Quantitative gene monitoring of microbial tetracycline resistance using magnetic luminescent nanoparticles.

A magnetic/luminescent nanoparticles (MLNPs) based DNA hybridization method was developed for quantitative monitoring of antibiotic resistance genes and gene-expression in environmental samples. Manipulation of magnetic field enabled the separation of the MLNPs-DNA hybrids from the solution and the fluorescence of MLNPs normalized the quantity of target DNA. In our newly developed MLNPs-DNA assay, linear standard curves (R(2) = 0.99) of target gene was determined with the detection limit of 620 gene copies. The potential risk of increased bacterial antibiotic resistance was assessed by quantitative monitoring of tetracycline resistance (i.e., tetQ gene) in wastewater microcosms. The gene abundance and its expression showed a significant increase of tetQ gene copies with the addition of tetracycline, triclosan (TCS), or triclocarban (TCC). A real-time PCR assay was employed to verify the quantification capability of the MLNPs-DNA assay and accordingly both assays have shown strong correlation (R(2) = 0.93). This non-PCR based MLNPs-DNA assay has demonstrated its potential for gene quantification via a rapid, simple, and high throughput platform and its novel use of internal calibration standards.