X-ray imaging of gold nanoparticle loaded alginate microcapsules

Abstract

Event Abstract Back to Event X-ray imaging of gold nanoparticle loaded alginate microcapsules Fengxiang Qie1, 2, Alberto Astolfo3, Astrid Kibleur3*, Xiaojuan Hao1, Tianwei Tan2* and Timothy Hughes1 1 CSIRO, Manufacturing, Australia 2 Beijing University of Chemical Technology, Beijing Key Lab of Bioprocess, China 3 Australian Synchrotron, Australia Introduction: Cell based therapy has the potential to treat a wide range of diseases. One potential solution to enable immuno-isolation of the transplanted cells is to encapsulate the cells in alginate microcapsules (MCs). The aim of this project is to develop a non-invasive and simple technique that permits the tracking of the position and integrity of the MCs when placed in laboratory animals. Information obtained from tracking the MCs will help to guide best practice as encapsulated cells are being contemplated for clinical therapies, for example, for treatment of insulin-dependent diabetes. Materials and Methods: Gold nanoparticles (AuNPs) were prepared by the citrate reduction method [1]. Poly((2-methacryloyloxy)ethyl trimethyl ammonium chloride), a positively charged polymer, and poly (ethylene glycol), a non-charged polymer were prepared via RAFT polymerisation and coated onto the AuNPs as prepared, i.e. containing dithioester end groups. Alternatively, the RAFT end groups were cleaved off affording the corresponding thiol-capped polymers which were then coated onto AuNPs. These polymer-modified AuNPs were then encapsulated (blended) in alginate MCs (~500 μm) [2].Alternatively the polymer-modified AuNPs were coated onto preformed alginate MCs via electrostatic self-assembly [3]. The cytotoxicity and mechanical stability of the AuNPs containing MCs were assessed. The attenuation coefficients were measured for both blended and coated AuNPs MCs. Finally, both the blended and coated AuNPs containing MCs were implanted into cadaver mice and X-ray imaged in order to test their ability to track alginate MCs within the body by x-ray imaging. Results and Discussion: Both blended and coated AuNP-MC composites were found to have low cytotoxicity. In addition, they were found to be mechanically stable under shaking at 37oC for more than 1 month with no measurable loss of the contrast agent. The results of our preliminary experiments conducted at the IMBL (Australian Synchrotron, Melbourne, Australia) and at SYRMEP (Elettra, Trieste, Italy) beamlines have shown that gold nanoparticles (AuNPs) are an attractive solution for MCs tracking if combined with x-ray computed tomography (CT). The AuNPs coated MCs gave a higher X-ray attenuation than the corresponding blended AuNPs-MCs at the same gold concentration due to their higher localised Au concentration. Figure1: Preparation of both blended and coated AuNPs containing alginate MCs Conclusions: X-ray imaging of encapsulated AuNPs modified with RAFT polymers is a promising methodology to track alginate MCs in situ that may be used as drug delivery devices or to encapsulate cells for cell therapy (eg. diabetes treatment). MCs decorated with a AuNPs coating were more readily identified than AuNPs blended into MCs at the same gold concentration due to the distinctive circular contrast of the coated MCs potentially enabling them to be used for in vivo tracking experiments over multiple time points. We acknowledge the travel funding provided by the International Synchrotron Access Program (ISAP) managed by the Australian Synchrotron and funded by the Australian Government. The authors thank the Chinese Scholarship Council (CSC) and CSIRO for the financial support to Fengxiang Qie