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The major draw backs of chemotherapy includes mainly the poor solubility, specficity, stability of drugs and assisted delivery systems are found promising in overcoming this problem. Sorafenib, a class of novel multikinase inhibitors is being restircted to fewer pharmacological effects due to its poor solubility and pharmacokinetics. In the present study sorfenib was successfully loaded on mesoporous silica nanospheres with a loading efficiency of 93% and size of 396 nm. Cytotoxicity checking with normal fibroblast cells shown increased toxicity of sorafenib alone over loaded form which can be attributed to specificity of drug release. The particles were found to induce cell death in HT 29 colorectal cancer cell lines in a dose dependent manner with IC 50 values of 50μg/ml. The results draw new insights in use of silica nanospheres as potent delivery systems for multikinase inhibitors Introduction The multikinase inhibitors sorafenib and sunitinib is clinically proved to be effective in patients with colorectal cancer, renal cell cancer and hepatocellular cancer (liu l et al, 2006) Sorafenib is a multikinase inhibitor of Raf, and it inhibits tumor cell proliferation and vascularisation by the activation of the receptor for tyrosine kinase signaling in the Ras/Raf/Mek/Erk cascade pathway. It has also been shown to block tumor cell proliferation and angiogenesis by inhibiting serine/threonine kinases (c-RAF, and mutant and wild-type BRAF) as well as the receptor tyrosine kinases vascular endothelial growth factor receptor 2 (VEGFR2), VEGFR3, platelet-derived growth factor receptor (PDGFR), FLT3, Ret, and c-KIT. The limitations of sorafenib including lesser solubility pose concerns over pharmacokinetics of the drug. The recent findings reported regarding adverse drug reactions including Hand-foot disease(Wood et al,2010), hypertension, nausea, muscle pain is quite alarming. In this aspect assisted delivery systems can be quite worthy and silica mesospheres offer a promising candidate in this context. Silicon is the second most abundant element in the earth and it is readly excreted into urine as orthosilicic acid ( reffitt et al,1999) generating minimum toxicity. Silica in its Nano form has good properties like good mechanical and thermal stability, it is chemically inert and has low density. According to WCRF, colorectal cancer is the third most common cancer in both men and women. The recent reports of National cancer institute estimates, that around 136,830 new cases of colorectal cancer will be reporting and death due to colon cancer is about 96,830 in 2014. It is a cancer that forms in the tissues of colon. Most colon cancers are adenocarcinomas (cancers that begin in cells that make and release mucus or other fluids) and inefficacy of existing therapeutic regimens necessitates the need for novel delivery systems. Materials and Methods Tetraethyl ortho silicate (TEOS) 99%, Ethanol, Ammonia solution 25% were obtained from Merck specialities, India. Dulbecco,s Modified eagles media(DMEM), Trypsin, Fetal bovine serum(FBS), 3-(4, 5dimethythiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) were obtained from Invitrogen. All the other chemicals used were of superior analytical grade. Cell lines L929 ( Murine fibroblast cells ), HT 29 ( colorectal carcinoma) were obtained from NCCS, pune and maintained in Dulbecco,s Modified eagles media supplemented with 10% FBS Synthesis of Mesoporous silica Nanospheres Mesoporous silica nanospheres was prepared by sol-gel method ( Stober et al,1968) . 1.5ml of tetraethyl orthosilicate (TEOS-99%) and 50 ml of ethanol was heated at 64°C for 1-2 hours. 2.5ml ammonia was added drop wise to the resulting solution and stirred continuously for 18 hours. Nanospheres were extracted by centrifugation at 10,000g at 4°C for 10 minutes. The pellets were washed with ethanol 3times and particles (MSN) were air dried. Preparation of drug loaded Nanospheres Drug loaded Nanospheres was prepared by dissolving 200mg sorafenib in 1ml ethanol. 200mg of synthesized particles were added to the above mixture and stirred for 48hours at 500rpm. The particles were recovered by centrifugation at 10,000g at 4°C for 15 minutes. The pellet was washed for 3 times with acetone and particles (SMSN) were air dried. Zeta Sizer Analysis Particle size and size distribution were determined using Zetasizer ( brookhaven Instruments cooperation) . Measurements were recorded at 25°C suspended in Hepes buffer (ionic strength 40mM, pH 7.4) with a Ag electrode using Phase Analysis light scattering mode. The zeta (ζ)potential was automatically calculated from electrophoretic mobility based on the smoluchowski equation, v=(e.E/η)ξ. Where, v= electrophoretic velocity |
