Development of MOF Reinforcement for Structural Stability and Toughness Enhancement of Biodegradable Bioinks

Abstract

Three-dimensional (3D) bioprinting is a technology that can precisely fabricate customized tissues and organs. Hydrogel materials that can embed living cells for use in 3D printing are called bioinks. However, there are only limited options of bioinks currently because they require the following features at once, such as printability, repetitive layer-by-layer stacking (stackability), structure stabilization, and biological properties. A polyurethane–gelatin double network hydrogel bioink was previously reported to own tunable modulus through changing the solid content, but cell viability at the high solid content is inevitably reduced. In the present study, the reinforcement effects of a metal–organic framework (MOF), zeolitic imidazolate framework-8 (ZIF-8), in the PUG bioink were evaluated. The printability, stackability, thermoresponsiveness, and shear-thinning behavior of the PUG-ZIF-8 composite hydrogels were examined. It was found that the PUG composite hydrogel containing 1250 μg/mL ZIF-8 crystals showed significant structural stability and modulus enhancement (∼2.5-fold). However, the PUG bioink containing 1250 μg/mL ZIF-8 crystals may lead to cell senescence or death. The cytocompatible concentration of ZIF-8 crystals in the bioink was about 875 μg/mL, and this concentration was much higher than the reported tolerable amount (∼50 μg/mL) of ZIF-8 for biomedical applications. The strong reinforcement effect of ZIF-8 and the drug-loading/sensing possibilities of MOFs may open new opportunities for using MOFs in 3D bioprinting applications.

3D Printing of Metal–Organic Framework-Based Ionogels: Wearable Sensors with Colorimetric and Mechanical Responses

“…For example, a MIG containing porphyrinic Zr-MOF should exhibit colorimetric and mechanical sensing functions. The incorporation of MOFs into hydrogels has been investigated in a few previous studies, − and the preparation of MOF-based ionogels has been reported previously. , However, hydrogels or ionogels competent for bifunctional or multifunctional sensing purposes with MOFs as the active materials have not been reported thus far, and the use of MOFs in DES-based ionogels has not been demonstrated.…”

“…3D printing or additive manufacturing is a flexible, versatile, and highly customizable technique for fabricating various objects with complex geometries by the layer-by-layer deposition of materials . Furthermore, 3D printing enables the rapid prototyping and manufacturing of lightweight and strong parts to overcome the limitations of traditional shaping techniques. − Various printing processes such as stereolithography, fused deposition modeling, and direct ink writing (DIW) have been developed to span different printing speeds, resolutions, and printable materials. , In particular, DIW has attracted tremendous attention due to the cost-effective fabrication of soft electronics and the use of a wide range of printable materials. , Because of such fantastic features, 3D printing has been considered as an attractive technique for shaping MOFs, as most MOFs in the powder form are less desirable for industrial-scale applications. , Several studies have demonstrated the 3D printing of pure MOFs or composite materials containing various MOFs, which are mostly constructed from copper-based or zinc-based nodes, for a range of applications. ,− Photocurable MOF–polymer composite inks also have been reported for shaping a range of MOFs and their subsequent use in chemical sensors . However, thus far, only two very recent examples have investigated the 3D printing of water-stable group-(IV)-metal-based MOFs. , Furukawa, Dhainaut, and co-workers have reported the 3D printing of a Zr-MOF, UiO-66-NH 2 , for gas storage and separation, and Boyer, Liang, and co-workers have utilized a porphyrinic Zr-MOF, MOF-525 (Zn), as a photocatalyst for polymerization during printing .…”

Nanoarchitectonics horizons: materials for life sciences

“…Our group recently explored the possibility of incorporating zeolitic imidazolate framework-8 with a biodegradable polyurethane hydrogel to improve the printability of a bioink. The composites were treated with calcium chloride for reinforcement and the developed bioink showed great biocompatibility when cultured with human mesenchymal stem cells and helped in the proliferation of cells 162 (Fig. 10).…”

Engineering of Metal–Organic Frameworks/Gelatin Hydrogel Composites Mediated by the Coacervation Process for the Capture of Acetic Acid

“…Such ability of gelatin for morphogenesis in soft conditions was mainly ascribed to its self-organization properties into triple helices and the existence of attractive interactions at the fluoroapatite/gelatin interface. Recently, the synthesis of MOF–gelatin hydrogels was mainly reported for bioapplications related to tissue engineering, wound healing, drug delivery, or bioimaging. − These composites were mainly prepared through the impregnation of preformed MOF particles into functionalized gelatin-based scaffolds or hybrid hydrogels or the physical gelation of gelatin in the presence of MOF particles eventually associated to electrospinning. − Although these hydrogels present interesting performance, the large majority of these composites suffers from a low porosity as a result of the very low amount of MOF (<10 wt %) and this strongly limits the exploitation of their physico-chemical properties and drug delivery properties. − A MOF–gelatin composite was also used for water purification with however a low MOF content and/or a low porosity . It should be noted that MOFs based on divalent cations (ZIF-8, ZIF-67, and HKUST) were mainly used for the processing of gelatin-based hydrogels while interfacing gelatin with MOFs of higher chemical stability such as the series of UiO-66­(Zr) was only rarely described .…”