@article {65653, title = {Multifield and inverse-contrast switching of magnetocaloric high contrast ratio MRI labels.}, journal = {Magnetic Resonance in Medicine}, volume = {85}, year = {2020}, month = {2020 Jul 07}, pages = {506-17}, abstract = {

PURPOSE: Demonstrating multifield and inverse contrast switching of magnetocaloric high contrast ratio MRI labels that either have increasing or decreasing moment versus temperature slopes depending on the material at physiological temperatures and different MRI magnetic field strengths.

METHODS: Two iron-rhodium samples of different purity (99\% and 99.9\%) and a lanthanum-iron-silicon sample were obtained from commercial vendors. Temperature and magnetic field-dependent magnetic moment measurements of the samples were performed on a vibrating sample magnetometer. Temperature-dependent MRI of different iron-rhodium and lanthanum-iron-silicon samples were performed on 3 different MRI scanners at 1 Tesla (T), 4.7T, and 7T.

RESULTS: Sharp, first-order magnetic phase transition of each iron-rhodium sample at a physiologically relevant temperature (~37{\textdegree}C) but at different MRI magnetic fields (1T, 4.7T, and 7T, depending on the sample) showed clear image contrast changes in temperature-dependent MRI. Iron-rhodium and lanthanum-iron-silicon samples with sharp, first-order magnetic phase transitions at the same MRI field of 1T and physiological temperature of 37{\textdegree}C, but with positive and negative slope of magnetization versus temperature, respectively, showed clear inverse contrast image changes. Temperature-dependent MRI on individual microparticle samples of lanthanum-iron-silicon also showed sharp image contrast changes.

CONCLUSION: Magnetocaloric materials of different purity and composition were demonstrated to act as diverse high contrast ratio switchable MRI contrast agents. Thus, we show that a range of magnetocaloric materials can be optimized for unique image contrast response under MRI-appropriate conditions at physiological temperatures and be controllably switched in situ.

}, issn = {1522-2594}, doi = {10.1002/mrm.28400}, author = {Barbic, Mladen and Dodd, Stephen J and ElBidweihy, Hatem and Dilley, Neil R and Marcheschi, Barbara and Huston, Alan L and Morris, H Douglas and Koretsky, Alan P} } @article {49150, title = {Evaluating the potential of using quantum dots for monitoring electrical signals in neurons.}, journal = {Nature Nanotechnology}, volume = {13}, year = {2018}, month = {2018 Apr}, pages = {278-288}, abstract = {

Success in the projects aimed at providing an advanced understanding of the brain is directly predicated on making critical advances in nanotechnology. This Perspective addresses the unique interface of neuroscience and nanomaterials by considering the foundational problem of sensing neuron membrane voltage and offers a potential solution that may be facilitated by a prototypical nanomaterial. Despite substantial improvements, the visualization of instantaneous voltage changes within individual neurons, whether in cell culture or in vivo, at both the single-cell and network level at high speed remains complex and problematic. The unique properties of semiconductor quantum dots (QDs) have made them powerful fluorophores for bioimaging. What is not widely appreciated, however, is that QD photoluminescence is exquisitely sensitive to proximal electric fields. This property should be suitable for sensing voltage changes that occur in the active neuronal membrane. Here, we examine the potential role of QDs in addressing the important challenge of real-time optical voltage imaging.

}, issn = {1748-3395}, doi = {10.1038/s41565-018-0107-1}, author = {Efros, Alexander L and Delehanty, James B and Huston, Alan L and Medintz, Igor L and Barbic, Mladen and Harris, Timothy D} } @article {46744, title = {Visualization and neuronal cell targeting during electrophysiological recordings facilitated by quantum dots.}, journal = {Proceedings of SPIE}, volume = {9305}, year = {2015}, month = {2015 Mar 10}, pages = {9305Y}, abstract = {

The simultaneous visualization, identification and targeting of neurons during patch clamp-mediated electrophysiological recordings is a basic technique in neuroscience, yet it is often complicated by the inability to visualize the pipette tip, particularly in deep brain tissue. Here we demonstrate a novel approach in which fluorescent quantum dot probes are used to coat pipettes prior to their use. The strong two-photon absorption cross sections of the quantum dots afford robust contrast at significantly deeper penetration depths than current methods allow. We demonstrate the utility of this technique in multiple recording formats both in vitro and in vivo where imaging of the pipettes is achieved at remarkable depths (up to 800 microns). Notably, minimal perturbation of cellular physiology is observed over the hours-long time course of neuronal recordings. We discuss our results within the context of the role that quantum dot nanoprobes may play in understanding neuronal cell physiology.

}, doi = {10.1117/12.2076934}, author = {Field, Lauren D and Andrasfalvy, Bertalan K and Gali{\~n}anes, Gregorio L and Huber, Daniel and Barbic, Mladen and Macklin, John J and Susumu, Kimihiro and Delehanty, James B and Huston, Alan L and Makara, Judit K and Medintz, Igor L} } @article {45812, title = {Quantum dot-based multiphoton fluorescent pipettes for targeted neuronal electrophysiology.}, journal = {Nature Methods}, volume = {11}, year = {2014}, month = {2014 Dec}, pages = {1237-41}, abstract = {

Targeting visually identified neurons for electrophysiological recording is a fundamental neuroscience technique; however, its potential is hampered by poor visualization of pipette tips in deep brain tissue. We describe quantum dot-coated glass pipettes that provide strong two-photon contrast at deeper penetration depths than those achievable with current methods. We demonstrated the pipettes{\textquoteright} utility in targeted patch-clamp recording experiments and single-cell electroporation of identified rat and mouse neurons in vitro and in vivo.

}, issn = {1548-7105}, doi = {10.1038/nmeth.3146}, author = {Andrasfalvy, Bertalan K and Gali{\~n}anes, Gregorio L and Huber, Daniel and Barbic, Mladen and Macklin, John J and Susumu, Kimihiro and Delehanty, James B and Huston, Alan L and Makara, Judit K and Medintz, Igor L} }