Thermo-mechanical performance of nanostructured electrospun composites produced from poly(vinyl alcohol) and cellulosic compounds for potential uses as wound dressings

The purpose of this research was to analyze the morphology, thermal and mechanical properties of poly(vinyl alcohol) (PVA)-based electrospun mats reinforced with cellulose acetate (CA) or cellulose nanocrystalline (CNC) for potential applications in wound dressings. Bead-free and water-stable electrospun nanofibers made of blends of PVA and CA or CNC were successfully produced and crosslinked with glutaraldehyde vapor. Crosslinking slightly increased the nanofibers’ diameters in order of 43 and 13% for 80/20 PVA/CA and PVA/CNC electrospun mats, respectively, while maintaining their bead-free morphology. Thermogravimetry (TGA) and differential scanning calorimetry (DSC) evaluations were employed to determine the miscibility and the thermal response of the uncrosslinked and crosslinked mats, reporting a reduction in mass loss upon addition of CA and CNC and upon crosslinking process. Polymers’ powder and mats (before and after crosslinking) crystallinity was assessed by X-ray diffraction analysis (XRD). Crosslinked mats experienced a slight reduction in crystallinity compared to the uncrosslinked. Static and dynamic tensile strength tests revealed that CA and CNC doped mats enhanced the Young's modulus and lowered deformation at failure compared to pristine PVA electrospun mats. Data from storage modulus (E’) demonstrated the strength of the physical interactions formed between PVA and the cellulosic derivatives (either before and after crosslinking), highlighting the stiffness of CA (231.58 MPa for the 80/20 mat) and, particularly, CNC (742.04 MPa for the 80/20 mat). This research uncovered important information concerning the chemical and physical relation between polymeric matrices and additives, essential for the proper selection of materials for wound dressings production.Authors acknowledge the Portuguese Foundation for Science and Technology (FCT), FEDER funds by means of Portugal 2020 Competitive Factors Operational Program (POCI) and the Portuguese Government (OE) for funding the project with reference PTDC/CTM-TEX/28074/2017 (POCI-01-0145-FEDER-028074). Authors also acknowledge project UIDP/00264/2020 of Centre for Textile Science and Technology (2C2T), funded by national funds through FCT/MCTES. M.A.T., D.P.F and H.P.F. also acknowledge FCT for PhD scholarship (SFRH/BD/148930/2019) and junior (CEECIND/02803/2017) and auxiliary researcher (2021.02720.CEECIND) contracts, respectively

Antimicrobial action and clotting time of thin, hydrated poly(Vinyl Alcohol)/cellulose acetate films functionalized with LL37 for prospective wound-healing applications

Poly(vinyl alcohol)/cellulose acetate (PVA/CA) films were prepared via a new method that combines principles from solvent casting and phase inversion. To guarantee some degree of flexibility, films were produced with a higher percentage of PVA compared to CA, from 90/10 to 50/50. The antimicrobial peptide (AMP) LL37 was then anchored using dopamine as a binding agent. Films were characterized in terms of functional groups, thermal stability, tensile strength, porosity, swelling and degradation (stability in physiological media at different pHs). The antimicrobial performance of LL37 surface-modified films was tested against Staphylococcus aureus, Staphylococcus epidermidis and Escherichia coli in dynamic environment and in the presence and absence of an albumin interface. LL37 treated films demonstrated great antibacterial efficacy against the three kinds of bacteria, ≈ 75% inhibition for S. aureus, ≈ 85% for S. epidermidis and ≈ 60% for E. coli, regardless of PVA/CA ratio. Presence of albumin reduced bacteria inhibition in all tested groups, most likely due to the binding of the protein molecules to the antimicrobial agents, reducing the free fraction available for bacterial killing. Films treated with LL37 accelerated clotting time (≈ 10 min) above vancomycin and bare surfaces, demonstrating great capacity to activate the intrinsic coagulation cascade.Portuguese Foundation for Science and Technology (FCT), FEDER funds by means of Portugal 2020 Competitive Factors Operational Program (POCI) and the Portuguese Government (OE) for funding the project PEPTEX with reference POCI-01-0145-FEDER-028074. Authors also acknowledge project UID/CTM/00264/2019 of Centre for Textile Science and Technology (2C2T), funded by national funds through FCT/MCTE

Eugenol-containing essential oils loaded onto Chitosan/Polyvinyl alcohol blended films and their ability to eradicate Staphylococcus aureus or Pseudomonas aeruginosa from infected microenvironments

