The present study evaluated the effect of using electrospun polycaprolactone (PCL) as a barrier coating and black pepper oleoresin (OR) as a natural extract on the morphology, thermal, mechanical, ...antimicrobial, oxygen, and water vapor barrier properties of solvent cast gelatin (GEL). The antimicrobial activity of the developed multilayer system obtained by the so-called electrospinning coating technique was also evaluated against
strains for 10 days. The results showed that the multilayer system containing PCL and OR increased the thermal resistance, elongated the GEL film, and significantly diminished its permeance to water vapor. Active multilayer systems stored in hermetically closed bottles increased their antimicrobial activity after 10 days by inhibiting the growth of
. This study demonstrates that addition of electrospun PCL ultrathin fibers and OR improved the properties of GEL films, which promoted its potential use in active food packaging applications.
Electro-hydrodynamic processing, comprising electrospraying and electrospinning techniques, has emerged as a versatile technology to produce nanostructured fiber-based and particle-based materials. ...In this work, an antimicrobial active multilayer system comprising a commercial polyhydroxyalkanoate substrate (PHA) and an electrospun PHA coating containing in situ-stabilized silver nanoparticles (AgNPs) was successfully developed and characterized in terms of morphology, thermal, mechanical, and barrier properties. The obtained materials reduced the bacterial population of
below the detection limits at very low silver loading of 0.002 ± 0.0005 wt %. As a result, this study provides an innovative route to generate fully renewable and biodegradable materials that could prevent microbial outbreaks in food packages and food contact surfaces.
Antimicrobial resistance has been declared one of the top 10 global public health threats. Methicillin-resistant
(MRSA) is a leading cause of recurring skin and soft tissue infections in patients ...with chronic skin conditions such as diabetic foot infections, making the treatment of the ulcers challenging. Wound dressings combined with metal nanoparticles have been suggested to prevent and treat MRSA-infected wounds. However, these particles are commonly synthesized by chemical approaches. In this study, we developed bio-based silver (Bio-AgNPs) and copper oxide nanoparticles (CuONPs) polymer composites using a microbially produced polyester from the Polyhydroxyalkanoates (PHAs) family. Poly(3-hydroxyoctanoate)-
-(3-hydroxyhexanoate) (PHO) was synthesized by
and functionalized in-situ with Bio-AgNPs or ex-situ with CuONPs. PHO-CuONPs films did not inhibit MRSA growth, while a reduction of 6.0 log CFU/mL was achieved with PHO-Bio-AgNPs synthesized from silver nitrate (AgNO
) solution at 3.5 mM. Exposure of human fibroblast cells (HFF-1) to the bioactive films did not induce notable cytotoxicity and genotoxicity, as seen by a viability higher than 79% and no significant changes in basal DNA damage. However, exposure to PHO-Bio-AgNPs induced oxidative DNA damage in HFF-1 cells. No hemolytic potential was observed, while platelet aggregation was promoted and desired for wound healing. Here we demonstrate the biosynthesis of polymer-nanoparticle composites and their potential as bioactive films for MRSA treatment.
One of the major health problems linked to methicillin-resistant Staphylococcus aureus (MRSA) is severe diabetic foot ulcers (DFU), which are associated with hospital-acquired infections, lower limb ...amputations and emerging resistance to the current antibiotics. As an alternative, this work aims to develop a biodegradable and biocompatible material with antimicrobial capacity to prevent DFU. This was achieved by producing active polymeric films with metallic nanoparticles dispersed through a polycaprolactone (PCL) dressing. First, the antimicrobial activity of copper oxide nanoparticles (CuONPs) was tested by the microdilution method, selecting the lowest concentration that has an inhibitory effect on MRSA. Then, active PCL films were prepared and characterized in terms of their physicochemical properties, antimicrobial performance, cytotoxicity, genotoxicity and hemocompatibility. Active films had chemical and thermal properties like the ones without the antimicrobial agents, which was confirmed through FTIR, Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) analysis. In relation to antimicrobial activity, active PCL films inhibited MRSA growth when treated with CuONPs at a concentration of 0.07% (w/w). After exposure to the active film extracts, human foreskin fibroblast cells (ATCC® SCRC1041™) (HFF-1) exhibited a cell viability average above 80% for all treatments and no DNA damage was found. Finally, PCL films with 0.07% (w/w) CuONPs proved to be hemocompatible, and none of the films evaluated had red blood cell breakage greater than 5%, being within the acceptable limits established by the International Organization for Standardization ISO 10993-4:2002.
