High voltage atmospheric cold plasma modification of bovine serum albumin

Combatting the antigenicity of common ragweed pollen and its primary allergen Amb a 1 with cold atmospheric pressure air plasma

Airborne allergens, especially those originating from various types of pollen, significantly compromise the health and well-being of individuals on a global scale. Here, cold atmospheric pressure plasma (CAP) created in ambient air was used to treat highly allergenic and invasive Ambrosia artemisiifolia pollen. Immunoassays were used to evaluate the impact of CAP on the principal A. artemisiifolia allergen Amb a 1, demonstrating that > 90 % reduction in antigenicity could be achieved. Chemical analyses using Fourier Transform infrared revealed that CAP induced significant alterations to proteins on the surface of pollen grains, resulting in a 43 % increase in the amide I peak area and a 57 % increase in the amide II peak area. These findings were corroborated by Raman and X-ray photoelectron spectroscopy, which indicated that the protein modifications induced by CAP were due to carbonylation and nitration/nitrosylation processes. Beyond protein transformations, CAP also induced notable oxidation and modification of lipid-like compounds, polysaccharides and sporopollenin. Evident transformations at the chemical level translated into morphological changes at the grain surface, manifesting as increased roughness via significant outer-layer etching. These findings underscore the potential of CAP technology as a viable approach for mitigating against the allergenicity of pollen, providing a deeper understanding into the underlying chemical mechanisms.

Atmospheric cold plasma as a novel approach to remediating microplastics pollution in water

Microplastics (MPs) have become an environmental and health threat to aquatic species and humans because they are small and can easily reach water bodies for municipal and agricultural uses. MPs have been traced in food commodities and products derived from animals and even found in bottles of drinking water. Current treatment techniques for permanently destroying MPs require high energy inputs and thus are generally cost-inefficient. Atmospheric cold plasma (ACP) is a low-cost energy-efficient technology to produce highly reactive species that can induce physicochemical changes in plastic polymers. This study, for the first time, used ACP as a novel method for MPs treatment. Polypropylene (PP) and low-density polyethylene (LDPE) were used to prepare model MPs. The effects of plasma working gas (oxygen, nitrogen, or their mixture) and post-ACP treatment storage (24 h) on MPs were studied. ACP treatments for 30 min successfully degraded both MPs, by 1.4-11.3% in weight. PP MPs had larger weight reduction than LDPE and the ACP of mixture gas was most effective. PP MPs also showed increased carbonyl index after treatments, to up to 6.89, indicating hydrolytic degradation. For LDPE MPs, oxygen ACP caused more oxidation, but storage did not have an enhancing effect. The results of physicochemical analyses indicated that MPs degradation by ACP was possibly mainly through oxidative and hydrolytic reactions, but further characterizations are needed. This study proves that ACP is a promising strategy to remediate MPs pollution, and thus has great potential for addressing the severe challenges of MPs that the food and agriculture sectors are currently facing.

Gas plasmas technology: from biomolecule redox research to medical therapy

Physical plasma is one consequence of gas ionization, i.e. its dissociation of electrons and ions. If operated in ambient air containing oxygen and nitrogen, its high reactivity produces various reactive oxygen and nitrogen species (RONS) simultaneously. Technology leap innovations in the early 2010s facilitated the generation of gas plasmas aimed at clinics and operated at body temperature, enabling their potential use in medicine. In parallel, their high potency as antimicrobial agents was systematically discovered. In combination with first successful clinical trials, this led in 2013 to the clinical approval of first medical gas plasma devices in Europe for promoting the healing of chronic and infected wounds and ulcers in dermatology. While since then, thousands of patients have benefited from medical gas plasma therapy, only the appreciation of the critical role of gas plasma-derived RONS led to unraveling first fragments of the mechanistic basics of gas plasma-mediated biomedical effects. However, drawing the complete picture of effectors and effects is still challenging. This is because gas plasma-produced RONS not only show a great variety of dozens of types but also each of them having distinct spatio-temporal concentration profiles due to their specific half-lives and reactivity with other types of RONS as well as different types of (bio) molecules they can react with. However, this makes gas plasmas fascinating and highly versatile tools for biomolecular redox research, especially considering that the technical capacity of increasing and decreasing individual RONS types holds excellent potential for tailoring gas plasmas toward specific applications and disease therapies.

