Optical Control of Tissue Regeneration through Photostimulation of Organic Semiconducting Nanoparticles.

Next generation bioengineering strives to identify crucial cues that trigger regeneration of damaged tissues, and to control the cells that execute these programs with biomaterials and devices. Molecular and biophysical mechanisms driving embryogenesis may inspire novel tools to reactivate developmental programs in situ. Here nanoparticles based on conjugated polymers are employed for optical control of regenerating tissues by using an animal with unlimited regenerative potential, the polyp Hydra, as in vivo model, and human keratinocytes as an in vitro model to investigate skin repair. By integrating animal, cellular, molecular, and biochemical approaches, nanoparticles based on poly-3-hexylthiophene (P3HT) are shown able to enhance regeneration kinetics, stem cell proliferation, and biomolecule oxidation levels. Opposite outputs are obtained with PCPDTBT-NPs (Poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta [2,1-b;3,4-b'] dithiophene)-alt-4,7(2,1,3-benzothiadiazole)], causing a beneficial effect on Hydra regeneration but not on the migratory capability of keratinocytes. These results suggest that the artificial modulation of the redox potential in injured tissues may represent a powerful modality to control their regenerative potential. Importantly, the possibility to fine-tuning materials' photocatalytic efficiency may enable a biphasic modulation over a wide dynamic range, which can be exploited to augment the tissue regenerative capacity or inhibit the unlimited potential of cancerous cells in pathological contexts.

Seamless integration of bioelectronic interface in an animal model via in vivo polymerization of conjugated oligomers.

Leveraging the biocatalytic machinery of living organisms for fabricating functional bioelectronic interfaces, in vivo, defines a new class of micro-biohybrids enabling the seamless integration of technology with living biological systems. Previously, we have demonstrated the in vivo polymerization of conjugated oligomers forming conductors within the structures of plants. Here, we expand this concept by reporting that Hydra, an invertebrate animal, polymerizes the conjugated oligomer ETE-S both within cells that expresses peroxidase activity and within the adhesive material that is secreted to promote underwater surface adhesion. The resulting conjugated polymer forms electronically conducting and electrochemically active µm-sized domains, which are inter-connected resulting in percolative conduction pathways extending beyond 100 µm, that are fully integrated within the Hydra tissue and the secreted mucus. Furthermore, the introduction and in vivo polymerization of ETE-S can be used as a biochemical marker to follow the dynamics of Hydra budding (reproduction) and regeneration. This work paves the way for well-defined self-organized electronics in animal tissue to modulate biological functions and in vivo biofabrication of hybrid functional materials and devices.

Time-gated luminescence imaging of positively charged poly-l-lysine-coated highly microporous silicon nanoparticles in living Hydra polyp.

The development of non-toxic fluorescent agents alternative to heavy metal-based semiconductor quantum dots represents a relevant topic in biomedical research and in particular in the bioimaging field. Herein, highly luminescent Si─H terminal microporous silicon nanoparticles with µs-lived photoemission are chemically modified with a two step process and successfully used as label-free probes for in vivo time-gated luminescence imaging. In this context, Hydra vulgaris is used as model organism for in vivo study and validity assessment. The application of time gating allows to pursue an effective sorting of the signals, getting rid of the most common sources of noise that are fast-decay tissue autofluorescence and excitation scattering within the tissue. Indeed, an enhancement by a factor ~ 20 in the image signal-to-noise ratio can be estimated.