Home | Research | Selected Publications | Members| Resources | Collaborations | About Dr. Robert Strongin 

Latest News

May 22/18

New accepted article": "In Situ Lysosomal Cysteine-Specific Targeting and Imaging during Dexamethasone-Induced Apoptosis," published in Analytical Chemistry.

May 15/18

New accepted article": "E-cigarettes can emit formaldehyde at high levels under conditions that have been reported to be non-averse to users," published in Scientific Reports.

March 15/18

New accepted article": "Varied Length Stokes Shift BODIPY-Based Fluorophores for Multicolor Microscopy," published in Scientific Reports.

January 10/18

We welcome our new graduate student Megha Gupta.

January 05/18

New accepted article": "E-Cigarette Airflow Rate Modulates Toxicant Profiles and Can Lead to Concerning Levels of Solvent Consumption," published in ACS Omega.

New accepted article": "Dihydroxyacetone Levels in Electronic Cigarettes: Wick Temperature and Toxin Formation," published in Aerosol Sci. Technol.

September 22/17

New accepted article": "Toxicant Formation in Dabbing: The Terpene Story," published in ACS Omega.

September 11/17

New accepted article": "Formaldehyde Hemiacetal Sampling, Recovery, and Quantification from Electronic Cigarette Aerosols," published in Scientific Reports.

January 20/17

New accepted article": "Far-red and near-infrared seminaphthofluorophores for targeted pancreatic cancer imaging," published in ACS Omega.

January 18/17

We welcome our new graduate students Tendai Mafireyi and Jiries Meehan-Atrash.

June 16/16

New accepted article: "Systemic delivery and biodistribution of cisplatin in vivo," published in Molecular Pharmaceutics.

February 11/16

New accepted critical review: "Recent progress in chromogenic and fluorogenic chemosensors for hypochlorous acid," published in Analyst.

January 16/16

New accepted article: "Fluorescein tri-aldehyde promotes the selective detection of homocysteine," published in The Journal of Fluorescence.

January 04/16

We welcome our new graduate students Shawna Vreeke and Ian Munhenzva.

December 02/15

New accepted article: "Rhodamine analogues for molecular ruler applications," published in Dyes and Pigments.

November 06/15

New ASAP article: "Templated polymers enable selective capture and release of lysophosphatidic acid in human plasma via optimization of non-covalent binding to functional monomers," published in Analyst.

April 17/15

New ASAP article: "A simple assay for glutathione in whole blood," published in Analyst.

January 22/15

PSU researchers find hidden formaldehyde in E-cigarette aerosols. The findings were published by the New England Journal of Medicine.

December 08/14

New ASAP communication: "Spiroguanidine rhodamines as fluorogenic probes for lysophosphatidic acid," published in Chemical Communications.

June 10/14

New ASAP communication:  "Differences in heterocycle basicity distinguish homocysteine from cysteine using aldehyde-bearing fluorophores," published in Chemical Communications.

June 02/14

Professor Strongin is the recipient of the 2014 John Eliot Allen Teaching Award for the Department of Chemistry.  The awards ceremony will be on Friday, June 6 at the Smith Center Ballroom from 3-5 pm.

February 28/14

New ASAP edge article: "A dual emission fluorescent probe enables simultaneous detection of glutathione and
" published in Chemical Science.

February 10/14

New ASAP communication: "A photochemical method for determining plasma homocysteine with limited sample processing" published in Chemical Communications.

Older news

Welcome to our website

We work in the fields of synthetic and physical organic chemistry, with a focus on redox and chromophore materials and mechanisms. Examples of current studies include the chemistry of electronic cigarettes as well as pharmaceutical, sensor and molecular probe design. The multidisciplinary nature of these topics promotes collaborative research. Local and global collaborations involve the (i) elucidation of reaction pathways and byproducts in electronic cigarettes and hookahs, (ii) targeted imaging of pancreatic cancer, (iii) monitoring of chronic disease, (iv) elucidation of cellular trafficking mechanisms of major pharmaceutical side-effects, and (v) synthesis of highly potent pharmaceuticals that normalize heart arrhythmias via a redox mechanism.

