Pullulan hydrogels as drug release platforms in biomedicine

It is increasingly urgent to develop new therapeutic systems to combat the spreading and evolution of various pathologies globally. Nonspecific therapies and/or insufficient medication biodistribution might hinder the patient's recovery. In this sense, a targeted and controlled delivery of various biomolecules allows overcoming the limitations of conventional delivery systems, taking the user one step closer to the successful treatment of a disease. Hydrogels have been highlighted for their drug delivery abilities, particularly for their tunable properties, like hydration capacity, biodegradability, release kinetics, etc., that can be adjusted to the desired needs. Additionally, they can be produced from either natural and/or synthetic polymers, with natural-origin sources providing exceptional features like biodegradation and acceptable integration in biological systems. One of those polymers is pullulan, a biodegradable, biocompatible and hemocompatible material, with multiple uses in biomedicine. Investigations into pullulan-based hydrogels have progressively increased over the last few decades. This review addresses the uses of pullulan in biomedical engineering, emphasizing its exceptional properties for drug delivery and its processing into hydrogel systems, either in its original or derivative forms.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 PTDC/CTM-TEX/28074/2017 (POCI-01-0145-FEDER-028074) and 2C2T Strategic project UIDP/00264/2020. M.O.T. and H.P.F. also acknowledge FCT for funding PhD scholarship with reference 2021.06906.BD and auxiliary researcher contract via 2021.02720. CEEIND, respectively

Can superhydrophobic PET surfaces prevent bacterial adhesion?

Prevention of bacterial adhesion is a way to reduce and/or avoid biofilm formation, thus restraining its associated infections. The development of repellent anti-adhesive surfaces, such as superhydrophobic surfaces, can be a strategy to avoid bacterial adhesion. In this study, a polyethylene terephthalate (PET) film was modified by in situ growth of silica nanoparticles (NPs) to create a rough surface. The surface was further modified with fluorinated carbon chains to increase its hydrophobicity. The modified PET surfaces presented a pronounced superhydrophobic character, showing a water contact angle of 156° and a roughness of 104 nm (a considerable increase comparing with the 69° and 4.8 nm obtained for the untreated PET). Scanning Electron Microscopy was used to evaluate the modified surfaces morphology, further confirming its successful modification with nanoparticles. Additionally, a bacterial adhesion assay using an Escherichia coli expressing YadA, an adhesive protein from Yersinia so-called Yersinia adhesin A, was used to assess the anti-adhesive potential of the modified PET. Contrarily to what was expected, adhesion of E. coli YadA was found to increase on the modified PET surfaces, exhibiting a clear preference for the crevices. This study highlights the role of material micro topography as an important attribute when considering bacterial adhesion.This work was supported by the ViBrANT project that received funding from the EU Horizon 2020 Research and Innovation Programme under the Marie Sklowdowska-Curie, Grant agreement no 765042 and the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UIDB/04469/2020.info:eu-repo/semantics/publishedVersio

Enhancing functionalization of health care textiles with gold nanoparticle-loaded hydroxyapatite composites

Hospitals and nursing home wards are areas prone to the propagation of infections and are of particular concern regarding the spreading of dangerous viruses and multidrug-resistant bacteria (MDRB). MDRB infections comprise approximately 20% of cases in hospitals and nursing homes. Healthcare textiles, such as blankets, are ubiquitous in hospitals and nursing home wards and may be easily shared between patients/users without an adequate pre-cleaning process. Therefore, functionalizing these textiles with antimicrobial properties may considerably reduce the microbial load and prevent the propagation of infections, including MDRB. Blankets are mainly comprised of knitted cotton (CO), polyester (PES), and cotton-polyester (CO–PES). These fabrics were functionalized with novel gold-hydroxyapatite nanoparticles (AuNPs-HAp) that possess antimicrobial properties, due to the presence of the AuNPs’ amine and carboxyl groups, and low propensity to display toxicity. For optimal functionalization of the knitted fabrics, two pre-treatments, four different surfactants, and two incorporation processes were evaluated. Furthermore, exhaustion parameters (time and temperature) were subjected to a design of experiments (DoE) optimization. The concentration of AuNPs-HAp in the fabrics and their washing fastness were critical factors assessed through color difference (∆E). The best performing knitted fabric was half bleached CO, functionalized using a surfactant combination of Imerol® Jet-B (surfactant A) and Luprintol® Emulsifier PE New (surfactant D) through exhaustion at 70 ◦C for 10 min. This knitted CO displayed antibacterial properties even after 20 washing cycles, showing its potential to be used in comfort textiles within healthcare environments

