ABSTRACT
Herein, a novel method for the in situ growth of single gold nanoparticles (AuNPs) in microgel (MG) networks is presented. The key feature in this approach is the localization of ß-diketone groups capable of both complexation and reduction of aurate ions in the MGs' core, which allows localization of the nucleation and growth of single AuNPs. The MG synthesis is carried out via precipitation polymerization in water with N-vinylcaprolactam as the main monomer and with the two comonomers acetoacetoxyethyl methacrylate (AAEM) and acrylic acid (AAc), where AAEM is mainly located in the MGs' core and AAc in their shell. For the synthesis of AuNPs, a certain amount of chloroauric acid (HAuCl4 ) is added to the dispersion, followed by fast reduction with sodium borohydride (NaBH4 ). In situ synthesized AuNPs in MGs possess a spherical shape, with a diameter of 8.1 ± 0.8 nm, being localized in the center of every MG. In addition, these AuNPs embedded into MG networks can be used as seeds that grow in their size after the addition of HAuCl4 up to 46.0 ± 9.5 nm under mild reaction conditions (room temperature, aqueous dispersion) and without the use of any additional reducing and stabilizing agents.
ABSTRACT
INTRODUCTION: The risk of spinal cord ischemia is a relevant problem in in fields of open and endovascular thoracoabdominal aortic aneurysm repair (TAAA). Despite all efforts, no therapeutical concept exists, which enables a complete treatment of the TAAA without open branches or fenestrations, and reduces the risk for a spinal cord ischemia (SCI) to the minimum. In this article, we would like to present a new concept based on slow-occluding hydrogel-textile membrane, which could help to reduce the SCI risk during endovascular TAAA repair. CONCEPT: A hydrogel textile membrane is under development, which could be used a functional unit of endovascular stentprosthesis. If in contact with blood, glutathion induces swelling of the induces ongoing swelling of the membrane because of the triggered degradation of the crosslinker. Due to the resulting water uptake of the hydrogel textile membrane and mass increase of the gel, the swelling leads to a stabilization of the membrane. In vitro studies show, that the swelling of the hydrogel textile membrane should lead to a controlled decreasing flow into the aneurysm sac. After a pre-defined period, the membrane is occluded and the aneurysm sac perfusion stops. So, by using the hydrogel textile membrane, a complete treatment of the TAAA can be realized in one procedure without further re-intervention or pre-interventional measures. Furthermore, the risk of a SCI would be minimized. As this treatment concept is under development, only interim results are presented. CONCLUSION: The successful development and usage of a slow-occluding hydrogel textile membrane as a part of endovascular stentprosthesis could help to reduce the risk SCI during endovascular TAAA surgery.
Subject(s)
Aortic Aneurysm, Thoracic , Blood Vessel Prosthesis Implantation , Endovascular Procedures , Spinal Cord Ischemia , Blood Vessel Prosthesis , Humans , Risk Factors , Spinal Cord , Spinal Cord Ischemia/surgery , Stents , Treatment OutcomeABSTRACT
We report the synthesis of poly(N-vinylcaprolactam) nanogels (PVCL NGs) loaded with gadolinium (Gd) for tumor MR imaging applications. The PVCL NGs were synthesized via precipitation polymerization using the monomer N-vinylcaprolactam (VCL), the comonomer acrylic acid (AAc), and the degradable cross-linker 3,9-divinyl-2,4,8,10-tetraoxaspiro-[5,5]-undecane (VOU) in aqueous solution, followed by covalently binding with 2,2',2â³-(10-(4-((2-aminoethyl)amino)-1-carboxy-4-oxobutyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl) triacetic acid (NH2-DOTA-GA)/Gd complexes. We show that the formed Gd-loaded PVCL NGs (PVCL-Gd NGs) having a size of 180.67 ± 11.04 nm are water dispersible, colloidally stable, uniform in size distribution, and noncytotoxic in a range of the studied concentrations. The PVCL-Gd NGs also display a r1 relaxivity (6.38-7.10 mM-1 s-1), which is much higher than the clinically used Gd chelates. These properties afforded the use of the PVCL-Gd NGs as an effective positive contrast agent for enhanced MR imaging of cancer cells in vitro as well as a subcutaneous tumor model in vivo. Our study suggests that the developed PVCL-Gd NGs could be applied as a promising contrast agent for T1-weighted MR imaging of diverse biosystems.
