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Background: The cornea, a vital component of the human eye, plays a crucial role in maintaining visual clarity. Understanding its ultrastructural organization and cell distribution is fundamental for elucidating corneal physiology and pathology. This study comprehensively examines the microarchitecture of the hydrated human cornea using contrast-enhanced micro-computed tomography (micro-CT). Method: Fresh human corneal specimens were carefully prepared and hydrated to mimic their in vivo state. Contrast enhancement with Lugol's iodine-enabled high-resolution Micro-CT imaging. The cells' three-dimensional (3D) distribution within the cornea was reconstructed and analyzed. Results: The micro-CT imaging revealed exquisite details of the corneal ultrastructure, including the spatial arrangement of cells throughout its depth. This novel approach allowed for the visualization of cells' density and distribution in different corneal layers. Notably, our findings highlighted variations in cell distribution between non-hydrated and hydrated corneas. Conclusions: This study demonstrates the potential of contrast-enhanced micro-CT as a valuable tool for non-destructive, 3D visualization and quantitative analysis of cell distribution in hydrated human corneas. These insights contribute to a better understanding of corneal physiology and may have implications for research in corneal diseases and tissue engineering.

A multitude of autogenous/allogeneic and semi-synthetic bone graft materials have been developed to reconstruct the defective bone tissue but with high bio-cost and potential environmental pollution. With high calcium content and several trace elements, chicken eggshells are no longer considered as wastes but attractive sources of high-value-added biomaterials. This study used chicken eggshells and synthetic hydroxyapatite (HAp) to synthesize amorphous calcium phosphate (ACP) bone graft materials, namely Control and Eggshell. The physiochemical characteristics, biosafety, and immunocompatibility of synthetic ACP particles were inspected. Their osteogenic activity was further investigated in a novel osteoblastic spheroids model. Eggshell ACP particles exhibited ideal cytocompatibility compared to the control ACP and were more resistant to re-crystallization. In osteoblastic spheroids, Eggshell ACP mediated typical osteogenic mRNA profiles of MC-3T3-E1 cells, accompanied by the increased formation of mineralized nodules and boosted synthesis of ECM proteins represented by OPN and collagen I. This study establishes a promising technique to synthesize stable, safe, and osteoinductive ACP graft particles from eggshell waste. Furthermore, the osteoblastic spheroids constructed in the present study provide a more practical model for biomaterial research, which reflect the three-dimensional interaction between host bone tissue and graft materials more realistically.