Aaron D. Gilmour

Hydrogel coatings provide a promising pathway to tailor and improve cell culture surfaces, maintaining bulk material properties desired for handling and optical measurement while providing cell–surface interactions vital for optimising cell behaviour. For immobilised hydrogels to be useful, layers of this structure must be robustly adhered to the substrate and able to withstand strain from sources such as tensile forces exerted by adherent cell lines and fluid streams in microfluidic devices. Plasma‐activated coatings (PAC) are investigated here as a method for robust and translatable hydrogel immobilisation. Results show that embedded radicals within the PAC can immobilise methacrylated poly‐vinyl alcohol hydrogels, forming nanometer‐thick (reagent‐free) to millimeter‐thick (photoinitiator‐assisted) hydrogel layers. Utilisation of the nanometer reagent‐free layer as a ‘primer layer’ before forming photoinitiator‐assisted millimeter‐thick layers is a novel approach that results in superior adhesion of the thicker gel layers. When used as a cell culture surface for MCF‐7 cells, E cadherin and vinculin signalling significantly ( p < 0.05) increased (for physiologically relevant High MA hydrogel compared to the glass control). This work therefore outlines the novel reagent‐free primer layer approach as a method for creating hydrogels with superior adhesion for in vitro culture of cells.

The growth and study of living cells outside their native organisms forms the foundation of modern biology and underpin medicine. It has led to the identification of stem cells and the development of methods that can reprogram mature cells into pluripotent states, creating enormous potential for new therapies that can cure previously untreatable conditions and enable the repair of patient-specific tissues and organs. Accessing these advances, however, will require the development of sophisticated new cell culture materials and technologies. This Perspective article reviews the development of cell culture and current cell culture capabilities, with particular attention to the influence of spatial and temporal factors. We discuss traditional 2D culture, the complexities of 3D systems, and the emergence of 2.5D approaches as an alternative to high throughput 2D systems. Untapped potential and barriers to progress are identified while the new materials and technologies needed to drive the field forward are discussed.

The clinical potential of mesenchymal stromal/stem cells (MSCs) is limited by the mismatch between their low abundance in adult tissue and the high doses required for treatment. Conventional cell expansion systems that rely on repeated supplementation with labile, soluble growth factors are inefficient and costly. Moreover, the majority of transplanted MSCs exhibit poor survival post-delivery, undermining therapeutic outcomes and exacerbating cell supply challenges. Three-dimensional (3D) polymeric scaffolds, with high surface-area-to-volume ratios, offer a promising strategy for enhancing both cell expansion and delivery. However, their bioinert nature and limited functionalization options have hindered translation. Here, we present a dual-purpose macroporous polycaprolactone (PCL) scaffold, homogeneously activated using long-lived surface-embedded radicals, to enable the one-step covalent immobilization of fibroblast growth factor 2 (FGF2) throughout its internal architecture. This approach preserves the degradability of PCL, while enhancing FGF2 stability and bioavailability. The resulting biofunctional scaffold supports labor-efficient, spatially uniform MSC expansion with a 99% reduction in FGF2 usage, compared to serial cultures on planar surfaces in FGF2-supplemented media. In addition, when used as a cell delivery vehicle, the scaffold enhances MSC survival and retention after implantation. The generation of such multifunctional 3D materials has broad implications for improving the feasibility, accessibility, and impact of cell therapies and offers a blueprint for the robust, cost-effective biofunctionalization of other biomedically relevant porous materials.

This paper provides first-time evidence of covalent attachment of fluorescent molecules to plasma polymerised nanoparticles for diagnostic and therapeutic applications.

