In tissue engineering, microstructure and material composition of tissue scaffolds have major influences on the proliferation and differentiation of cells in the scaffolds. However, once tissue scaffolds implanted, it is extremely difficult to monitor the change of their microstructure and compositions during tissue regeneration. Here, we report how random lasing can be utilized to non-invasively monitor the structure and composition of scaffolds. We hypothesize that morphological and compositional change of silk fibroin (SF) scaffolds can be conveniently detected based on random lasing responses. Engineered SF scaffolds with hydroxyapatite (HAP) nanoparticles and controlled pore alignment were fabricated, and their random lasing responses were analyzed depending on the concentration of HAP nanoparticles and the degree of internal pore alignment. We also examined the real-time random lasing responses of porous SF scaffolds by applying a compressive force to the scaffolds. Introduction of HAP nanoparticles lowered the lasing thresholds and narrowed the random lasing (RL) width dramatically, which is likely due to the increase in heterogeneity in both refractive index and physical arrangement within the SF and HAP composites. The strong dependency of RL response on pore alignment was also measured and validated by numerical calculation with the finite element method (FEM). Finally, real-time monitoring of RL on compressed scaffolds demonstrated the possibility of using RL as a monitoring tool for structural change of SF scaffolds in vivo.

Harvesting photosynthetic electrons (PEs) from plant or algal cells can be a highly efficient and environmentally friendly way of generating renewable energy. Recent work on nanoelectrode insertion into algal cells has demonstrated the possibility to directly extract PEs from living algal cells with high efficiencies. However, the instability of the inserted cells limits the practicality of this technology. Here, the impact of nanoelectrode insertion on intracellular extraction of PEs is characterized with the goal of stabilizing algal cells after nanoelectrode insertion. Using nanoelectrodes < 500 nm in diameter, algal cells remained stable for over one week after insertion and continued to provide PEs through direct extraction by the inserted nanoelectrodes. After nanoelectrode insertion, a photosynthetic current density of 6 mA·cm^-2, which is several fold higher than the current densities attained using approaches based on isolated thylakoid membranes or photosystem Ⅰ complexes, was observed in the dark and during illumination at various light intensities.

Liquid-phase exfoliation (LPE) is an attractive method for the scaling-up of exfoliated MoS₂ sheets compared to chemical vapor deposition and mechanical cleavage. However, the MoS₂ nanosheet yield from LPE is too small for practical applications. We report a facile method for the scaling-up of exfoliated MoS₂ nanosheets using freeze-dried silk fibroin powders. Compared to MoS₂ dispersion in the absence of silk fibroin powder, sonicated MoS₂ dispersions with silk fibroin powder (MoS₂/Silk dispersion) show noticeably higher exfoliated MoS₂ nanosheet yields, with suspended MoS₂ concentrations in MoS₂/Silk dispersions sonicated for 2 and 5 h of 1.03 and 1.39 mg·mL^–1, respectively. The MoS₂ concentration in the MoS₂/Silk dispersion after centrifugation above 10, 000 rpm is more than four times that without the silk fibroin. The size of the dispersed silk fibroin is controlled by the change of centrifugation rate, showing the removal of silk fibroin above tens of micrometers in size after centrifugation at 2, 000 rpm. Size-controlled silk fibroin biomolecules combined with MoS₂ nanosheets are expected to increase the practical use of such materials in fields related to tissue engineering, biosensors and electrochemical electrodes. Atomic force microscopy and Raman spectroscopy provide the height of the MoS₂ nanosheets spin-cast from MoS₂ /Silk dispersions, showing thicknesses of 3–6 nm. X-ray photoelectron spectroscopy and X-ray diffraction indicate that the outermost surface layer of the hydrophobic MoS₂ crystals interact with oxygen-containing functional groups that exist in the hydrophobic part of silk fibroins. The amphiphilic properties of silk fibroin combined with the MoS₂ nanosheets stabilize dispersions by enhancing solvent-material interactions. The large quantities of exfoliated MoS₂ nanosheets suspended in the as-synthesized dispersions can be utilized for the fabrication of vapor and electrochemical devices requiring high MoS₂ nanosheets contents.