Nanobioimaging and sensing of infectious diseases

Abstract

New methods to identify trace amount of infectious pathogens rapidly, accurately and with high sensitivity are in constant demand to prevent epidemics and loss of lives. Early detection of these pathogens to prevent, treat and contain the spread of infections is crucial. Therefore, there is a need and urgency for sensitive, specific, accurate, easy-to-use diagnostic tests. Versatile biofunctionalized engineered nanomaterials are proving to be promising in meeting these needs in diagnosing the pathogens in food, blood and clinical samples. The unique optical and magnetic properties of the nanoscale materials have been put to use for the diagnostics. In this review, we focus on the developments of the fluorescent nanoparticles, metallic nanostructures and superparamagnetic nanoparticles for bioimaging and detection of infectious microorganisms. The various nanodiagnostic assays developed to image, detect and capture infectious virus and bacteria in solutions, food or biological samples in vitro and in vivo are presented and their relevance to developing countries is discussed.

Fig. 1

Fluorescence emission spectra of Fort Orange Qdots before conjugation to IgG antibody (A), after conjugation (B), and after binding increasing amounts of B. subtilis variant niger spores (C,D).

Fig. 2

Test strip assay format. CT in the reaction mixture binds to the gangliosides on the liposome surface. The CT–GM1-liposome complex migrates through the nitrocellulose test strip by capillary action until it reaches the analytical zone, where toxins in the complex are captured by immobilized antibodies. This binding zone is shown as the dark band on the test strip.

Fig. 3

Barcoded metallic nanowires for multiplexed biodetection. (A) Nanowires with different patterns of Au and Ag segments are functionalized with different molecular beacon probe sequences, which are nonfluorescent in the absence of target strands. When a mixture of target molecules, in this case complementary to probes 1 and 2, is incubated with the mixture of barcoded nanowires, (B) some nanowire-bound probes become fluorescent because of complementary target binding. Reflectance and fluorescence microscope images are acquired for the identification of nanowires and quantification of fluorescence, respectively, and (C) mean fluorescence intensities are calculated from populations of individual nanowires of each barcode pattern, to quantify the amount of each target present.

Fig. 4

Schematic of the bio-barcode assay: (A) formation of MNP-2nd DNA probe/target DNA/1st DNA probe-Au NPs-barcode DNA; (B) barcode DNA separation and release.

Fig. 5

Representation of the vancomycin-d-alanyl–d-alanine interaction responsible for mediating the interaction between the NPs and the bacteria. The critical components for the strong H-bonding interaction both on the vancomycin molecule (the heptapeptide backbone) and the d-alanyl–d-alanine dipeptide exposed from the bacterial surface are highlighted.