- 710 N. Pleasant St, 1302-1314 LGRT
University of Massachusetts Amherst
Amherst, MA 01003 - +1-413-545-4865
- University of Massachusetts Amherst, Chemistry, Post-DocUniversity of Texas at Arlington, Material Science and Engineering, Graduate Studentadd
- Engineering, Materials Engineering, Physics, Condensed Matter Physics, Materials Science, Chemistry, and 15 moreInorganic Chemistry, Physical Chemistry, Particle Physics, Green Chemistry, Nanomaterials Characterization, Electronic Materials, Synthesis of nanoparticles, Shape and Control of Metallic Nanoparticles, Magnetic nanoparticles, L10 FePt, Recording Media, FePt Nanoparticles, Nanoscience, Nanotechnology, and FePt nanorodsedit
- More than nine years of academic research experience in synthesis, characterization, and processing of magnetic and s... moreMore than nine years of academic research experience in synthesis, characterization, and processing of magnetic and semiconducting nanomaterials and nanocomposites.
Two years of postdoctoral research experience at University of Massachusetts Amherst.
Two years of industrial experience at Texas Instruments Inc. and Nanda Technocare Pvt. Ltd.
26 research papers in international peer reviewed journals (9 as a first author), 431 citations and h-index equal to 12.
Presenter at 11 international conferences.
Reviewer of 2 international peer-reviewed journals (Journal of Materials Chemistry and Langmuir).edit
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The effect of isolation on the phase transition temperature of FePt nanoparticles has been studied systematically by thermal, magnetic and structural characterizations and analyses. Isolated monodisperse L10 FePt nanoparticles embedded in... more
The effect of isolation on the phase transition temperature of FePt nanoparticles has been studied systematically by thermal, magnetic and structural characterizations and analyses. Isolated monodisperse L10 FePt nanoparticles embedded in carbon matrix were obtained by adding enough surfactants after chemical synthesis and by post-annealing during which the surfactant decomposed into carbon. It was found that the Al to L10
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IntroductionAmyloid‐beta oligomers (AβOs) accumulate in Alzheimer's disease and may instigate neuronal pathology and cognitive impairment. We examined the ability of a new probe for molecular magnetic resonance imaging (MRI) to detect... more
IntroductionAmyloid‐beta oligomers (AβOs) accumulate in Alzheimer's disease and may instigate neuronal pathology and cognitive impairment. We examined the ability of a new probe for molecular magnetic resonance imaging (MRI) to detect AβOs in vivo, and we tested the behavioral impact of AβOs injected in rabbits, a species with an amino acid sequence that is nearly identical to the human sequence.MethodsIntracerebroventricular (ICV) injection with stabilized AβOs was performed. Rabbits were probed for AβO accumulation using ACUMNS (an AβO‐selective antibody [ACU193] coupled to magnetic nanostructures). Immunohistochemistry was used to verify AβO presence. Cognitive impairment was evaluated using object location and object recognition memory tests and trace eyeblink conditioning.ResultsAβOs in the entorhinal cortex of ICV‐injected animals were detected by MRI and confirmed by immunohistochemistry. Injections of AβOs also impaired hippocampal‐dependent, but not hippocampal‐independ...
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Imaging of immune cells has wide implications in understanding disease progression and staging. While optical imaging is limited in penetration depth due to light properties, magnetic resonance (MR) imaging provides a more powerful tool... more
Imaging of immune cells has wide implications in understanding disease progression and staging. While optical imaging is limited in penetration depth due to light properties, magnetic resonance (MR) imaging provides a more powerful tool for the imaging of deep tissues where immune cells reside. Due to poor MR signal to noise ratio, tracking of such cells typically requires contrast agents. This report presents an in-depth physical characterization and application of archaeal magnetoferritin for MR imaging of macrophages - an important component of the innate immune system that is the first line of defense and first responder in acute inflammation. Magnetoferritin is synthesized by loading iron in apoferritin in anaerobic condition at 65 °C. The loading method results in one order of magnitude enhancement of r1 and r2 relaxivities compared to standard ferritin synthesized by aerobic loading of iron at room temperature. Detailed characterizations of the magnetoferritin revealed a crystalline core structure that is distinct from previously reported ones indicating magnetite form. The magnetite core is more stable in the presence of reducing agents and has higher peroxidase-like activities compared to the core in standard loading. Co-incubation of macrophage cells with magnetoferritin in-vitro shows significantly higher enhancement in T2-MRI contrast of the immune cells compared to standard ferritin.
