In this review, the research devoted to synthesising chitosan apatites, their biologically active properties, and their application in medical practice is analysed. The data are from articles published between 2001 and 2022 on the formation of calcium- and phosphorus-containing chitosan composites and the mechanism of their interaction.

Chitosan is a cationic polymer capable of binding acidic drugs. In addition, it has haemostatic and antimicrobial activity. Chitosan derivatives withanti-fibrinolytic properties may present increased effectiveness, especially when the added substance forms an adduct with chitosan. The aim of this work was to study the haemostatic action of the chitosan–tranexamic acid complex. Two chitosan solutions (molecularweight of 250 and 625 kDa at pH 5.7 and 6.2, and after tranexamic acid had been added to chitosan solutions) werestudied. Haemostatic evaluation was performed on white outbred mice. The time to complete cessation of bleeding from the tail was determined. Chitosan 625 kDa at pH 6.2 had the best haemostatic properties. Adding tranexamic acid to the chitosan solution reduced the bleeding time. This phenomenon was more pronounced for chitosan 625 kDa. Compared with control animals, this chitosan reduced bleeding arrest time by 30% and the chitosan–tranexamic acid adduct reduced the bleeding arrest time by 75%.

Chitin nanocrystals and microfibrils were prepared based on the strong acid hydrolysis method. The change in the molecular structure was studied by Fourier-transform infrared and Raman spectroscopy. The surface morphology of chitin materials was observed using scanning electron and optical microscopy. The separation of nano-crystals and microfibril crystalline regions from native chitin may increase the scope of its application for the creation of bioactive composites and scaffolds for tissue culture. As a result of the conducted experimental work, it was possible to loosen the amorphous areas and partially separate nano-crystals and chitin microfibrils. Stable aqueous suspensions of chitin nano-crystals and microfibrils were obtained, which can be used for further experimental work.

This paper describes the synthesis of hierarchical zeolites based on a commercial FAU zeolite modified with chitosan. Additionally, the amount of silicon source added (tetraethyl orthosilicate) and the type of structuring agent used were modified during synthesis of the materials. The synthesised materials were characterised by the following methods: X-ray diffraction, transmission electron microscopy, scanning electron microscopy, Fourier-transform infrared spectroscopy, and low-temperature nitrogen adsorption/ desorption isotherms. The obtained results confirmed the achievement of additional porosity in the synthesised materials. According to the adsorption experiments, the hierarchical zeolite-modified chitosan had a high adsorption capacity of 1.2 cm³ g⁻¹.

The consumption of highbush blueberries has been growing rapidly in recent years due to their taste and health-promoting qualities. Various solutions have been sought to obtain the highest quality fruit after harvest. In the era of eco-friendly products, it is important that the methods used are natural and ecological. For this purpose, chitosan (CH) was sprayed five times on highbush blueberry bushes before harvesting. Different molecular weights of CH (5, 12, 21, 50, 125, and 500 kDa) were used in this study. The physical and biochemical characteristics of the fruit were investigated. The antioxidant activity, microbial contaminants, and mycotoxins in fruit were also analysed. Application of CH affected the quality of highbush blueberries after harvest. The molecular weight of CH had a significant effect on the studied traits. The application of high-molecular-weight CH improved physical characteristics such as the average weight of 100 blueberries, firmness, and puncture. Furthermore, the blueberries had a more intense blue colour; were characterised by a higher content of l-ascorbic acid and polyphenols, especially anthocyanins; and did not contain mycotoxins. Spraying with CH can be recommended in the organic cultivation of highbush blueberries to obtain robust fruit with health-promoting qualities.

