Implantable photonic crystal for reflection-based optical sensing of biodegradation

Biodegradable inverse opal (IoPPC) was synthesized from a multifunctional carboxylic acid and polyols by colloidal crystal templating. The IoPPC was prepared by infiltration of the monomer solution into interparticle voids of silica colloidal crystal template, polycondensation of the infiltrated film, and removal of the template. The synthesized IoPPC was characterized by infrared absorption, X-ray diffraction measurements, differential scanning calorimetry, and thermogravimetry/mass spectrometry analysis. In order to clarify the effect of biodegradation on the inverse opal structure and the optical reflection property, the IoPPC was implanted in subcutaneous tissue of the lower back of three mice (ICR, 10 weeks, female). After the 2 weeks implantation, fragmented samples were harvested from the implant location and investigated by scanning electron microscope observations and optical reflection measurements. It was found that the reflection peak for the harvested samples decayed from that for the sample without implantation. Such a spectral change is considered to be attributed to the deterioration of the regularity of the inverse opal structures through biodegradation. The finding of this study will serve in the development of reflection-based sensing in various biomedical applications.