SCIENTIFIC HIGHLIGHTS

Preparation of curcumine bio-metal-organic-frameworks (bio-MOFs)

This article analyses the use of supercritical CO2 green technology in the reactive crystallization processes of a bio-MOF composed by curcumin and Zn (II) metal centres.

The attained success in controlling the structure, functionality and porosity of MOFs materials has led to the development of numerous applications, most notably in gas adsorption, energy conversion and storage, and medicine. Medical applications would require constructions made of biocompatible building blocks, which drive on the development of the topic of metal−biomolecule frame-works or bioMOFs. In this article, a new phase with a [Zn(curcumin)]n composition, termed sc-CCMOF-1, is presented. In previous research we have demonstrated that 1D to 3D coordination polymers can be prepared in scCO2 through reactive crystallization by the right choice of building blocks with suitable solubility in this fluid. 

In this case, the developed scCO2 methodology  allowed the precipitation in high yields of the small-sized crystalline material, which was characterized by the use of the recently developed electron diffraction tomography method applied to the resolution of sub-micrometric crystals. A remarkable 3D macrostructure with a complex morphology was obtained.

To analyse the crystallization mechanism, multiple identical runs were performed under similar experimental conditions to study in each time period the crystal growth progress ex-situ by X-ray diffraction and scanning electron microscopy. These experiments indicated that the process to achieve the sc-CCMOF-1 in a crystalline form involves the formation of amorphous or semi-crystalline metastable phases that derived into hierarchical stable and crystalline nano-flower aggregates. In addition, a potential therapeutic application of the bio-MOF was tested by studying the released of the curcumin molecule at neutral pH. The obtained results indicate that the curcumin dissolution process was faster from the synthesized MOF than from the pristine curcumin. The dynamic micro-porosity of the bio-MOF appears to provide the advantage of speeding dissolution by facilitating water diffusion to the interior of the bioMOF, thus increasing the bioavailability.

Authors:  
Nuria Portolés-Gil,1 Arianna Lanza,2 Núria Aliaga-Alcalde,1,3 José A. Ayllón,4 Mauro Gemmi,2 Enrico Mugnaioli,2 Ana M. López-Periago,1 and Concepción Domingo1

Affiliation:
1Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Spain
2Center for Nanotechnology Innovation@NEST, Istituto Italiano di Tecnologia, Italy
3 ICREA, Institució Catalana de Recerca i Estudis Avançats, Spain
4Departamento de Química Analítica, Universidad de Barcelona, Spain

Publication:
Crystalline Curcumin bioMOF Obtained by Precipitation in Supercritical CO2 and Structural Determination by Electron Diffraction Tomography
ACS Sustainable Chemistry & Engineering 6, 12309-12319 (2018)
DOI: 10.1021/acssuschemeng.8b02738

Figure:
Scheme of the formation of curcumin–based  bio-MOF and its crystal structure.

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