3D Bioprinted Human Skin Model Recapitulating Native-like Tissue Maturation and Immunocompetence as an Advanced Platform for Skin Sensitization Assessment.

Physiologically-relevant in vitro skin models hold utmost importance for efficacy assessments of pharmaceutical and cosmeceutical formulations, offering valuable alternatives to animal testing. Here, we present an advanced immunocompetent three-dimensional (3D) bioprinted human skin model to assess skin sensitization. Initially, a photopolymerizable bioink is formulated using silk fibroin methacrylate, gelatin methacrylate, and photoactivated human platelet releasate. The developed bioink shows desirable physicochemical and rheological attributes for microextrusion bioprinting. The tunable physical and mechanical properties of bioink were modulated through variable photocuring time, aiding control over mechanoresponsive cellular behaviour. Thereafter, the bioink is utilized to 3D bioprint "sandwich type" skin construct where an artificial basement membrane supports a biomimetic epidermal layer on one side and a printed pre-vascularized dermal layer on the other side within a transwell system. The printed construct is further cultured in air-liquid interface for maturation. Immunofluorescence staining demonstrated a differentiated keratinocyte layer and dermal extracellular matrix (ECM)-remodelling by fibroblasts and endothelial cell innervation. The biochemical estimations and gene-expression analysis validate the maturation of the printed model. Incorporation of macrophages further enhances physiological relevance of the model. Our model effectively classifies skin irritative and non-irritative substances, thus establishing itself as a suitable pre-clinical screening platform for sensitization tests. This article is protected by copyright. All rights reserved.