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Global Translational Medicine Graphene oxide in cancer drug delivery applications

then washed and centrifuged until the pH reaches neutral. synthesis. While chemical methods often result in GO with
This process yields GO either as a liquid suspension or a damaged structure and poor electrical properties, they
in dry powder form. Despite its widespread use, ongoing remain an active area of exploration. Recent modifications
research seeks to improve the Hummers’ method for greater to Tour’s method have shown promising results, with
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productivity, efficiency, and quality. Many modifications Ranjan et al. optimizing the process by adjusting the
involve using alternative oxidizing agent mixtures, often ratio of permanganate to acids. Electrochemical synthesis
excluding nitrates, adopting two-step processes, utilizing offers an eco-friendly alternative, with significant potential
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co-oxidants, and applying low- or room-temperature for large-scale production. This approach provides several
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conditions. Guo et al. proposed an innovative method benefits, including reduced chemical waste, enhanced
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by incorporating an electric field during synthesis, quality of GO, precise control over oxidation levels, and
significantly improving efficiency, increasing yield, and defect density. 36
reducing reaction times. This advancement offers essential
knowledge for optimizing GO production. GOs generated 3. Synthesis of rGO
through the Hummers’ method contain a higher amount rGO can be synthesized using various methods, including
of oxygen functional groups, including hydroxyl, carboxyl, chemical, biological, thermal, and photoreduction techniques
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and epoxy groups. These functional groups improve GO’s (Table 2).
hydrophilicity and allow for various surface modifications,
expanding its applicability. 15,20,21 The high specific surface 3.1. Chemical route
area of GO also renders it ideal for use in adsorption and Chemical reduction methods employ reducing agents such
catalysis. 15,22-26 as hydrazine, ascorbic acid, catalysts, sodium borohydride,

2.4. Tour’s method and hydroiodic acid. Hydrazine is particularly effective,
producing rGO with high conductivity and a C/O ratio
Tour’s method is an advanced alternative to the Hummers’ of up to 15.1, though it may leave some functional groups
method, incorporating enhancements that improve both intact. Ascorbic acid offers a green and biocompatible
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safety and efficiency. This method utilizes a mixture of alternative, although it may induce defects in the structure.
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phosphoric acid and H₂SO₄ with KMnO₄ as the oxidizing Catalytic methods using aluminum and zinc allow for rapid
agent, conducted at lower temperatures to minimize the GO reduction, with aluminum reacting with hydrochloric
risk of explosive reactions. The controlled oxidation acid to produce hydrogen gas for the reduction process.
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process produces high-quality GO, followed by thorough Ascorbic acid produces high-quality rGO, and solvents such
washing and purification steps to remove impurities. as benzyl alcohol and dimethylformamide can enhance its
Tour’s method addresses many limitations of earlier electrical conductivity. Hydroiodic acid is another potent
techniques by reducing the generation of toxic gases, reducing agent, producing rGO with excellent conductivity
improving yield, and reducing reaction times, making and mechanical properties when used at high temperatures.
it a more viable option for large-scale production. In Each method varies in effectiveness, environmental impact,
addition, this method allows for controlled and precise and the properties of the resulting material, influencing
functionalization, facilitating the introduction of various its suitability for different applications. One challenge
functional groups onto the surface of GO. 15,27,28 The GOs with chemical reduction is that the process can be slow,
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generated through this method demonstrate enhanced and the reducing agents involved may pose significant
stability against aggregation and restacking, minimizing health hazards. In addition, the resultant rGOs may be
the propensity of irreversible aggregate formation. This nitrogen- or iodine-doped, depending on the method
property is particularly beneficial for the generation of thin used. However, these approaches yield high-quality rGO
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films and coatings. 15,29,30 that can be readily dispersed in a range of solvents, a crucial
feature for numerous beneficial applications. 41
2.5. Other methods
In addition to the established methods, modern techniques 3.2. Biological route
for preparing GO include the use of potassium chromate The biological route refers to an environmentally friendly
with perchloric or nitric acid, as well as preparation method of producing rGO. Plant components such as
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under Jones conditions. Alternatively, potassium ferrate leaves, roots, and seeds contain natural substances – such
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in sulfuric acid. and less toxic methods, such as oxidation as green tea, pomegranate juice, and eucalyptus – that
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with Fe(VI) in water at 50°C or benzoyl peroxide at 110°C, can be used to fabricate rGO. Key elements present in
have also been explored. However, some studies have these extracts, such as polyphenols and flavonoids, engage
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indicated that potassium ferrate is ineffective for GO in reduction reactions by interacting with the epoxy
Volume 3 Issue 3 (2024) 3 doi: 10.36922/gtm.4602