Unveiling the Self-Assembling Behavior of 5-Fluorouracil and its N,N′-Dimethyl Derivative: A Spectroscopic and Microscopic Approach

Abstract

Under physiological conditions, 5-fluorouracil (5-FU), an anticancer drug, self-assembles into fibrils by strong hydrogen-bonding network, whereas its N,N'-dimethyl derivative, 5-fluoro-1,3-dimethyluracil (5-FDMU), does not make fibrils due to lack of strong hydrogen-bonding motif. In vitro, 5-FU self-assembly is sensitive to physicochemical conditions like the pH and ionic strength of the solution, which tune the strength of the noncovalent driving forces. Here we report a surprising finding that the buffer, which is necessary to control the pH and is typically considered to be inert, also significantly influences 5-FU self-assembly, which indicates an important role of counterions in the fibril formation. We have also monitored concentration- and time-dependent fibrillar growth of 5-FU. Again, fibril growth process is probed under dynamic conditions using microfluidic platform. The self-assembly of 5-FU compared with its N,N'-dimethyl derivative shows lower cytotoxicity to the cultured human erythroleukemic cells (K562 cells), which plausibly states the reason behind the greater effectiveness of 5-FU derivative drugs than 5-FU itself.

Selective Self-Assembly of 5-Fluorouracil through Nonlinear Solvent Response Modulates Membrane Dynamics

“…Price and co-workers have reported about the tight solvation of 5-FU hydrogen bonding groups by water molecules in pure water . We have also observed no fibril formation of 5-FU in pure water in our previous study . Harmandaries and co-workers also have reported that type of nanostructure tuning of diphenylalanine dipeptide using the higher methanol–water mixture .…”

“…Since fluorescence lifetime is insensitive to local signal intensity and fluorophore concentration, FLIM provides significant benefits. , Lifetime images are displayed as a false-color image of the lifetime obtained for each pixel . We have used DCM (4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran) (∼6 μM) molecule to probe 5-FU morphologies, as DCM was previously successfully used to detect fibrillar structures. , 5-FU concentration is kept the same for all DMSO–water compositions and it is 38 mM. The high concentration correlates to the recommended physiological and medicinal doses of 5-FU .…”

“…Solvent-dependent nanostructure formation may open up new possibilities for precise control of such nanostructures for application in biomedicine and nanotechnology . In our previous work, we have shown that 5-FU can form different fibrillar morphologies in different buffer systems . 5-FU self-assembles through strong intermolecular hydrogen bonding between −NH···OC–. , Interestingly, in pure water, 5-FU cannot form fibrillar structures because of the tight solvation of hydrogen-bonding groups by water molecules .…”

“…On the other hand, spontaneous self-assembly of small molecule drugs such as 5-fluorouracil (5-FU) cause a notable decrease in its drug efficiency. , 5-FU is cheap and extensively used as a chemotherapeutic drug and radiosensitizer. , But, in recent times, the use of 5-FU has been very much restricted because of its systematic toxicity and resistance. − The design of this particular study is based on our recent efforts to explore and understand the supramolecular fibrillar assembly of uracil derivatives, especially 5-FU in different buffers. , Though the ability of small molecules to form ordered structures at the nanoscale is one of the most promising directions in nanotechnology, merely inducing aggregation is not sufficient. The control and understanding of the self-assembly process has great potential for a multitude of future applications .…”

“…In our previous work, we have shown that 5-FU can form different fibrillar morphologies in different buffer systems . 5-FU self-assembles through strong intermolecular hydrogen bonding between −NH···OC–. , Interestingly, in pure water, 5-FU cannot form fibrillar structures because of the tight solvation of hydrogen-bonding groups by water molecules . We have introduced a DMSO–water binary mixture of different compositions as a solvent system of 5-FU.…”