New technologies and materials could help in this fight against healthcare-associated infections. As the majority of these infections are caused by antibiotic-resistant bacteria, the development of materials with intrinsic antibacterial properties is a promising field of research. We combined chitosan (CS), with antibacterial properties, with polyhedral oligomeric silsesquioxanes (POSS), a biocompatible polymer with physico-chemical, mechanical, and rheological properties, creating a hydrogel using cross-linking agent genipin. The antibacterial properties of CS and CS-POSS hydrogels were investigated against nosocomial Gram-positive and Gram-negative bacteria both in terms of membrane damage and surface charge variations, and finally, the anti-biofilm property was studied through confocal microscopy. Both materials showed a good antibacterial capacity against all analyzed strains, both in suspension, with % decreases between 36.36 and 73.58 for CS and 29.86 and 66.04 for CS-POSS, and in plates with % decreases between 55.29 and 78.32 and 17.00 and 53.99 for CS and CS-POSS, respectively. The treated strains compared to the baseline condition showed an important membrane damage, which also determined a variation of surface charges, and finally, for both hydrogels, a remarkable anti-biofilm property was highlighted. Our findings showed a possible future use of these biocompatible materials in the manufacture of medical and surgical devices with intrinsic antibacterial and anti-biofilm properties. Full article

The present study demonstrates a strategy for preparing porous composite fibrous materials with superior biocompatibility and antibacterial performance. The findings reveal that the incorporation of PEG into the spinning solutions significantly influences the fiber diameters, morphology, and porous area fraction. The addition of a hydrophilic homopolymer, PEG, into the Ch/PLA spinning solution enhances the hydrophilicity of the resulting materials. The hybrid fibrous materials, comprising Ch modified with PLA and PEG as a co-solvent, along with post-treatment to improve water stability, exhibit a slower rate of degradation (stable, moderate weight loss over 16 weeks) and reduced hydrophobicity (lower contact angle, reaching 21.95 ± 2.17°), rendering them promising for biomedical applications. The antibacterial activity of the membranes is evaluated against Staphylococcus aureus and Escherichia coli, with PEG-containing samples showing a twofold increase in bacterial reduction rate. In vitro cell culture studies demonstrated that PEG-containing materials promote uniform cell attachment, comparable to PEG-free nanofibers. The comprehensive evaluation of these novel materials, which exhibit improved physical, chemical, and biological properties, highlights their potential for biomedical applications in tissue engineering and regenerative medicine. Full article

Nanogel-forming polymers such as chitosan and alginic acid have a number of practical applications in the fields of drug delivery, food technology and agrotechnology as biocompatible, biodegradable polymers. Unlike bulk macrogel formation, which is followed by visually or easily detectable changes and physical parameters, such as viscosity or turbidity, the formation of nanogels is not followed by such changes and is therefore very difficult to track. The counterflow extrusion method (or analogues) enables gel nanoparticle formation for certain polymers, including chitosan and its derivatives. DLS or TEM, which are typically used for their characterization, only allow for the study of the already-formed nanoparticles. Alternatively, one might introduce a fluorescent dye into the gel-forming polymer, with the purpose of monitoring the effect of its microenvironment on the fluorescence spectra. But apparently, this approach does not provide a sufficiently specific signal, as the microenvironment may be affected by a big number of various factors (such as pH changes) including but not limited to gel formation per se. Here, we propose a new approach, based on the FRET effect, which we believe is much more specific and enables the elucidation of nanogel formation process in real time. Tryptophan-Pyrene is suggested as one of the donor–acceptor pairs, yielding the FRET effect when the two compounds are in close proximity to one another. We covalently attached Pyrene (the acceptor) to the chitosan (or PEG-chitosan) polymeric chain. The amount of introduced Pyrene was low enough to produce no significant effect on the properties of the resulting gel nanoparticles, but high enough to detect the FRET effect upon its interaction with Trp. When the Pyr-modified chitosan and Trp are both present in the solution, no FRET effect is observed. But as soon as the gel formation is initiated using the counterflow extrusion method, the FRET effect is easily detectable, manifested in a sharp increase in the fluorescence intensity of the pyrene acceptor and reflecting the gel formation process in real time. Apparently, the gel formation promotes the Trp-Pyr stacking interaction, which is deemed necessary for the FRET effect, and which does not occur in the solution. Further, we observed a similar FRET effect when the chitosan gel formation is a result of the covalent crosslinking of chitosan chains with genipin. Interestingly, using ovalbumin, having numerous Trp exposed on the protein surface instead of individual Trp yields a FRET effect similar to Trp. In all cases, we were able to detect the pH-, concentration- and temperature-dependent behaviors of the polymers as well as the kinetics of the gel formation for both nanogels and macrogels. These findings indicate a broad applicability of FRET-based analysis in biomedical practice, ranging from the optimization of gel formation to the encapsulation of therapeutic agents to food and biomedical technologies. Full article

