IgG detection in human serum employing non-functionalized chromium doped zinc gallate nanoparticles

Chromium-doped zinc gallate (ZnGa 2 O 4 :Cr 3 + ) nanoparticles (ZGO) show promising potential for antigen immunodetection using persistent luminescence, thereby reducing autofluorescence interference. Recently, we have shown that ZGO prepared by hydrothermal treatment at 120°C for 24 h can be used for in vitro biodetection in simple media such as phosphate-buffered saline. In this study, we investigated the effect of the protocol used to synthesize these ZGO nanoparticles, using a hydrothermal treatment at 220°C for different durations (6 h, 12 h, and 24 h), followed by calcination at 500°C. The nanoparticle size determined by transmission electron microscopy after grinding and centrifugation was found to be around 15 nm. The persistent luminescence signal of the ZGO nanoparticles varied with the hydrothermal synthesis conditions. Moreover, in the presence of H 2 O 2 , these nanoparticles show a signal enhancement dependent on the hydrothermal duration, with a 12 h treatment showing the highest 8-fold luminescence increase in the presence of H 2 O 2 produced by glucose oxidase mediated glucose degradation. Based on these results, these non-functionalized nanoparticles were successfully used to develop a persistent luminescence-based sandwich immunoassay for autofluorescence-free detection of antigens in undiluted human serum samples, using rabbit IgG as a model antigen. This study highlights the promising potential for biosensing applications of persistent ZGO nanophosphors for IgG detection in a complex medium (undiluted human serum), with a linear range from 1 ng mL −1 to 10 4 ng mL −1 and a limit of detection of 0.01 ng mL −1 . The present optimization of ZGO nanophosphor synthesis offers promising prospects for medical diagnostics due to their increased sensitivity and ability to eliminate autofluorescence interference, as well as their ease of use, since no functionalization of the ZGO NPs is required before use. We investigated the effect of the method used to prepare ZnGa 2 O 4 :Cr 3+ (ZGO) nanoparticles on their application in ELISA assays using signal amplification. We have shown that the conditions of the hydrothermal synthesis of the ZGO nanoparticles, at 220 °C for either 6, 12, or 24 h significantly influence their signal amplification when exposed to H₂O₂ and UV excitation. These characteristics were found to be crucial in optimizing the efficacy of these non-functionalized ZGO nanoparticles for antigen detection in undiluted human serum within an ELISA context.