Imaging Contrast and Biomechanics using Optical Coherence Tomography to Sense Superparamagnetic Iron Oxide Labeled Platelets

Abstract

Optical coherence tomography (OCT) provides 3D tissue imaging by contrasting light backscattering. OCT also senses nanoscale motions from optical phase shifts. We employ temporally modulated magnetic field gradients to mechanically displace superparamagnetic iron oxide nanoparticles (SPIOs). By locking in to the modulation frequency, SPIOs are contrasted in OCT, dubbed magnetomotive OCT (MMOCT).Rehydrated lyophilized human platelets (“RL platelets”), are chemically stabilized infusion hemostatic agents retaining viability. We investigate similar dried platelets with intracellular SPIOs (“SPIO platelets”) as imaging therapeutics. SPIOs are uptaken into the surface connected open canalicular system of platelets where they form clusters. Platelets are then stabilized and dried with the same methods as RL platelets. These SPIO platelets retain the primary hemostatic functions of RL and fresh platelets.We found that MMOCT provides highly specific contrast to SPIO platelets at 1.5e6/μL in 1% agarose scaffolding (see figure). Furthermore, by sweeping the modulation frequency, a mechanical frequency spectrum is obtained, and resonance peaks are associated with the sample elasticity. This has potential for imaging sites of vascular damage and monitoring the local mechanical microenvironment to provide more detailed information about vascular pathologies.View Large Image | View Hi-Res Image | Download PowerPoint Slide