Paras N. Prasad

Korea University, Sŏul, Seoul, South Korea

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Publications (595)2413.87 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Nanoparticles (NPs) with high drug loading and pH-responsivity were prepared by nanoprecipitation of a hydrophobic polymer-drug conjugate (PDC). The PDC, polylactide-graft-doxorubicin (PLA-g-DOX), was synthesized by azide-alkyne click reaction to transform acetylene-functionalized PLA into PLA-graft-aldehyde (PLA-g-ALD), followed by DOX conjugation to form acid-sensitive Schiff base linkage between drug moieties and polymer scaffold. The DOX loading amount in PLA-g-DOX PDC was determined to be 32 wt% by 1H NMR and UV-Vis spectroscopies. PLA-g-DOX PDC was further used to prepare NPs with precisely controlled drug loading by nanoprecipitation in the presence of a PEGylated surfactant. The effects of organic solvent, PLA-g-DOX PDC concentration and PLA-g-DOX/surfactant mass ratio on size and size distribution of NPs were systematically examined based on analysis by dynamic light scattering (DLS) and transmission electron microscopy (TEM). NPs prepared under the optimal conditions exhibited well-defined spherical morphology with volume-average hydrodynamic diameter (Dh) around 100 nm. Due to the Schiff base conjugation linkage in PLA-g-DOX PDC, acid-sensitive drug release behavior of the NPs was observed. In vitro studies against MCF-7 breast cancer cells showed that the NPs can be readily uptaken and result in enhanced therapeutic efficiency than DOX•HCl, indicating their promising potential applications as anti-cancer nanomedicines.
    Biomacromolecules 01/2014; · 5.79 Impact Factor
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    ABSTRACT: The luminescence efficiency of lanthanide-doped upconversion nanoparticles is of particular importance for their embodiment in biophotonic and photonic applications. Here, we show that the upconversion luminescence of typically used NaYF4:Yb3+30%/Tm3+0.5% nanoparticles can be enhanced by ~240 times through a hierarchical active core/active shell/inert shell (NaYF4:Yb3+30%/Tm3+0.5%)/NaYbF4/NaYF4 design, which involves the use of directed energy migration in the second active shell layer. The resulting active core/active shell/inert shell nanoparticles are determined to be about 11 times brighter than that of well-investigated (NaYF4:Yb3+30%/Tm3+0.5%)/NaYF4 active core/inert shell nanoparticles when excited at ~980 nm. The strategy for enhanced upconversion in Yb3+/Tm3+-codoped NaYF4 nanoparticles through directed energy migration might have implications for other types of lanthanide-doped upconversion nanoparticles.
    Nanomaterials. 01/2014; 4(1):55-68.
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    ABSTRACT: Having unique architectural features, cationic polymeric nanocapsules (NCs) with well-defined covalently stabilized biodegradable structures were generated as potentially universal and safe therapeutic nanocarriers. These NCs were synthesized from allyl-functionalized cationic polylactide (CPLA) by highly efficient UV-induced thiol-ene interfacial cross-linking in transparent miniemulsions. With tunable nanoscopic sizes, negligible cytotoxicity and remarkable degradability, they are able to encapsulate doxorubicin (Dox) with inner cavities and bind interleukin-8 (IL-8) small interfering RNA (siRNA) with cationic shells. The Dox-encapsulated NCs can effectively bypass the P-glycoprotein (Pgp)-mediated multidrug resistance of MCF7/ADR cancer cells, thereby resulting in increased intracellular drug concentration and reduced cell viability. In vitro studies also showed that the NCs loaded with Dox, IL-8 siRNA and both agents can be readily taken up by PC3 prostate cancer cells, resulting in a significant chemotherapeutic effect and/or IL-8 gene silencing.