Chronic wounds (CW) create numerous entryways for pathogen invasion and prosperity, further damaging host tissue and hindering its remodeling and repair. Essential oils (EOs) exert quick and efficient antimicrobial (AM) action, unlikely to induce bacterial resistance. Cinnamon leaf and clove oils (CLO and CO) display strong AM activity, namely against Staphylococcus aureus and Pseudomonas aeruginosa. Chitosan (CS) is a natural and biodegradable cationic polysaccharide, also widely known for its AM features. CS and poly (vinyl alcohol) (PVA) films were prepared (ratio 30/70 w/w; 9 wt%) by the solvent casting and phase inversion method. The film's thermal stability and chemical composition data reinforced polymer blending and EO entrapment. Films were supplemented with 1 and 10 wt% of EO in relation to total polymeric mass. The film thickness and degree of swelling (DS) tended to increase with EO content, particularly with 10 wt % CLO (* p < 0.05). UV-visible absorbance scans in the 250-320 cm-1 region confirmed the successful uptake of CLO and CO into CS/PVA films, particularly with films loaded with 10 wt% EO that contained 5.30/5.32 times more CLO/CO than films supplemented with 1 wt% EO. AM testing revealed that CS films alone were effective against both bacteria and capable of eradicating all P. aeruginosa within the hour (*** p < 0.001). Still, loaded CS/PVA films showed significantly improved AM traits in relation to unloaded films within 2 h of contact. This study is a first proof of concept that CLO and CO can be dispersed into CS/PVA films and show bactericidal effects, particularly against S. aureus, this way paving the way for efficient CW therapeutics.Portuguese Foundation for Science and Technol-ogy (FCT), FEDER funds by means of Portugal 2020 Competitive Factors Operational Program(POCI), and the Portuguese Government (OE) for funding the project PEPTEX with reference PTDC/CTM-TEX/28074/2017 (POCI-01-0145-FEDER-028074). The authors also acknowledge project UID/CTM/00264/2021 of the Centre for Textile Science and Technology (2C2T), funded by nationalfunds through FCT/MCTES. The authors also thankÂngela Silva for performing STA and DSCmeasurements and assisting with enthalpy calculations and FTIR set-up, Eng. Joaquim Jorge Peixotofor showing us how to use the film thickness meter, as well as to Eng. Paulo Madureira from IsazaScientific for clarifications regarding the employed UV-visible spectroscopy metho

Flexible, biodegradable LL37-anchored poly(vinyl alcohol)/cellulose acetate films for enhanced infection control

Wound care is a growing industry that lately has been facing multiple challenges due to the increasing health care costs, aging of population, appearance of antibiotic-resistant pathogens, and rise in the incidence of chronic diseases. Unlike acute wounds which heal in a predictable amount of time following the stages of healing, chronic wounds (CW) often fail to progress past the inflammatory phase, increasing costs and healing time. Bioactive dressings that incorporate drugs/antibiotics or bioactive molecules in their formulation have been suggested as alternatives to the conventional gauzes and foams. Here, we propose the combination of poly(vinyl alcohol) (PVA) and cellulose acetate (CA), both biodegradable and biocompatible polymers, for the production of films processed via a new method that combines principles from solvent casting and phase inversion, and modified with the antimicrobial peptide (AMP) LL37, as a new active solution. To guarantee some degree of flexibility, films were produced with a higher percentage of PVA compared to CA, from 90/10 to 50/50. LL37 was then anchored using dopamine as a binding agent. Films were characterized in terms of functional groups, thermal stability, tensile strength, porosity, swelling and degradation rate. The antimicrobial performance of LL37 surface-modified films was tested against Staphylococcus aureus, Staphylococcus epidermidis and Escherichia coli in dynamic environment. LL37-modified films demonstrated great antibacterial efficacy against the three bacteria, ≈ 75% inhibition for S. aureus, ≈ 85% for S. epidermidis and ≈ 60% for E. coli, regardless of PVA/CA ratio. Films treated with LL37 accelerated clotting time (≈ 10 min) above vancomycin and bare surfaces, demonstrating great capacity to activate the intrinsic coagulation cascade. In the end, the potential of LL37 functionalized PVA/CA films for prospective wound-healing applications was demonstrated

Escolas transformadoras: Colaboração, transformação e políticas educativas em educação para a cidadania global

O projeto Escolas Transformadoras, levado a cabo por uma Organização Não Governamental para o Desenvolvimento e três Instituições do Ensino Superior, pretendeu refletir sobre os desafios colocados à Escola na construção de uma dimensão de cidadania consciente e crítica nos/as alunos/as com vista à transformação de todas as formas de injustiça social, ou seja, uma escola transformadora. O projeto privilegiou um processo de trabalho colaborativo entre pares, no qual as/os docentes aprendem entre pares e com os/as estudantes, numa partilha de saberes que lhes permite reconfigurar-se, transformar(-se) e ampliar o conjunto das suas competências, fomentando o seu desenvolvimento pessoal e profissional ao mesmo tempo que se constituem como agentes transformadores da escola e da comunidade. Neste artigo pretende-se sistematizar as reflexões e aprendizagens realizadas no âmbito do projeto, a partir da categoria de análise da colaboração enquanto motor de transformação e resposta política em si mesma. Podemos afirmar que as práticas desenvolvidas, como a monitorização e avaliação das ações através da reflexão conjunta, se traduzem na melhoria das ações e do processo de trabalho da equip

