Hrushikesh M Joshi

Publications (12) View all

• Article: Hybrid magnetic nanostructures (MNS) for magnetic resonance imaging applications.

  Mrinmoy De, Stanley S Chou, Hrushikesh M Joshi, Vinayak P Dravid
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  ABSTRACT: The development of MRI contrast agents has experienced its version of the gilded age over the past decade, thanks largely to the rapid advances in nanotechnology. In addition to progress in single mode contrast agents, which ushered in unprecedented R(1) or R(2) sensitivities, there has also been a boon in the development of agents covering more than one mode of detection. These include T(1)-PET, T(2)-PET T(1)-optical, T(2)-optical, T(1)-T(2) agents and many others. In this review, we describe four areas which we feel have experienced particular growth due to nanotechnology, specifically T(2) magnetic nanostructure development, T(1)/T(2)-optical dual mode agents, and most recently the T(1)-T(2) hybrid imaging systems. In each of these systems, we describe applications including in vitro, in vivo usage and assay development. In all, while the benefits and drawbacks of most MRI contrast agents depend on the application at hand, the recent development in multimodal nanohybrids may curtail the shortcomings of single mode agents in diagnostic and clinical settings by synergistically incorporating functionality. It is hoped that as nanotechnology advances over the next decade, it will produce agents with increased diagnostics and assay relevant capabilities in streamlined packages that can meaningfully improve patient care and prognostics. In this review article, we focus on T(2) materials, its surface functionalization and coupling with optical and/or T(1) agents.
  Advanced drug delivery reviews 08/2011; 63(14-15):1282-99. · 11.96 Impact Factor
• Source

  Available from: neurobiology.northwestern.edu

  Article: Probing the Chemical Stability of Mixed Ferrites: Implications for MR Contrast Agent Design.

  Elise A Schultz-Sikma, Hrushikesh M Joshi, Qing Ma, Keith W Macrenaris, Amanda L Eckermann, Vinayak P Dravid, Thomas J Meade
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  ABSTRACT: Nanomaterials with mixed composition, in particular magnetic spinel ferrites, are emerging as efficient contrast agents for magnetic resonance imaging (MRI). Many factors, including size, composition, atomic structure, and surface properties are crucial in the design of such nanoparticle-based probes due to their influence on the magnetic properties. Silica-coated iron oxide (IO-SiO(2)) and cobalt ferrite (CoIO-SiO(2)) nanoparticles were synthesized using standard high temperature thermal decomposition and base-catalyzed water-in-oil microemulsion techniques. Under neutral aqueous conditions, it was found that 50-75% of the cobalt content in the CoIO-SiO(2) nanoparticles leached out of the core structure. Leaching caused a 7.2-fold increase in longitudinal relaxivity and an increase in the saturation magnetization from ~48 emu/g core to ~65 emu/g core. X-ray absorption fine structure studies confirmed that the atomic structure of the ferrite core was altered following leaching, while TEM and DLS confirmed that the morphology and size of the nanoparticle remained unchanged. The CoIO-SiO(2) nanoparticles converted from a partially inverted spinel cation arrangement (unleached state) to an inverse spinel arrangement (leached state). The control IO-SiO(2) nanoparticles remained stable with no change in structure and negligible changes in magnetic behavior. This detailed analysis highlights how important understanding the properties of nanomaterials is in the development of reliable agents for diagnostic and therapeutic applications.
  Chemistry of Materials 05/2011; 23(10):2657-2664. · 7.29 Impact Factor
• Source

  Available from: Allen Taflove

  Article: Quantification of nanoscale density fluctuations by electron microscopy: probing cellular alterations in early carcinogenesis.

  Prabhakar Pradhan, Dhwanil Damania, Hrushikesh M Joshi, Vladimir Turzhitsky, Hariharan Subramanian, Hemant K Roy, Allen Taflove, Vinayak P Dravid, Vadim Backman
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  ABSTRACT: Most cancers are curable if they are diagnosed and treated at an early stage. Recent studies suggest that nanoarchitectural changes occur within cells during early carcinogenesis and that such changes precede microscopically evident tissue alterations. It follows that the ability to comprehensively interrogate cell nanoarchitecture (e.g., macromolecular complexes, DNA, RNA, proteins and lipid membranes) could be critical to the diagnosis of early carcinogenesis. We present a study of the nanoscale mass-density fluctuations of biological tissues by quantifying their degree of disorder at the nanoscale. Transmission electron microscopy images of human tissues are used to construct corresponding effective disordered optical lattices. The properties of nanoscale disorder are then studied by statistical analysis of the inverse participation ratio (IPR) of the spatially localized eigenfunctions of these optical lattices at the nanoscale. Our results show an increase in the disorder of human colonic epithelial cells in subjects harboring early stages of colon neoplasia. Furthermore, our findings strongly suggest that increased nanoscale disorder correlates with the degree of tumorigenicity. Therefore, the IPR technique provides a practicable tool for the detection of nanoarchitectural alterations in the earliest stages of carcinogenesis. Potential applications of the technique for early cancer screening and detection are also discussed.
  Physical Biology 03/2011; 8(2):026012. · 2.60 Impact Factor
• Source

  Available from: Allen Taflove

  Article: Quantification of nanoscale density fluctuations using electron microscopy: Light-localization properties of biological cells.

  Prabhakar Pradhan, Dhwanil Damania, Hrushikesh M Joshi, Vladimir Turzhitsky, Hariharan Subramanian, Hemant K Roy, Allen Taflove, Vinayak P Dravid, Vadim Backman
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  ABSTRACT: We report a study of the nanoscale mass-density fluctuations of heterogeneous optical dielectric media, including nanomaterials and biological cells, by quantifying their nanoscale light-localization properties. Transmission electron microscope images of the media are used to construct corresponding effective disordered optical lattices. Light-localization properties are studied by the statistical analysis of the inverse participation ratio (IPR) of the localized eigenfunctions of these optical lattices at the nanoscale. We validated IPR analysis using nanomaterials as models of disordered systems fabricated from dielectric nanoparticles. As an example, we then applied such analysis to distinguish between cells with different degrees of aggressive malignancy.
  Applied Physics Letters 12/2010; 97(24):243704. · 3.84 Impact Factor
• Article: High-performance nanostructured MR contrast probes.

  Fengqin Hu, Hrushikesh M Joshi, Vinayak P Dravid, Thomas J Meade
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  ABSTRACT: Magnetic resonance imaging (MRI) has become a powerful technique in biological molecular imaging and clinical diagnosis. With the rapid progress in nanoscale science and technology, nanostructure-based MR contrast agents are undergoing rapid development. This is in part due to the tuneable magnetic and cellular uptake properties, large surface area for conjugation and favourable biodistribution. In this review, we describe our recent progress in the development of high-performance nanostructured MR contrast agents. Specifically, we report on Gd-enriched nanostructured probes that exhibit T(1) MR contrast and superparamagnetic Fe(3)O(4) and CoFe(2)O(4) nanostructures that display T(2) MR contrast enhancement. The effects of nanostructure size, shape, assembly and surface modification on relaxivity are described. The potential of these contrast agents for in vitro and in vivo MR imaging with respect to colloidal stability under physiological conditions, biocompatibility, and surface functionality are also evaluated.
  Nanoscale 10/2010; 2(10):1884-91. · 5.91 Impact Factor