This review focuses on the enzymatic breakdown of chitin, taking into account the latest scientific reports on the activity of lytic polysaccharide monooxygenase (LPMO). Chitin is a natural, abundant polysaccharide of great practical importance in the environment. However, the insolubility in water and the tightly packed crystalline structure of chitin pose a serious obstacle to enzymatic degradation. This substrate can be converted into soluble sugars by the action of glycosidic hydrolases (GH), also known as chitinases. LPMO could prove to be helpful in enzymatic processes that increase the rate of chitin depolymerisation by improving the availability of substrates for chitinases. The unique action of LPMO is based on the ability to catalyse the oxidative cleavage of glycosidic chains present in complex, resistant crystal networks of chitin, and this cleavage facilitates the subsequent action of glycolytic hydrolases.

An increase in the number and volume of surgical interventions leads to an increase in the frequency of postoperative adhesions. The development of the adhesion process in the abdominal cavity causes pain, a decrease in the quality of life of patients, a violation of the reproductive function of women as well as acute adhesion intestinal obstruction. Recently, polymer biomaterials, including those based on chitosan, have been widely used for the prevention of adhesions. Due to their biocompatibility and biodegradation ability, they do not require repeated operations to extract the material. It is believed that these materials act as barriers, physically separating the damaged surfaces. The molecular mechanism of their action is still poorly understood. In this review, the main mechanisms of adhesion formation, as well as ways to prevent them with the help of materials based on chitosan and its derivatives, are discussed.

Chitin is a naturally occurring polymer. Together with its derivatives such as chitosan, it has a wide spectrum of application possibilities, and many properties not yet exploited. Chitosan possesses many features desirable in an ideal antimicrobial polymer. It shows activity against multidrug-resistant bacterial and fungal strains that pose a challenge to modern medicine. Chitosan also shows activity against certain viruses, such as SARS-CoV-2. It might be used as a drug or a vaccine delivery system, is biodegradable, bioavailable and considered safe for medical use. It is important to continue exploring the potential of chitosan, as well as to investigate its sources. Indeed, many sources of this polymer are still not or have been poorly described. In this paper, we compile the current state of knowledge on the antimicrobial properties of chitosan, list alternative sources of chitin to highlight the potential of these two polymers and encourage further research.

Epidemics of infectious diseases have always been a threat to humanity and have contributed to increased mortality in the affected areas. This also applies to a new species of coronavirus identified in 2019, SARS-CoV-2, which is responsible for the COVID-19 pandemic. Despite preventive measures implemented all over the world to minimise the spread of the pathogen as well as the development of vaccines, which have been approved for emergency use, the situation is still worrying. Moreover, the problem is exacerbated by the lack of targeted treatments for COVID-19 patients. One possible solution is the using preparations based on natural raw materials, including chitosan. This biopolymer is of great interest due to a number of unique biological properties, among which its antiviral effect is a key feature. Hence, this paper presents the application possibilities of chitosan-based solutions in the prevention and treatment of viral diseases, with particular emphasis on COVID-19.

The aim of this study was to develop a technical process and composition of mucoadhesive hydrogels containing benzocaine, based on different concentration ratios of the natural polymers chitosan and xanthan gum. For this purpose, lyophilisates of polymeric complexes with the quantitative ratios of 0.5:1, 1:1 and 1:0.5 chitosan to xanthan gum were prepared and subsequently used to prepare hydrogels of various concentrations. The physicochemical properties and pharmaceutical availability of benzocaine were evaluated and diffractograms and Fourier-transform infrared spectra of individual polymers and their polyelectrolyte complexes were compared. The 1:1 formulation exhibited the highest water absorption capacity and the gels showed the highest viscosity and the shortest blurring times. More chitosan increased carrier texture parameters, including hardness, cohesiveness and consistency, whereas more xanthan gum led to the longest gel blurring times and improved carrier stability. The concentration ratio of chitosan to xanthan gum in lyophilisates determined the viscosity, texture, spreadability and blurring time of the gels. Increases in lyophilisate percentage in the gels also affected the physicochemical properties of the carrier. In addition, the proportions of polymers in the mixture did not influence the availability of the drug from the prepared gel; this factor appears to depend more on the lyophilisate content in the carrier. Variations in the ratio of chitosan to xanthan gum in the polymer complex as well as lyophilisate percentage in the gel may impact the properties of the hydrogel and its efficacy as a carrier for therapeutic substances administered to the oral cavity mucosa.

