Uncovering the relationship between macrophages and polypropylene surgical mesh.

Currently, in vitro testing examines the cytotoxicity of biomaterials but fails to consider how materials respond to mechanical forces and the immune response to them; both are crucial for successful long-term implantation. A notable example of this failure is polypropylene mid-urethral mesh used in the treatment of stress urinary incontinence (SUI). The mesh was largely successful in abdominal hernia repair but produced significant complications when repurposed to treat SUI. Developing more physiologically relevant in vitro test models would allow more physiologically relevant data to be collected about how biomaterials will interact with the body. This study investigates the effects of mechanochemical distress (a combination of oxidation and mechanical distention) on polypropylene mesh surfaces and the effect this has on macrophage gene expression. Surface topology of the mesh was characterised using SEM and AFM; ATR-FTIR, EDX and Raman spectroscopy was applied to detect surface oxidation and structural molecular alterations. Uniaxial mechanical testing was performed to reveal any bulk mechanical changes. RT-qPCR of selected pro-fibrotic and pro-inflammatory genes was carried out on macrophages cultured on control and mechanochemically distressed PP mesh. Following exposure to mechanochemical distress the mesh surface was observed to crack and craze and helical defects were detected in the polymer backbone. Surface oxidation of the mesh was seen after macrophage attachment for 7 days. These changes in mesh surface triggered modified gene expression in macrophages. Pro-fibrotic and pro-inflammatory genes were upregulated after macrophages were cultured on mechanochemically distressed mesh, whereas the same genes were down-regulated in macrophages exposed to control mesh. This study highlights the relationship between macrophages and polypropylene surgical mesh, thus offering more insight into the fate of an implanted material than existing in vitro testing.

Revealing The Morphology of Ink and Aerosol Jet Printed Palladium-Silver Alloys Fabricated from Metal Organic Decomposition Inks.

Palladium films hold signicance due to their remarkable affinity for hydrogen diffusion, rendering them valauble for the seperation and purification of hydrogen in membrane reactors. However, palladium is expensive, and its films can become brittle after only a few cycles of hydrogen separation. Alloying with silver has been shown to overcome the problem of palladium embrittlement. Palladium-silver films have been produced via several methods but all have drawbacks, such as difficulties controlling the alloy composition. This study explores two promising jet printing methods: Inkjet and Aerosoljet. Both methods offer potential advantages such as direct patterning, which reduces waste, enables thin film production, and allows for the control of alloy composition. For the first time, palladium-silver alloys have been produced via inkjet printing using a palladium-silver metal organic decomposition (MOD) ink, which alloys at a temperature of 300 °C with nitrogen. Similarly, this study also demonstrates a pioneering approach for Aerosol Jet printing, showing the potential of a novel room-temperature method, for the deposition of palladium-silver MOD inks. This low temperature approach is considered an important development as palladium-silver MOD inks are originally designed for deposition on heated substrates.

Assessing the Quality of Oxygen Plasma Focused Ion Beam (O-PFIB) Etching on Polypropylene Surfaces Using Secondary Electron Hyperspectral Imaging.

The development of Focused Ion Beam-Scanning Electron Microscopy (FIB-SEM) systems has provided significant advances in the processing and characterization of polymers. A fundamental understanding of ion-sample interactions is still missing despite FIB-SEM being routinely applied in microstructural analyses of polymers. This study applies Secondary Electron Hyperspectral Imaging to reveal oxygen and xenon plasma FIB interactions on the surface of a polymer (in this instance, polypropylene). Secondary Electron Hyperspectral Imaging (SEHI) is a technique housed within the SEM chamber that exhibits multiscale surface sensitivity with a high spatial resolution and the ability to identify carbon bonding present using low beam energies without requiring an Ultra High Vacuum (UHV). SEHI is made possible through the use of through-the-lens detectors (TLDs) to provide a low-pass SE collection of low primary electron beam energies and currents. SE images acquired over the same region of interest from different energy ranges are plotted to produce an SE spectrum. The data provided in this study provide evidence of SEHI's ability to be a valuable tool in the characterization of polymer surfaces post-PFIB etching, allowing for insights into both tailoring polymer processing FIB parameters and SEHI's ability to be used to monitor serial FIB polymer surfaces in situ.

