Portable SpectroChip-Based Immunoassay Platform for Rapid and Accurate Melamine Quantification in Urine Samples

Abstract

Growing concerns about the health risks of melamine adulteration in food products highlight the urgent need for reliable detection methods. However, the long-term effects of chronic low-level melamine exposure remain inadequately explored. This study introduces THE ONE InstantCare platform, a portable immunoassay analyzer integrating a SpectroChip-based spectral processing unit (SPU) with lateral flow immunoassay (LFIA) for sensitive and accurate quantification of melamine in human urine. This platform provides a cost-effective, rapid, and user-friendly point-of-care (POC) solution for melamine detection. Analytical evaluations across eight melamine concentrations (0-100 parts per billion, ppb) achieved a limit of detection (LOD) of 1.91 ppb. Validation with 24 human urine samples demonstrated strong concordance with liquid chromatography-mass spectrometry (LC-MS), yielding an intraclass correlation coefficient (ICC) of 0.9220, a Pearson correlation coefficient of 0.9389, and 95% agreement in Bland-Altman analysis. High reproducibility was observed, with an intraday coefficient of variation (CV) of 6.53% and acceptable interday CV values, while interference studies confirmed reliability in the presence of common biological substances. By delivering results in approximately 10 min, THE ONE InstantCare platform significantly reduces analysis time compared to LC-MS, which typically requires several hours. This novel platform enhances food safety surveillance and advances human health risk assessments, particularly for evaluating melamine-linked kidney damage. Its versatility and robust performance make it a promising tool for environmental monitoring and clinical diagnostics, enabling the detection of diverse biomarkers with high sensitivity and reproducibility.

Keywords: SpectroChip; lateral flow immunoassay (LFIA); liquid chromatography–mass spectrometry (LC-MS); melamine detection; point-of-care (POC); spectral processing unit (SPU).

Figure 1

Interpretation of test strip results.

Figure 2

(a) THE ONE InstantCare platform and (b) inside view of the platform.

Figure 3

(a) Optical pathway of THE ONE InstantCare platform and (b) characteristic wavelength of colloidal gold.

Figure 4

(a) Eight different concentrations of test strips, showing the absorbance curve of the C-line (b) and T-line (c) at different melamine concentrations and (d) the standard curve of melamine.

Figure 5

Comparison of melamine concentrations in urine with potential interfering substances.

Figure 6

The results of Bland–Altman analysis comparing THE ONE InstantCare platform with LC-MS. The solid line represents the mean difference, and the dotted lines represent the 95% limits of agreement.

Figure 7

Results of correlation testing between THE ONE InstantCare platform and LC-MS. The scatter points represent individual data points, and the solid line indicates the line of best fit, showing the correlation between the two methods.