In vivo degradation kinetics of 3D scaffolds traced with a fluorescence marker

Abstract

In vivo scaffold degradation is one of the main points in tissue engineering. There are many studies on the in vitro estimation of scaffold degradation kinetics (Zhu et al. 2013; Costa-Pinto et al. 2014; Oliveira et al. 2014). However, in vivo assessment of this parameter remains a problem; and a new in vivo non-invasive imaging method is needed to reduce the number of surgical procedures. There are several approaches to solving this problem: biopolymer crosslinking with fluorescent dyes or nanoparticles, fluorophore encapsulation into material, development of auto fluorescent polymers. Auto fluorescent biodegradable materials are the most attractive because this approach requires no use of additional fluorescent agents, which cannot be homogeneously distributed within scaffolds. This leads to incorrect degradation kinetics values. Moreover, fluorescent agents are toxic and increase the burden on normally functioning organs and tissues (liver, kidney, spleen, etc.). We showed that two-photon polymerization (2PP) enables the fabrication of auto fluorescent biodegradable scaffolds, which can be observed in real-time via in vivo non-invasive methods. We used successfully this approach in our study and revealed that polylactide 2PP scaffolds possessed auto fluorescence and were implanted after cell seeding into C57/B16 mice. The in vivo degradation rates were assessed due to changes in fluorescence intensity in real time.