A Multiformat Alginate Hydrogel Platform for Persistent Luminescence-Based Biomolecule Detection in Human Serum

The integration of persistent luminescence nanoparticles (PLNPs) into hydrogels represents a promising approach for in vitro biodetection. While PLNP-containing alginate hydrogels have previously been reported for in vivo biomedical applications, the novelty of the present work lies in the development of a ZGO-based hydrogel platform for the quantitative in vitro detection of H2O2, glucose, and antigens in human serum. This approach leverages the unique properties of PLNPs, such as prolonged luminescence and high photostability, in combination with the structural flexibility and encapsulation capabilities of hydrogels. In this study, PLNP-loaded hydrogels were engineered and implemented in three different formats: either deposited in microwells, or applied as spots on nitrocellulose membranes, or used as millimetric beads. The system was designed for the sensitive and specific detection of key biomolecules, including hydrogen peroxide (H2O2), glucose, and antigens. The ZnGa2O4:Cr3+ (ZGO)-based PLNPs, whose luminescence has been shown to be amplified in the presence of H2O2, were synthesized via a hydrothermal method followed by calcination and mechanical grinding. The nanoparticles, at a concentration of 0.1 mg·mL-1 were incorporated into alginate (Alg) hydrogels at concentrations of 1%, 2%, or 3% (w/v), ensuring improved nanoparticle stability and enhanced interactions with target analytes. The study demonstrated the ability of PLNP-loaded hydrogels to detect H2O2 in human serum across all three formats. The lowest detection limit was achieved using 1% alg, reaching 1.8 μM in microwells, approximately 0.8 μM on membranes, and 1.01 μM in beads form, with a recovery rate of 99% ± 4%. Leveraging the responsiveness of hydrogel-PLNPs to H2O2, glucose detection assays were developed on membranes and in bead form using glucose oxidase as a specific added enzyme. Glucose detection limits in human serum were 0.6 μM on membranes and 0.3 μM in bead form, with detection ranges of 1-103 μM and 10-104 μM, respectively. Finally, hydrogel beads functionalized with capture antibodies were used to detect a model rabbit IgG, achieving a limit of detection of approximately 0.6 ng mL-1 and a dynamic range from 1 to 104 ng.mL-1. These three easy-to-prepare systems offer significant advantages in terms of sensitivity, signal durability, and compatibility with complex biological matrices. These results highlight the strong potential of PLNP-containing hydrogels as versatile and powerful platforms for advanced in vitro biodetection applications.