Inverse Opal Hydrogel Sensors for the Detection of Endospore Viability


Tara Sowrirajan


  • Adrian Ponce, Principal Investigator of the Ponce Lab at the Jet Propulsion Laboratory, California Institute of Technology
  • Heather McCaig, Postdoctoral Researcher at the Ponce Lab at the Jet Propulsion Laboratory, California Institute of Technology

Endospores are considered one of the toughest life forms, and their hardiness makes them ideal as biological indicators of sterility for applications such as healthcare, food safety, and spacecraft assembly. Uniquely, endospores contain high concentrations of dipicolinic acid (DPA), which is released upon endospore germination. This research develops a new method to detect endospore viability through the release of DPA. Created from a microstructured hydrogel, the sensor expresses a visible color change upon exposure to DPA, resulting in rapid, low-cost detection of live endospores independent of external equipment. Inverse opal hydrogel photonic crystal sensors were synthesized by creating a polymer colloidal crystal with polystyrene beads (220 nm). The interstitial space was infiltrated with a pre-polymerization solution, including DPA, to allow for molecular imprinting, followed by photopolymerization to form the hydrogel. A solution of pyridine was used for template removal and DPA dissolution. The remaining inverse opal hydrogel sensor was exposed to solutions of varying pH and aqueous solutions of DPA. The color change will be characterized through UV-Vis spectroscopy to determine concentration detection limits of DPA and sensor response time. The minimum detectable number of endospores as measured by color change of the sensor will be determined.

Presented by:


Saturday, November 23, 2013


9:55 AM — 10:10 AM


Science 208

Presentation Type:

Oral Presentation