Adsorption tests in the air-lift reactor were carried out for six dyes –four anionic (RR11, RB5, RB8, and RR18) and two cationic (BV10 and BG 4) – as well as three adsorbents – chitosan flakes, chitosan in the form of beads, and modified sawdust immobilised in chitosan (adsorbent 3). The dye concentration in the inflow to the reactor in all the conducted test series was 10 mg/dm³; the amount of adsorbent was also constant at 10 g dry matter (d.m./dm³, and the flow rate was 0.1 V/h. For all tested dyes, the obtained maximum adsorption capacity was high and ranged from 3802 to 2203 mg/g d.m. for chitosan flakes, from 3312 to 2076 mg/g d.m. for chitosan beads, and from 2734 to 2148 mg/g d.m. for modified sawdust immobilised in chitosan. The immobilisation of sawdust on chitosan resulted in effective adsorption of both anionic and cationic dyes.

In this study, membranes from chitosan with different molecular weights (175-230 kDa) and degree of deacetylation (92%-98%) were prepared and dehydration of a ethanol-water azeotropic mixture by pervaporation on membranes in the swollen and dry initial state was investigated. The influence of chitosan characteristics and the effect of the initial membrane state on separation properties are discussed. The structure of the obtained membranes changed during the drying process and affected the membrane transport parameters and time to membrane stabilisation. The impact of chitosan characteristics on the transport parameters depended on the initial membrane state. The chitosan molecular weight influenced ethanol transport, whereas the chitosan degree of deacetylation affected water transport. In addition, chitosan with the lowest molecular weight improved the separation properties of the membranes.

The aim of this paper was to formulate the composition of a bioadhesive film obtained based on acyclovir incorporated into natural bioadhesive polymers (chitosan and guar gum) in different quantitative ratios. To this end, the author developed a technology for preparing films containing various quantitative ratios of chitosan to guar gum: 1:0.25; 1:0.50; 1:0.75; 1:1; and 1.2:0.50. The formulations were used to prepare mucoadhesive films containing 2% acyclovir. The dressings were tested with respect to their physicochemical properties and subjected to dissolution testing. A comparative analysis of Fourier-transform infrared (FT-IR) spectra of pure polymers, acyclovir, and films containing polymers in different quantitative ratios was conducted. The quantitative ratio of chitosan to guar gum significantly impacted the mechanical properties of films: texture, elasticity, tensile strength, swelling, and blur time of the testes carriers. The 1:1 formulation showed the highest mechanical strength and flexibility. The dressing containing 1.2% chitosan and 0.5% guar gum had the longest blur time. An increase in the chitosan content in the formulation significantly affected the drug dissolution parameters, which makes it possible to achieve the desired effect of extended-release time. The FT-IR spectra excluded the formation of drug-polymer interactions. Changes in the quantitative ratios of chitosan and guar game in the carrier’s composition may impact the mechanical properties of the drug formulation and changes in the parameters of active substance release.

This work investigated the adsorption efficiency of Basic Violet 10 (BV10) and Basic Green 4 (BG4) dyes on ionically and covalently crosslinked chitosan hydrogel beads. The tested ionic crosslinkers were sodium citrate, sodium tripolyphosphate, and sulphosuccinic acid, while the covalent crosslinkers were glutaraldehyde, epichlorohydrin, and trimethylolpropane triglycidyl ether. The scope of the work included investigation of the effect of pH on the adsorption efficiency of dyes and the maximum adsorption capacity of crosslinked chitosan adsorbents. The maximum adsorption capacity of the non-crosslinked chitosan adsorbent was 2.94 mg/g and 44.32 mg/g for BV10 and BG4, respectively. Ionic crosslinking, regardless of the type of crosslinking agent, reduced the adsorption ability of hydrogel chitosan adsorbents in relation to cationic dyes (Q_max = 1.84-2.49 mg/g for BV10; 37.21-38.90 mg/g for BG4). Covalent crosslinking of chitosan slightly increased its adsorption capacity only for BV10 (Q_max = 3.59-3.81 mg/g for BV10; 39.15-40.62 mg/g for BG4).