  • Wang, L.; Barth, C. W.; Sibrian-Vazquez, M.; Escobedo, J. O.; Lowry, M.; Muschler, J.; Li, H.; Gibbs, S. L.; Strongin, R. M. "Far-red and near-infrared seminaphthofluorophores for targeted pancreatic cancer imaging," ACS Omega, 2017 2, 154-163, doi:10.1021/acsomega.6b00403.
  • Jensen, R. Paul; Luo, Wentai; Pankow, James F.; Strongin, Robert M.; Peyton, David H. Hidden Formaldehyde in E-Cigarette Aerosols. N. Engl. J. Med. 2015, 372, 392-394.
  • Yang, X.-F.; Huang, Q.; Zhong, Y.; Li, H.; Li, Z.; Lowry, M.; Escobedo,J. O.; Strongin, R. M. A dual emission fluorescent probe enables simultaneous detection of glutathione and cysteine/homocysteine. Chem. Sci., 2014, 5, 2177-2183 (cover feature).
  • Sibrian-Vazquez, M., Escobedo, J.O.; Lim, S.; Samoei, G. K.; Strongin, R. M. Homocystamides promote free-radical and oxidative damage to proteins. Proc. Natl. Acad. Sci. USA 2010, 107, 551-554.
  • Yang, Y. J.; Lowry, M.; Xu, X. Y.; Escobedo, J. O.; Sibrian-Vazquez, M.; Wong, L.; Schowalter, C. M.; Jensen, T. J.; Fronczek, F. R.; Warner, I. M.; Strongin, R. M. Seminaphthofluorones are a family of water-soluble, low molecular weight, NIR-emitting fluorophores. Proc. Natl. Acad. Sci. USA 2008, 105, 8829-8834.

Contributions to Science
  1. Early studies: conjugated materials leading to abiotic biosensors. Our earliest research focused on developing synthetic methods for challenging target molecules with unique redox and/or chromophore properties. Accomplishments included the first synthesis of the fullerene C122, via the reaction of C60 with atomic carbon. The structure contains two fullerenes linked via a bi(cyclopropylidene) bridge. At the time of the publication, the fullerene-derived dimers, including C121 and C122, and other structurally-related carbon allotrope clusters, had only been observed via mass spectrometry. Our work showed that they could be stable, isolable synthetic targets. This prompted theoretical and experimental interest in analog synthesis as well as in inter-sphere electron transfer effects and materials properties. Meantime, we were investigating a rational synthesis of other unique classes of conjugated materials via a macrocycle based template approach. We developed new synthetic methods for aryl borylation and Suzuki coupling reactions, as well as controlled syntheses of well-defined oligophenylene rods that were successfully coupled to the macrocycle. However, it was troubling to us that solutions of the calixarene-type macrocycles used in these studies developed intense color upon standing, despite the fact that they did not possess conjugation beyond isolated arene rings.
    Although this class of compounds was very well-known, the only prior report on their color formation appeared in a 19th century manuscript by von Baeyer. We eventually determined that trace amounts of xanthene dye chromophores were formed via ring opening and oxidation of the macrocycle. Prompted by the known affinity of arylboronic acids for sugars, we used this material to attain the formation of 12 different solution colors corresponding to 12 different sugar structures, as described in our initial manuscript in the sensor field. At the time, the use of boronic acid dyes for selective colorimetric sugar sensing was still in its infancy. The only prior related example of visual inspection-based selectivity for specific sugars had been reported by Shinkai and co-workers, the most prolific among what was then a limited number of research groups studying related fluorescent sensors.

    • He, M.; Johnson, R.J.; Escobedo, J.O.; Beck, P.A.; Kim, K.K.; St Luce, N.N.; Davis, C.J.; Lewis, P.T.; Fronczek, F.R.; Melancon, B.J.; Mrse, A.A.; Treleaven, W.D.; Strongin, R.M. Chromophore formation in resorcinarene solutions and the visual detection of mono- and oligosaccharides. J. Am. Chem. Soc. 2002, 124, 5000-5009.
    • Willis, D.M. and R.M. Strongin, Palladium-catalyzed borylation of aryldiazonium tetrafluoroborate salts. A new synthesis of arylboronic esters. Tetrahedron Lett. 2000, 41, 8683-8686.
    • Davis, C.J.; Lewis, P.T.; McCarroll, M.E.; Read, M.W.; Cueto, R.; Strongin, R.M. Simple and rapid visual sensing of saccharides. Org. Lett. 1999, 1, 331-334 (Highlighted in C & E News).
    • Fabre, T.S.; Treleaven, W.D.; McCarley, T.D.l Newton, C.L. Landry, R.M. ; Saraiva, M.C.; Strongin, R.M. The reaction of buckminsterfullerene with diazotetrazole. Synthesis, isolation, and characterization of (C60)2C2. J. Org. Chem. 1998, 63, 3522-3523.

  2. Simple chemical indicators with high selectivity for specific sugars. Encouraged by the findings summarized above, we tuned the structures of simple organic pH dyes to detect specific bioactive molecules, to help move the field beyond the well-known indicators for protons and metal cations. There was related ongoing research at the time in the boronic acid glucose sensing field. We thus focused on creating boronic acid-derived indicators that exhibited selectivity for sugars other than the well-studied glucose or fructose. Towards this end we synthesized the first known boronic acid optical chemosensor that had inherent selectivity for ribose (left, and ribose derivatives) rather than for fructose. This prompted its demonstration as the first indicator for the riboside biomarkers of Adenosyl Lyase Deficiency (ADSL), a devastating inborn error of purine metabolism that is one of the autism spectrum disorders. In related work, we also discovered a chemosensor selective for sialic acid, a sugar acid commonly associated with cancer pathogenesis when expressed at abnormal levels. We extensively investigated and described the mechanistic basis for these examples of previously unreported optical selectivity in the boronic acid sensor field towards expanding the scope and utility of arylboronic acid dyes.

