Search Results (162)

Polyvinyl alcohol (PVA) hydrogels have emerged as versatile materials due to their exceptional biocompatibility and tunable mechanical properties, showing great promise for flexible sensors, smart wound dressings, and tissue engineering applications. However, rational design remains challenging due to complex structure–property relationships involving multiple formulation parameters. This study presents an interpretable machine learning framework for predicting PVA hydrogel tensile strain properties with emphasis on mechanistic understanding, based on a comprehensive dataset of 350 data points collected from a systematic literature review. XGBoost demonstrated superior performance after Optuna-based optimization, achieving R² values of 0.964 for training and 0.801 for testing. SHAP analysis provided unprecedented mechanistic insights, revealing that PVA molecular weight dominates mechanical performance (SHAP importance: 84.94) through chain entanglement and crystallization mechanisms, followed by degree of hydrolysis (72.46) and cross-linking parameters. The interpretability analysis identified optimal parameter ranges and critical feature interactions, elucidating complex non-linear relationships and reinforcement mechanisms. By addressing the “black box” limitation of machine learning, this approach enables rational design strategies and mechanistic understanding for next-generation multifunctional hydrogels. Full article

A series of hydrogels containing sodium alginate at different concentrations (2%, 3%, and 4%) and egg white were prepared through ionic cross-linking with calcium chloride (CaCl₂) to obtain composite dressing materials. ZnO nanoparticles coated with eucalyptus or lavender essential oil were introduced into the hydrogel matrix to enhance antibacterial properties. The resulting hydrogels were freeze-dried to enhance mechanical properties, increase the porosity of the dressing, and facilitate further evaluations. A variety of analytical methods, including scanning electron microscopy (SEM), X-ray dispersive spectroscopy (EDS), and Fourier transform infrared spectroscopy (FT-IR) were employed to characterize the composites. The developed composites exhibited high porosity and a swelling degree exceeding 200% after 3 days. Additionally, water absorption capacity increased with higher alginate concentrations in the samples. Furthermore, they demonstrated significant antibiofilm activity against Staphylococcus aureus, Enterococcus faecalis, and Escherichia coli, with the samples containing 4% alginate showing the best results. Full article

High and large-spectrum antibacterial features and ROS scavenging properties are the most important requirements for efficient wound-dressing materials. A composite hydrogel was synthesized herein by a one-pot procedure embedding silver nanoparticles (AgNPs) covered with oxidized gum arabic (OGA) within gelatin (Gel) hydrogel. Small (2–20 nm), round-shaped AgNPs (ζ = −22 mV) were first obtained by green synthesis using OGA as a reducing and capping agent. Composite hydrogels, containing 0.6 and 1.3 wt.% Ag, were obtained by the covalent cross-linking (Schiff base reaction) of amine groups in gelatin with the dialdehyde groups located on the shell of the AgNPs. Thus, the uniform distribution of the AgNPs in the network contributed to the increased physicochemical and hydrolytic stability of the hydrogels. Moreover, the high swelling degree together with the good mechanical properties make them appropriate candidates for wound-healing materials. The hydrogels exhibited 80% scavenging activity of ABTS^●+ free radicals after 6 h of incubation and were effective against E. coli and S. aureus, achieving a 4% survival of bacteria within 3 h (E. coli) and 24 h (S. aureus). These results clearly indicate that the proposed hydrogels have potential in wound-dressing applications. Full article

The delayed healing and infection risks associated with chronic wounds and burns pose significant clinical challenges. Traditional dressings provide basic coverage but lack the bioactive properties needed for tissue regeneration and antimicrobial protection. In this study, we developed zinc alginate hydrogel-coated traditional wound dressings (WD@AlgZn) and evaluated their physicochemical properties, antimicrobial performance, and in vivo healing efficacy. Scanning electron microscopy (SEM) revealed a uniform coating of the zinc alginate network on dressing fibers, while Fourier-transform infrared spectroscopy (FT-IR) confirmed the successful incorporation of zinc ions. Antimicrobial assays further demonstrated that WD@AlgZn reduced bacterial loads (CFU/mL counts) by several orders of magnitude for both Staphylococcus aureus and Escherichia coli compared to uncoated controls. An in vivo rat burn wound model exhibited accelerated wound closure when using WD@AlgZn dressings compared to conventional wound care approaches, achieving a 90.75% healing rate by day 21, significantly outperforming the silver sulfadiazine (52.32%), uncoated-dressing (46.58%), and spontaneous-healing (37.25%) groups. Histological analysis confirmed enhanced re-epithelialization, neovascularization, and reduced inflammation in WD@AlgZn-treated tissues. The findings suggest that WD@AlgZn offers a promising alternative for advanced wound management, combining structural robustness with bioactive properties to support efficient wound healing and infection control. These results provide valuable insights into the potential clinical applications of metal-ion cross-linked biopolymeric hydrogel dressings for next-generation wound care strategies. Full article