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With a significant proportion of the global population growing older (>60 years), the low success rates of current diagnoses for early neurodegeneration signs are disappointing. Early detection of Alzheimer's disease (AD) can... more
With a significant proportion of the global population growing older (>60 years), the low success rates of current diagnoses for early neurodegeneration signs are disappointing. Early detection of Alzheimer's disease (AD) can improve acclimatization and quality of life for patients in their later years. Endogenous proteins, such as the most abundant secreted protein in cerebrospinal fluid, lipocalin‐type prostaglandin d synthase (L‐PGDS), can bind the early toxic oligomers of amyloid β (Aβ) peptides implicated in AD and prevent their aggregation. Herein, the utility of L‐PGDS for detection of amyloids is demonstrated. L‐PGDS is conjugated with different iron‐oxide magnetic nanoparticles for contrast‐enhanced visualization using magnetic resonance imaging (MRI). These conjugates inhibit amyloid aggregation in vitro and improve viability in neuronal cells incubated with amyloid fibrils, showing a potential neuroprotective function. L‐PGDS‐ferritin conjugates, when administered ...
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Improvements have been made in the diagnosis of Alzheimer’s disease (AD), manifesting mostly in the development of in vivo imaging methods that allow for the detection of pathological changes in AD by MRI and PET scans. Many of these... more
Improvements have been made in the diagnosis of Alzheimer’s disease (AD), manifesting mostly in the development of in vivo imaging methods that allow for the detection of pathological changes in AD by MRI and PET scans. Many of these imaging methods, however, use agents that probe amyloid fibrils and plaques - species that do not correlate well with disease progression and are not present at the earliest stages of the disease. Amyloid β oligomers (AβOs), rather, are now widely accepted as the Aβ species most germane to AD onset and progression. Here we report evidence further supporting the role of AβOs as pathological instigators of AD and introduce promising anti-AβO diagnostic probes capable of distinguishing the 5xFAD mouse model from wild type mice by PET and MRI. In a developmental study, Aβ oligomers in 5xFAD mice were found to appear at 3 months of age, just prior to the onset of memory dysfunction, and spread as memory worsened. The increase of AβOs is prominent in the subi...
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Endogenous brain proteins can recognize the toxic oligomers of amyloid-β (Aβ) peptides implicated in Alzheimer’s disease (AD) and interact with them to prevent their aggregation. Lipocalin-type Prostaglandin D Synthase (L-PGDS) is a major... more
Endogenous brain proteins can recognize the toxic oligomers of amyloid-β (Aβ) peptides implicated in Alzheimer’s disease (AD) and interact with them to prevent their aggregation. Lipocalin-type Prostaglandin D Synthase (L-PGDS) is a major Aβ-chaperone protein in the human cerebrospinal fluid. Here we demonstrate that L-PGDS detects amyloids in diseased mouse brain. Conjugation of L-PGDS with magnetic nanoparticles enhanced the contrast for magnetic resonance imaging. We conjugated the L-PGDS protein with ferritin nanocages to detect amyloids in the AD mouse model brain. We show here that the conjugates administered through intraventricular injections co-localize with amyloids in the mouse brain. These conjugates can target the brain regions through non-invasive intranasal administration, as shown in healthy mice. These conjugates can inhibit the aggregation of amyloids in vitro and show potential neuroprotective function by breaking down the mature amyloid fibrils.