Atmospheric plasma immobilization of antimicrobial Zeolite loaded silver nanoparticles on medical textiles

1. Introduction Nosocomial infections, in particular problematic chronic wounds, are a ubiquitous general concern. This apprehension was acuted by the prevalence of multidrug resistant bacteria and emergence of Pandemics. Therefore, the development of novel and highly effective antimicrobial wound dressing comprising marginal or absent cytotoxicity to the patient is crucial. Plasma plays a key role in improving the functionalization of surfaces, in particular of textiles [1]. Thus, in this work we used atmospheric double dielectric discharge (DBD) plasma activated woven polyester (PES) functionalized with silver nanoparticles (AgNPs), enzymes as antimicrobial agents, immobilized using mordenite (MOR) zeolites and polysaccharide-based matrixes to mitigate cytotoxicity. 2. Methodology and results MOR was used with the objective of improving the concentration, stability, and immobilization efficiency of AgNPs and enzymes in the functionalized fabric. Therefore, a solution combining the AgNPs, and/or antimicrobial enzymes was prepared. Afterwards, this solution was mixed with a polysaccharide matrix, consisting of alginate or chitosan. Woven PES surface was activated using DBD and was impregnated with the prepared formulation. The antimicrobial activity of the functionalized fabrics was characterized using bacteria commonly associated to nosocomial infections as well as a virus that is a potential surrogate of severe acute respiratory coronavirus 2 (SARS-COV-2). The antimicrobial tests performed comprised the evaluation of antimicrobial efficacy when in contact with the composites during 1 to 2 hours, by adapting the following standards: AATCC TM100-100 and ISO18184. The microorganisms used were S. aureus, E. coli, and bacteriophage MS2. The formulated composites containing alginate as matrix displayed a high antibacterial activity (higher than 99.999 %) which was stable for over than 15 days of storage. However, it did not exhibit any antiviral activity. The alginate composites also did not hinder the activity of protease, which may have an important antifouling activity. Whereas, the composites containing chitosan exhibited a highly effective antimicrobial activity against the bacteria and the virus (higher than 99.9999 %) when zeolite was present in the formulation

Distinct antimicrobial analysis to evaluate multi-component wound dressing performance

Wound infection hinders adequate healing, being particularly grievous and prevalent in burn wounds and chronic wounds. Wound infection extends inflammation, preventing epithelialization and angiogenesis. Therefore, infection prolongs healing time, steeply increases treatment costs and degrades patients wellbeing. One successful strategy to control wound infection is to apply an active wound dressing, able to eliminate or significantly reduce the microbial population present at the infection site. Silver nanoparticles (AgNPs) are a multipurpose antimicrobial agent with a wide scope of applications which include wound dressings. Nevertheless, several studies denote AgNPs dose-dependent cytotoxicity, and their capability to bypass the blood-brain barrier and induce a neurotoxic effect. Hence, we propose to adopt two different strategies to attempt the simultaneously immobilize and increase the load of AgNPs within the wound dressing fabric. Thus, the envisaged objective is to prevent potential systemic cytotoxicity /through immobilization and to improve its antimicrobial capability due to the higher concentration of AgNPs. Two different approaches were used: i. AgNPs were suspended in an alginate (ALG) solution, ii. AgNPs were embedded in Mordenite (MOR) zeolite, followed by the addition of an ALG solution. Both suspensions were incorporated into polyester fabric assisted by its surface activation by dielectric barrier discharge (DBD) plasma treatment. The bactericidal and virucidal effectiveness of each composite was tested against bacteria species known to induce nosocomial infections and a bacteriophage that is a potential surrogate of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Two distinct antimicrobial analyses were used to provide insights on the antimicrobial effectiveness of the obtained composites and to indirectly assess the release of AgNPs

