Visual and spectrophotometric nanobiosensor for Leishmania infantum detection based on kinetoplast DNA probe

Leishmaniasis is one of zoonotic tropical diseases and includes cutaneous, mucocutaneous, and visceral types. The agent of the visceral leishmaniasis (VL) in the Mediterranean region is Leishmania infantum, which may cause death if not diagnosed and treated promptly. A DNA biosensor based on gold nanoparticles has been fabricated for detection of L. infantum genome, based on Kinetoplast minicircle DNA with conserved sequence region. Initially, DNA samples were prepared from a number of patients and dogs with VL, as well as negative and positive controls. A thiolated 24-base oligonucleotide probe from kDNA was functionalized with AuNPs (AuNP-probe). AuNP-probe was then exposed to the solution containing target and non-target DNA for the hybridization. Dispersion or aggregation of the gold nanoparticles-probe conjugates in the presence or absence of a complementary DNA sequence, L. infantum genomic DNA, and clinical samples resulted in an obvious and sensitive change in the UV-vis spectra and the solution color, after acid addition. A red color for the samples containing complementary DNA was observed, whereas in the samples without complementary DNA, AuNP-probe turned blue-purple. The results indicated that this method is an easy, reliable, direct, rapid and cost-effective method for visual detection of L. infantum. A larger clinical cohort will need to be evaluated using this nanobiosensor to confirm its reliability and practical application. After validation with future studies, this nanobiosensor has potential for evolution into a portable diagnostic tool.