Newly Emerging Theranostic Agents for Simultaneous Cancertargeted Imaging and Therapy

The development of multifunctional theranostic agents has become an intriguing venture for personalized oncology, because they can integrate tumor diagnosis and therapy. One approach explored to obtain such multifunctional theranostic agents is through the chemical conjugation of anticancer drugs and contrast agents with various cancer-targeted ligands. The other approach is based on the nanoplatform, in which cancer-targeted nanostructures achieve simultaneous cancer specific detection and therapeutics either by EPR effect or by conjugation of target ligands. Interestingly, a newly emerging strategy from multifunctional small molecules to develop cancertargeted theranostic agents has been reported recently. In consideration of the urgent need and rapid development of theranostic agents in cancer therapy, herein we review the currently adopted and newly emerging approaches for their preparation, and highlight the promises and challenges in each approach, hoping to offer useful insights in developing more specific and efficient cancer theranostic agents suitable for clinical use.