Coaxial Aerodynamically Assisted Bio-jets: A Versatile Paradigm for Directly Engineering Living Primary Organisms

Bio-Sprayed/Threaded Microalgae Remain Viable and Indistinguishable from Controls

Microalgae are increasingly playing a significant role in many areas of research and development. Recent studies have demonstrated their ability to aid wound healing by their ability to generate oxygen, aiding the healing process. Bearing this in mind, the capability to spray/spin deposit microalgae in suspension (solution) or compartmentalize living microalgae within architectures such as fibers/scaffolds and beads, would have significance as healing mechanisms for addressing a wide range of wounds. Reconstructing microalgae-bearing architectures as either scaffolds or beads could be generated via electric field (bio-electrospraying and cell electrospinning) and non-electric field (aerodynamically assisted bio-jetting/threading) driven technologies. However, before studying the biomechanical properties of the generated living architectures, the microalgae exposed to these techniques must be interrogated from a molecular level upward first, to establish these techniques, have no negative effects brought on the processed microalgae. Therefore these studies, demonstrate the ability of both these jetting and threading technologies to directly handle living microalgae, in suspension or within a polymeric suspension, safely, and form algae-bearing architectures such as beads and fibers/scaffolds.

Reimagining Flow Cytometric Cell Sorting

In this review, a brief history of this unrivaled technology, flow cytometry, is provided, highlighting its past and present advances, with particular focus on "flow cell" technologies. Flow cytometry has truly revolutionized high-throughput single cell analysis, which has tremendous implications, from laboratory to the clinic. This technology embodies what is truly referred to as cross fertile research, merging the physical with the life sciences. This review introduces the recent notable advancements in flow cell technology. This advancement sees the complete removal of liquid sheath flow, which has advanced the technology with the possibility of both the reduction in its foot print, while also simplifying the flow cells explored in cytometry. Interestingly, the novel sheathless flow cell technology demonstrated herein has the flexibility for handling both heterogeneous cell populations and whole organisms, thus demonstrating a versatile flow cell technology for both flow cytometry and fluorescent-activated cell sorting.

Bio-electrosprayed human neural stem cells are viable and maintain their differentiation potential

Background: Bio-electrospray (BES) is a jet-based delivery system driven by an electric field that has the ability to form micro to nano-sized droplets. It holds great potential as a tissue engineering tool as it can be used to place cells into specific patterns. As the human central nervous system (CNS) cannot be studied in vivo at the cellular and molecular level, in vitro CNS models are needed. Human neural stem cells (hNSCs) are the CNS building block as they can generate both neurones and glial cells. Methods: Here we assessed for the first time how hNSCs respond to BES. To this purpose, different hNSC lines were sprayed at 10 kV and their ability to survive, grow and differentiate was assessed at different time points. Results: BES induced only a small and transient decrease in hNSC metabolic activity, from which the cells recovered by day 6, and no significant increase in cell death was observed, as assessed by flow cytometry. Furthermore, bio-electrosprayed hNSCs differentiated as efficiently as controls into neurones, astrocytes and oligodendrocytes, as shown by morphological, protein and gene expression analysis. Conclusions: This study highlights the robustness of hNSCs and identifies BES as a suitable technology that could be developed for the direct deposition of these cells in specific locations and configurations.

Bio-electrosprayed human neural stem cells are viable and maintain their differentiation potential

Background: Bio-electrospray (BES) is a jet-based delivery system driven by an electric field that has the ability to form micro to nano-sized droplets. It holds great potential as a tissue engineering tool as it can be used to place cells into specific patterns. As the human central nervous system (CNS) cannot be studied in vivo at the cellular and molecular level, in vitro CNS models are needed. Human neural stem cells (hNSCs) are the CNS building block as they can generate both neurones and glial cells. Methods: Here we assessed for the first time how hNSCs respond to BES. To this purpose, different hNSC lines were sprayed at 10 kV and their ability to survive, grow and differentiate was assessed at different time points. Results: BES induced only a small and transient decrease in hNSC metabolic activity, from which cells recovered by day 6, and no significant increase in cell death was observed, as assessed by flow cytometry. Furthermore, bio-electrosprayed hNSCs differentiated as efficiently as controls into neurones, astrocytes and oligodendrocytes as shown by morphological, protein and gene expression analysis. Conclusions: This study highlights the robustness of hNSCs and identifies BES as a suitable technology that could be developed for the direct deposition of these cells in specific locations and configurations.

