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There is a growing interest in using hydrogels for biomedical applications, because of more favourable characteristics. Some of these hydrogels can be activated by using particular stimuli, for example electrical fields. These stimuli can change the hydrogel shape in a predefined way. It could make them capable of adaptation to patient-specific anatomy even post-implantation. This is the first paper aiming to describe in vivo studies of an electro-responsive, Pluronic F127 based hydrogel, for intravascular applications. Pluronic methacrylic acid hydrogel (PF127/MANa) was in vitro tested for its haemolytic and cytotoxic effects. Minimal invasive implantation in the carotid artery of sheep was used to evaluate its medium-term biological effects, through biochemical, macroscopic, radiographic, and microscopic evaluation. Indirect and direct testing of the material gave no indication of the haemolytic effects of the material. Determination of fibroblast viability after 24 h of incubation in an extract of the hydrogel showed no cytotoxic effects. Occlusion was obtained within 1 h following in vivo implantation. Evaluation at time of autopsy showed a persistent occlusion with no systemic effects, no signs of embolization and mild effects on the arterial wall. An important proof-of-concept was obtained showing biocompatibility and effectiveness of a pluronic based electro-responsive hydrogel for obtaining an arterial occlusion with limited biological impact. So the selected pluronic-methacrylic acid based hydrogel can be used as an endovascular occlusion device. More importantly it is the first step in further development of electro-active hydrogels for a broad range of intra-vascular applications (e.g. system to prevent endoleakage in aortic aneurysm treatment, intra-vascular drug delivery).

Smart hydrogels for biomedical applications are highly researched materials. However, integrating them into a device for implantation is difficult. This paper investigates an integrated delivery device designed to deliver an electro-responsive hydrogel to a target location inside a blood vessel with the purpose of creating an occlusion. The paper describes the synthesis and characterization of a Pluronic/methacrylic acid sodium salt electro-responsive hydrogel. Application of an electrical bias decelerates the expansion of the hydrogel. An integrated delivery system was manufactured to deliver the hydrogel to the target location in the body. Ex vivo and in vivo experiments in the carotid artery of sheep were used to validate the concept. The hydrogel was able to completely occlude the blood vessel reducing the blood flow from 245 to 0 ml/min after implantation. Ex vivo experiments showed that the hydrogel was able to withstand physiological blood pressures of > 270 mm·Hg without dislodgement. The results showed that the electro-responsive hydrogel used in this paper can be used to create a long-term occlusion in a blood vessel without any apparent side effects. The delivery system developed is a promising device for the delivery of electro-responsive hydrogels.

ABSTRACT Typically, electroresponsive hydrogels have either a high electrical conductivity with little swelling or large swelling with low conductivity. This paper investigates a method of maintaining high swelling capabilities and increasing electrical conductivity by infusing multiwalled carbon nanotubes (MWCNTs) into a hydrolyzed polyacrylamide hydrogel. Various concentrations of MWCNT and Nafion solutions infused into the hydrogel were investigated. Optical microscopy analysis showed aggregates of carbon nanotube bundles at the macroscale, whereas electron microscopy revealed homogeneous dispersion of carbon nanotube in the polymer matrix at the microscale. Electrical conductivity measurements demonstrated an increase from 0.02 to 0.11 mS cm-1 with infused MWCNT. The MWCNT-infused hydrogels demonstrated a 400% increase in deswelling capabilities during an applied electrical stimulus compared to a noninfused hydrogel. In conclusion, infusing the MWCNT into the hydrogel increased its electrical conductivity, which allows the hydrogel to deswell more rapidly with an applied electrical bias without compromising its mechanical or swelling properties. [ABSTRACT FROM AUTHOR]

ABSTRACT Stimuli-responsive hydrogels are continuing to increase in demand in biomedical applications. Occluding a blood vessel is one possible application which is ideal for a hydrogel because of their ability to expand in a fluid environment. However, typically stimuli-responsive hydrogels focus on bending instead of radial uniform expansion, which is required for an occlusion application. This article focuses on using an interdigitated electrode device to stimulate an electro-responsive hydrogel in order to demonstrate a uniform swelling/deswelling of the hydrogel. A Pluronic-bismethacrylate (PF127-BMA) hydrogel modified with hydrolyzed methacrylic acid, in order to make it electrically responsive, is used in this article. An interdigitated electrode device was manufactured containing Platinum electrodes. The results in this paper show that the electrically biased hydrogels deswelled 230% more than the non-biased samples on average. The hydrogels deswelled uniformly and showed no visual deformations due to the electrical bias. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1523-1528 [ABSTRACT FROM AUTHOR]