Fluorescence nano metal organic frameworks modulated by encapsulation for construction of versatile biosensor.

The versatile fluorescence biosensors were implemented based on multipurpose nano metal organic frameworks (nMOFs) nanocomposites, which were obtained as fluorescence signal probes through encapsulation nMOFs. In this modulation process, the encapsulant bind with nMOFs through electrostatic attraction and hydrogen bond. Meanwhile, fluorescence enhancement of nMOFs were observed, accompanied by an increased in water solubility. The specific combination of target analyte triggers the release of the encapsulant and allows the target analyte to bind encapsulant to form a stable analyte-encapsulant complex. The complex binds tightly and promotes the photoinduced electron transfer from MOFs nanocomposites to the complex, thus resulting in reduce the fluorescence intensity of the MOFs nanocomposites. The results indicated that this novel system enables the specific and versatile detection of target biomolecules such as hemin and folic acid with high sensitivity and selectivity based on the choices of different encapsulant. Under optimized conditions, these biosensors show high sensitivity with a linear range from 0.16 to 12.5 μg/mL for hemin and 0.15-17.5 μmol/L for folic acid and detection limit of 47 ng/mL for hemin and 45 nmol/L folic acid. Moreover, it exhibits good performance of excellent selectivity, high stability, and acceptable fabrication reproducibility. This new multipurpose MOFs nanocomposites open avenues for combining together their properties and functionalities, and displaying novel important applications in fluorescence biosensors.