Culturing cancer cells in a three-dimensional (3D) environment better recapitulates in vivo conditions by mimicking cell-to-cell interactions and mass transfer limitations of metabolites, oxygen, and drugs. Recent drug studies have suggested that a high rate of preclinical and clinical failures results from mass transfer limitations associated with drug entry into solid tumors that 2D model systems cannot predict. Droplet microfluidic devices offer a promising alternative to grow 3D spheroids from a small number of cells to reduce intratumor heterogeneity, which is lacking in other approaches. Spheroids were generated by encapsulating cells in novel thiol–acrylate (TA) hydrogel scaffold droplets followed by on-chip isolation of single droplets in a 990- or 450-member trapping array. The TA hydrogel rapidly (∼35 min) polymerized on-chip to provide an initial scaffold to support spheroid development followed by a time-dependent degradation. Two trapping arrays were fabricated with 150 or 300 μm diameter traps to investigate the effect of droplet size and cell seeding density on spheroid formation and growth. Both trapping arrays were capable of ∼99% droplet trapping efficiency with ∼90% and 55% cellular encapsulation in trapping arrays containing 300 and 150 μm traps, respectively. The oil phase was replaced with media ∼1 h after droplet trapping to initiate long-term spheroid culturing. The growth and viability of MCF-7 3D spheroids were confirmed for 7 days under continuous media flow using a customized gravity-driven system to eliminate the need for syringe pumps. It was found that a minimum of 10 or more encapsulated cells are needed to generate a growing spheroid while fewer than 10 parent cells produced stagnant 3D spheroids. As a proof of concept, a drug susceptibility study was performed treating the spheroids with fulvestrant followed by interrogating the spheroids for proliferation in the presence of estrogen. Following fulvestrant exposure, the spheroids showed significantly less proliferation in the presence of estrogen, confirming drug efficacy.
While comparatively few scholarly studies exist on podcast advertising, market research substantiates the effectiveness of podcast advertisements. This academic study probed podcast listeners’ attitudes toward podcast advertising and motivations for consumer actions through survey research with 1714 respondents. Extending past research on attitudes toward advertising within a medium (Aam), consumer action, and listener preference for host-read podcast advertisements, this study proposes a theoretical framework that seeks to contribute to a fundamental understanding of how listeners interact with and process podcast advertising. Scale development included modifying existing scales for other media as well as original scale development using qualitative methods that were tested for validity and internal consistency. Results from the survey revealed that: (1) Podcast listeners have favorable attitudes toward podcast advertising, particularly host-read advertisements; (2) Podcast listeners are motivated by functional and socio-emotional reasons for consumer actions, which correlate with positive attitudes toward podcast advertising; and (3) The podcast consumption levels of listeners are moderate predictors of their attitudes toward podcast advertising and subsequent consumer action, while gender and age are weaker predictors.
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