Three-dimensional photonic crystal sensors are attractive platforms for autonomous chemical sensing and colorimetric bioassays. At present, the photonic crystal sensors with inverse opal structure were extensively studied, which swells or shrinks in response to the analytes. However, the fabrication of inverse opal sensors still remains a major challenge. Herein, we propose a simple and versatile approach to fabricate 3D opal photonic sensors. This photonic crystal is fabricated via assembly of monodispersed silica particles grafted with linear polymeric ligands (SiO@LPs). Acrylic acid (negatively charged monomer) and N-tert-butylacrylamide (hydrophobic monomer) were incorporated with N-isopropylacrylamide to achieve strong affinity between the designed polymer ligands and proteins. The proposed photonic crystal displays a maximum redshift of 23 nm in response to 2 mg/mL lysozyme, accompanied by the structure color change from blue to green. Compared to the cross-linked polymers, the linear polymer with flexible structure allows the colloidal array to recognize lysozyme with higher sensitivity (as low as 5 μg/mL) and broader linearity (from 5 to 2000 μg/mL in aqueous media). In the future, this photonic crystal sensor can be used as universal tools for the detection of a broad range of analytes. Graphical abstract Colloidal array self-assembled by polymer brush-grafted silica for proteins detection.
Self-monitoring of blood glucose is not only an effective method to treat diabetes, but also a painful invasive process to patients. To develop a noninvasive technique, we evaluated the clinical performance of a polymerized crystalline colloidal array (PCCA) sensor for glucose monitoring in urine. A twodimensional crystalline colloidal array (CCA) was assembled using polystyrene particles and further embedded into 3acrylamidophenylboronic acid functionalized hydrogel. 101 urine samples were tested, and the glucose concentrations was calculated by the particle spacing of PCCA. All the urine samples were also analyzed by automated urine analyzers. Pearson correlation and linear regression analyses showed a linear relationship between the PCCA results with a range of 0.4-53.3 mmol L À 1 and the Cobas® 8000 references (r = 0.914;[PCCA] = 0.9281 [HK] + 2.0585 mmol L À 1 ). Cohen's kappa (k) statistic with 0.65 (sig < 0.05) showed the PCCA results had moderate agreement with references. Also, Bland-Altman plot showed that AX-4030 sensor's systematic error was higher than PCCA sensor (mean = 7.4813 > 0.5271 mmol L À 1 ). The PCCA urine glucose biosensor has the advantages of fast fabrication, low cost, easy operation and high sensitivity, which provides a promising technique for noninvasive point-of-care glucose monitoring.
Based on the importance of fast and non-invasive detection technology of glucose monitoring, a glucose sensor based photonic crystal hydrogel material was prepared. The phenylboric acid was the glucose recognition molecule and the three-dimensional non-close packed array was the signal transformation structure. The experimental results show that the recognition behavior of the hydrogel is shown in the form of diffraction wavelength. As the glucose concentration increases from 0 mol/L to 50 mM, the blue shift of the diffraction wavelength occurs at 10 nm, showing a good sensing property.
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