Controlling the Adsorption and Release of Ocular Drugs in Metal–Organic Frameworks: Effect of Polar Functional Groups

Abstract

A series of UiO-66 materials with different functional groups (−H, −NH2, and −NO2) have been evaluated for the adsorption and release of a common ocular drug such as brimonidine tartrate. UiO-66 samples were synthesized under solvothermal conditions and activated by solvent exchange with ethanol. Experimental results suggest that the incorporation of surface functionalities gives rise to the development of structural defects (missing linker defects) but without altering the basic topology of the UiO-66 framework. These defects improve the adsorption performance of the parent metal–organic framework (MOF), while the bulkier functionalities infer slower release kinetics, with the associated benefits for prolonged delivery of brimonidine. Among the evaluated MOFs, defective UiO-66-NO2 can be proposed as the most promising candidate due to the combination of a larger brimonidine volumetric uptake (680 mg/cm3), a prolonged delivery (period of up to 25 days), a small particle size, and a larger instability. Contrariwise, at high concentrations UiO-66-NO2 has higher toxicity toward human retinal pigment epithelium cells (ARPE-19) compared to the pure and NH2-functionalized UiO-66.

Porous Coordination Polymer MOF-808 as an Effective Catalyst to Enhance Sustainable Chemical Processes

“…In fact, the experimental diffractograms prove the preparation of both the MOF-808 and UiO-66-NH2 materials with the expected solid-state structure [39,44]. As expected, the thermogravimetric analysis profiles of the two materials are like those previously reported and confirm the thermal stability of MOF-808 up to about 500 °C and up to 400 °C for UiO-66-NH2 (Figure 5d) [45,46]. The FT-IR and FT-Raman spectra obtained for both the Zr-based MOF-based materials reveal the main vibrational band characteristics as expected from the two MOF structures (Figure 5a,b; spectra shown in the 1900-400 cm −1 wavenumber region) [42,43].…”

“…In fact, the experimental diffractograms prove the preparation of both the MOF-808 and UiO-66-NH 2 materials with the expected solid-state structure [39,44]. As expected, the thermogravimetric analysis profiles of the two materials are like those previously reported and confirm the thermal stability of MOF-808 up to about 500 • C and up to 400 • C for UiO-66-NH 2 (Figure 5d) [45,46]. The micrographs obtained by SEM for the two materials in random zones of the samples reveal agglomerated particles, apparently with superior crystalline regularity in the UiO-66-NH2 sample, most probably because of its solvothermal preparation instead of the room temperature preparation of MOF-808 (Figure 6).…”

Friends or Foes: Fundamental Principles of Th-Organic Scaffold Chemistry Using Zr-Analogs as a Guide

“…Broad chemical and thermal stability is one of the highly sought-after traits in the field of metal−organic frameworks (MOFs 1−35 ), which shapes the landscape of possible applications with a main focus on specific MOF classes, including those based on zirconium. 36−46 Indeed, Zr-MOFs (e.g., possessing fcu- 47,48 and ftw-type 49,50 topologies) exhibit excellent thermostability up to 500 °C, 47 possess chemical stability across a wide pH range from 2 to 12, 48 and demonstrate exceptional resilience even under 423 Gy/min γ radiation. 51 At the same time, the recent and rapidly growing interest in the development of fuel cycle reactors, radiological daughters for nuclear medicine, and efficient nuclear stockpile recycling serves as the driving force for translating the wealth of fundamental knowledge acquired for Zr-MOFs to thoriumbased analogs.…”

“…Broad chemical and thermal stability is one of the highly sought-after traits in the field of metal–organic frameworks (MOFs − ), which shapes the landscape of possible applications with a main focus on specific MOF classes, including those based on zirconium. − Indeed, Zr-MOFs (e.g., possessing fcu- , and ftw-type , topologies) exhibit excellent thermostability up to 500 °C, possess chemical stability across a wide pH range from 2 to 12, and demonstrate exceptional resilience even under 423 Gy/min γ radiation . At the same time, the recent and rapidly growing interest in the development of fuel cycle reactors, radiological daughters for nuclear medicine, and efficient nuclear stockpile recycling serves as the driving force for translating the wealth of fundamental knowledge acquired for Zr-MOFs to thorium-based analogs. − Since the onset of research focusing on Th-based materials, Zr-frameworks have been considered to be the closest analogs due to the shared metal oxidation state (+4), high Lewis acidity, formation of strong coordination bonds to carboxylate-based organic linkers, and oxophilicity comparable to thorium. − However, in contrast to a plethora of publications (>3600) focusing on Zr-MOFs, only around 100 exist for their Th-based counterparts (Figure ).…”

Commonly Neglected Ester Groups Enhanced Microwave Absorption

“…On the other hand, Oxygen functional groups and structural flaws are invariably present together. The presence of oxygen functional groups that opposed to atoms invariably results in more pronounced irregular flaws in the structure, [15][16][17] favoring in-plane topological defects (dislocations, crystal planes, etc.). These structural flaws induce in situ Gaussian curvature, which modifies the rehybridized electron orbitals and bond lengths and might cause more pronounced electron redistribution.…”