Topics in Current Chemistry (2020) 378:12
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In addition, enzymes such as laccases have been immobilized in AuNPs by supramolecular interactions between the aromatic amino acids of the side chains of the
enzyme and functionalized ferrocene molecules as a coating on the NPs. The results
were compared with an analogous covalent coupling, demonstrating the advantages
of supramolecular conjugations [146, 147].
Antibody–antigen interactions have also been used for bionanoconjugaion. In
several cases, immobilization is beneficial to increase the nanoparticle-antibodyantigen association constant, relative to the free antibody [148, 149]. The immobilization of antibodies on nanomaterials has found several applications in diagnosis
[150], biosensing [151], magnetic separation [152], purification of analytes [153]
and cell labeling [154].
5.3 Encapsulation
Encapsulation on nanometric supports occurs when NPs coated with hydrophobic
ligands are overcoated with amphiphilic ligands. The process at the surface of the
NPs is achieved by intercalating the hydrophobic portions of ligands (or biomolecules) of the solution with the hydrophobic coatings of the NPs. Thus, the hydrophilic portion of the immobilized component (ligand or biomolecule) is oriented
towards the solution. This methodology allows the stabilization of colloidal systems
in hydrophilic media due to the head groups within the hydrophilic portion of the
coating. In addition, the functional group may also allow further bioconjugation of
the NPs, as previously reported [155].
This methodology allows the immobilization of drugs inside polymeric nanoparticles to develop controlled release agents and nanodelivery systems in cancer
therapy [156]. Encapsulation of essential oils in poly(ɛ-caprolactone) nanocapsules
has been reported to enhance the antimicrobial activity against food-borne pathogens. This is promising for food preservation [157]. Essential oils have also been
encapsulated using several supports with different designs including NPs [158],
nanocapsules [159], nanoemulsions [160], micelles [161], and liposomes [162]. In
these cases, the formation of polymer-based and lipid-based nanosystems avoids
the drawbacks of essential oils related to their volatility and low solubility, and also
enhances antioxidant, anti-inflammatory and antibacterial activities of the encapsulated compounds. Nanoencapsulation has been also used to enable the production of
“healthy” foods and drugs, through delivering specific substances such as vitamins
[163], antibiotics [164], flavors [165], antioxidants [166], omega-3 fatty acids [167],
proteins [168], and nucleic acids [169] in an easily absorbable nanometric form.
The operational lifetime of enzymes for environmental applications may be
enhanced through encapsulation. As an example, laccase encapsulated within chitosan NPs showed temperature and pH activity profiles similar to those of free
enzyme, but the procedure of encapsulation ensured its stability against microbial
degradation, allowing clear applications in industrial bioremediation [170]. Encapsulation has also extended the use of enzymes in conditions where these biocatalysts are neither stable nor active. For instance, GOx has been encapsulated within
polymeric nanocapsules with a hydrophilic core via inverse miniemulsion periphery
108
Reprinted from the journal
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In addition, enzymes such as laccases have been immobilized in AuNPs by supramolecular interactions between the aromatic amino acids of the side chains of the
enzyme and functionalized ferrocene molecules as a coating on the NPs. The results
were compared with an analogous covalent coupling, demonstrating the advantages
of supramolecular conjugations [146, 147].
Antibody–antigen interactions have also been used for bionanoconjugaion. In
several cases, immobilization is beneficial to increase the nanoparticle-antibodyantigen association constant, relative to the free antibody [148, 149]. The immobilization of antibodies on nanomaterials has found several applications in diagnosis
[150], biosensing [151], magnetic separation [152], purification of analytes [153]
and cell labeling [154].
5.3 Encapsulation
Encapsulation on nanometric supports occurs when NPs coated with hydrophobic
ligands are overcoated with amphiphilic ligands. The process at the surface of the
NPs is achieved by intercalating the hydrophobic portions of ligands (or biomolecules) of the solution with the hydrophobic coatings of the NPs. Thus, the hydrophilic portion of the immobilized component (ligand or biomolecule) is oriented
towards the solution. This methodology allows the stabilization of colloidal systems
in hydrophilic media due to the head groups within the hydrophilic portion of the
coating. In addition, the functional group may also allow further bioconjugation of
the NPs, as previously reported [155].
This methodology allows the immobilization of drugs inside polymeric nanoparticles to develop controlled release agents and nanodelivery systems in cancer
therapy [156]. Encapsulation of essential oils in poly(ɛ-caprolactone) nanocapsules
has been reported to enhance the antimicrobial activity against food-borne pathogens. This is promising for food preservation [157]. Essential oils have also been
encapsulated using several supports with different designs including NPs [158],
nanocapsules [159], nanoemulsions [160], micelles [161], and liposomes [162]. In
these cases, the formation of polymer-based and lipid-based nanosystems avoids
the drawbacks of essential oils related to their volatility and low solubility, and also
enhances antioxidant, anti-inflammatory and antibacterial activities of the encapsulated compounds. Nanoencapsulation has been also used to enable the production of
“healthy” foods and drugs, through delivering specific substances such as vitamins
[163], antibiotics [164], flavors [165], antioxidants [166], omega-3 fatty acids [167],
proteins [168], and nucleic acids [169] in an easily absorbable nanometric form.
The operational lifetime of enzymes for environmental applications may be
enhanced through encapsulation. As an example, laccase encapsulated within chitosan NPs showed temperature and pH activity profiles similar to those of free
enzyme, but the procedure of encapsulation ensured its stability against microbial
degradation, allowing clear applications in industrial bioremediation [170]. Encapsulation has also extended the use of enzymes in conditions where these biocatalysts are neither stable nor active. For instance, GOx has been encapsulated within
polymeric nanocapsules with a hydrophilic core via inverse miniemulsion periphery
108
Reprinted from the journal