Apparent penetration depth in attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy of Allium cepa L. epidermis and cuticle

Comparison of Seed Morphology and Seed Coat Chemistry in Ophrys (Orchidaceae) Species

Orchidaceae is the largest flowering plant family in the world and holds significant importance in terms of biological diversity. Many of the species are found in endemic regions, serving as important indicators for the conservation of biological diversity. Therefore, research on the morphology, seed and embryo structures, chemical composition, and taxonomy of orchids is crucial for species conservation, habitat restoration, and the sustainability of natural habitats. This research involves comparing the morphometric and chemical contents of seeds belonging to certain Ophrys L. species and examining interspecies relationships. The micromorphological features of the seeds were analyzed by using light microscopy and scanning electron microscopy (SEM), while their chemical contents were compared by using Fourier transform infrared spectroscopy (FT-IR) analysis. Seed and embryo morphology, morphometric analysis, and seed coat chemistry hold diagnostic significance. In species of the Ophrys genus, features like anticlinal wall structure and periclinal wall reticulation are considered weak taxonomic characters. FT-IR analysis identifies specific chemical groups in orchid samples, revealing significant differences in absorbance values and chemical compositions among the different orchid species. Particularly, Ophrys lycia (Lycian Kaş Orchid) shows distinct separation from closely related species at peak points such as 2917 and 2850, 1743, 1515, 1240, and 1031 cm-1. Common peak points in the fingerprint region (1200- 700 cm-1) indicate similarity between O. apifera and O. reinholdii subsp. reinholdii. O. ferrum-equinum, O. mammosa subsp. mammosa, O. fusca subsp. leucadica, O. reinholdii subsp. reinholdii, and O. iricolor exhibit similar absorbance values in the range of 1500-1000 cm-1. These results provide valuable preliminary information about the structure of orchid seed coats, reticulation presence and pattern, chemical profiles, distribution, and dormancy-germination processes.

Influence of sample preparation methods on FTIR spectra for taxonomic identification of tropical trees in the Atlantic forest

The Atlantic forest is one of the world's major tropical biomes due to its rich biodiversity. Its vast diversity of plant species poses challenges in floristic surveys. Fourier transform infrared spectroscopy (FTIR) enables rapid and residue-free data collection, providing diverse applications in organic sample analysis. FTIR spectra quality depends on the sample preparation methodology. However, no research on FTIR spectroscopy methodology for taxonomy has been conducted with tropical tree species. Hence, this study addresses the sample preparation influence on FTIR spectra for the taxonomic classification of 12 tree species collected in the Serra do Mar State Park (PESM) - Cunha Nucleus - São Paulo State, Brazil. Spectra were obtained from intact fresh (FL), intact dried (DL), and heat-dried ground (GL) leaves. The spectra were evaluated through chemometrics using Principal Component Analysis (PCA), Hierarchical Cluster Analysis (HCA), and Linear Discriminant Analysis (LDA) with validation by LDA-PCA. The results demonstrate that sample preparation directly influences tropical species FTIR spectra categorization capability. The best taxonomic classification result for all techniques, validated by LDA-PCA, was obtained from GL. FTIR spectra evaluation through PCA, HCA, and LDA allow for the observation of phylogenetic relationships among the species. FTIR spectroscopy proves to be a viable technique for taxonomic evaluation of tree species in floristic exploration of tropical biomes which can complement traditional tools used for taxonomic studies.

2D foam film coating of antimicrobial lysozyme amyloid fibrils onto cellulose nanopapers

Amyloid fibrils made from inexpensive hen egg white lysozyme (HEWL) are bio-based, bio-degradable and bio-compatible colloids with broad-spectrum antimicrobial activity, making them an attractive alternative to existing small-molecule antibiotics. Their surface activity leads to the formation of 2D foam films within a loop, similar to soap films when blowing bubbles. The stability of the foam was optimized by screening concentration and pH, which also revealed that the HEWL amyloid foams were actually stabilized by unconverted peptides unable to undergo amyloid self-assembly rather than the fibrils themselves. The 2D foam film was successfully deposited on different substrates to produce a homogenous coating layer with a thickness of roughly 30 nm. This was thick enough to shield the negative charge of dry cellulose nanopaper substrates, leading to a positively charged HEWL amyloid coating. The coating exhibited a broad-spectrum antimicrobial effect based on the interactions with the negatively charged cell walls and membranes of clinically relevant pathogens (Staphylococcus aureus, Escherichia coli and Candida albicans). The coating method presented here offers an alternative to existing techniques, such as dip and spray coating, in particular when optimized for continuous production. Based on the facile preparation and broad spectrum antimicrobial performance, we anticipate that these biohybrid materials could potentially be used in the biomedical sector as wound dressings.

