Direct inkjet writing of polylactic acid/ß-tricalcium phosphate composites for bone tissue regeneration: A proof-of-concept study.

There is an ever-evolving need of customized, anatomic-specific grafting materials for bone regeneration. More specifically, biocompatible and osteoconductive materials, that may be configured dynamically to fit and fill defects, through the application of an external stimulus. The objective of this study was to establish a basis for the development of direct inkjet writing (DIW)-based shape memory polymer-ceramic composites for bone tissue regeneration applications and to establish material behavior under thermomechanical loading. Polymer-ceramic (polylactic acid [PLA]/ß-tricalcium phosphate [ß-TCP]) colloidal gels were prepared of different w/w ratios (90/10, 80/20, 70/30, 60/40, and 50/50) through polymer dissolution in acetone (15% w/v). Cytocompatibility was analyzed through Presto Blue assays. Rheological properties of the colloidal gels were measured to determine shear-thinning capabilities. Gels were then extruded through a custom-built DIW printer. Space filling constructs of the gels were printed and subjected to thermomechanical characterization to measure shape fixity (Rf) and shape recovery (Rr) ratios through five successive shape memory cycles. The polymer-ceramic composite gels exhibited shear-thinning capabilities for extrusion through a nozzle for DIW. A significant increase in cellular viability was observed with the addition of ß-TCP particles within the polymer matrix relative to pure PLA. Shape memory effect in the printed constructs was repeatable up to 4 cycles followed by permanent deformation. While further research on scaffold macro-/micro-geometries, and engineered porosities are warranted, this proof-of-concept study suggested suitability of this polymer-ceramic material and the DIW 3D printing workflow for the production of customized, patient specific constructs for bone tissue engineering.

3D bioprinting and microscale organization of vascularized tissue constructs using collagen-based bioink.

Bioprinting three-dimensional (3D) tissue equivalents have progressed tremendously over the last decade. 3D bioprinting is currently being employed to develop larger and more physiologic tissues, and it is of particular interest to generate vasculature in biofabricated tissues to aid better perfusion and transport of nutrition. Having an advantage over manual culture systems by bringing together biological scaffold materials and cells in precise 3D spatial orientation, bioprinting could assist in placing endothelial cells in specific spatial locations within a 3D matrix to promote vessel formation at these predefined areas. Hence, in the present study, we investigated the use of bioprinting to generate tissue-level capillary-like networks in biofabricated tissue constructs. First, we developed a bioink using collagen type-1 supplemented with xanthan gum (XG) as a thickening agent. Using a commercial extrusion-based multi-head bioprinter and collagen-XG bioink, the component cells were spatially assembled, wherein the endothelial cells were bioprinted in a lattice pattern and sandwiched between bioprinted fibroblasts layers. 3D bioprinted constructs thus generated were stable, and maintained structural shape and form. Post-print culture of the bioprinted tissues resulted in endothelial sprouting and formation of interconnected capillary-like networks within the lattice pattern and between the fibroblast layers. Bioprinter-assisted spatial placement of endothelial cells resulted in fabrication of patterned prevascularized constructs that enable potential regenerative applications in the future.

Hydro-Assisted Self-Regenerating Brominated N-Alkylated Thiophene Diketopyrrolopyrrole Dye Nanofibers-A Sustainable Synthesis Route for Renewable Air Filter Materials.

With rising global concerns over the alarming levels of particulate pollution, a sustainable air quality management is the need of the hour. Air filtration research has gained momentum in recent years. However, the research perspective is still blinkered toward formulating new fiber systems for the energy-intensive electrospinning process to fabricate high quality factor air filters. A holistic approach on sustainable air filtration models is still lacking. The air filter model presented in this work uses a simple process involving water-induced self-organization and self-regeneration of nanofibers, and an easy recycling route after the filter life that not only facilitates reuse of the microfibrous scaffold holding the nanofibers but also allows renewal of nanofibers. Three generations of air filters are fabricated and tested, all having high particulate matter (PM)-adsorbing tendency, high filtration efficiency (>95%), and high Young's modulus (≈5 GPa). The renewable air filters offer a sustainable alternative to the present cost-intensive electrospun air filters.