Forming amorphous calcium carbonate within hydrogels by enzyme-induced mineralization in the presence of N-(phosphonomethyl)glycine

Milovanovic, Marko; Unruh, Marvin T.; Brandt, Volker; Tiller, Joerg C.

doi:10.1016/j.jcis.2020.06.047

Cited by 15 publications

(12 citation statements)

References 54 publications

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“…Analytical investigation of the mineralized hydrogel was carried out analogous to previous publications. − ,, The freeze-dried, mineralized composite networks were broken in liquid nitrogen prior to further analysis. The cross-sections were investigated by scanning electron microscopy (SEM).…”

Section: Methodsmentioning

confidence: 99%

Improving the Strength of Ultrastiff Organic–Inorganic Double-Network Hydrogels

et al. 2021

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Swollen double networks (DNs) are hydrogels with greatly improved stiffness, toughness, and strength compared to classical hydrogels. The highest stiffness is achieved for organic− inorganic DN hydrogels, which show a rather low tensile strength of about 1 MPa so far. It was presumed that this is due to an insufficient reversible bond formation between inorganic and organic phases. Therefore, the influence of the functional groups that form reversible bonds between these two phases was investigated on the example of calcium phosphate-based DN hydrogels. The functional groups were introduced by copolymerization of acrylate-based monomers with acrylamide and N,Ndimethylacrylamide, respectively, to form a hydrogel-containing alkaline phosphatase. After enzyme-induced mineralization, it was found that only acrylic acid (AA) results in improved strength of the formed ultrastiff DN hydrogels. Stress−strain curves with different strain rates revealed that Young's modulus of ∼300 MPa is constant in all cases, while the tensile strength increases from 7 MPa at 5% min −1 to 17 MPa at 750% min −1 . The fracture toughness of these optically transparent DN hydrogels, which are among the stiffest and strongest existing hydrogels, is up to 2000 J m −2 which is also improved by the introduction of AA into the hydrogel.

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Section: Methodsmentioning

confidence: 99%

Improving the Strength of Ultrastiff Organic–Inorganic Double-Network Hydrogels

et al. 2021

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“…The ratio between the neutral and the charged monomers was continually changed until the degree of mineralization in the final DN hydrogel drops, i.e., the urease activity decreases. The mineralization was performed using the same chemical conditions as described earlier [47]. The calcification was performed at 20°C for 24 h. The degrees of mineralization and Young's modulus of the organic-inorganic double-network hydrogels (O/I-DNHs) are provided in Supp.…”

Section: Resultsmentioning

confidence: 99%

“…This led to homogenous precipitation of spherical agglomerates of longterm stable amorphous CaCO 3 (ACC) in high quantity inside the hydrogel matrix. Although the ureaseinduced calcification leads to a uniform and homogenous precipitation of inorganic material inside the hydrogel, no significant improvement of the mechanical properties was observed, which might be due to missing binding between polymer matrix and the precipitated inorganic material [47].…”

Section: Introductionmentioning

confidence: 93%

Enzyme-induced mineralization of hydrogels with amorphous calcium carbonate for fast synthesis of ultrastiff, strong and tough organic–inorganic double networks

