Andresen, Thomas Lars

Bruun, Linda Maria

Christiansen, Anders N.

Clausen, Mads Hartvig

Hansen, Anders Elias

Jølck, Rasmus Irming

Kjær, Andreas

Schaarup-Jensen, Henrik

Scherman, Per Jonas Bengtsson

The poster presents the development of a liquid fiducial tissue marker based on sucrose acetate isobutyrate (SAIB) and uniform, coated gold nanoparticles (AuNPs). The PNIPAM-coated AuNP-SAIB gel provided high CT contrast and high in vivo stability and was assessed to be a suitable tissue marker for image guided radiotherapy (IGRT)

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Downloaded from orbit.dtu.dk on: Dec 20, 2017Sucrose acetate isobutyrate-based nanogels as liquid fiducial tissue markers withpotential use in image guided radiotherapyBruun, Linda Maria; Schaarup-Jensen, Henrik; Jølck, Rasmus Irming; Hansen, Anders Elias;Christiansen, Anders N.; Scherman, Per Jonas Bengtsson; Clausen, Mads Hartvig; Kjær, Andreas;Andresen, Thomas LarsPublication date:2014Link back to DTU OrbitCitation (APA):Bruun, L. M., Schaarup-Jensen, H., Jølck, R. I., Hansen, A. E., Christiansen, A. N., Scherman, P. J. B., ...Andresen, T. L. (2014). Sucrose acetate isobutyrate-based nanogels as liquid fiducial tissue markers withpotential use in image guided radiotherapy. Poster session presented at Træf for Organisk KemiStuderende2014, Lyngby, Denmark.BackgroundWithin the field of radiotherapy, modern radiation oncology relies on high precision imagingtechniques like Computed Tomography (CT), Positron Emitting Tomography (PET) andMagnetic Resonance Imaging (MRI) in order to deliver high radiation doses to preciselydefined targets [1-3]. Tumors undergoing fractionated radiation therapy rarely display a fixedposition during irradiation or within treatment, due to changes in organ filling, breathingmotion and tumor size. This usually entails that the planning target volume has to beincreased to ensure radiation dose coverage during treatment [4].Image-guided Radiotherapy (IGRT) is a recently developed technique that has contributed todecrease in planning target volume, as 2D - and 3D images are frequently recorded beforeand during treatment [1,5]. This protocol has reduced treatment toxicity and improvedrelapse-free survival [6]. However, a remaining challenge within IGRT is fixation andcorrelation of the anatomical positions of several tumors to internal fixation points such asthe skeleton. Radiopaque fiducial tissue markers (contrast agents) are therefore implantednear or inside the tumor to facilitate precise localization of tumors during therapy andthereby increase radiation accuracy. Solid markers like gold seeds are used routinely asradiopaque markers due to their excellent radiographic contrast, but the implantationprocedure may cause severe complications [7]. Migration of seeds is likewise an issue. As analternative, liquid fiducial markers are therefore of high interest.Based on our previous work [8] - the work presented in this poster deals with developmentof biocompatible liquid fiducial injectable markers based upon well-defined coated goldnanoparticles (AuNPs) encapsulated within a secondary medium of sucrose acetateisobutyrate (SAIB), PLA (poly-lactic acid) and EtOH (Figure 1). The mixture of PLA, EtOH, SAIBand coated AuNPs forms a Newtonian liquid (50-200 mPa⋅s) that is injectable through thin,hypodermic needles (25 G). Upon injection, efflux of EtOH via non-solvent induced phaseseparation (NIPS) occurs, leading to