Tecnologias inovadoras do cuidado em enfermagem

Objective: to reflect about the conceptualization of technology as a field of knowledge in nursing, as well as the production of technologies in the area. Methodology: it is a theoretical reflection. Results: historically, the conception of technology is used as a product or an equipment, however, it also includes knowledge to generate and use products and organizate of human relations. The knowledge of Nursing consists of techniques and technologies produced in its praxis, as: Technologies of Nursing Care and Educational Technologies. Conclusion: however, there emerges the need to (re) to discuss the relations between technologies in nursing to contemplate the thought technology in its ambivalenceObjetivo: reflexionar sobre la conceptualización de la tecnología como un campo del conocimiento en enfermería, así como la producción de tecnologías en el área. Metodología: se trata de una reflexión teórica. Resultados: históricamente, la concepción de la tecnología es utilizada como un producto o material, sin embargo, también incluye los conocimientos para la generación y uso de los productos y la organización de las relaciones humanas. El conocimiento de Enfermería consiste en técnicas y tecnologías producidas en su praxis, como: Tecnologías de los Cuidados de Enfermería y Tecnologías Educativas. Conclusión: sin embargo, surge la necesidad de (re) discutir las relaciones entre las tecnologías en la enfermería para contemplar el pensamiento tecnológico en su ambivalencia.Objetivo: refletir acerca da conceituação de tecnologia como campo do saber de enfermagem, bem como a produção de tecnologias na área. Metodologia: Trata-se de uma reflexão teórica. Resultados: Historicamente, a concepção de tecnologia é utilizada como um produto ou equipamento, entretanto, ela também compreende saberes para geração e utilização de produtos e organização das relações humanas. O saber de Enfermagem é constituído por técnicas e tecnologias produzidas em sua práxis, como: Tecnologias do Cuidado em Enfermagem e Tecnologias Educacionais. Conclusão: Contudo, emerge a necessidade de (re) discutir as relações entre tecnologias na enfermagem para contemplar o pensamento tecnológico em sua ambivalência

Potencialities of electrospun mats based on PVA/CA for applications as chronic wound dressings

Chronic wounds are unable to follow the normal healing steps, taking more than 12 weeks to heal They are characterized by a defective matrix and cell debris impair healing, prolonged inflammation, moisture imbalance and high bacteria amounts Bacterial infections are the main cause behind complications with the healing of chronic wounds. Biodegradable polymeric wound dressings were engineered by electrospinning with a porous fibrous nanostruture resembling the extracellular matrix The goal was to generate dressings with thin fiber diameters that, in the future, will be functionalized with antimicrobial peptides ( with immunoregulatory properties, to prevent bacterial colonization and fight infection.PTDC/CTM-TEX/28074/2017 ; UID/CTM/0026

On the mechanical characterization of bovine bone tissue under compressive loading

This study reveals a pioneer characterization of bovine trabecular bone tissue under dynamic compressive loading in the range of 20-140 oC, within physiological loading frequencies (1-20 Hz). The presented results demonstrate that the viscous behaviour in compression mode up to 140 oC is regulated by the collagen viscoelastic properties, showing three frequency-independent main peaks in tanδ and loss modulus at 75, 100, and 130 oC. The referred peaks are, respectively, related to crystalline structure breakdown, water structural evaporation, and the glass transition temperature (Tg) of collagen. At these low frequencies, the system is governed by a frequency-dependent elastic response and a frequency- independent energy dissipation. However, an additional experimental test at physiological temperature (37 oC), in the range of 10-200 Hz, has shown that bone trabecular tissue submitted to compressive loading at higher frequencies is ruled by a frequency-dependent behaviour of the viscous component

Effects of antimicrobial peptides on bacteria and viruses

[Excerpt] For many years, antibiotics have been the most widely used antimicrobial agents to fight infections. However, their excessive consumption has led to an alarmingly high development of resistance by microbial pathogens, raising a serious global, public-health problem (Felgueiras 2021, Lewies et al. 2019, Rončević et al. 2019). Hence, the growing search for alternatives to these agents. In recent years, antimicrobial peptides (AMPs) have been the focus of great interest since they are the most widespread and evolutionarily conserved components of the innate immune system, acting as a primary line of host defense against microbial infections (Magana et al. 2020)

New method to produce poly(vinyl alcohol)/cellulose acetate films with improved antibacterial action

New alternatives to the conventional wound dressings are being engineered. Here, we propose the processing of two biodegradable polymers, poly(vinyl alcohol) (PVA) and cellulose acetate (CA), in the form of films via a new method that combines principles of solvent casting and phase-inversion. Highly flexible and mechanically resistant films were obtained. PVA/CA films were then treated with the antibiotic vancomycin via two methods, blending and physisorption (via dopamine). Immobilization of vancomycin was proven efficient in promoting the films' antibacterial action against Staphylococcus epidermidis bacteria. Data demonstrates the potentialities of PVA/CA films for prospective wound healing applications.Authors acknowledge the Portuguese Foundation for Science and Technology (FCT), FEDER funds by means of Portugal 2020 Competitive Factors Operational Program (POCI) and the Portuguese Government (OE) for funding the project PEPTEX with reference POCI-01-0145-FEDER-028074. Authors also acknowledge project UID/CTM/00264/2019 of Centre for Textile Science and Technology (2C2T), funded by national funds through FCT/MCTE