Guanidine Hydrochloride Research Articles

Addressing Acid-Catalyzed Deamidation and the Solubility of Hydrophobic Peptides in Multi-Attribute Method Workflows.

Recently, we introduced an optimized and automated Multi-Attribute Method (MAM) workflow, which (a) significantly reduces the number of missed cleavages using an automated two-step digestion procedure and (b) dramatically reduces chromatographic peak tailing and carryover of hydrophobic peptides by implementing less retentive reversed-phase column chemistries. Here, further insights are provided on the impact of postdigest acidification and the importance of maintaining hydrophobic peptides in solution using strong chaotropic agents after digestion. We demonstrate how oxidation can significantly increase the solubility of hydrophobic peptides, a fact that can have a profound impact on quantitation of oxidation levels if care is not taken in MAM workflows. We conclude that (a) postdigestion acidification can result in significant acid-catalyzed deamidation during storage in an autosampler at 5 °C and (b) a strong chaotropic agent, such as guanidine hydrochloride, is critical for preventing loss of hydrophobic peptides through adsorption, which can result in (sometimes extreme) biases in quantitation of tryptophan oxidation levels. An optimized method is presented, which effectively addressed acid-catalyzed deamidation and solubility of hydrophobic peptides in MAM workflows.

Deep coverage and quantification of the bone proteome provides enhanced opportunities for new discoveries in skeletal biology and disease.

Dysregulation of cell signaling in chondrocytes and in bone cells, such as osteocytes, osteoblasts, osteoclasts, and an elevated burden of senescent cells in cartilage and bone, are implicated in osteoarthritis (OA). Mass spectrometric analyses provides a crucial molecular tool-kit to understand complex signaling relationships in age-related diseases, such as OA. Here we introduce a novel mass spectrometric workflow to promote proteomic studies of bone. This workflow uses highly specialized steps, including extensive overnight demineralization, pulverization, and incubation for 72 h in 6 M guanidine hydrochloride and EDTA, followed by proteolytic digestion. Analysis on a high-resolution Orbitrap Eclipse and Orbitrap Exploris 480 mass spectrometer using Data-Independent Acquisition (DIA) provides deep coverage of the bone proteome, and preserves post-translational modifications, such as hydroxyproline. A spectral library-free quantification strategy, directDIA, identified and quantified over 2,000 protein groups (with ≥ 2 unique peptides) from calcium-rich bone matrices. Key components identified were proteins of the extracellular matrix (ECM), bone-specific proteins (e.g., secreted protein acidic and cysteine rich, SPARC, and bone sialoprotein 2, IBSP), and signaling proteins (e.g., transforming growth factor beta-2, TGFB2), and lysyl oxidase homolog 2 (LOXL2), an important protein in collagen crosslinking. Post-translational modifications (PTMs) were identified without the need for specific enrichment. This includes collagen hydroxyproline modifications, chemical modifications for collagen self-assembly and network formation. Multiple senescence factors were identified, such as complement component 3 (C3) protein of the complement system and many matrix metalloproteinases, that might be monitored during age-related bone disease progression. Our innovative workflow yields in-depth protein coverage and quantification strategies to discover underlying biological mechanisms of bone aging and to provide tools to monitor therapeutic interventions. These novel tools to monitor the bone proteome open novel horizons to investigate bone-specific diseases, many of which are age-related.

Microwave Synthesized Hydrophilic 4‐Oxo‐2‐phenylquinazoline‐3(4H)–carboximidamide and –Carboxamide as Privileged Small Molecule Scaffolds with Anti‐HIV‐1 Activities