We propose a scheme for realizing nonreciprocal optical scattering with non-Hermitian four-wave mixing (FWM) in a double-$\mathsf{\Lambda }$ system of cold atoms driven by coupling and dressing phase-mismatched standing-wave (SW) fields. Four scattering channels—direct transmission, cross transmission, direct reflection, and cross reflection—can be established for a probe and a signal field, some of which are nonreciprocal due to non-Hermitian spatial modulations when the two SW driving fields exhibit a $\pi /4$ phase shift. We find in particular that it is viable to attain single-color unidirectional transport, dual-color unidirectional transport, and single-color directional blockade with respect to a probe and a signal field incident upon this atomic sample from the same side, due to perfect destructive interference between direct and cross scattering channels. This work provides a new paradigm for studying non-Hermitian nonlinear optics and offers a theoretical foundation for designing all-optical atomic devices based on multi-channel nonreciprocal scattering. Full article

Background/Objectives: Activities of Daily Living (ADLs) are crucial for assessing an individual’s autonomy, encompassing tasks such as eating, dressing, and moving around, among others. Predicting these activities is part of health monitoring, elderly care, and intelligent systems, improving quality of life, and facilitating early dependency detection, all of which are relevant components of personalized health and social care. However, the automatic classification of ADLs from sensor data remains challenging due to high variability in human behavior, sensor noise, and discrepancies in data acquisition protocols. These challenges limit the accuracy and applicability of existing solutions. This study details the modeling and evaluation of real-time ADL classification models based on batch learning (BL) and stream learning (SL) algorithms. Methods: The methodology followed is the Cross-Industry Standard Process for Data Mining (CRISP-DM). The models were trained with a comprehensive dataset integrating 23 ADL-centric datasets using accelerometers and gyroscopes data. The data were preprocessed by applying normalization and sampling rate unification techniques, and finally, relevant sensor locations on the body were selected. Results: After cleaning and debugging, a final dataset was generated, containing 238,990 samples, 56 activities, and 52 columns. The study compared models trained with BL and SL algorithms, evaluating their performance under various classification scenarios using accuracy, area under the curve (AUC), and F1-score metrics. Finally, a mobile application was developed to classify ADLs in real time (feeding data from a dataset). Conclusions: The outcome of this study can be used in various data science projects related to ADL and Human activity recognition (HAR), and due to the integration of diverse data sources, it is potentially useful to address bias and improve generalizability in Machine Learning models. The principal advantage of online learning algorithms is dynamically adapting to data changes, representing a significant advance in personal autonomy and health care monitoring. Full article

Alginate-ZnO nanoparticles (ZnO_nano) composite wound dressing membranes were prepared with two different ZnO_nano concentrations (0.03 and 0.20 g ZnO/g sodium alginate) and cross-linked with two different calcium treatments (low and high Ca⁺⁺concentration) to evaluate the influence of nanoparticle content and cross-linking degree on membrane attributes. ZnO_nano addition did not significantly alter the mechanical properties, water vapor permeability, swelling degree in water and the alginate amorphous nature of the nanocomposite membranes. The increase in cross-linking degree, on the other hand, altered the microstructure of the membranes, increased the tensile strength and reduced the water vapor permeability of the nanocomposite membranes. The presence of ZnO_nano in alginate membranes granted them antibacterial activity in vitro against Pseudomonas aeruginosa and Staphylococcus aureus and substantially increased the absorption capacity in phosphate buffer and fetal bovine serum solutions, validating their potential use as wound dressings. Full article

