RETRACTED: Light-triggered nitric oxide release and targeted fluorescence imaging in tumor cells developed from folic acid-graft-carboxymethyl chitosan nanospheres (Retracted Article)

Folic acid (FA) grafted carboxymethyl chitosan (CMC) nanospheres (CMC-FA) were prepared via a facile carboxy-amine coupling reaction, and were further developed toward light-triggered nitric oxide (NO) release and targeted fluorescence imaging in cells. Under electrostatic adsorption interactions, photosensitive NO donors (Fe4S3(NO)(7)(-), RBS) and polyethleneimine-stabilized carbon quantum dots (CQD) were respectively loaded into CMC-FA to form CMC-FA-RBS and CMC-FA-CQD hybrid nanospheres. These as-prepared nanospheres exhibited high colloidal stabilities in phosphate buffered saline (pH 4.9-9.2) and bovine serum albumin (0-48 h incubation), and produced negligible cytotoxicity. NO was released from CMC-FA-RBS nanospheres upon light excitation (365 nm), demonstrating a smart "on-off" switch for controllable NO release. Targeted fluorescence imaging of CMC-FA-CQD nanospheres was investigated and confirmed in folate receptor (FR) over-expressed tumor (HeLa) cells, compared to other cells without or with relatively low expression of FR.