Quantum Dot-based Bio-conjugates as an Emerging Bioimaging Tool for
Cancer Theranostic- A Review
Authors: Priya Lipika , Mehta Smit , Gevariya Darshan , Sharma Raghav , Panjwani Drishti , Patel Shruti , Ahlawat Priyanka , Dharamsi Abhay , Patel Asha 
Published: January 2024

Cancer is the most widely studied disorder in humans, but proper treatment has not yet
been developed for it. Conventional therapies, like chemotherapy, radiation therapy, and surgery,
have been employed. Such therapies target not only cancerous cells but also harm normal cells.
Conventional therapy does not result in specific targeting and hence leads to severe side effects.

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The main objective of this study is to explore the QDs. QDs are used as nanocarriers for diagnosis
and treatment at the same time. They are based on the principle of theranostic approach. QDs can
be conjugated with antibodies via various methods that result in targeted therapy. This results in
their dual function as a diagnostic and therapeutic tool. Nanotechnology involving such nanocarriers
can increase the specificity and reduce the side effects, leaving the normal cells unaffected.

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This review pays attention to different methods for synthesising QDs. QDs can be obtained using
either organic method and synthetic methods. It was found that QDs synthesised naturally are
more feasible than the synthetic process. Top or bottom-up approaches have also emerged for the
synthesis of QDs. QDs can be conjugated with an antibody via non-covalent and covalent binding.
Covalent binding is much more feasible than any other method. Zero-length coupling plays an important
role as EDC (1-Ethyl-3-Ethyl dimethylaminopropyl)carbodiimide is a strong crosslinker
and is widely used for conjugating molecules. Antibodies work as surface ligands that lead to antigen-
antibody interaction, resulting in site-specific targeting and leaving behind the normal cells unaffected.
Cellular uptake of the molecule is done by either passive targeting or active targeting.

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QDs are tiny nanocrystals that are inorganic in nature and vary in size and range. Based on different
sizes, they emit light of specific wavelengths. They have their own luminescent and optical
properties that lead to the monitoring, imaging, and transport of the therapeutic moiety to a variety
of targets in the body. The surface of the QDs is modified to boost their functioning. They act as a
tool for diagnosis, imaging, and delivery of therapeutic moieties. For improved therapeutic effects,
nanotechnology leads the cellular uptake of nanoparticles via passive targeting or active targeting.
It is a crucial platform that not only leads to imaging and diagnosis but also helps to deliver
therapeutic moieties to specific sites. Therefore, this review concludes that there are numerous
drawbacks to the current cancer treatment options, which ultimately result in treatment failure.
Therefore, nanotechnology that involves such a nanocarrier will serve as a tool for overcoming all
limitations of the traditional therapeutic approach. This approach helps in reducing the dose of anticancer
agents for effective treatment and hence improving the therapeutic index. QDs can not only
diagnose a disease but also deliver drugs to the cancerous site.