Surface biofunctionalization aims to create cell-instructive surfaces that control the behavior of cells and modulate cellular interactions by incorporating cell signaling moieties at the materials–biosystem interface. Despite advances in developing bioinert and biocompatible materials, blood clotting, inflammation, and cell death continue to be observed upon the contact of foreign materials with living tissues leading to the materials' rejection. Specific examples include the application of foreign materials in implantable devices (e.g., bone implants, antimicrobial surfaces, and cardiovascular stents), biosensors, drug delivery, and 3D-bioprinting. Biofunctionalization of materials to date has been predominantly realized using wet chemical approaches. However, the complexity of wet chemistry, toxicity of reactants, waste disposal issues, reaction time, poor reproducibility, and scalability drive a need for a paradigm shift from wet chemical approaches to dry methods of surface biofunctionalization. Plasma-based technologies that enable covalent surface immobilization of biomolecules have emerged as dry, reagent-free, and single-step alternatives for surface biofunctionalization. This review commences by highlighting the need for bioinstructive surfaces and coatings for various biomedical applications such as bone implants, antimicrobial surfaces, biosensors, and 3D-bioprinted structures, followed by a brief review of wet chemical approaches for developing biofunctionalized surfaces and biomimetic devices. We then provide a comprehensive review of the development of plasma-based technologies for biofunctionalization, highlighting the plasma–surface interactions and underpinning mechanisms of biomolecule immobilization.

Cell transplantation constitutes an important avenue for development of new treatments for spinal cord injury (SCI). These therapies are aimed at supporting neural repair and/or replacing lost cells at the injury site. To date, various cell types have been trialed, with most studies focusing on different types of stem cells or glial cells. Here, we review commonly used cell transplantation approaches for spinal cord injury (SCI) repair, with focus on transplantation of olfactory ensheathing cells (OECs), the glial cells of the primary olfactory nervous system. OECs are promising candidates for promotion of neural repair given that they support continuous regeneration of the olfactory nerve that occurs throughout life. Further, OECs can be accessed from the nasal mucosa (olfactory neuroepithelium) at the roof of the nasal cavity and can be autologously transplanted. OEC transplantation has been trialed in many animal models of SCI, as well as in human clinical trials. While several studies have been promising, outcomes are variable and the method needs improvement to enhance aspects such as cell survival, integration, and migration. As a case study, we include the approaches used by our team (the Clem Jones Centre for Neurobiology and Stem Cell Research, Griffith University, Nathan, QLD, Australia) to address the current problems with OEC transplantation and discuss how the therapeutic potential of OEC transplantation can be improved. Our approach includes discovery research to improve our knowledge of OEC biology, identifying natural and synthetic compounds to stimulate the neural repair properties of OECs, and designing three-dimensional cell constructs to create stable and transplantable cell structures.

Intracortical electrodes for brain–machine interfaces rely on intimate contact with tissues for recording signals and stimulating neurons. However, the long-term viability of intracortical electrodes in vivo is poor, with a major contributing factor being the development of a glial scar. In vivo approaches for evaluating responses to intracortical devices are resource intensive and complex, making statistically significant, high throughput data difficult to obtain. In vitro models provide an alternative to in vivo studies; however, existing approaches have limitations which restrict the translation of the cellular reactions to the implant scenario. Notably, there is no current robust model that includes astrocytes, microglia, oligodendrocytes and neurons, the four principle cell types, critical to the health, function and wound responses of the central nervous system (CNS). In previous research a co-culture of primary mouse mature mixed glial cells and immature neural precursor cells were shown to mimic several key properties of the CNS response to implanted electrode materials. However, the method was not robust and took up to 63 days, significantly affecting reproducibility and widespread use for assessing brain-material interactions. In the current research a new co-culture approach has been developed and evaluated using immunocytochemistry and quantitative polymerase chain reaction (qPCR). The resulting method reduced the time in culture significantly and the culture model was shown to have a genetic signature similar to that of healthy adult mouse brain. This new robust CNS culture model has the potential to significantly improve the capacity to translate in vitro data to the in vivo responses.

Nerve block via electrical stimulation of nerves requires a device capable of transferring large amounts of charge across the neural interface on chronic time scales. Current metal electrode designs are limited in their ability to safely and effectively deliver this charge in a stable manner. Conductive hydrogel (CH) coatings are a promising alternative to metal electrodes for neural interfacing devices. This study assessed the performance of CH electrodes compared to platinum-iridium (PtIr) electrodes in commercial nerve cuff devices in both the in vitro and acute in vivo environments. CH electrodes were found to have higher charge storage capacities and lower impedances compared to bare PtIr electrodes. Application of CH coatings also resulted in a three-fold increase in in vivo charge injection limit. These significant improvements in electrochemical properties will allow for the design of smaller and safer stimulating devices for nerve block applications.