Photodegradable Hydrogel Matrices for Spatiotemporal Control of Bacteria Transport and Delivery

Area of Science:

• Biomaterials Science
• Microfluidics
• Synthetic Biology

Background:

• Stimuli-responsive hydrogels offer controlled degradation for advanced therapeutic applications.
• Photodegradable hydrogels can direct bacterial movement and tune delivery through spatiotemporal degradation control.

Purpose of the Study:

• To investigate the use of photodegradable hydrogels for controlling bacterial transport.
• To explore the impact of tunable hydrogel degradation on bacterial speed and directionality.
• To achieve controlled release of bacteria for therapeutic applications.

Main Methods:

• Hydrogels synthesized via Michael addition reactions between photodegradable poly(ethylene glycol) (PEG) macromers and PEG tetra-thiol cross-linkers in microfluidic channels.
• Spatiotemporal hydrogel degradation induced by patterned 365 nm light exposure.
• Characterization of hydrogel degradation using in situ fluorescence visualization.
• Monitoring of *Bacillus subtilis* movement and chemotaxis through degraded hydrogels using time-lapse fluorescence microscopy.

Main Results:

• Bacteria mean speed and directional change were tunable based on hydrogel photodegradation levels.
• A 2.6-fold difference in mean cell speed observed across partially degraded hydrogel regions.
• Minimal bacterial adhesion to partially degraded PEG hydrogels was confirmed.
• Controlled release profiles of bacteria achieved by altering speed and directionality through tunable degradation.

Conclusions:

• Photodegradable hydrogels provide a novel platform for spatiotemporal control of bacterial transport.
• Tunable hydrogel degradation enables precise manipulation of bacterial speed and directionality.
• These findings advance the use of PEG-based hydrogels as delivery vehicles for bacterial therapeutics and living material applications.