Development of PCL PolyHIPE Substrates for 3D Breast Cancer Cell Culture.

Cancer is a becoming a huge social and economic burden on society, becoming one of the most significant barriers to life expectancy in the 21st century. In particular, breast cancer is one of the leading causes of death for women. One of the most significant difficulties to finding efficient therapies for specific cancers, such as breast cancer, is the efficiency and ease of drug development and testing. Tissue-engineered (TE) in vitro models are rapidly developing as an alternative to animal testing for pharmaceuticals. Additionally, porosity included within these structures overcomes the diffusional mass transfer limit whilst enabling cell infiltration and integration with surrounding tissue. Within this study, we investigated the use of high-molecular-weight polycaprolactone methacrylate (PCL-M) polymerised high-internal-phase emulsions (polyHIPEs) as a scaffold to support 3D breast cancer (MDA-MB-231) cell culture. We assessed the porosity, interconnectivity, and morphology of the polyHIPEs when varying mixing speed during formation of the emulsion, successfully demonstrating the tunability of these polyHIPEs. An ex ovo chick chorioallantoic membrane assay identified the scaffolds as bioinert, with biocompatible properties within a vascularised tissue. Furthermore, in vitro assessment of cell attachment and proliferation showed promising potential for the use of PCL polyHIPEs to support cell growth. Our results demonstrate that PCL polyHIPEs are a promising material to support cancer cell growth with tuneable porosity and interconnectivity for the fabrication of perfusable 3D cancer models.

Characterization in respect to degradation of titanium-coated polypropylene surgical mesh explanted from humans.

Titanium-coated polypropylene (Ti-PP) mesh was introduced in 2002 as a surgical mesh for the treatment of hernias and shortly after for pelvic floor surgery, with the aim of improving biocompatibility when compared to non-titanised/regular PP mesh implants. The application of a titanium coating could also be beneficial to address concerns regarding the exposure of PP in an in vivo environment. Many studies have shown that PP, although it is widely accepted as a stable polymer, is subject to oxidation and degradation, such degradation affects the mechanical behavior, that is, the stiffness and tensile strength of PP mesh. Despite the wide clinical use of Ti-PP surgical meshes, no study has yet investigated the residual material properties post clinical deployment and subsequent explantation. In this study, two explanted Ti-PP mesh samples each having different incorporation durations from two patients were examined. Material analysis conducted within this study includes the following techniques: attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), Raman spectroscopy, low voltage - scanning electron microscopy (LV-SEM), backscattered electron (BSE) imaging, energy dispersive X-ray spectroscopy (EDS) and secondary election hyperspectral imaging (SEHI). The hypothesis of this study is that the Ti coating successfully shields the PP mesh from oxidative stress in vivo and thus protects it from degradation. The results of this analysis show for the first time evidence of bulk oxidation, surface degradation, and environmental stress cracking on explanted Ti-PP meshes.

Revealing Localised Mechanochemistry of Biomaterials Using In Situ Multiscale Chemical Analysis.

The study of mechanical and chemical phenomena arising within a material that is being subjected to external stress is termed mechanochemistry (MC). Recent advances in MC have revealed the prospect not only to enable a greener route to chemical transformations but also to offer previously unobtainable opportunities in the production and screening of biomaterials. To date, the field of MC has been constrained by the inability of current characterisation techniques to provide essential localised multiscale chemically mapping information. A potential method to overcome this is secondary electron hyperspectral imaging (SEHI). SEHI is a multiscale material characterisation technique applied within a scanning electron microscope (SEM). Based on the collection of secondary electron (SE) emission spectra at low primary beam energies, SEHI is applicable to the chemical assessment of uncoated polymer surfaces. Here, we demonstrate that SEHI can provide in situ MC information using poly(glycerol sebacate)-methacrylate (PGS-M) as an example biomaterial of interest. This study brings the use of a bespoke in situ SEM holder together with the application of SEHI to provide, for the first time, enhanced biomaterial mechanochemical characterisation.

