Preparation And Evaluation Of A Novel TPGS-L-NETA-Gd Conjugate: A Micellar MR Contrast Agent

Magnetic resonance imaging?MRI?with no X-ray radiation damage,the human body safe,noninvasive,the nervous system and soft tissue high resolution and other unique advantages,in addition to showing the pathological changes,but also functional imaging and in vivo metabolic imaging.The clinical application of this technology continues to develop,the application of MRI contrast agent has also been the rapid development of the most used in clinical use of gadopentetate?Gd-DTPA?.And this gadolinium-containing chelate T₁ contrast agent,rapid metabolism,short time in vivo circulation,angiography is not ideal.There are many studies on the use of different nanomaterials as carriers of Gd³⁺chelate molecules,including liposomes,micelles,dendrimers,silica,carbon nanotubes and the like,and in these carrier materials The preparation of the beam is relatively simple and the preparation cost is relatively low,so it is necessary to develop the micellar type T1 contrast agent.This paper was divided into two chapters.In the first chapter,we designed and synthesized TPGS-L-NETA-Gd and analyzed its characterization.In the second chapter,we evaluated the TPGS-L-NETA-Gd micelles in vitro and in vivo.In the first chapter,we first selected the laboratory made L-NETA chelating agent.L-NETA chelating agent reacted with Gd³⁺to obtain L-NETA-Gd.TPGS-COOH was synthesized,and then L-NETA-Gd and TPGS-COOH under certain conditions of reaction and synthesis of TPGS-L-NETA-Gd.TPGS-L-NETA-Gd micelles were prepared by thin film dispersion method.The stability of TPGS-L-NETA-Gd micelles was determined by DLS,and the particle size was determined by TEM.The critical micelle concentration?CMC?was determined by pyrene fluorescence probe method.Determination of R₁ relaxation degree of L-NETA-Gd and TPGS-L-NETA-Gd under PH=5.5 and PH=7.4 conditions with 3 T MR.The experimental results showed that TPGS-L-NETA-Gd can self assemble into micelles,and its critical micelle concentration?CMC?is 4.3?g/mL.The particle size of the micelles was determined by DLS.The results showed that the stability of TPGS-L-NETA-Gd micelles in water was good.The results of TEM showed that the particle size was about 20 nm.L-NETA-Gd at PH=5.5 and PH=7.4R₁ relaxation values of 2.293 mM^-1S^-1 and 2.290mM^-1S^-1.TPGS-L-NETA-Gd at PH=5.5 and PH=7.4 R₁ relaxation values of 3.453mM^-1S^-1 and 2.534 mM^-1S^-1.In the second chapter,we used HepG2 cells as a cell model,to evaluate the ability of cell uptake of TPGS-L-NETA-Gd micelles,commercially available contrast agent Gd-DTPA was as a positive control group,the content of Gd was determined by ICP-AES,with 3 T MR was observed and analyzed the signal strength of the contrast.The weight of mice was measured,the plasma was collected and the value of AST,ALT,CRE and BUN in plasma were measured.The liver and kidney tissue sections were analyzed and the toxicity of TPGS-L-NETA-Gd was analyzed.We established a mouse model of orthotopic liver cancer,HepG2 transplanted tumor model,and then analyzed the ability of TPGS-L-NETA-Gd micelles with 4.7 T MR and 3 T,respectively.The HepG2 transplanted tumor model was established with BALB/c-nu female,and the distribution of TPGS-L-NETA-Gd micelles in mice was analyzed.Cell uptake experiments showed that the uptake of TPGS-L-NETA-Gd micelles by HepG2 cells was much higher than that of Gd-DTPA.In vitro MRI assay was used to examine the cell uptake,and the signal intensity of HepG2 cells and Gd-DTPA co culture group was 106±1.63%,and the signal intensity of HepG2 cells and TPGS-L-NETA-Gd micelles group was about 137±5.86%.The toxicity test showed that the micelles had low toxicity.The results of in vivo MRI showed that TPGS-L-NETA-Gd significantly increased the tumor area at 45 min.It was found that the TPGS-L-NETA-Gd micelles were unstable in vivo and the long cycle effect was not obvious.The results showed that TPGS-L-NETA-Gd micelles had good biocompatibility and low toxicity,and they had higher targeting compared with Gd-DTPA,but compared with Gd-DTPA,The relaxation rate of TPGS-L-NETA-Gd micelles was relatively low.