Current status and future prospects of nanoscale metal-organic frameworks in bioimaging

The importance of the early-stage diagnosis and in situ monitoring of lesion regions and transportation of bioactive molecules has a pivotal effect on successful treatment, reducing side effects, and increasing the chances of survival in the case of serious diseases such as cancer. This strongly depends on the development of contrast agents and biomarkers together with the appropriate use of bioimaging techniques. Because of their exceptionally high surface area and porosity, nanoscale metal-organic frameworks (NMOFs) have been the subject of numerous studies in the biomedical domain as drug carriers, diagnostic and therapeutic agents, and biosensors. This review provides a summary of the recent advancements in the use of MOFs as nanoscale platforms for biomedical imaging via magnetic resonance (MR) imaging, computed tomography (CT), single-photon emission computed tomography (SPECT), fluorescence (FL) imaging, positron emission tomography (PET), photoacoustic (PA) imaging, and photothermal (PT) imaging modalities. Initially, we describe the principles of a specific imaging technique in each section, and then present the recent reports on MOFs for monomodal and multimodal imaging and the following information: (i) how to synthesize MOFs and modify their surface and (ii) their utilization in bioimaging or theranostic applications.