Comparison of SERS pH probe responses after microencapsulation within hydrogel matrices

Area of Science:

• Biomedical Engineering
• Materials Science
• Analytical Chemistry

Background:

• Personalized medicine necessitates continuous monitoring of individual metabolite levels to detect health anomalies and assess medication responses.
• Implanted sensors are crucial for real-time metabolite tracking, requiring accuracy, long-term stability, and biocompatibility.

Purpose of the Study:

• To evaluate four types of hydrogels embedded with pH-sensitive sensors for their suitability in long-term implantation.
• Assessing sensor performance metrics including accuracy, sensitivity, reversibility, longevity, and dynamic response under various conditions.

Main Methods:

• Utilized Raman spectroscopy for calibrating pH-sensitive hydrogel sensors in static and dynamic pH environments.
• Evaluated sensor response times, consistency, and stability after five months of storage.

Main Results:

• All hydrogels enabled surface-enhanced Raman spectroscopy (SERS) sensors to respond to pH without interference, yielding consistent calibration curves.
• Hydrogel probes exhibited slow steady-state response times (several hours), varying among types.
• Poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogels demonstrated the greatest functional stability over five months without significant dynamic range degradation.

Conclusions:

• While all tested hydrogels are potential biocompatible hosts for SERS sensing, pHEMA offers superior long-term functional stability.
• Poly(ethylene glycol) hydrogels show the fastest pH response.
• Both pHEMA and poly(ethylene glycol) hydrogels, being covalently cross-linked and non-degradable, present advantages over sodium alginate for implantable sensor applications.