We evaluated the potential use of the starburst polyamidoamine dendrimer (generation 3) conjugate with α-cyclodextrin (α-CyD) having an average degree of substitution of 2.4 (α-CDE conjugate) as a siRNA carrier for RNAi. The ternary complex composed of pGL2 control vector (pDNA)/pGL2 siRNA/α-CDE conjugate showed higher pGL2 siRNA sequence-specific gene silencing effects without off-target effects than those of commercial transfection reagents such as Lipofectamine™2000 (LP), TransFast™ (TF) and Lipofectin™ (LF). These results suggest that α-CDE conjugate has the potential to be a novel carrier for siRNA.     

A novel entry to 2′-O-aminopropyl modified nucleosides amenable for further modifications

2′-O-aminopropyl modified 4,6-difluoro-substituted benzimidazole nucleosides were synthesized in a two-step synthesis via Michael reaction and a Raney-nickel catalyzed reduction in high yields. These building blocks were used as a starting point for the conjugation of different carboxylic acids to enhance the lipophilicity or cationic character of oligonucleotides when used in biological assays or medical applications.     

Sequence‐Defined Oligomers from Hydroxyproline Building Blocks for Parallel Synthesis Applications

The functionality of natural biopolymers has inspired significant effort to develop sequence‐defined synthetic polymers for applications including molecular recognition, self‐assembly, and catalysis. Conjugation of synthetic materials to biomacromolecules has played an increasingly important role in drug delivery and biomaterials. We developed a controlled synthesis of novel oligomers from hydroxyproline‐based building blocks and conjugated these materials to siRNA. Hydroxyproline‐based monomers enable the incorporation of broad structural diversity into defined polymer chains. Using a perfluorocarbon purification handle, we were able to purify diverse oligomers through a single solid‐phase extraction method. The efficiency of synthesis was demonstrated by building 14 unique trimers and 4 hexamers from 6 diverse building blocks. We then adapted this method to the parallel synthesis of hundreds of materials in 96‐well plates. This strategy provides a platform for the screening of libraries of modified biomolecules.     

Acid Sensitive Polymeric Micelles Combining Folate and Bioreducible Conjugate for Specific Intracellular siRNA Delivery

An efficiently siRNA transporting nanocarrier still remains to be developed. In this study, utilizing the dual stimulus of acid tumor extracellular environment and redox effect of glutathione in the cytosol, a new siRNA transporting system combining triple effects of folate targeting, acid sensitive polymer micelles, and bio‐reducible disulfide bond linked siRNA‐cell penetrating peptides (CPPs) conjugate is developed to suppress c‐myc gene expression of breast cancer (MCF‐7 cells) both in vitro and in vivo. Subsequent research demonstrates that the vesicle has particle size of about 100 nm and siRNA entrapment efficiency of approximately 80%. In vitro studies verified over 90% of encapsulated siRNA‐CPPs can be released and the vesicle shows higher cellular uptake in response to the tumorous zone. Determination of gene expression at both mRNA and protein levels indicates the constructed vesicle exhibited enhanced cancer cell apoptosis and improved therapeutic efficacy in vitro and in vivo.