English

• C-reactive protein (CRP) has recently been identified as an independent risk indicator for cardiovascular disease (CVD) [1,2]. As an excellent biomarker for CVD, it is essential to detect CRP concentrations within the range of 0.1–3.0 µg/mL [3]. In the risk assessment of CVD, CRP levels in blood can be categorized into three groups: low risk (< 1.0 µg/mL), average risk (1.0–3.0 µg/mL), and high risk (> 3.0 µg/mL) [4]. However, the clinical detection threshold for CRP is set at 10 mg/L, which lacks the sensitivity required for accurate risk prediction of CVD. Furthermore, evidence suggests that CRP levels can serve as a valuable tool for evaluating the efficacy of anti-inflammatory drugs in alleviating failure in patients with CVD [2]. Nevertheless, there remains a significant gap in the availability of a versatile CRP assay that can effectively address various clinical scenarios, indicating a potential area for further research and development in diagnostic testing.

  The lateral flow immunoassay (LFIA) has great advantages in various fields, especially in disease diagnosis, because of its rapid, sensitive and portable detection ability [5-17]. However, traditional LFIA typically utilize colloidal gold nanoparticles (GNPs) with a main absorption peak around 525 nm as the signal reporter for semi-quantitative colorimetric analysis, owing to their bright red color. This approach is susceptible to background interference and is not suitable for the high-sensitivity detection of low-abundance targets in blood due to the complexities of the blood matrix.

  To enhance the sensitivity of LFIA, various nanomaterials have been employed as signal reporters, including quantum dots [18-23], carbon dots [24], dye-loaded fluorescent microspheres [7,25-29], time-resolved fluorescent microspheres [30], surface-enhanced Raman scattering nanomaterials [31,32], and upconversion nanoparticles [33-37]. Among them, fluorescent nanomaterials based on small organic molecules have attracted increasing interest in the field of LFIA due to their advantages, including ease of synthesis, controllable fluorescence properties, and environmental friendliness.

  Traditional organic dyes often exist as aggregates due to their low solubility in water, resulting in decreased fluorescence emission attributed to the aggregation-induced quenching (ACQ) effect, which is caused by π–π stacking and the formation of other non-radiative dimers [38]. In contrast, aggregate-induced emission (AIE) dyes maintain high fluorescence emission in the aggregated state by restricting intramolecular rotation and vibration [39]. For instance, Bian et al. [40] embedded AIE₄₉₀ dyes into polystyrene microspheres (PS) to prepare AIE₄₉₀-PS-labeled LFIA with ultrabright fluorescence, enabling rapid semi-quantitative detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies in serum. Additionally, Zhang et al. [28] reported the use of BAPFNPs-labeled LFIA, achieving sensitive qualitative and quantitative detection of E. coli O157:H7. In recent years, AIE dyes-doped nanoparticles (AIENPs) have been widely utilized in LFIA across various fields, including food safety, medical diagnosis and environmental detection [25,40-43]. We believe that the development of various types of fluorescent nanoparticles is essential for enhancing the application of LFIA across multiple fields. As far as we know, solid-state luminescent dyes (SLD) exhibit strong luminescence in solid states, aggregated states in poor solvents, or dispersed states in good-solvent [44-48], suggesting they also very suitable for the application of LFIA than traditional dyes.

  Herein, to fulfill the requirements of the LFIA application scenario, 2-thiomethyl-4,6-dimethylpyrimidine was selected as the π-electron-deficient central unit, while N, N-diethylaniline served as the electron-rich central unit to create a bent-shaped SLD molecule, specifically 4,4′-((1E, 1′E)-(2-(methylthio)pyrimidine-4,6-diyl)-bis(ethene-2,1-diyl))-bis(N, N-diethylaniline) (SN) [49]. The bis(styryl)benzene derivatives-based bent-shaped molecules, characterized by spontaneous electrical polarization, demonstrated robust structural stability under high temperature, light illumination, and chemical stimulation. However, their extremely poor dispersion in water significantly limited their applications across various fields. Therefore, the SN was encapsulated in PS to form a solid-state luminescent dyes-doped nanoparticles with the maximum emission at 520 nm (SLD₅₂₀NP_S). SLD₅₂₀NP_S achieved the dual objectives of uniform dispersion and strong fluorescence emission in water. And more importantly, the synthesis of SN was simplicity, efficient and eco-friendly. Ultimately, the SLD₅₂₀NP_S was conjugated with the anti-CRP antibody (mAb1) to form SLD₅₂₀NP_S-mAb1, which act as the signal reporter of LFIA (Scheme 1A). A drawing showing the principle of SLD₅₂₀NPS-mAb1-based LFIA for CRP (Scheme 1B). The SLD₅₂₀NP_S-mAb1-LFIA successfully achieved quantitative detection of CRP in serum with excellent recoveries, which further confirmed the strong application potential of SLD in LFIA.

