The therapeutic use of magnetic field effects on intramembranous radical pair mechanisms, a promising new application to liposomal drug-delivery systems (DDSs), will depend to a large degree on technological improvements in the membrane structure of liposomes equipped with various ions and properties. Our previous reports already provided valuable findings about the potential of liposomal DDSs with magnetic controls. In the present research, we used flutamide (FM) as a radical pair-forming drug to investigate whether magnetic fields can control the drug release through changes in the physical properties of membranes.
For the quantitative analysis of FM-corresponding escape-radicals, we utilized the rate of the disappearance of FM, and the appearance of a cleavage product derived from a FM-corresponding cage product. The relative yields of the escape-radical with magnetic field effects ΦER were determined referring to the reported method, based on the following relation:
ΦER = Φ–FM – ΦUP – ΦCP
(1)
where Φ–FM is the FM-photodegradation yield, ΦUP is the yield related to the radical pair-unrelated photoreaction product, and ΦCP is the yields related to the radical pair-corresponding cleavage product.
Judging from the overall result of our liposomes prepared in this research, the escape-radical releases obtained using a magnetic field of 0.25 T had not gone as completely as it could have gone. Such differences in the field dependence, we believe, are results of the liposomal membrane packing and the influence of free radicals generated from a cage product derived from a FM-corresponding singlet radical pair, independently of the escaping process of a FM-corresponding triplet radical pair.
We assumed the possibility that the precision of liposomal drug releases with magnetic controls may be obtained by having no bis-allyl proton in its membrane structures. In addition, it may be supposed that at least 0.1 T is needed for detectable magnetic field effects.