Lactobionic acid (LBA) is a bioactive compound that has become increasingly popular in medicine in recent years due to its unique properties. This chemical can be formed via the enzymatic oxidation of lactose using fungal oxidoreductive enzymes. This study aimed to intensify the synthesis of LBA using immobilised enzymes (cellobiose dehydrogenase from Phanerochaete chrysosporium (PchCDH) and laccase from Cerrena unicolor (CuLAC)) on chitosan microspheres. We used three different crosslinking agents: genipin, glutaraldehyde, and polyethyleneimine to activate the chitosan. The FTIR and CellDrop techniques were used to characterise the activated microspheres. Quantitative (HPLC) and qualitative (TLC) methods were used to determine the obtained LBA. The results show that the type of activator used influences the efficiency of the binding of the enzyme to the matrix. Furthermore, the amount of LBA formed depends on the type of system used. The use of a system in which one of the enzymes is immobilised on a PEI-activated carrier (PchCDH) and the other is free (CuLAC) proved to be the most optimal, as it yielded almost 100% conversion of lactose to lactobionic acid. Summarising the data obtained the following: lactobionic acid immobilised on chitosan microspheres has great potential for medical applications. Full article

Chitosan is a natural and biodegradable polymer with promising potential for biomedical applications. This study concerns the production of chitosan-based materials for future use in the medical industry. Bioactive substances—caffeine and ethanolic propolis extract (EEP)—were incorporated into a chitosan matrix to increase the bioactivity of the obtained films and improve their mechanical properties. Acetic and citric acids were used as solvents in the production of the chitosan-based films. The obtained materials were characterized in terms of their antibacterial and antifungal activities, as well as their mechanical properties, including tensile strength and elongation at break. Moreover, the chemical structures and surface morphologies of the films were assessed. The results showed that the solution consisting of chitosan, citric acid, caffeine, and EEP exhibited an excellent antiradical effect. The activity of this solution (99.13%) was comparable to that of the standard antioxidant Trolox (92.82%). In addition, the film obtained from this solution showed good antibacterial activity, mainly against Escherichia coli and Enterococcus faecalis. The results also revealed that the films produced with citric acid exhibited higher activity levels against pathogenic bacteria than the films obtained with acetic acid. The antimicrobial effect of the chitosan-based films could be further enhanced by adding bioactive additives such as caffeine and propolis extract. The mechanical tests showed that the solvents and additives used affected the mechanical properties of the films obtained. The film produced from chitosan and acetic acid was characterized by the highest tensile strength value (46.95 MPa) while the chitosan-based film with citric acid showed the lowest value (2.28 MPa). The addition of caffeine and propolis to the film based on chitosan with acetic acid decreased its tensile strength while in the case of the chitosan-based film with citric acid, an increase in strength was observed. The obtained results suggested that chitosan films with natural bioactive substances can be a promising alternative to the traditional materials used in the medical industry, for example, as including biodegradable wound dressings or probiotic encapsulation materials. Full article

Gluten is a natural byproduct derived from wheat starch, possessing ideal biocompatibility. However, its poor mechanical properties and heterogeneous structure are not suitable for cell adhesion in biomedical applications. To resolve the issues, we prepare novel gluten (G)/sodium lauryl sulfate (SDS)/chitosan (CS) composite hydrogels by electrostatic and hydrophobic interactions. Specifically, gluten is modified by SDS to give it a negatively charged surface, and then it conjugates with positively charged chitosan to form the hydrogel. In addition, the composite formative process, surface morphology, secondary network structure, rheological property, thermal stability, and cytotoxicity are investigated. Moreover, this work demonstrates that the change can occur in surface hydrophobicity caused by the pH−eading influence of hydrogen bonds and polypeptide chains. Meanwhile, the reversible non−covalent bonding in the networks is beneficial to improving the stability of the hydrogels, which shows a prominent prospect in biomedical engineering. Full article