AbstractOpportunistic infections like tuberculosis (TB) are prevalent in HIV‐infected individuals. In an approach to introducing an industrial‐scale microwave‐assisted production of agents having both antiviral and antibacterial properties, a set of hydrophilic 2,3‐substituted quinazolinones, 4‐oxo‐2‐phenylquinazoline‐3(4H)‐carboximidamide (Qg) and 4‐oxo‐2‐phenylquinazoline‐3(4H)‐carboxamide (Qu), were afforded in encouraging yields. They were obtained by treating 2‐benzamidobenzoyl chloride with guanidine hydrochloride or urea in the presence of potassium carbonate in DMF. DFT calculations were employed for geometrical optimization and vibrational frequency analysis of the compounds. Free energies of solvation (ΔGsol) of Qg, and Qu calculated using DFT lend evidence in support of their hydrophilicity The anti‐HIV‐1 activities of the small‐molecule quinazolinone derivatives Qg and Qu were investigated. The synthons under in vitro conditions inhibit the entry of HIV in receptor cells with low cytotoxicity (EC50=50.53 nM for Qu and EC50=97.92 nM for Qg). The study identifies the antiviral properties of the two benzo‐fused pyrimidine derivatives, which were earlier reported to have antitubercular activity. Our findings indicate the scope for further synthetic explorations of these quinazolinone scaffolds that can lead to developing promising alternatives in drug design, pharmaceutics, and clinical research.

OBTAINING AND INVESTIGATION OF THE BIOLOGICAL ACTIVITY OF GUANIDINE COMPLEXES WITH PECTIN POLYSACCHARIDES

Pectin polysaccharides, due to the presence of reactive carboxyl functional groups in the structure, have a high complexing ability. This expands the scope of their practical application for the development of new biologically active substances. In this work, we propose the preparation of complex compounds based on sodium pectate and guanidine hydrochloride. By varying the molar amount of guanidine in relation to the acid groups of the polysaccharide matrix, samples were obtained that differ in the degree of substitution, the content of the amino derivative of the compound, and the inherent viscosity. The optimal ratio of the starting compounds was determined, at which the limiting amount of guanidine is bound to -COO- groups of pectin macromolecules. The structure of the resulting complexes was studied by FTIR spectroscopy. It has been established that the interaction of guanidine with polysaccharide carboxyls is accompanied by a change in the intensity of the absorption bands corresponding to the ionized acid group. Also, the binding of guanidine to the polysaccharide matrix through ionic bonds has been proven by carrying out the hydrolytic cleavage of the complex compound in an acidic medium. It is shown that with an increase in the hydrolysis time from 3 to 24 h, a gradual decrease in the initial degree of substitution of the complex compound is observed. The antimicrobial properties of polymer complexes with different characteristics against Staphylococcus aureus and Escherichia coli were studied.

Lyoprotectants for Lactobacillus brevis B144 and their capability to maintain the expression of surface layer protein

Lactobacillus brevis as a probiotic has been reported to facilitate micronutrient absorption such as minerals (zinc, calcium, magnesium) into the intestine through the surface layer protein (Slp). Negatively charged-Slp from the bacteria that adheres on the intestinal mucosa binds to the positively charged-minerals, e.g., calcium, zinc, iron, magnesium and potassium via an ionic interaction. In this study, several sugar-based lyoprotectants (glucose, galactose, and lactose) and skim milk were implemented in the L. brevis B144 InaCC freeze drying. The dried L. brevis B144 InaCC was kept in the refrigerator up to three months and monthly tested for the cell viability. The dried L. brevis B144 InaCC was re-culture and then its Slp was isolated using 8 M guanidine hydrochloride. In general, combinations of skim milk and the sugar-based lyoprotectant provided higher protection than the skim milk alone. Meanwhile, without any lyoprotectant, the L. brevis B144 InaCC lose its ability to grow. In regards to maintain the capability of the Slp expression, the L. brevis B144 InaCC which was protected with the combination of 20% skim milk and 10% galactose showed the highest protein expression level among the other lyoprotectants.

Jamun Seed-Derived Nitrogen-Doped Carbon Dots: A Novel Microwave-Assisted Synthesis for Ultra-Bright Fluorescence and Mn7+ Detection.