Investigating the impact of inbuilt cold atmospheric pressure plasma on molecular assemblies of tryptophan enantiomers: in vitro fabrication of self-assembled supramolecular structures

The advancements in understanding the phenomenon of plasma interactions with matter, coupled with the development of CAPP devices, have resulted in an interdisciplinary research topic of significant importance. This has led to the integration of various fields of science, including plasma physics, chemistry, biomedical sciences, and engineering. The reactive oxygen species and reactive nitrogen species generated from cold atmospheric plasma on interaction with biomolecules like proteins and peptides form various supramolecular structures. CAPP treatment of amino acids, which are the fundamental building blocks of proteins, holds potential in creating self-assembled supramolecular architectures. In this work, we demonstrate the process of self-assembly of aromatic amino acid tryptophan (Trp) enantiomers (l-tryptophan and d-tryptophan) into ordered supramolecular assemblies induced by the reactive species generated by a cold atmospheric pressure helium plasma jet. These enantiomers of tryptophan form organized structures as evidenced by FE-SEM. To assess the impact of CAPP treatment on the observed assemblies, we employed various analytical techniques such as zeta potential, dynamic light scattering and FTIR spectroscopy. Also, photoluminescence and time-resolved lifetime measurements revealed the transfiguration of individual Trp enantiomers. The LC-ESI-QTOF-MS analysis demonstrated that CAPP irradiation led to the incorporation of oxygenated ions into the pure Trp molecule. These studies of the self-assembly of Trp due to ROS and RNS interactions will help us to understand the assembly environment. This knowledge may be utilized to artificially design and synthesize highly ordered functional supramolecular structures using CAPP.

Current and Potential Applications of Atmospheric Cold Plasma in the Food Industry

The cost-effectiveness and high efficiency of atmospheric cold plasma (ACP) incentivise researchers to explore its potentials within the food industry. Presently, the destructive nature of this nonthermal technology can be utilised to inactivate foodborne pathogens, enzymatic ripening, food allergens, and pesticides. However, by adjusting its parameters, ACP can also be employed in other novel applications including food modification, drying pre-treatment, nutrient extraction, active packaging, and food waste processing. Relevant studies were conducted to investigate the impacts of ACP and posit that reactive oxygen and nitrogen species (RONS) play the principal roles in achieving the set objectives. In this review article, operations of ACP to achieve desired results are discussed. Moreover, the recent progress of ACP in food processing and safety within the past decade is summarised while current challenges as well as its future outlook are proposed.

Effect of atmospheric pin-to-plate cold plasma on oat protein: Structural, chemical, and foaming characteristics

The impact of novel pin-to-plate atmospheric cold plasma was investigated with input voltage (170 V, 230 V) and exposure time (15 & 30 min) on oat protein by studying structural (FTIR, circular dichroism (CD), UV-vis, Fluorescence), morphological (particle size analysis, SEM, turbidity), chemical (pH, redox potential (ORP), ζ potential, carbonyl, sulfhydryl, surface hydrophobicity), and foaming characteristics. The plasma treatment reduced the pH while increasing the ORP of the dispersions. These ionic environment changes affected the ζ potential and particle size leading to the formation of larger aggregates (170-15; 230-15) and distorted smaller ones (170-30; 230-30) as confirmed by SEM. The FTIR spectra showed reduced intensity at specific amide bands (1600-1700 cm^-1) and also an increase in carbonyl stretching (1743 cm^-1) representing oxidative carbonylation (increase in carbonyl content). Thus, the partial exposure of hydrophobic amino acids increases surface hydrophobicity. The altered secondary structure (rise in α-helix, decrement in β-sheets and turns), and tertiary structures were observed in circular dichroism (CD) and UV absorbance and fluorescence characteristics of proteins respectively. Furthermore, the increase in free sulfhydryl content and disulfide content was highly affected by the plasma treatments due to observed protein unfolding and aggregations. Besides, the increased solubility and reduced surface tension contributed to the improved foaming characteristics. Thus, plasma processing influences protein structure affecting their characteristics and other functionalities.

Cold plasma as a pre-treatment for processing improvement in food: A review

Thermal processes can be very damaging to the nutritional and sensory quality of foods. Non-thermal technologies have been applied to reduce the impact of heat on food, reducing processing time and increasing its efficiency. Among many non-thermal technologies, cold plasma is an emerging technology with several potential applications in food processing. This technique can be used to preserve and sanitize food products, and act as a pre-treatment for drying, extraction, cooking, curing, and hydrogenation of foods. Furthermore, the reacting plasma species formed during the plasma application can change positively the sensory and nutritional aspects of foods. The aim of this review is to analyze the main findings on the application of cold plasma as a pre-treatment technology to improve food processing. In its current maturity stage, the cold plasma technology is suitable for reducing drying time, increasing extraction efficiency, as well as curing meats. This technology can convert unsaturated into saturated fats, without forming trans isomers, which can be an alternative to healthier foods. Although many advantages come from cold plasma applications, this technology still has several challenges, such as the scaling up, especially in increasing productivity and treating foods with large formats. Optimization and control of the effects of plasma on nutritional and sensory quality are still under investigation. Further improvement of the technology will come with a higher knowledge of the effects of plasma on the different chemical groups present in foods, and with the development of bigger or more powerful plasma systems.

