In-vitro investigations of a pH- and ionic-strength-responsive polyelectrolytic hydrogel using a piezoresistive...

Area of Science:

• Biomedical Engineering
• Materials Science
• Chemical Engineering

Background:

• Environmental responsive hydrogels exhibit volume phase transitions in response to external stimuli like pH or ionic strength.
• These smart materials can convert chemical energy into mechanical energy, making them suitable for biochemical microsensors and Micro-Electro-Mechanical Systems (MEMS) devices.

Purpose of the Study:

• To investigate the use of a biocompatible polyelectrolytic hydrogel, poly(hydroxypropyl methacrylate-N,N-dimethylaminoethyl methacrylate-tetra-ethyleneglycol dimethacrylate) (HPMA-DMA-TEGDMA), as a sensitive element in piezoresistive biochemical sensors.
• To characterize the sensor's response to changes in pH and ionic strength for potential integration into microsensor applications.

Main Methods:

• Micro-fabricated silicon pressure sensor chips with integrated piezoresistors were utilized as transducers.
• The HPMA-DMA-TEGDMA hydrogel was employed as the environmental sensitive element.
• In-vitro measurements of sensor response to varying pH and ionic strength in phosphate-buffered saline (PBS) solutions were conducted.

Main Results:

• The hydrogel exhibited a sharp volume phase transition around physiological pH (7.4).
• Sensor sensitivity to pH was calculated using the Hill equation, and time-dependent responses to pH and ionic strength variations were recorded.
• Asymmetric swelling behavior and differing time constants were observed during swelling and deswelling cycles, attributed to hydrogel confinement within the sensor.

Conclusions:

• The developed piezoresistive sensor effectively utilizes a biocompatible hydrogel for detecting environmental stimuli like pH and ionic strength.
• The sensor demonstrates potential for sensitive biochemical detection, with distinct responses to environmental changes.
• Further investigation into the hydrogel-confinement effects is warranted to optimize sensor performance.