Highly Sensitive Lanthanide-Doped Nanoparticles-Based Point-of-Care Diagnosis of Human Cardiac Troponin I

Figures & data

Scheme 1 Schematic illustration for configuration and principle of the cTnI determination.

Figure 1 SEM images of GdVO₄:30% Eu NPs. (A) Scale bar = 1 μm and (B) scale bar = 100 nm. TEM images of GdVO₄:30% Eu NPs with different molar of Cit^3-/Gd³⁺ (C) 4:1, (D) 3:1, (E) 2:1. Inset of b: DLS of the GdVO₄:30% Eu NPs. Inset of c: HRTEM image of GdVO₄:30% Eu NPs (scale bar = 5 nm).

Figure 2 (A) The excitation spectrum (black line) and emission spectrum (red line) of GdVO₄:30% Eu NPs. (B) The PL decay from ⁵D₀ of the NPs emission monitoring at 618 nm.

Table 1 Comparison of Various Methods for cTnI Determination

Materials	Detection Method	Linear Range	Detection Limit	Reference
15 nm AuNP-(ald) HRP-Ab and 40 nm AuNP-(ald) HRP-Ab	LFA	10°–10^4 and 10^1–10^4 pg mL^−1	5.6 pg mL^−1 and 30 pg mL^−1	[^Citation37]
Carbon nanofibers modified cellulose	LFA	0–250 ng mL^−1	1.28–1.40 ng mL^−1	[^Citation13]
ZrMOF@CdTe nanoparticles	LFA	0–1 mg L^−1	250 ng mL^−1	[^Citation38]
Alexa Fluor dye	LFA	0–100 ng mL^−1	19 pg mL^−1	[^Citation39]
Polyvinyl alcohol	LFA	10°–10^5 pg mL^−1	0.92 ng mL^−1	[^Citation40]
Streptococcal protein G modified polystyrene microspheres	LFA	0.05–32 ng mL^−1	32 pg mL^−1	[^Citation41]
Raspberry-type Eu-SiNP	LFA	0–1.16 ng mL^−1	97 pg mL^−1	[^Citation42]
Peptide-functionalized gold nanoparticles	Colorimetry	0.1–1000 ng mL^−1	0.2 ng mL^−1	[^Citation43]
Gold nanorods (AuNRs) on heparin	Colorimetry	0.5–15 ng mL^−1	0.4 ng mL^−1	[^Citation44]
PDMS-AuNPs composite film	Colorimetry	0.01–5 ng mL^−1	0.01 ng mL^−1	[^Citation45]
GdVO4:30% Eu NPs	LFA	0.02–30 ng mL^−1	17 pg mL^−1	This work

Figure 3 (A) The photos of LFA system toward different-concentration cTnI standards under UV light excitation. From left to right, the concentrations are 2.5, 0.25, 0.025 and 0 ng mL⁻¹ in order. (B) Calibration curve between the relative fluorescence intensity (T/C) versus the cTnI concentration.

Table 2 The Reproducibility Results of the Developed LFA Strip

cTnI (ng mL^−1)	Intra-Assay Precision (n=10)		Inter-Assay Precision (n=10)
	Mean ± SD (ng mL^−1)	CV (%)	Mean ± SD (ng mL^−1)	CV (%)
0.62	0.55 ± 0.08	6.86	0.52 ± 0.11	6.92
2.62	2.53 ± 0.08	4.86	2.42 ± 0.11	4.92
8.45	8.19 ± 0.41	3.67	8.21 ± 0.67	5.26
20.29	21.36 ± 1.98	6.29	22.56 ± 2.63	7.92

Table 3 The Specificity Results of the Developed LFA Strip with Interferents on cTnI Detection

cTnI (ng mL^−1)	cTnI (1.62 ng mL^−1)		cTnI (2.93 ng mL^−1)
	Value	RD (%)	Value	RD (%)
Control	1.64	1.2	3.08	5.1
Bilirubin	1.72	6.2	3.15	7.5
Sodium azide	1.52	−6.2	2.84	−3.1
Cholesterol	1.69	4.3	2.98	1.7
Hemoglobin	1.53	−5.6	2.81	−4.1
Human serum albumin	1.25	2.5	2.54	3.5
Cardiac troponin T	1.68	3.6	3.56	2.8
Immunoglobulin G	1.85	−1.5	2.37	1.9

Note: RD = (Value-Standard value)/Standard value.

Figure 4 Fluorescence intensity decay rate of the LFA strip at different repeat times. Black dots: GdVO₄ NPs probe; red dots: Polystyrene microsphere.

Figure 5 (A) The fluorescence signals of various concentrations of cTnI ranging from 0.1–30 ng mL⁻¹ spiked in Beckman cTnI quality control serum samples at different sites on the NC membrane. (B) Linear regression analysis of cTnI in Beckman quality control serum samples. (C) Correlation between the LFA kit based on GdVO₄:30% Eu NPs and commercial kit for the determination of cTnI in 86 serum samples. (D) The difference between the developed LFA kit value and the commercial kit.

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