    Nanoscale 12/2013; · 6.74 Impact Factor
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    ABSTRACT: Infectious diseases are a worldwide health concern. For some infections, a common feature is the intracellular residence of the pathogen and evasion of the host immune response. In the case of Tuberculosis (TB), Mycobacterium tuberculosis evades clearance within macrophages through suppression of intracellular reactive oxygen and nitrogen species (ROS/RNS) and pro-inflammatory cytokines. We propose new nanoparticle designs for infectious diseases, functionalized with ligands able to modulate the cellular immune response and concurrently deliver drug. We have designed 1,3-β-glucan functionalized chitosan shell, poly(lactide)co-glycolide core nanoparticles to stimulate ROS/RNS, pro-inflammatory cytokine secretion, and delivery of rifampicin inside human alveolar like macrophages (ALM). Nanoparticles significantly enhanced ALM secretion of IL-12p70 (2.9-fold), TNF-α (16-fold) and INF-γ (23-fold) compared to controls over 24h, and doubled ROS/RNS generation over 6h. Nanoparticles could deliver 4-fold greater rifampicin into ALM compared to rifampicin solution. These results provide proof-of-concept of multimodal nanoparticles and support their further development.
    Nanomedicine: nanotechnology, biology, and medicine 12/2013; · 6.93 Impact Factor
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    ABSTRACT: The design, synthesis, and supramolecular organization of a nanocomposite in which nanoscale excitonic interactions between quantum dots and the chiral polymer dramatically enhance the optical activity is reported. This material is highly suitable for application in the emerging field of chiral photonics.
    Advanced Materials 12/2013; · 15.41 Impact Factor
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    ABSTRACT: Intense ultraviolet upconversion emission has been observed in water-dispersed uniform rhombic nanodisks (side length of ∼14 nm and thickness of ∼2.5 nm) of YF3 co-doped with Yb(3+) sensitizer and Tm(3+) activator ions, when excited at ∼980 nm.
    Nanoscale 12/2013; · 6.74 Impact Factor
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    ABSTRACT: Development of long-term implantable luminescent biosensors for subcutaneous oxygen has proved challenging due to difficulties in immobilizing a biocompatible matrix that prevents sensor aggregation yet maintains sufficient concentration for transdermal optical detection. Here, Pd-porphyrins can be used as PEG cross-linkers to generate a polyamide hydrogel with extreme porphyrin density (≈5 × 10(-3) m). Dye aggregation is avoided due to the spatially constraining 3D mesh formed by the porphyrins themselves. The hydrogel exhibits oxygen-responsive phosphorescence and can be stably implanted subcutaneously in mice for weeks without degradation, bleaching, or host rejection. To further facilitate oxygen detection using steady-state techniques, an oxygen-non-responsive companion hydrogel is developed by blending copper and free base porphyrins to yield intensity-matched luminescence for ratiometric detection.
    Advanced Healthcare Materials 11/2013; 3(6).
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    ABSTRACT: Nanoscopic size, biodegradability and environmental responsivity are highly desired for drug delivery systems in order to achieve high precision and efficacy in cancer treatment without considerable side effects. In this project, nanoparticles with high drug loading and pH-responsivity were prepared by nanoprecipitation of hydrophobic polymer-drug conjugates. Polymer-drug conjugates, polylactide (PLA)-g-doxorubicin (DOX), were synthesized by click reaction to convert alkyne-functionalized PLA to benzyl aldehyde-functionalized PLA, followed by DOX conjugation to form acid-sensitive Schiff base linkage between drug moieties and polymer scaffold. The DOX loading amount in PLA-g-DOX was determined to be 30 wt% by 1H NMR and UV spectroscopies. PLA-g-DOX was further used to prepare nanoparticles with precisely controlled drug loading by nanoprecipitaiton in the presence of a PEGylated surfactant. The effects of organic solvent, PLA-g-DOX concentration and PLA-g-DOX/surfactant mass ratio on nanoparticle size and distribution were systematically examined based on DLS and TEM analysis. Nanoparticles prepared under the optimal conditions exhibited well-defined sphere morphology with average diameter around 100 nm. Due to the Schiff base conjugation linkage in PLA-g-DOX, the acid sensitive drug release behavior of the nanoparticles was observed. Cytotoxicity and cell internalization studies of the nanoparticles towards MCF-7 breast cancer cells indicated their promising potential applications as anti-cancer nanomedines.
