Self-healing metal-coordinated hydrogels using nucleotide ligands

Abstract

A supramolecular gel formed by Zn 2+ coordination with adenosine monophosphate (AMP) is reported. The adenine base, the monophosphate, and Zn 2+ are all important for gel formation. Mechanically disrupted gels can re-form upon centrifugation; applications of this gel for guest molecule entrapment are explored.Supramolecular gels have received considerable attention in recent years both as intriguing examples of self-assembly and as a means of creating smart materials.1-5 These gels are formed by noncovalent interactions to assemble supramolecular networks that trap solvent. 6Among the various types of supramolecular gels, those crosslinked by metal coordination are particular interesting. A few types of ligands have been developed for this purpose. For example, Craig and coworkers reported organopalladium−pyridine coordination. 16,17 Self-healing is a very interesting and useful feature of metal-coordinated gels; broken gel pieces can seal together with a mild mechanical force.Most of previously reported gels have to use specially designed ligands (e.g. incorporating a segment of PEG chain in addition to the metal ligand) to facilitate solvent trapping and gelation. Few reports are based on pure small molecule ligands. We reason that small molecule ligands will allow a higher metal density and thus may display different properties.Adenine, a purine nucleobase, is an important ligand in supramolecular chemistry. Adenine and its derivatives can form many complexes by coordination (with metal ions) and hydrogen bonding (with organic molecules). [18][19][20] With metal ions, it may form metalorganic frameworks, 21 and nanoparticles. [22][23][24][25] Recently, the gelation of adenine with tricarboxylic acid compounds was reported based on hydrogen bonding and π-π stacking. 26,27 We are interested in exploring whether it is possible to achieve gelation by metal coordination with adenine derivatives. Guanine and its derivatives have been mixed with monovalent metal ions to form gels based on quadruplex formation. 28-31 However, little has been done on adenine derivatives. Nanoparticles are the most common products. [22][23][24][25] Compared to nanoparticles, hydrogels are more attractive materials for making stimuli-responsible materials. [32][33][34][35][36][37][38][39] In this work, we communicate such an example, its property in guest molecule encapsulation, and healing.Since most previous work focused on adenine nucleobase and nucleoside as ligands, we started with nucleotide coordination in this work. Zn 2+ was chosen as the metal because it is a good Lewis acid that can be coordinated by a diverse range of ligands. In addition, it is a relatively biocompatible metal with low toxicity. We first studied the reaction between Zn 2+ and three kinds of nucleotides (AMP, GMP and CMP). TMP was not included since thymine has very weak coordination ability at neutral pH. Zn 2+ was respectively titrated into the solutions of AMP, GMP and CMP, and the UV-vis extinction at 550 nm was recorded. Since none of the products are c...

Magnetic Iron Oxide Nanoparticle Seeded Growth of Nucleotide Coordinated Polymers

“…39 Interestingly, precipitation occurred by increasing the HEPES concentration ( Figure 1A). With 35 mM HEPES, yellow precipitants formed in a few minutes after adding FeCl3.…”

“…36 We recently found that Zn 2+ coordinates with adenosine monophosphate (AMP) to form hydrogels. 39 In this work, since we are interested in coating iron oxide NPs, the most appropriate metal is iron. Since Fe 2+ is easy oxidized in air, we tested Fe 3+ first.…”

“…33 Nucleotide coordinated materials 4 were already used in preparing metal-organic frameworks, 34 NPs, 24,[35][36][37] and hydrogels. [38][39] We and others demonstrated that CPs are capable of adsorbing and entrapping a broad range of molecules. 24,35,39 Given the encapsulation ability of CPs, an interesting question is whether CPs can grow on iron oxide NP seeds and incorporate guest molecules at the same time.…”

“…[38][39] We and others demonstrated that CPs are capable of adsorbing and entrapping a broad range of molecules. 24,35,39 Given the encapsulation ability of CPs, an interesting question is whether CPs can grow on iron oxide NP seeds and incorporate guest molecules at the same time. If so, a convenient, efficient, and high capacity method might be derived for introducing various materials and molecules upon the magnetic core.…”

In-Situ Self-Assembly of Zinc/Adenine Hybrid Nanomaterials for Enzyme Immobilization

“…Up to now, various types of biomolecules, such as nucleotides [34], proteins [35], peptides [36], amino acids [37] and nucleobases [38] have been used as the ligands to construct CPs. It also has been demonstrated that some CPs are capable of adsorbing and entrapping a broad range of molecules, due to their good biocompatibility and porosity [34,39]. Adenine, as an important naturally occurring nitrogen heterocycle present in nucleic acids [40], has multiple possible metal-binding modes [41][42][43].…”