Search Results (141)

Background/Objectives: The work presented herein focused on the development and characterization of a transdermal caffeine platform fabricated from ultrathin micro- and submicron fibers produced via electrospinning. Methods: The formulations incorporated caffeine encapsulated in a polyethylene oxide (PEO) matrix, combined with various permeation enhancers. A backing layer made of annealed electrospun polycaprolactone (PCL) facilitated the lamination of the two layers to form the final multilayer patch. Comprehensive characterization was conducted, utilizing scanning electron microscopy (SEM) to assess the fiber morphology, attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) for chemical detection and to assess the stability of the caffeine, and differential scanning calorimetry (DSC) along with wide-angle X-ray scattering (WAXS) to analyze the physical state of the caffeine within the fibers of the active layer. Additionally, Franz cell permeation studies were performed using both synthetic membranes (Strat-M) and ex vivo human stratum corneum (SC) to evaluate and model the permeation kinetics. Results: These experiments demonstrated the significant role of enhancers in modulating the caffeine permeation rates provided by the patch, achieving permeation rates of up to 0.73 mg/cm² within 24 h. Conclusions: This work highlights the potential of using electro-hydrodynamic processing technology to develop innovative transdermal delivery systems for drugs, offering a promising strategy for enhancing efficacy and innovative therapeutic direct plasma administration. Full article

As health concerns and regulatory pressures over saturated and trans fats grow, there is a growing need for healthier alternatives to traditional solid fats, such as butter and hydrogenated oils, that are still widely used in the food system. In this study, cellulose particle-based Pickering emulsions (CP-PEs) were prepared from microcrystalline cellulose and ethylcellulose and then foamed to obtain edible oleofoams (CP-EOs) as a solid-fat replacer. The average size of CP-PE droplets without surfactant was 598 ± 69 nm, as confirmed by confocal and transmission electron microscopy. Foaming with citric acid/NaHCO₃ and structuring with ≥6% glyceryl monostearate resulted in CP-EOs with an overrun of 147 ± 4% and volumetric stability for 72 h. Micro-computed tomography showed a uniform microcellular network, while the rheological analysis showed solid-like behavior with a storage modulus higher than butter. Differential scanning calorimetry showed a melting enthalpy similar to unsalted butter (10.1 ± 0.9 J/g). These physicochemical properties demonstrate that CP-EOs can closely mimic the firmness, thermal profile, and mouth-feel of conventional solid fats and may provide a promising solid-fat replacer. Full article

To promote environmental sustainability, this research investigated the potential of utilizing recycled polymethylmethacrylate (PMMA) as raw material in material extrusion (MEX) additive manufacturing (AM). To enhance its mechanical response, carbon black (CB) was employed as the filler in nanocomposite formation. Filament extrusion of the mixture at different concentrations produced printable feedstocks for MEX AM. Rheological analysis (viscosity and material flow rate) showed that the CB introduction to the matrix was beneficial for consistent layer deposition, while differential scanning calorimetry and thermogravimetric analyses verified the thermal stability of the nanocomposites during processing. Mechanical properties were optimized, with increases in modulus (27.8% and 25.8%, respectively, in tensile and bending loadings) and tensile strength at optimal CB loadings. Dynamic mechanical analysis revealed the viscoelastic response of the nanocomposites. Raman and energy dispersive spectroscopy provided element-related insights. Surface morphology and parts structure were observed employing scanning electron microscopy and micro-computed tomography, respectively, revealing a positive impact on the AM parts due to the CB presence in the nanocomposites. The 4 wt.% in CB content nanocomposite was the optimum one. This research pioneers the development of new sustainable nanocomposite filaments and highlights the potential of next-generation MEX-based AM. Full article

Assessing the detailed characteristics of recycled plastics is essential for evaluating their quality and suitability for high-value applications compared to virgin polymers. This review provides a comprehensive overview of advanced analytical techniques used for characterizing the chemical, structural, morphological, and physical properties of recycled polymeric materials. The techniques examined include Fourier Transform Infrared Spectroscopy (FTIR), Micro-Raman spectroscopy, X-ray Fluorescence (XRF), Inductively Coupled Plasma (ICP) techniques, X-ray Powder Diffraction (XRPD), Differential Scanning Calorimetry (DSC), and Scanning Electron Microscopy (SEM). These methods are critically assessed for their effectiveness in detecting polymer degradation, surface and structural alterations, and the presence of contaminants—factors frequently introduced during mechanical recycling processes. For each technique, this review outlines the working principles, sample preparation protocols, and illustrative case studies while discussing their advantages, limitations, and operational challenges. By synthesizing current knowledge and methodological advancements, this review aims to support the development of robust and standardized quality assessment protocols. Enhancing the reliability and precision of recycled plastic characterization will improve their acceptance as high-quality secondary raw materials, thereby facilitating their upcycling and contributing to the broader goals of the circular economy. Full article