Excessive blood loss is a leading cause of mortality among soldiers and accident victims. The wound healing process typically ranges from three weeks to several months, with disruptions in healing stages potentially prolonging recovery time. Chronic wounds may persist for years, creating a favorable environment for microbial growth. Chitosan, a derivative of chitin—the second most abundant biopolymer in nature—is obtained through deacetylation and exhibits mucoadhesive, analgesic, antioxidant, biodegradable, non-toxic, and biocompatible properties. Due to its hemostatic and regenerative support capabilities, chitosan is widely applied in the food, cosmetic, and agricultural industries; environmental protection; and as a key component in dressings for chronic wound healing. Notably, its antibacterial properties make it a promising candidate for novel biomaterials to replace traditional antibiotics and prevent the emergence of drug-resistant strains. The primary aim of this study was the chemical cross-linking of chitosan with the amino acids L-aspartic and L-glutamic acid in the presence of periclase (magnesium oxide) under microwave radiation conditions. Subsequent research stages involved the analysis of the samples’ physicochemical properties using SEM, FT-IR, XPS, atomic absorption spectrometry, swelling behavior (in water, SBF, and blood), porosity, and density. Biological assessments included biodegradation, cytotoxicity, and antibacterial activity against Escherichia coli and Staphylococcus aureus. The obtained results confirmed the high potential of the newly developed hemostatic agents for effective hemorrhage management under non-sterile conditions. Full article

Objective: This study aimed to analyze and compare three different methods of estimated blood loss (EBL) assessment in conjunction with the exploration of risk factors associated with early postpartum hemorrhage (PPH) among women undergoing a cesarean section (CS). Methods: Women with a singleton pregnancy who underwent an elective/emergency CS were recruited for this prospective cross-sectional study. Early PPH was defined as a cumulative blood loss ≥1000 mL within the 24 h period following the delivery. Methods of EBL assessment included the following: (1) visual estimation by the surgeon (sEBL), (2) the evaluation of blood-soaked dressings (dEBL), and (3) implementation of a mathematical formula (fEBL). Results: In the study period, 21 cases of early PPH were identified and compared with 452 controls. Among the patients with a PPH, a significant increase in the surgery time (60 min. vs. 46 min., p = 0.001), fetal birthweight (3780 g vs. 3417.5 g, p < 0.01), the occurrence of uterine atony (61.9% vs. 2.2%, p < 0.001), and myomas (9.5% vs. 1.1%, p < 0.05) was noted. In both groups, dEBL and sEBL provided the highest and the lowest EBL values, respectively (PPH dEBL: 1230 mL vs. fEBL: 1173.3 mL vs. sEBL 1000 mL, p < 0.001; control dEBL: 652 mL vs. fEBL 604 mL vs. sEBL 600 mL, p < 0.001). A patient age of 31–34 years (OR 1.71; 95%CI: 1.19–2.44), overweight (OR 2.65; 95%CI: 1.87–3.76), obesity (OR 2.68; 95%CI: 1.71–4.21), emergency mode of CS (OR 4.06; 95%CI: 2.94–5.62), surgeon experience (resident OR 1.86; 95%CI: 1.27–2.7; assistant specialist OR 3.13; 95%CI: 2.15–4.55) and fetal macrosomia (OR 3.19; 95%CI: 2.14–4.74) were selected as significant risk factors of the PPH. Conclusions: In women with early PPH following a CS, both dEBL and fEBL provide comparable estimations of blood loss. An emergency-mode CS and fetal macrosomia are the strongest contributors to PPH among women undergoing a CS. A combination of different methods of EBL with the proper identification of risk factors of a PPH can lead to improvement in the clinical management of obstetric hemorrhage following the CS. Full article

In this study, a hydrogel material based on porcine gelatin and sodium alginate was synthesized for use as a dressing for chronic wound treatment. The hydrogels were covalently cross-linked using polyethylene glycol diglycidyl ether (PEGDE 500), and the interaction between the components was confirmed via FTIR. The properties of the resulting hydrogels were examined, including gel-fraction volume, swelling degree in different media, mechanical properties, pore size, cytotoxicity, and the ability to absorb and release analgesics (lidocaine, novocaine, sodium diclofenac). The hydrogel’s resistance to enzymatic action by protease was enhanced both through chemical cross-linking and physical interactions between gelatin and alginate. The absorption capacity of the hydrogels, reaching 90 g per dm² of the hydrogel dressing, indicates their potential for absorbing wound exudates. It was demonstrated that the antiseptic (chlorhexidine) contained in the structured gelatin–alginate hydrogels can be released into an infected substrate, resulting in a significant inhibition of pathogenic microorganisms (Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Aspergillus niger). These results clearly demonstrate that the obtained hydrogel materials can serve as non-traumatic dressings for the treatment of chronic and/or infected wounds. Full article

