TESET polyelectrolyte completely kills drug-resistant microorganisms – News Home

米。 1. 耐甲氧西林金黄色葡萄球菌存活时间的依赖性

US researchers have discovered that TESET, a sulfo-containing polymer used in the chemical industry, has unique antibacterial properties. By significantly lowering the pH of the surrounding environment, he was able to kill pathogenic microorganisms, including antibiotic-resistant strains, in a very short period of time.

Pathogenic drug resistance is a growing threat to public health around the world (see, for example, Maya Petrova and Alexei Rzheshevsky) Bacterial Resistance: The Dangers That Are Near and R. Laxminarayan, D. Heymann, 2012. Drug resistance challenges in developing countries). Over the years, antibiotic-based therapies have allowed some microbes to survive exposure to chemicals designed to fight them through random mutations, and their offspring are eventually able to develop mechanisms to protect them from antibiotics.

Examples of antibiotic-resistant pathogens or so-called “superbugs” are Methicillin-resistant Staphylococcus aureus (Staphylococcus aureusmethicillin-resistant Staphylococcus aureus), Vancomycinresistant enterococci (Enterococcus faecalis, Virtual Reality) and carbapenemsResistant Acinetobacter (Acinetobacter baumannii, Inland Revenue Department) (见 A. N. Neely, M. P. Maley Survival of enterococci and staphylococci on hospital fabrics and plastics). Medical diagnostic errors (because they treat the wrong things), poor disease prevention, and overuse of antibiotics have exacerbated the problem of the spread of drug-resistant microbes. One symptom of the growing health crisis associated with antibiotic resistance is the increase in nosocomial infections, which pose a serious threat to the elderly and the immunocompromised.You can read more about the mechanisms by which resistance develops and related issues in the news Synthetic superantibiotic, no resistance (“Elements”, 6 June 2017).

Every year, infections caused by drug-resistant microorganisms kill tens of thousands of people in developed countries. Medical statistics have led us to disappointing predictions that by 2050 the death rate from infections caused by “superbugs” could exceed cancer deaths (J. O’Neill, 2016. Global response to drug-resistant infections: final report and recommendations)。

The problem of infections caused by drug-resistant microbes is especially acute in hospitals, and the odd thing is: many patients have weak immune systems in which microbes live and multiply, and the high “concentration” of various treatments creates increased evolutionary pressure, literally forcing Bacteria increase their resistance.in the so-called Hospital Infection Many are related to the “superbugs” listed above. They are infected differently: some are spread by airborne droplets, some by direct contact (wounds and mucous membranes). Therefore, it is important to disinfect the premises of healthcare facilities as efficiently as possible, including the disinfection of various surfaces. Currently, several methods are being used (Figure 2).

米。 2. 表面杀菌机制

The simplest method of disinfection is to regularly treat surfaces with UV radiation or disinfecting chemicals (chlorine, hydrogen peroxide, surfactants), but such treatments can damage surfaces and even pose additional risks to human health.

The next most common method is to immobilize on the surface of nanoparticles of metals (silver or gold) or metal oxides (ZnO or TiO2)2). Nanoparticles act as bactericides. They destroy pathogens by disrupting the cell membrane of bacteria or fungi, making it impossible for microorganisms to develop resistance to them (AP Richter et al., 2015. Environmentally friendly antimicrobial nanoparticles based on silver-infused lignin cores). However, this approach requires caution – nanoparticles can “leak” into the environment and either become an element of the food chain or directly into the human body, but for now, the prospect of uncontrolled long-term exposure of organisms to nano-objects raised many concerns.

