Synthetic Antiferromagnetic Gold Nanoparticles as Bimodal Contrast Agents in MRI and CT-An Experimental In Vitro and In Vivo Study.

The use of multimodal contrast agents can potentially overcome the intrinsic limitations of individual imaging methods. We have validated synthetic antiferromagnetic nanoparticles (SAF-NPs) as bimodal contrast agents for in vitro cell labeling and in vivo cell tracking using magnetic resonance imaging (MRI) and computed tomography (CT). SAF-NP-labeled cells showed high contrast in MRI phantom studies (r2* = 712 s-1 mM-1), while pelleted cells showed clear contrast enhancement in CT. After intravenous SAF-NP injection, nanoparticles accumulated in the liver and spleen, as visualized in vivo by significant MRI contrast enhancement. Intravenous injection of SAF-NP-labeled cells resulted in cell accumulation in the lungs, which was clearly detectable by using CT but not by using MRI. SAF-NPs proved to be very efficient cell labeling agents for complementary MRI- and CT-based cell tracking. Bimodal monitoring of SAF-NP labeled cells is in particular of interest for applications where the applied imaging methods are not able to visualize the particles and/or cells in all organs.

Full-wafer in-situ fabrication and packaging of microfluidic flow cytometer with photo-patternable adhesive polymers.

Integration of microelectronics with microfluidics enables sophisticated lab-on-a-chip devices for sensing and actuation. In this paper, we investigate a novel method for in-situ microfluidics fabrication and packaging on wafer level. Two novel photo-patternable adhesive polymers were tested and compared, PA-S500H and DXL-009. The microfluidics fabrication method employs photo lithographical patterning of spin coated polymer films of PA or DXL and direct bonding of formed microfluidics to a top glass cover using die-to-wafer level bonding. These new adhesive materials remove the need for additional gluing layers. With this approach, we fabricated disposable microfluidic flow cytometers and evaluated the performance of those materials in the context of this application. DXL-009 exhibits lower autofluorescence compared to PA-S500H which improves detection sensitivity of fluorescently stained cells. Results obtained from the cytotoxicity test reveals that both materials are biocompatible. The functionality of these materials was demonstrated by detection of immunostained monocytes in microfluidic flow cytometers. The flexible, fully CMOS compatible fabrication process of these photo-patternable adhesive materials will simplify prototyping and mass manufacturing of sophisticated microfluidic devices with integrated microelectronics.

Synthetic antiferromagnetic nanoparticles as potential contrast agents in MRI.

We present the top-down synthesis of a novel type of MRI T2 contrast agent with great control over size and shape using a colloidal lithography technique. The resulting synthetic antiferromagnetic nanoparticles (SAF-NPs) yield improved relaxivities compared to superparamagnetic iron oxide alternatives (SPIONs). For T2 weighted imaging, the outer sphere relaxation theory has shown that the sensitivity of a T2 contrast agent is dependent on the particle size with an optimal size that exceeds the superparamagnetic limit of SPIONs. With the use of the interlayer exchange coupling effect, the SAF-NPs presented here do not suffer from this limit. Adjusting the outer sphere relaxation theory for spherical particles to SAF-NPs, we show both theoretically and experimentally that the SAF-NP size can be optimized to reach the r2 maximum. With measured r2 values up to 355 s(-1) mM(-1), our SAF-NPs show better performance than commercial alternatives and are competitive with the state-of-the-art. This performance is confirmed in an in vitro MRI study on SKOV3 cells.