Thermosensitive Cationic Magnetic Liposomes for Thermoresponsive Delivery of CPT-11 and SLP2 shRNA in Glioblastoma Treatment.

Thermosensitive cationic magnetic liposomes (TCMLs), prepared from dipalmitoylphosphatidylcholine (DPPC), cholesterol, 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)]-2000, and didodecyldimethylammonium bromide (DDAB) were used in this study for the controlled release of drug/gene for cancer treatment. After co-entrapping citric-acid-coated magnetic nanoparticles (MNPs) and the chemotherapeutic drug irinotecan (CPT-11) in the core of TCML (TCML@CPT-11), SLP2 shRNA plasmids were complexed with DDAB in the lipid bilayer to prepare TCML@CPT-11/shRNA with a 135.6 ± 2.1 nm diameter. As DPPC has a melting temperature slightly above the physiological temperature, drug release from the liposomes can be triggered by an increase in solution temperature or by magneto-heating induced with an alternating magnetic field (AMF). The MNPs in the liposomes also endow the TCMLs with magnetically targeted drug delivery with guidance by a magnetic field. The successful preparation of drug-loaded liposomes was confirmed by various physical and chemical methods. Enhanced drug release, from 18% to 59%, at pH 7.4 was observed when raising the temperature from 37 to 43 °C, as well as during induction with an AMF. The in vitro cell culture experiments endorse the biocompatibility of TCMLs, whereas TCML@CPT-11 shows some enhancement of cytotoxicity toward U87 human glioblastoma cells when compared with free CPT-11. The U87 cells can be transfected with the SLP2 shRNA plasmids with very high efficiency (~100%), leading to silencing of the SLP2 gene and reducing the migration ability of U87 from 63% to 24% in a wound-healing assay. Finally, an in vivo study, using subcutaneously implanted U87 xenografts in nude mice, demonstrates that the intravenous injection of TCML@CPT11-shRNA, plus magnetic guidance and AMF treatment, can provide a safe and promising therapeutic modality for glioblastoma treatment.

Thrombolysis induced by intravenous administration of plasminogen activator in magnetoliposomes: dual targeting by magnetic and thermal manipulation.

In previously published studies, intra-arterial (i.a.), but not intravenous (i.v.) delivery of recombinant tissue-type plasminogen activator (rtPA) immobilized on the surface of magnetic nanoparticles induces thrombolysis by magnetic targeting. We asked whether i.v. delivery of protected rtPA in a thermosensitive magnetoliposome (TML@rtPA) may achieve target thrombolysis. PEGylated TML@rtPA was optimized and characterized; controlled release of rtPA was achieved by thermodynamic and magnetic manipulation in vitro. The lysis index of TML@rtPA incubated with blood at 43 °C vs. 37 °C was 53 ±â€¯11% vs. 81 ±â€¯3% in thromboelastograms, suggesting thermosensitive thrombolysis of TML@rtPA. In a rat embolic model with superfusion of 43 °C saline on a focal spot on the iliac artery with clot lodging, release of rtPA equivalent to 20% regular dose from TML@rtPA administered i.a. vs. i.v. significantly restored iliac blood flow 15 vs. 55 min after clot lodging, respectively. TML@rtPA with magnetic guiding and focal hyperthermia may be potentially amendable to target thrombolysis.

Magnetically controlled release of recombinant tissue plasminogen activator from chitosan nanocomposites for targeted thrombolysis.

Ionic cross-linking of water-soluble chitosan with sodium tripolyphosphate in the presence of recombinant tissue plasminogen activator (rtPA) and magnetite (Fe3O4) nanoparticles could produce rtPA-encapsulated magnetic chitosan nanoparticles (MCNPs-rtPA). MCNPs do not elicit cytotoxicity and hemolysis in vitro. MCNPs-rtPA showed a negligible release of the rtPA protein when stored in phosphate buffer for 28 days. In contrast, the burst release of rtPA from MCNPs-rtPA was found in the serum with 60% of the original activity released in 30 min. The drug release into the serum is also magnet-sensitive; the release could be turned down with a magnetic field when MCNPs-rtPA was pelleted and reversibly turned on after removing the magnetic field when MCNPs-rtPA was dispersed. An in vitro thrombolytic study by thromboelastometry indicated a controlled release of rtPA from MCNPs-rtPA. In a rat embolic model where a preformed blood clot lodged in the left iliac artery upstream of the pudic epigastric branch, MCNPs-rtPA (0.2 mg kg-1 rtPA) was administered and guided magnetically to the clot, followed by mobile magnetic guidance for 60 min. Iliac blood flow increased immediately in response to the treatment, and reached a stable level ∼50 min after drug administration and the hind limb perfusion rate was restored from 53% to 75% of the basal level. Effective thrombolysis was therefore successfully demonstrated at an rtPA dose equivalent to 20% of the regular dose when the MCNPs-rtPA pellet was magnet-guided to the blood clot, followed by a triggered release of rtPA when switched to mobile magnetic guidance.