Calorimetric lateral flow immunoassay detection platform based on the photothermal effect of gold nanocages with high sensitivity, specificity, and accuracy

Figures & data

Scheme 1 Schematics of CLFA based on GNCs with high photothermal conversion efficiency and deep penetration ability under NIR irradiation. (A) Conjugation of antibody onto GNCs. (B) Principle diagram of the generation, collection, and detection of heat signal in C-band and T-band of CLFA strips.

Abbreviations: HS-PEG-NHS, Thiol-polyethylene glycol-succinyl imide ester; GNCs, gold nanocages; CLFA, calorimetric lateral flow assays.

Figure 1 Morphology, characterization, and surface modification of AFP-GNCs. (A) the UV-Vis spectra comparison of AFP-GNCs before and after surface modification. (B) and (C) the TEM photographs of bare GNCs and AFP-GNCs, respectively. (D) Energy dispersive spectra (EDS) of AFP-GNCs (red line) and bare GNCs (black line). The inset plots are the element mapping images of AFP-GNCs and bare GNCs. (E) Hydrodynamic diameters and zeta potentials of AFP-GNCs (red) and bare GNCs (black). (F) Atom force microscopy (AFM) characterization of AFP-GNCs and bare GNCs.

Abbreviations: GNCs, gold nanocages; GNPs, gold nanoparticles; AFP, alpha-fetoprotein.

Figure 2 Photothermal effect of AFP-GNCs. (A) Comparison of photothermal conversion efficacy of AFP-GNC dispersions with bare GNC dispersions and control solution: the gold contents of AFP-GNCs and bare GNCs were 0.1 mg Au/mL, and the control solution was ultrapure water. (B) Influence of laser power (λ=808 nm) on the photothermal effect of AFP-GNC strips. (C) Stability evaluation of the photothermal conversion ability of AFP-GNC strips: five repeats of heating/cooling curves of AFP-GNCs strips under NIR laser with the power of 2.0 mW/cm². (D) Photothermal conversion comparison of various volumes of GNCs and GNPs under the NIR laser with the corresponding wavelength (λ=808 nm and 532 nm respectively). (E) Linear dependence on gold contents of signal intensities of GNC-labelled CLFA and GNC-labelled VLFA.

Abbreviations: GNCs, gold nanocages; GNPs, gold nanoparticles; CLFA, calorimetric lateral flow assays; VLFA, visual lateral flow assays.

Figure 3 VLFA for AFP detection. (A) Comparison of GNC-labeled CLFA or VLFA strips of AFP detection. (B) The AFP detection of GNC-labeled CLFA with GNC-labeled VLFA or GNP-labeled VLFA.

Abbreviations: AFP, alpha-fetoprotein; GNC, gold nanocage; GNP, gold nanoparticle, CLFA, calorimetric lateral flow assays; VLFA, visual lateral flow assays.

Table 1 Assay results of AFP clinical serum samples using the CLFA and ELISA methods (n=3)

Sample No.	CLFA (ng/mL)	ELISA (ng/mL)	Relative Deviation
1	16.96±0.50	17.89±0.31	5.2%
2	3.79±0.02	3.68±0.09	−3.0%
3	1.89±0.11	1.93±0.04	2.2%
4	1.55±0.12	1.62±0.05	4.1%
5	9.7±0.44	10.53±0.35	7.9%
6	4.78±0.38	4.74±0.12	−0.8%
7	3.92±0.13	4.03±0.02	2.7%
8	2.96±0.14	2.91±0.05	−1.6%

Abbreviations: AFP, alpha-fetoprotein; CLFA, calorimetric lateral flow assays; ELISA, enzyme-linked immunosorbent assays.

Figure 4 Systematic evaluation of GNC-labelled CLFA strips for rapid detection of ZEN. (A) and (B): influence of chromatographic time and GNC content on CLFA signal intensity, respectively. Normalized CLFA signal intensity of negative sample (gray), positive sample (red), and the ratio of the both (green). (C) and (D): Qualitative specificity and quantitative accuracy of GNC-labelled CLFA strips for ZEN detection, respectively.

Abbreviations: ZEN, zearalenone; DON, vomitoxin; T-2, insariotoxin; AFB1, aLFAtoxin.