ABSTRACT
Enzymatic amplification-free DNA detection for point-of-care (POC) in vitro diagnostics is still a challenge due to the lack of sensitive DNA-detection methods that can be seamlessly automated and integrated into portable platforms. Herein, we present a sensitive yet simple DNA-detection method using an ultrabright surface-enhanced Raman scattering (SERS) tag, the nanorattle. The method involves sandwich hybridization of magnetic beads that have capture probes, target sequences, and ultrabright SERS nanorattles that are loaded with reporter probes. The nanorattle has a core–gap–shell structure with resonance Raman reporters loaded in the gap space between the core and the shell. Nanorattles’ SERS intensity is three orders of magnitude brighter than gold nanospheres coated with the same Raman reporters. Using the method described here, a specific DNA sequence of the malaria parasite Plasmodium falciparum could be detected with a detection limit of ∼3 pM, equivalent to ∼100 attomoles. Differentiating between wild-type malaria DNA and mutant malaria DNA, which has a single nucleotide polymorphism (SNP) conferring resistance to artemisinin drugs, was also demonstrated. The results demonstrate the potential of the nanorattle-based method for in vitro diagnostics, in which infectious pathogens can be both detected and genotyped. The use of magnetic beads and the method's simplicity makes it a suitable candidate for automation and integration into lab-on-a-chip systems for POC applications.
