No abstract

Protein-based hydrogel biomaterials provide a platform for different biological applications, including the encapsulation and stabilization of different biomolecules. These hydrogel properties can be modulated by controlling the design parameters to match specific needs; thus, multicomponent hydrogels have distinct advantages over singlecomponent hydrogels due to their enhanced versatility. Here, silk fibroin and γ-prefoldin chaperone protein based composite hydrogels were prepared and studied. Different ratios of the proteins were chosen, and the hydrogels were prepared by enzyme-assisted cross-linking. The secondary structure of the two proteins, dityrosine bond formation, and mechanical properties were assessed. The results obtained can be used as a platform for the rational design of composite thermostable hydrogel biomaterials to facilitate protection (due to hydrogel mechanics) and retention of bioactivity (e.g., of enzymes and other biomolecules) due to chaperone-like properties of γ-prefoldin.

Continuous monitoring of biochemical analytes like oxygen is of interest in biomedicine to provide insight into physiology and health. Silk-protein biomaterials are particularly useful as the scaffold material in oxygen sensors due to silk's unique amphiphilic chemistry, which promotes noncovalent stabilization of the protein and additives in aqueous environments. Silk films containing a water-insoluble oxygen-sensing chromophore, Pd (II) tetramethacrylated benzoporphyrin (PdBMAP), are evaluated as optical oxygen sensors in vitro and in vivo. These silk-chromophore composites are stabilized by the self-assembled, physically crosslinked protein network. The deaerated phosphorescence lifetime (τ m,0 ≈300 µs) of the chromophore in vitro is quenched to 50% of its initial value at ≈31 µm dissolved oxygen, indicating sensing functionality within physiological ranges of oxygen. In vitro enzymatic degradation of the silk films with and without the chromophore is demonstrated. The silkchromophore composite films are cytocompatible in vitro, biocompatible in vivo upon implantation in rats, and displayed mechanical properties suitable for subcutaneous implantation. Further, the films maintain oxygen-sensing function in vivo and demonstrate real-time sensing capabilities throughout various physiological states (i.e., hyperoxia, normoxia, and hypoxia).

The field of tissue engineering has evolved from its early days of engineering tissue substitutes to current efforts at building human tissues for regenerative medicine and mechanistic studies of tissue disease, injury, and regeneration. Advances in bioengineering, material science, and stem cell biology have enabled major developments in the field. In this perspective, we reflect on the September 2021 virtual Next Generation Tissue Engineering symposium and trainee workshop, as well as our projections for the field over the next 15 years.

used or studied as delivery platforms for therapeutic agents. [5][6][7] With non-pressurized systems, the dose of active ingredient is delivered through a metered-dose with a pump. [8] In contrast, pressurized systems, also known as aerosols, depend on the power of compressed or liquefied gas to expel the ingredients from the container. [9] These non-pressurized spray types are attractive systems for topical and systemic delivery of therapeutic agents due to their good reproducibility, and inexpensive and convenient characteristics, allowing for easy and ready to use by patients as well as physicians in any setting. Thus, these spray techniques have been explored as therapeutic delivery systems via localized routes of administration, including nasal, [10][11][12] oral, [13][14][15] and dermal. [1,16,17] Liquid sprays are effective in delivering relevant dosage of therapeutic agents via the nasal cavity, but often suffer from poor retention, dripping from the nose or draining rapidly followed by swallowing, which result in reduced bioavailability and impacting therapeutic response. [12,18] Aerosol spray systems have the potential to address these issues by offering rapid drug delivery to the respiratory tract while increasing the bioavailability of the drugs and minimizing the exposure of unaffected organs and tissues to the drugs. [19] Besides aerosols, recently, there has been growing interest in the use of fiber-based scaffolds, such as 1D, 2D, and 3D micro-and nanofibers, as carriers for drug delivery due to their remarkable advantages in controlling drug release rate by varying composition and structure (e.g., micro-or macro-), [20,21] allowing for low initial drug release burst rate compared to spherical carriers and controlled zeroorder drug release profiles. [22][23] Moreover, fiber morphologies provide distinct features, including high porosity, large surface area-to-volume ratio, and ease of functionalization with bioactive molecules, such as enzymes and growth factors, making them promising candidates as scaffolds for tissue engineering and regenerative medicine. [21,24] For in situ production of particles and fibers, a portable handheld electrohydrodynamic multi-needle device was used and by varying the operating parameters, such as the applied voltage, the flow rate of the feed solution/suspension, and the distance between the nozzle A variety of artificial silk spinning approaches are attempted to mimic the natural spinning process found in silkworms and spiders, yet instantaneous silk fiber formation with hierarchical structure under physiological and ambient conditions without post-treatment procedures remains unaddressed. Here, this work reports a new strategy to fabricate silk protein-based aerosols and silk fibers instantaneously in situ using a spray device, avoiding complicated and costly advanced manufacturing techniques. The key to success is the instantaneous conformational transition of silk fibroin from random coil to β-sheet right before spraying by mixing silk and polyethylene glycol (P...