Metal–Organic Frameworks at the Biointerface: Synthetic Strategies and Applications

Abstract

Many living organisms are capable of producing inorganic materials of precisely controlled structure and morphology. This ubiquitous process is termed biomineralization and is observed in nature from the macroscale (e.g., formation of exoskeletons) down to the nanoscale (e.g., mineral storage and transportation in proteins). Extensive research efforts have pursued replicating this chemistry with the overarching aims of synthesizing new materials of unprecedented physical properties and understanding the complex mechanisms that occur at the biological-inorganic interface. Recently, we demonstrated that a class of porous materials termed metal-organic frameworks (MOFs) can spontaneously form on protein-based hydrogels via a process analogous to natural matrix-mediated biomineralization. Subsequently, this strategy was extended to functional biomacromolecules, including proteins and DNA, which have been shown to seed and accelerate crystallization of MOFs. Alternative strategies exploit co-precipitating agents such as polymers to induce MOF particle formation thus facilitating protein encapsulation within the porous crystals. In these examples the rigid molecular architecture of the MOF was found to form a protective coating around the biomacromolecule offering improved stability to external environments that would normally lead to its degradation. In this way, the MOF shell mimics the protective function of a biomineralized exoskeleton. Other methodologies have also been explored to encapsulate enzymes within MOF structures, including the fabrication of polycrystalline hollow MOF microcapsules that preserve the original enzyme functionality over several batch reaction cycles. The potential to design MOFs of varied pore size and chemical functionality has underpinned studies describing the postsynthesis infiltration of enzymes into MOF pore networks and bioconjugation strategies for the decoration of the MOF outer surface, respectively. These methods and configurations allow for customized biocomposites. MOF biocomposites have been extended from simple proteins to complex biological systems including viruses, living yeast cells, and bacteria. Indeed, a noteworthy result was that cells encapsulated within a crystalline MOF shell remain viable after exposure to a medium containing lytic enzymes. Furthermore, the cells can adsorb nutrients (glucose) through the MOF shell but cease reproducing until the MOF casing is removed, at which point normal cellular activity is fully restored. The field of MOF biocomposites is expansive and rapidly developing toward different applied research fields including protection and delivery of biopharmaceuticals, biosensing, biocatalysis, biobanking, and cell and virus manipulation. This Account describes the current progress of MOFs toward biotechnological applications highlighting the different strategies for the preparation of biocomposites, the developmental milestones, the challenges, and the potential impact of MOFs to the field.

GraftFast Surface Engineering to Improve MOF Nanoparticles Furtiveness

“…In addition, if one considers the use of nanocarriers in the biomedical field, surface chemistry is known to play a crucial role, defining the chemical interactions among biological systems, and therefore states the final bioactivity of the material . Despite the extensive research on drug delivery systems (mainly liposomes, nanoemulsions, NPs, or micelles), the efficient and target release in the body of many drugs still remains an important challenge.…”

The Horizon of the Emulsion Particulate Strategy: Engineering Hollow Particles for Biomedical Applications

“…[35] As such, the produced capsules (as called colloidosomes) were the hollow structures that sealed with close-packed colloidal particles. [38] The assembly of nanobuilding blocks, offered the synergetic properties that can hardly be achieved by the individual microparticles or nanoparticles. In addition, the inherent gaps among the adsorbed particles constituted the porous shells with semipermeability and multicompartment encapsulation potential.…”

Electrospinning of Metal–Organic Frameworks for Energy and Environmental Applications

“…[56][57][58][59] A complete overview of the structuring of functional MOFs into hierarchical porous nanofibers by electrospinning for energy and environment applications has not yet been reported despite an increasing relevance of this class of materials. [56][57][58][59] A complete overview of the structuring of functional MOFs into hierarchical porous nanofibers by electrospinning for energy and environment applications has not yet been reported despite an increasing relevance of this class of materials.…”