  Scheme1

  

  Scheme1.  Illustration of SLD₅₂₀NP_S-mAb1-based LFIA for CRP. (A) The preparation process of SLD₅₂₀NP_S-mAb1. (B) A drawing showing each part of the LFIA and the principle of SLD₅₂₀NP_S-mAb1-based LFIA for CRP.

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  The SN was synthesized in solvent-free conditions via simple grinding according to reference [49]. The synthetic route of SN was described in Scheme S1 (Supporting information), and the proton nuclear magnetic resonance (¹H NMR), ¹³C NMR and high-resolution mass spectrometry (HRMS) of the related compounds were shown in Figs. S1 and S2 (Supporting information). The simple and solvent-free reaction with highly-yield was ideal for large-scale production. SN displayed extraordinary fluorescence in solid state, but it does not disperse well in aqueous solution. Consequently, in order to meet the requirement of the application scenario of LFIA, we introduced the hydrophobic dye SN into the internal hydrophobic cavity of PS with hydrophilic surface. As shown in Scheme 1A, using ammonium persulfate (APS) as the oxidizing agent, PS with a large number of carboxyl groups on the surface were synthesized by one-pot polymerization [50]. Subsequently, the SN were encapsulated to PS to form SLD₅₂₀NP_S via swelling-shrinking method due to the good-solubility of SN in tetrahydrofuran (THF). Finally, anti-CRP antibody (mAb1) was grafted to the SLD₅₂₀NP_S by the amidation coupling reaction as the highly-sensitive reporter of LFIA. As confirmed by transmission electron microscopy (TEM, Fig. 1A), the PS with highly uniform and dispersity was fabricated. After the process of swelling and reshrinking, SN were loaded into the cavity of PS to form SLD₅₂₀NP_S, whose morphology were basically consistent with PS (Fig. 1B).

  Figure 1

  

  Figure 1.  Characterization of successful preparation of SLD₅₂₀NP_S-mAb1. (A) TEM images of PS and the insert graph shows the magnified TEM image of a single PS nanoparticle. (B) TEM images of SLD₅₂₀NP_S and insert graph demonstrated the magnified TEM image of SLD₅₂₀NP_S. (C) Absorption spectra of SN in THF and SLD₅₂₀NP_S in water. (D) Absorption spectra of SLD₅₂₀NP_S (180 µg/mL) in THF. (E) Fluorescent excitation (ex) and emission (em) spectra of SN in THF and SLD₅₂₀NP_S in water. (F) Em spectra of SN in THF, SLD₅₂₀NP_S and SLD₅₂₀NP_S-mAb1 in water. (G) QY of SLD₅₂₀NP_S and SLD₅₂₀NP_S-mAb1 in water. (H) DLS of PS, SLD₅₂₀NP_S and SLD₅₂₀NP_S-mAb1 in water. (I) Zeta potential of PS, SLD₅₂₀NP_S and SLD₅₂₀NP_S-mAb1 in water. Data are presented as mean ± standard deviation (SD) (n = 3).

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  The spectrum of SN and SLD₅₂₀NP_S were measured by the ultraviolet–visible spectroscopy (UV–vis) and fluorescence spectrometers. Both the maximum absorption of SN and SLD₅₂₀NP_S were at 445 nm (Fig. 1C). The loading capacity of SN in PS was obtained by standard curve method, which was plotted by the concentration of SN in THF as the x and the absorbance at 445 nm as y (Fig. S3 in Supporting information). According to the liner regression equation: y = 0.112x – 0.041 (R² = 0.999), the mass ratio (M_SN/M_PS) between the SN and PS was calculated to be 6.2% (Fig. 1D). The maximum excitation peak of SN was at 445 nm, while that of SLD₅₂₀NP_S was at 440 nm. The maximum emission peak of SN at 525 nm, while that of SLD₅₂₀NP_S was at 520 nm. The excitation spectrum of SLD₅₂₀NP_S was basically the same as that of SN, while the emission spectrum has an additional emission peak at 630 nm relative to SN (Fig. 1E). The apparent difference in emission spectra may be due to the formation of dimers due to changes in the surrounding environment. As shown in the Fig. S4 (Supporting information), the dissolution of SLD₅₂₀NP_S in DMSO resulted in the disappearance of the emission peak at 630 nm, further confirming the formation of dimers.