et al. 2021

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Hydrogels with good mechanical properties have great importance in biological and medical applications. Double-network (DN) hydrogels were found to be very tough materials. If one of the two network phases is an inorganic material, the DN hydrogels also become very stiff without losing their toughness. So far, the only example of such an organic–inorganic DN hydrogel is based on calcium phosphate, which takes about a week to be formed as an amorphous inorganic phase by enzyme-induced mineralization. An alternative organic–inorganic DN hydrogel, based on amorphous CaCO3, which can be formed as inorganic phase within hours, was designed in this study. The precipitation of CaCO3 within a hydrogel was induced by urease and a urea/CaCl2 calcification medium. The amorphous character of the CaCO3 was retained by using the previously reported crystallization inhibiting effects of N-(phosphonomethyl)glycine (PMGly). The connection between organic and inorganic phases via reversible bonds was realized by the introduction of ionic groups. The best results were obtained by copolymerization of acrylamide (AAm) and sodium acrylate (SA), which led to water-swollen organic–inorganic DN hydrogels with a high Young’s modulus (455 ± 80 MPa), remarkable tensile strength (3.4 ± 0.7 MPa) and fracture toughness (1.1 ± 0.2 kJ m−2). Graphical Abstract The present manuscript describes the method of enzymatic mineralization of hydrogels for the production of ultrastiff and strong composite hydrogels. By forming a double-network structure based on an organic and an inorganic phase, it is possible to improve the mechanical properties of a hydrogel, such as stiffness and strength, by several orders of magnitude. The key to this is the formation of a percolating, amorphous inorganic phase, which is achieved by inhibiting crystallization of precipitated amorphous CaCO3 with N-(phosphonomethyl)glycine and controlling the nanostructure with co polymerized sodium acrylate. This creates ultrastiff, strong and tough organic–inorganic double-network hydrogels.

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“…Then, the glass slides were carefully separated and the formed polymer film (thickness 300 ± 30 µm) was either ferrified or stored until use at −25 °C. [ 42–47 ]…”

Section: Methodsmentioning

confidence: 99%

“…A recent method to achieve the formation of highly ordered nanostructures within a polymer matrix is the enzyme-induced mineralization (EIM). [42][43][44][45][46][47] This method allows the formation of percolated nanostructures of amorphous and crystalline calcium carbonate and -phosphate within hydrogels. The degree of mineralization of such materials reaches 70-90 wt%, and the fully transparent materials can be tuned in stiffness over several orders of magnitude while also showing a remarkable toughness, with fracture energies of 1000-2000 J m −2 .…”

Section: Introductionmentioning

confidence: 99%

Enzyme‐Induced Ferrification of Hydrogels for Toughening of Functional Inorganic Compounds

Milovanovic

Rauner

Civelek

et al. 2022

Macro Materials & Eng

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Enzyme-induced mineralization (EIM) has been shown to greatly enhance the mechanical properties of hydrogels by precipitation of calcium salts. Another feature of such hydrogels is their high toughness even when containing finely nanostructured mineral content of ≈75 wt%. This might be useful for bendable materials with high content of functional inorganic nanostructures. The present study demonstrates that EIM can form homogeneous nanostructures of water-insoluble iron salts within hydrogels. Crystalline iron(II) carbonate precipitates urease-induced within polyacrylate-based hydrogels and forms platelet structures that have the potential of forming self-organized nacre-like architectures. The platelet structure can be influenced by chemical composition of the hydrogel. Further, amorphous iron(II) phosphate precipitates within hydrogels with alkaline phosphatase, forming a nanostructured porous inorganic phase, homogeneously distributed within the double network hydrogel. The high amount of iron phosphate (more than 80 wt%) affords a stiffness of ≈100 MPa. The composite is still bendable with considerable toughness of 400 J m −2 and strength of 1 MPa. The high water content (>50%) may allow fast diffusion processes within the material. This makes the iron phosphate-based composite an interesting candidate for flexible electrodes and demonstrates that EIM can be used to deliberately soften ceramic materials, rendering them bendable.

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Forming amorphous calcium carbonate within hydrogels by enzyme-induced mineralization in the presence of N-(phosphonomethyl)glycine

Cited by 15 publications

References 54 publications

Improving the Strength of Ultrastiff Organic–Inorganic Double-Network Hydrogels

Improving the Strength of Ultrastiff Organic–Inorganic Double-Network Hydrogels

Enzyme-induced mineralization of hydrogels with amorphous calcium carbonate for fast synthesis of ultrastiff, strong and tough organic–inorganic double networks

Enzyme‐Induced Ferrification of Hydrogels for Toughening of Functional Inorganic Compounds

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