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Leptospirosis detection using tapered optical fiber biosensor

30 Apr | By Biophotonics.World
Leptospirosis detection using tapered optical fiber biosensor
Left to right: Nurul Hida Zainuddin and Mohd Hanif Yaacob developed a tapered optical fiber biosensor to detect Leptospirosis. Inset: Schematic of the tapered optical fiber coated with aldehyde coatings as a DNA biofunctionalized layer.
By: Mohd Hanif Yaacob

Leptospirosisis a deadly disease with common early flu-like symptoms. Leptospirosisin human is caused by bacteria known as Leptospira. The infection is resulted from direct or indirect contact with contaminated urine, water or soil from infected animals especially rodents. Once infected, human has vague clinical signs with other infectious diseases and makes them likely to be under-diagnosed. Without early treatment, the patient may enter a more severe stage, which could lead to kidney failure, meningitis, liver failure, respiratory distress, and even death. Recently, there is a major concerns due to sharp rise reported for the Leptospirosis infection specifically in the developing and tropical countries. Culture and microscopic agglutination test (MAT) are gold standard methods for Leptospirosis diagnosis. However, these methods are inadequate for early diagnosis. In the case of Leptospira culture, the colonies are slow-growing bacteria and for MAT, the anti-Leptospira antibodies can only be detected by the second week after onset of symptoms. Therefore, there is an urgent demand for highly sensitive, selective and early detection system towards Leptospirosis.

Researchers from Wireless and Photonics Networks (WiPNET) Research Centre of Excellence, Universiti Putra Malaysia (UPM) has developed a sensitive and specific optical sensing system using tapered optical fiber to detect Leptospira DNA. Tapered optical fiber is a modified single mode optical fiber (SMF) by tapering or shrinking process to enhance the light evanescent field interaction with the outer surroundings. The operation of tapered optical fiber sensing platform is based on the change in light propagates in its core upon hybridization of the Leptospira single strand DNA to a capture probe DNA. 

Prior detection, the tapered region of the optical fiber is first bio-functionalized to bond the DNA molecules onto the tapered surface. The specific capture probe DNA is designed to hybridize with target Leptospira DNA like a lock and key system. The detection signal of the hybridization is representing by optical wavelength shift. It is discovered that the shift of the light wavelength is linearly proportional with the increase in the target LeptospiraDNA concentrations. The sensitivity of the biosensor toward DNA is measured to be 1.2862 nm/nM and able to detect as low as 0.1 fM (femtomolar). The excellent sensitivity is achieved by tapering the optical fiber diameter from its standard dimension of 125 μm to 12 μm. The innovation in the Leptospira DNA biosensor using tapered optical fiber is highly potential for in-situ, fast and sensitive bio-sensing applications. 

Author: Mohd Hanif Yaacob

Related journal article:  https://doi.org/10.1002/jbio.201870153


Area of application: Molecular diagnostics, Therapeutics
Methods and Techniques: Probe and sensor development

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