For the synthesis of heteroatom-doped carbon nanostructures, biomass is considered asa promising option. Utilizing the microwave-assisted method, we have demonstrated an easy and straightforward one-pot synthesis of nitrogen-doped luminous carbon dots (NCDs) from jamun seed powder and guanidine hydrochloride. Structural and morphological analyses were performed using various analytical techniques. Under ultraviolet light of 315 nm, NCDs emit a bright blue fluorescence, possess a high quantum yield of 26.90%, exhibit strong water dispersion, and demonstrated excellent stability. The average particle size of the NCDs was found to be 7.5±1.2 nm, with a spherical shape. NCDs exhibit high selectivity and sensitivity in fluorescence quenching when exposed to Mn7+ ions. Over a concentration range of 2-30 µM, the fluorescence response (F0/F) shows a linear relationship with Mn7+ concentration, with a detection limit of 0.81 µM. The probe exhibited negligible interference and proved to be effective in accurately quantifying Mn7+ in spiked real-water samples.

Expand and Sensitize: Guanidine‐Functionalized Exopolysaccharide Nanoparticles Cause Bacterial Cell Expansion and Antibiotic Sensitization

AbstractConventional antibacterial agents and mechanisms are frequently observed to be ineffective due to the evolution of bacteria to the strains with stronger antibiotic resistance, and hence developing alternative antibacterial materials and mechanisms is urgently needed. Here, guanidine‐functionalized exopolysaccharide (EPS) nanoparticles (termed EPGNs) with durable antibacterial and antibiofilm activities are developed. Very interestingly, the EPGNs obtained by the reaction of EPS, epichlorohydrin, and polyhexamethylene guanidine hydrochloride exhibit an unconventional antibacterial mechanism, i.e., they can induce substantial bacterial cell expansion by upregulating the SulA and DicB proteins that are responsible for cell division inhibition, along with the increase of reactive oxygen species production, bacterial cell surface disruption, and bacterial ribosomal RNA degradation. The transcriptome analysis reveals that EPGNs can hinder cell motility, induce loss of cell integrity, decrease the resistance of bacteria to oxidative stress, and finally lead to cell death. Moreover, EPGNs can effectively accelerate the bacteria‐infected wound healing. This work provides the first example that nanomaterials can cause bacterial cell expansion by affecting intracellular structures and inhibiting cell division, and it may inspire other researchers to investigate the effect of antibacterial materials on the change of bacterial volume and design unconventional antibacterial materials/strategies.

Synthesis of 2‐amino‐4‐aryl‐6‐styrylpyrimidines through aza‐Michael addition/nucleophilic addition/dehydrogenation cascade reactions

AbstractAn efficient method for the synthesis of 2‐amino‐4‐aryl‐6‐styrylpyrimidines by the reactions of various distyryl ketones with guanidine hydrochloride through aza‐Michael addition/nucleophilic addition/dehydrogenation cascade processes is described. The salient features of this protocol are the use of easy‐to‐obtain substrates, transition‐metal‐free system, mild reaction conditions, high atom economy, wide substrate scope, satisfactory yield, and simple work‐up procedures.

Comparative Study of Guanidine-, Acetamidine- and Urea-Based Chloroaluminate Electrolytes for an Aluminum Battery.

