5TH International Congress on Technology - Engineering & Science - Kuala Lumpur - Malaysia (2018-02-01)

Reflectance Spectrophotometric Dna Biosensor Based On Metal Complex Intercalator

A new nucleic acid biosensor model based on binding and interaction of Schiff base metal salphen complex as optical DNA hybridization label has been developed. The binding and interaction of Schiff base metal salphen complex as optical DNA label allowed naked-eye detection of targeted DNA via solid-state DNA hybridization chemistry, which has been optimized by using reflectance spectrophotometric method. Due to the square planar geometry and aromatic ring structured characteristics of the metal complex intercalators, they could intercalate between DNA bases via π-π stacking interaction, and rendered a yellowish pink hue on the DNA biosensor surface. Current clinical diagnosis of dengue virus infection in human is based on serological test that involves virus isolation in cell culture, therefore must be performed in the laboratory with the necessary infrastructures and technical expertise. Furthermore, detection and classification of dengue virus via serology test usually takes several days or may be longer than a week or two. Non-structural 1 (NS1) protein antigen detection kits are commercially available, and can yield result within a few hours. However, the assays are not type-specific, and required specific equipment and expensive. Dengue IgM ELISA kit, which is designed for quantitative measurement of IgM antibody in human serum would normally require about five days for the patient to produce a detectable level of anti-dengue antibodies, and this test requires expensive ELISA facilities and high reagent consumption. In general, the currently available commercial technologies employed in the dengue virus detection appeared to be laboursome, low sensitivity, expensive and invasive as blood sample is usually required. The proposed optical DNA biosensor can be employed as the solution to these limitations, based upon semiquantitative visual colour inspection of dengue virus DNA immobilized on the DNA biosensor. As the DNA probe is selective towards its complementary target DNA, thus visual monitoring of dengue DNA in non-invasive human bodily fluids (e.g. urine and saliva samples) would permit rapid diagnosis of dengue infection in human as fast as the first day of illness onset. The present study employed 16-mer oligopeptide as the probe specific for dengue serotype 2 detection as it causes more severe disease than do other serotypes in Southeast Asia countries. The nanostructural feature of the silica nanoparticles (SiO2NPs) DNA solid support substrate has promoted the mass transfer of the DNA molecules, and that providing high sensitivity and rapidity in DNA detection. The optical DNA biosensor demonstrated a linear reflectance response between 1 fM and 10 pM complementary DNA (cDNA) concentration (R2=0.9975) with a fast DNA hybridization time of 30 min and a limit of detectable (LOD) DNA concentration as low as 1 zM. In addition, this biosensor showed stable shelf life for a 20-day operational duration and was reusable for five consecutive DNA testing. In addition, the proposed optical DNA biosensor offered a far superior biosensing performance compared to previously reported electrochemical DNA biosensors for early diagnosis of dengue virus infection in human. Keywords: metal salphen complex, DNA biosensor, fibre optic reflectance Spectrophotometer, optical DNA label.
Ling Ling Tan, Nur-Fadhilah Mazlan, Nurul Huda Abd. Karim