Highly sensitive fluorescence turn-on detection of neomycin utilizing premicellar surfactant aggregation in...

Use of antibiotics to mitigate various bacterial, fungal and other infections has become very common practice. Although it immediately solves the problem, prolonged accumulation of antibiotics can have detrimental effects in human body. Therefore, periodic monitoring of antibiotic in human body is extremely essential.

Herein, we have developed a near infrared (NIR) emitting fluorogenic supramolecular dye-surfactant assembly, capitalizing noncovalent interaction between a cationic dye, LDS-798 and anionic surfactant, sodium dodecyl sulfate (SDS) for the detection of a versatile bacterial antibiotic, neomycin. At higher concentration, SDS formed inclusion complex with LDS-798, triggering its large enhancement in emission intensity; however, at lower SDS concentration, LDS-798•SDS ion-pair complex was formed and thus, there was hardly any change in fluorescence for LDS-798. Interestingly, the LDS-798•SDS assembly (with low SDS concentration) exhibited a large enhancement in fluorescence in the presence of neomycin (Neo) due to the formation of a stable LDS-798•SDS•Neo ternary complex. Such enhancement in fluorescence exhibited a linear trend with Neo concentration from 0 to 38 μM which was utilized for the detection of Neo down to 32.1 nM in buffer. Importantly, the LDS-798•SDS complex demonstrated excellent selectivity towards Neo, enabling detection of Neo in complex biofluids such as 1 % human serum and 100 % urine matrix.

Low initial signal, emission in the near-IR region, negligible interference from auto-fluorescence of the background matrices, deep sample penetration, low scattering and utilization of commonly available and inexpensive surfactant make the studied system a promising and economically affordable platform for easy and label free detection of Neo.