    • Lim, S.; Escobedo, J. O.; Lowry, M.; Strongin, R. M. Detecting specific saccharides via a single indicator. Chem. Comm. 2011, 47, 8295-8297.
    • Jiang, S.; Escobedo, J.O.; Kim, K.K.; Alpturk, O.; Samoei, G.K.; Fakayode, S.O.; Warner, I. M.; Rusin, O.; Strongin, R.M. Stereochemical and regiochemical trends in the selective detection of saccharides. J. Am. Chem. Soc. 2006. 128, 12221-12228.
    • Yang, Y.J.; Lewis, P.T.; Escobedo, J.O.; St Luce, N.N.; Treleaven, W.D.; Cook, R.L.; Strongin, R. M. Mild colorimetric detection of sialic acid. Collect. Czech. Chem. Comm. 2004, 69, 1282-1291 (invited special issue in honor of Prof. Ivan Stibor).

  3. Targeted molecular probes and indicators for disease biomarkers. In order to use selective indicators to address issues in disease diagnostics beyond sugar detection, we targeted other bioactive small molecules such as biological thiols, lysophospholipids and glycolipids. These studies additionally led to the colorimetric detection of a specific post-translational protein modification resulting from the reaction of homocysteine thiolactone with lysine residues. Our manuscript describing the use of simple aldehyde-bearing xanthene dyes for sensing cysteine and homocysteine popularized this approach and prompted many related selective thiol probe syntheses in the field, enabling a variety of sensing and cellular imaging studies. A relatively more recent report on the use of acrylate-functionalized dyes for selective biothiol detection has similarly received significant attention in the community and has helped initiate many related investigations of acrylate-based "turn-on" fluorescent indicators. Our project on homocysteine detection led to the first selective homocysteine colorimetric indicator (no interference from cysteine or glutathione), via a hydrogen atom transfer mechanism. The methodology has enabled homocysteine detection in unprocessed human blood plasma samples.
    In addition, the mechanistic and sensing studies led to the finding that protein homocysteinylation was a source of protein free radicals and carbonyl formation. In other studies, we developed a simple and rapid indicator for glutathione (GSH). It is currently being marketed along with several of our other indicators. In related work, the GSH sensor enabled the development of a convenient blood spot test. We have thus developed simple and useful detection materials and methods for each of the three major biological thiols, cysteine, homocysteine and glutathione.
    Many new fluorescent dyes have been synthesized in our group, including the white light emitter (above, looking down into a cuvette) and large Stokes shift dyes that absorb and emit in the near infra-red. These molecules are under study for targeted imaging applications.

    • Yang, X. F.; Guo, Y. X.; Strongin, R. M. Conjugate addition/cyclization sequence enables selective and simultaneous fluorescence detection of cysteine and homocysteine. Angew. Chem., Int. Ed. 2011, 50, 10690-10693.
    • Sibrian-Vazquez, M., Escobedo, J.O.; Lim, S.; Samoei, G. K.; Strongin, R. M. Homocystamides promote free-radical and oxidative damage to proteins. Proc. Natl. Acad. Sci. USA 2010, 107, 551-554.
    • Escobedo, J.O.; Wang, W.H.; Strongin, R.M. Use of a commercially available reagent for the selective detection of homocysteine in plasma. Nat. Protoc. 2006, 1, 2759-2762 (invited protocol manuscript).
    • Rusin, O.; St Luce, N.N.; Agbaria, R.A.; Escobedo, J.O.; Jiang, S.; Warner, I.M.; Dawan, F.B.; Lian, K.; Strongin, R.M. Visual detection of cysteine and homocysteine. J. Am. Chem. Soc. 2004, 126, 438-439.

    Complete List of Published Work in MyBibliography: http://www.ncbi.nlm.nih.gov/sites/myncbi/robert.strongin.1/bibliography/41163194/public/?sort=date&direction=ascending

Strongin Group

From right to left:  Jialu Wang, Dr. Martha Sibrian-Vazquez, Dr. Jorge Escobedo, Dr. Mark Lowry, Lovemore Hakuna, Yixing Guo, Dr. Xiaofeng Yang (visiting professor), Dr. Soojin Lim, Shelly Chu and Aabha Barve.

ChemPDX1 Youtube channel


We are currently located in rooms 71 and 76, B1 level at the Science Research and Teaching Center (formerly known as Science Building 2).