A colloidal gold immunochromatography test strip based on a monoclonal antibody for the rapid detection of triadimefon and triadimenol in foods

Figures & data

Figure 1. The structural formula of triadimefon (TDF) and triadimenol (TDN).

Figure 2. Synthesis of TDF hapten.

Figure 3. Identification of the molecular structure of TDF hapten: (A) total ion chromatogram (TIC) of TDF hapten; (B) extract ion chromatogram (EIC) of TDF hapten; (C) mass spectrum of TDF hapten.

Figure 4. The ultraviolet absorption spectrum of TDF hapten-BSA (A) and TDF hapten-OVA (B).

Figure 5. (A) The composition of colloidal gold test strip; (B) Principle of the CG test strip.

Table 1. The titres and inhibition of antisera screened by ic-ELISA.

			Titres (1:X)			(B0-B)/B0 × 100%
			Mouse 1	Mouse 2	Mouse 3	Mouse 1		Mouse 2		Mouse 3
Immunogen (X:1)	Dose (μg)	Standard (ng/mL)				TDF	TDN	TDF	TDN	TDF	TDN
TDF hapten-BSA	50	500	9000	27000	27000	65	53	69	45	59	58
(40:1)	50	200	27000	27000	27000	58	51	60	50	52	55
	50	100	81000	81000	81000	51	54	53	49	62	48
TDF hapten-BSA	50	500	27000	27000	9000	67	69	72	54	55	50
(80:1)	50	200	81000	81000	27000	60	67	67	58	59	61
	50	100	81000	243000	81000	55	59	73	55	51	59

Figure 6. The optimization of ic-ELISA: (A) the pH (4.0, 6.0, 7.4, 8.8 and 9.6) of coating buffer; (B) the ionic strength (0%, 0.4%, 0.8%, 1.6% and 3.2%, w/v); (C) DMF content (0%, 2%, 4%, 8% and 10%) of the standard diluent.

Figure 7. The indirect competition inhibition curves (A) (B) and cross reaction (C) of the MAb.

Table 2. The detection of cross reaction by ic-ELISA.

Chemicals	Structures	IC50 (ng/mL)	Cross reaction rate (%)
Triadimefon		5.00	100
Triadimenol		10.00	50
Cyproconazole		>500.00	<2
Propiconazole		>500.00	<2
Hexaconazole		>500.00	<2
Diniconazole		>500.00	<2
Myclobutanil		>500.00	<2
Bitertanol		>500.00	<2

Figure 8. Images of TDF and TDN detection by CG test strip in tomato sample: (A) tomato sample spiked with TDF; (B) tomato sample spiked with TDN; (C) tomato sample spiked with TDF mixed with TDN (1:1, w/w). A series of tomato samples spiked with TDF and TDN were tested by colloidal gold test strip: 1=0 ng/g, 2=10 ng/g, 3=25 ng/g, 4=50 ng/g, 5=100 ng/g and 6=250 ng/g.

Table 3. Analysis of TDF, TDN and TDF mixed TDN in tomato sample by ic-ELISA and CG test strip (n = 3).

Standards	Spiked level (ng/g)	CG test strip	ic-ELISA
			Mean ± SD	Recovery rate (%)
TDF	0	− − −	ND	−−
	10	±±±	8.2 ± 0.04	82.0 ± 0.04
	250	±±±	224.0 ± 0.10	89.6 ± 0.10
TDN	0	− − −	ND	−−
	10	±±±	9.06 ± 0.15	90.6 ± 0.15
	250	±±±	233.7 ± 0.12	93.5 ± 0.12
TDF and TDN (1:1)	0	− − −	ND	−−
	10	±±±	8.75 ± 0.06	87.5 ± 0.06
	250	±±±	233.0 ± 0.13	93.2 ± 0.13

−, the concentration of standard was <10 ng/g, negative sample; ±, the concentration of standard was 10–250 ng/g, weak positive sample; +, the concentration of standard was ≥250 ng/g; ND means not detection; −− means incalculable.