Preparation of calcium phosphate ion clusters through atomization method for biomimetic mineralization of enamel

Dental enamel is a mineralized extracellular matrix, and enamel defect is a common oral disease. However, the self-repair capacity of enamel is limited due to the absence of cellular components and organic matter. Efficacy of biomimetic enamel mineralization using calcium phosphate ion clusters (CPICs), is an effective method to compensate for the limited self-healing ability of fully developed enamel. Preparing and stabilizing CPICs presents a significant challenge, as the addition of certain stabilizers can diminish the mechanical properties or biosafety of mineralized enamel. To efficiently and safely repair enamel damage, this study quickly prepared CPICs without stabilizers using the atomization method. The formed CPICs were evenly distributed on the enamel surface, prompting directional growth and transformation of hydroxyapatite (HA) crystals. The study revealed that the mended enamel displayed comparable morphology, chemical composition, hardness, and mechanical properties to those of the original enamel. The approach of repairing dental enamel by utilizing ultrasonic nebulization of CPICs is highly efficient and safe, therefore indicating great promise.

Benzalkonium Chloride Poisoning in Pediatric Patients: Report of Case with a Severe Clinical Course and Literature Review

The use of disinfectants, particularly those containing quaternary ammonium compounds (QUACs), has dramatically escalated globally since the coronavirus disease 2019 pandemic. We report a case that highlights the risks associated with ingesting low-concentration QUAC solutions and emphasize the importance of effective management in resolving severe lesions without sequelae. A 17-month-old boy experienced severe respiratory failure after ingesting a disinfectant containing benzalkonium chloride (BAC). The child was initially treated at a local emergency department and was subsequently transferred to a pediatric poison center. Upon evaluation, the child was found to have grade III-A corrosive esophageal lesions and chemical pneumonitis. Several complications, including massive pneumothorax and candidemia, occurred during the clinical course of the disease. However, with timely medical intervention and appropriate supportive care, the patient completely recovered without any long-term sequelae. The properties of BAC and the comprehensive management approach may have been responsible for the patient's full recovery, despite the potentially life-threatening effects of ingesting disinfectants.

Quaternary Ammonium Compounds and Contact Dermatitis: A Review and Considerations During the COVID-19 Pandemic

The recent global pandemic has resulted in increased use of quaternary ammonium compounds (QACs). Currently, QACs are active ingredients in 292 disinfectants recommended by the US EPA for use against SARS-CoV-2. Among QACs, benzalkonium chloride (BAK), cetrimonium bromide (CTAB), cetrimonium chloride (CTAC), didecyldimethylammonium chloride (DDAC), cetrimide, quaternium-15, cetylpyridinium chloride (CPC), and benzethonium chloride (BEC) were all identified as potential culprits of skin sensitivity. Given their widespread utilization, additional research is needed to better classify their dermal effects and identify other cross-reactors. In this review, we aimed to expand our knowledge about these QACs to further dissect its potential allergic and irritant dermal effects on healthcare workers during COVID-19.

Chronic quaternary ammonium compound exposure during the COVID-19 pandemic and the impact on human health

Objective

This review examines a relevant, and underacknowledged, emerging global public health concern—the widespread exposure to quaternary ammonium compounds (QACs) during the COVID-19 pandemic. QACs are a widely used class of cationic surfactants with broad spectrum antimicrobial activity that serve as the active ingredients in antimicrobial products. While these compounds have been used for decades, the production and consumer use of QAC-containing products have steeply risen during the COVID-19 pandemic to control and prevent the spread of the SARS-Cov-2 virus. As a result, human exposure to QACs has also drastically increased.

Methods

This critical review was conducted by searching the key terms “quaternary ammonium compounds,” “disinfectants,” “COVID-19,” “SARS-Cov-2,” “human health,” and “human exposure” in the major search engines, including Google Scholar, PubMed and Science Direct.

Results

QACs are generally considered safe and effective, yet the magnitude of QAC exposure and the subsequent health effects have not been adequately investigated. Recent studies have revealed the potential for bioaccumulation of QACs in blood and tissue. Inhalation and dermal absorption of QACs are identified as the most significant exposure routes for adults, while children and infants may be significantly more vulnerable to QAC exposure and potential adverse health effects.

Conclusions

QACs are an important tool to protect individual and public health, but understanding the impact of widespread QAC exposure is vital to guide best practices for QAC use and minimize the associated health risks. These pandemic era results warrant further investigation and raise additional questions about the short-term and long-term health effects of chronic QAC exposure.