Active Control of Contact Angles of Various Liquids from the Response of Self-Assembled Thiol Molecules to Electric Current

The ability to change wettability in situ would realize active surfaces that can change their functionality and adapt to different environments. This article reports a new and easy method that controls surface wettability in situ. In doing so, three hypotheses were to be proven. First, thiol molecules with dipole moments at the end that were adsorbed onto gold could change the contact angles of nonpolar or slightly polar liquids when an electric current was provided at the gold surface without having to ionize the dipole. It was also hypothesized that the molecules would undergo conformation changes as their dipoles would align with the magnetic field induced by the applied current. Second, the ability to change contact angles was modified by mixing ethanethiol, a much shorter thiol with no dipole, with the abovementioned thiol molecules because it would provide space for the thiol molecules to undergo conformation changes. Third, the indirect evidence of the conformation change was verified with attenuated total reflection Fourier transform infrared (FT-IR) spectroscopy. Four thiol molecules that controlled the contact angles of deionized water and hydrocarbon liquids were identified. The abilities of those four molecules in changing the contact angles were modified by adding ethanethiol. A quartz crystal microbalance was used to infer the possible change in the distance between the adsorbed thiol molecules by investigating adsorption kinetics. The changes in FT-IR peaks with respect to applied currents were also presented as indirect evidence for the conformation change. This method was compared with other reported methods that control wettability in situ. The differences between the voltage-driven method to induce conformation changes of thiol molecules and the method presented in this paper were further discussed to emphasize that the mechanism by which the conformation change was induced in this article was most likely because of the dipole-electric current interaction.

Terahertz time-domain attenuated total reflection spectroscopy integrated with a microfluidic chip

The integration of a microfluidic chip into terahertz time-domain attenuated total reflection (THz TD-ATR) spectroscopy is highly demanded for the accurate measurement of aqueous samples. Hitherto, however little work has been reported on this regard. Here, we demonstrate a strategy of fabricating a polydimethylsiloxane microfluidic chip (M-chip) suitable for the measurement of aqueous samples, and investigate the effects of its configuration, particularly the cavity depth of the M-chip on THz spectra. By measuring pure water, we find that the Fresnel formulae of two-interface model should be applied to analyze the THz spectral data when the depth is smaller than 210 μm, but the Fresnel formula of one-interface model can be applied when the depth is no less than 210 μm. We further validate this by measuring physiological solution and protein solution. This work can help promote the application of THz TD-ATR spectroscopy in the study of aqueous biological samples.

Promotion of glyoxylic acid penetration into human hair by glycolic acid

OBJECTIVE

Glyoxylic acid (GA) is widely used as a straight perming agent for hair care products, however, advanced GA penetration-enhancing agents are desired due to the peculiar odour and hair colour fading caused by the continuous use of GA products. Hence, it is important to develop a penetration-enhancing agent that helps minimize the GA concentration. We have found that the combined use of GA and glycolic acid (GCA) has a strong hair straightening effect.

METHODS

Straightening hair test was carried out to the evaluation of the effect of additives. Liquid chromatography-mass spectrometry (LC/MS) was performed to quantify the GA penetration amount into human hair. Attenuated total reflection (ATR) Fourier transform-infrared spectroscopy (FT-IR) and FT-IR microscope were implemented to estimate the localization of GA in the hair.

RESULTS

Straightening hair tests indicated that the hair straightening effect by GA was enhanced by the presence of GCA. LC/MS results showed that the addition of GCA enhanced the amount of GA that penetrated human hair by about four times. ATR FT-IR and FT-IR microscope measurements indicated that GA was localized more in the innermost region of hair (medulla) than the cortex and cuticle. The GA accumulated in the medulla disappeared after a hair straightener treatment at 180°C due to the chemical reaction.

