title: Long-circulating monensin nanoparticles for the potentiation of immunotoxin and anticancer drugs.
abstract: The carboxylic ionophore monensin was formulated into long-circulating nanoparticles with the help of polyethylene glycol/poly (DL-lactide-co-glycolide) diblock copolymers, in an attempt to enhance the cytotoxicity of a ricin-based immunotoxin, anti-My9, and anticancer drugs like adriamycin and tamoxifen. This study looked into various aspects involving the preparation (using a homogenizer and an EmulsiFlex homogenizer-extrusion device) and lyophilization of long-circulating monensin nanoparticles (LMNP) of particle size < 200 nm in diameter. The particle size of LMNP was reduced from 194 nm to 160 nm by passing the nanoparticles through an EmulsiFlex, before freeze-drying. There was a 4.8-83.7% increase in the particle size of LMNP after freeze-drying, which was dependent upon the manufacturing conditions such as use of the EmulsiFlex for size reduction before freeze-drying, the freezing method (rapid/slow) and the concentration of lyoprotectant (mannitol or trehalose) employed for freeze-drying. LMNP freeze-dried with 2.4% of trehalose showed minimal size change (< 9%) after freeze-drying. Further, the freezing method was found to have negligible effect on the particle size of LMNP freeze-dried with trehalose in comparison with mannitol. The entrapment efficiency of monensin in LMNP was found to be 14.2 +/- 0.3%. The LMNP were found to be spherical in shape and smooth in surface texture as observed by atomic force microscopy. In-vitro release of monensin from LMNP in phosphate buffered saline (PBS) pH 7.4 or PBS supplemented with 10% human serum indicated that there was an initial rapid release of about 40% in the first 8 h followed by a fairly slow release (about 20%) in the next 88 h. In-vivo studies conducted with Sprague-Dawley rats showed that 20% of monensin remained in circulation 4-8 h after the intravenous administration of LMNP. An in-vitro dye-based cytotoxicity assay (MTS/PMS method) showed that there was 500 times and 5 times potentiation of the cytotoxicity of anti-My9 immunotoxin by LMNP (5 x 10(-8) M of monensin) in HL-60 sensitive and resistant human tumour cell lines, respectively. Further, LMNP (5 x 10(-8) M of monensin) potentiated the cytotoxicity of adriamycin in MCF 7 and SW 620 cell lines by 100 fold and 10 fold, respectively, and that of tamoxifen by 44 fold in MCF 7 cell line as assessed by crystal violet dye uptake assay. Our results suggest that it is possible to prepare LMNP possessing appropriate particle size (< 200 nm), monensin content and in-vitro and in-vivo release characteristics with the help of a homogenizer and an EmulsiFlex homogenizer-extrusion device. LMNP can be freeze-dried with minimal increase in particle size by using a suitable concentration of a lyoprotectant like trehalose. Furthermore, LMNP could potentiate the cytotoxicity of immunotoxin, adriamycin and tamoxifen by 5-500 fold in-vitro, which will be further investigated in-vivo in a suitable animal model.
authors.affiliation: Division of Pharmaceutics, College of Pharmacy, Florida A&M University, Tallahassee 32307, USA.
authors.forename: M S
authors.initials: MS
authors.lastname: Shaik
authors.forename: O
authors.initials: O
authors.lastname: Ikediobi
authors.forename: V D
authors.initials: VD
authors.lastname: Turnage
authors.forename: J
authors.initials: J
authors.lastname: McSween
authors.forename: N
authors.initials: N
authors.lastname: Kanikkannan
authors.forename: M
authors.initials: M
authors.lastname: Singh
mesh_terms: D000818:Animals; D000935:Antifungal Agents / Q000276:immunology / Q000493:pharmacokinetics* / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology*; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D004317:Doxorubicin / Q000494:pharmacology*; D004347:Drug Interactions; D005079:Excipients / Q000737:chemistry; D005612:Freeze Drying; D006207:Half-Life; D006863:Hydrogen-Ion Concentration; D000922:Immunotoxins / Q000494:pharmacology*; D008985:Monensin / Q000276:immunology / Q000493:pharmacokinetics* / Q000494:pharmacology; D010316:Particle Size; D011092:Polyethylene Glycols / Q000737:chemistry; D011108:Polymers; D051381:Rats; D017207:Rats, Sprague-Dawley; D012276:Ricin / Q000494:pharmacology*; D013629:Tamoxifen / Q000494:pharmacology*
chemical_list: D000935:Antifungal Agents; D000970:Antineoplastic Agents; D000972:Antineoplastic Agents, Phytogenic; D005079:Excipients; D000922:Immunotoxins; D011108:Polymers; D013629:Tamoxifen; D011092:Polyethylene Glycols; D004317:Doxorubicin; D012276:Ricin; D008985:Monensin