  To verify the successful modification of mAb1 on the SLD₅₂₀NP_S, the fluorescence spectra, fluorescence quantum yield (QY), hydrodynamic diameter (DLS) and zeta potential of PS, SLD₅₂₀NP_S and SLD₅₂₀NP_S-mAb1 were characterized. After modification of mAb1 on the SLD₅₂₀NP_S, the fluorescence emission spectrum of SLD₅₂₀NP_S-mAb1 was basically unchanged with SLD₅₂₀NP_S (Fig. 1F). The QY was measured by absolute method via the integrating sphere. The QY of SLD₅₂₀NP_S was 49% while the QY of SLD₅₂₀NP_S-mAb1 was 46.68% (Fig. 1G), indicating that the antibody modification had no effect on the fluorescence properties. The DLS increased from 310 nm to 390 nm after SN were loaded into PS. the DLS of SLD₅₂₀NP_S-mAb1 increased to 450 nm after modification with the mAb1 (Fig. 1H). The zeta potentials of PS, SLD₅₂₀NP_S and SLD₅₂₀NP_S-mAb1 were −44.65, −40.02 and −30.00 eV, respectively (Fig. 1I). The above data for SLD₅₂₀NP_S changed significantly following the attachment of the mAb1, thereby confirming the successful binding of mAb1.

  As the signal reporter of LFIA, the photostability of SLD₅₂₀NP_S is crucial. As shown in Fig. 2A, the fluorescence intensity at 520 nm of SLD₅₂₀NP_S remained 85% relative to the original state under the irradiation of 405 nm light for 2 h, indicating the excellent photostability of SLD₅₂₀NP_S. Moreover, SLD₅₂₀NP_S also exhibited excellent pH stability. As shown in Fig. 2B, the fluorescence intensity at 520 nm of SLD₅₂₀NP_S was steady in the pH range from 5 to 9. When incubated at high temperature for 2 h, the fluorescence intensity of SLD₅₂₀NP_S changed little, indicating its heat resistance (Fig. 2C).

  Figure 2

  

  Figure 2.  Fluorescence stability test of SLD₅₂₀NP_S. Fluorescence evolution of SLD₅₂₀NP_S (A) under continuous 405 nm light illumination, (B) in different pH and (C) in 60 ℃ water bath. Data are presented as mean ± SD (n = 3).

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  The above excellent performance of SLD₅₂₀NP_S proved that SN combined with PS was very suitable for application in LFIA. To verify this point, anti-CRP antibody (mAb2) and goat anti-mouse IgG were coated on the NC membrane as test line (TL) and control line (CL), respectively. SLD₅₂₀NP_S-mAb1 were evenly sprayed on the conjugate pad through the gold spray instrument. The principle of SLD₅₂₀NP_S-mAb1 detecting CRP could be revealed that sandwich-like immunological structure were formed by mAb2 on the TL binding with the CRP in the SLD₅₂₀NP_S-mAb1 (Scheme 1B). With the increased concentration of CRP, the fluorescence intensity of TL gradually increased, while the fluorescence intensity of CL gradually decreased. Moreover, the CRP level was reflected by the fluorescence intensity of TL, which can be accurately and quantitatively determined with a customized strip analyzer.

