Aperture Modulation of Isoreticular Metal Organic Frameworks for Targeted Antitumor Drug Delivery

The introduction of different pore diameters in metal organic frameworks (MOFs) could adjust their drug delivery performance. MOFs with customized structures have potential application value in targeted drug delivery. However, no research on this topic has been found so far. In this report, isoreticular metal organic frameworks (IRMOFs) have been taken as a typical case of tailor-made MOFs, the pore size of which is enlarged (average BJH pore sizes of about 2.43, 3.06, 5.47, and 6.50 nm were determined for IRMOF-1, IRMOF-8, IRMOF-10, and IRMOF-16, respectively), emphasizing the relationship between pore size and model drugs (Oridonin, ORI) and clarifying its potential working mechanism. IRMOF-1, whose pore size matches the size of ORI, has an outstanding drug loading capacity (57.93% by wt) and release profile (about 90% in 24 h at pH 7.4). IRMOF-1 was further coated with polyethylene glycol (PEG) modified with a cell penetrating peptide (CPP44) bound to M160 (CD163L1) protein for targeting of hepatic tumor lines. This nanoplatform (CPP44-PEG@ORI@IRMOF-1) exhibited acid-responsive drug release behavior (37.86% in 10 h at pH 7.4 and 66.66% in 10 h at pH 5.5) and significantly enhanced antitumor effects. The results of cell targeting and in vivo animal imaging indicated that CPP44-PEG@ORI@IRMOF-1 may serve as a tumor-selective drug delivery nanoplatform. Toxicity assessment confirmed that PEGylated IRMOF-1 did not cause organ or systemic toxicity. Furthermore, it is encouraging that the IRMOF-based targeted drug delivery system with pore size modulation showed rapid clearance (most administered NPs are metabolized from urine and feces within 1 week) and avoided accumulation in the body, indicating their promise for biomedical applications. This MOF-based aperture modulation combined with a targeted modification strategy might find broad applications in cancer theranostics. Thus, it is convenient to customize personalized MOFs according to the size of drug molecules in future research.