Herein, we detail an atomic-level investigation of the cutinase enzyme encapsulated within a model metal-organic framework (MOF) platform using quantum mechanics calculations and molecular dynamics simulations. Cutinase, when encapsulated in an isoreticularly expanded MOF-74 (cutinase@IRMOF-74-VI), was proven to maintain its structural stability at temperatures that would otherwise denature the enzyme in its unprotected native state. Hydrogen bonding and salt bridge interactions, most notably involving arginine residues at the surface of the enzyme, were critical for stabilizing cutinase within the pore channels of IRMOF-74-VI. The findings reported support the viability of enzyme encapsulation in a porous material by demonstrating that a model enzyme not only retains its structural integrity but also remains accessible and active under extreme and foreign conditions.
Chemotherapeutic agents used in treating certain cancer types operate in a non-selective manner tending to accumulate in normal, healthy tissue when high doses are used. To mitigate the toxicity effect resulting from this, there is an urgent need to develop active nano delivery systems capable of regulating optimal doses specifically to cancer cells without harming adjacent normal cells. Herein, we report a versatile nanoparticle - zeolitic imidazolate framework-8 (nZIF-8) - that is loaded with a chemotherapeutic agent (gemcitabine; GEM) and surface-functionalized with an autonomous homing system (Arg-Gly-Asp peptide ligand; RGD) via a straightforward, one-pot solvothermal reaction. Successful functionalization of the surface of nZIF-8 loaded GEM (GEM⊂nZIF-8) with RGD was proven by spectroscopic and electron microscopy techniques. This surface-functionalized nanoparticle (GEM⊂RGD@nZIF-8) exhibited enhanced uptake in human lung cancer cells (A549), compared with non-functionalized GEM⊂nZIF-8. The GEM⊂RGD@nZIF-8, experienced not only efficient uptake within A549, but also induced obvious cytotoxicity (75% at a concentration of 10 μg mL-1) and apoptosis (62%) after 48 h treatment when compared to the nanoparticle absent of the RGD homing system (GEM⊂nZIF-8). Most importantly, this surface-functionalized nanoparticle was more selective towards lung cancer cells (A549) than normal human lung fibroblast cells (MRC-5) with a selectivity index (SI) of 3.98. This work demonstrates a new one-pot strategy for realizing a surface-functionalized zeolitic imidazolate framework that actively targets cancer cells via an autonomous homing peptide system to deliver a chemotherapeutic payload effectively.
To improve the selective delivery of cisplatin (Cis) to cancer cells, we report and establish the significance of active, targeting drug delivery nanosystems for efficient treatment of lung cancer. Specifically, pH-responsive nano-sized zeolitic imidazolate framework (nZIF-90) was synthesized, post-synthetically modified with an Arg-Gly-Asp peptide motif (RGD@nZIF-90), a known cancer cell homing peptide, and loaded with a large amount of Cis (RGD@Cis⊂nZIF-90). RGD@Cis⊂nZIF-90 was shown to be highly stable under physiological conditions (pH = 7.4) with framework dissociation occurring under slightly acidic conditions (pH = 5.0)-conditions relevant to tumor cells-from which 90% of the encapsulated Cis was released in a sustained manner. In vitro assays demonstrated that RGD@Cis⊂nZIF-90 achieved significantly better cytotoxicity (65% at 6.25 μg ml-1) and selectivity (selectivity index = 4.18 after 48 h of treatment) against adenocarcinoma alveolar epithelial cancer cells (A549) when compared with the unmodified Cis⊂nZIF-90 (22%). Cellular uptake using A549 cells indicated that RGD@Cis⊂nZIF-90 was rapidly internalized leading to significant cell death. After successfully realizing this nanocarrier system, we demonstrated its efficacy in transporting and delivering Cis to cancer cells.