The aim of this research was to develop a bioadhesive film based on benzydamine hydrochloride incorporated into natural bioadhesive polymers with different quantities of chitosan and guar gum but utilising a plasticiser. The obtained gels were deaerated by sonification, formed and evaporated by hot air drying; then, the properties were evaluated. Guar gum had a great influence on mechanical properties of the films – dynamic viscosity, texture, elasticity, stretching robustness, swelling and blur time. The formulations were used to obtain mucoadhesive films containing 0.3% benzydamine hydrochloride; they were tested for the release of the model drug. The amount of chitosan added to the formulation reduced the quantity of released substance and slowed down the release. Fourier-transform infrared spectroscopy did not reveal the creation of new chemical structures. In conclusion, the ratio of chitosan to guar gum in the medium impacts the mechanical properties and release parameters of the drug. These findings should enable researchers to match the parameter values to receive the most beneficial therapeutic outcome.

Treatment of chitosan with ionising radiation is one of the methods by which it is modified for various applications. However, in the case of chitosan irradiated in the solid state, the radicals formed during irradiation can be stabilised in its crystalline phase and subsequently cause post-irradiation changes. It has been observed that further degradation of the polymer occurs during storage of the irradiated polymer, resulting in an increase in oxidation products and a decrease in deacetylation degree. This effect results from the transformation of radicals leading to the formation of stable nitroxyl radicals, a process observed years after irradiation.

The aim of this study was to evaluate the influence of the surface microstructure of chitosan films on the contact angle. Films without plasticising additives made of chitosan or regenerated chitosan were selected for the tests. A sessile drop method based on the European Pharmacopoeia was used to determine the contact angle. Due to the method of film production, the contact angle measurements were made on both the top and bottom surfaces of the film. For chitosan or regenerated chitosan films, the method of preparation slightly affected the difference in wettability between the top and bottom of the films, as confirmed by scanning electron microscopy. On the other hand, the wettability of the top and bottom of cellulose films varied greatly depending on the side of the film. Both chitosan and cellulose films had a homogeneous structure. There were differences in the microstructure between the top and the bottom of the sample in the cellulose film, a factor that affected the contact angle and thus the wettability of the surface.

Zinc pollution in wastewater is a global problem because it is highly toxic. Zinc is commonly used in industries that transfer the water containing zinc directly into water sources, leading to pollution. Exposure to a high level of zinc causes major health problems. This study evaluated the adsorption of zinc ions from aqueous system using modified biopolymers of chitosan by crosslinking with sulphates using the batch adsorption method; the concentration was determined using atomic absorption spectrophotometry. The sulphate cross-linked chitosan (SCC) was characterised by several method. The effects of various experimental parameters such as pH, contact time, concentration, adsorbent dosage and temperature were investigated. Under the optimised conditions, the percentage efficiency for the removal of zinc(II) was up to 85%. Freundlich and Langmuir isotherms were used to analyse the equilibrium adsorption data along with kinetic studies. Various thermodynamic parameters have also been reported.

Chitosan are biopolymers that are actively used for the production of local haemostatic agents. The physicochemical characteristics that determine its biological properties include the molecular weight and the deacetylation degree. However, there is no linear relationship between these parameters and haemostatic activity. The most reliable method of confirming the effectiveness is still in vivo experiments. The ability to initiate haemostasis depends on the conformational transition of chitosan macromolecules. The highest efficiency in vitro was for samples in which the transition of a significant part of the molecules from the ‘rigid rod’ state to the ‘globule’ occurred at physiological pH. It is proposed to expand the list of indicators of chitosan that can be controlled to evaluate the quality of raw materials, related to haemostatic activity, to include the definition of the conformational transition at physiological pH.

New composite materials were obtained based on chitosan iodide and organic dyes – methylene blue and fuchsine in fucorcin (Castellani liquid) – by using a simple synthetic procedure. The materials were characterised by scanning electron microscopy, X-ray diffraction, temperature-programmed desorption mass spectrometry, infrared spectroscopy and visible and ultraviolet light spectroscopy. The dyes in the composites were distributed uniformly and did not form separate phases. These composites could form structured porous sponges and films and therefore be used in various fields of application. The materials displayed antibacterial activity against antibiotic resistant gram-positive and gram-negative bacteria.

Effective antibacterial coatings are in demand in medicine, especially for urological medical devices such as catheters and stents. We propose the production method of an antibacterial hydrogel coating on polydimethylsiloxane (PDMS, silicone), a popular surface for medical materials. The coating process consists of the following steps: PDMS surface activation (introduction of hydroxyl groups), silanisation (introduction of amine groups) and application of chitosan/alginate hydrogel with the addition of lysozyme as an antibacterial agent using the layer-by-layer method. We investigated the effect of polyion concentration on the coating mass, swelling ratio and stability. We analysed the adsorption of Micrococcus luteus, Escherichia coli and Proteus rettgeri on a PDMS surface using confocal laser scanning microscopy. The chitosan/alginate hydrogel coating with immobilised lysozyme protected the PDMS surface against adhesion for all three tested bacterial strains.

