Detection of lysozyme in body fluid based on two-dimensional colloidal crystal sensor

It is significant to detect lysozyme both in fundamental research and in clinical practice, since its concentration in body fluid is associated with many diseases. In this study, a new kind of sensor for rapid screening the lysozyme was fabricated based on the two-dimensional (2D) polystyrene colloidal crystal array together with the optimized hydrogel containing acrylamide-based functional groups. Distinct hydrogel volume shrink was observed due to the hydrogel crosslink induced by the functional ligand–protein interactions while the protein bound to the sensor. Therefore, the analyte concentration could be accessed by of the lattice spacing of the 2D colloidal crystal array, which was detected by a change in the Debye diffraction ring diameter. The lysozyme concentration could be easily monitored by measuring the diameter of the Debye diffraction ring in the pathophysiologic range. The particle spacing of 2D colloidal crystal hydrogel sensor increased to about 22 nm while lysozyme concentration increased from zero to 1.0 mg/mL, meanwhile the structural color of the sensor blue shifted from red to yellow. The detection limit was confirmed as 1.38 × 10⁻³ mg/mL. The selective response to other common proteins in body fluids was also exhibited, indicating the great selective response properties to lysozyme. In addition, the 2D colloidal crystal hydrogel sensor was reusable to detect the lysozyme solution reversibly due to its thermal sensitivity. Moreover, the determination of lysozyme in artificial tears and human urine samples by this sensor demonstrated its feasibility in potential clinical analysis diagnosis.