Epithelialization of hydrogels achieved by amine functionalization and co-culture with stromal cells

The aim of this study was to develop a hydrogel which would be suitable for corneal cell re-epithelialization when used as a corneal implant. To achieve this, a series of hydrogels were functionalized with primary amines by post-polymerization reactions between amine compounds and glycidyl ether groups attached to the hydrogels. We report a strong correlation between the structure of the amine and the viability of stromal cells and epithelial cells cultured on these hydrogels. Subsequent co-culture of epithelial and stromal cells on the amine modified hydrogels allowed successful expansion of epithelial cells on surfaces functionalized with alkyl α–ω diamines with carbon chain lengths of between 3 and 6. Analysis of variance showed that corneal epithelial cells had a strong preference for surfaces functionalized by the reaction of excess 1,3 diaminopropane with units of glycidyl methacrylate compared to the reaction products of other amines (ammonia; 1,2-diaminoethane; 1,4-diaminobutane or 1,6-diaminohexane). We suggest this approach of amine functionalization combined with stromal/epithelial co-culture offers a promising new approach to achieving a secure corneal epithelium. Keywords: Epithelial cell

Versatile Preparation of Fluorescent Particles Based on Polyphosphazenes: From Micro- to Nanoscale

A series of intrinsically fluorescent hydrophobic and amphiphilic polyphosphazenes with ethyl tryptophan (EtTrp) and poly(N-isopropylacrylamide) (PNIPAAm) or poly(ethylene glycol) (PEG) as hydrophobic and hydrophilic segments, respectively, are synthesized. Depending on polymer composition and preparation procedure, particles with diameters ranging from micro- to nanoscale can be prepared successfully, which might be used as a visible tracer, both in 14vitro or in 14vivo, in drug- or gene-delivery systems, as well as in other biomedical studies such as diagnostic medicine and brain research. Most importantly, in combination with the flexible synthesis and versatile modification of polyphosphazene, this method provides a general protocol to engineer a broad range of fluorescent particles with different properties based on diverse polymers.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/57545/1/2081_ftp.pd

A bioprintable form of chitosan hydrogel for bone tissue engineering

Bioprinting can be defined as 3D patterning of living cells and other biologics by filling and assembling them using a computer-aided layer-by-layer deposition approach to fabricate living tissue and organ analogs for tissue engineering. The presence of cells within the ink to use a 'bio-ink' presents the potential to print 3D structures that can be implanted or printed into damaged/diseased bone tissue to promote highly controlled cell-based regeneration and remineralization of bone. In this study, it was shown for the first time that chitosan solution and its composite with nanostructured bone-like hydroxyapatite (HA) can be mixed with cells and printed successfully. MC3T3-E1 pre-osteoblast cell laden chitosan and chitosan-HA hydrogels, which were printed with the use of an extruder-based bioprinter, were characterized by comparing these hydrogels to alginate and alginate-HA hydrogels. Rheological analysis showed that all groups had viscoelastic properties. It was also shown that under simulated physiological conditions, chitosan and chitosan-HA hydrogels were stable. Also, the viscosity values of the bio-solutions were in an applicable range to be used in 3D bio-printers. Cell viability and proliferation analyses documented that after printing with bio-solutions, cells continued to be viable in all groups. It was observed that cells printed within chitosan-HA composite hydrogel had peak expression levels for early and late stages osteogenic markers. It was concluded that cells within chitosan and chitosan-HA hydrogels had mineralized and differentiated osteogenically after 21 days of culture. It was also discovered that chitosan is superior to alginate, which is the most widely used solution preferred in bioprinting systems, in terms of cell proliferation and differentiation. Thus, applicability and printability of chitosan as a bio-printing solution were clearly demonstrated. Furthermore, it was proven that the presence of bone-like nanostructuredHAin alginate and chitosan hydrogels improved cell viability, proliferation and osteogenic differentiation

Boron Mediated 2D And 3D Cultures Of Adipose Derived Mesenchymal Stem Cells

Boron (B), which is a beneficial bioactive element for human, has an increasing interest in tissue engineering for the last 5 years. However, the effective B concentration in cell culture is still unknown. The aim of the present study is to investigate in vitro osteogenic potential of mesenchymal stem cells, isolated from adipose tissue (AdMSCs), on boron containing 2D and 3D cell cultures. At first, the effects of B concentrations between 1 and 20 μg/mL were evaluated on the survival and osteogenic differentiation of AdMSCs cultured on 2D cell cultures. The 3D cultures were established by using chitosan (Ch) scaffolds prepared by freeze-drying and Ch scaffolds combined with hydroxyapatite (HAp) and B containing hydroxyapatite (B-HAp) that are produced by microwave-induced biomimetic method. The proliferation and osteogenic differentiation of AdMSCs on Ch, HAp/Ch and B-HAp/Ch scaffolds were investigated by in vitro cell culture studies. The results were evaluated with respect to cell viability, bone related ECM gene expressions, and cellular morphology. It was demonstrated that cellular functions of AdMSCs were enhanced by boron in both 2D and 3D cultures. Especially, B-HAp/Ch scaffolds, which have both osteoinductive and osteoconductive properties based on presence of B and HAp in its structure, promoted adhesion, proliferation and osteogenic differentiation of AdMSCs.PubMedWo

Highly Methacrylated Gelatin Bioink for Bone Tissue Engineering

Methacrylated gelatin (Gel-MA) is a commonly used biomaterial in bioprinting applications. The Gel-MA synthesis procedure is inadequate and needs to be improved, particularly from the point of optimization and efficacy. We report a significantly faster (by 5 min) and effective method to controllably synthesize Gel-MA using microwave energy (Mw at 1000 W power) with ≥90% degree of methacrylation (DM) even with the use of a very low concentration of methacrylic anhydride (MA). Rheological and mechanical analyses indicated that Gel-MA synthesized by Mw-assisted methacrylation enabled the formation of hydrogels that are more elastic and stronger and have a lower degradation rate (∼27% at 35 days) than Gel-MA synthesized by the conventional method. The viscosity values of the Gel-MA bioink were in the range applicable for use in 3D bioprinters. Additionally, Mw-assisted methacrylated Gel-MA hydrogels that have mechanically superior properties significantly enhanced the viability, attachment, proliferation, alkaline phosphatase (ALP) activity, mineral deposition, and mRNA expression levels of osteogenic genes of MC3T3-E1 preosteoblastic cells