Alfaisal University

Shimaa Eissa

Mohammed Zourob

Raja Chinnappan

Ayesha Siddiqua

Maher M Aljohani

A method and process to make and use cotton-tipped electrochemical immunosensor for the detection of corona viruses is described. The immunosensor were fabricated by immobilizing the virus antigens on carbon nanofiber-modified screen printed electrodes which were functionalized by diazonium electrografting and activated by EDC/NHS chemistry. The detection of virus antigens were achieved via swabbing followed by competitive assay using fixed amount of antibody in the solution. Ferro/ferricyanide redox probe was used for the detection using square wave voltammetric technique. The limits of detection for our electrochemical biosensors were 0.8 and 0.09 pg/ml for SARS-CoV-2 and MERS-CoV, respectively indicating very good sensitivity for the sensors. Both biosensors did not show significant cross reactivity with other virus antigens such as influenza A and HCoV, indicating the high selectivity of the method.

Method and process to make and use cotton-tipped electrochemical immunosensor for the detection of corona virus

The developed long and short aptamer sequences can be used as high affinity and specificity tools to analyze the drug Dabigatran etexilate for therapeutic drug monitoring, pharmacokinetic and naturalization studies. Using the technique by performing several rounds of selection and enrichment with a randomized 60-mer DNA library, a number of specific aptamer sequences were successfully selected for Dabigatran etexilate. We evaluated the binding affinity and specificity of the generated aptamers showing dissociation constants (k) ranging from 47-312 nM and very weak or no cross-reactivity to other analytes. Complimentary sequences labelled with a fluorophore and a quencher was used for mapping the binding region within the aptamer by monitoring the change in the fluorescence signal. A truncated sequence was used to construct a turn-on fluorescence sensor. The application of the long and short sequences in electrochemical and fluorescence sensors, respectively implying the usefulness of these aptamers in Dabigatran etexilate diagnostics applications and has unique potential of clinical uses in the near future.

Full-length and truncated anti-coagulant Dabigatran etexilate specific DNA aptamers for electrochemical and fluorescence sensing applications

An electrochemical screening method for the selection of DNA aptamers against 11-deoxycortisol (11-DCL) using gold electrode for target immobilization is described. The gold electrode is used as solid matrix instead of the beads for SELEX. The selection steps (SELEX) are performed on the 11-DC modified electrode directly as the DNA library in the first round or the enriched DNA pools in the subsequent rounds were incubated on the electrode, then the unbound DNA is washed and the bound DNA is measured directly by square wave voltammetry. Then elution of the bound DNA is performed for further use.

Electrochemical screening for the selection of DNA aptamers

High affinity DNA aptamers Seq ID#1-8 for HbA1C and tHb were successfully selected using SELEX after 11 rounds of selection. The tested aptamers bind to HbA1C with dissociation constants in the nanomolar range with the highest affinity aptamer, Seq ID#6, exhibiting a Kof 2.8 nM. Another aptamer sequence (Seq ID #4) which showed high binding affinity to tHb with a Kof 2.7 nM was also selected. The HbA1C and tHb-specific aptamers were then applied for the detection of HbA1C % using a voltammetric aptasensor array platform showing remarkable sensitivity and selectivity. The aptasensor array platform was validated using standard human whole blood samples and demonstrated linearity over wide concentration range. The developed platform is superior to current methodologies due to its simplicity, stability and lower cost which will facilitate the early and accurate diagnosis of diabetes.

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Riyadh, Saudi Arabia

Shimaa Eissa