Non-enzymatic detection of urea using unmodified gold nanoparticles based aptasensor

Area of Science:

• Biotechnology
• Biosensing
• Analytical Chemistry

Background:

• Economically Motivated Adulteration (EMA) of food products necessitates robust detection methods for adulterants like urea.
• Existing urea detection methods can be complex, requiring extensive sample processing or enzymatic reactions.

Purpose of the Study:

• To develop a specific DNA aptamer for urea detection using the FluMag-SELEX method.
• To create a simple, non-enzymatic aptasensor for simultaneous dual readout (fluorescence and colorimetric) of urea.
• To validate the aptasensor's performance in detecting urea adulteration in milk.

Main Methods:

• Isolation of a urea-specific DNA aptamer via FluMag-SELEX.
• Characterization of aptamer-urea interactions using affinity assays, CD analysis, and melting curve analysis.
• Development of a dual readout aptasensor utilizing unmodified gold nanoparticles (AuNPs).

Main Results:

• A urea-specific DNA aptamer with a dissociation constant (Kd) of 232 nM was successfully isolated.
• The aptasensor demonstrated high selectivity for urea, with no interference from common milk adulterants.
• Linear correlation between urea concentration (20mM to 150mM) and aptasensor response, with a detection limit of 20mM.
• Comparable results to commercial urease-based methods were achieved.

Conclusions:

• The developed DNA aptamer and aptasensor provide a sensitive, selective, and user-friendly platform for urea detection.
• This non-enzymatic approach simplifies sample handling and analysis for detecting urea adulteration in milk.
• The aptasensor shows significant potential for quality control in the food industry to combat EMA.