Chelator-Free Conjugation of 99mTc and Gd3+ to PEGylated Nanographene Oxide for Dual-Modality SPECT/MR Imaging of Lymph Nodes

PEGylated ultrasmall nanographene oxide (usNGO-PEG) has exhibited a great potential in nanotheranostics due to its newly discovered physicochemical properties derived from the rich functional groups and bonds. Herein, we developed a general, simple, and kitlike preparation approach for 99mTc- and Gd-anchored NGO-PEG using a chelator-free strategy. In this strategy, [99mTcI(CO)3(OH2)3]+ (abbreviated to 99mTcI) and GdCl3 were mixed with usNGO-PEG to yield 99mTc- and Gd-usNGO-PEG via the synergistic coordination of N and O atoms from NGO and PEG with 99mTcI and Gd3+ without additional exogenous chelators. Under optimized conditions, the nanoprobes 99mTc- and Gd-usNGO-PEG were reliably prepared with high yields and good stability. Serial comparative experiments of the labeling yield, the measurements of −NH2 density and ζ-potentials, and various characterizations including energy-dispersive X-ray analysis spectroscopy, X-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy demonstrated ...