Insights into the interaction between the kusaginin and bovine serum albumin: Multi-spectroscopic techniques and computational approaches

Kusaginin, as a phenylethanoid glycoside, which has exhibited wide antioxidant and antimicrobial properties. The molecular mechanism underlying the broad biological activities of kusaginin has not yet been well documented. In this paper, the interaction of kusaginin with bovine serum albumin (BSA) has been explored by fluorescence spectra, UV-vis absorption spectra, and circular dichroism (CD) spectra along with computational approaches. The fluorescence experiments showed that kusaginin could strongly quench the intrinsic fluorescence of BSA through both dynamic and static quenching mechanisms. The thermodynamic analysis suggested that hydrophobic force was the main force in stabilizing the BSA-kusaginin complex. In addition, conformation changes of BSA were observed from three-dimensional and synchronous fluorescence spectra, UV spectra, and CD spectra under experimental conditions. All these experimental results have been complemented and validated by the molecular docking and dynamic simulation studies, which revealed that kusaginin was bound on the hydrophobic cavity in subdomain IIA of BSA and formed a stable BSA-kusaginin complex. Finally, density functional theory (DFT) calculation further implied that hydrogen bonds also support stabilizing the BSA-kusaginin complex. This research may aid in understanding the pharmacological characteristics of kusaginin and provide a vital reference modeling for the design of analogues drugs.

Investigation on the impact of quality characteristics and storage stability of foxtail millet induced by air cold plasma

The aim of this work was to investigate the effects of dielectric barrier discharge-air cold plasma (DBD-ACP, 15-35 kV, 2-12 min) on the quality of foxtail millets. The L and b* values were evaluated by a digital colorimeter representing that the color of millets was significantly changed at 25 kV for 4-12 min or at 35 kV for 2-12 min. The results were consistent with the change of total yellow pigment in millets, indicating that DBD-ACP damaged the carotenoids if the treatment condition was too high. The activity of lipoxygenase and lipase, involving the oxidation and hydrolysis of lipids of millet, decreased significantly induced by DBD-ACP. For example, the lipoxygenase and lipase activity of Mizhi millet was decreased from 44.0 to 18.7 U g^-1min^-1, 56.0-15.1 U/(mg pro) (p<0.05) after being exposed to 25 kV for 2-12 min, respectively. Changes of color, lipoxygenase and lipase activity, and malondialdehyde content of millets were determined during accelerated storage (40 ± 2°C and 75% Relative Humidity) for 15 days after being treated by DBD-ACP under 15 and 25 kV for 4 min. Results showed that millets treated by DBD-ACP at 15 kV kept a better color with lower malondialdehyde content, and lower lipoxygenase and lipase activity compared to control. This work implied that DBD-ACP is an underlying approach for the storage of foxtail millets.

Cold atmospheric plasma driven self-assembly in serum proteins: insights into the protein aggregation to biomaterials

The self-assembly of proteins is crucial in many biomedical applications. This work deals with understanding the role of cold atmospheric plasma (CAP) on the self-assembly of two different proteins present in the serum - BSA and hemoglobin and to elucidate the process associated with the direct application of physical plasma on or in the human (or animal) body, which has implications in therapeutics. The work has been corroborated by several spectroscopic studies such as fluorescence spectroscopy, circular dichroism spectroscopy, and SEM analysis. Through steady-state fluorescence spectroscopy and by following the tryptophan fluorescence, we observed that the emission intensity was quenched for the protein when treated with plasma radiation. Circular dichroism spectroscopy revealed that the structure of the protein was altered both in the case of BSA and hemoglobin. N-Acetyl tryptophanamide (NATA), which resembles the tryptophan in the protein, was treated with CAP and we observed the similar quenching of fluorescence as in the proteins, indicating that the protein underwent self-assembly. Time-resolved fluorescence spectroscopy with a decrease in the lifetime revealed that the protein self-assembly was promoted with CAP treatment, which was also substantiated by SEM micrographs. The ROS/RNS produced in the CAP has been correlated with the protein self-assembly. This work will help to design protein self-assembled systems, and in the future, may bring possibilities of creating novel biomaterials with the help of plasma radiation.