Pathological environment directed in situ peptidic supramolecular assemblies for nanomedicines

Editorial: Special issue on advances in nanomedicine

Nanomaterials are being increasingly used to develop new methods of disease diagnosis and treatment, thereby providing novel paradigms to break through the current limitations of medicine. However, there is still a long way toward the complete revolution for nanomedicine in the diagnosis and treatment of diseases. As nanoparticles are highly complex products and difficult to characterize, there are still many challenges. This special issue on Advances in Nanomedicine includes a series of topical reviews and original research articles that highlight the recent advances in diagnosis and therapy of nanomaterials.

Intracellular fluorogenic supramolecular assemblies for self-reporting bioorthogonal prodrug activation

A visual drug delivery system (DDS) is urgently needed for precision medicine. DDS-mediated bioorthogonal prodrug activation strategies have demonstrated remarkable advantages in enlarging a therapeutic index via the alleviation of adverse drug reactions. However, the events of bioorthogonal prodrug activation remain inaccessible. Here, we construct a self-reporting bioorthogonal prodrug activation system using fluorescence emission to interpret prodrug activation events. In designed reactive oxygen species (ROS)-instructed supramolecular assemblies, the bioorthogonal reaction handle of tetrazine carries a dual role as fluorescence quencher and prodrug activator. The subsequent inverse-electron-demand Diels-Alder (IEDDA) reaction simultaneously liberates fluorescence and active drugs, which form a linear relationship. Differentiated by their cellular redox status, ROS-instructed supramolecular assemblies form selectively in both tumor cells and cell spheroids. Upon prodrug treatment, the brightness of fluorescence reflects the liberation of active drugs, which further correlates with the cell survival rate. Therefore, a fluorescence-based visualizable DDS (VDDS) for bioorthogonal prodrug activation is demonstrated, which should be useful to elucidate the multi-step processes in drug delivery and determine prodrug activation efficacy.

Enzyme-mediated intratumoral self-assembly of nanotheranostics for enhanced imaging and tumor therapy

Enzyme-mediated intratumoral self-assembled (EMISA) nanotheranostics represent a new class of smart agents for combined imaging and therapy of cancer. Cancer cells overexpress various enzymes that are essential for high metabolism, fast proliferation, and tissue invasion and metastasis. By conjugating small molecules that contain an enzyme-specific cleavage site to appropriate chemical linkers, it is possible to induce self-assembly of nanostructures in tumor cells having the target enzyme. This approach of injecting small theranostic molecules that eventually become larger nanotheranostics in situ avoids some of the major limitations that are encountered when injecting larger, pre-assembled nanotheranostics. The advantage of EMISA nanotheranostics include the avoidance of nonspecific uptake and rapid clearance by phagocytic cells, increased cellular accumulation, reduced drug efflux and prolonged cellular exposure time, all of which lead to an amplified imaging signal and therapeutic efficacy. We review here the different approaches that can be used for preparing EMISA-based organic, inorganic, or organic/inorganic hybrid nanotheranostics based on noncovalent interactions and/or covalent bonding. Imaging examples are shown for fluorescence imaging, nuclear imaging, photoacoustic imaging, Raman imaging, computed tomography imaging, bioluminescent imaging, and magnetic resonance imaging. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Biology-Inspired Nanomaterials > Peptide-Based Structures.

Sensitive and Enzyme-Free Pathogenic Bacteria Detection Through Self-Circulation of Molecular Beacon

This research exhibits the design of a feasible, enzyme-free and sensitive fluorescent sensing assay for the detection of Staphylococcus aureus (S. aureus), using self-circulation of molecular beacons. With protein A on S. aureus as identifying target, the capture probe binds on the surface of S. aureus based on interaction between its aptamer section and protein A. Recognition of protein A by aptamer section in capture probe leads to allosterism of capture probe, exposing initiator section to activate the following self-circulation. After multiple circulation-based signal amplification, the method exhibits a favorable detection sensitivity and shows a promising prospect for the keratitis-related pathogenic bacteria detection. The highlights of the sensing assay are as follows: (i) capture probe is designed with aptamer section which endows the method a high selectivity; (ii) signal of bacteria is converted to nucleic acid signal after recognition of target bacteria by capture probe; and (iii) high sensitivity of method is derived from the self-circulation process. Therefore, we believe that the strategy can provide a useful platform for target bacteria detection and thus contribute to the diagnosis of infectious diseases.