Clinical trial registration

Not applicable.

Quaternary ammonium compounds of emerging concern: Classification, occurrence, fate, toxicity and antimicrobial resistance

Amplified hygiene and precautionary measures are of utmost importance to control the spread of COVID-19 and future infection; however, these changes in practice are projected to trigger a rise in the purchase, utilisation and hence, discharge of many disinfectants into the environment. While alcohol-based, hydrogen peroxide-based, and chlorine-based compounds have been used widely, quaternary ammonium compounds (QACs) based disinfectants are of significant concern due to their overuse during this pandemic. This review presents the classification of disinfectants and their mechanism of action, focusing on QACs. Most importantly, the occurrence, fate, toxicity and antimicrobial resistance due to QACs are covered in this paper. Here we collated evidence from multiple studies and found rising trends of concern, including an increase in the mass load of QACs at a wastewater treatment plant (WWTP) by 331% compared to before the COVID-19 pandemic, as well as an increases in the concentration of 62% in residential dust, resulting in high concentrations of QACs in human blood and breast milk and suggesting that these could be potential sources of persistent QACs in infants. In addition to increased toxicity to human and aquatic life, increased use of QACs and accelerated use of antibiotics and antimicrobials during the COVID-19 pandemic could multiply the threat to antimicrobial resistance.

A broad-spectrum synthetic antibiotic that does not evoke bacterial resistance

BACKGROUND

Antimicrobial resistance (AMR) poses a critical threat to public health and disproportionately affects the health and well-being of persons in low-income and middle-income countries. Our aim was to identify synthetic antimicrobials termed conjugated oligoelectrolytes (COEs) that effectively treated AMR infections and whose structures could be readily modified to address current and anticipated patient needs.

METHODS

Fifteen chemical variants were synthesized that contain specific alterations to the COE modular structure, and each variant was evaluated for broad-spectrum antibacterial activity and for in vitro cytotoxicity in cultured mammalian cells. Antibiotic efficacy was analyzed in murine models of sepsis; in vivo toxicity was evaluated via a blinded study of mouse clinical signs as an outcome of drug treatment.

FINDINGS

We identified a compound, COE2-2hexyl, that displayed broad-spectrum antibacterial activity. This compound cured mice infected with clinical bacterial isolates derived from patients with refractory bacteremia and did not evoke bacterial resistance. COE2-2hexyl has specific effects on multiple membrane-associated functions (e.g., septation, motility, ATP synthesis, respiration, membrane permeability to small molecules) that may act together to negate bacterial cell viability and the evolution of drug-resistance. Disruption of these bacterial properties may occur through alteration of critical protein-protein or protein-lipid membrane interfaces-a mechanism of action distinct from many membrane disrupting antimicrobials or detergents that destabilize membranes to induce bacterial cell lysis.

INTERPRETATION

The ease of molecular design, synthesis and modular nature of COEs offer many advantages over conventional antimicrobials, making synthesis simple, scalable and affordable. These COE features enable the construction of a spectrum of compounds with the potential for development as a new versatile therapy for an imminent global health crisis.

FUNDING

U.S. Army Research Office, National Institute of Allergy and Infectious Diseases, and National Heart, Lung, and Blood Institute.

Study of Cationic Surfactants Raw Materials for COVID-19 Disinfecting Formulations by Potentiometric Surfactant Sensor

The behavior of a new 1,3-dioctadecyl-1H-imidazol-3-ium tetraphenylborate (DODI-TPB) surfactant sensor was studied in single and complex mixtures of technical grade QACs-benzalkonium chloride (BAC), N,N-didecyl-N,N-dimethylammonium chloride (DDAC), and N,N-dioctyl-N,N-dimethylammonium chloride (DOAC) usually used in COVID-19 disinfecting agents formulations. The results obtained with the new DODI-TPB sensor were in good agreement with data measured by a 1,3-dihexadecyl-1H-benzo[d]imidazol-3-ium-tetraphenylborate (DMI-TPB) surfactant sensor, as well as two-phase titration used as a reference method. The quantitative titrations of a two-component mixture of the cationic homologs (a) DDAC and DOAC; and (b) BAC and DOAC showed that the new DODI-TPB surfactant sensor can clearly distinguish two separate mixture components in a single potentiometric titration curve with two characteristic inflexion points. The consumption of SDS (used as a titrant) in the end-point 1 (EP 1) corresponded to the content of DDAC (or BAC), whereas the consumption in the end-point 2 (EP 2) corresponded to the total content of both cationic surfactants in the mixture. DOAC content in both mixtures can be calculated from the difference of the titrant used to achieve EP1 and EP2. The addition of nonionic surfactants resulted in the signal change decrease from 333.2 mV (1:0; no nonionic surfactant added) to 243.0 mV (1:10, w/w). The sensor was successfully tested in ten two-component COVID-19 disinfecting formulations.

