Issue 25, 2016

Multi-scale magnetic nanoparticle based optomagnetic bioassay for sensitive DNA and bacteria detection

Abstract

Benefiting from their rapid readout, highly flexible devices and low-cost portable systems, optomagnetic biosensors have drawn increased attention in recent years as bioassay technologies for small molecules, biomarkers, DNA, and bacteria. Herein, an optomagnetic bioassay strategy suitable for point-of-care diagnostics, utilizing functionalized magnetic nanoparticles (100 nm) with Brownian relaxation behavior is optimized in order to obtain higher detection sensitivity for DNA molecules and bacteria. Presence of target DNA sequences or bacteria changes the dynamic behavior of the magnetic nanoparticles (binding to the target) and thus the optomagnetic response of the sample, which is measured by an optomagnetic setup including a 405 nm laser and a photodetector. The limit of detection is mainly set by the lowest measurable concentration of magnetic nanoparticles. Herein, as new results compared to previous work, we systematically optimize the concentration of 100 nm magnetic nanoparticles to increase the assay sensitivity and lower the limit of detection. To enable biplex detection, we perform this optimization in the presence of larger 250 nm magnetic nanoparticles that do not interact with the target. We show that the optimization and lowering of the 100 nm magnetic nanoparticle concentration result in a limit of detection of 780 fM of DNA coils formed by rolling circle amplification (size of about 1 μm) and 105 CFU per mL Salmonella (for immunoassay). These values are 15 times lower than those reported previously for this readout principle. Finally, we show that the 250 nm magnetic nanoparticles can serve as a second detection label for qualitative biplex detection of DNA coils formed by rolling circle amplification from V. cholerae and E. coli DNA coils using 100 nm and 250 nm magnetic detection nanoparticles, respectively.

Graphical abstract: Multi-scale magnetic nanoparticle based optomagnetic bioassay for sensitive DNA and bacteria detection

Supplementary files

Article information

Article type
Paper
Submitted
11 Mar 2016
Accepted
02 Jun 2016
First published
03 Jun 2016
This article is Open Access
Creative Commons BY license

Anal. Methods, 2016,8, 5009-5016

Multi-scale magnetic nanoparticle based optomagnetic bioassay for sensitive DNA and bacteria detection

B. Tian, T. Zardán Gómez de la Torre, M. Donolato, M. F. Hansen, P. Svedlindh and M. Strömberg, Anal. Methods, 2016, 8, 5009 DOI: 10.1039/C6AY00721J

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements