title: PEG-coumarin based biocompatible self-assembled fluorescent nanoaggregates synthesized via click reactions and studies of aggregation behavior.
abstract: OBJECTIVE
  Click chemistry has found wide application in drug discovery, bioconjugation reactions, polymer chemistry and synthesis of amphiphilic materials with pharmaceutical and biomedical applications. Triazole substitution via a click reaction alters photophysical properties of coumarin. Both coumarin and triazole moieties participate in π-π stacking interactions. Hence it should be possible to prepare fluorescent self-assembly systems by conjugation of coumarin to poly (ethylene glycol) (PEG) via click reactions exhibiting hydrophilic, hydrophobic and π-π stacking interactions. Moreover, the materials can be suitable platforms to assess fluorescence modulation effect of triazole substitution on coumarins.
  
  
  METHODS
  PEG supported coumarin conjugates were synthesized and the fluorescence modulation effect of the formation of triazole on coumarin was assessed. Their aggregation properties were studied by surface tension measurements, dynamic light scattering (DLS), transmission electron microscopy (TEM), fluorescence and (1)H NMR spectroscopy.
  
  
  RESULTS
  The conjugates were found to form nanoaggregates in the size range of 100-120 nm with a negative free energy of micellization (~-27 kJ mol(-1)) confirming aggregation and self-assembly. The Quantum yield of 4-methyl-7-propargylcoumarin (7P4MC) was enhanced after triazole formation with azide functionalized PEG (methoxy-PEG350 azide). The conjugates were found to exhibit π-π stacking interactions in addition to hydrophilic and hydrophobic interactions. They were found to be biocompatible with human pancreatic cancer cells.
authors.affiliation: Department of Chemistry, Dyal Singh College, University of Delhi, Lodhi Road, Delhi 110003, India.
authors.forename: Gautam
authors.initials: G
authors.lastname: Behl
authors.affiliation: Dr. B.R. Ambedkar Center for Biomedical Research, University of Delhi, Delhi 110007, India.
authors.forename: Manisha
authors.initials: M
authors.lastname: Sikka
authors.affiliation: Department of Chemistry, Dyal Singh College, University of Delhi, Lodhi Road, Delhi 110003, India. Electronic address: arunachhikara@gmail.com.
authors.forename: Aruna
authors.initials: A
authors.lastname: Chhikara
authors.affiliation: Dr. B.R. Ambedkar Center for Biomedical Research, University of Delhi, Delhi 110007, India. Electronic address: mchopradu@gmail.com.
authors.forename: Madhu
authors.initials: M
authors.lastname: Chopra
mesh_terms: D001386:Azides / Q000737:chemistry; D001672:Biocompatible Materials; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D057930:Click Chemistry; D003374:Coumarins / Q000737:chemistry*; D004337:Drug Carriers / Q000138:chemical synthesis* / Q000494:pharmacology; D005427:Flocculation; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D009682:Magnetic Resonance Spectroscopy; D046529:Microscopy, Electron, Transmission; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure; D011092:Polyethylene Glycols / Q000737:chemistry*; D013816:Thermodynamics; D014230:Triazoles / Q000737:chemistry*
chemical_list: D001386:Azides; D001672:Biocompatible Materials; D003374:Coumarins; D004337:Drug Carriers; D014230:Triazoles; D011092:Polyethylene Glycols
keywords: Biocompatible; CAC; Click reaction; Coumarin; Fluorescence; Nanoaggregates; PEG; Self-assembly; Stacking