Using cell-based aptamer selection, we have developed a strategy to use the differences at the molecular level between any two types of cells for the identification of molecular signatures on the surface of targeted cells. A group of aptamers have been generated for the specific recognition of leukemia cells. The selected aptamers can bind to target cells with an equilibrium dissociation constant ( K _d ) in the nanomolar-to-picomolar range. The cell-based selection process is simple, fast, straightforward, and reproducible, and, most importantly, can be done without prior knowledge of target molecules. The selected aptamers can specifically recognize target leukemia cells mixed with normal human bone marrow aspirates and can also identify cancer cells closely related to the target cell line in real clinical specimens. The cell-based aptamer selection holds a great promise in developing specific molecular probes for cancer diagnosis and cancer biomarker discovery.

Abnormal enzymatic activities are directly related to the development of cancers. Identifying the location and expression levels of these enzymes in live cancer cells have considerable importance in early-stage cancer diagnoses and monitoring the efficacy of therapies. Small-molecule fluorescent probes have become a powerful tool for the detection and imaging of enzymatic activities in biological systems by virtue of their higher sensitivity, nondestructive fast analysis, and real-time detection abilities. Moreover, due to their structural tailorability, numerous small-molecule enzymatic fluorescent probes have been developed to meet various demands involving real-time tracking and visualizing different enzymes in live cancer cells or in vivo. In this review, we provide an overview of recent advances in small-molecule enzymatic fluorescent probes mainly during the past decade, including the design strategies and applications for various enzymes in live cancer cells. We also highlight the challenges and opportunities in this rapidly developing field of small-molecule fluorescent probes for interventional surgical imaging, as well as cancer diagnosis and therapy.

Investigation of metal–organic frameworks (MOFs) for biomedical applications has attracted much attention in recent years. MOFs are regarded as a promising class of nanocarriers for drug delivery owing to well-defined structure, ultrahigh surface area and porosity, tunable pore size, and easy chemical functionalization. In this review, the unique properties of MOFs and their advantages as nanocarriers for drug delivery in biomedical applications were discussed in the first section. Then, state-of-the-art strategies to functionalize MOFs with therapeutic agents were summarized, including surface adsorption, pore encapsulation, covalent binding, and functional molecules as building blocks. In the third section, the most recent biological applications of MOFs for intracellular delivery of drugs, proteins, and nucleic acids, especially aptamers, were presented. Finally, challenges and prospects were comprehensively discussed to provide context for future development of MOFs as efficient drug delivery systems.