Poloxamer 184 (L64)

3D hydrogel synthetic scaffold culture embeds cells, spheroids, organoids, or tissue fragments inside a hydrated crosslinked polymer network so that cells receive matrix and cell-cell cues in three dimensions rather than from a flat plastic surface. A literature-supported model protocol is PEG-4MAL hydrogel culture, in which four-arm maleimide-terminated PEG is functionalized with cysteine-containing adhesive peptides such as RGD and crosslinked with protease-degradable peptides such as GPQ-W; this creates a defined, modular scaffold that supports human organoid generation and culture. The readouts are scaffold-supported growth, morphology, lumen formation, budding, viability, proliferation, lineage-marker expression, and matrix-dependent expansion or differentiation; reported assays include transmitted-light imaging, immunofluorescence, in situ hybridization, qRT-PCR, and rheological characterization.

Infectious-disease experiments test how pathogens interact with host barriers, innate immune receptors, inflammatory signaling, pathogen replication, and tissue injury; pattern-recognition receptors such as TLRs, RIG-I-like receptors, NOD-like receptors, and inflammasomes detect microbial molecules and activate NF-κB, interferon, and cytokine responses. The central hypothesis is that infection severity reflects the balance between pathogen burden and host response: protective inflammation restricts pathogen growth, whereas excessive or mislocalized inflammation contributes to tissue damage and disease phenotype. Unresolved questions include which host pathways are protective versus pathogenic, why some infection models fail to translate to human disease, and which combined readouts best predict clinically relevant infection outcomes.

This protocol assesses dermal irritation using reconstructed human epidermis (RhE) models such as EpiDerm, EPISKIN, and SkinEthic RHE, in which a test substance is applied topically and tissue viability is measured after exposure; reduced viability reflects cytotoxic injury associated with skin irritation potential. The primary readout is MTT reduction, where viable cells convert tetrazolium salt into colored formazan measured by spectrophotometry; this signal is used as a quantitative viability endpoint for classifying irritant versus non-irritant responses. The historical in vivo comparator is the Draize rabbit skin irritation method, which scores erythema and edema after topical exposure, but validated RhE assays were developed to replace or reduce reliance on this animal-based endpoint.