No abstract

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.

Hydrogen sulphide (H 2 S) is a gaseous signalling agent that has important regulatory roles in many biological systems but remains difficult to measure in living biological specimens. Here we introduce a new method for highly sensitive sulphide mapping in live cells via singleparticle plasmonic spectral imaging that uses Au-Ag core-shell nanoparticles as probes. This strategy is based on Ag 2 S formation-induced spectral shifts of the nanoprobes, which is not only highly selective towards sulphide but also shows a linear logarithmic dependence on sulphide concentrations from 0.01 nM to 10 mM. A theoretical model was established that successfully explained the experimental observations, suggesting that the local sulphide concentration as well as its oscillations can be determined indirectly from kinetic measurements of the spectral shifts of the nanoprobes. We demonstrated for the first time the realtime mapping of local variations of sulphide levels in live cells with nM sensitivity.

The complete three-dimensional orientations of single gold nanorods (AuNR) were successfully resolved by using a standard optical darkfield microscope through deciphering the field distribution pattern in the slightly defocused darkfield images. The resulting images depend on the aspect ratio of the AuNR, the numerical aperture of the objective, the defocusing distance, and the polarization direction of the incident radiation. Interpretation of the observed images is facilitated by comparing them with a series of simulated images with different parameters. The experimental data matched well with the simulated results, and the reliability of this technique was further verified with polarization modulation experiments. Since deconvolution can be performed off-line after the images are recorded, this approach essentially allows video-rate data acquisition. The convenient, reliable and rapid angle-resolving capability should enable broad applications in imaging studies in many scientific fields.

The advent of SELEX (systematic evolution of ligands by exponential enrichment) technology has shown the ability to evolve artificial ligands with affinity and specificity able to meet growing clinical demand for probes that can, for example, distinguish between the target leukemia cells and other cancer cells within the matrix of heterogeneity, which characterizes cancer cells. Though antibodies are the conventional and ideal choice as a molecular recognition tool for many applications, aptamers complement the use of antibodies due to many unique advantages, such as small size, low cost, and facile chemical modification. This Minireview will focus on the novel applications of aptamers and SELEX, as well as opportunities to develop molecular tools able to meet future clinical needs in biomedicine.