pH-sensitive siRNA delivery systems

Enhanced siRNA delivery with novel smart chitosan-based formulations

This study aims to develop an innovative multifunctional and dual responsive drug formulation for precise siRNA delivery to breast cancer sites, addressing the challenges posed by conventional cancer treatments which often result in adverse side effects due to their non-specific nature. The formulation made by incorporating gold coated superparamagnetic iron oxide nanoparticles (Au-SPIONs) into chitosan microspheres, which were subsequently loaded with siRNA. Comprehensive characterization, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), Fourier-transform infrared spectroscopy (FTIR), and energy-dispersive X-ray spectroscopy (EDS) confirmed the formulation's favourable morphology, particle size distribution, chemical composition, and stability, indicating its strong potential for effective siRNA drug delivery applications. The developed formulation demonstrated siRNA encapsulation efficiencies ranging from 27.4 % to 88.6 % and loading capacity from 0.291 % to 1.59 %, these values particularly higher for medium molecular weight chitosan. These results were compared across different formulations, showing that variations in chitosan type and crosslinker concentration significantly influenced encapsulation efficiency and drug release profiles. Additionally, our results were compared to previous studies on chitosan microspheres encapsulating organic drugs and siRNA, where the developed system demonstrated similar encapsulation and release properties.. The type of chitosan and the choice of crosslinker significantly influenced the drug release patterns. Diverse release profiles across batches highlighted the necessity for precise formulation control. Incorporating SPIONs into chitosan microspheres presents a promising strategy for magnetically driven, site-specific drug delivery. The dual pH-responsive and magnetic properties enable rapid and targeted siRNA release, leveraging the acidic tumor microenvironment as an internal stimulus in addition to external magnetic stimuli. This novel combination of SPIONs, chitosan microspheres, and siRNA encapsulation represents a new approach for targeted drug delivery. While further research is needed to refine and optimize this approach, our study provides a proof of concept for advancing targeted cancer therapies.

Combining Inulin Multifunctional Polycation and Magnetic Nanoparticles: Redox-Responsive siRNA-Loaded Systems for Magnetofection

Superparamagnetic Iron Oxide Nanoparticles (SPIONs) are recognized as one of the most promising agents for theranostic applications. Among methods designed for siRNA delivery, magnetofection, that is, nucleic acid cell uptake under the influence of a magnetic field acting on magnetic nucleic acid vectors, is emerging as a unique approach to combining advantages such as strong improvement of the kinetics of the delivery process and the possibility of localizing nucleic acid delivery to an area where the magnetic field is applied. This paper reports on the preparation of siRNA loaded magnetoplexes—named ICD@SS@SPIONs/siRNA—by controlled crosslinking, in the presence of SPIONs, of the polycation INU-C-DETA, synthesized starting from the polysaccharide inulin by grafting diethylenetriamine and cystamine molecules. The obtained ICD@SS@SPIONs/siRNA have suitable chemical-physical characteristics to be employed for iv administration and are also able to release siRNA in a redox-triggered manner thanks to intracellular glutathione (GSH) mediated reduction of disulphide bridges formed during the crosslinking process. Moreover, ICD@SS@SPIONs/siRNA are able to produce magnetic targeting in vitro on breast cancer cells, without appreciable cyto- and hemo-toxic effects, in a wide range of concentrations. Finally, protein binding to nanoparticles revealed that obtained systems are potentially longer circulating and applicable as a smart multifunctional agents for cancer therapy.

Multifunctional pH-Sensitive Amino Lipids for siRNA Delivery

RNA interference (RNAi) represents a powerful modality for human disease therapy that can regulate gene expression signature using small interfering RNA (siRNA). Successful delivery of siRNA into the cytoplasm of target cells is imperative for efficient RNAi and also constitutes the primary stumbling block in the clinical applicability of RNAi. Significant progress has been made in the development of lipid-based siRNA delivery systems, which have practical advantages like simple chemistry and easy formulation of nanoparticles with siRNA. This review discusses the recent development of pH-sensitive amino lipids, with particular focus on multifunctional pH-sensitive amino lipids for siRNA delivery. The key components of these multifunctional lipids include a protonatable amino head group, distal lipid tails, and two cross-linkable thiol groups, which together facilitate the facile formation of stable siRNA-nanoparticles, easy surface modification for target-specific delivery, endosomal escape in response to the pH decrease during subcellular trafficking, and reductive dissociation of the siRNA-nanoparticles for cytoplasmic release of free siRNA. By virtue of these properties, multifunctional pH-sensitive lipids can mediate efficient cytosolic siRNA delivery and gene silencing. Targeted siRNA nanoparticles can be readily formulated with these lipids, without the need for other helper lipids, to promote systemic delivery of therapeutic siRNAs. Such targeted siRNA nanoparticles have been shown to effectively regulate the expression of cancer-related genes, resulting in significant efficacy in the treatment of aggressive tumors, including metastatic triple negative breast cancer. These multifunctional pH-sensitive lipids constitute a promising platform for the systemic and targeted delivery of therapeutic siRNA for the treatment of human diseases. This review summarizes the structure-property relationship of the multifunctional pH-sensitive lipids and their efficacy in in vitro and in vivo siRNA delivery and gene silencing.

Improving the in vivo therapeutic index of siRNA polymer conjugates through increasing pH responsiveness

Polymer based carriers that aid in endosomal escape have proven to be efficacious siRNA delivery agents in vitro and in vivo; however, most suffer from cytotoxicity due in part to a lack of selectivity for endosomal versus cell membrane lysis. For polymer based carriers to move beyond the laboratory and into the clinic, it is critical to find carriers that are not only efficacious, but also have margins that are clinically relevant. In this paper we report three distinct categories of polymer conjugates that improve the selectivity of endosomal membrane lysis by relying on the change in pH associated with endosomal trafficking, including incorporation of low pKa heterocycles, acid cleavable amino side chains, or carboxylic acid pH sensitive charge switches. Additionally, we determine the therapeutic index of our polymer conjugates in vivo and demonstrate that the incorporation of pH responsive elements dramatically expands the therapeutic index to 10-15, beyond that of the therapeutic index (less than 3), for polymer conjugates previously reported.