Aluminum-based batteries are a promising alternative to lithium-ion as they are considered to be low-cost and more friendly to the environment. In addition, aluminum is abundant and evenly distributed across the globe. Many studies and Al battery prototypes use imidazolium chloroaluminate electrolytes because of their good rheological and electrochemical performance. However, these electrolytes are very expensive, and so cost is a barrier to industrial scale-up. A urea-based electrolyte, AlCl3:Urea, has been proposed as an alternative, but its performance is relatively poor because of its high viscosity and low conductivity. This type of electrolyte has become known as an ionic liquid analogue (ILA). In this contribution, we proposed two Lewis base salt precursors, namely, guanidine hydrochloride and acetamidine hydrochloride, as alternatives to the urea-based ILA. We present the study of three ILAs, AlCl3:Guanidine, AlCl3:Acetamidine, and AlCl3:Urea, examining their rheology, electrochemistry, NMR spectra, and coin-cell performance. The room temperature viscosities of both AlCl3:Guanidine (52.9 cP) and AlCl3:Acetamidine (76.0 cP) were significantly lower than those of the urea-based liquid (240.9 cP), and their conductivities were correspondingly higher. Cyclic voltammetry (CV) and linear sweep voltammetry (LSV) showed that all three electrolytes exhibit reversible deposition/dissolution of Al, but LSV indicated that AlCl3:Guanidine and AlCl3:Acetamidine ILAs have superior anodic stability compared to the AlCl3:Urea electrolyte, as evidenced by anodic potential limits of +2.23 V for both AlCl3:Guanidine and AlCl3:Acetamidine and +2.12 V for AlCl3:Urea. Coin-cell tests showed that both AlCl3:Guanidine and AlCl3:Acetamidine ILA exhibit a higher Coulombic efficiency (98 and 97%, respectively) than the AlCl3:Urea electrolyte system, which has an efficiency of 88% after 100 cycles at 60 mA g-1. Overall, we show that AlCl3:Guanidine and AlCl3:Acetamidine have superior performance when compared to AlCl3:Urea, while maintaining low economic cost. We consider these to be valuable alternative materials for Al-based battery systems, especially for commercial production.

Prospects for Application of Guanidine-Containing Organomineral Complexes as Biocidal Functional Additives for Waterborne Polymer Materials

The possibility of using organomineral complexes of polyhexamethylene guanidine hydrochloride as a functional additive for a waterborne paint based on polyvinyl acetate has been investigated. Organomineral complexes containing 20 and 30 wt % guanidine polymer have been obtained, with intercalation of polyguanidine chains into the interlayer space of montmorillonite being observed. It has been revealed that the stability of the polymer film to water is retained when organomineral complexes are introduced into a polyvinyl acetate dispersion, whereas the water resistance of the film sharply decreases when free polyguanidine is added. There was no significant influence of organomineral complexes on the rheological characteristics of the dispersion and its sedimentation stability. Testing of waterborne paints with various additives has shown that introduction of organomineral complexes into the material prevents the coating from fouling by biofilms of gram-positive bacteria Staphylococcus aureus and Rhodococcus erythropolis, with the hardness, water resistance, and water-vapor transmission of the coatings being retained at a satisfactory level.

Polyhexamethylene guanidine hydrochloride as promising active ingredient for oral antiseptic products to eliminate microorganisms threatening the health of endangered wild cats: a comparative study with chlorhexidine digluconate.

The aim of this study was to evaluate the antimicrobial efficacy of polyhexamethylene hydrochloride guanidine (PHMGH) compared to chlorhexidine digluconate (CLX) for use as an oral antiseptic during dental procedures in wild cats. This research is crucial due to limited information on the diversity of oral microorganisms in wild cats and the detrimental local and systemic effects of oral diseases, which highlights the importance of improving prevention and treatment strategies. Samples were collected from the oral cavities of four Puma concolor, one Panthera onca, and one Panthera leo, and the number of colony-forming units per milliliter (CFU/mL) was counted and semi-automatically identified. The antimicrobial susceptibility profile of bacterial isolates was determined using minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and time-kill kinetics of PHMGH and CLX. A total of 16 bacterial isolates were identified, consisting of six Gram-positive and 10 Gram-negative. PHMGH displayed MIC and MBC from 0.24 to 125.00 μg/mL, lower than those of CLX against three isolates. Time-kill kinetics showed that PHMGH reduced the microbial load by over 90% for all microorganisms within 30 min, whereas CLX did not. Only two Gram-positive isolates exposed to the polymer showed incomplete elimination after 60 min of contact. The results could aid in the development of effective prevention and treatment strategies for oral diseases in large felids. PHMGH showed promising potential at low concentrations and short contact times compared to the commercial product CLX, making it a possible active ingredient in oral antiseptic products for veterinary use in the future.