Non-isothermal differential scanning calorimetry (DSC) and Raman microscopy were used to study the crystallization behavior of the 20–50 μm amorphous nifedipine (NIF) powder. In particular, the study was focused on the diffusionless glass-crystal (GC) growth mode occurring below the glass transition temperature (T_g). The exothermic signal associated with the GC growth was indeed directly and reproducibly recorded at heating rates q⁺ ≤ 0.5 °C·min⁻¹. During the GC growth, the α_p polymorphic phase was exclusively formed, as confirmed via Raman microscopy. In addition to the freshly prepared NIF samples, the crystallization of the powders annealed for 7 h at 20 °C was also monitored—approx. 50–60% crystallinity was achieved. For the annealed NIF powders, the confocal Raman microscopy verified a proportional absence of the crystalline phase on the sample surface (indicating its dominant formation along the internal micro-cracks, which is characteristic of the GC growth). All DSC data were modeled in terms of the solid-state kinetic equation paired with the autocatalytic model; the kinetic complexity was described via reaction mechanism based on the overlap of 3–4 independent processes. The kinetic trends associated with decreasing q⁺ were identified, confirming the temperature-dependent kinetic behavior, and used to calculate a theoretical kinetic prediction conformable to the experimentally performed 7 h annealing at 20 °C. The theoretical model slightly underestimated the true extent of the GC growth, predicting the crystallinity to be 35–40% after 7 h (such accuracy is still extremely good in comparison with the standard kinetic approaches nowadays). Further research in the field of kinetic analysis should thus focus on the methodological ways of increasing the accuracy of considerably extrapolated kinetic predictions. Full article

Background: Ciprofloxacin (CIP) is a poorly water-soluble fluoroquinolone-type antibiotic that can be useful in the treatment of lung infections. When the drugs are delivered directly to the lungs, a smaller dosage is needed to achieve the desired effect compared to the oral administration. Moreover, the application of nanoparticles potentially enhances the effectiveness of the treatments while lowering the possible side effects. Therefore, we aimed to develop a “nano-in-micro” structured dry powder inhaler formulation containing CIP. Methods: A two-step preparation method was used. Firstly, a nanosuspension was first prepared using a high-performance planetary mill by wet milling. After the addition of different additives (leucine and mannitol), the solid formulations were created by spray drying. The prepared DPI samples were analyzed by using laser diffraction, nanoparticle tracking analysis, scanning electron microscopy, X-ray powder diffraction, and differential scanning calorimetry. The solubility and in vitro dissolution tests in artificial lung fluid and in vitro aerodynamic investigations (Spraytec^® device, Andersen Cascade Impactor) were carried out. Results: The nanosuspension (D50: 140.0 ± 12.8 nm) was successfully prepared by the particle size reduction method. The DPIs were suitable for inhalation based on the particle diameter and their spherical shape. Improved surface area and amorphization after the preparation processes led to faster drug release. The excipient-containing systems were characterized by large lung deposition (fine particle fraction around 40%) and suitable aerodynamic diameter (between 3 and 4 µm). Conclusions: We have successfully formulated a nanosized antibiotic-containing formulation for pulmonary delivery, which could provide a potential treatment for patients with different respiratory infections. Full article

