Basic Research Of Trafficking Degradation Of PLGA Scaffold In Vivo By Labeling Gold Nanoclusters

ObjectiveThis study used a new type of fluorescent nanomaterials ——gold nanoclusters as a marker to label the poly lactic-co-glycolic acid(PLGA).Fluorescence imaging and X-ray computed tomography(CT)imaging were used to monitor the degradation of PLGA scaffolds in mice,To explore the feasibility and accuracy of this method,thus providing a new method for monitoring the degradation of scaffold materials in vivo.Methods1.Gold nanoclusters(AuNanoclusters,AuNCs)were synthesized with HAuCl4 and bovine serum albumin(BSA).High-resolution transmission electron microscopy was used to observe the nanostructure,ultraviolet light was used to detect the fluorescence,and Micro-CT was used to detect the X-ray attenuation property.Fluorescence spectrophotometer measured the fluorescence spectra of AuNCs,and the UV-VIS spectrophotometer measured the absorption spectra of AuNCs.The cytotoxicity of gold nanoclusters was detected by real time cellular analysis and CCK-8 assay.2.The porous AuNCs labeled PLGA(AuNCs/PLGA)scaffold was fabricated by freeze drying method.Pure-PLGA scaffold acted as control group.The fluorescence of the AuNCs/PLGA was detected with UV light at 365 nm,CT image of the scaffold detected by micro-CT.Scanning electron microscopy was used to detect the surface structure.Laser scanning confocal microscopy identified the fiber structure of scaffold and the distribution of gold nanoclusters.3.Sterilized AuNCs/PLGA scaffold was implanted subcutaneously in nude mice.The experimental group was performed with the fluorescence imaging and Micro-CT scanning for a period of 4 weeks.Analysing the fluorescence changes of the scaffolds,and using the Mimics software to analyze the results of CT,reconstruct the 3D morphology of scaffolds,and measure the CT value.At the same time,the quality of the scaffolds was measured,and the correlation between the quality of the scaffold and the imaging results was analyzed.Results1.Synthesized AuNCs showed red fluorescence under ultraviolet light and x-ray attenuation property.High-resolution transmission electron microscopy showed that AuNCs was a spherical particle with a diameter of about 2nm.The fluorescence spectra showed that AuNCs have two excitation peaks at 350 nm and 440 nm,emission peak at 700 nm.The absorption spectra show that the absorption peak of AuNCs is at 280 nm.Cytotoxicity test showed that AuNCs had no cytotoxicity.2.The AuNCs/PLGA scaffold showed red fluorescence and CT imaging property.The pore diameter of the support is about 20 μm.Laser confocal microscopy showed that the gold nanoclusters were distributed in the fiber structure of scaffold.3.Within first weeks,the fluorescence intensity of the scaffolds decayed quickly,then slowdown in the following weeks.The curve of fluorescence change was not consistent with the curve of the quality of scaffold.The results of CT image showed that the scaffolds were degraded gradually from the edge,the degradation was completed by the end of the fourth week.The change of CT value is close to the change of scaffold quality.Conclusion1.The synthesized AuNCs can be used for fluorescence imaging and CT imaging and showed no obvious cytotoxicity,therefore can act as the marker of scaffold materials.2.The AuNCs/PLGA scaffolds can meet the requirements of fluorescence imaging and CT imaging.3.Compared with fluorescence imaging,CT imaging technology can more accurately monitor the degradation of labeled PLGA scaffolds in vivo.