Highlights
The production and consumption of commodity polymers have been an indispensable part of the development of our modern society. Owing to their adjustable properties and variety of ...functions, polymer-based materials will continue playing important roles in achieving the Sustainable Development Goals (SDG)s, defined by the United Nations, in key areas such as healthcare, transport, food preservation, construction, electronics, and water management. Considering the serious environmental crisis, generated by increasing consumption of plastics, leading-edge polymers need to incorporate two types of functions: Those that directly arise from the demands of the application (e.g. selective gas and liquid permeation, actuation or charge transport) and those that enable minimization of environmental harm, e.g., through prolongation of the functional lifetime, minimization of material usage, or through predictable disintegration into non-toxic fragments. Here, we give examples of how the incorporation of a thoughtful combination of properties/functions can enhance the sustainability of plastics ranging from material design to waste management. We focus on tools to measure and reduce the negative impacts of plastics on the environment throughout their life cycle, the use of renewable sources for their synthesis, the design of biodegradable and/or recyclable materials, and the use of biotechnological strategies for enzymatic recycling of plastics that fits into a circular bioeconomy. Finally, we discuss future applications for sustainable plastics with the aim to achieve the SDGs through international cooperation.
Leading-edge polymer-based materials for consumer and advanced applications are necessary to achieve sustainable development at a global scale. It is essential to understand how sustainability can be incorporated in these materials via green chemistry, the integration of bio-based building blocks from biorefineries, circular bioeconomy strategies, and combined smart and functional capabilities.
Graphic abstract
In this work, three active bio-based multilayer structures, using a polyhydroxybutyrate-co-valerate film with a valerate content of 8 % (PHBV8) as support, were developed. To this end, a zein ...interlayer with or without cinnamaldehyde (CNMA) was directly electrospun onto one side of the PHBV8 film and the following systems were developed: (1) without an outer layer; (2) using a PHBV8 film as outer layer; and (3) using an alginate-based film as outer layer. These multilayer structures were characterized in terms of water vapour and oxygen permeabilities, transparency, intermolecular arrangement and thermal properties. The antimicrobial activity of the active bio-based multilayer systems and the release of CNMA in a food simulant were also evaluated. Results showed that the presence of different outer layers reduced the transport properties and transparency of the multilayer films. The active bio-based multilayer systems showed antibacterial activity against
Listeria monocytogenes
being the multilayer structure prepared with CNMA and PHBV outer layers (PHBV + zein/CNMA + PHBV) the one that showed the greater antibacterial activity. The release of CNMA depended on the multilayer structures, where both Fick’s and Case II transport—polymer relaxation explained the release of CNMA from the multilayer systems.
Overall, the deposition of electrospun CNMA-loaded zein fibres on a PHBV8 layer is a promising methodology for the development of active bio-based multilayer systems, with a great potential for food packaging applications.
In the Anthropocene, plastic pollution is a worldwide concern that must be tackled from different viewpoints, bringing together different areas of science. Microbial transformation of polymers is a ...broad-spectrum research topic that has become a keystone in the circular economy of fossil-based and biobased plastics. To have an open discussion about these themes, experts in the synthesis of polymers and biodegradation of lignocellulose and plastics convened within the framework of The Transnational Network for Research and Innovation in Microbial Biodiversity, Enzymes Technology and Polymer Science (MENZYPOL-NET), which was recently created by early-stage scientists from Colombia and Germany. In this context, the international workshop "Microbial Synthesis and Degradation of Polymers: Toward a Sustainable Bioeconomy" was held on 27 September 2021 via Zoom. The workshop was divided into two sections, and questions were raised for discussion with panelists and expert guests. Several key points and relevant perspectives were delivered, mainly related to (i) the microbial evolution driven by plastic pollution; (ii) the relevance of and interplay between polymer structure/composition, enzymatic mechanisms, and assessment methods in plastic biodegradation; (iii) the recycling and valorization of plastic waste; (iv) engineered plastic-degrading enzymes; (v) the impact of (micro)plastics on environmental microbiomes; (vi) the isolation of plastic-degrading (PD) microbes and design of PD microbial consortia; and (vii) the synthesis and applications of biobased plastics. Finally, research priorities from these key points were identified within the microbial, enzyme, and polymer sciences.
