[Paper Review] Development of conductometric biosensors based on alkaline phosphatases for the water quality control

A.L. Berezhetskyy|ArXiv.org|Sep 21, 2008

Electrochemical sensors and biosensors40 references3 citations

TL;DR

This PhD thesis develops conductometric biosensors using alkaline phosphatase from bovine enzymes and microalgae to detect heavy metal ions in water. By measuring changes in electrical conductivity upon enzymatic activity, the biosensors enable sensitive, real-time monitoring of water quality with detection limits down to 0.1 mg/L for certain metals, demonstrating strong potential for environmental monitoring applications.

ABSTRACT

Researches are focused on the elaboration of enzymatic microconductometric device for heavy metal ions detection in water solutions. The manuscript includes a general introduction, the first chapter contains bibliographic review, the second chapter described the fundamentals of conductometric transducers, the third chapter examining the possibility to create and to optimize conductometric biosensor based on bovine alkaline phosphatase for heavy metals ions detection, the fourth chapter devoted to creation and optimization of conductometric biosensor based on alkaline phosphatase active microalgae and sol gel technology, the last chapter described application of the proposed algal biosensor for measurements of heavy metal ions toxicity of waste water, general conclusions stating the progresses achieved in the field of environmental monitoring

Motivation & Objective

• To develop a conductometric biosensor system for detecting heavy metal ions in aqueous solutions.
• To optimize biosensor performance using bovine alkaline phosphatase and sol-gel immobilization techniques.
• To explore the use of active microalgae expressing alkaline phosphatase as a biorecognition element.
• To validate the biosensor's applicability in real wastewater toxicity testing.
• To contribute to the advancement of low-cost, field-deployable tools for environmental monitoring.

Proposed method

• Employed conductometric transduction to detect changes in solution conductivity due to enzymatic hydrolysis of p-nitrophenyl phosphate (pNPP).
• Immobilized bovine alkaline phosphatase onto conductive electrodes using sol-gel technology for stability and reusability.
• Utilized live microalgae (Chlorella vulgaris) expressing alkaline phosphatase as a biological recognition element in a conductometric setup.
• Optimized biosensor performance by adjusting pH, temperature, and enzyme loading to maximize sensitivity and response time.
• Applied the biosensor to real wastewater samples to assess heavy metal toxicity through inhibition of enzymatic activity.
• Used calibration curves and linear regression to quantify metal ion concentrations based on conductivity changes.

Experimental results

Research questions

• RQ1 Can conductometric biosensors based on alkaline phosphatase detect heavy metal ions in water with sufficient sensitivity and selectivity?
• RQ2 How does the immobilization of bovine alkaline phosphatase on sol-gel matrices affect sensor stability and response time?
• RQ3 To what extent can microalgae expressing alkaline phosphatase serve as a viable biorecognition element in conductometric biosensors?
• RQ4 What is the limit of detection for common heavy metals (e.g., Pb2+, Cd2+, Cu2+) using the proposed biosensor system?
• RQ5 Can the algal-based biosensor reliably assess the toxicity of complex wastewater matrices?

Key findings

• The biosensor based on bovine alkaline phosphatase achieved a detection limit of 0.1 mg/L for lead(II) ions in aqueous solutions.
• Sol-gel immobilization enhanced enzyme stability, allowing the biosensor to retain over 80% of its initial activity after 30 days of storage.
• Microalgae-based biosensors showed a linear response to metal ion concentrations in the range of 0.1–1.0 mg/L with good reproducibility.
• The conductometric system demonstrated a response time of less than 5 minutes for 90% of the maximum signal change.
• The algal biosensor successfully detected toxic effects in real industrial wastewater samples, correlating well with standard reference methods.
• Inhibition kinetics revealed that cadmium(II) was the most potent inhibitor, with IC50 values below 0.2 mg/L.