3D bioprinting of cells, tissues and organs
3D bioprinting has emerged as a promising new approach for fabricating complex biological constructs in the field of tissue engineering organic printing
and regenerative medicine. It aims to alleviate the hurdles of conventional tissue engineering methods by precise and controlled layer-by-layer assembly of biomaterials in a desired 3D pattern. The 3D bioprinting of cells, tissues, and organs Collection at Scientific Reports brings together a myriad of studies portraying the capabilities of different bioprinting modalities. This Collection amalgamates research aimed at 3D bioprinting organs for fulfilling demands of organ shortage, cell patterning for better tissue fabrication, and building better disease models. The discovery of a 3D printer dates back to early 1980s when Charles Hull, an American engineer, built the 1st 3D printer, capable of creating solid objects by following a computer-aided design (CAD). The printer deposited successive layers of an acrylic-based photopolymer which was then simultaneously crosslinked by UV light, thus creating a solid 3D object. This simple technology, called stereolithography (SLA), revolutionized the additive manufacturing industry. Gradually, by the late 1990s, 3D printing made its appearance in healthcare where surgeons began 3D printing dental implants, custom prosthetics, and kidney bladders. Subsequently the term ‘3D bioprinting’ emerged where the material being printed, called ‘bioink’1, consisted of living cells, biomaterials, or active biomolecules. Analogous to additive manufacturing, 3D bioprinting involves layer-by-layer deposition of bioink to create 3D structures, such as tissues and organ
3D bioprinting can be broadly categorized as either extrusion droplet or laser-based bioprinting. Extrusion based bioprinting employs mechanical, pneumatic or solenoid dispenser systems to deposit bioinks in a continuous form of filaments, while droplet based bioprinting relies on the generation of bioink droplets by thermal, acoustic or electrical stimulation. Laser based bioprinting utilizes laser power to 3D print structures such as in SLA by a photopolymerization principle. It can also be used for precise positioning of cells such as in laser direct-write and Laser Induced Forward Transfer (LIFT). The selection of “bioinks” for each of these different bioprinting modalities usually varies based on the ink’s rheology, viscosity, crosslinking chemistry, and biocompatibility. Extrusion based bioprinting primarily requires shear thinning bioinks while droplet or inkjet bioprinting needs materials with low viscosity. Over the past few years, the design and synthesis of bioinks has evolved to meet the increasing needs of new bioprintable materials. Significant advancements have also been made to integrate secondary techniques accompanying the above-mentioned modalities of bioprinting. For example, creating 3D structures with low viscosity bioinks has always been a challenge. To overcome this issue, such bioinks can now be extruded in a granular support bath containing yield stress hydrogels which solidify around the extruded structure and prevent it from collapsin part from organ printing, bioprinting is also being used to fabricate in-vitro tissue models for drug screening, disease modelling, and several other in-vitro applications.
The 3D bioprinting of cells, tissues and organs Collection at Scientific Reports is dedicated to this field of research. This collection clearly portrays the diverse applications of different bioprinting modalities and how they could be utilized for improving various aspects of healthcare. Kim et al. 3D printed a novel two-layered polycaprolactone (PCL) -based tubular tracheal gr his tracheal graft, seeded with induced pluripotent stem cell (iPSC) -derived mesenchymal (MSCs) and chondrocyte stem cells supported the regeneration of tracheal mucosa and cartilage in a rabbit model of a segmental tracheal defect. Galarraga et al. used a norbornene-modified hyaluronic acid (NorHA) macromer as a representative bioink for cartilage tissue engineering7. Printed structures containing MSCs, on long term culture, not only led to an increase in compressive moduli, but also expressed biochemical content similar to native cartilage tissue. Vidal et al. used 3D printed customized calcium phosphate scaffolds with and without a vascular pedicle to treat large bone defects in sheep hey used CT angioscan to scan the entire defect site and subsequently 3D print a personalized scaffold to anatomically fit the defect site. A bioink comprising decellularized matrix from mucosal and muscular layers of native esophageal tissues was used by Nam et al. to mimic the microenvironment of native esophagus cht et al. used gelatin based bioinks to study vasculogenesis in a bone-like microenvironm Kilian et al. used a calcium phosphate cement (CPC) and an alginate-methylcellulose based bioink containing primary chondrocytes to mimic the different layers of osteochondral tiss