Background: Osteoarticular deformities or contractures in institutionalized elderly individuals, described as acquired deforming hypertonia (ADH), have a multifactorial origin. The reported prevalence of ADH in French Caucasian patients in long-term care units (LTCUs) is 25.6%. To date, ADH in the Caribbean population has never been studied. We aimed to assess the prevalence and characteristics of ADH in such a population. Materials and Methods: This was a cross-sectional observational study of a French Caribbean population in Martinique in which patients aged 75 years or older were institutionalized in LTCUs during the study period. Data extraction from the medical files of eligible LTCU patients was conducted to assess the prevalence, clinical characteristics, and impact of ADH on patients’ daily care. The assessments were performed collaboratively between the patients’ geriatric team and a PM&R physician. Results: In total, 81 patients were included, with an ADH prevalence of 77.8%. Reported ADH was bilateral (86%) or multiple (66% of patients had ≥5 ADH) and was responsible for major alterations in terms of hygiene, dressing, pain, and skin damage. ADH patients had a high level of dependence (GMP = 924), and this level of dependence was significantly associated with the presence of at least one ADH (p < 0.001) regardless of prior disease. Conclusions: The incidence of ADH in our Caribbean population seems twice as high as that in Caucasian patients, underlining the necessity for this nosological framework to be better recognized, particularly in an insular context. Local campaigns for the prevention and recognition of ADH must be considered, and targeted multidisciplinary protocols need to be established for adapted care in all institutions receiving elderly people. Full article

Chitosan is a positively charged natural polymer with several properties conducive to wound-healing applications, such as biodegradability, structural integrity, hydrophilicity, adhesiveness to tissue, and bacteriostatic potential. Along with other mechanical properties, some of the properties discussed in this review are antibacterial properties, mucoadhesive properties, biocompatibility, high fluid absorption capacity, and anti-inflammatory response. Chitosan forms stable complexes with oppositely charged polymers, arising from electrostatic interactions between (+) amino groups of chitosan and (−) groups of other polymers. These polyelectrolyte complexes (PECs) can be manufactured using various materials and methods, which brings a diversity of formulations and properties that can be optimized for specific wound healing as well as other applications. For example, chitosan-based PEC can be made into dressings/films, hydrogels, and membranes. There are various pros and cons associated with manufacturing the dressings; for instance, a layer-by-layer casting technique can optimize the nanoparticle release and affect the mechanical strength due to the formation of a heterostructure. Furthermore, chitosan’s molecular weight and degree of deacetylation, as well as the nature of the negatively charged biomaterial with which it is cross-linked, are major factors that govern the mechanical properties and biodegradation kinetics of the PEC dressing. The use of chitosan in wound care products is forecasted to drive the growth of the global chitosan market, which is expected to increase by approximately 14.3% within the next decade. This growth is driven by products such as chitoderm-containing ointments, which provide scaffolding for skin cell regeneration. Despite significant advancements, there remains a critical gap in translating chitosan-based biomaterials from research to clinical applications. Full article

With the growing use of crossbred cattle in Brazilian feedlots and increasing pressure to reduce antibiotic use as growth promoters, this study examines the impact of three feed additives—monensin (MON), monensin with Lithothamnium calcareum (LCM), and a blend of essential oils (BEO)—on the performance of Nellore (NEL) and crossbred (CROSS) cattle. A total of 90 Nellore and 90 crossbred bulls were assigned to a completely randomized block design with a 2 × 3 factorial design for 112 days, and all received the same diet with varying additives. Their methane (CH₄) emissions were estimated. All data were analyzed using the emmeans package of R software (version 4.4.1). Crossbred cattle outperformed Nellore in average daily gain (ADG), hot carcass weight (HCW), and dry matter intake (DMI), though feed efficiency remained unaffected. Across additives, no significant differences were observed in ADG, HCW, or dressing percentage. However, LCM had a lower DMI than the BEO, while MON showed better feed efficiency than the BEO. A breed-by-additive interaction trend was noted for DMI as a percentage of body weight (DMI%BW), with Nellore bulls on LCM diets showing the lowest DMI%BW. Crossbreeds had greater net energy (NE) requirements for maintenance (NEm) and gain (NEg), and MON-fed animals had greater NEm and NEg than the BEO. Crossbred bulls had greater daily methane (CH₄) emissions than Nellore bulls. Animals on the BEO had greater daily CH₄ emissions and greater g CH₄/kg metabolic BW than LCM bulls. In conclusion, the addition of Lithothamnium calcareum to monensin did not enhance performance compared to monensin alone. Monensin outperformed the BEO in feed efficiency and nutrient utilization. Full article

