When you use the electrochemical biosensor combines with DNA or RNA, what's kind of interference for the electrochemical biosensor?  How to reduce it?

Electrochemical biosensor can combine with DNA or RNA for two purposes: (1) when we want to capture disease biomarkers in which DNA or RNA perform function like antibody to capture/conjugate with specific disease biomarkers (thrombin, troponin, lipopolysaccharide, etc. and cancer biomarkers) followed by electrochemical detection. In these cases, specific sequences of DNA or RNA which is capable of selectively capture biomarkers is selected based on systematic evolution of ligands by exponential enrichment (SELEX), which is a combinatorial chemistry technique in molecular biology for producing oligonucleotides of either single-stranded DNA or RNA that specifically bind to a target ligand or ligands; (2) when we want to detect specific pathogen like bacteria, virus or genetic disorders on the basis of genetic element itself with hybridization techniques. In these cases, unique nucleotide sequences of target organisms are selected using bioinformatics tools. The designed primer/ probe will only be perfectly hybridised with target but not with any other else.   

In electrochemical biosensor, owing to interaction between sensor and ligand some electrochemical parameters (production of ions or electrons and change in conductance or resistance) changes which is measured electrochemically. Therefore, if any analogue to target molecule exists in buffer or sample, it may interfere with measured data. Beside this, if SELEX is not properly employed, biosensor may capture addition compound along with target one which may be reflected on measurable parameters. Interference may come from wrong selection of primer/probe nucleotide sequence. In addition, improper selection of fabrication platform (electrode and nanomaterial) and lack of optimization of reaction parameters (hybridization temperature, pH, buffer etc.) may interfere with results.

In order reduce the interference, unique nucleotide selection should have first priority. For example, in case of SELEX for biomarker detection, trial should be given with targeting all possible ligand in raw sample and best combination be selected among them targeting desired one. In case of hybridization process, after alignment of relevant sequences and selection of specific sequences as primer/probe, additional blast in NCBI is required to authenticate its uniqueness. Others reaction parameters should be optimized, and noise should be minimized case by case basis carefully.

I would like to know the biosensor of your research in the future can apply to investigate the COVID-19 or not? and how to?

How about the sensitivity of this biosensor? and what is the limitation of the test? 

I would like to know the biosensor of your research in the future can apply to investigate the COVID-19 or not? and how to?

Thank you for your interest. Biosensor can be applied to investigate COVID-19. For that specific primer/probe should be designed based on the genome sequence of COVID-19. After immobilization on electrode surface with specific aid, primer/probe act as capturing element for target COVID-19.

How about the sensitivity of this biosensor? and what is the limitation of the test?

Thanks DR. SANI BOONYAGUL for your interest.

Sensitivity of electrochemical nucleic acid Biosensor varies from nM to fM depending on the target analytes such as disease biomarkers, pathogen (virus, bacteria) types etc. and electrochemical detection techniques (Voltammetry, amperometry, impedimetry, potentiometry and conductimetry). The sensitivity of electrochemical nucleic acid biosensor is better than or at least comparable to allied existing detection methods.

Each of these biosensor types has limitations based on the intended application and the parameters which are obligatory for optimal performance. The choice of biosensor design must consider factors such as the ligand specificity, sensitivity, dynamic range, functional range, mode of output, time of activation, ease of test. For better performance, chemisorption of molecules on the conductive surface, quality of the semiconductor material and improvement of the signal-to-noise ratio to be considered actively. Some technical barriers biosensor for test include reproducibility and shelf life which are not up to the mark. Although many challenges must still to overcome, electrochemical nucleic acid biosensor have great potential.