PEG-coumarin based biocompatible self-assembled fluorescent nanoaggregates synthesized via click reactions and studies of aggregation behavior

• PEG-coumarin based fluorescent conjugates were synthesized via click reactions.
• The conjugates formed self-assembled nanoaggregates within size range of 100–120 nm.
• Fluorescence modulation effect of triazole was observed by photophysical characterizations.
• Existence of π–π stacking interactions acting as a driving force for the formation of aggregates was observed.
• The nanoaggregates were found to be biocompatible with pancreatic cancer cell lines.

HypothesisClick 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.ExperimentsPEG 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 1H NMR spectroscopy.FindingsThe 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.

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