Chitosan-coated mesoporous MIL-100(Fe) nanoparticles as improved bio-compatible oral nanocarriers

Abstract

Nanometric biocompatible Metal-Organic Frameworks (nanoMOFs) are promising candidates for drug delivery. Up to now, most studies have targeted the intravenous route, related to pain and severe complications; whereas nanoMOFs for oral administration, a commonly used non-invasive and simpler route, remains however unexplored. We propose here the biofriendly preparation of a suitable oral nanocarrier based on the benchmarked biocompatible mesoporous iron(III) trimesate nanoparticles coated with the bioadhesive polysaccharide chitosan (CS). This method does not hamper the textural/structural properties and the sorption/release abilities of the nanoMOFs upon surface engineering. The interaction between the CS and the nanoparticles has been characterized through a combination of high resolution soft X-ray absorption and computing simulation, while the positive impact of the coating on the colloidal and chemical stability under oral simulated conditions is here demonstrated. Finally, the intestinal barrier bypass capability and biocompatibility of CS-coated nanoMOF have been assessed in vitro, leading to an increased intestinal permeability with respect to the non-coated material, maintaining an optimal biocompatibility. In conclusion, the preservation of the interesting physicochemical features of the CS-coated nanoMOF and their adapted colloidal stability and progressive biodegradation, together with their improved intestinal barrier bypass, make these nanoparticles a promising oral nanocarrier.

Figure 1

(a) Comparison of TFY and TEY Fe L_2,3-edge XANES of the nano-MOFs before (NP) and after (NP-CS) CS absorption. (b) Reference Fe L_2,3-edge XANES in three different model compounds with different number of d–electrons, coordination numbers and with different formal charges, i.e. metal (Fe⁰), FeCl₂ (Fe^II) and Fe₂O₃ (Fe^III). (c) XANES O K-edge spectra of the nano-MOFs (NP)- before and after CS absorption, using TFY detector.

Figure 2. Geometry optimized configuration for CS (here corresponding to 3 units linked through β-(1–4) bridges: 2 units of D-glucosamine and 1 of N-acetyl-D-glucosamine) and a metal cluster issued from MIL-100(Fe) NPs with 2 Fe^II and 1 Fe^III.

Figure 3. Release of Rh-CS in water (black), SIF (blue), lis-SIF-panc (green) and HBSS (red) at 37 °C as a function of time.

The maximum of release of 100 wt% corresponds to the total release of the total amount of CS initially coating the NPs.

Figure 4. Degradation kinetics of uncoated (black) and coated (red) MIL-100(Fe) NPs in water, HBSS, DMEM, PBS, SIF, lis-SIF and lis-SIF-panc at 37 °C as a function of time.

Figure 5. Confocal microscopy images of Caco-2 cells containing uncoated and CS-coated MIL-100(Fe) NPs observed by iron self-reflection signal (green channel) and the nucleus stained by DAPI (blue channel).

The images have been taken at different times: 0.5, 2.5 and 24 h. Moreover, the controls were obtained with cells (control) after 24 h. In all the cases, the scale bar corresponded to 25 μm. All the images were taken at 63X.