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Here we report design of a smart nanoconstruct that can be used as a multimodal theranostic platform for imaging and therapy applications. Decorated with two sizes of magnetic nanostructures (MNS) on thermoresponsive nanosized hydrogel... more
Here we report design of a smart nanoconstruct that can be used as a multimodal theranostic platform for imaging and therapy applications. Decorated with two sizes of magnetic nanostructures (MNS) on thermoresponsive nanosized hydrogel (NG), the NG-MNS nanoconstruct shows dual-mode contrast enhancement ability in MRI and thermo-chemo therapeutic ability under an RF field. Because of the unique design where all MNS are at the exterior of the nanoconstruct, no compromise in the physical properties of MNS and their effect on contrast enhancement and thermal activation has been observed. In a series of in vitro analyses in human breast adenocarcinoma (MDA-MB-231) cells, we validate that NG-MNS show dual-mode MR imaging capability with a higher signal/noise ratio than in clinically approved dual-mode contrast agents as well as enhanced therapeutic efficacy compared to previously reported hydrogel-based nanocarriers and free drug systems.
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A novel magnetic nanostructures (MNS) stabilized lipid nanoconstruct is reported that shows superior structural stability and theranostic functionality than conventional lipid based nanocarriers.
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Exchange coupling between hard and soft magnetic materials at the nanoscale exhibit novel or improved physical properties for energy and data storage applications. Recently, exchange coupling has also been explored in core/shell magnetic... more
Exchange coupling between hard and soft magnetic materials at the nanoscale exhibit novel or improved physical properties for energy and data storage applications. Recently, exchange coupling has also been explored in core/shell magnetic nanostructures (MNS) composed of hard and soft magnetic spinel ferrites but applications has been limited in biomedicine due to the presence of 'toxic' cobalt based ferrites as hard magnetic component. We report core/shell MNS where both core and shell components are soft magnetic ferrites (Fe3O4, MnFe2O4, and Zn0.2Mn0.8Fe2O4) and show that exchange coupling still exist due to the difference in their anisotropy. The physical properties (saturation magnetization, susceptibility, anisotropy, r2 relaxivity, and specific absorption rate) of core/shell MNS is compared with same size single phase counterparts that excludes any size dependent effect and gives the direct effect of exchange coupling. After optimization of core and shell components an...
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The intrinsic coagulation activity of silica nanoparticles strongly depends on their surface curvature.
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The effect of isolation on the phase transition temperature of FePt nanoparticles has been studied systematically by thermal, magnetic and structural characterizations and analyses. Isolated monodisperse L10 FePt nanoparticles embedded in... more
The effect of isolation on the phase transition temperature of FePt nanoparticles has been studied systematically by thermal, magnetic and structural characterizations and analyses. Isolated monodisperse L10 FePt nanoparticles embedded in carbon matrix were obtained by adding enough surfactants after chemical synthesis and by post-annealing during which the surfactant decomposed into carbon. It was found that the Al to L10
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Research Interests: Engineering, Chemical Engineering, Materials Science, Sintering, Nanoparticle, and 11 moreHeat Treatment, Magnetic nanoparticles, Physical sciences, Phase transition, Phase Transformation, Magnetic Anisotropy, Magnetic Nanoparticles, Ferromagnetism, Chemical Synthesis, Coercivity, and permanent magnet
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Alignment of ferromagnetic nano-sized crystals is essential for advanced applications like nanocomposite magnets with high energy density and magnetic recording media with high data storage density. Recently we successfully prepared... more
Alignment of ferromagnetic nano-sized crystals is essential for advanced applications like nanocomposite magnets with high energy density and magnetic recording media with high data storage density. Recently we successfully prepared monodisperse ferromagnetic FePt nanoparticles with uniform particle size and controllable shape.[1] The particles have strong magnetic anisotropy and coercivity (up to 30 KOe). However the very small particle size (4 to 8 nm) makes the alignment difficult. Application of high magnetic fields is necessary. We ...