CONCLUSIONS

The GA penetration-enhancing effect of GCA is worth investigating to reduce the GA concentration in products for more comfortable use.

Quantitative detection of THz-ATR spectra of aqueous samples under strong-field terahertz wave

Owing to the characteristics of THz wave, the terahertz time-domain spectral (THz-TDS) system has potentials in the field of biological macromolecule detection. However, water with strong absorption effect on THz wave exists in most biological detection, so the research focus in this field is to study aqueous samples. In view of these, THz spectroscopy system has research value for qualitative and quantitative detection of α-lactose and its water-containing samples. This research used a THz-TDS system with LiNbO₃ crystal to generate strong THz wave that was used to test 0.29 mmol α-lactose samples with water content of 15 μL-930 μL by using attenuating total reflection (ATR) prism. The absorption peak at 0.53 THz is detected, and with the increase of water content, the curve of absorption spectrum is observed to move up on the whole. This research has a guiding role for the test and improvement of water content limit in this field.

New approaches with ATR-FTIR, SEM, and contact angle measurements in the adaptation to extreme conditions of some endemic Gypsophila L. taxa growing in gypsum habitats

Gypsophila L. taxa growing on gypsum soils have to withstand limiting and restrictive conditions for plant life. This study aims to identify functional mechanisms determine the main functional groups in the vegetative and reproductive organs of some endemic Gypsophila taxa growing in gypsum soils, as well as to understand the relationship between the hidrophobicities and their micromorphological structures of the leaves of these plants grown in arid conditions. In this context, a series of Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR), water contact angle (CA) measurements, and scanning electron microscopy (SEM) analyses were performed that may help to understand the survival mechanisms of Gypsophila eriocalyx Boiss., Gypsophila germanicopolitana Hub.-Mor. and Gypsophila simonii Hub.-Mor. growing in gypsum habitats. Our results showed the presence of O-H and C-O stretching bands belong to gypsum and calcium oxalate in the roots, stems, leaves and flowers of Gypsophila taxa is thought to be a way of tolerating the excess Ca and sulphate in the extreme habitat where these species grow. Leaves of Gypsophila taxa showed CAs above 90°, which indicates that G. eriocalyx, G. germanicopolitana, and G. simonii were hydrophobic. This study offers new approaches to understanding the adaptation of Gypsophila taxa to the extreme conditions typical of gypsum soils. The characterization of gypsum plants such as Gypsophila taxa, whose mechanisms for competition and survival on gypsum are still not fully understood, is very important in terms of shedding light on the adaptation of endemic plants to gypsum habitats.

Assessing Fire-Damage in Historical Papers and Alleviating Damage with Soft Cellulose Nanofibers

The conservation of historical paper objects with high cultural value is an important societal task. Papers that have been severely damaged by fire, heat, and extinguishing water, are a particularly challenging case, because of the complexity and severity of damage patterns. In-depth analysis of fire-damaged papers, by means of examples from the catastrophic fire in a 17th-century German library, shows the changes, which proceeded from the margin to the center, to go beyond surface charring and formation of hydrophobic carbon-rich layers. The charred paper exhibits structural changes in the nano- and micro-range, with increased porosity and water sorption. In less charred areas, cellulose is affected by both chain cleavage and cross-linking. Based on these results and conclusions with regard to adhesion of auxiliaries, a stabilization method is developed, which coats the damaged paper with a thin layer of cellulose nanofibers. It enables the reliable preservation of the paper and-most importantly-retrieval of the contained historical information: the nanofibers form a flexible, transparent film on the surface and adhere strongly to the damaged matrix, greatly reducing its fragility, giving it stability, and enabling digitization and further handling.

