Whole-Cell Biosensors: History, Principles, and Applications
Whole-cell biosensors represent a significant advancement in the field of biosensing, leveraging living cells as the biological component to detect and measure various environmental and biological parameters.
Historical Development
- 1975: First Microbial Biosensor: Divies designed the first microbial biosensor using Acetobacter xylinum and an oxygen electrode for ethanol detection. This marked the beginning of using microorganisms in biosensor technology[1][2][4].
Principles and Advantages
- Metabolic Pathways: Whole cells contain a complete metabolic aggregate of enzymes, cofactors, and coenzymes, enabling complex chemical reactions that can be harnessed for biosensing. These cells can self-regulate and recycle necessary substances, making them well-suited for detecting a wide range of analytes[3].
- Direct Effects on Living Cells: Whole-cell biosensors can measure direct effects on living cells, such as changes in respiratory activity, photosynthetic activity, or bioluminescence, due to environmental pollutants. This approach is more holistic than traditional methods, which often focus on individual compounds[2][5].
Types of Whole-Cell Biosensors
- Amperometric Devices: Microorganisms have been incorporated into amperometric devices to produce environmental biosensors. For example, eukaryotic algae have been used to monitor pollution in aquatic systems by measuring photosynthetic activity[2].
- Biochemical Oxygen Demand (BOD) Sensors: Pioneered in Japan, BOD sensors use immobilized microorganisms on the tip of an oxygen electrode to measure oxygen consumption over a few minutes, correlating this with BOD. This method is faster than the conventional 5-day test[2].
- Bioluminescent Organisms: Bioluminescent bacteria, engineered with lux genes, emit light in response to metabolic activity. This technology is versatile and provides real-time, nondestructive measurements of viability and the impact of various chemical, biological, and physical signals[2].
Applications
- Environmental Monitoring: Whole-cell biosensors are widely used for monitoring water and air quality. They can detect pollutants and measure their impact on living cells, providing a more comprehensive view of environmental health[1][2][4].
- Toxicity Assessment: These biosensors are effective in assessing the toxicity of various chemicals and mixtures. Bioluminescent bacteria, for example, can indicate the metabolic activity and viability of cells exposed to toxins[2].
- Industrial and Biotechnological Applications: Whole-cell biosensors can be used in biotechnological processes to monitor fermentation, detect contaminants, and optimize production conditions[3].
Technological Advances
- Genetically Engineered Cells: Advances in molecular biology have enabled the creation of genetically engineered cells with specific sensing capabilities. For instance, cells can be engineered to produce bioluminescence in response to specific analytes[2][4].
- Microfluidic and Chemostat Systems: Modern whole-cell biosensors often incorporate microfluidic systems and chemostats to maintain cell viability and ensure continuous monitoring. These systems allow for real-time measurements and can be integrated into portable devices[4].
Commercial and Clinical Impact
- BOD Sensors: Despite the lack of exact correlation with traditional BOD tests, BOD sensors have been widely adopted in Japan and other countries for rapid water quality assessment[2].
- Continuous Glucose Monitoring: Whole-cell biosensors have also influenced the development of continuous glucose monitoring systems (CGMS) for diabetes management. These systems, such as the MiniMed CGMS, have revolutionized glucose monitoring by providing continuous, real-time data
