Printable Thermo- and Photo-stable Poly(D,L-lactide)/Carbon Nanodots Nanocomposites via Heterophase Melt-Extrusion Transesterification

We propose for the first time an one-pot synthesis of carbon nanodots-poly(D,L-lactide) (CDs-PLA) nanocomposites, obtained by a simple reactive melt-extrusion process involving polar surface groups of multicolor CDs and ester bonds of PLA chains. Apart from providing an excellent method to produce polyester-coated CDs, our protocol allows obtaining perfect PLA@CDs blends giving rise to homogeneous extruded PLA@CDs filaments (ePLA@CDs) suitable for 3D printing applications (e.g., additive manufacturing for biomaterials and biodegradable encoded polymer ink technology). We demonstrate that ePLA@CDs filaments can be used to build a huge range of fluorescent objects with increasing architectural complexity (from grids to orthopedic screws). The designed nanocomposite synergistically combines the brilliant optical properties of hydrophilic N,S-CDs with the known biodegradable and biocompatible properties of PLA. Indeed, CDs endow PLA with peculiar thermo- and photo-stable multicolor emission (from blue to NIR) as well as good printability, avoiding typical self-quenching phenomena of CDs in solid-state. Besides, the use of CDs as probe-filler assumes a multifunctional role improving water uptake, degradation rate and also increasing material-cell interactions in comparison with the plain PLA. Overall, our results pave the way for the design of fluorescent implants providing real-time localization and monitoring of degradation state via non-invasive fluorescence imaging.