Folic acid modified Fe3O4 nanoclusters by a one-step ultrasonic technique for drug delivery and MR imaging

Multifunctional nanoclusters based on Fe₃O₄ nanoparticles for magnetic resonance imaging (MRI) and drug delivery are reported here. At first, oleic acid (OA)-coated Fe₃O₄ nanoparticles were prepared. Then block copolymer Pluronic F127 or folic acid (FA) conjugated-Pluronic F127 was used to modify the hydrophobic nanoparticles to become hydrophilic Fe₃O₄@F127 nanoclusters via facile ultrasonic treatment. During this process, drug molecules can also be introduced into the nanoclusters and therefore the targeted drug delivery system was formed. Next, we verified the feasibility of the nanoclusters as drug delivery vehicles and magnetic contrast agents. The nanoclusters have an average size of 200 nm and remained stable in water for long periods. Folic acid-modified nanoclusters showed an enhanced intracellular uptake into HepG2 cells by using both cellular iron amount analysis and flow cytometry analysis. Besides, Fe₃O₄@F127@FA nanoclusters showed good compatibility in the tested concentration range and good sensitivity in T₂-weighted MRI. The magnetic nanoclusters combined with drug delivery properties have greatly increased the significance in the diagnosis and therapy of diseases, which are suitable for systematical administration of hydrophobic drugs and simultaneously MRI diagnosis.

Water-soluble Fe₃O₄@F127@FA nanoclusters were prepared by a facile ultrasonic-treated method for MR imaging and targeted drug delivery.

An ultra-sensitive T2-weighted MR contrast agent based on Gd3+ ion chelated Fe3O4 nanoparticles

An ultra-sensitive T₂-weighted MR imaging contrast agent was prepared based on Fe₃O₄ nanoparticles and Gd³⁺ ions (Fe₃O₄@Gd). Amino modified Fe₃O₄ nanoparticles were conjugated to diethylenetriamine pentaacetic acid, and finally coordinated with Gd³⁺ ions. The nanoparticles had a uniform morphology with a size of 100 nm and a Gd/Fe mass ratio of 1/110. The r₂ (transverse relaxivity) of the Fe₃O₄ nanoparticles increased from 131.89 mM⁻¹ s⁻¹ to 202.06 mM⁻¹ s⁻¹ after coordination with Gd³⁺ ions. MR measurements showed that the aqueous dispersion of Fe₃O₄@Gd nanoparticles had an obvious concentration-dependent negative contrast enhancement. Hepatoma cells were selected to test the cytotoxicity and MR imaging effect. The application of Fe₃O₄@Gd nanoparticles as contrast agents was also exploited in vivo for T₂-weighted MR imaging of rat livers. All the results showed the effectiveness of the nanoparticles in MR diagnosis.

An ultra-sensitive T₂-weighted MR imaging contrast agent was prepared based on Fe₃O₄ nanoparticles and Gd³⁺ ions (Fe₃O₄@Gd).

Facile fabrication of water-dispersible nanocomposites based on hexa-peri-hexabenzocoronene and Fe3O4 for dual mode imaging (fluorescent/MR) and drug delivery

Water-dispersible, stable and biocompatible dandelion-like Fe₃O₄/HBC@F127 nanocomposites were facilely developed for dual mode imaging (fluorescent/MR) and drug delivery.

Effects of microinjection of melatonin and its receptor antagonists into anterior hypothalamic area on blood pressure and heart rate in rats

AIM

To examine the effects of microinjection of melatonin and its receptor antagonists into the anterior hypothalamic area (AHA) on blood pressure (BP) and heart rate (HR) in normotensive and stress-induced hypertensive rats.

METHODS

Melatonin and its receptor antagonists were microinjected into the AHA, then BP, mean arterial pressure (MAP), and HR were synchronously recorded.

RESULTS

Microinjection of melatonin produced a fall in MAP. Prazosin, an antagonist of melatonin ML2 receptor, could not antagonize the depressive response induced by melatonin. While luzindole, a competitive antagonist of melatonin ML1 receptor, was able to almost completely prevented the depressive response induced by injection of melatonin.

CONCLUSION

Melatonin acts as a hypotensive factor and the effects are mainly due to activation of ML1 receptors in rat brain, and the AHA may be one of the important central areas where melatonin can exert modulatory effects on BP and HR.