SPIONs: Superparamagnetic iron oxide-based nanoparticles for the delivery of microRNAi-therapeutics in cancer

Non-coding RNA (ncRNA)-based therapeutics that induce RNA interference (RNAi), such as microRNAs (miRNAs), have drawn considerable attention as a novel class of targeted cancer therapeutics because of their capacity to specifically target oncogenes/protooncogenes that regulate key signaling pathways involved in carcinogenesis, tumor growth and progression, metastasis, cell survival, proliferation, angiogenesis, and drug resistance. However, clinical translation of miRNA-based therapeutics, in particular, has been challenging due to the ineffective delivery of ncRNA molecules into tumors and their uptake into cancer cells. Recently, superparamagnetic iron oxide-based nanoparticles (SPIONs) have emerged as highly effective and efficient for the delivery of therapeutic RNAs to malignant tissues, as well as theranostic (therapy and diagnostic) applications, due to their excellent biocompatibility, magnetic responsiveness, broad functional surface modification, safety, and biodistribution profiles. This review highlights recent advances in the use of SPIONs for the delivery of ncRNA-based therapeutics with an emphasis on their synthesis and coating strategies. Moreover, the advantages and current limitations of SPIONs and their future perspectives are discussed.