3D printed chitosan dressing crosslinked with genipin for potential healing of chronic wounds

Recently, various additive manufacturing (3D printing) approaches have been employed to fabricate dressings such as film scaffolds that possess well defined architecture and orientation at the micro level. In this study, crosslinked chitosan (CH) based film matrices were prepared using 3D printing with genipin (GE) as a crosslinker, with glycerol (GLY) and poly ethylene glycol (PEG) as plasticizer. The 3D printed films were functionally characterized using (tensile, fluid handling, mucoadhesion, drug dissolution, morphological properties and cell viability as well physico-chemical characterization using scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction. CH-GE-PEG600 3D printed films having the ratio of 1:1 polymer: plasticizer was selected due to their appropriate flexibility. Fourier transform infrared results showed intermolecular interaction between CH, GE and PEG which was confirmed by X-ray diffraction showing amorphous matrix structure. In vitro mucoadhesion studies of CH-GE-PEG600 films showed the capability of the 3D printed film to adhere to the epithelial surface. Scanning electron microscopy images showed that the surface of the plasticised films were smooth indicating content uniformity of CH, GE and PEG whilst micro cracks in unplasticised films confirmed their brittle nature. Plasticised films also showed high swelling capacity which enhanced water absorption. Cytotoxicity (MTT) assay using human skin fibroblast cell lines demonstrated that more than 90% of cells were viable after 48 h confirming non-toxic nature of the 3D printed CH-GE-PEG600 films and therefore promising dressing for chronic wound healing applications

3D printed composite dressings loaded with human epidermal growth factor for potential chronic wound healing applications

(GE) or CH combined with collagen (COL) and loaded with epidermal growth factor (EGF). The films were characterized using texture analyzer (tensile, adhesion), swelling capacity, Xray diffraction-XRD, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy-SEM, drug dissolution, and MTT assay using human dermal fibroblasts. FTIR confirmed crosslinking between CH and GE, CH and COL as well as between CH and EGF while. XRD showed amorphous matrix of the films. Mucoadhesion studies showed the film’s’ ability to adhere to a model simulated wound surface. SEM demonstrated a smooth, homogenous surface indicating content uniformity. The swelling was higher for CH-GE than the CH-COL films while blank films swelled better than the EGF loaded films. EGF was initially released rapidly, reaching 100% in 2 h, subsequent sharp reduction till 5 h followed by sustained release till 72 h, while MTT assay showed greater than 90% cell viability after 48 h, confirming their biocompatibility. EGF loaded films showed higher cell proliferation than blank equivalents. Overall, the results showed the potential of CH based 3D printed films as suitable dressing platforms to deliver EGF directly to chronic wounds

Bioprinting and preliminary testing of highly reproducible novel bioink for potential skin regeneration

Three-dimensional (3D) bioprinting is considered as a novel approach in biofabricating cell-laden constructs that could potentially be used to promote skin regeneration following injury. In this study, a novel crosslinked chitosan (CH)–genipin (GE) bioink laden with keratinocyte and human dermal fibroblast cells was developed and printed successfully using an extruder-based bioprinter. By altering the composition and degree of CH–GE crosslinking, bioink printability was further assessed and compared with a commercial bioink. Rheological analysis showed that the viscosity of the optimised bioink was in a suitable range that facilitated reproducible and reliable printing by applying low pressures ranging from 20–40 kPa. The application of low printing pressures proved vital for viability of cells loaded within the bioinks. Further characterisation using MTT assay showed that cells were still viable within the printed construct at 93% despite the crosslinking, processing and after subjecting to physiological conditions for seven days. The morphological study of the printed cells showed that they were mobile within the bioink. Furthermore, the multi-layered 3D printed constructs demonstrated excellent self-supportive structures in a consistent manner

Bioprinting with live cells

One of the most significant developments in cell and developmental biology in recent years has been the incredible interest in the potential of stem cells in regenerative medicine. In spite of the ongoing political, ethical and scientific challenges, interest in the potential clinical utility of stem continues to increase. Given this, a book series that provides volumes that are didactic, or methods driven and that provide comprehensive and authoritative information is needed. The series will provide volumes covering emerging areas in Stem Cell Biology and Regenerative Medicine

Bioprinting

The main goal of tissue or organ engineering is to reconstruct a damaged or diseased tissue or organ with cells, biomaterials and bioactive molecules. Recently, many tissue engineering approaches are based on developing highly porous tissue scaffolds and seeding cells into the scaffold with or without biologically active molecules to reinstate damaged tissue or organ. Various additive manufacturing methods have been used successfully to develop scaffolds with controlled micro-architecture and geometry. However, scaffold-based approaches still face some challenges such as difficulty in seeding different cells spatially in a scaffold, limited vascularization and blood-vessel formation, and weak cell-adhesion to scaffold material. This chapter focuses on Bioprinting, a special additive manufacturing technique, for tissue/organ engineering. Bioprinting or biofabrication creates complex living and non-living biological products from living cells, biomolecules and biomaterials. Various bioprinting techniques are discussed and contrasted in this chapter

Bioprinting: application of additive manufacturing in medicine

The main goal of tissue or organ engineering is to reconstruct a damaged or diseased tissue or organ with cells, biomaterials and bioactive molecules. Recently, many tissue engineering approaches are based on developing highly porous tissue scaffolds and seeding cells into the scaffold with or without biologically active molecules to reinstate damaged tissue or organ. Various additive manufacturing methods have been used successfully to develop scaffolds with controlled micro-architecture and geometry. However, scaffold-based approaches still face some challenges such as difficulty in seeding different cells spatially in a scaffold, limited vascularization and blood-vessel formation, and weak cell-adhesion to scaffold material. This chapter focuses on Bioprinting, a special additive manufacturing technique, for tissue/organ engineering. Bioprinting or biofabrication creates complex living and non-living biological products from living cells, biomolecules and biomaterials. Various bioprinting techniques are discussed and contrasted in this chapter

Computational model-informed design and bioprinting of cell-patterned constructs for bone tissue engineering

Three dimensional (3D) bioprinting is a rapidly advancing tissue engineering technology that holds great promise for the regeneration of several tissues, including bone. However, to generate a successful 3D bone tissue engineering construct, additional complexities should be taken into account such as nutrient and oxygen delivery, which is often insufficient after implantation in large bone defects. We propose that a well-designed tissue engineering construct, that is, an implant with a specific spatial pattern of cells in a matrix, will improve the healing outcome. By using a computational model of bone regeneration we show that particular cell patterns in tissue engineering constructs are able to enhance bone regeneration compared to uniform ones. We successfully bioprinted one of the most promising cell-gradient patterns by using cell-laden hydrogels with varying cell densities and observed a high cell viability for three days following the bioprinting process. In summary, we present a novel strategy for the biofabrication of bone tissue engineering constructs by designing cell-gradient patterns based on a computational model of bone regeneration, and successfully bioprinting the chosen design. This integrated approach may increase the success rate of implanted tissue engineering constructs for critical size bone defects and also can find a wider application in the biofabrication of other types of tissue engineering constructs