The expression of a defective gene can lead to major cell dysfunctions among which cell proliferation and
tumor formation. One promising therapeutic strategy consists in silencing the defective gene using
small interfering RNA (
siRNA). In previous publications we showed that
diamond nanocrystals (ND) of primary size 35 nm, rendered cationic by
polyethyleneimine-coating, can efficiently deliver
siRNA into cell, which further block the expression of EWS/FLI-1 oncogene in a
Ewing sarcoma disease model. However, a therapeutic application of such
nanodiamonds requires their elimination by the organism, particularly in urine, which is impossible for 35 nm particles. Here, we report that hydrogenated cationic
nanodiamonds of primary size 7 nm (ND-H) have also a high affinity for
siRNA and are capable of delivering them in cells. With
siRNA/ND-H complexes, we measured a high inhibition efficacy of EWS/FLI-1 gene expression in
Ewing sarcoma cell line. Electron microscopy investigations showed ND-H in endocytosis compartments, and especially in macropinosomes from which they can escape before
siRNA degradation occurred. In addition, the association of EWS/FLI-1 silencing by the
siRNA/ND-H complex with a
vincristine treatment yielded a potentiation of the toxic effect of this chemotherapeutic
drug. Therefore ND-H appears as a promising delivery agent in anti-tumoral gene therapy.