Stimuli-responsive hybrid nanocarriers developed by controllable integration of hyperbranched PEI with mesoporous silica nanoparticles for sustained intracellular siRNA delivery

Abstract

Small interfering RNA (siRNA) is a highly potent drug in gene-based therapy with the challenge being to deliver it in a sustained manner. The combination of mesoporous silica nanoparticles (MSNs) and polycations in the confined pore space allows for incorporation and controlled release of therapeutic siRNA payloads. We hereby constructed MSNs with expanded mesopores and pore-surface-hyperbranched poly(ethyleneimine) (PEI) tethered with redox-cleavable linkers that could carry a high payload of siRNA (120 mg·g⁻¹). The developed nanocarriers were efficiently taken up by cancer cells and were subsequently able to escape to the cytoplasm from the endosomes, most likely owing to the integrated PEI. Triggered by the intracellular redox conditions, the siRNA was sustainably released inside the cells over a period of several days. Functionality of siRNAs was demonstrated by using cell-killing siRNA as cargo. Despite not being the aim of the developed system, in vitro experiments using cell-killing siRNAs showed that the efficacy of siRNA transfection was comparable to the commercial in vitro transfection agent Lipofectamine. Consequently, the developed MSN-based delivery system offers a potential approach to hybrid nanocarriers for more efficient and long-term siRNA delivery and, in a longer perspective, in vivo gene silencing for RNA interference (RNAi) therapy.

Keywords:

• mesoporous silica nanoparticles
• RNAi therapy
• siRNA delivery
• stimuli-responsive drug release
• hybrid nanocarriers

Supplementary materials

Figure S1 In vitro cell viability of MSN and MSN-PEI nanoparticles performed with WST-1 assay.

Abbreviations: MSN, mesoporous silica nanoparticle; PEI, poly(ethyleneimine).

Figure S2 Comparison of cellular internalization of MSN and MSN-PEI nanoparticles.

Abbreviations: MSN, mesoporous silica nanoparticle; PEI, poly(ethyleneimine).

Figure S3 The gene knockdown efficiency by siRNA delivery through MSN nanocarriers.

Notes: The analysis was performed by colony area counting ImageJ plugin for proliferating cell colonies upon 120 h treatment with MSN nanocarriers and Lipofectamine as transfection control.

Abbreviations: siRNA, small interfering RNA; MSN, mesoporous silica nanoparticle.

Figure S4 The gene knockdown efficiency by siRNA delivery through MSN nanocarriers.

Notes: The analysis was performed by calculating colony intensity of surviving colonies after 120 h treatment with MSN nanocarriers and Lipofectamine as transfection control in the presence of positive and negative controls. The analysis was performed by crystal violet staining of cell colonies and ImageJ plugin “ColonyArea”.

Abbreviations: siRNA, small interfering RNA; MSN, mesoporous silica nanoparticle.

Acknowledgments

The authors would like to acknowledge the technical assistance provided by Taina Kalevo-Mattila, Dr Anni Laine and Amanpreet Kaur from Cancer Cell Signalling group from Turku Centre of Biotechnology, University of Turku, and Åbo Akademi University, Finland. The authors are grateful for IncuCyte Imaging assistance by Tiina Kähkönen and Dr Yu Lan from Cell Biology and Anatomy, Faculty of Medicine, University of Turku. Dr Takahiro Deguchi, Laboratory of Biophysics, University of Turku, is acknowledged for data analysis of the co-localization experiment. The financial contributions from Jane and Aatos Erkko Foundation (DD, EC, JW, JMR), Sigrid Juselius Foundation (JW), Foundation for Finnish Cancer Institute (JW), Academy of Finland (projects #260599, 284542) (JMR), Suomen Kulttuurirahasto (DD), Forskarskolan vid Åbo Akademi (TGS), National Natural Science Foundation of China (NSFC, Grant No 51502027), Basic Advanced Research Project of Chongqing 572 (Grant No cstc2015jcyjA10051) (JZ) and the Doctoral Education Network in Materials Research at Åbo Akademi University (NP) are greatly acknowledged. EC thanks Agency for Management of University and Research Grants from Generalitat de Catalunya (AGAUR) for financial support through Beatriu de Pinos program (2014 BP_A 00132).

Author contributions

NP designed and performed the cellular studies and wrote the manuscript. JZ designed, synthesized and characterized the initial MSN nanocarriers and contributed in manuscript writing. DD, EC and TGS prepared MSN nanocarriers and performed siRNA loading at different stages of the experiments. TN helped with technical details with cellular studies and experimental design. JW and JMR conceived, designed and coordinated the study and assisted in manuscript writing. All authors read, commented and approved the final manuscript. All authors contributed toward data analysis, drafting and critically revising the paper and agree to be accountable for all aspects of the work.

Disclosure

The author reports no conflicts of interest in this work.