Synthesis and characterization ofα-Fe2O3nanoparticles showing potential applications for sensing quaternary ammonium vapor at room temperature

P-type and n-type metal oxide semiconductors are widely used in the manufacture of gas sensing materials, due to their excellent electronic, electrical and electrocatalytic properties. Hematite (α-Fe₂O₃) compound has been reported as a promising material for sensing broad types of gases, due to its affordability, good stability and semiconducting properties. In the present work, the efficient and easy-to-implement sol-gel method has been used to synthesizeα-Fe₂O₃nanoparticles (NPs). The TGA-DSC characterizations of the precursor gel provided information about the phase transformation temperature and the mass percentage of the hematite NPs. X-ray diffraction, transmission electron microscopy and x-ray photoelectron spectroscopy data analyses indicated the formation of two iron oxide phases (hematite and magnetite) when the NPs are subjected to thermal treatment at 400 °C. Meanwhile, only the hematite phase was determined for thermal annealing above 500 °C up to 800 °C. Besides, the crystallite size shows an increasing trend with the thermal annealing and no defined morphology. A clear reduction of surface defects, associated with oxygen vacancies was also evidenced when the annealing temperature was increased, resulting in changes on the electrical properties of hematite NPs. Resistive gas-sensing tests were carried out using hematite NPs + glycerin paste, to detect quaternary ammonium compounds. Room-temperature high sensitivity values (S_r ∼ 4) have been obtained during the detection of ∼1 mM quaternary ammonium compounds vapor. The dependence of the sensitivity on the particle size, the mass ratio of NPs with respect to the organic ligand, changes in the dielectric properties, and the electrical conduction mechanism of gas sensing was discussed.

Multi-route exposure sampling of quaternary ammonium compounds and ethanol surface disinfectants in a K-8 school

The frequency of surface disinfectant use has increased over the last several years in public settings such as schools, especially during the COVID-19 pandemic. Although these products are important for infection control and prevention, their increased use may intensify the exposure to both persons applying the disinfection product as well as bystanders. Safety assessments have demonstrated that these products, when used as intended, are considered safe for use and effective; however, point-of-contact effects (such as respiratory or dermal irritation) may still occur. Additionally, relative exposures may vary significantly due to the wide variation in disinfectant formulation and application methods. Quantitative estimations of exposures to two commonly used active ingredients, quaternary ammonium compounds (QACs) and ethanol, are not well characterized during product use and application scenarios. To assess the potential for health risks attributable to increased use in classroom settings, as well as to quantitatively evaluate the potential exposure to both ethanol and QACs, student and adult bystander surface and air measurements were collected in a K-8 school setting in Ohio, United States, over a three-day period. Direct-reading instruments were utilized to collect real-time air samples that characterized mass fraction concentrations following the use of the QAC- and ethanol-based disinfectants. Furthermore, surface and air sampling of microbial species were conducted to establish the overall bioburden and effectiveness of each disinfectant to inform the comparative risk and health effect impacts from the tested products use scenario. Both tested products were approximately equally effective at reducing bioburdens on desk surfaces. In some classrooms, concentrations of QAC congeners were significantly increased on desk surfaces following the application of the disinfectant spray; however, the magnitude of the change in concentration was small. Ethanol was not measured on surfaces due to its volatility. Airborne concentrations increased immediately following spray of each disinfectant product but rapidly returned to baseline. Each of the QAC congeners listed in the product safety data sheets were detected and measurable on desk surfaces; however, air concentrations were generally below the limit of detection. The 15-min time-weighted averages (TWAs) of both QACs and ethanol in the air were below respective health effects benchmarks, and therefore, the negative impact on health outcomes is considered to be minimal from short-term, repeated use of ethanol- or QAC-based spray products in a school setting when the products are used as directed.