ABSTRACT Bimagnetic FePt/CoFe 2 O 4 nanoparticles having a bricklike morphology were synthesized by growing a soft magnetic CoFe 2 O 4 phase on FePt cubic nanoparticle seeds. The size of the soft phase could be controlled by tuning the... more
ABSTRACT Bimagnetic FePt/CoFe 2 O 4 nanoparticles having a bricklike morphology were synthesized by growing a soft magnetic CoFe 2 O 4 phase on FePt cubic nanoparticle seeds. The size of the soft phase could be controlled by tuning the material ratio of the FePt seeds to the CoFe 2 O 4 component. To obtain magnetic hardening, the as-synthesized bricklike nanoparticles were annealed at elevated temperatures under a reductive atmosphere to convert the disordered face-centered cubic FePt phase into the ordered L1 0 phase having high magnetic anisotropy. When the particles were annealed, a gradual change was observed in morphology from bricklike particles to spherical polycrystalline nanocomposite particles because of diffusion. Meanwhile, the magnetic energy density was enhanced as a result of the exchange coupling between the hard and soft phases. The enhancement was dependent on the ratio of the volumes of the soft phase and the hard phase.
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Magnetic nanostructures (MNS) have emerged as promising functional probes for simultaneous diagnostics and therapeutics (theranostic) applications due to their ability to enhance localized contrast in magnetic resonance imaging (MRI) and... more
Magnetic nanostructures (MNS) have emerged as promising functional probes for simultaneous diagnostics and therapeutics (theranostic) applications due to their ability to enhance localized contrast in magnetic resonance imaging (MRI) and heat under external radio frequency (RF) field, respectively. We show that the "theranostic" potential of the MNS can be significantly enhanced by tuning their core composition and architecture of surface coating. Metal ferrite (e.g., MFe2O4) nanoparticles of ∼8 nm size and nitrodopamine conjugated polyethylene glycol (NDOPA-PEG) were used as the core and surface coating of the MNS, respectively. The composition was controlled by tuning the stoichiometry of MFe2O4 nanoparticles (M = Fe, Mn, Zn, ZnxMn1-x) while the architecture of surface coating was tuned by changing the molecular weight of PEG, such that larger weight is expected to result in longer length extended away from the MNS surface. Our results suggest that both core as well as s...
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Despite the complexities of cancer, remarkable diagnostic and therapeutic advances have been made during the past decade, which include improved genetic, molecular, and nanoscale understanding of the disease. Physical science and... more
Despite the complexities of cancer, remarkable diagnostic and therapeutic advances have been made during the past decade, which include improved genetic, molecular, and nanoscale understanding of the disease. Physical science and engineering, and nanotechnology in particular, have contributed to these developments through out-of-the-box ideas and initiatives from perspectives that are far removed from classical biological and medicinal aspects of cancer. Nanostructures, in particular, are being effectively utilized in sensing/diagnostics of cancer while nanoscale carriers are able to deliver therapeutic cargo for timed and controlled release at localized tumor sites. Magnetic nanostructures (MNS) have especially attracted considerable attention of researchers to address cancer diagnostics and therapy. A significant part of the promise of MNS lies in their potential for "theranostic" applications, wherein diagnostics makes use of the enhanced localized contrast in magnetic resonance imaging (MRI) while therapy leverages the ability of MNS to heat under external radio frequency (RF) field for thermal therapy or use of thermal activation for release of therapy cargo. In this chapter, we report some of the key developments in recent years in regard to MNS as potential theranostic carriers. We describe that the r 2 relaxivity of MNS can be maximized by allowing water (proton) diffusion in the vicinity of MNS by polyethylene glycol (PEG) anchoring, which also facilitates excellent fluidic stability in various media and extended in vivo circulation while maintaining high r 2 values needed for T 2-weighted MRI contrast. Further, the specific absorption rate (SAR) required for thermal activation of MNS can be tailored by controlling composition and size of MNS. Together, emerging MNS show considerable promise to realize theranostic potential. We discuss that properly functionalized MNS can be designed to provide remarkable in vivo stability and accompanying pharmacokinetics exhibit organ localization that can be tailored for specific applications. In this context, even iron-based MNS show extended circulation as well as diverse organ accumulation beyond liver, which otherwise renders MNS potentially toxic to liver function. We believe that MNS, including those based on iron oxides, have entered a renaissance era where intelligent synthesis, functionalization, stabilization, and targeting provide ample evidence for applications in localized cancer theranostics.