Small conformational changes in IgG1 detected as acidic charge variants by cation exchange chromatography

Fully characterizing the post-translational modifications present in charge variants of therapeutic monoclonal antibodies (mAbs), particularly acidic variants, is challenging and remains an open area of investigation. In this study, to test the possibility that chromatographically separated acidic fractions of therapeutic mAbs contain conformational variants, we undertook a mAb refolding approach using as a case study an IgG1 that contains many unidentified acidic peaks with few post-translational modifications, and examined whether different acidic peak fractions could be generated corresponding to these variants. The IgG1 drug substance was denatured by guanidine hydrochloride, without a reducing agent present, and gradually refolded by stepwise dialysis against arginine hydrochloride used as an aggregation suppressor. Each acidic chromatographic peak originally contained in the IgG1 drug substance was markedly increased by this stepwise refolding process, indicating that these acidic variants are conformational variants. However, no conformational changes were detected by small-angle X-ray scattering experiments for the whole IgG1, indicating that the conformational changes are minor. Chromatographic, thermal and fluorescence analyses suggested that the conformational changes are a localized denaturation effect centred around the aromatic amino acid regions. This study provides new insights into the characterization of acidic variants that are currently not fully understood.

Enhancing gluten detection assay development through optimization of gliadin extraction conditions

Gluten consumption can lead to severe health conditions in certain individuals, and following a strict gluten-free diet is often the only effective treatment option. Therefore, it is crucial to develop a gluten detection method that is accurate, sensitive, and specific to ensure the absence of gluten. An important aspect of developing effective gluten detection tests is the implementation of an efficient gluten extraction method. In this study, we conducted an evaluation of various buffer conditions for gliadin extraction from both heat-treated and non-heat-treated food samples. These buffer conditions included ethanol, 2-mercaptoethanol, guanidine hydrochloride, detergents, chelating agents, and deep eutectic solvents. Among the tested conditions, a combination of 2-mercaptoethanol and guanidine hydrochloride demonstrated significantly higher extraction efficacy compared to most other conditions. Furthermore, we explored the use of a less toxic extraction buffer, choline chloride, which exhibited a 1.4-fold higher extraction efficiency than the combination of 2-mercaptoethanol and guanidine hydrochloride (p < 0.05). Choline chloride showed great potential as a preferred buffer for commercial gliadin extraction kits, suitable for both heat-treated and non-heat-treated food samples. Overall, our findings highlight the importance of optimizing the gluten extraction process to improve the accuracy and reliability of gluten detection methods, ultimately contributing to the development of effective tools for individuals following a strict gluten-free diet.

Solubility, thermodynamic investigation and molecular dynamics simulation of guanidine hydrochloride in four binary solvents

Solubilities of guanidine hydrochloride (GuHCl) in organic solvents are of great importance for its development and optimization of industrial process. The study of the dissolution characteristics of GuHCl in DMF/2-meoxyethanol/methanol/NMP + n-propanol at different temperatures were experimentally investigated by using laser monitoring method. Results showed that GuHCl solubilities were observed to be increasing with the increment in experimental temperature and rising with higher mass fraction of DMF/2-meoxyethanol/methanol/NMP. Molecular dynamics (MD) simulation technique was utilized to reveal the microscopic behaviors of GuHCl and solvent mixtures and its effect on the dissolving capability of GuHCl in involved solvent systems. Also, five thermodynamic models were selected to regress the observed GuHCl equilibrium solubility. A comparison of the experimental values with corresponding estimated data indicated that the modified Apelblat equation provided the most excellent correlation in modelling GuHCl solubility. Finally, through the analyses of enthalpy change, entropy change and Gibbs free energy change, the dissolution thermodynamic features were evaluated.