Biomimetic 3D Environment Based on Microgels as a Model for the Generation of Drug Resistance in Multiple Myeloma

The development of three-dimensional environments to mimic the in vivo cellular response is a problem in the building of disease models. This study aimed to synthesize and validate three-dimensional support for culturing monoclonal plasma cells (mPCs) as a disease model for multiple myeloma. The three-dimensional environment is a biomimetic microgel formed by alginate microspheres and produced on a microfluidic device whose surface has been functionalized by a layer-by-layer process with components of the bone marrow’s extracellular matrix, which will interact with mPC. As a proof of concept, RPMI 8226 cell line cells were cultured in our 3D culture platform. We proved that hyaluronic acid significantly increased cell proliferation and corroborated its role in inducing resistance to dexamethasone. Despite collagen type I having no effect on proliferation, it generated significant resistance to dexamethasone. Additionally, it was evidenced that both biomolecules were unable to induce resistance to bortezomib. These results validate the functionalized microgels as a 3D culture system that emulates the interaction between tumoral cells and the bone marrow extracellular matrix. This 3D environment could be a valuable culture system to test antitumoral drugs efficiency in multiple myeloma.

Comparison of polyvinyl alcohol films reinforced with cellulose nanofibers derived from oil palm by impregnating and casting methods

Cellulose nanofibers (CNFs) derived from oil palm trees were utilized to reinforce polyvinyl alcohol (PVA) films by either casting or impregnating. CNFs derived from trunks of the oil palm tree were dispersed well in a PVA film by the casting method. Using the impregnating method, however, a sandwich construction with CNFs and PVA was obtained, which was confirmed using attenuated total reflectance Fourier transform infrared spectroscopy. The thermal stability, tensile strength, and Young's moduli of the PVA/CNF nanocomposite films were increased by compounding CNFs at different concentrations using both the casting and impregnating methods. However, the impregnated nanocomposite films showed higher thermal melting temperature and higher tensile toughness than those obtained by the casting method. No obvious differences appeared in the X-ray diffraction patterns or thermal decomposition behavior between the impregnated and cast nanocomposite films. In addition, adding CNFs was confirmed to increase the crystallinity of PVA.

Colloidal assembly of polydisperse particle blends during drying

In this work, we synthesize a polydisperse aqueous colloidal system composed of small and large zwitterionic particles, as well as medium sized standard acrylic particles. By assembling these dispersions into films by drying, we show using atomic force microscopy (AFM) how their top surfaces can be mostly covered by zwitterionic groups for a wide range of evaporation rates. We probe underneath the top film surface using Fourier-transform infrared (FTIR) spectroscopy - attenuated total reflection (ATR), observing that the content in zwitterionic particles of the film upper layer increases for faster evaporation rates. We show how polydisperse systems hold great potential to overcome the evaporation rate dependence of size segregation processes in drying colloidal blends, and we provide further insights into the assembly mechanisms involved. Polydisperse blends enhance the robustness of such processes for application in coatings and other soft products where evaporation rate can not be tuned.

Accelerated Ageing Procedures to Assess the Stability of an Unconventional Acrylic-Wax Polymeric Emulsion for Contemporary Art

This research evaluates the stability of an aqueous emulsion of acrylic copolymers and waxes. Edelwachs, generally applied on wood, has been recently used as an unconventional medium in contemporary painting. Through Pyrolysis-Gas Chromatography-Mass Spectrometry (Py-GC-MS) and Fourier Transformed Infrared Attenuated Total Reflectance (FT-IR-ATR) analyses, the composition of Edelwachs was defined as a mixture of acrylic polymers (MA, MMA, nBA, nBMA), Carnauba and microcrystalline waxes and additives. Mock-ups-obtained mixing Edelwachs with titanium white, zinc white and ultramarine blue were subjected to UV, high temperatures, and high relative humidity accelerated ageing. The effect of the ageing procedures was evaluated through optical microscopy, colourimetric measurements, FT-IR-ATR, Thermogravimetry and Differential Scanning Calorimetry (TG-DSC) and wettability measures. FT-IR-ATR spectra do not show significant variations in terms of chemical stability, indicating a fair stability of Edelwachs as a painting binder. UV and high temperature treatments show the most relevant effects in terms of colorimetric changes (increasing of b*) and thermal stability. The TG-DSC highlights the influence of the pigments (specifically zinc white) mainly on the thermal behaviour of the acrylates. The unexpected decrease of wettability of the paint films, registered after ageing, may indicate a possible phase separation among acrylates and waxes.