## 3 Results and Discussion
### Practical Assay Detection
#### 3.2.1 Fluorescence Detection for Albumin Quantification  
In this study, the nonimmunological method for urinary albumin determination was used to demonstrate the fluorescence detection capability of the GGP-GMR/CCD system. Figure 4: Dose response curve obtained using the (**a**) GGP-GMR/CCD system and (**b**) spectrome-193 ter. (**c**) This figure displays the correlation between the normalized intensity of the peak wave-194 length and that of the minimum intensity corresponding pixel (MICP). Figure 5: (**a**) Peak wavelength (blue), measured MICP (orange), and expected MICP (gray) based on the calibration diagram as a function of the concentration. (**b**) Correlation between the peak wavelength and the MICP. The detection mechanism is fairly simple. The albumin blue 580 (AB580) dye can bind to human albumin [8; 18] and enhance the fluorescence quantum efficiency by two orders of magnitude [19]. The composition of artificial urine used in this study, which was obtained by referring to [20], is listed in Table S1. By spiking human serum albumin (HSA; Abcam) in the artificial urine, samples with seven HSA concentrations (200, 150, 100, 50, 25, 12.5, and 6.25 mg/L) and a blank sample (only artificial urine) were prepared. Then, 4 uL of AB580 and 46 uL of albumin assay buffer (both purchased from Abcam) were added to 50 uL of each sample with HSA. The samples were wrapped in an aluminum foil for 30 min at room temperature before the measurement. A 5-mW green laser with a wavelength of 532 nm was used to excite the AB580-HSA conjugate. In addition, a bandpass filter with a wavelength of 605-625 nm was used to block the excitation illumination. The intensity measured by the GGP-GMR/CCD system and the emission spectra measured using a spectrometer at different concentrations are illustrated in Figure 6a,b, respectively. Both the peak wavelength intensity and MICP intensity increased with the HSA concentration. The peak wavelength fluctuated marginally between 608 and 612 nm. Moreover, the MICP fluctuated between the 2210 th and 2216 th pixels, which agrees well with the calibration diagram presented in Figure 1e. The MICP and peak wavelength intensities were normalized to the highest HSA concentration (200 mg/L). The dose response curves obtained from the three experimental runs are displayed in Figure 6c,d. The correlation between the spectrometer and GPP-GMR/CCD system measurements is depicted in Figure 6e, where the slope of the regression line and the coefficient of determination (R2) approach 1, which verifies that the measurement obtained with the GGP-GMR/CCD system agrees comprehensively with that measured with a commercial spectrometer. Figure 6: Intensity measured with the (**a**) GGP-GMR/CCD system and (**b**) spectrometer for different human serum albumin (has) concentrations. Normalized intensities for the (**c**) MICP and (**d**) peak wavelength as a function of the HSA concentration. (**e**) This figure depicts the correlation between the HSA measurements obtained from the spectrometer and GGP-GMR/CCD system. The limit of detection (LOD) was calculated by dividing the measurement noise with sensitivity. The noise was calculated as three times the standard deviation from all measurements. The sensitivity was obtained from the slope of the graphs presented in Figure 6c,d. The results indicate that the GGP-GMR/CCD system and spectrometer could achieve LODs of 40.99 and 17.39 mg/L, respectively, for HSA, which agreed well with the manufacturer's manual (which states that an LOD of 20 mg/L can be achieved). Within the range of 6.25-200 mg/L, both GGP-GMR/CCD system and spectrometer exhibit a fairly linear response. The marginally better LOD achieved with the spectrometer than with the proposed device is attributable to the marginally higher sensitivity (0.042 vs. 0.037) and smaller measurement noise (0.0730 vs. 0.1517) of the spectrometer. An improved optical path design can increase the light intensity on the CCD and increase shielding on the GGP-GMR/CCD setup to prevent environmental influences.