| In this study, Piezoelectric-Excited Millimeter-Sized Cantilever (PEMC) sensors were used to detect pathogens and disease conditions using DNA-based detection technique. Using Stx-2 gene as a unique identifier, the model pathogen E. coli O157:H7 was detected using a simplified and rapid genomic DNA extraction method (30 min) in both buffer and proteinous complex matrix at ∼2,000 pathogens per mL. Single Nucleotide Polymorphism (SNP) of DNA of length 10 to 60 nt were detected via nucleic-acid hybridization at 1 femtomolar concentration. Synthetic single stranded DNA, 10 to 288 bases long were detected by hybridization. For the first time, Taq-polymerase based extension of captured DNA was performed on the cantilever sensor thus increasing hybridized mass by ∼2.2 pg. The PEMC sensor showed high specificity in detecting complementary DNA in presence of 10,000 times higher concentration noncomplementary DNA strands. Using antibody-antigen assay, E. coli O157:H7 was detected at 10 cells/mL and developed a protocol for regeneration of the sensor surface for multiple uses. Another significant result is the measurement of alkanethiol chemisorption on Au coated sensor surface at 1 femtomolar. At higher alkanethiol concentrations the sensor responses were proportionately, but non-linearly, higher. However, the responses to C4, C8, C11, C16 and C 18 alkanethiols at 1 mM were linearly proportional to their molecular weights. We report for the first time that, once the Au-surface is equilibrated at 1 pM, further chemisorption at a lower concentration does not take place, even though over 99% of adsorption sites is vacant. |