    13 AIChE Annual Meeting; 11/2013
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    ABSTRACT: The tetrazole-based photoclick chemistry has provided a powerful tool to image proteins in live cells. To extend photoclick chemistry to living organisms with improved spatiotemporal control, here we report the design of naphthalene-based tetrazoles that can be efficiently activated by a 700 nm femtosecond pulsed laser. A water-soluble, cell-permeable naphthalene-based tetrazole was identified that reacts with acrylamide with the two-photon cross section of the cycloaddition reaction determined to be 3.8 GM. Furthermore, the use of this naphthalene-tetrazole for real-time, spatially controlled imaging of microtubules in live mammalian cells via the fluorogenic, two-photon triggered photoclick chemistry was demonstrated.
    Journal of the American Chemical Society 10/2013; · 11.44 Impact Factor
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    ABSTRACT: Bionanocombinatorics is an emerging field that aims to use combinations of positionally encoded biomolecules and nanostructures to create materials and devices with unique properties or functions. The full potential of this new paradigm could be accessed by exploiting specific noncovalent interactions between diverse palettes of biomolecules and inorganic nanostructures. Advancement of this paradigm requires peptide sequences with desired binding characteristics that can be rationally designed, based upon fundamental, molecular-level understanding of biomolecule-inorganic nanoparticle interactions. Here, we introduce an integrated method for building this understanding using experimental measurements and advanced molecular simulation of the binding of peptide sequences to gold surfaces. From this integrated approach, the importance of entropically driven binding is quantitatively demonstrated, and the first design rules for creating both enthalpically and entropically driven nanomaterial-binding peptide sequences are developed. The approach presented here for gold is now being expanded in our laboratories to a range of inorganic nanomaterials and represents a key step toward establishing a bionanocombinatorics assembly paradigm based on noncovalent peptide-materials recognition.
    ACS Nano 10/2013; · 12.03 Impact Factor
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    ABSTRACT: Upconversion nanoparticles (UCNPs) can convert tissue-penetrable nearinfrared light into UV emission, making them promising as transducers for photoactivation in biology. However, the choice of the UV emitting UCNPs is limited and their NIR-to-UV efficiency is low. G. Han and co-workers have addressed this issue by developing a family of CaF2 -coated UCNPs with tunable UV enhancement. As reported on page 3213, such design outperforms known optimal UCNPs and in situ realtime live-cell photoactivation is recorded for the first time with such nanoparticles. This result is a potential game changer in photoactivation in living systems and a new tool for other biophotonic applications.
    Small 10/2013; 9(19):3212. · 7.51 Impact Factor
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    ABSTRACT: Chiral photonics is an emerging field which deals with enantioselective light–matter interactions, offering numerous exciting applications. Two main approaches to enhancing enantioselective interactions are currently under extensive study: 1) structuring light itself, and 2) developing materials with gigantic optical activity. Both are required to realize the full potential of this emerging field. Here, the intensity-dependent optical activity of a chiral polyfluorene film that has been studied by using open- and closed-aperture z-scan techniques with ∼775 nm and ∼160 fs laser pulses is reported. For a film of ∼20 μm thickness, the measured two-photon absorption coefficients are 1.24 and 1.49 cm GW-1, respectively, and the nonlinear refractive indices are 8.74 × 10−5 and 1.38 × 10−4 cm2 GW-1 for right and left circularly polarized laser beams, respectively. The nonlinear optical activity of pure, undoped polyfluorene is the highest reported so far.
    Advanced Optical Materials. 10/2013; 1(10).
  • Synthetic Metals 10/2013; 182:22-27. · 2.22 Impact Factor
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    ABSTRACT: With the rapid development of bionanotechnology, there has been a growing interest recently in identifying the affinity classes of the inorganic materials binding peptide sequences. However, there are some distinct characteristics of inorganic materials binding sequence data that limit the performance of many widely-used classification methods. In this paper, we propose a novel framework to predict the affinity classes of peptide sequences with respect to an associated inorganic material. We first generate a large set of simulated peptide sequences based on our new amino acid transition matrix, and then the probability of test sequences belonging to a specific affinity class is calculated through solving an objective function. In addition, the objective function is solved through iterative propagation of probability estimates among sequences and sequence clusters. Experimental results on a real inorganic material binding sequence dataset show that the proposed framework is highly effective on identifying the affinity classes of inorganic material binding sequences.