Phage as versatile nanoink for printing 3-D cell-laden scaffolds

Bioprinting is an emerging technology for producing tissue-mimetic 3-D structures using cell-containing hydrogels (bioink). Various synthetic and natural hydrogels with key characteristics, including biocompatibility, biodegradability, printability and crosslinkability, have been employed as ink materials in bioprinting. Choosing the right cell-containing "bioink" material is the most essential step for fabricating 3-D constructs with a controlled mechanical and biochemical microenvironment that can lead to successful tissue regeneration and repair. Here, we demonstrate that the genetically engineered M13 phage holds great potential for use as a versatile nanoink for printing 3-D cell-laden matrices. In particular, M13 phages displaying integrin-binding (GRGDS) and calcium-binding (DDYD) domains on their surface were blended with alginate to successfully form Ca(2+)-crosslinked hydrogels. Furthermore, 3-D cell-laden scaffolds with high cell viability were generated after optimizing the printing process. The MC3T3-E1 cells within these scaffolds showed enhanced proliferation and differentiation rates that increased proportionally with the concentration of phages in the 3-D matrices compared with the rates of cells in pure alginate scaffolds.

STATEMENT OF SIGNIFICANCE

Bioprinting is an emerging technology for producing tissue-mimetic 3-D structures using cell-containing hydrogels called bioink. Choosing the right bioink is essential for fabricating 3-D structures with controlled mechanical and biochemical properties which lead to successful tissue regeneration. Therefore, there is a growing demand for a new bioink material that can be designed from molecular level. Here, we demonstrate that genetically engineered M13 phage holds great potential for use as versatile bioink. The phage-based bioink benefits from its replicability, self-assembling property, and tunable molecular design and enables bioprinted scaffolds to exhibit improved cell viability, proliferation and differentiation. This study opens the door for the development of genetically tunable nanofibrous bioink materials which closely mimic natural structural proteins in the extracellular matrix.

Bio-electrospraying and droplet-based microfluidics: control of cell numbers within living residues

Bio-electrospraying (BES) has demonstrated great promise as a rapidly evolving strategy for tissue engineering and regenerative biology/medicine. Since its discovery in 2005, many studies have confirmed that cells (immortalized, primary and stem cells) and whole organisms (Danio rerio, Xenopus tropicalis, Caenorhabditis elegans to Drosophila) remain viable post-bio-electrospraying. Although this bio-protocol has achieved much, it suffers from one crucial problem, namely the ability to precisely control the number of cells within droplets and or encapsulations. If overcome, BES has the potential to become a high-efficiency biotechnique for controlled cell encapsulation, a technique most useful for a wide range of applications in biology and medicine ranging from the forming of three-dimensional cultures to an approach for treating diseases such as type I diabetes. In this communication, we address this issue by demonstrating the coupling of BES with droplet-based microfluidics for controlling live cell numbers within droplets and residues.

Aerodynamically assisted jetting and threading for processing concentrated suspensions containing advanced structural, functional and biological materials

In recent years material sciences have been interpreted right across the physical and the life sciences. Essentially this discipline broadly addresses the materials, processing, and/or fabrication right up to the structure. The materials and structures areas can range from the micro- to the nanometre scale and, in a materials sense, span from the structural, functional to the most complex, namely biological (living cells). It is generally recognised that the processing or fabrication is fundamental in bridging the materials with their structures. In a global perspective, processing has not only contributed to the materials sciences but its very nature has bridged the physical with the life sciences. In this review we discuss one such swiftly emerging fabrication approach having a plethora of applications spanning the physical and life sciences.

