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.

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.

A hybrid bio-jetting approach for directly engineering living cells.

This paper reports developments on a hybrid cell-engineering protocol coupling both bio-electrosprays and aerodynamically assisted bio-jets for process-handling living cells. The current work demonstrates the ability to couple these two cell-jetting protocols for handling a wide range of cells for deposition. The post-treated cells are assessed for their viability by way of flow cytometry, which illustrates a significant population of viable cells post-treatment in comparison to those controls. This work is the first example of coupling these two protocols for the process handling of living cells. The hybrid protocol demonstrates the achievement of stable cone jetting of a cellular suspension in the single-needle configuration which was previously unachieved with single-needle bio-electrosprays. Furthermore the living cells explored in these investigations expressed GFP, thus demonstrating the ability to couple gene therapy with this hybrid protocol. Hence, this approach could one day be explored for building biologically viable tissues incorporating a therapeutic payload for combating a range of cellular/tissue-based pathologies.

A novel direct fibre generation technique for preparing functionalized and compound scaffolds and membranes for applications within the life sciences.

Fibres, scaffolds and membranes have shown in the past decade their tremendous applicability to the life sciences. Essentially, these constructs have recently spearheaded focused applications in and within approaches to assist in the development of biologically active tissues to effective mechanisms for targeted and controlled cellular/drug delivery. There are several routes for forming continuous fibres from which functionalized scaffolds to membranes are prepared. One such technique that has demonstrated its wide versatility is none other than electrospinning. This is an electrified threading process capable of generating micro- and nano-sized (<50 nm) threads, which have been explored with a wide range of material compositions in their many manifestations. Although this threading process is economical and flexible, the process has its downsides, namely the associated high voltage to the preclusion of threading highly conducting viscoelastic media. In the current work we unveil a three-needle pressure-assisted spinning (PAS) approach comparable to coaxial- or co-electrospinning, without the hazardous high voltage and possessing the ability to thread highly conducting viscoelastic media from which pre-designed to functionalized compound structural units could be generated. Previously in our hands we demonstrated this technique with a two-needle system, which was only able to process a single- or multi-phase suspension at any given time. In its present form, two single/multi-phase miscible or immiscible media could be processed simultaneously. Therefore, PAS would be most useful to the biomedical world because a majority of biological media containing biological matter such as living cells have within them unprecedented concentrations of ions, which are needed by the living organisms for maintaining the cells/organisms' intricate metabolisms. In our hands, pressure-assisted spinning will compete directly with electrospinning and have a revolutionary effect on the fibre, scaffold and membrane preparation arena as applied to the plethora of applications within the life sciences.

Aerodynamically assisted bio-jets: the development of a novel and direct non-electric field-driven methodology for engineering living organisms.

We recently demonstrated the ability to use electrified jets under stable conditions for the generation of cell-bearing droplets to the formation of composite threads which are biologically active. Our studies established that processed cells were viable over several generations post-jetting and -threading. These harmless and successful techniques for jet-based cell handling to deployment for precision deposition have great potential and widespread applications in bioengineering and biotechnology. Nonetheless, our investigations into 'bio-electrosprays' and 'cell electrospinning' have elucidated these jets having direct applicability in regenerative and therapeutic medicine to studies in developmental biology. For these very reasons, jet methodologies having the capability to safely handle living organisms for drop and placing are increasingly gaining the interests of life scientists. We now demonstrate yet another technique (a non-electric field-driven approach, previously never explored with jetting living cells), possessing the ability to directly handle the processing of primary living organisms by means of the flow of a cell suspension within a needle placed in a pressure chamber in the presence of an applied pressure difference. The technique we introduce here is referred to as 'aerodynamically assisted bio-jets/-jetting' which is driven completely by aerodynamic forces applied over an exit orifice by way of a differential pressure. Our investigations present an operational window in which stable jetting conditions are achieved for the formation of a near-monodispersed distribution of cell-bearing droplets and droplet residues. Finally, the aerodynamically bio-jetted living primary organisms are assessed (over both short and long time points) for cellular viability by means of FACScan, a flow cytometry technology which quantifies the percentage of living and dead cells. These advanced biophysical and bioengineering studies elucidate the emergence of a non-electric field-driven bio-jetting technology which now joins the cell jetting race.

Pressure-assisted cell spinning: a direct protocol for spinning biologically viable cell-bearing fibres and scaffolds.

We recently pioneered the ability to directly electrospin living cells from which scaffolds to membranes were derived. This protocol, now widely referred to as 'cell electrospinning', is currently undergoing in-depth investigations where the post-treated cell's global gene expression to its sub-cellular components is being investigated for understanding any effects post-treating. Our motivation is to develop this method for the biomedical sciences, in particular for applications in regenerative and therapeutic medicine. In the current work, we unveil a direct cell spinning protocol which is non-electric field driven and which will compete directly with cell electrospinning. We referred to this processing method as 'pressure-assisted spinning' in our previous studies, where we demonstrated this route as an emerging micro/nanotechnology. In the current context, we refer to this processing protocol as 'pressure-assisted cell spinning' (PACS). Our developmental studies on PACS reported here show, for the first time, that this technique could be explored as an alternative approach to cell electrospinning. Pressure-assisted cell spinning now enters the direct biological scaffold to membrane formation league.