    Proceedings of the International Conference on Bioinformatics, Computational Biology and Biomedical Informatics; 09/2013
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    ABSTRACT: Chiral photonics deals with enantioselective polarization control of linear and nonlinear optical functions and holds a great promise for a wide range of applications including optical signal processing, biosensing, and chiral bioimaging. Development of chiral materials with optical activity exceeding that of natural materials therefore becomes a prerequisite to realizing the full potential of this field. Herein, we report on a study of structure–property relations of two chiral polymers with ester functional groups in lateral branch. To enhance rotational strength, the macroscopic measure of chirality, we employ a fluorene–quinoxaline motif in the monomer unit. To the best of our knowledge, we find the optical activity of one of the studied polymers to be the highest reported so far. Theoretical calculations reveal a correlation between the topological conformations and the simulated CD spectra in agreement with the experimental measurements and help clarify the mechanism of optical activity enhancement that could create insight for further enhancement of chirality.
    Macromolecules 09/2013; 46(18):7158–7165. · 5.93 Impact Factor
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    ABSTRACT: We introduce a mechanical approach to phase transfer of PEGylated gold nanorods. Amphiphilic PEG ligands can be switched between hydrophilic and hydrophobic states by applying mechanical force. PEG-GNRs in their hydrophobic state self-assemble into rings, a phenomenon previously observed only for GNRs capped with hydrophobic ligands.
    Chemical Communications 09/2013; · 6.38 Impact Factor
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    ABSTRACT: This contribution reports the chiro-optic response of as-cast and photopatterned films of silver nanoparticles capped with photothermally-cleavable chiral ligands. We demonstrate broadband circular dichroism in these nanoparticle films, which is not present in dispersions of the nanoparticles capped with the chiral ligands. Long wavelength circular dichroism is derived from coupling of the plasmonic bands of neighbouring silver nanoparticles. Furthermore, the chiral response is preserved in the microstructured film after photopatterning using direct two-photon absorption in the plasmonic band of the silver nanoparticles. Thus, both the as-cast and photopatterned films show circular dichroism from the UV wavelength of intrinsic absorption of the ligand, through the plasmon resonances of both the isolated silver nanoparticles and the interacting nanoparticles, which extend to the near IR. Density functional theory (DFT) calculations of model electronic complexes of a chiral ligand and a small metallic cluster suggest that the new chiral bands at the plasmonic resonances are derived from new chiral hybrid electronic states of the metal nanoparticle-ligand complexes.
    Nanoscale 09/2013; 5(21):10550. · 6.74 Impact Factor
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    ABSTRACT: We report a new type of heterogeneous nanoparticles (NPs) composed of a heavily-doped semiconductor domain (Cu2-xSe) and a metal domain (Au), which exhibit a broad localized surface plasmon resonance (LSPR) across visible and near infrared (NIR) wavelengths, arising from interactions between the two nanocrystal domains. We demonstrate both in vivo photoacoustic imaging and in vitro dark field imaging, using the broad LSPR in Cu2-xSe-Au hybrid NPs to achieve contrast at different wavelengths. The high photoacoustic imaging depth achieved, up to 17 mm, shows that these novel contrast agents could be clinically relevant. More broadly, this work demonstrates a new strategy for tuning LSPR absorbance by engineering the density of free charge carriers in two interacting domains.
    Nano Letters 08/2013; · 13.03 Impact Factor
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    ABSTRACT: Enhanced DC conductivity and photoconductivity of cationic carbazole tethered deoxyribonucleic acid (Cz-DNA) in film devices is achieved by incorporating mobility enhancers. An anthracene-based organic semiconductor (namely 4HPA-Ant) and the inorganic semiconductor cadmium sulfide (CdS) multipod nanocrystal (NC) were used as the mobility enhancers. Space charge limited current (SCLC) experiments show that hole mobility in CdS:Cz-DNA composite film is improved significantly, by about an order of magnitude, compared to the Cz-DNA film. Similarly, the DC conductivity of the composite film is slightly enhanced by 4HPA-Ant. The photoconductivity is also improved in the Cz-DNA composite, with both 4HPA-Ant and CdS multipod NCs. The enhancement in photocurrent is by more than an order of magnitude, as demonstrated by current-voltage (I-V) characterization using DNA composite photodetectors.
