Fluorescence Resonance Energy Transfer Based Highly Efficient Theranostic Nanoplatform for Two-Photon Bioimaging and Two-Photon Excited Photodynamic Therapy of Multiple Drug Resistance Bacteria

Near-infrared (NIR) light between 700 and 2500 nm, which is in the range of the first, second, and third biological windows, has the capability to penetrate biological tissues and blood, which provides a huge advantages of higher penetration depth. However, because of the lack of available biocompatible single photon probes in NIR window, there is an urgent need for new theranostic material, which could be used for two-photon bioimaging as well as for two-photon photodynamic therapy (PDT) in biological window. Driven by the need, the current manuscript reports gold nanoclusters (GNCs) attached graphene quantum dot (GQD) based twophoton excited theranostic nanoplatform with high two-photon absorption, very strong two-photon luminescence, as well as two-photon stability in NIR region. Experimental result shows strong two-photon luminescence and twophoton-induced PDT, which is based on fluorescence resonance energy transfer (FRET) mechanism, where graphene quantum dots with very high two-photon absorption act as two-photon donors and gold nanoclusters act as acceptors. Reported data indicate that O-1(2) generation efficiency enhances tremendously due to the FRET process, which increases the two-photon excited PDT efficiency for multiple drug resistance bacteria (MDRB). Reported data indicate that the nanoplatform has the capability for bright two-photon bioimaging and two-photon photodynamic therapy for MRSA and carbapenem-resistant (CRE) Escherichia coli. Reported nanoplatform is a promising candidate to serve as a contrast agent for multiphoton imaging as well as for two-photon excited PDT agent to eliminate multidrug-resistant strains.