Surface modification of perovskite with guanidine hydro-chloride to improve the stability and efficiency of Cs0.2FA0.8PbI2·8Cl0.2 perovskite solar cells

Surface modification engineering has been established as a successful method for enhancing the properties of organic-inorganic perovskite solar cells (PVK–SCs). In this research, scientists employed guanidine hydrochloride (GuHCl) to modify the surface of Cs0.2FA0.8PbI2·8Cl0.2 perovskite (PVK:GuHCl) films, leading to a significant enhancement in the performance of the devices. After the surface modification, the PVK-SC demonstrated notable enhancements in its open-circuit voltage (Voc), which increased from 1.011 V to 1.056 V. Additionally, the power conversion efficiency (PCE) experienced a significant boost, surging from 13.1% to an impressive 18.6%. Additionally, the study highlighted that the reliability of the solar cell was greatly enhanced through surface engineering, as evidenced by the packaged device maintained an exceptional 90% of its initial value even after being stored at room temperature for six days.

Content of bone morphogenetic protein 2 in demineralized bone matrix prepared from different long bones and study of the osteogenic properties in vitro

To measure the concentration of bone morphogenetic protein 2 (BMP-2) in demineralized bone matrix (DBM) prepared from different long bones and to evaluate the osteoinductivity of different DBM on MC3T3-E1 cells. Different bones from the same cadaver donor were used as the initial materials for making DBM, which were divided into ulna group (uDBM), humerus group (hDBM), tibia group (tDBM), and femur group (fDBM) according to the origins, and boiled DBM (cDBM) was taken as the control group. The proteins of DBM were extracted by guanidine hydrochloride, and the concentrations of BMP-2 were determined by ELISA assay. Then the DBM were co-cultured with MC3T3-E1 cells, the proliferation of MC3T3-E1 cells was observed by cell counting kit 8 (CCK-8) assay. The osteogenic differentiation ability of MC3T3-E1 cells was qualitatively observed by alizarin red, alkaline phosphatase (ALP), and Van Gieson staining, and the osteogenic differentiation ability of MC3T3-E1 cells was quantitatively analyzed by ALP content. Linear regression was used to analyze the effect of BMP-2 concentration in DBM on ALP synthesis. There were significant differences in the concentration of BMP-2 among the DBM groups (P<0.05). The concentrations of BMP-2 in the lower limb long bone were higher than those in the upper limb long bone, and the concentration of BMP-2 in the fDBM group was about 35.5 times that in the uDBM group. CCK-8 assay showed that the cells in each group continued to proliferate within 5 days of co-culture, and the absorbance (A) values at different time points were in the order of cDBM group<uDBM group<hDBM group<tDBM group<fDBM group. After co-culture for 14 days, the expressions of ALP, calcified nodules, and collagen fibers in each group were consistent with the distribution of BMP-2 concentration in DBM. The order of ALP content from low to high was cDBM group<uDBM group<hDBM group<tDBM group<fDBM group, and the differences between the groups were significant (P<0.05). Linear regression analysis showed that =0.361+0.017x, the effect of BMP-2 concentration in DBM on cellular ALP content was significant (t=3.552, P=0.005); for every 1 ng/g increase in BMP-2 concentration, ALP content would increase by 0.017 [95%CI (0.006, 0.027)] U/100 mL. The concentration of natural BMP-2 in different long bones varies greatly, and the lower limb long bone is higher than the upper limb long bone. The harvested location of bone material was an important factor affecting the osteoinductivity of DBM.

Polar and dispersive surface tension components of water-guanidinium chloride (Gdmcl) binary mixtures

Interfacial interaction of water with guanidinium chloride (GdmCl) is crucial to understanding protein solubility and denaturing mechanism. However, molecularly resolved parameters such as polar and dispersive surface energy components of water-GdmCl mixtures remain unknown. Here, we developed a method to determine water-GdmCl mixture surface tension and its components using four different substrates including polydimethylsiloxane (PDMS), silicone, polyethylene, and polystyrene. Results show all six combinations, PDMS-silicone, PDMS-polystyrene, PDMS-polyethylene, silicone-polyethylene, silicone-polystyrene, and polyethylene-polystyrene can estimate similar trend of total surface tension, polar and dispersive components with respect to salt concentration changes. Silicone-polyethylene pairs yield the most accurate surface tension compared to others because silicone and polyethylene have large distinctive surface energy differences. Results show that polar components increase from 51 mJ/m2 to 64 mJ/m2 when salt concentration increases; dispersive components decrease from 21 mJ/m2 to 15 mJ/m2 when salt concentration increases. Total surface tension increases from 72.8 mJ/m2 to 78.1 mJ/m2 when GdmCl increases from 0% to 40 wt%. The results of this study can elucidate molecular interaction between water and GdmCl.