the formation of a highly viscous, hydrophobic fiducialradiopaque implant.Experimental methodsThe AuNPs were synthesized by a three step seeding protocol using chloroauric acid andtrisodium citrate (Scheme 1). Three different coating options were tested: 1) Thiol-terminated PEG5000 polymers, 2) thiol-terminated PNIPAM3500 polymers and 3) a dithiolanefunctionalized SAIB derivative that was synthesized in 4 steps from sucrose.The AuNP-SAIB gels were made by dispersing the coated AuNPs in EtOH follwed by mixingwith SAIB and PLA. In vitro stability studies of AuNP-SAIB gels were conducted in PBS-bufferat 370C. In vivo contrast and stability of the gels were monitored by micro-CT after injectionof 200μL of SAIB/EtOH/PLA (75:20:5) + 30mg∙mL-1 PNIPAM-AuNPs or 10mg∙mL-1 PEG-AuNPsat the upper left flank of immunocompetent NMRI-mice. The X-ray contrast level, gel volumeand gel homogeneity were evaluated over time by active contour model.ResultsStable and uniform PEG - and PNIPAM-coated AuNPs were successfully synthesized, conferFigure 2. The dithiolane SAIB functionalized AuNPs were discarded due to observedaggregation of the nanoparticles. In-vitro stability test of the PEG-AuNP-SAIB gel (Figure 3)showed rapid burst release of PEGylated AuNPs. This burst release was completely avoided(<1%) with the PNIPAM-AuNP-SAIB gel, even with concentrations up to 100mg∙mL-1.In vivo contrast and stability of the PEG- and PNIPAM-AuNP-SAIB gels were likewise analyzed.The PEG-AuNP-SAIB gel suffered from PEG-AuNP migration towards the gel-boundaries overtime [8]. Figure 4 and 5 show micro-CT scans of mice after injection of the PNIPAM-AuNP-SAIBgel. The PNIPAM-AuNP-SAIB gel provided high stability in vivo, as well as a higher X-raycontrast level than the PEGylated AuNP-SAIB gel (as expected due to higher AuNP loadingbeing possible with the PNIPAM coating).The contrast level and homogeneity of the gels were analyzed manually in each CT scanningslice. First, a bounding box was drawn around each gel, and the gels were segmented by activecontour model [9]. The median values of the two gel types were compared using a Wilcoxonrank-sum test [10]. The homogeneity of the gels was then analyzed by first applying a Box-Coxtransformation [11] to the two datasets for variance stabilization, followed by a Wilcoxon ranksum test for comparison of variance.The PNIPAM-AuNP-SAIB gel had a significantly higher median (P-value: 0.0006) as expecteddue to higher loading of AuNPs. Despite a much better contrast, surprisingly no significantdifference was found in the variance of the gels (P-value: 0.0734), thereby indicating the sameextent of inhomogeneity in the PNIPAM-AuNP-SAIB gel and the PEG-AuNP-SAIB gel. This is dueto the inhomogeneity only being visible at higher intensity levels (Figure 5). Due to the muchlesser resolution in clinical imaging systems, the slight inhomogeneity of the PNIPAM-AuNP-SAIB gel will not be visible and will therefore not be an issue in clinical applications.Handling of PNIPAM-coated AuNPs was furthermore superior to the PEGylated AuNPs, as theycan be lyophilized and stored as a stable powder, that is easily dispersible in EtOH. Based onthe presented in vitro and in vivo results, the PNIPAM-AuNP-SAIB gel was evaluated to besuitable as tissue marker for IGRT.SUCROSE ACETATE ISOBUTYRATE-BASED NANOGELS AS LIQUID FIDUCIAL TISSUE MARKERSWITH POTENTIAL USE IN IMAGE GUIDED RADIOTHERAPYLinda M. Bruun1,2, Henrik Schaarup-Jensen1,3, Rasmus