    Nanotechnology 07/2013; 24(33):335203. · 3.67 Impact Factor
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    ABSTRACT: Nanochemistry and nanomaterials provide numerous opportunities for a new generation of photovoltaics with high solar energy conversion efficiencies at low fabrication cost. Quantum-confined nanomaterials and polymer-inorganic nanocomposites can be tailored to harvest sun light over a broad range of the spectrum, while plasmonic structures offer effective ways to reduce the thickness of light-absorbing layers. Multiple exciton generation, singlet exciton fission, photon down-conversion, and photon up-conversion realized in nanostructures, create significant interest for harvesting underutilized ultraviolet and currently unutilized infrared photons. Nanochemical interface engineering of nanoparticle surfaces and junction-interfaces enable enhanced charge separation and collection. In this review, we survey these recent advances employed to introduce new concepts for improving the solar energy conversion efficiency, and reduce the device fabrication cost in photovoltaic technologies. The review concludes with a summary of contributions already made by nanochemistry. It then describes the challenges and opportunities in photovoltaics where the chemical community can play a vital role.
    Chemical Society Reviews 07/2013; · 30.43 Impact Factor

Publication Stats

12k Citations
2,413.87 Total Impact Points


  • 2012–2014
    • Korea University
      • Department of Chemistry
      Sŏul, Seoul, South Korea
    • Universidade Federal do Paraná
      • Department of Chemistry
      Curityba, Paraná, Brazil
    • Chinese PLA General Hospital (301 Hospital)
      Peping, Beijing, China
    • University of Colorado at Boulder
      • Liquid Crystal Materials Research Center
      Boulder, CO, United States
    • Federal University of Pernambuco
      Arrecife, Pernambuco, Brazil
  • 2004–2014
    • State University of New York
      New York City, New York, United States
  • 2013
    • University of Massachusetts Medical School
      • Department of Biochemistry and Molecular Pharmacology
      Worcester, MA, United States
  • 2012–2013
    • Harbin Institute of Technology
      • • School of Chemical Engineering and Technology
      • • Department of Chemical Engineering
      Harbin, Heilongjiang Sheng, China
  • 1976–2013
    • University at Buffalo, The State University of New York
      • • Department of Chemistry
      • • Institute for Lasers, Photonics and Biophotonics
      • • Department of Electrical Engineering
      • • Department of Pathology and Anatomical Sciences
      Buffalo, New York, United States
  • 2011–2012
    • Changchun University of Science and Technology
      Changchun, Fujian, China
    • University of Southern California
      • Department of Otolaryngology-Head and Neck Surgery
      Los Angeles, CA, United States
  • 2010–2012
    • SUNY Ulster
      Kingston, New York, United States
    • Nanyang Technological University
      • School of Electrical and Electronic Engineering
      Singapore, Singapore
  • 2009–2010
    • Hannam University
      • Department of Advanced Materials
      Daiden, Daejeon, South Korea
    • Zhejiang University
      Hang-hsien, Zhejiang Sheng, China
  • 2006–2010
    • KTH Royal Institute of Technology
      • Division of Theoretical Chemistry and Biology
      Stockholm, Stockholm, Sweden
  • 2008–2009
    • Buffalo General Medical Center
      Buffalo, New York, United States
    • National Central University
      • Department of Chemistry
      Taoyuan City, Taiwan, Taiwan
  • 2005–2007
    • Roswell Park Cancer Institute
      • • Department of Dermatology
      • • Photodynamic Therapy Center
      • • PDT Center
      Buffalo, New York, United States
    • Rochester Institute of Technology
      Rochester, New York, United States
  • 1993–2006
    • Massachusetts Institute of Technology
      • Department of Materials Science and Engineering
      Cambridge, MA, United States
  • 1972–2006
    • University of Michigan
      • Department of Chemistry
      Ann Arbor, Michigan, United States
  • 2003–2004
    • University of California, Berkeley
      • Department of Chemistry
      Berkeley, MO, United States
  • 1972–1973
    • University of Pennsylvania
      • Laboratory for Research on the Structure of Matter
      Philadelphia, Pennsylvania, United States
    • Concordia University–Ann Arbor
      Ann Arbor, Michigan, United States