Chitosan electrospun nanofibres were synthesised in two different trifluoroacetic acid (TFA)/dichloromethane (DCM) solvent ratios and then neutralised in aqueous and ethanol sodium-based solutions (NaOH and Na₂CO₃) to produce insoluble materials with enhanced biological properties for regenerative and tissue engineering applications. Structural, electronic, and optical properties and the swelling capacity of the prepared nanofibre membrane were studied by scanning electron microscopy, Fourier-transform infrared spectroscopy, and photoluminescence. Cell viability (with the U2OS cell line) and antibacterial properties (against Staphylococcus aureus and Escherichia coli) assays were used to assess the biomedical potential of the neutralised chitosan nanofibrous membranes. A 7:3 TFA/DCM ratio allows for an elaborate nanofibrous membrane with a more uniform fibre size distribution. Neutralisation in aqueous NaOH only maintains a partial fibrous structure. At the same time, neutralisation in NaOH ethanol-water maintains the structure during 1 month of degradation in phosphate-buffered saline and distilled water. All membranes demonstrate high biocompatibility, but neutralisation in ethanol solutions affects cell proliferation on materials made with 9:1 TFA/DCM. The prepared nanofibrous mats could constrain the growth of both gram-positive and gram-negative microorganisms, but 7:3 TFA/DCM membranes inhibited bacterial growth more efficiently. Based on structural, degradation, and biological properties, 7:3 TFA/DCM chitosan nanofibrous membranes neutralised by 70% ethanol/30% aqueous NaOH exhibit potential for biomedical and tissue engineering applications.

The culture medium is often optimised to improve growth and morphogenesis in vitro. The efficiency of chitosan (CH) and meta-topolin (mT) on in vitro growth of blueberries (Vaccinium corymbosum) cv Liberty was investigated. The explants were grown on Woody Plant Medium (WPM) supplemented with mT at a concentration of 0.2, 0.4, and 0.6 mg l⁻¹ and WPM with chitosan with a molecular weight 3.33 kDa at 10, 20, and 40 ppm. WPM with the addition of 0.1 mg l⁻¹ zeatin was used as a control. Among the tested combinations, the maximum mean shoot length (23.81 cm), the number of new shoots (1.34), fresh mass (42.29 g), and dry mass (14.24 g) were recorded on the control medium. The addition of lower concentrations of chitosan (10 and 20 ppm) to the WPM medium decreased shoot length (23%-24.5% of control), fresh mass (30%-40% of control), and dry mass (20%-29% of control). However, blueberries treated with 40 ppm chitosan had similar shoot lengths, but darker (112% of control) and greener (139% of control) leaves compared with the control. In contrast, mT had a negative effect on the studied traits of Liberty blueberries, regardless of the concentration.

The development and improvement of chitin applications have drawn special attention from the global scientific community due to their extraordinary features and abundance. In this study, β-chitin nanofibres were obtained using the ultrasonication treatment method. Then, hydroxyapatite/ nanochitin (HAp/NCh) composites were prepared at different maturation times. In this case, mixtures of various amounts of β-chitin nanofibres (1%, 2%, and 5%) were added during the HAp precipitation approach. The prepared HAp/NCh materials were characterised with Fourier-transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, and energy-dispersive X-ray spectroscopy. The surface of prepared specimens was observed using scanning electron microscopy. The presence of nanofibres was confirmed by non-invasive backscattering with dynamic light scattering particle size analysis. Moreover, the synergic effect of chitin nanofibres on the mechanical resistance of HAp-based composite was investigated. The sample with 5% of chitin nanofibres exhibited about 10 times higher compression strength than the pure HAp. All these results essentially indicate that the prepared material can be a potential candidate for bone tissue engineering applications and further development.

The incidence of reflux disease increases with age, regardless of gender. This disease is diagnosed more often in highly developed countries. In addition to acidic reflux, the discharge of alkaline intestinal contents into the oesophagus is a major problem. This study was undertaken to examine whether hydrogels prevent irritation of the oesophageal mucosa. The aim was to investigate the influence of chitosan and hydroxypropylmethylcellulose on the properties of chitosan-containing gels. Preparations containing 4.0% hydroxypropylmethylcellulose showed the lowest pH. These gels could be used to treat advanced alkaline reflux. The addition of chitosan to all tested gels increased their pH and dynamic viscosity. The texture tests showed the effect of the hydroxypropylmethylcellulose concentration on the adhesion work of the tested gels.

