Paper-Based Enzymatic Colorimetric Assay for Rapid Malathion Detection

Area of Science:

• Biochemistry
• Analytical Chemistry
• Materials Science

Background:

• Paper-based biosensors offer low-cost, on-site analysis capabilities.
• Enzyme immobilization on paper is crucial for sensitive analyte detection but remains challenging.
• High apparent enzyme activity is desirable for efficient biosensing.

Purpose of the Study:

• To develop an improved method for immobilizing a malathion-degrading enzyme (PoOPH_M9) on paper.
• To enhance the apparent activity and stability of the immobilized enzyme.
• To create a rapid, paper-based colorimetric sensor for malathion detection.

Main Methods:

• Conjugation of Pluronic F127 (PF127)-poly(acrylic acid) with the PoOPH_M9 enzyme.
• Immobilization of the enzyme conjugate onto paper substrates.
• Colorimetric detection of malathion using smartphone image analysis.
• Validation of the sensor with contaminated water, plant, and apple samples.

Main Results:

• The PF127-poly(acrylic acid)-PoOPH_M9 conjugate significantly improved enzyme retention and activity.
• The immobilized enzyme exhibited a two-fold increase in V_max compared to controls without PF127.
• Rapid colorimetric detection of malathion was achieved within 5 minutes over a concentration range of 0.1-50 mM.
• Successful analysis of malathion in real-world samples (water, plant, apple) was demonstrated.

Conclusions:

• The developed PF127-poly(acrylic acid)-PoOPH_M9 paper offers a promising platform for sensitive and rapid on-site malathion detection.
• This approach enhances enzyme activity and stability for improved biosensor performance.
• The method facilitates the analysis of malathion contamination in various environmental and food samples.