In Situ Formation of Microgel Array Via Patterned Electrospun Nanofibers Promotes 3D Cell Culture and Drug Testing in a Microphysiological System

A microphysiological system (MPS) is recently emerging as a promising alternative to the classical preclinical models, especially animal testing. A key factor for the construction of MPS is to provide a biomimetic three-dimensional (3D) cellular microenvironment. However, it still remains a challenge to introduce extracellular matrix (ECM)-like biomaterials such as hydrogels and nanofibers in a precise and spatiotemporal manner. Herein, we report a strategy to fabricate a MPS combining both electrospun nanofibers and hydrogels. The in situ formation of microsized hydrogel (microgel) array in MPS is realized by patterning electrospun poly(l-lactic acid) (PLLA)/Ca²⁺ nanofibers via a solvent-loaded agarose stamp and injecting an alginate solution to trigger the quick ionic cross-linking between alginate and Ca²⁺ released from patterned nanofibers. The one-on-one integration of electrospun nanofibers and microgels not only provides a 3D cellular microenvironment in designated regions in MPS but also improves the stability of these microenvironments under dynamic culture. In addition, due to the biocompatible properties of an ionic cross-linking reaction, patterned cell array can be achieved simultaneously during the microgel formation process. A breast cancer model is then built in MPS by coculturing human breast cancer cells and human fibroblasts in microgel array, and its application in drug (cisplatin) testing is evaluated. Our data prove that MPS-MA offers a more precise platform for drug testing to evaluate the drug concentration, duration time, cancer microenvironment, etc, mainly due to its successful construction of the biomimetic 3D cellular microenvironment.

Fabrication of gelatin methacrylate/nanohydroxyapatite microgel arrays for periodontal tissue regeneration

INTRODUCTION

Periodontitis is a chronic infectious disease and is the major cause of tooth loss and other oral health issues around the world. Periodontal tissue regeneration has therefore always been the ultimate goal of dentists and researchers. Existing fabrication methods mainly focused on a top-down tissue engineering strategy in which several drawbacks remain, including low throughput and limited diffusion properties resulting from a large sample size. Gelatin methacrylate (GelMA) is a kind of photocrosslinkable and biocompatible hydrogel, with the capacities of enabling cell encapsulation and regeneration of functional tissues. Here, we developed a novel method to fabricate GelMA/nanohydroxylapatite (nHA) microgel arrays using a photocrosslinkable strategy. The viability, proliferation, and osteogenic differentiation and in vivo osteogenesis of human periodontal ligament stem cells (hPDLSCs) encapsulated in microgels were evaluated. The results suggested that such microgels provide great potential for periodontal tissue repair and regeneration.

METHODS

Microgel arrays were fabricated by blending different weight ratios of GelMA and nHA. hPDLSCs were encapsulated in GelMA/nHA microgels of various ratios for a systematic evaluation of cell viability, proliferation, and osteogenic differentiation. In vivo osteogenesis in nude mice was also studied.

RESULTS

The GelMA/nHA microgels exhibited appropriate microarchitecture, mechanical strength, and surface roughness, thus enabling cell adhesion and proliferation. Additionally, the GelMA/nHA microgels (10%/2% w/v) enhanced the osteogenic differentiation of hPDLSCs by elevating the expression levels of osteogenic biomarker genes, such as ALP, BSP, OCN, and RUNX2. In vivo ectopic transplantation results showed that GelMA/nHA microgels (10%/2% w/v) increased mineralized tissue formation with abundant vascularization, compared with the 1%, 3%, and the pure GelMA group.

CONCLUSION

The GelMA/nHA microgels (10%/2% w/v) facilitated hPDLSCs viability, proliferation, and osteogenic differentiation in vitro and further promoted new bone formation in vivo, suggesting that the GelMA/nHA microgels (10%/2% w/v) provide great potential for periodontal tissue regeneration.