The inherent porous structure of concrete enables the penetration of water and Cl⁻ ions through its pores, which eventually leads to rebar corrosion within the concrete. Consequently, the densification and impermeability of concrete protective layers play a critical role in the durability of reinforced concrete structures. This study proposes a composite anti-corrosion treatment for mortar protective layers by integrating nano-ion capillary crystalline with silane hydrophobic processing. Targeting existing mortar samples, a series of experiments were conducted, utilizing scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), differential scanning calorimetry-thermogravimetry (DSC-TG), X-ray computed tomography (X-CT), contact angle measurements, permeability tests, and electrochemical tests. These experiments systematically evaluated the effects of composite anti-corrosion treatment on the microstructure of hydration products, pore characteristics, surface hydrophobicity, impermeability, and the overall corrosion resistance of mortar-rebar samples in a Cl⁻-contained environment. The results reveal that nano-ion capillary crystalline materials react with free calcium ions in the mortar to produce secondary hydration products, effectively filling micro-pores, densifying the pore structure and inhibiting the invasion of Cl⁻ ions. The combination of capillary crystalline and silane hydrophobic processing synergistically enhances surface hydrophobicity and impermeability, preventing the ingress of corrosive agents, such as Cl⁻ ions, and significantly improving the anti-corrosion performance of mortar in a Cl⁻-contained environment. Full article

Laser micro-machining is a rapidly growing technique to create, manufacture and fabricate microstructures on different materials ranging from metals and ceramics to polymers. Micro- and nano-machining on different materials has been helpful and useful for various biomedical applications. This study focuses on the micro-machining of innovative barbed sutures using an ultrashort pulse laser, specifically a femtosecond (fs) laser system. Two bioresorbable polymeric materials, namely, catgut and poly (4-hydroxybutyrate) (P4HB), were studied and micro-machined using the femtosecond (fs) laser system. The optimized laser parameter was used to fabricate two different barb geometries, namely, straight and curved barbs. The mechanical properties were evaluated via tensile testing, and the anchoring performance was studied by means of a suture–tissue pull-out protocol using porcine dermis tissue which was harvested from the medial dorsal site. Along with the evaluation of the mechanical and anchoring properties, the thermal characteristics and degradation profiles were assessed and compared against mechanically cut barbed sutures using a flat blade. The mechanical properties of laser-fabricated barbed sutures were significantly improved when compared to the mechanical properties of the traditionally/mechanically cut barbed sutures, while there was not any significant difference in the anchoring properties of the barbed sutures fabricated through either of the fabrication techniques. Based on the differential scanning calorimetry (DSC) results for thermal transitions, there was no major impact on the inherent material properties due to the laser treatment. This was also observed in the degradation results, where both the mechanically cut and laser-fabricated barbed sutures exhibited similar profiles throughout the evaluation time period. It was concluded that switching the fabrication technique from mechanical cutting to laser fabrication would be beneficial in producing a more reproducible and consistent barb geometry with more precision and accuracy. Full article

Objectives: This study aimed to identify and develop a novel, safe, and effective transdermal penetration enhancer derived from the leaves of Perilla frutescens (L.) Britt, and to explore the underlying mechanisms of its penetration enhancement effects. Methods: To evaluate the safety profile of the penetration enhancer, both skin irritation tests and histopathological analyses were conducted. The transdermal enhancement capabilities of the penetration enhancer were assessed in vitro using five model drugs. Furthermore, to gain insights into the penetration enhancement mechanism of this novel penetration enhancer, a range of analytical methods were used, including a spectroscopic technique, differential scanning calorimetry, micro-optical techniques, and molecular docking simulations. Results: Perilla essential oil contained 93.70% perilla ketone (PEK), which exhibited a safety profile superior to that of azone. PEK significantly increased the cumulative skin permeation of all the model drugs (p < 0.05). PEK exhibited the most obvious impact on puerarin penetration, with quantitative enhancement ratios of 2.96 ± 0.07 and 3.39 ± 0.21 at concentrations of 3% and 5% (w/v), respectively. A strong correlation between the enhancement effect of PEK and the physicochemical properties of the drugs was observed. Mechanistic studies revealed that PEK facilitates drug distribution from the solution phase to the stratum corneum (SC). Conclusions: PEK, seldom discussed in former studies, was observed to show extensive penetration enhancement effects by inducing conformational changes in SC lipids and disrupting the tightly ordered bilayer arrangement of lipids. These findings highlight the potential of PEK as a promising and safe natural transdermal penetration enhancer. Full article