I. Jølck1,2, Anders E. Hansen1,2, Anders N. Christiansen4, Per Jonas BengtssonScherman6, Mads H. Clausen1,3, Andreas Kjær5 and Thomas L. Andresen1,21Technical University of Denmark, Center for Nanomedicine and Theranostics, 2800 Kgs. Lyngby, Denmark2Technical University of Denmark, Department of Micro-and Nanotechnology, 2800 Kgs. Lyngby, Denmark3Technical University of Denmark, Department of Chemistry, 2800 Kgs. Lyngby, Denmark4Technical University of Denmark, DTU Compute, Department of Applied Mathematics and Computer Science, 2800 Kgs. Lyngby, Denmark5Rigshospitalet and University of Copenhagen, Department of Clinical Physiology, Nuclear Medicine & PET and Cluster for Molecular Imaging, 2100 Copenhagen, Denmark.6Department of Oncology, Section of Radiotherapy, Rigshospitalet, 2100 Copenhagen, DenmarkAcknowledgementsThe authors wish to thank the Nanoguide project and the Danish Council For StrategicResearch for financing this project.Figure 3.  In vitro release in PBS-buffer at 37°C from SAIB/EtOH/PLA (75:20:5)  containing either 30mg∙mL-1 PNIPAM-AuNPs (blue)  or 30mg∙mL-1PEGylated-AuNPs (red)Figure 4. Maximum Intensity Projection of a PNIPAM-AuNP-SAIB gel–depot viewed from several anglesFigure 1.  Principle of  the developed liquid fiducial marker.Figure 5. Micro-CT scanning slice of the PNIPAM-AuNP-SAIB gel in a mouse at three contrast levels. At high contrast level, slight inhomogeneity in the AuNP distribution is observedFigure 2. From left to right: UV-Vis -, DLS – andζ-potential characterization of PEG-, PNIPAM- anddithiolane-SAIB coated AuNPs in aqueous solution Scheme 1. Synthesis of PEG-, PNIPAM- and SAIB-coated AuNPsReferences[1]: L. A. Dawson, M. B. Sharpe, Lancet Oncol. 2006, 7, 848[2]: J. Bussink, J. H. A. M. Kaanders, W. T. A. van der Graaf, W. J. G. Oyen, Nat. Rev. Clin. Oncol. 2011, 8, 233[3]: D. Verellen, R.M. De, N. Linthout, K. Tournel, G. Soete, G. Storme, Nat. Rev. Cancer, 2007, 7, 949[4]: K. M. Langen, D. T. Jones, Int. J. Radiat. Oncol. Biol. Phys. 2001, 50, 265[5]: M. Falk, P. M. af Rosenschold, P. Keall, H. Cattell, B. C. Cho, P. Poulsen, S. Povzner, A. Sawant, J. Zimmerman, S. Korreman, Radiother.  Oncol. 2010, 94, 218[6]: M. J. Zelefsky, M. Kollmeier, B. Cox, A. Fidaleo, D. Sperling, X. Pei, B. Carver, J. Coleman, M. lovelock, M. hunt, Int. J. Radiat. Oncol. Biol. Phys. 2012, 84, 125[7]: N. Bhagat, N. Fidelman, J. C. Durack, J. Collins, R. L. Gordon, J. M. LaBerge, R. K. J. Kerlan,  Cardiovasc. Intervent. Radiol. 2010, 33, 1186[8]: R. I. Jølck, T. Binderup, A.E. Hansen, et al. Adv. Healthcare Mater. 2014, 1[9]: T. F. Chan, L. A. Vese, Image Processing, IEEE Transactions on, 2001, 10 (2), 266[10]: F. Wilcoxon, Biometrics 1.6 1945, 80 [11]: G. E. P. Box , D. R. Cox, J. R. Stat. Soc., Series B 26.2 , 1964, 211.The poster presents the development of a liquid fiducial tissue marker based on sucrose acetate isobutyrate (SAIB) and uniform, coated gold nanoparticles (AuNPs). The PNIPAM-coated AuNP-SAIB gel provided high CT contrast and high in vivo stability and was assessed to be a suitable tissue marker for image guided radiotherapy (IGRT).

Sucrose acetate isobutyrate-based nanogels as liquid fiducial tissue markers with potential use in image guided radiotherapy

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Sucrose acetate isobutyrate-based nanogels as liquid fiducial tissue markers with potential use in image guided radiotherapy

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