New 99mTc - silica nanoparticles radiotracer biodistribution studied through scintigraphy

Abstract

Aim of the study: Silica nanoparticles (SNP) are a new and versatile tool for targeting drug delivery. Our aim was to investigate biodistribution of a new SNP derivate in guinea pigs, in order to identify the possible uses as a drug carrier. Materials: SNP were prepared at the Institute o f Chemistry and Bioanalytics, University o f Applied Sciences Northwestern Switzerland, Muttenz, Switzerland. One 124 nm size SNP derivate was used: AA124 - SNP carrying OH groups on the surface. Methods: The procedure of 99mTc - SNP coupling was an in-house preparation performed as follows: 1- first of all, SNP were suspended in EtOH (5mg/ml) and sonicated for 15 or 20 min for better disper­sion. 2- to this suspension, 200MBq/lml of Na99mTc04 solution was added and the suspension was stirred gently. 3- an excess of NaBH4 reducing agent was added quickly to the suspension and stirred for minimum 1 hour. Scintigraphic study design: Groups of 4 animals were intravenously administered with 37MBq/kg/ animal 99mTc-coupled AA124 SNP. Control groups received 37MBq/kg animal 99mTc. A dual head Siemens gamma camera with high resolution parallel collimators was used. The image acquisitions protocol started with a dynamic image acquisition for 60 seconds (1 image/sec), followed by a dynamic image acquisition for 4 minutes (1 image/min) and static planar images (256x256 Matrix, Zoom 2) every 15 minutes for a duration of 2h. The animals were sacrificed after 120 min and different organs were extracted entirely and submited to gamma camera. Results: Following the i.v. administration, AA124 SNP did not penetrate the blood brain barrier. SNP were present in all the organs investigated except the brain, with different target/non target indexes, that were graphically represented for each of them. Conclusion: These step results represent a promising support for the idea of using the AA124 as container for modular drug delivery system with promising future in therapeutics.