Hydrothermal Synthesis of Fluorescent Nitrogen-doped Carbon Nanodots

“One-pot green hydrothermal synthesis of fluorescent nitrogen-doped carbon nanodots for in vivo bioimaging.”

Summary

The rationale of the study carried out by Kuo et al. (2016) is to establish the potential for developing an applicable bioimaging contrast agent. Indeed, to achieve this end, the researchers applied one-pot green synthesis. The experiment followed treatment of biocompatible polyvinylpyrrolidone (PVP) and glycine using hydrothermal process to come up with fluorescent nitrogen-doped carbon nanodots (CNDs). To get their results, Kuo et al. (2016) used various materials in confirming the identified nature of the CNDs. The researchers used UV-vis spectroscopy as one of the materials as well as fluorescence spectroscopy. They also used Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). Raman spectroscopy was the last material used in the experiment. An in vivo imaging system (IVIS) was used in which the agent was injected into the lungs. At 12- and 24-h post-injection, a fluorescence signal of the CNDs was visibly observable.

Use of the simplistic and green synthetic mechanism in preparing the fluorescent nitrogen-doped CNDs revealed that the agent has some qualities. The nitrogen-doped CNDs that were obtained in the process showed evidence of emissions of strong blue fluorescence. The agent, fluorescent nitrogen-doped CNDs, was revealed to have a high rate of water solubility. It was also revealed to show superior salt stability and rated low in cytotoxicity. The evident of the last property was shown in low concentration for the bioimaging contrast agent use. In addition, the fluorescence of nitrogen-doped CNDs’ tunable and up-conversion aspects could be related with an advantage in the choice of the appropriate emission as well as excitation energy for the in vivo imaging using the fluorescence agent. Based on these properties, it would be concluded that the agent was highly suitable for biological imaging. From their findings, the authors made the weighing up that synthesized CNDs could be applicable for intracellular tests based on the high level of biocompatibility.

In addition, it is evident that the green synthetic as well as a facile approach has been recognized to organize doped fluorescent nitrogen CNDs from the glycine and biocompatible PVP. The result also indicated that the obtained CNDs (nitrogen doped) emitted a strong fluorescence (strong blue), which recorded a maximum of 21.43% of quantum yield at the excitation of 340nm in terms of the wavelength. On the other hand, the fluorescent nitrogen-doped also demonstrated good salt, high solubility of water, and low toxicity based on the low concentration for the bioimaging contrast agent usage.

Advantages

The CNDs (nitrogen doped) has many advantages founded on the properties, which are clearly identifiable in its preparation. The properties of CNDs usually combine with hyaluronic acid as well as homologues. As such, together with composite CNDs (HA-CDs) and hyaluronic acid, they form hyaluronic acid imaging in vivo. The process used in the preparation of fluorescent nitrogen-doped carbon nanodots (CNDs) as well as the use of the agent in vivo fluorescence imaging provides evidence of a procedure that is easy to follow, beginning from the acquisition of the materials used in the experiment; Polyvinylpyrrolidone (PVP), glycine, H3PO4, NaH2PO4, Na2HPO4, and Na3PO4. Thus, use of the agent is beneficial given the ease within which can be prepared. For the purpose of bioimaging, researchers and practitioners can easily acquire the materials, Polyvinylpyrrolidone (PVP), glycine, H3PO4, NaH2PO4, Na2HPO4, and Na3PO4, prepare the CNDs in the lab, and use it in practice. Kuo et al. (2016) indicate that the synthesized CNDs can be applied in intracellular imaging based on their excellent biocompatibility. For potential application, the practitioner will understand the initial preparation of the agent and further how to inject it within the cell in the imaging process.

Another benefit of using the nitrogen doped CNDs is usually a novel nanomaterials, which display fundamental fluorescence properties. Therefore, they have various applications in many fields that involve biological and chemical sensing, drug delivery, biological imaging, and photocatalysis among other areas, which are very promising in the future development (Li et al., 8152). The exceptional optical as well as electronic characteristics of the CNDs are applicable in biomedical, electrochemical, as well as photochemical use. The research reveals that as long as there is a fluorescence contrast agent, it is possible to provide an element applicable to optical imaging in vitro. In addition, an image useful in vitro can also be useful for in vivo as revealed in the study by Kuo et al. (2016). The sole critical factor to consider is that the agent has the identified characteristics, good salt stability, high solubility of water, and low toxicity. The use of the agent with such properties are many, including labelling the cell membrane as well as the COS-7 cells’ cytoplasm in confocal imaging, labeling the cell membrane as well as MCF-7 cells’ cytoplasm, labeling of A549 cells, and in bioimaging using fluorescent CNDs instead of conventional organic dyes.

Disadvantages

There are various challenges connected to “One-pot green hydrothermal synthesis of fluorescent nitrogen-doped carbon nanodots for in vivo bioimaging.” First, near the infrared (NIR), there is a lesser amount of scattering through the tissues. The negative aspect of the agent affects its usability in in vivo applications such as bioimaging. It is critical for such processes that an agent is used with a high level of scattering within the tissue in order to image the entire internal aspects of the target cell. Also, the absorption is affected based on the tissue Hb, which might be difficult to control before using the agent. There is also the issue of skin flab or dorsal skin fold. Another issue associated with the use of fluorescent nitrogen-doped CNDs relates to their yield. Although the green hydrothermal synthesis of CNDs has been shown to provide an agent with the desirable characteristics for bioimaging in vivo, the problem is that the procedure has not provided an amount adequate for successful use (Li et al., 8152). While success is shown for in vitro applications, the synthesis and application protocols of CNDs using the green hydrothermal synthesis are still inadequate for in vivo applications.

Suggestions

The topic “One-pot green hydrothermal synthesis of fluorescent nitrogen-doped carbon nanodots for in vivo bioimaging” is recommended in various fields and the process should be encouraged for what lies ahead. In essence, the topic is promising and should cover the following areas, including, drug disposition, phototherapy, imaging efficacy of the drug, diagnostics, as well as nano-surgery. However, for success to be achieved, there are areas that should be improved. Researchers should devise effective procedures to attain adequate yields for application in vivo imaging. The reality is that the most important factor in successful bioimaging application is the use of a high fluorescence quantum yield (Zhu et al., 380). Future research should consider the use and application of surface passivation and heteroatom doping to get higher yields.