Design of graphene quantum dots decorated MnO2 nanosheet based fluorescence turn “On-Off-On” nanoprobe for highly sensitive detection of lactoferrin

• Designed graphene quantum dots (GQDs) and MnO 2 -nanosheet-based fluorescent nanoprobe (GQDs@MnO 2 -NS). • Fluorescent GQDs@MnO 2 -NS demonstrates high sensitivity for the detection of lactoferrin. • Redox reaction between lactoferrin and MnO 2 -NS resulted in the reappearance of fluorescence emission of GQDs. • The envisioned fluorescent biosensor will present a novel complement for the diagnosis of periodontal disease. Lactoferrin estimation is increasingly acquiring prominence as a novel biomarker for the diagnosis of periodontal disease. To date, diverse lactoferrin detection methods which include electrochemical, surface-enhanced Raman scattering, colorimetric, and others have been extensively portrayed. Unfortunately, these systems have significant shortcomings including low sensitivity, selectivity, high cost, arduous and time-consuming technique, and so forth. Recently, the fluorescence-based method shows remarkable uniqueness that overcomes the demerits of traditionally reported techniques. Therefore, graphene quantum dots (GQDs) and manganese dioxide nanosheets (MnO 2 -NS) based simplistic, highly sensitive, and selective fluorescent turn ‘Off-On’ mediated GQDs@MnO 2 -NS nanoprobe was designed. Herein, MnO 2 -NS addition demonstrated the quenching of GQDs containing fluorescence through inner filter effects (IFE) and strong interaction between GQDs and MnO 2 -NS. The lactoferrin addition destroyed the MnO 2 -NS and fluorescence emission of GQDs reappeared which may be because of redox reaction between lactoferrin and prepared MnO 2 -NS. Herein, nanoprobe offers a wide concentration range and low limit of detection of 5 to 1600 ng/mL and 1.69 ng/mL, respectively. As fabricated GQDs@MnO 2 -NS nanoprobe sensor demonstrated high selectivity, good stability, and reproducibility towards lactoferrin that assuring applicability of biosensor. Therefore, the GQDs@MnO 2 -NS nanoprobe will offer a simplistic sensor with adequate sensitivity to achieve highly responsive and selective detection of lactoferrin.