Enzyme-Loaded Flower-Shaped Nanomaterials: A Versatile Platform with Biosensing, Biocatalytic, and Environmental Promise

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.

Keywords: bio-catalysis; biosensing cues; biosynthesis; hybrid nanoflowers; influencing factors.

Figure 1

Schematic illustration of the hybrid nanoflower (hNF) formation process.

Figure 2

Formation of BSA-Cu₃(PO₄)₂.3H₂O nanoflowers. The SEM images at different times: (a) 2 h, (b) 12 h, and (c) 3 days. Reprinted from [20] with permission from Springer Nature. Copyright © 2021, Nature Publishing Group. License Number: 5031780508604.

Figure 3

SEM image (a) without the addition of lipase enzyme, (b) with the addition of lipase enzyme. Reprinted from [21] with permission from the Royal Society of Chemistry. Copyright © The Royal Society of Chemistry. License Number: 1105113-1.

Figure 4

SEM images of different ChT concentrations on the formation of nanoflowers: (a1,a2) 0.0 mg/mL, (b1,b2) 0.05 mg/mL, (c1,c2) 0.1 mg/mL, and (d1,d2) 0.5 mg/mL. Reprinted from [22] with permission from the Royal Society of Chemistry. Copyright © The Royal Society of Chemistry. License Number: 1105121-1.

Figure 5

SEM image of different trypsin concentrations on the formation of nanoflowers: (A1,A2) 0.0 mg/mL, (B1,B2) 0.02 mg/mL, (C1,C2) 1.0 mg/mL, and (D1,D2) 5.0 mg/mL. Reprinted from [23] with permission from the Royal Society of Chemistry. Copyright © The Royal Society of Chemistry. License Number: 1105124-1.

Figure 6

SEM image of different soybean peroxidase (SBP) concentrations on the formation of nanoflowers: (A) 0.0 mg/mL, (B) 0.5 mg/mL, (C) 1.0 mg/mL, and (D) 2.0 mg. Reprinted from [24] with permission from Elsevier. Copyright © 2021 Elsevier B.V. License Number: 5031790214453.

Figure 7

Dual cycle process for enzyme immobilization. Reprinted from [37] with permission from the Royal Society of Chemistry under the Creative Commons Attribution 3.0 Unported Licence.

Figure 8

SEM images of hybrid nanoflowers: (a–l) column 1, a-lactalbumin; column 2, laccase; column 3, carbonic anhydrase; column 4, lipase; at protein. Reprinted from [20] with permission from Springer Nature. Copyright © 2021, Nature Publishing Group. License Number: 5031780508604.

Figure 9

Preparation of MNP-GOx NFs. Reprinted from [111] with permission from Elsevier. Copyright © 2021 Elsevier B.V. License Number: 5031790647430.

Figure 10

Formation of copper hNFs. Reprinted from [42] with permission from the American Chemical Society. Copyright © 2021 American Chemical Society.

Figure 11

The growing process copper−protein hNFs. Reprinted from [42] with permission from the American Chemical Society. Copyright © 2021 American Chemical Society.

Figure 12

SEM of Cu-BSA hNFs with different protein concentrations, with an incubation time of 6 h. Reprinted from [42] with permission from the American Chemical Society. Copyright © 2021 American Chemical Society.

Figure 13

The process of self-repairing sodium alginate (SA)-coated CPO-Ca₃(PO₄)₂ hybrid nanoflowers. Reprinted from [87] with permission from the Royal Society of Chemistry. Copyright © The Royal Society of Chemistry. License Number: 1105129-1.

Figure 14

Summary of different applications used for hNFs. (A) Fast detection of phenol using laccase/cooper phosphate hNFs integrated into a membrane. Reprinted from [55] with permission from John Wiley and Sons. Copyright © 2021 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim. License Number: 5031800087304. (B) Detection of ractopamine using a protein/manganese ion hNF electrochemical biosensor. Reprinted from [98] with permission from Elsevier. Copyright © 2021 Elsevier B.V. License Number: 5031800271904. (C) Selective separation of cadmium and lead in water, cigarette, and hair samples using BSA/copper ions hNFs. Reprinted from [131] with permission from Elsevier. Copyright © 2021 Elsevier B.V. License Number: 5031800434687. (D) Degradation of bisphenol A using laccase/cooper phosphate hNFs. Reprinted from [34] with permission from Elsevier. Copyright © 2021 Elsevier B.V. License Number: 5031800600650. (E) Epoxidation of alkenes using dual enzyme system GOx and lipase/copper ions hNFs. Reprinted from [77] with permission from Elsevier. Copyright © 2021 Elsevier Ltd. License Number: 5031800753597. (F) Transformation of D-Galactose to D-Tagatose using L-Arabinose Isomerase/manganese ions hNFs. Reprinted from [95] with permission from the American Chemical Society. Copyright © 2021 American Chemical Society.