Konrad Kwiecień

Background/Objectives: Targeted pulmonary delivery of antibiotics offers a favorable approach for the treatment of lower respiratory tract infections (LRTIs) by enhancing local drug concentrations while minimizing systemic exposure. This study aimed to develop and characterize fatty acid-based nanostructured lipid carrier (NLC) microparticles, including tobramycin-loaded formulations, and assess their potential application as carriers for pulmonary drug delivery. Methods: Tobramycin-loaded NLC microparticles were prepared using a hot emulsification method, with lauric acid as the solid lipid and oleic acid as the liquid lipid. The obtained formulations were characterized in terms of morphology, particle size distribution, zeta potential, thermal properties, encapsulation efficiency, drug-release behavior, aerodynamic properties, and powder flowability. Antibacterial activity was evaluated against S. aureus and P. aeruginosa, while cytocompatibility was assessed using BEAS-2B human-lung epithelial cells. Results: The developed microparticles exhibited spherical morphology, with particle characteristics influenced by lipid composition. Incorporation of oleic acid increased tobramycin encapsulation efficiency, reaching approximately 75% at liquid lipid concentrations of 5–15%. Theoretical aerodynamic diameters remained within the respirable range, and increasing oleic acid content improved powder flowability. Drug-release behavior was strongly dependent on lipid composition, with the optimized formulation providing prolonged tobramycin release over 72 h. All formulations preserved antibacterial activity against S. aureus and P. aeruginosa and demonstrated good cytocompatibility with BEAS-2B cells. Conclusions: Fatty acid-based nanostructured lipid microparticles represent a promising active carrier platform for the pulmonary delivery of tobramycin. The developed system demonstrated efficient drug encapsulation, satisfactory particle characteristics, controlled drug release, preserved antibacterial activity, and good biocompatibility, making them a suitable component of dry powders for inhalation (DPI).

Due to the possibility of damage from earthquakes, vibrations, humidity, and the degradation of wooden joints, there is growing interest in new polyurethane adhesives for wooden structures. These adhesives often have two or more purposes in such structures. Such purposes include connection strength, resistance to environmental conditions at the point of application, and behaviour during fire or under vibration. Some fundamental data on the application of materials exhibiting these properties concern their adhesive thermal stability. This paper focuses on the thermal stability of a new blend of flexible and rigid polyurethanes and its correlation with the structural properties of the material. The new polyurethanes were investigated using hot-stage microscopy for thermal stability of shape, and the results were correlated with DSC, thermogravimetry, and evolved-gas analyses. The experiments showed that it is essential to use primary research methods, including FTIR, XRD, DSC-TG-QMS, and HSM, to identify and characterise new polyurethane adhesives. These research methods are crucial for understanding the properties and potential applications of these materials and providing deeper insight into the subject. The tested polyurethane adhesives, new materials for construction, meet strict ecological requirements and are suitable for patching both small and large wooden structures, as well as for other construction applications, such as insulation and soundproofing.

Wood characterized by desired mechanical properties and wood joining material is essential for creating wooden structures. The polymer adhesives are suitable for such applications due to the possibility of energy dissipation from stresses generated by wooden structures and the elimination of thermal bridging, which are common problems in metal joining materials. This research focuses on the thermophysical properties of the laboratory-prepared flexible and rigid polyurethanes to select an appropriate polymer adhesive. Our results showed that the highest thermal stability was in the case of the new PSTF-S adhesive, which reached 230 °C, but the lowest mass loss in the air environment was around 54% for the PS material. The mean thermal expansion coefficient for F&R PU adhesives was 124–164∙10⁻⁶ K⁻¹. The thermal diffusivity of examined adhesives varied between 0.100 and 0.180 mm²s⁻¹. The thermal conductivity, depending on the type of polyurethane, was in the 0.13–0.29 W∙m⁻¹∙K⁻¹ range. The relative decrease in thermal diffusivity after heating the adhesives to 150 °C was from 2% for materials with the lowest diffusivity to 23% for the PU with the highest value of heat transfer. It was found that such data can be used to simulate wooden construction joints in future research.

