The development of new preparations for managing skin lesions is a task requiring a complex research approach. Thus, one promising direction consists in the creation of new bases for wound-healing drugs for external application. Chemical compounds that can be used as such bases include polymeric hydrogels, representing spatially cross-linked macromolecules that swell in a solvent. This property provides an opportunity to load hydrogels with drugs of both synthetic and herbal origin. A search for a gel-forming polymer acting not only as a drug carrier, but also as a healing agent presents a relevant research task. In a previous work, the authors obtained polyhexamethylene guanidine hydrochloride hydrogels by crosslinking terminal amino groups with formaldehyde. The conducted studies of the wound-healing capacity of the obtained hydrogels and compositions on their basis confirmed their comparability with such widely-used agents, as levomecol, bepanthene, etc. In addition, the obtained compositions were found to exhibit their own activity. Therefore, hydrogels based on polyhexamethylene guanidine hydrochloride can be used as a promising platform for drug design. In this work, the destruction products released during hydrolysis of the hydrogel under study were investigated. IR and UV spectroscopy methods were applied to evaluate the concentration of hydrogel destruction products over time. A mechanism of hydrogel destruction yielding the initial polyhexamethylene guanidine hydrochloride and formaldehyde in a gem-diol form is proposed.

Since 2020, surface disinfection has become particularly relevant thus requiring improved approaches to its implementation. Conventional disinfectants comprising concentrated solutions or soluble tablets fail to fully comply with the need for antimicrobial protection of surfaces, calling for their repetitive application. This leads to considerable expenses, with the price of disinfectants rising by 30–50% over the past two years. In this article, agents characterised by prolonged action due to film-forming antimicrobial components having good adhesion to various surfaces are developed in order to reduce the cost of the disinfection procedure and increase its efficiency. In addition, such systems can be used as additives to water paint coatings for minor maintenance of medical and preventive institutions. These materials can significantly reduce the growth rate of the harmful bacteria population, as well as provide long-term protection against it. In order to implement this approach, the polymer-polymer composition based on polyvinyl alcohol and polyhexamethylene guanidine hydrochloride was developed. It should be noted that guanidine-containing polymers are characterised by high antimicrobial activity and low human toxicity, being also widely used as active agents in disinfectants. An excellent film-forming polymer exhibiting good adhesive properties, polyvinyl alcohol is non-toxic and chemically inert. Thus, the use of such additives can significantly reduce the extension of harmful bacteria, especially in crowded public areas.

The possibility of obtaining a polymer gel based on polyhexamethylene guanidine hydrochloride and polyvinyl alcohol under conditions of acid catalysis is considered. It was shown that the use of formaldehyde as a crosslinking agent leads to the formation of methylene bridges between the hydroxyl groups of polyvinyl alcohol and the amino groups of polyhexamethylene guanidine hydrochloride. The study of samples obtained by IR spectroscopy revealed the presence of corresponding signals of functional groups at 2780 cm-1 (isolated methylene group between nitrogen and oxygen atoms) and 1580 cm-1 (characteristic band of the guanidine group).

The resistance of bacteria to the disinfectants used is one of the pressing health problems that need to be addressed in order to prevent the formation and spread of resistant strains. This leads to a sharp decrease in the effectiveness of anti-epidemic measures and contributes to maintaining a high level of morbidity. In the context of the growing incidence of HAIs, their polyetiology, the large adaptive potential of opportunistic microorganisms, and the growing resistance to antimicrobial drugs, it is necessary to search for new or modify the corresponding substances of plant or synthetic origin that have antimicrobial action and are used as antimicrobial agents. One of the representatives of this class of compounds are polyguanidines, characterized by high antimicrobial activity and low toxicity. Due to the high reactivity of the guanidine group, as well as the ease of synthesis and the relative availability of raw materials, N-phenyl- and N-octyl-substituted derivatives of polyhexamethylene guanidine hydrochloride were obtained by melt polycondensation, their molecular weight characteristics were determined, and the structure was investigated by IR spectroscopy. An earlier study of the acute toxicity of polyhexamethylene guanidine hydrochloride derivatives after a single oral intake of drugs into the body of laboratory animals (white mice) made it possible to establish the following LD50 values: polyhexamethylene guanidine hydrochloride - 850.0 ± 112.02 mg / kg; N-phenyl-substituted polyhexamethylene guanidine hydrochloride - 1399.9 ± 120.51 mg / kg; N-octyl-substituted polyhexamethylene guanidine hydrochloride - 1150.0 ± 137.40 mg / kg. The obtained values, according to the tabulation of hazard classes, allow the synthesized derivatives to be classified into the fourth hazard class and open up the possibility of using disinfectants as active components. The evaluation of the antibacterial properties of the samples was carried out by the method of serial dilutions in agar on hospital strains of bacteria and fungi isolated from the biomaterial of patients of the Republican Clinical Hospital named after N.A. Semashko, according to the clinical guidelines "Laboratory diagnosis of community-acquired pneumonia" 2014; "Bacteriological analysis of urine" 2014; "Determination of the susceptibility of microorganisms to antimicrobial drugs" 2015 It was found that N-substituted derivatives exhibit a greater antimicrobial effect in comparison with an unsubstituted polymer. The most sensitive to all the drugs presented are the yeast-like fungi Candida albicans (No. 2495) (complete suppression), as well as methicillin-resistant St. aureus (no. 2544), and the substituted samples almost completely suppress its growth. The most resistant strains are P. aeruginosa (No. 2281), A. Baumannii (No. 2806) and K. Pneumoniae (No. 3023), the percentage of reduction of these bacteria under the action of substituted samples does not exceed 41%, which is explained by their multi-resistance.

Diagnosis of complex injuries, such as splinter fractures and wounds, skull injuries accompanied by internal injuries that are inaccessible to visual control, presents the greatest difficulties during X-ray examination. Therefore, it is relevant to develop a drug that can help localize the site of a pathological lesion with high accuracy, relying only on the results of an X-ray study, which is possible when a reference point (substance) is applied to the patient’s skin. A radiopaque contrast compound based on an iodinated polymeric matrix with iodine as the contrasting component and polyguanidine as the carrier has been proposed to be used as a reference point substance. The choice of this class of polymers stemmed from the fact that a positive charge is localized to a greater extent on the carbon atom of the guanidine group, which allows loading iodine anions into it. Protonation of pure guanidine with hydroiodic acid has helped obtain guanidine hydroiodide. This finding was confirmed by IR spectroscopy methods (a decrease in the intensity of bands in the region of 1,380, 880 cm−1 in comparison with guanidine, as well as broadening of the band of stretching vibrations of amino groups characteristic of guanidine salts) and X-ray phase analysis. Polyhexamethylene guanidine hydroiodide was synthesized based on hexamethylenediamine and iodine-containing guanidine salt using melt polycondensation. The results show that the aqueous solutions of samples under study absorb X-radiation and are the X-ray-positive substances (exposure radiation dosage E = 0.04 mSV).