Liquid crystal assisted optical DNA biosensor for the selective detection of bacterium Neisseria gonorrhoeae

A highly selective and sensitive label-free liquid crystal (LC)-based optical DNA biosensor has been reported for the detection of bacterial disease. A sensing platform is constructed using nematic LC (4-cyano-4'-pentyl biphenyl) filled in a confined mesh area of transmission electron microscope (TEM) grid placed within a Polydimethylsiloxane (PDMS) well of a fixed dimension for the detection of bacterial infection caused by Neisseria gonorrhoeae. The optical response associated with LC orientation was investigated by using N. gonorrhoeae nucleotide-specific oligonucleotide probe interacting with both the synthetic complementary ssDNA as well as genomic DNA isolated from N. gonorrhoeae under polarised optical microscope. The grey scale area of the resultant POM images was quantised using Image J software and monitored as a function of DNA concentration. The LC-cell has been able to detect the genomic DNA of N. gonorrhoeae bacteria down to the lowest detectable concentration of 10 pM. The optical response studies of LC-biosensor with genomic DNAs isolated from different bacteria showed high specificity and selectivity exclusively for N. gonorrhoeae pathogen and its potential as a convenient, rapid, and reliable label-free detection for gonorrhoea disease.