Bioprinting, within the emerging field of biofabrication, aims at the fabrication of functional biomimetic constructs. Different 3D bioprinting techniques have been adapted to bioprint cell-laden bioinks. However, single-material bioprinting techniques oftentimes fail to reproduce the complex compositions and diversity of native tissues. Multi-material bioprinting as an emerging approach enables the fabrication of heterogeneous multi-cellular constructs that replicate their host microenvironments better than single-material approaches. Here, bioprinting modalities are reviewed, their being adapted to multi-material bioprinting is discussed, and their advantages and challenges, encompassing both custom-designed and commercially available technologies are analyzed. A perspective of how multi-material bioprinting opens up new opportunities for tissue engineering, tissue model engineering, therapeutics development, and personalized medicine is offered.

Emerging Technologies in Multi-Material Bioprinting.

Inkjet printing technology uses the low-cost direct deposition manufacturing technique for printing and is applicable in various fields including optics, ceramics, three-dimensional printing in biomedicine, and conductive circuitry. This study reviews the classifications and applications of inkjet printing technologies, with a focus on recent publications. The different design approaches, applications, and research progress of several inkjet printing techniques are reviewed. Among them, the piezoelectric inkjet printing technology is the main focus owing to its reliability and handling of a diverse range of inks. A piezo-driven inkjet printhead is activated by applying a voltage waveform to a piezoelectric membrane. The waveform ensures the formation of the designed droplet and a stable jet. A survey of various driving-voltage waveforms is conducted, which can serve as a reference to the research community that uses piezo-driven inkjet printheads. The challenges of printing quality, stability, and speed and their solutions as published in recent studies are reviewed. Technologies for producing high-viscosity inkjets are explored, and the applications of inkjet printing technology in textile, displays, and wearable devices are discussed.

/pdf/classifications-and-applications-of-inkjet-printing-4q6l5hbyo4.pdf

Classifications and Applications of Inkjet Printing Technology: A Review

Tumor cells evolve in a complex and heterogeneous environment composed of different cell types and an extracellular matrix. Current 2D culture methods are very limited in their ability to mimic the cancer cell environment. In recent years, various 3D models of cancer cells have been developed, notably in the form of spheroids/organoids, using scaffold or cancer-on-chip devices. However, these models have the disadvantage of not being able to precisely control the organization of multiple cell types in complex architecture and are sometimes not very reproducible in their production, and this is especially true for spheroids. Three-dimensional bioprinting can produce complex, multi-cellular, and reproducible constructs in which the matrix composition and rigidity can be adapted locally or globally to the tumor model studied. For these reasons, 3D bioprinting seems to be the technique of choice to mimic the tumor microenvironment in vivo as closely as possible. In this review, we discuss different 3D-bioprinting technologies, including bioinks and crosslinkers that can be used for in vitro cancer models and the techniques used to study cells grown in hydrogels; finally, we provide some applications of bioprinted cancer models. 

/pdf/current-advances-in-3d-bioprinting-for-cancer-modeling-and-2qiq67ri.pdf

Current Advances in 3D Bioprinting for Cancer Modeling and Personalized Medicine

Think outside the box: 3D bioprinting concepts for biotechnological applications - recent developments and future perspectives.

Single-cell analysis is becoming an indispensable tool in modern biological and medical research. Single-cell isolation is the key step for single-cell analysis. Single-cell printing shows several distinct advantages among the single-cell isolation techniques, such as precise deposition, high encapsulation efficiency, and easy recovery. Therefore, recent developments in single-cell printing have attracted extensive attention. We review herein the recently developed bioprinting strategies with single-cell resolution, with a special focus on inkjet-like single-cell printing. First, we discuss the common cell printing strategies and introduce several typical and advanced printing strategies. Then, we introduce several typical applications based on single-cell printing, from single-cell array screening and mass spectrometry-based single-cell analysis to three-dimensional tissue formation. In the last part, we discuss the pros and cons of the single-cell strategies and provide a brief outlook for single-cell printing.

/pdf/advances-in-single-cell-printing-1zhqgwg8.pdf

Advances in Single-Cell Printing

Bioprinting allows the manufacture of complex cell-laden hydrogel constructs that can mature into tissue replacements in subsequent cell culture processes. The nozzles used in currently available bioprinters limit the print resolution and at dimensions below 100 µm clogging is expected. Most critically, the reduction of nozzle diameter also increases shear stress during printing. At critical shear stress, mechanical damage to printed cells triggers cell death. To overcome these limitations, a novel 3D bioprinting method based on the principle of acoustic droplet ejection (ADE) is introduced here. The absence of a nozzle in this method minimizes critical shear stress. A numerical simulation reveals that maximum shear stress during the ADE process is 2.7 times lower than with a Ø150 µm microvalve nozzle. Printing of cell clusters contained in droplets at the millimeter length scale, as well as in droplets the size of a single cell, is feasible. The precise 3D build-up of cell-laden structures is demonstrated and evidence is provided that there are no negative effects on stem cell morphology, proliferation, or differentiation capacities. This multiscale acoustic bioprinting technique thus holds promise for cell-preserving creation of complex and individualized cell-laden 3D hydrogel structures.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/smtd.202000971

Benedikt Gundert

Papers

Multiscale 3D Bioprinting by Nozzle‐Free Acoustic Droplet Ejection