Study Of AS1411 Aptamer-Functionalized Fe₃O₄ Nanoparticles For Targeted Hyperthermia

Magnetic nanoparticles（MNPs）have found numerous applications in biomedical area,such as targeted drug delivery,magnetic resonance imaging（MRI）,hyperthermia and magnetic separation due to their unique physicochemical properties and abilities to function at cellular and molecular levels.Their excellent properties mainly lie in favorable biocompatibility,relatively low toxicity,low sensibility to oxidation and stable magnetic responsiveness and high magnetically induced heating effects.Generally,thermal decomposition technique is an effective way in preparing high-quality Fe₃O₄ nanoparticles（Fe₃O₄ NPs）,where their shape,size,composition,surface states and some other important features can be synthetically controlled.Based on previous synthesis experience,thermal decomposition technique was applied to fabricate Fe₃O₄ NPs with desirable properties.In detail,Fe（acac）3 was used as precursor,oleic acid and oleyl amine as surfactant in dibenzyl ether solvents with high boiling point,then biocompatible DSPE-PEG2000-COOH was used as modification agent via hydrophobic interaction,where Fe₃O₄@PEG NPs with long circulation ability were synthesised.Fe₃O₄@Apt NPs were obtained by conjugating the PEGylated Fe₃O₄ NPs with 5’-NH2 AS 1411 aptamer（Apt）via the classic EDC/NHS technique,which can be used to target nucleolin-overexpressing cancerous cells.During blood circulation,Fe₃O₄@PEG NPs can be passively targeted to cancerous cells via enhanced permeability and retention（ERP）effect,while Fe₃O₄@Apt NPs can be actively accumulated in cancerous cells through AS1411 aptamer-nucleolin interaction,thereby,they can be used for targeted hyperthermia.By contrast,both the two materials possess high magnetism and magnetically induced heating effects with SAR value calculated as 394 and 381 Wg-1 Fe.In vivo hyperthermia experiments in tumor-bearing mice showed that the Fe3I4@Apt NPs preferentially accumulating at the tumor site exhibited excellent heating effect that the tumor surface regions can be heated to 39-44℃ when the tumors were exposed to a mid-frequency alternating current magnetic field（ACMF）.By repeatedly intravenous administration and hyperthermia,tumor growth was inhibited over a certain period of time.Notably,AS 1411 aptamer has tumor anti-proliferative effects itself with IG50 at micro molar scale level,while this dosage has little effects on normal cells,which exhibit tumor-selective effects.In vitro,a synergistic effect of AS1141-induced chemotherapy and Fe₃O₄@PEG NPs-induced hyperthermia under ACMF leaded to significantly more cell apoptosis and necrosis compared with AS1411 or Fe₃O₄@PEG NPs-induced alone,demonstrating synergistic effect of hyperthermia and chemotherapy.