Retracted Article: Light-triggered nitric oxide release and targeted fluorescence imaging in tumor cells developed from folic acid-graft-carboxymethyl chitosan nanospheres

Abstract

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.