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- ItemLighting the Path: Light Delivery Strategies to Activate Photoresponsive Biomaterials In Vivo(Weinheim : Wiley-VCH, 2021) Pearson, Samuel; Feng, Jun; del Campo, AránzazuPhotoresponsive biomaterials are experiencing a transition from in vitro models to in vivo demonstrations that point toward clinical translation. Dynamic hydrogels for cell encapsulation, light-responsive carriers for controlled drug delivery, and nanomaterials containing photosensitizers for photodynamic therapy are relevant examples. Nonetheless, the step to the clinic largely depends on their combination with technologies to bring light into the body. This review highlights the challenge of photoactivation in vivo, and presents strategies for light management that can be adopted for this purpose. The authors’ focus is on technologies that are materials-driven, particularly upconversion nanoparticles that assist in “direct path” light delivery through tissue, and optical waveguides that “clear the path” between external light source and in vivo target. The authors’ intention is to assist the photoresponsive biomaterials community transition toward medical technologies by presenting light delivery concepts that can be integrated with the photoresponsive targets. The authors also aim to stimulate further innovation in materials-based light delivery platforms by highlighting needs and opportunities for in vivo photoactivation of biomaterials. © 2021 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH.
- ItemManual Versus Microfluidic-Assisted Nanoparticle Manufacture: Impact of Silk Fibroin Stock on Nanoparticle Characteristics(Washington, DC : ACS Publications, 2020) Solomun, Jana I.; Totten, John D.; Wongpinyochit, Thidarat; Florence, Alastair J.; Seib, F. PhilippSilk has a long track record of clinical use in the human body, and new formulations, including silk nanoparticles, continue to reveal the promise of this natural biopolymer for healthcare applications. Native silk fibroin can be isolated directly from the silk gland, but generating sufficient material for routine studies is difficult. Consequently, silk fibroin, typically extracted from cocoons, serves as the source for nanoparticle formation. This silk requires extensive processing (e.g., degumming, dissolution, etc.) to yield a hypoallergenic aqueous silk stock, but the impact of processing on nanoparticle production and characteristics is largely unknown. Here, manual and microfluidic-assisted silk nanoparticle manufacturing from 60-and 90-min degummed silk yielded consistent particle sizes (100.9-114.1 nm) with low polydispersity. However, the zeta potential was significantly lower (P < 0.05) for microfluidic-manufactured nanoparticles (-28 to-29 mV) than for manually produced nanoparticles (-39 to-43 mV). Molecular weight analysis showed a nanoparticle composition similar to that of the silk fibroin starting stock. Reducing the molecular weight of silk fibroin reduced the particle size for degumming times ≤30 min, whereas increasing the molecular weight polydispersity improved the nanoparticle homogeneity. Prolonged degumming (>30 min) had no significant effect on particle attributes. Overall, the results showed that silk fibroin processing directly impacts nanoparticle characteristics. Copyright © 2020 American Chemical Society.
- ItemStructural and Chemical Hierarchy in Hydroxyapatite Coatings(Basel : MDPI, 2020) Gross, Karlis A.; Petzold, Christiane; Pluduma-LaFarge, Liene; Kumermanis, Maris; HAugen, Håvard J.Hydroxyapatite coatings need similarly shaped splats as building blocks and then a homogeneous microstructure to unravel the structural and chemical hierarchy for more refined improvements to implant surfaces. Coatings were thermally sprayed with differently sized powders (20–40, 40–63 and 63–80 µm) to produce flattened homogeneous splats. The surface was characterized for splat shape by profilometry and Atomic force microscopy (AFM), crystal size by AFM, crystal orientation by X-ray diffraction (XRD) and structural variations by XRD. Chemical composition was assessed by phase analysis, but variations in chemistry were detected by XRD and Raman spectroscopy. The resulting surface electrical potential was measured by Kelvin probe AFM. Five levels of structural hierarchy were suggested: the coating, the splat, oriented crystals, alternate layers of oxyapatite and hydroxyapatite (HAp) and the suggested anion orientation. Chemical hierarchy was present over a lower range of order for smaller splats. Coatings made from smaller splats exhibited a greater electrical potential, inferred to arise from oxyapatite, and supplemented by ordered OH− ions in a rehydroxylated surface layer. A model has been proposed to show the influence of structural hierarchy on the electrical surface potential. Structural hierarchy is proposed as a means to further refine the properties of implant surfaces.
- ItemElectrically Conductive and 3D-Printable Oxidized Alginate-Gelatin Polypyrrole: PSS Hydrogels for Tissue Engineering(Weinheim : Wiley-VCH, 2021) Distler, Thomas; Polley, Christian; Shi, Fukun; Schneidereit, Dominik; Ashton, Mark D.; Friedrich, Oliver; Kolb, Jürgen F.; Hardy, John G.; Detsch, Rainer; Seitz, Hermann; Boccaccini, Aldo R.Electroactive hydrogels can be used to influence cell response and maturation by electrical stimulation. However, hydrogel formulations which are 3D printable, electroactive, cytocompatible, and allow cell adhesion, remain a challenge in the design of such stimuli-responsive biomaterials for tissue engineering. Here, a combination of pyrrole with a high gelatin-content oxidized alginate-gelatin (ADA-GEL) hydrogel is reported, offering 3D-printability of hydrogel precursors to prepare cytocompatible and electrically conductive hydrogel scaffolds. By oxidation of pyrrole, electroactive polypyrrole:polystyrenesulfonate (PPy:PSS) is synthesized inside the ADA-GEL matrix. The hydrogels are assessed regarding their electrical/mechanical properties, 3D-printability, and cytocompatibility. It is possible to prepare open-porous scaffolds via bioplotting which are electrically conductive and have a higher cell seeding efficiency in scaffold depth in comparison to flat 2D hydrogels, which is confirmed via multiphoton fluorescence microscopy. The formation of an interpenetrating polypyrrole matrix in the hydrogel matrix increases the conductivity and stiffness of the hydrogels, maintaining the capacity of the gels to promote cell adhesion and proliferation. The results demonstrate that a 3D-printable ADA-GEL can be rendered conductive (ADA-GEL-PPy:PSS), and that such hydrogel formulations have promise for cell therapies, in vitro cell culture, and electrical-stimulation assisted tissue engineering. © 2021 The Authors. Advanced Healthcare Materials published by Wiley-VCH GmbH
- ItemPolymer Hydrogels to Guide Organotypic and Organoid Cultures(Weinheim : Wiley-VCH, 2020) Magno, Valentina; Meinhardt, Andrea; Werner, CarstenHuman organotypic and organoid cultures provide increasingly life-like models of tissue/organ development and disease, enable more realistic drug screening, and may ultimately pave the way for new therapies. A broad variety of extracellular matrix-based or inspired materials is instrumental in these approaches. In this review article, the foundations of the related materials design are summarized with an emphasis on the advantages and limitations of decellularized and reconstituted biopolymeric matrices as well as biohybrid and fully synthetic polymer hydrogel systems applied to enable specific organotypic and organoid cultures. Recent progress in the fabrication of defined hydrogel systems offering thoroughly tunable biochemical and biophysical properties is highlighted. Potentialities of hydrogel-based approaches to address the persisting challenges of organoid technologies, namely scalability, connectivity/integration, reproducibility, parallelization, and in situ monitoring are discussed. © 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim