Infrared Based Saliva Screening Test for COVID-19.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has resulted in an unprecedented need for diagnostic testing that is critical in controlling the spread of COVID-19. We propose a portable infrared spectrometer with purpose-built transflection accessory for rapid point-of-care detection of COVID-19 markers in saliva. Initially, purified virion particles were characterized with Raman spectroscopy, synchrotron infrared (IR) and AFM-IR. A data set comprising 171 transflection infrared spectra from 29 subjects testing positive for SARS-CoV-2 by RT-qPCR and 28 testing negative, was modeled using Monte Carlo Double Cross Validation with 50 randomized test and model sets. The testing sensitivity was 93 % (27/29) with a specificity of 82 % (23/28) that included positive samples on the limit of detection for RT-qPCR. Herein, we demonstrate a proof-of-concept high throughput infrared COVID-19 test that is rapid, inexpensive, portable and utilizes sample self-collection thus minimizing the risk to healthcare workers and ideally suited to mass screening.

Interaction of Giant Unilamellar Vesicles with the Surface Nanostructures on Dragonfly Wings.

The waxy epicuticle of dragonfly wings contains a unique nanostructured pattern that exhibits bactericidal properties. In light of emerging concerns of antibiotic resistance, these mechano-bactericidal surfaces represent a particularly novel solution by which bacterial colonization and the formation of biofilms on biomedical devices can be prevented. Pathogenic bacterial biofilms on medical implant surfaces cause a significant number of human deaths every year. The proposed mechanism of bactericidal activity is through mechanical cell rupture; however, this is not yet well understood and has not been well characterized. In this study, we used giant unilamellar vesicles (GUVs) as a simplified cell membrane model to investigate the nature of their interaction with the surface of the wings of two dragonfly species, Austrothemis nigrescens and Trithemis annulata, sourced from Victoria, Australia, and the Baix Ebre and Terra Alta regions of Catalonia, Spain. Confocal laser scanning microscopy and cryo-scanning electron microscopy techniques were used to visualize the interactions between the GUVs and the wing surfaces. When exposed to both natural and gold-coated wing surfaces, the GUVs were adsorbed on the surface, exhibiting significant deformation, in the process of membrane rupture. Differences between the tensile rupture limit of GUVs composed of 1,2-dioleoyl- sn-glycero-3-phosphocholine and the isotropic tension generated from the internal osmotic pressure were used to indirectly determine the membrane tensions, generated by the nanostructures present on the wing surfaces. These were estimated as being in excess of 6.8 mN m-1, the first experimental estimate of such mechano-bactericidal surfaces. This simple model provides a convenient bottom-up approach toward understanding and characterizing the bactericidal properties of nanostructured surfaces.

Co-delivery of inhalable therapies: Controlling active ingredients spatial distribution and temporal release.

The management of respiratory diseases relies on the daily administration of multiple active pharmaceutical ingredients (APIs), leading to a lack of patient compliance and impaired quality of life. The frequency and dosage of the APIs result in increased side effects that further worsens the overall patient condition. Here, the manufacture of polymer-polymer core-shell microparticles for the sequential delivery of multiple APIs by inhalation delivery is reported. The microparticles, composed of biodegradable polymers silk fibroin (shell) and poly(L-lactic acid) (core), incorporating ciprofloxacin in the silk layer and ibuprofen (PLLA core) as the antibiotic and anti-inflammatory model APIs, respectively. The polymer-polymer core-shell structure and the spatial distribution of the APIs have been characterized using cutting-edge synchrotron macro ATR-FTIR technique, which was correlated with the respective API sequential release profiles. The APIs microparticles had a suitable size and aerosol properties for inhalation therapies (≤4.94 ± 0.21µm), with low cytotoxicity and immunogenicity in healthy lung epithelial cells. The APIs compartmentalization obtained by the microparticles not only could inhibit potential actives interactions but can provide modulation of the APIs release profiles via an inhalable single administration.

Odd-even effects on hydration of natural polyelectrolyte multilayers: An in situ synchrotron FTIR microspectroscopy study.

HYPOTHESIS: Odd-even effects in polysaccharide polyelectrolyte multilayers influence their hydration content and the chemical environment of the water within them. EXPERIMENTS: Polysaccharide polyelectrolyte multilayers (PEMs) composed of pharmaceutical grade fucoidan and chitosan were studied under confinement using synchrotron FTIR microspectroscopy at increasing pressure, in order to isolate and measure infrared spectra of water within the PEM, without interference from bulk water. Complementary studies of the PEMs were carried out using lab-based in situ attenuated total reflectance Fourier transform spectroscopy (ATR FTIR) and quartz crystal microbalance with dissipation monitoring (QCM-D), as well as zeta potential measurements, to determine the quantity of adsorbed polymer, hydration content, film thickness, viscoelastic properties and surface charge during layer-by-layer deposition. FINDINGS: The hydration of the PEM followed a saw-tooth profile, known as the odd-even effect, where the film increased hydration with fucoidan adsorption and dehydrated/densified with chitosan adsorption. The water structure within the film showed a lower degree of hydrogen bonding than water in the bulk electrolyte. However, the water structure/environment was independent of the terminating layer of the PEM, in spite of the alteration in percentage hydration water, indicating only a partial proof of the initial hypothesis for this multilayer system (hydration amount changes, hydration water environment does not).

Insect Analogue to the Lotus Leaf: A Planthopper Wing Membrane Incorporating a Low-Adhesion, Nonwetting, Superhydrophobic, Bactericidal, and Biocompatible Surface.

Nature has produced many intriguing and spectacular surfaces at the micro- and nanoscales. These small surface decorations act for a singular or, in most cases, a range of functions. The minute landscape found on the lotus leaf is one such example, displaying antiwetting behavior and low adhesion with foreign particulate matter. Indeed the lotus leaf has often been considered the "benchmark" for such properties. One could expect that there are animal counterparts of this self-drying and self-cleaning surface system. In this study, we show that the planthopper insect wing (Desudaba danae) exhibits a remarkable architectural similarity to the lotus leaf surface. Not only does the wing demonstrate a topographical likeness, but some surface properties are also expressed, such as nonwetting behavior and low adhering forces with contaminants. In addition, the insect-wing cuticle exhibits an antibacterial property in which Gram-negative bacteria (Porphyromonas gingivalis) are killed over many consecutive waves of attacks over 7 days. In contrast, eukaryote cell associations, upon contact with the insect membrane, lead to a formation of integrated cell sheets (e.g., among human stem cells (SHED-MSC) and human dermal fibroblasts (HDF)). The multifunctional features of the insect membrane provide a potential natural template for man-made applications in which specific control of liquid, solid, and biological contacts is desired and required. Moreover, the planthopper wing cuticle provides a "new" natural surface with which numerous interfacial properties can be explored for a range of comparative studies with both natural and man-made materials.

Synchrotron macro ATR-FTIR microspectroscopic analysis of silica nanoparticle-embedded polyester coated steel surfaces subjected to prolonged UV and humidity exposure.

Surface modification of polymers and paints is a popular and effective way to enhance the properties of these materials. This can be achieved by introducing a thin coating that preserves the bulk properties of the material, while protecting it from environmental exposure. Suitable materials for such coating technologies are inorganic oxides, such as alumina, titania and silica; however, the fate of these materials during long-term environmental exposure is an open question. In this study, polymer coatings that had been enhanced with the addition of silica nanoparticles (SiO2NPs) and subsequently subjected to environmental exposure, were characterized both before and after the exposure to determine any structural changes resulting from the exposure. High-resolution synchrotron macro ATR-FTIR microspectroscopy and surface topographic techniques, including optical profilometry and atomic force microscopy (AFM), were used to determine the long-term effect of the environment on these dual protection layers after 3 years of exposure to tropical and sub-tropical climates in Singapore and Queensland (Australia). Principal component analysis (PCA) based on the synchrotron macro ATR-FTIR spectral data revealed that, for the 9% (w/w) SiO2NP/polymer coating, a clear discrimination was observed between the control group (no environmental exposure) and those samples subjected to three years of environmental exposure in both Singapore and Queensland. The PCA loading plots indicated that, over the three year exposure period, a major change occurred in the triazine ring vibration in the melamine resins. This can be attributed to the triazine ring being very sensitive to hydrolysis under the high humidity conditions in tropical/sub-tropical environments. This work provides the first direct molecular evidence, acquired using a high-resolution mapping technique, of the climate-induced chemical evolution of a polyester coating. The observed changes in the surface topography of the coating are consistent with the changes in chemical composition.

Effect of spatial distribution of wax and PEG-isocyanate on the morphology and hydrophobicity of starch films.

This study proposes a novel method for improving surface hydrophobicity of glycerol plasticized high amylose (HAG) films. We used polyethylene glycol isocyanate (PEG-iso) crosslinker to link HAG and three natural waxes (beeswax, candelilla wax and carnauba wax) to produce HAG+wax+PEG-iso films. The spatial distributions of wax and PEG-iso across the thickness of these films were determined using Synchrotron-based Fourier transform infrared spectroscopy. The hydrophobicity and surface morphology of the films were determined using contact angle (CA) and scanning electron microscopic measurements, respectively. The distribution patterns of wax and the PEG-iso across the thickness of the film, and the nature of crystalline patterns formed on the surface of these films were found to be the key factors affecting surface hydrophobicity. The highest hydrophobicity (CA >90°) was created when the PEG-iso was primarily distributed in the interior of the films and a hierarchical circular pinnacle structure of solidified wax was formed on the surface.

High spatial resolution infrared micro-spectroscopy reveals the mechanism of leaf lignin decomposition by aquatic fungi.

Organic carbon is a critical component of aquatic systems, providing energy storage and transfer between organisms. Fungi are a major decomposer group in the aquatic carbon cycle, and are one of few groups thought to be capable of breaking down woody (lignified) tissue. In this work we have used high spatial resolution (synchrotron light source) infrared micro-spectroscopy to study the interaction between aquatic fungi and lignified leaf vein material (xylem) from River Redgum trees (E. camaldulensis) endemic to the lowland rivers of South-Eastern Australia. The work provides spatially explicit evidence that fungal colonisation of leaf litter involves the oxidative breakdown of lignin immediately adjacent to the fungal tissue and depletion of the lignin-bound cellulose. Cellulose depletion occurs over relatively short length scales (5-15 µm) and highlights the likely importance of mechanical breakdown in accessing the carbohydrate content of this resource. Low bioavailability compounds (oxidized lignin and polyphenols of plant origin) remain in colonised leaves, even after fungal activity diminishes, and suggests a possible pathway for the sequestration of carbon in wetlands. The work shows that fungi likely have a critical role in the partitioning of lignified material into a biodegradable fraction that can re-enter the aquatic carbon cycle, and a recalcitrant fraction that enters long-term storage in sediments or contribute to the formation of dissolved organic carbon in the water column.