Biomimetic fiber assembled gradient hydrogel to engineer glycosaminoglycan enriched and mineralized cartilage: Anin vitrostudy

Abstract

The study investigated the potential of electrospun fiber assembled hydrogel, with physical gradients of chondroitin sulfate (CS) and sol-gel-derived bioactive glass (BG), to engineer hyaline and mineralized cartilage in a single 3D system. Electrospun poly(caprolactone) (PCL) fibers incorporated with 0.1% w/w of CS (CSL) and 0.5% w/w of CS (CSH), 2.4% w/w of BG (BGL) and 12.5% w/w of BG (BGH) were fabricated. The CS showed a sustained release up to 3 days from CSL and 14 days from CSH fibers. Chondrocytes secreted hyaline like matrix with higher sulfated glycosaminoglycans (sGAG), collagen type II and aggrecan on CSL and CSH fibers. Mineralization was observed on BGL and BGH fibers when incubated in simulated body fluid for 14 days. Chondrocytes cultured on these fibers secreted a mineralized matrix that consisted of sGAG, hypertrophic proteins, collagen type X, and osteocalcin. The CS and BG incorporated PCL fiber mats were assembled in an agarose-gelatin hydrogel to generate a 3D hybrid scaffold. The signals in the fibers diffused and generated continuous opposing gradients of CS (chondrogenic signal) and BG (mineralization) in the hydrogel. The chondrocytes were encapsulated in hybrid scaffolds; live dead assay at 48 h showed viable cells. Cells maintained their phenotype and secreted specific extracellular matrix (ECM) in response to signals within the hydrogel. Continuous opposing gradients of sGAG enriched and mineralized ECM were observed surrounding each cell clusters on gradient hydrogel after 14 days of culture in response to the physical gradients of raw materials CS and BG. A construct with gradient mineralization might accelerate integration to subchondral bone during in vivo regeneration.

3D printing for the design and fabrication of polymer-based gradient scaffolds

“…However, methods that can visualize as well as quantify the existence of the gradient are still of importance. In cases where the chemical composition of a scaffold is varied spatially, thermogravimetric analysis (TGA) [77] or Fourier transform infrared spectroscopy (FTIR) has been used to successfully compare chemical constituents [75, 76]. TGA was used to effectively quantify the gradient of bioactive glass (BG) present in the BG PCL fibers incorporated into the single scaffold to support hyaline and mineralized cartilage.…”

“…Assays to assess the gradient should measure these specific outcomes in order to form conclusions on the added value of the scaffold. For example, one study in osteochondral regeneration developed agarose-gelatin hydrogel scaffolds with a gradient concentration of chondroitin sulfate (CS) (chondrogenic signal) and BG (bone mineralization signal) incorporated into PCL fiber mats [77]. Chondrocytes seeded onto these scaffolds secreted a hyaline like matrix with higher amount sulfated glycosaminoglycans (sGAG), collagen type II, and aggrecan CS fibers than on BG fibers.…”

“…Conversely, mineralization was observed on BG fibers. The observation of continuous, opposing gradients of sGAG enriched (chondrogenic) and mineralized ECM (osteoblastic) was observed surrounding each cell clusters on gradient hydrogel after 14 days of culture, in response to the physical gradients of raw materials CS and BG [77]. This is an example of how cellular response can act as a bioassay to help prove the existence of a biochemical gradient.…”

Recent Progress of Fabrication of Cell Scaffold by Electrospinning Technique for Articular Cartilage Tissue Engineering

“…Bioprinting and electrospinning were combined to fabricate biomimetic scaffolds for cartilage tissue engineering [ 13 ]. Electrospun fiber assembled hydrogel was also utilized for supplementation of glycosaminoglycan enriched and mineralized cartilage [ 18 ].…”

“…Fabricating scaffolds with gradients of molecules and element particles for tissue engineering has drawn substantial attention. Chondroitin sulfate (CS) and gentamycin sulfate (GS) gradients have been achieved with mineralized cartilage [ 18 ] and spatiotemporal drug release [ 35 ]. Ramalingam et al reported a scaffold with amorphous calcium phosphate nanoparticles (nACP) gradient by coelectrospinning.…”