Polymeric vehicles assembled via multilayer deposition of polymers on sacrificial templates have shown promising potential as the next generation of advanced biomedical materials due to their controllable shape and stimuli-responsive properties. Multilayer microcapsules of the polyphenol, tannic acid (TA), and poly(N-vinylcaprolactam) (PVCL) are particularly interesting due to their large capacity for drug loading and ultrasound-triggered release of payload. However, there is the need for spatial localization of the delivery vehicles in the body after administration. Magnetic resonance imaging (MRI) is a powerful tool for medical diagnostics and the de-facto standard for precision imaging in medical settings. A multilayer assembly using a (PCVL-transition metal complex) copolymer that enables MRI has been developed. Currently, there is no common MRI contrast agent that can be tuned to increase contrast on demand within the human body. However, the transition metal complex tris(2,2’-bipyridine)ruthenium(II), [Ru(bpy)3]+2 has been shown to oscillate between oxidation states that are either para- or diamagnetic as part of the Belousov-Zhabotinsky (BZ) reaction, resulting in “on/off” MRI contrast. Motivated by this capability, a series of copolymers consisting of PVCL with pendant [Ru(bpy)3]+2 complexes with PVCL to [Ru(bpy)3]+2 ratios of 1:1 and 2:1 were created through free radical polymerization. The ability of the copolymers to participate in redox reactions was demonstrated with 2,2-Azinobis(3-ethylbenzothiazoline-6-sulfonic acid) and a version of the BZ reagent system. We showed that these copolymers can be used to fabricate multilayer microcapsules of (PVCL-Ru/TA)n through multilayer polymer deposition onto sacrificial silica templates followed dissolution of the template. Our results indicate that these capsules may provide multimodal imaging through MRI contrast representing a step forward in the field of advanced therapeutic carriers.

Multilayer microcapsules from MRI-compatible poly(N-vinylcaprolactam)-co-ruthenium copolymer with ultralow magnetic susceptibility

2019 Spring National Meeting

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