  In order to achieve highly-sensitive, fast and quantitative detection of the CRP, many important factors of LFIA need to be optimized. By observing the F_T, the F_C and the value of T/C, we explored the optimal parameters, including the coupling amount of mAb1, the coating amount of mAb2, the amount of probe sprayed on the conjugate pad, and the immunoreaction time. We found that the amount of mAb2 played a significant role in the complete emergence image of the CL. First, the concentration of goat anti-mouse IgG on the CL was fixed at 1 mg/mL. When the amount of mAb2 exceeded 1 mg/mL, a virtual image appeared in the upper middle of CL due to the most of the CRP was captured by mAb2 on the TL. The limited amount of CRP was not sufficient to present a complete CL picture. Subsequently, the concentration of 0.2, 0.5, 0.7, 1 and 1.3 mg/mL have also been screened. Combining the F_C, F_T and T/C value, we found that the concentration of 1 mg/mL was the most suitable (Fig. 3A). With the increase of the SLD₅₂₀NPs-mAb1 concentration sprayed on the conjugate pad, the T/C value gradually increased. Although 10 µL/cm of SLD₅₂₀NPs-mAb1 demonstrated the best performance, the release of SLD₅₂₀NPs-mAb1 from the conjugate pad to the NC membrane was incomplete. And the intensity of CL decreased. Therefore, 8 µL/cm was selected for subsequent tests (Fig. 3B). It is noteworthy that during the testing period, we observed that the T-line appeared superior to the C-line when the spray velocity reached 10 µL/cm, resulting in a downward trend in the T/C ratio with an increase in immunoreaction time. As the coupling ratio of mAb1 in the SLD₅₂₀NPs-mAb1 increases from 50:1 to 150:1, the signal on the TL was gradually enhanced. But the signal on the TL does not increase significantly above 130:1, so the optimal ratio of antibody was 130:1 (Fig. 3C). As shown in the Fig. 3D, with the increase of immunoreaction time, the T/C value gradually increased. And immunoreaction time reached the plateau after 15 min. In the subsequent experimental, 15 min was selected as the optimal reaction time. As shown in Fig. S5 (Supporting information), SLD₅₂₀NPs-mAb1-based LFIA can still maintain the ability of CRP detection within two weeks at 55 ℃, indicating that it can be stored longer at room temperature.

  Figure 3

  

  Figure 3.  Optimization of various parameters. Variation of F_C, F_T and T/C value (A) with the amount of anti-CRP antibody (mAb2), (B) the amount of SLD₅₂₀NPs-mAb1 and (C) the coupling ratio of SLD₅₂₀NPs to mAb1. (D) Variation of T/C value with the assay time. The concentration of CRP is 100 ng/mL. Data are presented as mean ± SD (n = 3).

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  To verify the excellent performance of SLD₅₂₀NPs-based LFIA, a series concentration of CRP (from 0 to 100 ng/L) in phosphate buffer saline (PBS, 10 mmol/L, pH 7.4, 0.1% Tween-20) were prepared. Fig. 4A demonstrated that SLD₅₂₀NPs-mAb1 not only were captured by the mAb1 on the TL and the goat anti-mouse IgG on the CL, but also could be quantitative captured. In addition, as shown in Fig. 4B, the T/C values showed a satisfactory linear relationship with the CRP concentration in the range of 0.5–100 ng/mL (y = 0.121 + 0.009x, R² = 0.958). The limits of detection (LOD) were 0.78 ng/mL and the calculation was based on the mean signal and 3-fold standard deviation (SD) of a negative sample with a detectable concentration. Furthermore, the visible LOD was 1 ng/mL with a handheld 405 nm lamp. To validate the improved performance of the current LFIA, the performance of the commercial LFIA to SLD₅₂₀NPs-mAb1-based LFIA have been compared. As shown in the Fig. S6 (Supporting information), the visible LOD of the commercially available colloidal gold based LFIA was 10 ng/mL, while the visible LOD of the SLD₅₂₀NPs-mAb1-based LFIA designed by us was 1 ng/mL. The SLD₅₂₀NPs-mAb1-based LFIA demonstrates a tenfold increase in visible LOD compared to commercially available colloidal gold strips. Compared with other methods of detecting CRP, the SLD₅₂₀NPs-mAb1-based LFIA also showed excellent detection performance (Table S1 in Supporting information).

  Figure 4

  

  Figure 4.  Performance evaluation of SLD₅₂₀NPs-mAb1-based LFIA. (A) Fluorescence images of SLD₅₂₀NPs-mAb1-based LFIA at different concentrations of CRP under a 405 nm lamp. (B) The concentration dependence of the T/C value in the range of 0–100 ng/mL. (C) The specificity of SLD₅₂₀NPs-mAb1-based LFIA toward CRP. (D) The anti-interference property of SLD₅₂₀NPs-mAb1-based LFIA toward CRP in the present of other proteins. Data are presented as mean ± SD (n = 3).

