Development of an Aptamer Based Luminescent Optical Fiber Sensor for the Continuous Monitoring of Hg²⁺ in Aqueous Media

• Main Authors: Nerea De Acha, César Elosúa, Francisco J. Arregui
• Format: Article
• Language: English
• Published: MDPI AG 2020-04-01
• Series: Sensors
• Subjects: optical fiber biosensor; luminescent biosensor; fluorophore-labelled aptamer; mercury detection
• Online Access: https://www.mdpi.com/1424-8220/20/8/2372
• ISSN: 1424-8220

A fluorescent optical fiber sensor for the detection of mercury (Hg²⁺) ions in aqueous solutions is presented in this work. The sensor was based on a fluorophore-labeled thymine (T)-rich oligodeoxyribonucleotide (ON) sequence that was directly immobilized onto the tip of a tapered optical fiber. In the presence of mercury ions, the formation of T–Hg²⁺-T mismatches quenches the fluorescence emission by the labeled fluorophore, which enables the measurement of Hg²⁺ ions in aqueous solutions. Thus, in contrast to commonly designed sensors, neither a fluorescence quencher nor a complementary ON sequence is required. The sensor presented a response time of 24.8 seconds toward 5 × 10⁻¹² M Hg²⁺. It also showed both good reversibility (higher than the 95.8%) and selectivity: the I₀/I variation was 10 times higher for Hg²⁺ ions than for Mn²⁺ ions. Other contaminants examined (Co²⁺, Ag⁺, Cd²⁺, Ni²⁺, Ca²⁺, Pb²⁺, Mn²⁺, Zn²⁺, Fe³⁺, and Cu²⁺) presented an even lower interference. The limit of detection of the sensor was 4.73 × 10⁻¹³ M Hg²⁺ in buffer solution and 9.03 × 10⁻¹³ M Hg²⁺ in ultrapure water, and was also able to detect 5 × 10⁻¹² M Hg²⁺ in tap water.