Introduction
Quantum dots-based tissue imaging is an important imaging technique and has
emerged as a promising tool in different types of breast cancer researches due to its
outstanding optical properties. Breast cancer is one of the most common malignant
cancer for women around the world. Breast cancer is a highly heterogeneous disease,
with different biological behaviors for the same stage of breast cancer patients. Optical
imaging is the best method to detect and image lymph systems in case of Breast cancer. Cancer imaging, including macroscopic cancer imaging techniques (magnetic
resonance imaging, (MRI) and microscopic cancer imaging techniques
(immunofluorescence), play critical roles in cancer detection, cancer treatment,
prognosis evaluation, and disease course monitoring. The traditional imaging
techniques is not perfect to acquire more specific and unique information
on Breast Cancer biology—the latest imaging techniques to reveal multi-dimensional
information clearly and precisely is urgently needed in cancer diagnosis. Optical-
based nanoparticles imaging is an important branch of nanotechnology, such as
quantum dots (QDs)-based imaging, which gives a promising potential application in
cancer research. These optical advantages of QDs-based imaging have been widely
applied in cancer researches.
Properties of Quantum Dots (QDs)
The majority of QDs are nanocrystal’s semiconductors with core sizes ranging (2 to
10 nm) composed of two kinds of atoms from the II group and VI group elements of the
periodic table of elements. When QDs are excited by a high external-energy light, the
the internal electron of QDs will excite from its ground state to a higher level, and The high-
level electron relaxes and returns to the ground state during the whole process of a
photon is emitted, producing fluorescence. Bandgap energy is the minimum energy
required to excite an electron from its ground state to a higher level, which is dependent
on the size of the complex; the larger size, the smaller the bandgap. QDs has
narrow emission and wide excitation spectrum advantages; due to the small size, the
entire Quantum dots particle could behave like a single molecule with the atoms exciting
and emitting light simultaneously and producing high signal intensity in the form of a
strong fluorescence.
Biomarker interaction of Quantum Dots
The traditional methods are available to obtain a piece of single biomarker information
at one time, such as immunofluorescence, immunohistochemistry, and Western blotting.
These methods have one common drawback, which is they cannot obtain in situ
quantitative information along with morphological features for multiple biomarkers.
The development of QDs-based multiplexed imaging shows enormous potentials for
in situ multiplexed imaging to reveal the interactions of different molecules. QDs-based
multiplexed imaging has also been used to simultaneously reveal the dynamic
interactions between biomarkers in the tumour microenvironment and cancer cells.
With the event of biology, many prognostic biomarkers hidden in Breast cancer lumps
have been discovered. The accurate quantification and Specific labelling of those
prognostic biomarkers are the key procedure to evaluating Breast Cancer prognosis.
QDs-based imaging and quantitative spectral analysis on biomarkers of Breast cancer
were developed and showed correlation and consistency, with better image quality and
sensitivity. QDs-based imaging was as informative and useful as multi-genes
analysis with lower cost. Quantum based imaging methods could have more
potentials in clinical applications than multi-gene assays, especially in developing
countries where multi-genes analysis is found expensive for patients. These studies
demonstrated that QDs-based multiplexed imaging might be a promising strategy for
more accurate diagnostic pathology.
Quantum Dots – Based Imaging to detect breast cancer
The early detection and Targeted imaging of metastasis in metastatic cancer, the
major cause for cancer mortality, could help initiate effective therapy to improve breast
cancer patient’s prognosis and cancer treatment. Currently used imaging techniques are
difficult to achieve early detection because those imaging techniques can only detect a
tumour when the tumour cells grow up to a normal tissue structure. The QDs-based
imaging could help achieve earlier detection by imaging on cancer tumour cells, even
single tumour cells in vivo. An early metastasis diagnosis that takes place long
before the development of obvious metastasis is known as micrometastasis, and such
micrometastasis is within the diameter range of 0.2 to 2.0 mm, now considered as a
powerful prognostic factor for Breast cancer. Traditional imaging fails to reveal such
micrometastasis due to low resolution. In contrast, QDs could be designed to distinguish
non-target tissues from rare target cells due to their strong fluorescence intensity and
high photostability. Another important advantage of QDs-based imaging for
micrometastasis of Breast cancer is, it can rapidly distinguish between small metastasis
and complex non-tumour tissues because of its strong target imaging and strong
fluorescence.
Limitations
● There are some serious limitations, including inherent toxicity, poor
biocompatibility, and lack of multiplexed imaging.
● The currently used Quantum dots contain heavy metal elements such as Cd, As,
Pb, Te, and Hg, posing potential adverse effects on living systems. The heavy
metal core of QDs could induce early-stage mouse blastocyst death both in vitro
and in vivo.
● The analytical systems should be systematically improved to further promote
their use in cancer research.
