According to the World Health Organization, cervical cancer is the fourth most common cancer experienced by women worldwide, accounting for 342,000 deaths in 2020. Early detection is important for successful treatment, but current screening methods are invasive and may be uncomfortable for patients.
How Does Cervical Cancer Develop?
Cervical cancer is a type of cancer that starts in the cells of the cervix, the lower, narrow end of the uterus. Cervical cancer usually develops over time. Before it appears in the cervix, the cells undergo changes called dysplasia, where abnormal cells appear in the cervical tissue. Over time, the abnormal cells may become cancer cells if not destroyed or removed, growing and spreading more deeply into the cervix and to surrounding areas.
Cervical cancers are named after the kind of cell where the cancer started. In squamous cell carcinoma, the cancer develops from cells located in the ectocervix. Meanwhile, adenocarcinoma develops in the glandular cells of the endocervix.
Most cases of cervical cancer are caused by strains of human papillomavirus (HPV), a common infection passed through sexual contact. When a person is exposed to HPV, their body's immune system prevents the virus from doing any harm. However, the virus may survive for years in a small percentage of people. This can contribute to the process where cervical cells develop into cancer cells.
READ ALSO : Nearly Half Of Adults In The US Are Infected With HPV, Most Of Them Are Now Prone To Cancer
Novel DNA Biosensors
At Chung-Ang University in Korea, a team of scientists developed an electrochemical DNA biosensor with enhanced sensitivity to detect HPV effectively. This was done using a graphitic nano-onion/ molybdenum disulfide nanosheet composite, which shows enhanced conductive electron transfer compared to the nanosheet alone. This discovery can give way to developing biosensors for early diagnosis of different diseases.
Molybdenum disulfide (MoS2) has gained the interest of materials scientists due to its ability to form two-dimensional nanosheets that resemble graphene. These nanosheets are created from stacked S-Mo-S layers connected with Van der Waals interactions. MoS2 is also known for its unique optical, structural, thermal, and electrochemical properties, which open research opportunities in optoelectronics, chemical detection, batteries, biomolecule sensing, and supercapacitors.
Carbon nanostructures have been traditionally used as an immobilization platform for DNA. To replace carbon with MoS2 as an effective electrochemical DNA sensor, the electrical conductivity of MoS2 must be enhanced.
Associate Professor Eunah Kang and Mr. Youngjun Kim from the School of Chemical Engineering and Material Science at Chung-Ang University proposed a novel solution to address this challenge. They developed an electrochemical DNA biosensor that uses a graphitic nano-onion/ molybdenum disulfide (MoS2) nanosheet composite.
Nano-onions are known for possessing graphitic sp2 structures obtained from crystalline sp3-nanodiamonds through thermal annealing or laser irradiation. The researchers prepared the novel electrode surface for probing DNA chemisorption by enabling chemical conjugation between two functional groups. These include acyl bonds on functionalized nano-onions' surfaces and amine groups on the modified MoS2 nanosheets.
The sensitivity of the novel DNA biosensor was measured towards HPV using the differential pulse voltammetry (DPV) method in the presence of methylene blue as a redox indicator. It was found that the proposed sensor targets DNAs produced from HPV-16 and HPV-18 Siha and Hela cancer cells effectively and with high specificity. MoS2 nanosheets with enhanced electrical conductivity facilitated by complexation with nano-onions are suitable for developing efficient electrochemical biosensors.
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