14
aqueous media, which is critical for manipulation and processing
for the envisaged applications. To overcome that handicap, chemical functionalization of CNHs is imperative and to this end a plethora of strategies have been developed broadly based on the covalent
addition of organic species onto the outer skeleton of CNHs [3–
17], as well as on the non-covalent/supramolecular interactions
through electrostatic association [18–20] with charged species
and/or π − π stacking forces [21–23] with planar aromatic molecules. In addition, oxidation of the conical tips of CNHs, introducing carboxylic units suitable for further chemical alteration, is
another widely employed methodology for effectively modifying
CNHs [18, 24–33]. A typical process for the oxidation of CNHs
involves heat treatment in the presence of oxygen, while the lightassisted oxidation of CNHs in the presence of hydrogen peroxide
is comparatively a much milder technique [33, 34]. Hence without
surprise, a variety of biomolecules were attached through
carbodiimide- mediated condensation reactions on oxidized CNHs.
For example, bovine serum albumin (BSA) was covalently incorporated at the carboxylic units of light-assisted oxidized CNHs. The
BSA-CNH material formed homogeneous dispersions into phosphate buffer saline, allowing incorporation inside mammalian cells
through endocytosis [33].
A significant benefit of CNHs as compared to carbon nanotubes is that they do not have the high aspect ratio issues related to
toxicity observed in longer nanotubes. Furthermore, the irregular
structure of CNHs permits the opening of nanowindows at the
tips and sidewalls of CNHs, from which incorporation and release
of bioactive molecules are feasible and easier. Hence, CNHs as a
highly pure and easily available material have been successfully
tested as drug carriers [35–38].
Summarizing, the capability for large-scale production of
CNHs accompanied by their handy chemical manipulation, as
illustrated in Fig. 1, makes this unique carbon nanostructure a
promising biocompatible drug delivery platform.
2 Materials
1. A chamber equipped with a high-power CO 2 laser source
(wavelength 10.6 μm, maximum power 5 kW, variable pulse
duration from 10 ms to continuous illumination, and beam
2.1 Preparation
of CNHs
Fig. 1 (continued) at the edge of the conical tips of CNHs, which can then be converted to the corresponding
acyl chlorides for subsequent coupling with hydroxyl- or amine-terminated drugs/biomolecules. Right: Harsh
oxidative treatment of CNHs, followed by reduction of the introduced oxygen functionalities, generates pores at
the edge of the cone and onto the sidewalls of CNHs, thereby enabling the release of the drugs/biomolecules
encapsulated by nanoprecipitation into CNHs
Anastasios Stergiou and Nikos Tagmatarchis
aqueous media, which is critical for manipulation and processing
for the envisaged applications. To overcome that handicap, chemical functionalization of CNHs is imperative and to this end a plethora of strategies have been developed broadly based on the covalent
addition of organic species onto the outer skeleton of CNHs [3–
17], as well as on the non-covalent/supramolecular interactions
through electrostatic association [18–20] with charged species
and/or π − π stacking forces [21–23] with planar aromatic molecules. In addition, oxidation of the conical tips of CNHs, introducing carboxylic units suitable for further chemical alteration, is
another widely employed methodology for effectively modifying
CNHs [18, 24–33]. A typical process for the oxidation of CNHs
involves heat treatment in the presence of oxygen, while the lightassisted oxidation of CNHs in the presence of hydrogen peroxide
is comparatively a much milder technique [33, 34]. Hence without
surprise, a variety of biomolecules were attached through
carbodiimide- mediated condensation reactions on oxidized CNHs.
For example, bovine serum albumin (BSA) was covalently incorporated at the carboxylic units of light-assisted oxidized CNHs. The
BSA-CNH material formed homogeneous dispersions into phosphate buffer saline, allowing incorporation inside mammalian cells
through endocytosis [33].
A significant benefit of CNHs as compared to carbon nanotubes is that they do not have the high aspect ratio issues related to
toxicity observed in longer nanotubes. Furthermore, the irregular
structure of CNHs permits the opening of nanowindows at the
tips and sidewalls of CNHs, from which incorporation and release
of bioactive molecules are feasible and easier. Hence, CNHs as a
highly pure and easily available material have been successfully
tested as drug carriers [35–38].
Summarizing, the capability for large-scale production of
CNHs accompanied by their handy chemical manipulation, as
illustrated in Fig. 1, makes this unique carbon nanostructure a
promising biocompatible drug delivery platform.
2 Materials
1. A chamber equipped with a high-power CO 2 laser source
(wavelength 10.6 μm, maximum power 5 kW, variable pulse
duration from 10 ms to continuous illumination, and beam
2.1 Preparation
of CNHs
Fig. 1 (continued) at the edge of the conical tips of CNHs, which can then be converted to the corresponding
acyl chlorides for subsequent coupling with hydroxyl- or amine-terminated drugs/biomolecules. Right: Harsh
oxidative treatment of CNHs, followed by reduction of the introduced oxygen functionalities, generates pores at
the edge of the cone and onto the sidewalls of CNHs, thereby enabling the release of the drugs/biomolecules
encapsulated by nanoprecipitation into CNHs
Anastasios Stergiou and Nikos Tagmatarchis