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  To evaluate the specificity of the SLD₅₂₀NPs-mAb1-based LFIA, several types of proteins including interleukin-6 (IL-6), SARS-Cov-2 nucleocapsid protein (NP), cardiac troponin I (cTnI), and procalcitonin (PCT) at a concentration of 1000 ng/mL in PBS (10 mmol/L, pH 7.4, 0.1% Tween-20) were employed as the negative controls. Moreover, the concentration of the positive sample with CRP was at 100 ng/mL. As shown in Figs. 4C and D, even when the concentration of interfering proteins was 100 times higher than that of the CRP sample, the F_T of the CRP sample was still significantly higher than that of the negative samples. Furthermore, the T/C value of the CRP sample showed no significant change in the presence or absence of the negative samples, suggesting the high sensitivity and strong anti-interference properties of the SLD₅₂₀NPs-mAb1. The corresponding fluorescence images of SLD₅₂₀NPs-mAb1-based LFIA under a 405 nm lamp are shown in Figs. S7 and S8 (Supporting information). Given that the serum contains various components, including human serum protein, glucose, IgG, and amino acids, we also evaluated whether these substances interfered with the detection process of the SLD₅₂₀NPs-mAb1-LFIA. As illustrated in Fig. S9 (Supporting information), the SLD₅₂₀NPs-mAb1-LFIA demonstrated high sensitivity and robust anti-interference properties.

  The excellent performance of LFIA meets the requirements of biomarker detection in PBS containing 10% serum. And to evaluate the accuracy and precision of the SLD₅₂₀NPs-mAb1-based LFIA, various concentrations of CRP including 10, 25, and 75 ng/mL were added into the solution with a base value of 10 ng/mL. As shown in Table 1, the average recoveries for CRP were 102.50%, 94.45%, and 94.69%, and the coefficients of variation (CV) were 7.57%, 3.33%, and 4.91%, respectively. The results indicated that the SLD₅₂₀NPs-mAb1-based LFIA have a good quantitative ability and an excellent accuracy for CRP in serum with a portable fluorescent reader. To further verify the accuracy of SLD₅₂₀NPs-mAb1-based LFIA, the correlation between the detection results of the SLD₅₂₀NPs-mAb1-based LFIA and the enzyme-linked immunosorbent assay (ELISA) method involved in various concentrations of CRP including 5, 10, 20, 40, 60, 80 and 100 ng/mL have been analyzed. As illustrated in Fig. S10 (Supporting information), the results obtained from SLD₅₂₀NPs-mAb1-based LFIA align closely with those from the ELISA, demonstrating a linear correlation coefficient of 0.97, reflecting a significant level of reliability.

  Table 1

  

  Table 1.  Spike-and-recovery tests of SLD₅₂₀NPs-mAb1-based LFIA in detecting CRP-spiked serum with the baseline concentration of 10 ng/mL (n = 3).

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  Sample	Added (ng/mL)	Mean	SD	Found (ng/mL)	Recovery (%)	CV (%)
  1	10	0.303	0.023	20.25	102.50	7.57
  2	25	0.424	0.014	33.61	94.45	3.33
  3	75	0.850	0.042	81.01	94.69	4.91

  In summary, to broaden the diversity of fluorescent nanoparticles and thereby improve the application of LFIA across various fields, we have successfully developed solid-state luminescent dye-doped nanoparticles for LFIA applications. The innovative LFIA system, which is based on SLD₅₂₀NPs coupled with the monoclonal antibody, showcased a satisfactory linear relationship with the concentrations of CRP that span from 0.5 ng/mL to 100 ng/mL, with LOD of 0.78 ng/mL. Notably, the system exhibited excellent recoveries in serum, ranging from 94.45% to 102.5%. indicating its accuracy and reliability in real-world biological contexts. Collectively, the exceptional performance demonstrated by the SLD₅₂₀NPs-mAb1-based LFIA underscores the substantial promise that solid-state luminescent dyes hold for further advancements and applications within the sector of LFIA.

  Declaration of competing interest

  The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

  CRediT authorship contribution statement

  Panpan Sun: Writing – original draft, Visualization, Validation, Project administration, Methodology, Investigation, Funding acquisition, Formal analysis, Data curation, Conceptualization. Qian Li: Validation, Software. Ningshuang Gao: Validation. Mingyue Luo: Methodology. Wenzhuo Chang: Investigation. Baodui Wang: Supervision. Xiaoquan Lu: Validation, Supervision. Zhonghua Xue: Writing – review & editing, Funding acquisition.

