**5. Application of quantum dots in LFA for detecting non-communicable (chronic) diseases**

#### **5.1 Cardiovascular diseases**

Cardiovascular diseases (CVDs) are disorders related to the heart, such as ischemic heart disease, heart failure, stroke, cerebrovascular diseases, thrombosis, arrhythmia, and cardiomyopathies [55]. N-terminal pro-B-type natriuretic peptide (NT-proBNP) is a diagnostic cardiac biomarker for acute heart failure. However, inadequate products are available in the market for the diagnostic quantification of NT-proBNP. Wilkins and co [21] recently reported on sandwich LFA for NT-pro-BNP. The group used monoclonal antibodies conjugated to QDs via reductive amination. The study showed that conjugating QDs to the antibodies using a site-specific reductive amination strategy exhibited a higher signal at all tested concentrations than LFAs run using EDC-conjugated antibodies. Along with other studies [56, 57], this work verified the potential use of QDs conjugated to CVDs antibodies as a viable means for risk assessment of human cardiovascular diseases.

*Application of Quantum Dots in Lateral Flow Immunoassays: Non-Communicable… DOI: http://dx.doi.org/10.5772/intechopen.107947*

#### **5.2 Cancer**

Cancer is one of the leading causes of death all over the world. An early cancer diagnosis is meaningful and helpful for extending the overall survival of patients. Despite developing highly sophisticated diagnostic tools, these are expensive, timeconsuming, and require complex operations and skilled personnel. Moreover, they are not suitable for the first-line diagnosis. One of the early diagnostic approaches for cancer is to test tumor markers. Carbohydrate antigen 72–4 (CA72–4) is a biomarker linked with the diagnosis and prognosis of early stages of gastric cancer. A CdSe QD labeled sandwich LFA coupled with a charge-coupled device (CCD)-based reader has been reported to detect CA72–4 in clinical samples. Monoclonal CC49 and B72.3 antibodies are often used to detect CA72–4; therefore, to improve the sensitivity of LFA, CC49 was conjugated to the CdSe QDs. The QD-labeled CC49 exhibited narrower emissions with strong fluorescence signals than the QDs alone and proved to be a suitable sensor probe for CA72–4 detection. The QDs-based LFA could sensitively detect CA72–4 at 2 IU/mL levels within 10 min. Furthermore, compared to the Roche electrochemiluminescence assay, the developed strip method has shown excellent reproducibility and specificity [58]. Magnetic-quantum dot nanobeads (MQBs) are composite nanomaterials with distinctive fluorescent and magnetic properties. Antibody-conjugated MQBs are employable in recognizing the immune and can magnetically separate analytes under complex samples. Rong et al., 2019 [22] conjugated MQBS to free prostate-specific antigen (f-PSA) and complexed prostate-specific antigen (c-PSA) as fluorescent probes for prostate cancer. The conjugates were used for immune recognition and simultaneous detection of f-PSA and c-PSA analytes in a complex biological matrix. The developed sandwich LFA detected both antigens (-PSA and c-PSA) on a single test line with high sensitivity and specificity.