Food edible coatings are an important milestone in food production and one of the innovations in food packaging development. This article presents materials on the development of the formulation and technology for the manufacture of a novel composite coating based on sodium alginate, chitosan and protein hydrolysate obtained by the electrochemical method of double extraction from cod processing waste to obtain edible coatings for semi-finished fish products. Furthermore, the physicochemical, physical, mechanical and microbiological properties of this material are described.

Among the diseases of the digestive tract, gastro-oesophageal reflux is one of the most troublesome ailments. It is estimated that in highly developed countries, reflux symptoms occur in about 5%-10% of people every day. It has also been found that about 20% of people experience such symptoms once a week. The incidence of this disease increases with age, regardless of gender. The aim of the study was to investigate the physicochemical properties of gels intended for the protection of the oesophageal mucosa. Preparations containing 3.0% pectin showed the lowest pH. These gels can be used in the treatment of advanced alkaline reflux. The addition of chitosan to all tested gels increased their pH and dynamic viscosity. The texture tests showed the effect of pectin concentration on the adhesion work of the tested gels.

An important issue in the treatment of vaginitis is the amount of time the drug remains on the vaginal mucosa. If the contact time is too short, the drug cannot work effectively to ensure the correct pH in the vaginal environment. This study evaluated formulations of globules containing sodium alginate, lactic acid and chitosan with different pH and rheological properties. The experimental studies revealed that it is possible to produce a preparation with optimal pharmaceutical and application properties. The use of an appropriate ratio of lactic acid to chitosan in the complex and the appropriate concentration of sodium alginate produces a preparation with excellent properties to coat the surface of the vaginal mucosa.

A series of N,O-acylated chitosan derivatives were emulsified with different fatty acids. Hydrophobically modified chitosan derivatives were expected to exhibit self-assembly behaviour resulting in micelle formation. Several parameters of the oil-in-water emulsification process were investigated: mixing method, speed and duration, volume oil phase and addition of modifiers. Their influence on micellar Z-average diameter, size distribution and Zeta potential was analysed based on dynamic light scattering measurements. There were various relations between the hydrodynamic behaviour of chitosan derivatives, their chemical structure and the process parameters. Additionally, the obtained micelles could serve as active compound carriers because they encapsulated two model substances, namely ibuprofen and α-tocopherol.

Creating innovative methods of treatment and regeneration of damaged tissues or organs is a key challenge of the twenty-first century. The aim of this study was to determine the possibility of producing and characterising the properties of self-organising chitosan hydrogels prepared with the use of chitosan lactate/chloride and disodium hydrogen phosphate dodecahydrate as a cross-linking agent. The structure and supramolecular architecture of the biomaterials were evaluated by Fourier-transform infrared spectroscopy and polarised optical microscopy. Biological studies assessed cytotoxicity by contact with a human colon adenocarcinoma cell line. The colourimetric resazurin assay showed that the obtained chitosan hydrogels are non-cytotoxic materials. Thus, self-organising biomaterials hold great promise for application in tissue engineering.

Chitosan hydrolysate was obtained using nitric acid; the prevailing fraction had a molecular weight of 30 kDa and a deacetylation degree of 95%. The effect of chitosan hydrolysate when added to potato dextrose agar (PDA) in different concentrations (0.5, 1, 1.5, 2, 4, 6 and 8 mg/mL) was studied on the growth of the fungi Alternaria solani Sorauer, Fusarium solani (Mart.) Sacc. and Rhizoctonia solani J.G. Kühn. A. solani was the most sensitive to the addition of chitosan hydrolysate to PDA in radial growth experiments. On days 3 and 7 of incubation, the antifungal activity of the phytopathogen growth was 69%-92% and 69%-88%, respectively, in the concentration range of 0.5-2 mg/ml.

The wetting properties of chitosan (Ch) and single 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), cholesterol (Chol) and binary DPPC-Chol χ_Chol=0.25 layers deposited onto polyethylene terephthalate activated by low-temperature air plasma (PET_air) were examined. PET is widely used in tissue engineering, but its low hydrophilicity limits its integration with the surrounding tissues. Ch is a biocompatible polysaccharide, distinguished by its antimicrobial properties, widely distributed in medicine. DPPC and Chol are the major building components of cell membrane, so they can perfectly mimic membrane behaviour during contact with the Ch layer. Monolayers of lipids were deposited onto PET_air with or without the Ch layer using the Langmuir-Blodgett technique. The total surface free energy (SFE) and its components changes were calculated from theoretical approaches. Wettability strongly depended on the monolayer composition as well as the Ch layer. The Ch film decreased the contact angle and increased SFE of the PET surface with the lipid monolayers due to specific organisation of molecules within the chitosan scaffold. The most promising combination of surface modification for tissue engineering applications seems to be the PET_air/Ch/DPPC-Chol system.