Materials based on highly reactive α-tricalcium phosphate (α-TCP) powder were developed and evaluated. Furthermore, the impact of different polymeric additives, such as citrus pectin or polyacrylamide (PAAM) modified with sago starch, neem flower, or rambutan peel, on the physiochemical and biological properties of the developed materials was assessed. The addition of modified PAAM shortened the setting process of bone cements and decreased their compressive strength. On the other hand, the addition of citrus pectin significantly enhanced the mechanical strength of the material from 4.46 to 7.15 MPa. The improved mechanical properties of the bone cement containing citrus pectin were attributed to the better homogenization of cementitious pastes and pectin cross-linking by Ca²⁺ ions. In vitro tests performed on L929 cells showed that 10% extracts from α-TCP cements modified with pectin are more cytocompatible than control cements without any additives. Cements containing PAAM with plant-derived modifiers show some degree of cytotoxicity for the highly concentrated 10% extracts, but for diluted extracts, cytotoxicity was reduced, as shown by a resazurin reduction test and live/dead staining. All the developed bone substitutes exhibited in vitro bioactivity, making them promising candidates for further biological studies. This research underscores the advantageous properties of the obtained biomaterials and paves the way for subsequent more advanced in vitro and in vivo investigations.

Background: The use of nanotechnology in the production of medical equipment has opened new possibilities to fight bacterial biofilm developing on their surfaces, which can cause infectious complications. In this study, we decided to use gentamicin nanoparticles. An ultrasonic technique was used for their synthesis and immediate deposition onto the surface of tracheostomy tubes, and their effect on bacterial biofilm formation was evaluated. Methods: Polyvinyl chloride was functionalized using oxygen plasma followed by sonochemical formation and the embedment of gentamicin nanoparticles. The resulting surfaces were characterized with the use of AFM, WCA, NTA, FTIR and evaluated for cytotoxicity with the use of A549 cell line and for bacterial adhesion using reference strains of S. aureus (ATCC^® 25923™) and E. coli (ATCC^® 25922™). Results: The use of gentamicin nanoparticles significantly reduced the adhesion of bacterial colonies on the surface of the tracheostomy tube for S. aureus from 6 × 10⁵ CFU/mL to 5 × 10³ CFU/mL and for E. coli from 1.655 × 10⁵ CFU/mL to 2 × 10¹ CFU/mL, and the functionalized surfaces did not show a cytotoxic effect on A549 cells (ATTC CCL 185). Conclusions: The use of gentamicin nanoparticles on the polyvinyl chloride surface may be an additional supporting method for patients after tracheostomy in order to prevent the colonization of the biomaterial by potentially pathogenic microorganisms.

Implant-related infections are a worldwide issue that is considered very challenging. Conventional therapies commonly end up failing; thus, new solutions are being investigated to overcome this problem. The in situ delivery of the drug at the implant site appears to be more sufficient compared to systemic antibiotic therapy. In this study, we manufactured porous zirconia scaffolds using the foam replication method. To improve their overall bioactivity, they were coated with a calcium phosphate (CaP) layer containing antibiotic-loaded degradable polymer nanoparticles (NPs) obtained by the double emulsion method to achieve the antibacterial effect additionally. Encapsulation efficiency (EE) and drug loading (DL) were superior and were equal to 99.9 ± 0.1% and 9.1 ± 0.1%, respectively. Scaffolds were analyzed with scanning electron microscopy, and their porosity was evaluated. The porosity of investigated samples was over 90% and resembled the microstructure of spongy bone. Furthermore, we investigated the cytocompatibility with osteoblast-like MG-63 cells and antimicrobial properties with Staphylococcus aureus. Scaffolds coated with a CaP layer were found non-toxic for MG-63 cells. Moreover, the presence of antibiotic-loaded nanoparticles had no significant influence on cell viability, and the obtained scaffolds inhibited bacteria growth. Provided processes of fabrication of highly porous zirconia scaffolds and surface functionalization allow minimizing the risk of implant-related infection.