Low-voltage SEM of air-sensitive powders: From sample preparation to micro/nano analysis with secondary electron hyperspectral imaging.

Powder materials are used in all corners of materials science, from additive manufacturing to energy storage. Scanning electron microscopy (SEM) has developed to meet morphological, microstructural and bulk chemical powder characterization requirements. These include nanoscale elemental analysis and high-throughput morphological assays. However, spatially localized powder surface chemical information with similar resolution to secondary electron (SE) imaging is not currently available in the SEM. Recently, energy filtered (EF-) SEM has been used for surface chemical characterization by secondary electron hyperspectral imaging (SEHI). This review provides a background to existing powder characterization capabilities in the low voltage SEM provided by SE imaging, EDX analysis and BSE imaging and sets out how these capabilities could be extended for surface chemical analysis by applying SEHI to powders, with particular emphasis on air and beam sensitive powder surfaces. Information accessible by SEHI, its advantages and limitations, is set into the context of other chemical characterization methods that are commonly used for assessing powder surface chemistry such as by Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). The applicability of existing powder preparation methods for SEM to SEHI is also reviewed. An alternative preparation method is presented alongside first examples of SEHI characterization of powder surfaces. The commercial powder materials used as examples were carbon-fiber/polyamide composite powder feedstock (CarbonMide®) used in additive manufacturing and powders consisting of lithium nickel cobalt oxide (NMC). SEHI is shown to differentiate bonding present at carbonaceous material surfaces and extract information about the work function of metal oxide surfaces. The surface sensitivity of SEHI is indicated by comparison of pristine powders to those with surface material added in preparation. A minimum spatial localization of chemical information of 55 nm was achieved in differentiating regions of NMC surface chemistry by distinct SE spectra.

Monitoring Carbon in Electron and Ion Beam Deposition within FIB-SEM.

It is well known that carbon present in scanning electron microscopes (SEM), Focused ion beam (FIB) systems and FIB-SEMs, causes imaging artefacts and influences the quality of TEM lamellae or structures fabricated in FIB-SEMs. The severity of such effects depends not only on the quantity of carbon present but also on its bonding state. Despite this, the presence of carbon and its bonding state is not regularly monitored in FIB-SEMs. Here we demonstrated that Secondary Electron Hyperspectral Imaging (SEHI) can be implemented in different FIB-SEMs (ThermoFisher Helios G4-CXe PFIB and Helios Nanolab G3 UC) and used to observe carbon built up/removal and bonding changes resulting from electron/ion beam exposure. As well as the ability to monitor, this study also showed the capability of Plasma FIB Xe exposure to remove carbon contamination from the surface of a Ti6246 alloy without the requirement of chemical surface treatments.

A novel characterisation approach to reveal the mechano-chemical effects of oxidation and dynamic distension on polypropylene surgical mesh.

Polypropylene (PP) surgical mesh, used successfully for the surgical repair of abdominal hernias, is associated with serious clinical complications when used in the pelvic floor for repair of stress urinary incontinence or support of pelvic organ prolapse. While manufacturers claim that the material is inert and non-degradable, there is a growing body of evidence that asserts PP fibres are subject to oxidative damage and indeed explanted material from patients suffering with clinical complications has shown some evidence of fibre cracking and oxidation. It has been proposed that a pathological cellular response to the surgical mesh contributes to the medical complications; however, the mechanisms that trigger the specific host response against the material are not well understood. Specifically, this study was constructed to investigate the mechano-chemical effects of oxidation and dynamic distension on polypropylene surgical mesh. To do this we used a novel advanced spectroscopical characterisation technique, secondary electron hyperspectral imaging (SEHI), which is based on the collection of secondary electron emission spectra in a scanning electron microscope (SEM) to reveal mechanical-chemical reactions within PP meshes.