Background: This study aimed at investigating the prolonged effects of glucocorticoids and bisphosphonates on bone. Methods: Six-to-eight-month-old skeletally mature male Sprague Dawley rats were randomized to receive a cancer therapy combination of zoledronic acid (ZA = 0.13 mg/kg) and dexamethasone (DX = 3.8 mg/kg) (treatment group, n = 10) or sterile phosphate buffer saline solution (control group, n = 10). The rats received weekly intraperitoneal injections for 8 weeks, which were stopped 6 weeks before euthanasia. Mineralized bone samples were characterized by three-point bending tests, micro-CT imaging, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). Bone collagen was assessed using tensile tests on the demineralized bones and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy on mineralized and demineralized bones. Results: The samples in the treatment group showed increased tibial cortical thickness, mineral crystal size, and toughness. Analyses of demineralized tibiae revealed decreased collagen tensile strength in the experimental group. The spectroscopic and TGA/DSC analyses showed that the ZA + DX treatment increased the collagen amide I 1660/1690 cm⁻¹ area ratio and collagen denaturalization temperature, indicating a higher level of collagen cross-linking. Conclusions: Bisphosphonates and glucocorticoids led to prolonged changes in the mechanical properties of bone as a result of increased cortical thickness, increased crystal size, and the deterioration of collagen quality. Full article

The particle size-dependent processes of structural relaxation and crystal growth in amorphous nifedipine were studied by means of non-isothermal differential scanning calorimetry (DSC) and Raman microscopy. The enthalpy relaxation was described in terms of the Tool–Narayanaswamy–Moynihan model, with the relaxation motions exhibiting the activation energy of 279 kJ·mol⁻¹ for the temperature shift, but with a significantly higher value of ~500 kJ·mol⁻¹ being obtained for the rapid transition from the glassy to the undercooled liquid state (the latter is in agreement with the activation energy of the viscous flow). This may suggest different types of relaxation kinetics manifesting during slow and rapid heating, with only a certain portion of the relaxation motions occurring that are dependent on the parameters of a given temperature range and time frame. The DSC-recorded crystallization was found to be complex, consisting of four sub-processes: primary crystal growth of α_p and β_p polymorphs, enantiotropic β_p → β_p′ transformation, and β_p/β_p′ → α_p recrystallization. Overall, nifedipine was found to be prone to the rapid glass-crystal growth that occurs below the glass transition temperature; a tendency of low-temperature degradation of the amorphous phase markedly increased with decreasing particle size (the main reason being the increased number of surface and bulk micro-cracks and mechanically induced defects). The activation energies of the DSC-monitored crystallization processes varied in the 100–125 kJ·mol⁻¹ range, which is in agreement with the microscopically measured activation energies of crystal growth. Considering the potential correlations between the structural relaxation and crystal growth processes interpreted within the Transition Zone Theory, a certain threshold in the complexity and magnitude of the cooperating regions (as determined from the structural relaxation) may exist, which can lead to a slow-down of the crystal growth if exceeded. Full article

The properties of thin polymer films are influenced by the size of the fillers, their morphology, the surface properties and their distribution/interaction in the polymer matrix. In this work, thin polymer composite films with MoO₃ or SiO₂ nano and micro fillers in PVDF-HFP/PVP polymer matrix were successfully fabricated using the solvent casting method. The effects of different types, sizes and morphologies of the inorganic fillers on the crystallization of the PVDF-HFP polymer were investigated, as well as the effects on the thermal and mechanical properties of the composites. Scanning electron microscopy, ATR-FTIR spectroscopy, differential scanning calorimetry, nanoindentation and uniaxial mechanical tests were used for characterization. The results showed that MoO₃ nanowires thermally stabilized the polymer matrix, induced crystallization of the PVDF-HFP polymer in all three polymorphs (α-, β-, γ-phase) and formed a geometrical network in the polymer matrix, resulting in the highest elastic moduli, hardness and Young’s modulus. Full article

Recent studies have focused on the development of bio-based products from sustainable resources using green extraction approaches, especially nanocellulose, an emerging nanoparticle with impressive properties and multiple applications. Despite the various sources of cellulose nanofibers, the search for alternative resources that replace wood, such as Lygeum spartum, a fast-growing Mediterranean plant, is crucial. It has not been previously investigated as a potential source of nanocellulose. This study investigates the extraction of novel cellulose micro/nanofibers from Lygeum spartum using a two-step method, including both alkali and mechanical treatment as post-treatment with ultrasound, as well as homogenization using water and dilute alkali solution as a solvent. To determine the structural properties of CNFs, a series of characterization techniques was applied. A significant correlation was observed between the Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) results. The FTIR results revealed the elimination of amorphous regions and an increase in the energy of the H-bonding modes, while the XRD results showed that the crystal structure of micro/nanofibers was preserved during the process. In addition, they indicated an increase in the crystallinity index obtained with both methods (deconvolution and Segal). Thermal analysis based on thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) confirmed improvement in the thermal properties of the isolated micro/nanofibers. The temperatures of maximum degradation were 335 °C and 347 °C. Morphological analysis using a scanning electron microscope (SEM) and atomic force microscope (AFM) showed the formation of fibers along the axis, with rough and porous surfaces. The findings indicate the potential of Lygeum spartum as a source for producing high-quality micro/nanofibers. A future direction of study is to use the cellulose micro/nanofibers as additives in recycled paper and to evaluate the mechanical properties of the paper sheets, as well as investigate their use in smart paper. Full article