Gastro-oesophageal reflux disease is a serious social problem that affects every sphere of life. The quality of life of people with this disease is reduced due to the presence of troublesome symptoms, which translates into reduced work efficiency and vitality. The major problem is acidic gastro-oesophageal reflux. This study was undertaken to examine whether hydrogels prevent irritation of the oesophageal mucosa. The aim was to investigate the influence of chitosan and carboxymethylcellulose sodium salt on the protective properties of prepared gels in the treatment of acid reflux. The addition of chitosan to all tested gels increased their pH and dynamic viscosity. Preparations containing 0.3% carboxymethylcellulose sodium salt showed the highest pH. The texture tests showed the effect of carboxymethylcellulose sodium salt concentration on the adhesion work of the tested gels. These gels could be used in the treatment of advanced acid reflux.

Chitosan could be an alternative to synthetic plant protection chemicals commonly used in strawberry cultivation. The aim of this study was to determine the effect of chitosan with different molecular weights on the yield, health, and quality of Korona cultivar strawberries. The largest number of strawberries was harvested from plants sprayed with chitosan with a molecular weight of 50k kDa (611 g/plant). On the other hand, the largest (1017 g/100 fruit) and the firmest (225 G mm) strawberries were harvested from plants sprayed with chitosan125k kDa. Compared with the control, chitosan with a molecular weight >50 kDa also increased the contents of l-ascorbic acid and polyphenols and the antioxidant activity and improved fruit colour compared with the control. The plants were also more resistant to grey mould infestation. The experiment has shown that how chitosan interacts with fruit depends on its molecular weight, and chitosan with a higher molecular weight has a better effect on most traits determining fruit quality.

Current chitosan extraction methods require a highly concentrated alkaline solvent that is costly and environmentally unfriendly. This study aimed to assess the potential of using subcritical liquid deproteination to produce amorphous chitin to reduce the alkaline concentration during the deacetylation step to obtain high-quality chitosan. A combination of microwave-assisted demineralisation, subcritical liquid (SL) deproteination, and conventional deacetylation was employed for chitosan production. Distilled water and 2% and 4% sodium hydroxide (NaOH) were used at subcritical liquid treatment temperatures of 100 to 250°C. Meanwhile, deacetylation using 20%-50% NaOH was attempted on the deproteinised chitin. 1.8 M hydrochloric acid at a 1:10 solid-to-liquid solvent ratio produced chitin with acceptable quality during microwave-assisted demineralisation. Demineralised chitin subjected to SL treatment at 150°C and 4% NaOH had the best protein removal (84.6%). Chitosan with a high degree of deacetylation (80.68%) was obtained at a lower alkalinity of 30% NaOH, derived from SL-deproteinised chitin (4% NaOH at 100°C). The crystallinity of chitin after SL treatment was reduced significantly from 72.4% to 59.4%, which allows easier access for the solvent to hydrolyse the acetamide bond. This study confirms that good quality chitosan can be produced by utilising SL treatment of demineralised chitin at a significantly short time and lower deacetylation solvent concentration.

The subject of this study was the synthesis of 12 chitosan-hydroxyapatite (CH:HA) composites with different contents of carbonate ions (CO₃²⁻), in two weight ratios of CH to HA (30:70 and 50:50), and two viscosities of CH (low [L] and high [H]). The method of direct co-precipitation of the introduced reagents was used. The structure of the obtained materials was characterised by Fourier-transform infrared (FT-IR) spectroscopy, powder X-ray diffraction, and scanning electron microscopy. The FT-IR spectra revealed the bands and ranges of the characteristic bands for CH and HA. The presence of CO₃²⁻ introduced into the structure of the obtained composites was identified by infrared spectroscopy. A reduction in the size of HA unit cells was observed in the obtained CH:HA biocomposites, in materials with a higher content of incorporated CO₃²⁻. The obtained nanomaterials are similar to natural bone tissue. Future research will focus on the evaluation of the obtained materials as a drug delivery system.