الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
Study objective was to use Nano-biotechnology in Bio-diagnosis. A recent sensitive accurate methodology for convenient diagnosis of microbial pathogen was established. It was based on gold nanoparticle probe assay using hybridization protocol. A DNA electrochemical biosensor for mecA gene of Methicillin resistant Staphylococcus aureus (MRSA) and eae gene of E. coli O157 was developed. Genomic DNA detection was done by using two protocols, one of them was through cross linking protocol (two probe method) by using two oligonucleotides probes, conjugated to two batches of gold nanoparticles (AuNPs). Each probe was complementary to one end of the target mecA gene. Hybridization of the AuNPs labeled probe to the target genes cause aggregation of conjugated gold nanoparticles and subsequently decrease in inter-particle distance with change of the solution color from pinky red to purple. Other protocol used was non cross linking method (single probe method) in which AuNPs functionalized with one type of oligonucleotides probe, upon the addition target DNA followed by 0.01 N HCl, the conjugated AuNPs resist aggregation so remained pink in positives case while became aggregated in case of negative one with purple color formation. Cross linking protocol was applied for detection of mecA gene of 10 isolates of methicillin resistant Staphylococcus aureus (MRSA), while non-cross linking one was applied for detection of eae gene of 6 isolates of E. coli. O157. Both protocols were applied on 6 standard bacterial strains to conclude specificity of techniques. Statistical analysis showed specificity of 100 % of both methods and highest sensitivity of 90.9 % and 100 % cross linking and non-cross linking technique respectively.