Background/Objectives: Freeze-drying is a dehydration method that extends the shelf life and stability of drugs, vaccines, and biologics. Recently, its role has expanded beyond preservation to improve novel pharmaceuticals and their carriers, such as hydrogels, which are widely studied for both drug delivery and wound healing. The main aim of this study was to explore the multifunctional role of freeze-drying in improving the physicochemical properties of sodium alginate/poly(vinyl alcohol)-based hydrogels for medical applications. Methods: The base matrix and hydrogels containing a nanocarrier-drug system, were prepared by chemical cross-linking and then freeze-dried for 24 h at −53 °C under 0.2 mBa. Key analyses included determination of gel fraction, swelling ratio, FT-IR, SEM, TG/DTG, in vitro drug release and kinetics, and cytotoxicity assessment. Results: Freeze-drying caused an increase in the gel fraction of the hydrogel with the dual drug delivery system from 55 ± 1.6% to 72 ± 0.5%. Swelling ability was pH-dependent and remained in the same range (175–282%). Thermogravimetric analysis showed that freeze-dried hydrogels exhibited higher thermal stability than their non-freeze-dried equivalents. The temperature at 10% weight loss increased from 194.0 °C to 198.9 °C for the freeze-dried drug-loaded matrix, and from 188.4 °C to 203.1 °C for the freeze-dried drug-free matrix. The average pore size of the freeze-dried hydrogels was in the range of 1.07 µm ± 0.54 to 1.74 µm ± 0.92. In vitro drug release revealed that active substances were released in a controlled and prolonged way, according to the Korsmeyer–Peppas model. The cumulative amount of salicylic acid released at pH = 9.0 after 96 h was 63%, while that of fluocinolone acetonide reached 73%. Both hydrogels were non-toxic to human fibroblast cells, maintaining over 90% cell viability after 48 h of incubation. Conclusions: The results show a high potential for commercialisation of the obtained hydrogels as medical dressings. Full article

Objectives: Hydrogels produced using the freeze–thaw method have demonstrated significant potential for wound management applications. However, their production requires precise control over critical factors including freezing temperature and the choice of matrix-forming excipients, for which no consensus on the optimal conditions currently exists. This study aimed to address this gap by evaluating the effects of the above-mentioned variables on cryogel performance. Methods: Mechanical properties, absorption capacity, and microstructure were assessed alongside advanced analyses using differential scanning calorimetry (DSC) and low-field nuclear magnetic resonance relaxometry (LF TD NMR). Results: The results demonstrated that fully hydrolyzed polyvinyl alcohol (PVA) with a molecular weight above 61,000 g/mol is essential for producing high-performance cryogels. Among the tested formulations, an 8% (w/w) PVA_56–98 solution (Mw~195,000; DH = 98.0–98.8%) with 10% (w/w) propylene glycol (PG) provided the best balance of stretchability, durability, and low adhesion. Notably, while −25 °C is often used for cryogel preparation, freezing the gel precursor at −80 °C yielded superior results, producing materials with more open, interconnected structures and enhanced mechanical strength and elasticity—deviating from conventional practices. Conclusions: The designed cryogel prototypes exhibited functional properties comparable to or even surpassing commercial wound dressings, except for absorption capacity, which remained lower. Despite this, the cryogel prototypes demonstrated potential as wound dressings, particularly for use in dry or minimally exuding wounds. All in all, this study provides a comprehensive analysis of the physicochemical and functional properties of PVA cryogels, establishing a strong foundation for the development of advanced wound dressing systems. Full article