Ion Diffusion Management Enables All-Interface Defect Passivation of Perovskite Solar Cells.

Perovskite solar cells (PSCs) have demonstrated over 25% power conversion efficiency (PCE) via efficient surface passivation. Unfortunately, state-of-the-art perovskite post-treatment strategies can solely heal the top interface defects. Herein, we propose an ion diffusion management strategy to concurrently modulate the top interfaces, buried interfaces, and bulk interfaces (i.e., grain boundaries) of perovskite film, enabling all-interface defect passivation. Specifically, this method is enabled by applying double interactive salts of octylammonium iodide (OAI) and guanidinium chloride (GACl) onto the three-dimensional (3D) perovskite surface. We reveal that the hydrogen-bonding interaction between OA+ and GA+ decelerates the OA+ diffusion and therefore forms dimensionally broadened 2D capping layer. Additionally, the diffusion of GA+ and Cl- determines the composition of the bulk and buried interface of PSCs. As a result, we can obtain n-inter-i-inter-p, i.e., 5-layer structured PSCs with a champion PCE of 25.43% (certified 24.4%). This approach also enables the substantially improved operational stability of perovskite solar cells. This article is protected by copyright. All rights reserved.

How to better select SARS-CoV-2 preservation solution of virus nucleic acid testing.

Sampling and testing for SARS-CoV-2 is a widely recognized method for identifying patients with COVID-19. However, there is limited research available on the stability of nucleic acids in viral storage solutions. This paper investigates the components that provide better protection for virus and nucleic acid detection. The study utilized real-time quantitative fluorescent PCR to detect SARS-CoV-2 and evaluate the preservation effect and stability of SARS-CoV-2 viral storage solution under various conditions, including different guanidinium salts, brands, and storage conditions. All brands of inactivated virus preservation solutions demonstrated effective preservation and stability. However, 0.5 mol/L guanidine hydrochloride and guanidine isothiocyanate solutions exhibited poor antiseptic effects. Additionally, refrigerated storage showed better preservation compared to room temperature storage. We recommend using inactivated virus collection solution to preserve and transport samples and testing preferably within 6 hours to reduce false negatives of NAT results.

Toxicity of benzethonium chloride and polyhexamethylene guanidine hydrochloride mixtures on Daphnia carinata: synergistic and antagonistic effects at specific ratios

Throughout the coronavirus (COVID-19) pandemic, the sanitizing products benzethonium chloride (BEC) and polyhexamethylene guanidine hydrochloride (PHMG-H) were widely used; however, few studies have investigated their combined toxicity to organisms. In the present study, acute toxicity and genotoxicity of BEC, PHMG-H, and the combination of the two were investigated as endpoints using Daphnia carinata as the model organism. For individual reagents, PHMG-H was found to be more toxic than BEC in terms of both mortality and genotoxicity. DNA damage and survival rate were used as toxicity endpoints. The interaction was evaluated with the concentration addition (CA) model via toxic unit (TU) approach and additive index (AI) method in mixtures at different ratios in TU. Only the binary mixture BEC + PHMG-H at the ratio 1:9 in TU was regarded as synergistic, while all others indicated increased antagonistic effects as the proportion of BEC increased over the PHMG-H concentration. The findings here benefit understanding surrounding precisely how BEC and PHMG-H interact at different mixing ratios, and can assist with the evaluation of risk assessments for binary mixtures in aquatic ecosystems.