Inorganic Nanoparticles for Cancer Therapy: A Transition from Lab to Clinic

Background: Inorganic nanoparticles (NPs) including those derived from metals (e.g., gold, silver), semiconductors (e.g., quantum dots), carbon dots, carbon nanotubes, or oxides (e.g., iron oxide), have been deeply investigated recently for diagnostic and therapeutic purposes in oncology. Compared to organic nanomaterials, inorganic NPs have several advantages and unique characteristics for better imaging and drug delivery. Still, only a limited number of inorganic NPs are translated into clinical practice. Method: In this review, we discuss the progression of inorganic NPs for cancer therapy and imaging, focusing our attention on opportunities, limitations and challenges for the main constituting nanomaterials, including metallic and magnetic NPs. In particular, the pre-clinical and clinical trials from the bench toward the clinic are here investigated. Results: Over the last few decades, the development of wide range of NPs with the ability to tune size, composition and functionality, has provided an excellent resource for nanomedicine. Inorganic NPs provide a great opportunity as drug carriers, due to the easy modification of targeting molecules, the control of drug release by different stimuli, and the effective delivery to target sites, thus resulting in having an improved therapeutic efficacy and in reducing side effects. Inorganic NPs are investigated in preclinical and clinical studies for the detection, diagnosis and treatment of many diseases. The stability of inorganic NPs offers a potential advantage over the traditional delivery methods. Inorganic NPs could enhance and improve current imaging and diagnostic techniques, such as MRI or PET. Even though, they have not yet been approved for drug delivery applications, their ability to respond to external stimuli is now widely investigated in clinic. Conclusion: The successful translation of inorganic NPs to the clinic requires the development of a simple, safe, cost-effective, ecofriendly mode of synthesis, and a better understanding of the safety mechanisms, biodistribution and the pharmacokinetics of NPs. However, more attention should be given to concerns on long-term toxicity, carcinogenesis, immunogenicity, inflammation and tissue damage. Although, some inorganic NPs, which were apparently promising in the preclinical phase, were found not to be successful when translated to the clinic, several encouraging NPs are currently being developed for treatment and cancer care and for a wide variety of other diseases.