This study aimed to investigate the potential of antimony-doped tin oxide (ATO) as a reinforcing agent for polyamide 12 (PA12) in 3D printing by examining four mixtures with varying ATO concentrations (2.0 to 8.0 wt.%, with a 2.0 wt.% interval). These mixtures were used to fabricate filaments for the manufacturing of specimens through the material extrusion method. The mechanical properties of the resulting PA12/ATO composites and PA12 pure samples were evaluated through tensile, Charpy impact, flexural, and microhardness tests. Additionally, rheology, structure, morphology, thermal properties, pore size, and consistency in the dimensions of the samples were evaluated. Thermogravimetric analysis, along with differential scanning calorimetry, scanning electron microscopy, energy-dispersive and Raman spectroscopy, and micro-computed tomography, were conducted. The results were correlated and interpreted. The greatest reinforcement was achieved with the PA12/ATO 4.0 wt.% mixture, which exhibited a 19.3% increase in tensile strength and an 18.6% increase in flexural strength compared with pure PA12 (the control samples). The Charpy impact strength and microhardness were also improved by more than 10%. These findings indicate the merit of composites with ATO in additive manufacturing, particularly in the production of components with improved mechanical performance. Full article

Thermoresponsive shape memory polymers (SMPs) have garnered increasing interest for their exceptional ability to retain a temporary shape and recover the original configuration through temperature changes, making them promising in various applications. The SMP shape change and recovery that happen due to a combination of mechanical loading and appropriate temperatures are related to its particular microstructure. The deformation process leads to the formation and growth of micro-cracks in the SMP structure, whereas the subsequent heating over its glass transition temperature T_g leads to the recovery of its original shape and properties. These processes also affect the SMP microstructure. In addition to the observed macroscopic shape recovery, the healing of micro-crazes and micro-cracks that have nucleated and developed during the loading occurs. Therefore, our study delves into the microscopic aspect, specifically addressing the healing of micro-cracks in the cyclic loading process. The proposed research concerns a thermoplastic polyurethane shape memory polymer (PU-SMP) MM4520 with a T_g of 45 °C. The objective of the study is to investigate the effect of the number of tensile loading-unloading cycles and thermal shape recovery on the evolution of the PU-SMP microstructure. To this end, comprehensive research starting from structural characterization of the initial state and at various stages of the PU-SMP mechanical loading was conducted. Dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), wide-angle X-ray scattering (WAXS) and scanning electron microscopy (SEM) were used. Moreover, the shape memory behavior in the thermomechanical loading program was investigated. The obtained average shape fixity value was 99%, while the shape recovery was 92%, which confirmed good shape memory properties of the PU-SMP. Our findings reveal that even during a single loading-unloading tension cycle, crazes and cracks nucleate on the surface of the PU-SMP specimen, whereas the subsequent temperature-induced shape recovery process carried out at the temperature above T_g enables the healing of micro-cracks. Interestingly, the surface of the specimen after three and five loading-unloading cycles did not exhibit crazes and cracks, although some traces of cracks were visible. The traces disappeared after exposing the material to heating at T_g + 20 °C (65 °C) for 30 min. The crack closure phenomenon during deformation, even without heating over T_g, occurred within three and five subsequent cycles of loading-unloading. Notably, in the case of eight loading-unloading cycles, cracks appeared on the surface of the PU-SMP and were healed only after thermal recovery at the particular temperature over T_g. Upon reaching a critical number of cycles, the proper amount of energy required for crack propagation was attained, resulting in wide-open cracks on the material’s surface. It is worth noting that WAXS analysis did not indicate strong signs of typical highly ordered structures in the PU-SMP specimens in their initial state and after the loading history; however, some orientation after the cyclic deformation was observed. Full article