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Global Translational Medicine Eco-friendly biomedical materials: A review

Qian et al. synthesized a CNT gel scaffold for targeted preparation of these materials. Top-down approaches
drug delivery and in vitro osteogenesis, which resulted consist of separating graphite from graphene layers;
in beneficial effects on adipose-derived stem cell activity however, these methods require high energy in the form
and osteogenic differentiation. On biosensors, Gupta et of heat or electricity while at the same time offering a
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al. fabricated an electrochemical non-enzymatic glucose low yield. Among the bottom-up approaches, CVD is
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sensor based on a set of CNTs microelectrodes. The sensor considered one of the most efficient, offering high quality
was evaluated by quantifying glucose in non-diabetic and yield. In addition, this method allows the formation
human blood and diabetic patient urine samples. 109 of graphene directly on the desired surface, as shown in
Carbon nanotubes usually are synthesized by CVD. the work of Xu et al., who deposited graphene on a thin
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High-temperature techniques, such as laser ablation metallic surface. Graphene and its derivatives, such
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or arc discharge, were previously used but have been as GO and reduced GO (rGO), have gained significant
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substituted by CVD methods since the geometric and research interest due to their exceptional properties and
morphological characteristics can be more accurately advancements in synthesis methods, making them readily
controlled at lower temperatures (below 800°C) while also available for various applications (Figure 9). 123
having the option to synthesize other types of nanotubes at Pure graphene green synthesis is generally limited to
higher temperatures. For instance, Chan et al. synthesized the usage of relatively high temperatures (over 100°C)
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MWCNTs at 600 °C with a heating rate of 10 °C/min, while compared to its previously mentioned derivatives, as
Ding et al. prepared semiconducting SWCNTs at 920°C. 113 shown in the work of Gürünlü et al., who prepared
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The main strategies for the green synthesis of CNTs graphene from flake graphite using salts at 500°C, and
include the usage of greener precursors and catalysts along Bindumadhavan et al., who prepared graphene from GO at
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with the optimization of methodologies to reduce the 100°C using a wet chemistry approach. As with graphene,
environmental impact. The Principles of Green Chemistry the preparation of GO requires a high energy input and
must be considered when defining the precursors, catalysts, earlier preparation of pure graphene for oxidation. Greener
purification, and gas emissions during synthesis. methods are more common in the preparation of reduced
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Examples of this include the work of Adeniran and Mokaya GO from graphene. Similar to metallic nanomaterials,
who synthesized CNTs using carbon tetrachloride as a green extracts can be used to prepare rGO materials. For
precursor and ferrocene/Ni as substrate/catalyst at 180°C, example, Meka Chufa et al. prepared rGO using a Vernonia
reducing the energy input required for CNTs formation. amygdalina extract through a green wet chemistry
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Tripathi et al. used plant extracts as precursors for synthesis approach requiring a relatively low temperature (50°C). 126
using a CVD process at 575°C. 115
4. Liposomes
3.2. Graphene and graphene oxide (GO)
Liposomes are lipid-based vesicles that have gained
Graphene consists uniquely of carbon atoms bound significant attention in biomedical research due to their
together by sp hybrid bonds to form a honeycomb unique properties and versatility in various applications. They
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structure. On the other hand, GO is a layered structure with consist of a lipid bilayer structure, such as cell membranes,
=O, -OH, -O- and -COOH functional groups attached to enclosing an aqueous core. This composition allows
the edges of the layer. The oxygen content present in GO liposomes to encapsulate hydrophilic substances within their
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may be reduced through chemical or thermal methods to core and incorporate hydrophobic compounds within the
form reduced GO. 113-115 Drug delivery, biosensing, 118,119 , lipid bilayer. 127,128 Figure 10 shows the general structure of a
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and implants are the major applications of GO. Both liposome and its different biomedical applications. 129
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top-down and bottom-up approaches are used for the
They have been extensively used in biomedical
applications as follows:
a) Drug delivery. Liposomes have been extensively
explored as drug-delivery vehicles. They can
encapsulate drugs within their aqueous core or lipid
bilayer and efficiently transport them to specific
target sites in the body. Liposomes can improve the
pharmacokinetics and biodistribution of drugs,
enhance their stability, and enable controlled release,
Figure 8. Schematic representation of single-walled (SWCNT), double-
walled (DWCNT), and multi-walled carbon nanotube (MWCNT). resulting in improved therapeutic efficacy and reduced
Reproduced from Patil et al. Copyright © 2021, The Author(s). side effects.
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Volume 3 Issue 4 (2024) 8 doi: 10.36922/gtm.4698