Inhalation-administrated drugs remain an interesting possibility of addressing pulmonary diseases. Direct drug delivery to the lungs allows one to obtain high concentration in the site of action with limited systemic distribution, leading to a more effective therapy with reduced required doses and side effects. On the other hand, there are several difficulties in obtaining a formulation that would meet all the criteria related to physicochemical, aerodynamic and biological properties, which is the reason why only very few of the investigated systems can reach the clinical trial phase and proceed to everyday use as a result. Therefore, we focused on powders consisting of polysaccharides, lipids, proteins or natural and synthetic polymers in the form of microparticles that are delivered by inhalation to the lungs as drug carriers. We summarized the most common trends in research today to provide the best dry powders in the right fraction for inhalation that would be able to release the drug before being removed by natural mechanisms. This review article addresses the most common manufacturing methods with novel modifications, pros and cons of different materials, drug loading capacities with release profiles, and biological properties such as cytocompatibility, bactericidal or anticancer properties.

Bone infections are a serious problem to cure, as systemic administration of antibiotics is not very effective due to poor bone vascularization. Therefore, many drug delivery systems are investigated to solve this problem. One of the potential solutions is the delivery of antibiotics from poly(L-actide-co-glycolide) (PLGA) nanoparticles suspended in the gellan gum injectable hydrogel. However, the loading capacity and release kinetics of the system based on hydrophilic drugs (e.g., gentamycin) and hydrophobic polymers (e.g., PLGA) may not always be satisfying. To solve this problem, we decided to use hydrophobized gentamycin obtained by ion-pairing with dioctyl sulfosuccinate sodium salt (AOT). Herein, we present a comparison of the PLGA nanoparticles loaded with hydrophobic or hydrophilic gentamycin and suspended in the hydrogel in terms of physicochemical properties, drug loading capacity, release profiles, cytocompatibility, and antibacterial properties. The results showed that hydrophobic gentamycin may be combined in different formulations with the hydrophilic one and is superior in terms of encapsulation efficiency, drug loading, release, and antibacterial efficacy with no negative effect on the NPs morphology or hydrogel features. However, the cytocompatibility of hydrophobic gentamycin might be lower, consequently more extensive study on its biological properties should be provided to evaluate a safe dose.

Due to growing antimicrobial resistance to antibiotics, novel methods of treatment of infected wounds are being searched for. The aim of this research was to develop a composite wound dressing based on natural polysaccharides, i.e., gellan gum (GG) and a mixture of GG and alginate (GG/Alg), containing lipid nanoparticles loaded with antibacterial peptide—nisin (NSN). NSN-loaded stearic acid-based nanoparticles (NP_NSN) were spherical with an average particle size of around 300 nm and were cytocompatible with L929 fibroblasts for up to 500 µg/mL. GG and GG/Alg sponges containing either free NSN (GG + NSN and GG/Alg + NSN) or NP_NSN (GG + NP_NSN and GG/Alg + NP_NSN) were highly porous with a high swelling capacity (swelling ratio above 2000%). Encapsulation of NSN within lipid nanoparticles significantly slowed down NSN release from GG-based samples for up to 24 h (as compared to GG + NSN). The most effective antimicrobial activity against Gram-positive Streptococcus pyogenes was observed for GG + NP_NSN, while in GG/Alg it was decreased by interactions between NSN and Alg, leading to NSN retention within the hydrogel matrix. All materials, except GG/Alg + NP_NSN, were cytocompatible with L929 fibroblasts and did not cause an observable delay in wound healing. We believe that the developed materials are promising for wound healing application and the treatment of bacterial infections in wounds.