Synthesis and characterization of metal organic frameworks for detection of antibiotics

My scientific research began in the area of optical and electrochemical sensors during my studies towards a Ph.D. degree. My Ph.D. thesis work was focused on the synthesis and characterization of different metal-organic frameworks (MOFs) and the application of these MOFs for the fabrication of electrochemical and optical sensors for monitoring trace levels of antibiotics in water samples. Antibiotics are medicines used for the treatment of bacterial infections in humans and animals. However, their overuse resulted in water pollution. Therefore, development of prompt, sensitive, and selective sensing systems is prime need of the modern world. Metal-organic frameworks (MOFs) are porous coordination polymers made up of metal ions and organic linkers which possess high surface area, tunable pore size, and remarkable electric & optical properties. As a result, MOFs have emerged as multifunctional materials for sensing applications. Therefore in my Ph.D. research work, three different MOFs viz. Copper MOF (Cu-MOF), Zirconium MOF (Zr-MOF), and Iron MOF (Fe-MOF) were synthesized solvothermally and used for detection of different antibiotics i.e. ciprofloxacin, nitrofurazone and erythromycin, respectively.

Figure 1 Summary of Ph.D. Research Work

(ⅰ) In the first study, an electrochemical sensor is developed for ciprofloxacin antibiotic which is an emerging water pollutant. For electrochemical sensing, Glassy carbon electrode (GCE) modified with Cu-MOF was used as working electrode (WE). Cu-MOF modified GCE was able to detect ciprofloxacin even at trace levels and gave better performance compared to the other sensors available for ciprofloxacin due to strong interaction between functional groups of copper MOF and CIP antibiotic. The work is published in a reputed SCI-indexed journal.

Figure 2 Schematic of Cu-MOF based electrochemical sensing of ciprofloxacin antibiotic

(ⅱ) In the next study, an electrochemical and fluorescent sensor was prepared for another antibiotic i.e. nitrofurazone (NFZ). The sensor was prepared using a zirconium-based MOF (UiO-66-NH₂). For electrochemical sensor, screen printed carbon electrode (SPCE) was modified with Zr-MOF and gold nanoparticles. For optical sensing, fluorescence behaviour of Zr-MOF solution was monitored in presence of NFZ. The Zr-MOF based sensor gave better response towards NFZ in terms of detection limit compared to the reported sensors in literature. The work is published in a reputed SCI-indexed journal.

Figure 3 Schematic of Zr-MOF based electrochemical-fluorescent sensing of nitrofurazone antibiotic

(ⅲ) In the third study, a novel dual mode bio-sensor (optical-electrochemical) was developed for another antibiotic i.e. erythromycin (ERY). For this, Fe-MOF was synthesized and then conjugated with ERY specific antibodies (ERY_Ab) and the conjugate is termed as ERY_Ab/Fe-MOF, which was used for development of dual mode sensor. For electrochemical sensing, SPCE was modified with ERY_Ab/ Fe-MOF and for optical sensing, fluorescence behaviour of ERY_Ab/ Fe-MOF solution was monitored in presence of ERY. This was the first MOF based dual mode sensor for ERY antibiotic. The dual sensor was able to detect ERY antibiotics upto trace levels and the response is better than present ERY sensors.

Figure 4 Schematic of Fe-MOF based electrochemical-fluorescent bio-sensing of erythromycin antibiotic

Apart from this, during my Ph.D., I was also involved in the synthesis and characterization of different porous, electro-active, and fluorescent materials viz. activated carbon, gold nanoparticles, 2D materials and their composites with MOFs, etc. and explored their application horizon for environmental pollutant detection and remediation. Some of the research on these materials is also published in SCI-indexed journals and presented in various international conferences. For Ph.D. coursework, I have also completed a project work entitled “Removal of surfactants from laundry wastewater.” In this project, waste organic material-derived activated carbon was used to remove surfactants from laundry wastewater.

Research Activities

Poster presentation

• Reetu Rani, Kei Toda, Shin Ichi Ohira
  Utilizing Zirconium based Metal Organic Framework for Water Remediation Applications
  The 18^th IROAST Symposium (21^st Nov, 2023)

• Reetu Rani, Kei Toda, Shin Ichi Ohira
  Adsorption studies of alkali and alkaline earth metal ions on zirconium metal–organic frameworks
  The 9th Asian Conference on Coordination Chemistry (ACCC9) in Bangkok, Thailand (19^th -22^nd Feb, 2024)
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