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Here we demonstrate patterning of protein/quantum dot hybrid bionanostructures via electrostatic assembly of engineered negatively charged fluorescent protein with positively charged CdSe/ZnS QD patterns formed through e-beam lithography... more
Here we demonstrate patterning of protein/quantum dot hybrid bionanostructures via electrostatic assembly of engineered negatively charged fluorescent protein with positively charged CdSe/ZnS QD patterns formed through e-beam lithography and post-patterning modification with cationic ligands.
Organization of the nanoparticles (NPs) into morphologically 10 controlled and organised structures is a central issue for bottom-up fabrication of functional devices in optoelectronics, sensing, catalysis and medicine. 1, 2 Directed... more
Organization of the nanoparticles (NPs) into morphologically 10 controlled and organised structures is a central issue for bottom-up fabrication of functional devices in optoelectronics, sensing, catalysis and medicine. 1, 2 Directed host-guest assembly of NPs into polymer matrices3, 4 is an effective route to form structured NP assemblies with advantageous optical, 5 15 electronic, 6 magnetic, 7 and mechanical properties. 8 Polymer mediated self-assembly of NPs yields stable nanocomposites and their properties can be tuned by ...
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ABSTRACT FexPtyAu100−x−y nanoparticles of size 3.5 nm were prepared by polyol reduction of platinum acetylacetonate and gold acetate and the thermal decomposition of iron pentacarbonyl. The as-synthesized nanoparticles with disordered fcc... more
ABSTRACT FexPtyAu100−x−y nanoparticles of size 3.5 nm were prepared by polyol reduction of platinum acetylacetonate and gold acetate and the thermal decomposition of iron pentacarbonyl. The as-synthesized nanoparticles with disordered fcc structure were then heat treated to transform to the L10 structure with high magnetocrystalline anisotropy. By tuning the stoichiometry of the FexPtyAu100−x−y nanoparticles, the phase transition temperature was reduced by more than 200 °C. After the annealing 500 °C, for instance, the highest coercivity of 18 kOe was obtained from the Fe51Pt36Au13 nanoparticles which is substantially higher compared to 2 kOe for Fe51Pt49 nanoparticles annealed at the same temperature. In addition to the high coercivity, the saturation magnetization value obtained from Fe51Pt36Au13 nanoparticles was 47 emu/g which is similar to that for the Fe51Pt49 nanoparticles, indicating that there is no trade-off between the coercivity and the saturation magnetization upon Au doping.