Bio-electrospraying embryonic stem cells: interrogating cellular viability and pluripotency

Bio-electrospraying, a recently discovered, direct electric field driven cell engineering process, has been demonstrated to have no harmful effects on treated cells at a molecular level. Although several cell types from both immortalized and primary cultures have been assessed post-treatment as a function of time in comparison to controls, the protocol has yet to be applied on embryonic stem cells. This is most important if bio-electrosprays are to further their applicability, in particular with regard to tissue engineering and regenerative medicine, where embryonic stem cells play a fundamental role. In the study presented herein the chosen stem cells are mouse embryonic stem (ES) cells. Hence, these first examples where embryonic stem cells have been jetted by way of bio-electrosprays, demonstrate the cellular viability and the cell's pluripotency indistinguishable when comparing those post-treated cells with their respective controls.

Genetic, genomic and physiological state studies on single-needle bio-electrosprayed human cells

Bio-electrospraying, a non-contact jet-based direct cell engineering approach, was recently pioneered and demonstrated for handling a wide range of primary living cells. In those studies, post-treated cells were biologically assessed in comparison to several controls by way of flow cytometry. Although flow cytometry accurately assesses those viable populations of cells, subtle effects at a sub-cellular level could have been missed. Therefore, in the present study we demonstrate metaphase chromosome breakage studies carried out on single-needle bio-electrosprayed human T-lymphocytes, which are compared with several controls. The results indicate that post-treated T-lymphocytes do not demonstrate any increase in chromosome damage in comparison to control cells. These studies further validate bio-electrospraying as a technique with potential for clinical utility.

Pilot study to investigate the possibility of cytogenetic and physiological changes in bio-electrosprayed human lymphocyte cells

Background: We recently pioneered the ability to directly electrospray and electrospin living cells without compromising their viability. These protocols, now referred to as ‘bio-electrosprays’ and ‘cell electrospinning’, are rapidly emerging bio-techniques with a plethora of promising applications within the life sciences, in particular to regenerative and therapeutic medicine. Our studies to date, with both bio-electrosprays and cell electrospinning, have demonstrated that a large population of viable cells exist post-treatment, in comparison to controls over both short and long periods as assessed by flow cytometry. Methods: Post-treated mammalian cells are investigated in comparison to controls (culture and needle controls) at a cytogenetic and physiological level. In particular, the study addresses chromosome integrity following these protocols to assess any protocol-inflicted aberrations. Results: The procedures explored failed to inflict any process-driven gross chromosomal aberrations post-treatment. Conclusions: Our preliminary investigations demonstrate no significant compromising affects on the cell’s structure at a cytogenetic or physiological level, post-treatment. Thus, further establishing these protocols as unique direct cell-engineering approaches with a host of biological and medical applications, from the development of tissues to perhaps even organs in the future.

Living scaffolds (specialized and unspecialized) for regenerative and therapeutic medicine

The physical sciences have increasingly demonstrated a significant influence on the life sciences. Engineering in particular has shown its input through the development of novel medical devices and processes having significance to the biomedical field. This review introduces and discusses several fiber generation protocols, which have recently undergone development and exploration for directly handling living cells from which continuous cell-bearing or living threads to scaffolds and membranes have been fabricated. In doing so these protocols have not only demonstrated their versatility but also opened several unique possibilities for the use of these scaffolds in a plethora of biological and medical applications. In particular, these living fibrous structural units could be explored for regeneration purposes, e.g., from accelerated wound healing to combating a wide range of pathologies when coupled with gene therapy. Thus, "living entities" such as these scaffolds could be most useful in surgery/medicine, including its exploration with stem cells for the preparation of unspecialized living scaffolds and membranes.