Academic Appointments

  • Instructor, Radiology

Honors & Awards

  • NSERC PDF, (Canada) (2018-2020)
  • Philips Healthcare Fellow, Philips, Stanford (2018-2019)
  • Dean's Fellowship (School of Medicine), Stanford (2017-2018)
  • Carl A. Winkler award for outstanding academic excellence – Thesis award, McGill University (2016-2017)
  • Sterry Hunt award for outstanding services as a Teaching assistant, McGill University (Chemistry departement) (2012/1 - 2013/9)
  • Nicolas Jaber Prize for academic excellence ( top 10 in the faculty of arts and science), American University of Beirut (AUB) (June 2009)

All Publications

  • Dynamic DNA Nanotubes: Reversible Switching between Single and Double-Stranded Forms, and Effect of Base Deletions ACS NANO Rahbani, J. F., Hariri, A. A., Cosa, G., Sleiman, H. F. 2015; 9 (12): 11898-11908


    DNA nanotubes hold great potential as drug delivery vehicles and as programmable templates for the organization of materials and biomolecules. Existing methods for their construction produce assemblies that are entirely double-stranded and rigid, and thus have limited intrinsic dynamic character, or they rely on chemically modified and ligated DNA structures. Here, we report a simple and efficient synthesis of DNA nanotubes from 11 short unmodified strands, and the study of their dynamic behavior by atomic force microscopy and in situ single molecule fluorescence microscopy. This method allows the programmable introduction of DNA structural changes within the repeat units of the tubes. We generate and study fully double-stranded nanotubes, and convert them to nanotubes with one, two and three single-stranded sides, using strand displacement strategies. The nanotubes can be reversibly switched between these forms without compromising their stability and micron-scale lengths. We then site-specifically introduce DNA strands that shorten two sides of the nanotubes, while keeping the length of the third side. The nanotubes undergo bending with increased length mismatch between their sides, until the distortion is significant enough to shorten them, as measured by AFM and single-molecule fluorescence photobleaching experiments. The method presented here produces dynamic and robust nanotubes that can potentially behave as actuators, and allows their site-specific addressability while using a minimal number of component strands.

    View details for DOI 10.1021/acsnano.5b04387

    View details for Web of Science ID 000367280100038

    View details for PubMedID 26556531

  • Stepwise growth of surface-grafted DNA nanotubes visualized at the single-molecule level NATURE CHEMISTRY Hariri, A. A., Hamblin, G. D., Gidi, Y., Sleiman, H. F., Cosa, G. 2015; 7 (4): 295-300


    DNA nanotubes offer a high aspect ratio and rigidity, attractive attributes for the controlled assembly of hierarchically complex linear arrays. It is highly desirable to control the positioning of rungs along the backbone of the nanotubes, minimize the polydispersity in their manufacture and reduce the building costs. We report here a solid-phase synthesis methodology in which, through a cyclic scheme starting from a 'foundation rung' specifically bound to the surface, distinct rungs can be incorporated in a predetermined manner. Each rung is orthogonally addressable. Using fluorescently tagged rungs, single-molecule fluorescence studies demonstrated the robustness and structural fidelity of the constructs and confirmed the incorporation of the rungs in quantitative yield (>95%) at each step of the cycle. Prototype structures that consisted of up to 20 repeat units, about 450 nm in contour length, were constructed. Combined, the solid-phase synthesis strategy described and its visualization through single-molecule spectroscopy show good promise for the production of custom-made DNA nanotubes.

    View details for DOI 10.1038/NCHEM.2184

    View details for Web of Science ID 000351756200008

    View details for PubMedID 25803467

  • Interaction of Anionic Phenylene Ethynylene Polymers with Lipids: From Membrane Embedding to Liposome Fusion LANGMUIR Karam, P., Hariri, A. A., Calver, C. F., Zhao, X., Schanze, K. S., Cosa, G. 2014; 30 (35): 10704-10711


    Here we report spectroscopic studies on the interaction of negatively charged, amphiphilic polyphenylene ethynylene (PPE) polymers with liposomes prepared either from negative, positive or zwitterionic lipids. Emission spectra of PPEs of 7 and 49 average repeat units bearing carboxylate terminated side chains showed that the polymer embeds within positively charged lipids where it exists as free chains. No interaction was observed between PPEs and negatively charged lipids. Here the polymer remained aggregated giving rise to broad emission spectra characteristic of the aggregate species. In zwitterionic lipids, we observed that the majority of the polymer remained aggregated yet a small fraction readily embedded within the membrane. Titration experiments revealed that saturation of zwitterionic lipids with polymer typically occurred at a polymer repeat unit to lipid mole ratio close to 0.05. No further membrane embedding was observed above that point. For liposomes prepared from positively charged lipids, saturation was observed at a PPE repeat unit to lipid mole ratio of ∼0.1 and liposome precipitation was observed above this point. FRET studies showed that precipitation was preceded by lipid mixing and liposome fusion induced by the PPEs. This behavior was prominent for the longer polymer and negligible for the shorter polymer at a repeat unit to lipid mole ratio of 0.05. We postulate that fusion is the consequence of membrane destabilization whereby the longer polymer gives rise to more extensive membrane deformation than the shorter polymer.

