Historical perspectiveOrganic-inorganic hybrid nanoflowers: The known, the unknown, and the future
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Definition, significance, and the history behind organic-inorganic hybrid nanoflowers (HNFs)
Organic-inorganic hybrid materials have drawn increasing attention in recent years as they simultaneously benefit from characteristics of both organic and inorganic constituents [1]. Flower-shaped organic-inorganic hybrid nanoflowers (HNFs) (Fig. 1) are one of the most popular hybrid materials that were accidentally discovered in 2012 by Zare’s group [2]. The inorganic component of HNFs is mainly composed of metal phosphates such as cobalt, copper, manganese, zinc, ferrous, and calcium salts.
One-pot conventional biomineralization method
As mentioned, HNFs were firstly discovered by Zare’s group after an accidental addition of copper sulfate to phosphate-buffered saline (PBS) (pH 7.4) containing bovine serum albumin (BSA) followed by an incubation of 3 days at room temperature [2]. The most commonly used method for preparing HNFs is nearly identical to the research of Zare's group. For instance, phosphotriesterase (PTE)@Cu3(PO4)2•HNFs were synthesized by the incubation of a mixture containing phosphate buffer, PTE, and CuSO4 at
Mechanism of HNFs formation
As discussed, HNFs have been synthesized by a number of methods; however, all of the methods are based on the coordination between organic and inorganic components. It is believed that the formation mechanism of HNFs involves nucleation, coordination, precipitation, and self-assembly [2]. At first, the spontaneous interfacial reaction between metal ions and negatively-charged phosphate groups results in the formation of metal phosphate nanocrystals. The primary crystals participate in
Innovations in designing HNFs
Incorporating a wide range of organic substances in the structure of HNFs to achieve novel or desired specific properties is a developing concern. Most reported HNFs are fabricated by incorporating enzymes as the organic and copper phosphate as the inorganic building blocks, as previously mentioned. Designing distinct and innovative HNFs is favorable for enhancing their biocatalytic functions such as enzyme stability, activity, and reusability. Therefore, enzyme-free, magnetic, and
HNFs-mediated biocatalysis
Both enzyme-loaded and enzyme-free HNFs can be applied as biocatalysts in many biochemical reactions, and the incorporation of enzymes inside HNFs increases their catalytic activity, reusability, and stability. Magnetic laccase-loaded HNFs with Cu3(PO4)2 were designed to degrade bisphenol A [98]. Laccase activity inside MHNFs was 3.3 times higher than that of the free enzyme, and the immobilized laccase retained 70% of its initial activity after 8 reuse cycles. The stability of the enzyme
Concluding remarks and future perspectives
HNFs have received remarkable attention during the past decade regarding their facile synthesis, flower-shaped structures, high surface property, and potential applications. Wide ranges of organic molecules and metal phosphates have been incorporated into the structures of HNFs. Based on recent evidences, it is proposed that the coordination of oxygen atoms from an organic constituent as well as nitrogen atoms with metal ions of an inorganic part is another possible type of mechanism involved
CRediT authorship contribution statement
Hossein Jafari-Nodoushan: Conceptualization, Methodology, Investigation, Writing – original draft, Visualization, Writing – review & editing. Somayeh Mojtabavi: Formal analysis, Data curation, Writing – original draft. Mohammad Ali Faramarzi: Supervision, Conceptualization, Methodology, Resources, Data curation, Writing – review & editing, Project administration, Funding acquisition. Nasrin Samadi: Supervision, Formal analysis, Writing – review & editing, Conceptualization, Software,
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
This work was financially supported by the grant No. 1400-2-104-53421 from Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran. The study is a part of the Ph.D. thesis of Dr. H. Jafari-Nodoushan.
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