Glycosylated gold nanoparticles in point of care diagnostics: from aggregation to lateral flow

Abstract

Current point-of-care lateral flow immunoassays, such as the home pregnancy test, rely on proteins as detection units (e.g. antibodies) to sense for analytes. Glycans play a fundamental role in biological signalling and recognition events such as pathogen adhesion and hence they are promising future alternatives to antibody-based biosensing and diagnostics. Here we introduce the potential of glycans coupled to gold nanoparticles as recognition agents for lateral flow diagnostics. We first introduce the concept of lateral flow, including a case study of lateral flow use in the field compared to other diagnostic tools. We then introduce glycosylated materials, the affinity gains achieved by the cluster glycoside effect and the current use of these in aggregation based assays. Finally, the potential role of glycans in lateral flow are explained, and examples of their successful use given.

Fig. 1. ASSURED acronym, WHO guidelines for the design of POCT.

Fig. 2. Schematic of a prototypical lateral flow device. (A) Device constituents in a successful positive test and (B) a successful negative test. Generic pregnancy tests for HCG detection inset.

Fig. 3. Schematic of strategies for the functionalisation of nanoparticles for use as the mobile phase in lateral flow devices.

Fig. 4. Plasmodium falciparum incidence per 1,000 people, 2017. Image produced using The Malaria Atlas Project, (Malaria Atlas Project, https://malariaatlas.org, (accessed 6 August 2019)).

Fig. 5. Image of negative and positive MRDT, taken from WHO documents.

Fig. 6. Electron micrograph of goat coronary capillary stained with Alcian blue and diagrammatic representation of the glycocalyx highlighting glycocalyx functions. Electron micrograph from van den Berg et al. reproduced from ref. (Figure 75.1.) with permission from publisher Cambridge University Press, copyright 2007.

Fig. 7. Graphical representation of a selection of glycoconjugates in “Table 1” from Lundquist et al. highlighting the maximum enhancement in binding (corrected for ligand valency) as valency changes.

Fig. 8. Macromolecular structure to tune cholera toxin binding. (A) control of cis/trans backbone; (B) GM-1 mimetic polymer through polymer/glycan linker modifications.

Fig. 9. Dynamic combinatorial selection of avid lectin binders using poly-aldehydes and acylhydrazide glycans.

Fig. 10. Representation of the three conceptual methods of polymer grafting to a surface.

Fig. 11. Major nanoparticle design considerations and common lectin analytes for aggregation assays and potential for use in lateral flow assays. Lectin structures were taken from the Protein Data Bank as follows; soybean agglutinin (SBA) – 1SBF, concanavalin A (ConA) – 3CNA, cholera toxin (CTX) – 1XTC, wheat germ agglutinin (WGA) – 2X52 and peanut agglutinin (PNA) – 2DVD.

Fig. 12. (A) Representative structure of glycosylated acrylamide coated AuNPs used by Toyoshima et al. and Ishii et al. (B) Schematic of the flow-through dipstick used by Toyoshima et al. and (C) Schematic of the lateral flow dipstick used by Ishii et al.

Fig. 13. Representative lateral flow glyco-assay and flow through glyco-assay for sensing for SBA (A) and SARS-COV-2 (B) respectively.

Fig. 14. Range of lateral-flow and related assays classes highlighting the stationary phase (SP) test line and mobile phase (MP). (A) Flow-through immunoassay (SP – analyte & MP – antibody-coated AuNP); (B) Lateral flow immunoassay (SP – antibody & MP – antibody-coated AuNP and analyte); (C) Flow-through glyco-assay (SP – analyte & MP – glycan-coated AuNP); (D) Hybrid lateral flow immuno-glyco-assay (SP – antibody & MP – glycan-coated AuNP and analyte); (E) Lateral flow glyco-assay (SP – glycan-functionalised test line & MP – glycan-coated AuNP and analyte).

Alexander N. Baker

George W. Hawker-Bond

Panagiotis G. Georgiou

Simone Dedola

Robert A. Field

Matthew I. Gibson