Current and Future Engineering Strategies for ECMO Therapy.

Extracorporeal membrane oxygenation (ECMO) is a last resort therapy for patients with respiratory failure where the gas exchange capacity of the lung is compromised. Venous blood is pumped through an oxygenation unit outside of the body where oxygen diffusion into the blood takes place in parallel to carbon dioxide removal. ECMO is an expensive therapy which requires special expertise to perform. Since its inception, ECMO technologies have been evolving to improve its success and minimize the complications associated with it. These approaches aim for a more compatible circuit design capable of maximum gas exchange with minimal need for anticoagulants. This chapter summarizes the basic principles of ECMO therapy with the latest advancements and experimental strategies aiming for more efficient future designs.

Toxicological effects of zinc oxide nanoparticle exposure: an in vitro comparison between dry aerosol air-liquid interface and submerged exposure systems.

Engineered nanomaterials (ENMs) are increasingly produced and used today, but health risks due to their occupational airborne exposure are incompletely understood. Traditionally, nanoparticle (NP) toxicity is tested by introducing NPs to cells through suspension in the growth media, but this does not mimic respiratory exposures. Different methods to introduce aerosolized NPs to cells cultured at the air-liquid-interface (ALI) have been developed, but require specialized equipment and are associated with higher cost and time. Therefore, it is important to determine whether aerosolized setups induce different cellular responses to NPs than traditional ones, which could provide new insights into toxicological responses of NP exposure. This study evaluates the response of human alveolar epithelial cells (A549) to zinc oxide (ZnO) NPs after dry aerosol exposure in the Nano Aerosol Chamber for In Vitro Toxicity (NACIVT) system as compared to conventional, suspension-based exposure: cells at ALI or submerged. Similar to other studies using nebulization of ZnO NPs, we found that dry aerosol exposure of ZnO NPs via the NACIVT system induced different cellular responses as compared to conventional methods. ZnO NPs delivered at 1.0 µg/cm2 in the NACIVT system, mimicking occupational exposure, induced significant increases in metabolic activity and release of the cytokines IL-8 and MCP-1, but no differences were observed using traditional exposures. While factors associated with the method of exposure, such as differing NP aggregation, may contribute toward the different cellular responses observed, our results further encourage the use of more physiologically realistic exposure systems for evaluating airborne ENM toxicity.

Extracellular-Matrix-Reinforced Bioinks for 3D Bioprinting Human Tissue.

Recent advances in 3D bioprinting allow for generating intricate structures with dimensions relevant for human tissue, but suitable bioinks for producing translationally relevant tissue with complex geometries remain unidentified. Here, a tissue-specific hybrid bioink is described, composed of a natural polymer, alginate, reinforced with extracellular matrix derived from decellularized tissue (rECM). rECM has rheological and gelation properties beneficial for 3D bioprinting while retaining biologically inductive properties supporting tissue maturation ex vivo and in vivo. These bioinks are shear thinning, resist cell sedimentation, improve viability of multiple cell types, and enhance mechanical stability in hydrogels derived from them. 3D printed constructs generated from rECM bioinks suppress the foreign body response, are pro-angiogenic and support recipient-derived de novo blood vessel formation across the entire graft thickness in a murine model of transplant immunosuppression. Their proof-of-principle for generating human tissue is demonstrated by 3D bioprinting human airways composed of regionally specified primary human airway epithelial progenitor and smooth muscle cells. Airway lumens remained patent with viable cells for one month in vitro with evidence of differentiation into mature epithelial cell types found in native human airways. rECM bioinks are a promising new approach for generating functional human tissue using 3D bioprinting.

Clickable decellularized extracellular matrix as a new tool for building hybrid-hydrogels to model chronic fibrotic diseases in vitro.

Fibrotic disorders account for over one third of mortalities worldwide. Despite great efforts to study the cellular and molecular processes underlying fibrosis, there are currently few effective therapies. Dual-stage polymerization reactions are an innovative tool for recreating heterogeneous increases in extracellular matrix (ECM) modulus, a hallmark of fibrotic diseases in vivo. Here, we present a clickable decellularized ECM (dECM) crosslinker incorporated into a dynamically responsive poly(ethylene glycol)-α-methacrylate (PEGαMA) hybrid-hydrogel to recreate ECM remodeling in vitro. An off-stoichiometry thiol-ene Michael addition between PEGαMA (8-arm, 10 kg mol-1) and the clickable dECM resulted in hydrogels with an elastic modulus of E = 3.6 ± 0.24 kPa, approximating healthy lung tissue (1-5 kPa). Next, residual αMA groups were reacted via a photo-initiated homopolymerization to increase modulus values to fibrotic levels (E = 13.4 ± 0.82 kPa) in situ. Hydrogels with increased elastic moduli, mimicking fibrotic ECM, induced a significant increase in the expression of myofibroblast transgenes. The proportion of primary fibroblasts from dual-reporter mouse lungs expressing collagen 1a1 and alpha-smooth muscle actin increased by approximately 60% when cultured on stiff and dynamically stiffened hybrid-hydrogels compared to soft. Likewise, fibroblasts expressed significantly increased levels of the collagen 1a1 transgene on stiff regions of spatially patterned hybrid-hydrogels compared to the soft areas. Collectively, these results indicate that hybrid-hydrogels are a new tool that can be implemented to spatiotemporally induce a phenotypic transition in primary murine fibroblasts in vitro.

Fluorescent Patterns by Selective Grafting of a Telechelic Polymer.

The preparation of patterned ultrathin films (sub-10 nm) composed of end-anchored fluorescently labeled poly(methyl methacrylate) (PMMA) is presented. Telechelic PMMA was synthesized utilizing activator regenerated by electron transfer atom transfer radical polymerization and consecutively end-functionalized with alkynylated fluorescein by Cu-catalyzed azide-alkyne cycloaddition (CuAAC) "click" chemistry. The polymers were grafted via the α-carboxyl groups to silica or glass substrates pretreated with (3-aminopropyl)triethoxysilane (APTES). Patterned surfaces were prepared by inkjet printing of APTES onto glass substrates and selectively grafted with fluorescently end-labeled PMMA to obtain emissive arrays on the surface.