Biodegradable Metal-Organic Framework-Based Microrobots (MOFBOTs).

Microrobots and metal-organic frameworks (MOFs) have been identified as promising carriers for drug delivery applications. While clinical applications of microrobots are limited by their low drug loading efficiencies and the poor degradability of the materials used for their fabrication, MOFs lack motility and targeted drug delivery capabilities. The combination of these two fields marks the beginning of a new era; MOF-based small-scale robots (MOFBOTs) for biomedical applications. Yet, biodegradability is a major hurdle in the field of micro- and nanoswimmers including small-scale robots. Here, a highly integrated MOFBOT that is able to realize magnetic locomotion, drug delivery, and selective degradation in cell cultures is reported for the first time. The MOF used in the investigations does not only allow a superior loading of chemotherapeutic drugs and their controlled release via a pH-responsive degradation but it also enables the controlled locomotion of enzymatically biodegradable gelatin-based helical microrobots under magnetic fields. The degradation of the integrated MOFBOT is observed after two weeks, when all its components fully degrade. Additionally, drug delivery studies performed in cancer cell cultures show reduced viability upon delivery of Doxorubicin within short time frames. This MOFBOT system opens new avenues for highly integrated fully biodegradable small-scale robots.

Competitive binding for triggering a fluorescence response in a hydrazodicarboxamide-based [2]rotaxane.

The design and synthesis of an interlocked receptor based on a hydrogen bonded [2]rotaxane containing a hydrazodicarboxamide binding site are reported. An anion recognition process with tetrabutylammonium benzoate triggers the submolecular translational movement of its benzylic amide macrocycle developing a progressive increase of the fluorescence intensity, effectively quenched at the original state. The binding of the anion competes with the hydrogen-bond-connected cyclic component for the bis(urea)-based station pushing it towards a stoppered alkyl chain. Moreover, this interlocked system is able to work as a molecular switch restoring its initial state in two ways, either by an ion exchange reaction or by a high yielding oxidation/reduction sequence.