Hydrogel-Film-Fabricated Fluorescent Biosensors with Aggregation-Induced Emission for Albumin Detection through the Real-Time Modulation of a Vortex Fluidic Device

Abstract

Hydrogels have various promising prospects as a successful platform for detecting biomarkers, and human serum albumin (HSA) is an important biomarker in the diagnosis of kidney diseases. However, the difficult-to-control passive diffusion kinetics of hydrogels is a major factor affecting detection performance. This study focuses on using hydrogels embedded with aggregation-induced emission (AIE) fluorescent probe TC426 to detect HSA in real time. The vortex fluidic device (VFD) technology is used as a rotation strategy to control the reaction kinetics and micromixing during measurement. The results show that the introduction of VFD could significantly accelerate its fluorescence response and effectively improve the diffusion coefficient, while VFD processing could regulate passive diffusion into active diffusion, offering a new method for future sensing research.

Keywords: aggregation-induced emission; fluorescence biosensor; human serum albumin; hydrogel films; vortex fluidic device.

Figure 1

(A) Portable VFD used in this study; (B) interaction process between the solution and hydrogel film adhered to the tube wall; (C) efficient spinning top flow-mediated transfer of reactants into and out of the hydrogel matrix.

Figure 2

Characterisation of hydrogel films using TC426. (A) Schematic of the working mechanism of TC426 in HSA detection [12]; (B) FL spectra of TC426 in two matrices: AAm−Alg and carrageenan under different conditions; (C) effect of TC426-based hydrogel films with and without VFD modulation; (D) standard curve of TC426-embedded hydrogel films under different HSA concentrations ranging from 0 to 1000 mg/L with/without VFD processing. TC426 = 10 μM, λ_ex = 480 nm, I₀ = intensity of HSA = 0 mg/L; VFD was used for 2 and 4 min in AAm–Alg + TC426 and Carrageenan + TC426, respectively.

Figure 3

SEM images captured under 50 μm magnification from the surface of an (A) AAm–Alg + TC426 hydrogel film, (C) carrageenan + TC426 hydrogel film. SEM images captured under magnification 20 and 40 μm from the cross section of (B) AAm–Alg + TC426 hydrogel film, and (D) carrageenan + TC426 hydrogel film.

Figure 4

Optical microscopy images for the reflection mode in the darkfield. AAm–Alg hydrogel film + TC426: (A) without VFD; (B) with VFD, 100 μm; carrageenan hydrogel film + TC426: (C) without VFD; (D) with VFD, 100 μm; HSA = 2000 mg/L and TC426 = 10 μM, VFD was used for 2 and 4 min in AAm–Alg + TC426 and carrageenan + TC426, respectively.

Figure 5

Potential mechanism of TC426-embedded AAm–Alg and carrageenan hydrogel film.

Figure 6

Correlations of HSA concentration and optical density in the range from 0 to 1000 mg/L under white LEDs. The black line represents the established master curve, R² = 0.97; the red dot represents the validated sample. TC426 = 10 μM.