Multicomponent wound dressing

This works describes the antimicrobial (antibacterial and antiviral) performance of a multicomponent fabric for wound dressing. The fabric comprises a scaffold of plasma activated polyester (PES), enveloped in a matrix of chitosan (CH) containing silver nanoparticles (AgNPs) and the zeolite mordenite (MOR). The antimicrobial efficacy of the cumulative addition of each of these components was evaluated.The authors would like to acknowledge the project PLASMAMED - PTDC/CTM-TEX/28295/2017 financed by FCT, FEDER and POCI in the frame of the Portugal 2020 program, the project UID/CTM/00264/2019 of 2C2T under the COMPETE and FCT/MCTES (PIDDAC) co-fnanced by FEDER through the PT2020 program

Distinct antimicrobial analysis to evaluate multi-component wound dressing performance

Wound infection hinders adequate healing, being particularly grievous and prevalent in burn wounds and chronic wounds. Wound infection extends inflammation, preventing epithelialization and angiogenesis. Therefore, infection prolongs healing time, steeply increases treatment costs and degrades patients wellbeing. One successful strategy to control wound infection is to apply an active wound dressing, able to eliminate or significantly reduce the microbial population present at the infection site. Silver nanoparticles (AgNPs) are a multipurpose antimicrobial agent with a wide scope of applications which include wound dressings. Nevertheless, several studies denote AgNPs dose-dependent cytotoxicity, and their capability to bypass the blood-brain barrier and induce a neurotoxic effect. Hence, we propose to adopt two different strategies to attempt the simultaneously immobilize and increase the load of AgNPs within the wound dressing fabric. Thus, the envisaged objective is to prevent potential systemic cytotoxicity /through immobilization and to improve its antimicrobial capability due to the higher concentration of AgNPs. Two different approaches were used: i. AgNPs were suspended in an alginate (ALG) solution, ii. AgNPs were embedded in Mordenite (MOR) zeolite, followed by the addition of an ALG solution. Both suspensions were incorporated into polyester fabric assisted by its surface activation by dielectric barrier discharge (DBD) plasma treatment. The bactericidal and virucidal effectiveness of each composite was tested against bacteria species known to induce nosocomial infections and a bacteriophage that is a potential surrogate of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Two distinct antimicrobial analyses were used to provide insights on the antimicrobial effectiveness of the obtained composites and to indirectly assess the release of AgNPs

Physical properties of an antibacterial and antiviral woven cotton functionalized with a multi-nanocomposite

[Excerpt] Introduction Wound infection is a critical factor that seriously hinders adequate healing preventing epithelialization and angiogenesis. This is particularly grievous and prevalent in burn and chronic wounds.This research was funded by FEDER funds through the Operational Competitiveness Program–COMPETE under the Project POCI-01-0247-FEDER-039733, and by National Funds through Fundação para a Ciência e Tecnologia (FCT), under the project UID/CTM/00264/2020. Liliana Melro, Rui D. V. Fernandes, and Ana Isabel Ribeiro acknowledge FCT, MCTES, FSE, and UE PhD grants 2020.04919.BD, SFRH/BD/145269/2019, SFRH/BD/137668/2018

Effects of cellulose nanofibrils on the structure and properties of poly(vinyl alcohol) electrospun nanofibers

Nanofibres of poly(vinyl alcohol) (PVA) reinforced with cellulose nanofibrils (CNFs) and/or crosslinked with maleic anhydride (MA) were produced by electrospinning technique to compare the additivation effects of the polymeric matrix. The results suggested that the PVA mass fraction equal to 14% and CNFs volumetric fraction of 3% are the best proportions for renewable base fibres production. CNFs addition allows to improve nanofibre thermal properties, which result in an eco-friendlier, biocompatible and biodegradable final product. In this study, different solutions required different operation conditions for a good membranes production and fibers with diameters between (70 to 140) nm were obtained.UID/CTM/00264/201

Characterisation of microbial attack on archaeological bone

As part of an EU funded project to investigate the factors influencing bone preservation in the archaeological record, more than 250 bones from 41 archaeological sites in five countries spanning four climatic regions were studied for diagenetic alteration. Sites were selected to cover a range of environmental conditions and archaeological contexts. Microscopic and physical (mercury intrusion porosimetry) analyses of these bones revealed that the majority (68%) had suffered microbial attack. Furthermore, significant differences were found between animal and human bone in both the state of preservation and the type of microbial attack present. These differences in preservation might result from differences in early taphonomy of the bones. © 2003 Elsevier Science Ltd. All rights reserved