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Flavins feature multiple attributes that explain their widespread occurrence in nature, including photostability, reversible electrochemistry, and especially the tunability of their optical, electronic, and redox properties by... more
Flavins feature multiple attributes that explain their widespread occurrence in nature, including photostability, reversible electrochemistry, and especially the tunability of their optical, electronic, and redox properties by supramolecular interactions and modification of their chemical structure. Flavins are important redox cofactors for enzymatic catalysis and are central to a wide variety of processes, including biosynthesis, electron transport, photosynthesis, and DNA repair. The wide range of processes catalyzed by flavins makes them promising leads for synthetic catalysts. Their properties are also relevant to organic electronic and optoelectronic devices, where they have the potential to serve as photoactive electron carriers, a very uncommon property in current photovoltaic systems. In flavoenzymes, the flavin cofactor binds to the active site of the apoenzyme through noncovalent interactions. These interactions regulate cofactor recognition and tune the redox behavior of the flavin cofactor. In this Account, we describe the creation of host-guest systems based on small molecule, polymer, and nanoparticle scaffolds that explore the role of aromatic stacking on the redox properties of the flavin and provide insight into flavoenzyme function. We also describe the creation of synthetic flavin-based interlocked structures featuring aromatic stacking interactions, along with the use of aromatic stacking to direct self-assembly of flavin-based materials. The interplay between redox events and aromatic stacking interactions seen in these synthetic models is important for fundamental understanding of biological systems including the flavoenzymes. The precise control of aromatic interactions and binding of flavins not only underpins their biological activity but gives them the potential to be developed into novel organic optoelectronic materials based on tuned synthetic flavin-receptor assemblies. In a broader context, the redox properties of the flavin provide a very concise tool for looking at the role of electronics in aromatic stacking, an issue of general importance in biological and supramolecular chemistry.
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Abstract Ultrafine FePt nanoparticles have been synthesized via a novel chemical solution synthesis route. Without using a reducing agent, the stoichiometric FePt nanoparticles were produced by the decomposition of iron acetylacetonate... more
Abstract Ultrafine FePt nanoparticles have been synthesized via a novel chemical solution synthesis route. Without using a reducing agent, the stoichiometric FePt nanoparticles were produced by the decomposition of iron acetylacetonate and platinum acetylacetonate in octyl ether in the presence of oleic acid and oleyl amine as the surfactants. The particle size was found to be around 2 nm with a narrow size distribution. The particles were then deposited on substrates and heat treated afterwards.
Abstract: Fe x Pt y Au 100− x− y nanoparticles of size 3.5 nm were prepared by polyol reduction of platinum acetylacetonate and gold acetate and the thermal decomposition of iron pentacarbonyl. The as-synthesized nanoparticles with... more
Abstract: Fe x Pt y Au 100− x− y nanoparticles of size 3.5 nm were prepared by polyol reduction of platinum acetylacetonate and gold acetate and the thermal decomposition of iron pentacarbonyl. The as-synthesized nanoparticles with disordered fcc structure were then heat treated to transform to the L1 0 structure with high magnetocrystalline anisotropy. By tuning the stoichiometry of the Fe x Pt y Au 100− x− y nanoparticles, the phase transition temperature was reduced by more than 200 C.
Alignment of ferromagnetic nano-sized crystals is essential for advanced applications like nanocomposite magnets with high energy density and magnetic recording media with high data storage density. Recently we successfully prepared... more
Alignment of ferromagnetic nano-sized crystals is essential for advanced applications like nanocomposite magnets with high energy density and magnetic recording media with high data storage density. Recently we successfully prepared monodisperse ferromagnetic FePt nanoparticles with uniform particle size and controllable shape.[1] The particles have strong magnetic anisotropy and coercivity (up to 30 KOe). However the very small particle size (4 to 8 nm) makes the alignment difficult. Application of high magnetic fields is necessary.
Abstract To transfer face-centered cubic (fcc) FePt nanoparticles to face-centered tetragonal (fct) structure with high magnetic anisotropy, heat treatments are necessary. The heat treatments, however, often lead to agglomeration and... more
Abstract To transfer face-centered cubic (fcc) FePt nanoparticles to face-centered tetragonal (fct) structure with high magnetic anisotropy, heat treatments are necessary. The heat treatments, however, often lead to agglomeration and sintering of the nanoparticles. To prevent the particles from sintering, a new method, the salt-matrix annealing, has been adopted in our experiments recently. The fcc nanoparticles produced by chemical synthesis were mixed with NaCl or other salt powders.