In vivo and in vitro tracking of erosion in biodegradable materials using non-invasive fluorescence imaging

In vitro experiments of a biomaterial's degradability rarely predict its in vivo behaviour. It is now shown that tracking the hydrolytic and enzymatic erosion of model materials by non-invasive fluorescence imaging allows the prediction of in vivo erosion from in vitro data. The approach should enable rapid screening of erodable biomaterials. The design of erodible biomaterials relies on the ability to program the in vivo retention time, which necessitates real-time monitoring of erosion. However, in vivo performance cannot always be predicted by traditional determination of in vitro erosion 1 , 2 , and standard methods sacrifice samples or animals 3 , preventing sequential measures of the same specimen. We harnessed non-invasive fluorescence imaging to sequentially follow in vivo material-mass loss to model the degradation of materials hydrolytically (PEG:dextran hydrogel) and enzymatically (collagen). Hydrogel erosion rates in vivo and in vitro correlated, enabling the prediction of in vivo erosion of new material formulations from in vitro data. Collagen in vivo erosion was used to infer physiologic in vitro conditions that mimic erosive in vivo environments. This approach enables rapid in vitro screening of materials, and can be extended to simultaneously determine drug release and material erosion from a drug-eluting scaffold, or cell viability and material fate in tissue-engineering formulations.