Photodynamic surface activation can be said to be an effective and reliable method for removing pathogenic microorganisms. The essence of this method is to introduce photosensitive molecules into the polymer surface, which, under the irradiation of visible light, help the oxygen molecules in the air to be converted into active singlet oxygen (one2). Oxygen in this form can strongly oxidize any organic matter (including those that form cell membranes), that is, it is a potent bactericide of general action, against which resistance is unlikely (E. Feese et al. ., 2011. Photosterilization of porphyrin-cellulose nanocrystals: synthesis, characterization and antibacterial properties), however, the production of surfaces capable of generating singlet oxygen remains expensive. Another expensive way to remove pathogens from surfaces is to make surfaces from polymers that are themselves harmful to bacteria or fungi (AE Ozcam et al., 2012. Generation of functional PET microfibers by surface-initiated polymerization)。

One of the promising directions for creating antimicrobial surfaces is the use of polyelectrolytes – polymer molecules that can dissociate in aqueous media into many small and macromolecular ions on which positive or negative charges reside. This charge can interact with charged regions of pathogenic microbial cell membranes, triggering membrane disruption (LB Rawlinson et al., 2010. Antibacterial effect of poly(2-(dimethylaminoethyl)methacrylate) against selected gram-positive and gram-negative bacteria). However, until now, only those polymer electrolytes were immobilized on surfaces, and they swelled in the presence of water to form soft hydrogels—colloidal structures with a consistency and strength similar to jelly or jelly. Since pathogenic microorganisms live in water, the strength of this antibacterial surface is greatly insufficient, and it is quickly destroyed, which is extremely inconvenient for practical use. (P. Li et al. 2011. Polycationic antibacterial and biocompatible hydrogels with microbial membrane adsorption capacity)。

In a new paper, researchers at the University of North Carolina led by Richard Spontak (Richard Spontak) and Reza Girardi (Reza Girardi), the polyelectrolyte was found to have antibacterial properties and, unlike many other polyelectrolytes, did not form brittle hydrogels. This polymer turned out to be a commercially available polyurethane elastomer.[трет-бутилстирол-b-(этилен-альт-пропилен)-b-(стиролсульфонат)-b-( этилен-альт-пропилен)-b-трет-бутилстирол]sold under the trade name TESET for water treatment and breathable fabrics (GM Geise et al., 2010. Characterization of sulfonated pentablock copolymers for desalination applications). The bactericidal effect of two grades of copolymers in which the sulfo group (-SO3H) Grafting to 26% and 52% of macromolecular chain units (TESET26 and TESET52, respectively).

In water, the strongly acidic sulfo groups present in the polymer dissociate, resulting in a decrease in pH in the immediate environment of the polymer. The effect of pH on bacteria has been well studied. Based on their preference for the acidity of their growth and development environment, microorganisms are divided into acidophiles (their normal pH ranges from 1.0-5.5), neutrophils (5.5-8.0), and alkalophiles (living in alkaline environments) . environment with a pH value greater than 8.0). While different microorganisms can survive in environments of varying acidity (including those that are not characteristic of their normal development), rapid changes in pH levels can cause mechanical stress on the bacterial cell outer membrane, which is sufficient to collapse the membrane and cause the bacteria to die.

Researchers have shown (Figure 3) that TESET polymers have antimicrobial activity: both grades destroy 99.9999% and Gram negativeand Gram positive Microorganisms that pose the greatest risk in developing multi-resistance to antibiotics and developing nosocomial infections (Enterococcus faecalis, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter sp. ).There was little difference in the antimicrobial activity of the polymers, with the main focus on details – TESET52 was more effective at inactivating MRSA, while TESET26 was better against strains Staphylococcus aureusSensitive to the effects of methicillin.

米。 3. 革兰氏阳性菌和革兰氏阴性菌的存活率

The results of studying the bioactivity of TESET polymers suggest that there may be a relatively simple and inexpensive way to fight “superbugs” — antibacterial materials whose action is activated by ordinary water. However, toxicological studies of these polymers have shown that they are also dangerous to mammalian cells, that is, that they themselves are dangerous to TESET26 and TESET52. May not be suitable for the manufacture of hospital antimicrobial surfaces. Still, scientists have not lost confidence that the development of antibacterial polymers (analogs of TESET sulfonated elastomers) that are harmless to humans is in the near future.

resource: Bharadwaja S. T. Peddinti、Frank Scholle、Mariana G. Vargas、Steven D. Smith、Reza A. Ghiladi、Richard J. Spontak Inherently self-sterilizing charged multi-block polymer that kills resistant microorganisms in minutes // material vision. 2019. DOI:10.1039/c9mh00726a。

Arkady Kuramshin

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