    View details for DOI 10.1021/la502572u

    View details for Web of Science ID 000341543100019

    View details for PubMedID 25115171

  • Simple Design for DNA Nanotubes from a Minimal Set of Unmodified Strands: Rapid, Room-Temperature Assembly and Readily Tunable Structure ACS NANO Hamblin, G. D., Hariri, A. A., Carneiro, K. M., Lau, K. L., Cosa, G., Sleiman, H. F. 2013; 7 (4): 3022-3028


    DNA nanotubes have great potential as nanoscale scaffolds for the organization of materials and the templation of nanowires and as drug delivery vehicles. Current methods for making DNA nanotubes either rely on a tile-based step-growth polymerization mechanism or use a large number of component strands and long annealing times. Step-growth polymerization gives little control over length, is sensitive to stoichiometry, and is slow to generate long products. Here, we present a design strategy for DNA nanotubes that uses an alternative, more controlled growth mechanism, while using just five unmodified component strands and a long enzymatically produced backbone. These tubes form rapidly at room temperature and have numerous, orthogonal sites available for the programmable incorporation of arrays of cargo along their length. As a proof-of-concept, cyanine dyes were organized into two distinct patterns by inclusion into these DNA nanotubes.

    View details for DOI 10.1021/nn4006329

    View details for Web of Science ID 000318143300015

    View details for PubMedID 23452006

  • Kinetics of Strand Displacement and Hybridization on Wireframe DNA Nanostructures: Dissecting the Roles of Size, Morphology, and Rigidity ACS NANO Platnich, C. M., Hariri, A. A., Rahbani, J. F., Gordon, J. B., Sleiman, H. F., Cosa, G. 2018; 12 (12): 12836–46


    Dynamic wireframe DNA structures have gained significant attention in recent years, with research aimed towards using these architectures for sensing and encapsulation applications. For these assemblies to reach their full potential, however, knowledge on the rates of strand displacement and hybridization on these constructs is required. Herein, we report the use of single molecule fluorescence methodologies to observe the reversible switching between double- and single-stranded forms of triangular wireframe DNA nanotubes. Specifically, by using fluorescently labeled DNA strands, we were able to monitor changes in intensity over time as we introduced different sequences. This allowed us to extract detailed kinetic information on the strand displacement and hybridization processes. Due to the polymeric NT structure, the ability to individually address each of the three sides, and the inherent polydispersity of our samples as a result of the step polymerization by which they are formed, a library of compounds could be studied independently yet simultaneously. Kinetic models relying on simple exponential decays, multi-exponential decays or sigmoidal behavior were adjusted to the different constructs to retrieve erasing and refilling kinetics. Correlations were made between the kinetic behavior observed, the site accessibility, the nanotube length, and the structural robustness of wireframe DNA nanostructures, including fully single-stranded analogs. Overall, our results reveal how the length, morphology, and rigidity of the DNA framework modulate the kinetics of strand displacement and hybridization, as well as the overall addressability and structural stability of the structures under study.

    View details for DOI 10.1021/acsnano.8b08016

    View details for Web of Science ID 000454567500108

    View details for PubMedID 30485067

  • Z-Profiling of CFTR Oligomerization State Distributions via Single Molecule Step Photobleaching Analysis in Epithelial Cells 59th Annual Meeting of the Biophysical-Society Desjardins, J., Abu-Arish, A., Hariri, A., Sleiman, H. F., Cosa, G., Hanrahan, J. W., Wiseman, P. W. CELL PRESS. 2015: 322A–322A
  • Visualizing the Formation and Exploring the Structure and Dynamics of DNA-Architectures. A Single Molecule Study 57th Annual Meeting of the Biophysical-Society Hariri, A. A., Hamblin, G., Sleiman, H., Cosa, G. CELL PRESS. 2013: 177A–177A
  • Band, target, and onion patterns in Co(OH)(2) Liesegang systems PHYSICAL REVIEW E Badr, L., Moussa, Z., Hariri, A., Sultan, R. 2011; 83 (1)


    The study of morphology and shape development has gained considerable interest in certain sciences, notably biology and geology. Liesegang experiments producing Co(OH)2 stratification are performed here, in one, two, and three dimensions for comparison of the pattern morphologies. We obtain well-resolved bands in one dimension, target patterns (rings) in two dimensions, and onion patterns (spherical shells) in three dimensions. The morphological characteristics of the various patterns (spacing coefficients, rate of growth of ring spacing with distance) were measured. The spacing ratio of the strata in the different spatial dimensions was found to be anticorrelated with the surface-to-volume ratio of the gel domain. Some studies featuring the importance of morphology in Liesegang systems are briefly surveyed.

    View details for DOI 10.1103/PhysRevE.83.016109

    View details for Web of Science ID 000286763100001

    View details for PubMedID 21405746