  Acknowledgments

  This work was supported by the National Natural Science Foundation of China (Nos. 22064014, 21765013), the Science and Technology Development Plan Project of Lanzhou (No. 2021-1-146), the Science and Technology Project of Gansu Province (Nos. 21YF5FA071, 21JR7RA538), the Industrial Support Programme for Higher Education Institutions Project (Nos. 2023CYZC-69, 2024CYCZ-05), and the 2023 Gansu Provincial Key Talent Project (No. 2023RCXM26), and a Gansu province postdoctoral grant (No. 00247).

  Supplementary materials

  Supplementary material associated with this article can be found, in the online version, at doi:10.1016/j.cclet.2024.110801.

  
  
• 1. [1]

     S.W. Oh, J.D. Moon, S.Y. Park, et al., Clin. Chim. Acta 356 (2005) 172–177. doi: 10.1016/j.cccn.2005.01.026

  2. [2]

     P.M. Burger, S. Koudstaal, A. Mosterd, et al., J. Am. Coll. Cardiol. 82 (2023) 414–426. doi: 10.1016/j.jacc.2023.05.035

  3. [3]

     P.M. Ridker, Circ. Res. 118 (2016) 145–156. doi: 10.1161/CIRCRESAHA.115.306656

  4. [4]

     T.A. Pearson, G.A. Mensah, R.W. Alexander, et al., Circulation 107 (2003) 499–511. doi: 10.1161/01.CIR.0000052939.59093.45

  5. [5]

     K. Wang, X. Liu, X. Liang, et al., Anal. Chem. 96 (2024) 3208–3216.

  6. [6]

     L. Ye, X. Xu, A. Qu, et al., Nano Res. 17 (2024) 5452–5460. doi: 10.1007/s12274-024-6471-2

  7. [7]

     L. Bian, Q. Fu, Z. Gan, et al., Adv. Sci. 11 (2024) 2305774. doi: 10.1002/advs.202305774

  8. [8]

     J. Guo, Y. Zhou, J. Cheng, et al., Anal. Chem. 96 (2024) 4891–4900. doi: 10.1021/acs.analchem.3c05448

  9. [9]

     D. Wang, S. He, X. Wang, et al., Nat. Biomed. Eng. 4 (2020) 1150–1158. doi: 10.1038/s41551-020-00655-z

  10. [10]

      B.S. Miller, L. Bezinge, H.D. Gliddon, et al., Nature 587 (2020) 588–593. doi: 10.1038/s41586-020-2917-1

  11. [11]

      J.H. Soh, H.M. Chan, J.Y. Ying, Nano Today 30 (2020) 100831. doi: 10.1016/j.nantod.2019.100831

  12. [12]

      Y. Liu, L. Zhan, Z. Qin, et al., ACS Nano 15 (2021) 3593–3611. doi: 10.1021/acsnano.0c10035

  13. [13]

      Z. Wang, R. Zou, J. Yi, et al., Small 20 (2024) 2310869. doi: 10.1002/smll.202310869

  14. [14]

      G. Guo, T. Zhao, R. Sun, et al., Chin. Chem. Lett. 35 (2024) 109198. doi: 10.1016/j.cclet.2023.109198

  15. [15]

      Y. Zhang, C.B. Ma, M. Yang, et al., Sens. Actuators B: Chem. 288 (2019) 163–170. doi: 10.1007/978-3-319-78963-7_22

  16. [16]

      M. Yang, Y. Tang, L. Qi, et al., Anal. Chem. 93 (2021) 11956–11964. doi: 10.1021/acs.analchem.1c01829

  17. [17]

      Y. Tang, L. Qi, Y. Liu, et al., Angew. Chem. Int. Ed. 61 (2022) e202115907. doi: 10.1002/anie.202115907

  18. [18]

      J. Liu, L. Lin, P. Yao, et al., Anal. Chem. 94 (2022) 8818–8826. doi: 10.1021/acs.analchem.2c02028

  19. [19]

      W. Wang, X. Yang, Z. Rong, et al., Nano Res. 16 (2023) 3063–3073. doi: 10.1007/s12274-022-5043-6

  20. [20]

