Abstract
As a result of their unique structural and multifunctional characteristics, organic–inorganic hybrid nanoflowers (hNFs), a newly developed class of flower-like, well-structured and well-oriented materials has gained significant attention. The structural attributes along with the surface-engineered functional entities of hNFs, e.g., their size, shape, surface orientation, structural integrity, stability under reactive environments, enzyme stabilizing capability, and organic–inorganic ratio, all significantly contribute to and determine their applications. Although hNFs are still in their infancy and in the early stage of robust development, the recent hike in biotechnology at large and nanotechnology in particular is making hNFs a versatile platform for constructing enzyme-loaded/immobilized structures for different applications. For instance, detection- and sensing-based applications, environmental- and sustainability-based applications, and biocatalytic and biotransformation applications are of supreme interest. Considering the above points, herein we reviewed current advances in multifunctional hNFs, with particular emphasis on (1) critical factors, (2) different metal/non-metal-based synthesizing processes (i.e., (i) copper-based hNFs, (ii) calcium-based hNFs, (iii) manganese-based hNFs, (iv) zinc-based hNFs, (v) cobalt-based hNFs, (vi) iron-based hNFs, (vii) multi-metal-based hNFs, and (viii) non-metal-based hNFs), and (3) their applications. Moreover, the interfacial mechanism involved in hNF development is also discussed considering the following three critical points: (1) the combination of metal ions and organic matter, (2) petal formation, and (3) the generation of hNFs. In summary, the literature given herein could be used to engineer hNFs for multipurpose applications in the biosensing, biocatalysis, and other environmental sectors.
Highlights
These results showed a ~137%, ~325%, and ~446% increase in activity compared with free crude soybean peroxidase (SBP), respectively, which has an activity of 572 U/mg [24]
The free horseradish peroxidase (HRP) activity was 2970.5 U/mg, whereas the embedded HRP activity was 15,040.5 U/mg. This led to a 506% increase in the inactivity of the HRP-embedded nanoflowers [36]. All of these studies solidified that organic–inorganic hybrid nanoflowers significantly boost the catalytical activity of the embedded enzyme, which can be ascribed to the four previously-mentioned reasons
The results showed that the different proteins tested (papain, bovine serum albumin (BSA) laccase, and horseradish peroxidase) gave different hybrid nanoflowers (hNFs) morphologies, which is supported by previous studies
Summary
Enzymes are used in many industrial applications, including food, drugs, and water remediation [1,2,3,4,5,6,7], and have numerous benefits, including a high catalytic efficiency, a high selectivity, and biodegradability. Despite all of these benefits, the use of enzymes in industrial applications has some limitations, such as a low operational stability, difficult recovery, low reproducibility, and a high cost. This review will focus on enzyme immobilization using organic–inorganic hybrid nanoflowers (hNFs), and will cover their synthesis, advantages, different types of nanoflowers, and applications
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