24 / 08 / 2021
FAL’s electrospun scaffolds research is published
Work at the FRAME Alternatives Laboratory (FAL) into the development of biomaterial scaffolds that support in vitro tissue development has been included in a recently published paper in the Royal Society of Chemistry’s Journal of Materials Chemistry B.
The development of 3D culture systems that support the growth and development of cells in an environment that more realistically replicates the human body is a key focus for many research projects in the FAL. Whilst many in vitro methods exist that allow human tissue to be grown in the lab, if the environment does not effectively mimic the conditions the cells would experience in vivo (in the body), the cells will not grow or may develop and behave differently. Improving cell culture methods is therefore essential to ensure research findings are of value and help progress our knowledge of human cell responses to drugs and disease.
The FAL carries out a lot of research into improving liver cell models which can be used in preclinical stages of new drug development, for example. One key aspect of these models are scaffolds that allow cells to grow in a 3D environment, as they would in the body. The scaffolds alone do not mimic alone the natural cell environment – they must then be exposed to the right mix and quantities of chemicals that would be found in the extracellular matrix around the cells in the body.
In this study, the researchers created a 3D scaffold material using electrospinning and investigated the potential of the selected biomaterials to supply proteins to the cells growing on the scaffold. This multidisciplinary project, which was a part of PhD student Inchirah’s project, was the result of a collaboration between FAL director Dr Andrew Bennett, Prof Felicity Rose and Prof Cameron Alexander from the School of Pharmacy at University of Nottingham. This project was supported by the Engineering and Physical Sciences Research Council (EPSRC) and the Medical Research Council’s Centre of Doctoral Training in Regenerative Medicine.
Effective regenerative medicine requires delivery systems which can release multiple biological components at appropriate levels and at different phases of tissue growth. However, there are few biomaterial scaffold materials that are fully suitable for the loading and controlled release of multiple proteins.
This project describes how proteins were physically and chemically loaded into a single coaxial electrospun fibre scaffold (this comprises an outer layer with fibres inside, like an insulated electrical cable). This provides a bi-phasic release profile where the outer layer disappears, leaving the slow release of the proteins encapsulated beneath. The biomaterials used in scaffolds must be compatible with the proteins to be released, so delivery of proteins within cell culture systems such as this can be challenging, with proteins susceptible to breakdown due to incorrect pH or ion levels, or the action of enzymes from the cells.
The polymers used to construct the scaffold in this project contained aolyethylene oxide (PEO) core and polycaprolactone (PCL) reacted or mixed with (bis-aminopropyl) polyether (Jeffamine ED2003; JFA) for the shell. This was compared with a more common polymer shell used to embed proteins created through a technique called aminolysis.
Various aspects of the polymer structure are reported on in the study, including the scaffold morphology, scaffold surface analysis, mechanical properties of the scaffolds, ability of the scaffolds to hold proteins on the outside and release them from the core, and compatibility with human liver cells and measurements to assess cell attachment and metabolism using a human liver cell line.
The researchers showed that the use of JFA on the outside of this coaxial electrospun scaffold successfully facilitates the production and delivery of a multiple proteins to the cells creating the desired environment for cell growth. Aminolysis treatment, which is considered the gold standard for surface delivery of biomolecules such as proteins, was suitable for the release of surface proteins but not when a bioactive protein was loaded in the core, due to loss of that bioactivity during the aminolysis treatment.
Despite interesting properties seen in JFA polymers, few studies have reported their use in electrospinning, and none in the coaxial-electrospinning structure described and used in this research. The study concluded that the use of JFA does not affect the stability of a pre-loaded protein in the core, enabling the simultaneous incorporation of multiple proteins in the same scaffold without affecting their activity. Additionally, surface analysis and mechanical characterisation showed that JFA rendered the scaffold more elastic than PEO/PCL fibres alone. Finally, the biocompatibility of surface functionalisation of the PEO/PCL/JFA fibre scaffolds was confirmed, and modulation of cellular responses to the incorporated bioactive molecules were successfully demonstrated.
These findings suggest that the PCL/JFA polymer shell has a lot of potential for use in future cell scaffolds, and will help to support the future development of non-animal research methods.