      C. Wang, R. Xiao, S. Wang, et al., Biosens. Bioelectron. 146 (2019) 111754. doi: 10.1016/j.bios.2019.111754

  21. [21]

      F. Gao, C. Liu, Y. Yao, et al., Biosens. Bioelectron. 199 (2022) 113892. doi: 10.1016/j.bios.2021.113892

  22. [22]

      J. Wang, C. Jiang, J. Jin, et al., Angew. Chem. Int. Ed. 60 (2021) 13042–13049. doi: 10.1002/anie.202103458

  23. [23]

      J. Liu, H. Meng, L. Zhang, et al., Chin. Chem. Lett. 32 (2021) 3421–3425. doi: 10.1016/j.cclet.2021.05.019

  24. [24]

      D. Qin, X. Jiang, G. Mo, et al., ACS Sens. 4 (2019) 504–512. doi: 10.1021/acssensors.8b01607

  25. [25]

      Y. Wang, G. Zhang, X. Xiao, et al., Anal. Chem. 95 (2023) 17860–17867. doi: 10.1021/acs.analchem.3c03986

  26. [26]

      L. Fan, W. Yan, Q. Chen, et al., Anal. Chem. 96 (2024) 401–408. doi: 10.1021/acs.analchem.3c04441

  27. [27]

      R. Chen, C. Ren, M. Liu, et al., ACS Nano 15 (2021) 8996–9004. doi: 10.1021/acsnano.1c01932

  28. [28]

      G. Zhang, Z. Huang, L. Hu, et al., ACS Nano 17 (2023) 23723–23731. doi: 10.1021/acsnano.3c07509

  29. [29]

      J. Shu, Y. Li, H. Cai, et al., Aggregate 5 (2024) e551. doi: 10.1002/agt2.551

  30. [30]

      L.M. Hu, K. Luo, J. Xia, et al., Biosens. Bioelectron. 91 (2017) 95–103. doi: 10.1016/j.bios.2016.12.030

  31. [31]

      M. Wang, J. Feng, J. Ding, et al., Chem. Eng. J. 487 (2024) 150666. doi: 10.1016/j.cej.2024.150666

  32. [32]

      Y. Pang, Q. Li, C. Wang, et al., Chem. Eng. J. 429 (2022) 132109. doi: 10.1016/j.cej.2021.132109

  33. [33]

      M. You, M. Lin, Y. Gong, et al., ACS Nano 11 (2017) 6261–6270. doi: 10.1021/acsnano.7b02466

  34. [34]

      W. He, M. Wang, P. Cheng, et al., Trends Anal. Chem. 173 (2024) 117641. doi: 10.1016/j.trac.2024.117641

  35. [35]

      J. Kim, J.H. Kwon, J. Jang, et al., Biosens. Bioelectron. 112 (2018) 209–215. doi: 10.1016/j.bios.2018.04.047

  36. [36]

      T. Ji, X. Xu, X. Wang, et al., ACS Nano 14 (2020) 16864–16874. doi: 10.1021/acsnano.0c05700

  37. [37]

      C. Chen, S. Hu, L. Tian, et al., Biosens. Bioelectron. 252 (2024) 116135. doi: 10.1016/j.bios.2024.116135

  38. [38]

      X. Hu, P. Zhang, D. Wang, et al., Biosens. Bioelectron. 182 (2021) 113188. doi: 10.1016/j.bios.2021.113188

  39. [39]

      X. He, Y. Luo, Y. Li, et al., Aggregate 5 (2024) e396. doi: 10.1002/agt2.396

  40. [40]

      L. Bian, Z. Li, A. He, et al., Biomaterials 288 (2022) 121694. doi: 10.1016/j.biomaterials.2022.121694

  41. [41]

      X. Liu, F. Xia, S. Zhang, et al., Food Chem. 402 (2023) 134235. doi: 10.1016/j.foodchem.2022.134235

  42. [42]

      G. Zhang, T. Liu, H. Cai, et al., ACS Nano 18 (2024) 2346–2354. doi: 10.1021/acsnano.3c10427

  43. [43]

      L. Hao, W. Yang, Y. Xu, et al., Biosens. Bioelectron. 212 (2022) 114411. doi: 10.1016/j.bios.2022.114411

  44. [44]

      M. Zheng, H. Jia, B. Zhao, et al., Small 19 (2023) 2206715. doi: 10.1002/smll.202206715

  45. [45]

