The Preparation Of PH Response 5ALA-Dex-SPIO And Its Gastrointestinal Cancermetastasislymph Nodes Mapping Effect

Lymph node metastasis is one of main metastasis modes of gastrointestinal cancer.At present,it’s hard to dissect lymph nodes precisely during the operation due to limitations of lymph node tracer technique.This research intended to develop a visualized tracer system for gastrointestinal cancer metastatic lymph nodes.In preliminary jobs,we had invented preparation of dextran ferroferric oxide(Dex-SPIO)nano-carriers;the nano disperse system was highly lymphotropic with excellent black staining effect on lymph nodes,yet it still could not identify cancer metastatic lymph nodes.Therefore,in this research,we combined it with the tumor fluorescence specificity prodrug with smart response,dextran-5-aminolevulinic acid derivative(Dex-5ALA),through coprecipitation method and ultrasonic dispersion technique to successfully prepare pH-responsive fluorescence specificity nanocrystalline ferroferric oxide hybrid system tracer,5-aminolevulinic acid-dextran-ferroferric oxide(5ALA-Dex-SPIO).5ALA-Dex-SPIO has the following advantages:(1)easy and simple operation with excellent biosecurity,the system was black brown liquid which could be locally injected into tumor periphery via mucous membrane or subserous region during the operation without local inflammatory response and could be metabolized quickly after the operation without local drug residues;(2)highly lymphotropic,being with a particle size of 130-170nm,the system could specifically enrich in lymph nodes to realize visualized black staining of lymph nodes;and(3)specific to tumor cells,pH-sensitive key binding ALA could release ALA in local weakly acidic environment of tumors to induce mass accumulation of autofluorescent material-protoporphyrin(PpIX)in cancer cells and increase fluorescence intensity of cancer metastatic lymph nodes so as to precisely differentiate cancer metastatic lymph nodes from normal lymph nodes.Finally,the research group hoped to establish a diagnosis model for cancer metastatic lymph nodes based on 5ALA-Dex-SPIO fluorescence imaging and fluorescent quantitative analysis to provide new ideas for precisely identifying lymph node dissection scope.PurposeThe research aimed to develop a cancer metastatic lymph node tracer,5ALA-Dex-SPIO,and assess its physiochemical property to demonstrate its effectiveness in tracing cancer metastatic lymph nodes;and to probe into its pharmacokinetic rules in in vitro inducing protoporphyrin accumulation in gastrointestinal cancer cells and assess itin vivo and in vitro biosecurity.Method The pH-responsive Dex-ALA macromolecule prodrug was prepared through conjugation of raw materials,dextran and ALA,via pH sensitive key,and then 5ALA-Dex-SPIO was prepared via chemical coprecipitation method with ferric chloride and ferrous chloride(SPIO)as iron sources;then 5ALA-Dex-SPIO,human normal gastric mucosa cells(GES-1),human normal colorectal mucosa cells(FHC),human gastric cancer cells(SGC-7901),human colon cancer cells(SW480)and human lymphatic endothelial cells(LECs)were co-cultured to assess the influence of 5ALA-Dex-SPIO on cell autofluorescence and its in vitro biosecurity;nude mice models of gastrointestinal cancer cells metastatic to axillary periphery were established and 5ALA-Dex-SPIO was locally injected into tumor periphery to assess its effectiveness in tracing cancer metastatic lymph nodes and in vivo biosecurity.Conclusion 5ALA-Dex-SPIO,which has stable physiochemical property,can effectively trace cancer metastatic lymph nodes with excellent safety upon local injection,thereby laying a foundation for establishing a diagnosis model for cancer metastatic lymph nodes and diagnosing cancer metastatic lymph nodes on a real-time basis.