An effective magnetic nanocrystals (MNCs)-mediated
theranostics strategy as a combination of simultaneous diagnostics and heating treatment of
tumors by using magnetic resonance imaging (MRI) and alternating current magnetic field (ACMF) is successfully developed. In this strategy, we had firstly synthesized a well-established Mn-Zn
ferrite MNCs coated with PEG-
phospholipids (1,2-distearoyl-sn-glycero-3-
phosphoethanolamine-N-[methoxy(
polyethylene glycol copolymers,
DSPE-
PEG2000). The monodisperse PEGylated MNCs with core-shell structure (15 nm) exhibited excellent performance, such as high magnetism of 98 emu g(-1) Fe, relaxivity coefficient (r2) of 338 mm(-1) s(-1), and specific absorption rate (SAR) value of 324 W g(-1) Fe. It was proved that the obtained MNCs with an average diameter of 48.6 nm can drastically minimize the recognition and phagocytosis of macrophages, simultaneously improve their biocompatibility in vitro. These advantages endowed them with efficient passive targeting ability in vivo for prominent
tumor MRI and magnetically induced heating when exposed to ACMF, based on enhanced permeability and retention (EPR) effects. To ensure sufficient accumulation of MNCs within
tumors for targeted
hyperthermia, we described the use of MNCs with a well-tolerated intravenous single dose of 18 mg Fe/kg mouse
body weight, achieving repeatedly injection and
hyperthermia within a subcutaneous breast cell
carcinoma mouse model. With an ACMF of 12 A at 390 kHz, the
tumor surface sites could be heated to approximately 43 °C in 30 min based on MNCs-mediated
intravenous injections. The long-lasting
hyperthermia could effectively induce the apoptosis of
tumor cells, inhibit the angiogenesis of
tumor vessels, and finally suppress the
tumor growth within a certain period of time.