      X. Hou, C. Ke, C.J. Bruns, et al., Nat. Commun. 6 (2015) 6884. doi: 10.1038/ncomms7884

  46. [46]

      X. Wang, B. Xu, W. Tian, Acc. Mater. Res. 4 (2023) 311–322. doi: 10.1021/accountsmr.2c00158

  47. [47]

      J. Ochi, K. Tanaka, Y. Chujo, Angew. Chem. Int. Ed. 59 (2020) 9841–9855. doi: 10.1002/anie.201916666

  48. [48]

      G. Zhu, Z. Liu, Q. Qi, et al., Angew. Chem. Int. Ed. 63 (2024) e202406417. doi: 10.1002/anie.202406417

  49. [49]

      L. Li, Y.P. Tian, J.X. Yang, et al., Chem. Asian J. 4 (2009) 668–680. doi: 10.1002/asia.200800402

  50. [50]

      S.E. Seo, E. Ryu, J. Kim, et al., Sens. Actuators B: Chem. 381 (2023) 133364. doi: 10.1016/j.snb.2023.133364

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  Scheme1  Illustration of SLD₅₂₀NP_S-mAb1-based LFIA for CRP. (A) The preparation process of SLD₅₂₀NP_S-mAb1. (B) A drawing showing each part of the LFIA and the principle of SLD₅₂₀NP_S-mAb1-based LFIA for CRP.

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  Figure 1  Characterization of successful preparation of SLD₅₂₀NP_S-mAb1. (A) TEM images of PS and the insert graph shows the magnified TEM image of a single PS nanoparticle. (B) TEM images of SLD₅₂₀NP_S and insert graph demonstrated the magnified TEM image of SLD₅₂₀NP_S. (C) Absorption spectra of SN in THF and SLD₅₂₀NP_S in water. (D) Absorption spectra of SLD₅₂₀NP_S (180 µg/mL) in THF. (E) Fluorescent excitation (ex) and emission (em) spectra of SN in THF and SLD₅₂₀NP_S in water. (F) Em spectra of SN in THF, SLD₅₂₀NP_S and SLD₅₂₀NP_S-mAb1 in water. (G) QY of SLD₅₂₀NP_S and SLD₅₂₀NP_S-mAb1 in water. (H) DLS of PS, SLD₅₂₀NP_S and SLD₅₂₀NP_S-mAb1 in water. (I) Zeta potential of PS, SLD₅₂₀NP_S and SLD₅₂₀NP_S-mAb1 in water. Data are presented as mean ± standard deviation (SD) (n = 3).

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  Figure 2  Fluorescence stability test of SLD₅₂₀NP_S. Fluorescence evolution of SLD₅₂₀NP_S (A) under continuous 405 nm light illumination, (B) in different pH and (C) in 60 ℃ water bath. Data are presented as mean ± SD (n = 3).

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  Figure 3  Optimization of various parameters. Variation of F_C, F_T and T/C value (A) with the amount of anti-CRP antibody (mAb2), (B) the amount of SLD₅₂₀NPs-mAb1 and (C) the coupling ratio of SLD₅₂₀NPs to mAb1. (D) Variation of T/C value with the assay time. The concentration of CRP is 100 ng/mL. Data are presented as mean ± SD (n = 3).

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  Figure 4  Performance evaluation of SLD₅₂₀NPs-mAb1-based LFIA. (A) Fluorescence images of SLD₅₂₀NPs-mAb1-based LFIA at different concentrations of CRP under a 405 nm lamp. (B) The concentration dependence of the T/C value in the range of 0–100 ng/mL. (C) The specificity of SLD₅₂₀NPs-mAb1-based LFIA toward CRP. (D) The anti-interference property of SLD₅₂₀NPs-mAb1-based LFIA toward CRP in the present of other proteins. Data are presented as mean ± SD (n = 3).

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  Table 1.  Spike-and-recovery tests of SLD₅₂₀NPs-mAb1-based LFIA in detecting CRP-spiked serum with the baseline concentration of 10 ng/mL (n = 3).

  Sample	Added (ng/mL)	Mean	SD	Found (ng/mL)	Recovery (%)	CV (%)
  1	10	0.303	0.023	20.25	102.50	7.57
  2	25	0.424	0.014	33.61	94.45	3.33
  3	75	0.850	0.042	81.01	94.69	4.91

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