3D bioprinted functional skeletal muscle models have potential applications for studies of muscle wasting in cancer cachexia.

Acquired muscle diseases such as cancer cachexia are responsible for the poor prognosis of many patients suffering from cancer. In vitro models are needed to study the underlying mechanisms of those pathologies. Extrusion bioprinting is an emerging tool to emulate the aligned architecture of fibers while implementing additive manufacturing techniques in tissue engineering. However, designing bioinks that reconcile the rheological needs of bioprinting and the biological requirements of muscle tissue is a challenging matter. Here we formulate a biomaterial with dual crosslinking to modulate the physical properties of bioprinted models. We design 3D bioprinted muscle models that resemble the mechanical properties of native tissue and show improved proliferation and high maturation of differentiated myotubes suggesting that the GelMA-AlgMA-Fibrin biomaterial possesses myogenic properties. The electrical stimulation of the 3D model confirmed the contractile capability of the tissue and enhanced the formation of sarcomeres. Regarding the functionality of the models, they served as platforms to recapitulate skeletal muscle diseases such as muscle wasting produced by cancer cachexia. The genetic expression of 3D models demonstrated a better resemblance to the muscular biopsies of cachectic mouse models. Altogether, this biomaterial is aimed to fabricate manipulable skeletal muscle in vitro models in a non-costly, fast and feasible manner.

Universal guidelines for the conversion of proteins and dyes into functional nanothermometers.

In the last decade, technological advances in chemistry and photonics have enabled real-time measurement of temperature at the nanoscale. Nanothermometers, probes specifically designed to relay these nanoscale temperature changes, provide a high degree of temperature, temporal, and spatial resolution and precision. Several different approaches have been proposed, including microthermocouples, luminescence and fluorescence polarization anisotropy-based nanothermometers. Anisotropy-based nanothermometers excel in terms of biocompatibility because they can be built from endogenous proteins conjugated to dyes, minimizing any system perturbation. Moreover, the resulting fluorescent proteins can retain their native structure and activity while performing the temperature measurement, allowing precise temperature recordings from the native environment or during an enzymatic reaction in any given experimental system. To facilitate the future use of these nanothermometers in research, here we present a theoretical model that predicts the optimal sensitivity for anisotropy-based thermometers starting with any protein or dye, based on protein size and dye fluorescence lifetime. Using this model, most proteins and dyes can be converted to nanothermometers. The utilization of these nanothermometers by a broad spectrum of disciplines within the scientific community will bring new knowledge and understanding that today remains unavailable with current techniques.