Antimicrobial resistance has been declared one of the top 10 global public health threats. Methicillin-resistant Staphylococcus aureus (MRSA) is a leading cause of recurring skin and soft tissue ...infections in patients with chronic skin conditions such as diabetic foot infections, making the treatment of the ulcers challenging. Wound dressings combined with metal nanoparticles have been suggested to prevent and treat MRSA-infected wounds. However, these particles are commonly synthesized by chemical approaches. In this study, we developed bio-based silver (Bio-AgNPs) and copper oxide nanoparticles (CuONPs) polymer composites using a microbially produced polyester from the Polyhydroxyalkanoates (PHAs) family. Poly(3-hydroxyoctanoate)-co-(3-hydroxyhexanoate) (PHO) was synthesized by Pseudomonas putida and functionalized in-situ with Bio-AgNPs or ex-situ with CuONPs. PHO-CuONPs films did not inhibit MRSA growth, while a reduction of 6.0 log CFU/mL was achieved with PHO-Bio-AgNPs synthesized from silver nitrate (AgNOsub.3) solution at 3.5 mM. Exposure of human fibroblast cells (HFF-1) to the bioactive films did not induce notable cytotoxicity and genotoxicity, as seen by a viability higher than 79% and no significant changes in basal DNA damage. However, exposure to PHO-Bio-AgNPs induced oxidative DNA damage in HFF-1 cells. No hemolytic potential was observed, while platelet aggregation was promoted and desired for wound healing. Here we demonstrate the biosynthesis of polymer-nanoparticle composites and their potential as bioactive films for MRSA treatment.
The development of novel bio-based materials with antimicrobial properties for active packaging applications is a topic of significant interest. The current PhD thesis deals with the development of ...biotechnologically derived polyhydroxyalkanoates (PHAs) based on nanometals for antimicrobial active food packaging applications. Initially, silver nanoparticles (AgNPs) were produced by chemical reduction and stabilized in situ within unpurified poly(hydroxybutyrate-co-hydroxyvalerate), PHBV18 (18 mol% valerate) suspensions previously obtained from mixed microbial cultures. The stabilized AgNPs were subsequently used to develop PHAs-AgNPs nanocomposites following two different strategies: 1) a direct melt-blending process where the AgNPs were added to the PHBV3 (3% mol valerate) from a highly dispersed and distributed enriched masterbatch form and, 2) as an annealed electrospun coating of PHBV3/PHBV18/AgNPs over compression molded PHBV3. The implementation of both strategies resulted in active nanocomposites with strong antimicrobial activity against food-borne pathogens, being the electrospinning coating technique the most efficient one in reducing the bacterial and virus population, even at very low AgNPs loading (from 0.002 to 0.04% wt.).
As an alternative route, an integrated bioprocess for the biological synthesis of AgNPs and polyhydroxybutyrate (PHB) from the fermentation process with Cupriavidus necator was also carried out. Interestingly, this work demonstrated for the first time, the inherent capacity of C. necator to reduce silver nitrate and produce AgNPs without the need for adding a reducing agent. The process was successfully optimized and scaled-up to a fully automated 10 liters bioreactor.
Finally, because of the limitations of the use of AgNPs in food applications, antimicrobial PHAs films based on zinc oxide (ZnO) and copper oxide (CuO) nanoparticles were prepared according to the previously developed strategies but in this case, a melt-mixing process of preincorporated ZnO into unpurified PHBV18 fiber mats made by electrospinning was also carried out to stabilize the metal nanoparticles. The effect of ZnO nanoparticles morphology and the method of ZnO/CuO incorporation on the morphological, optical, thermal, mechanical and barrier properties of the resulting active films as well as their influence on the antimicrobial (bactericide and virucidal) performance were studied.
Thus, this PhD thesis represents a significant step forward in the understanding of the antimicrobial efficacy of highly dispersed and distributed nanometals and highlights the suitability of the developed PHAs/nanometals materials for antimicrobial applications and in particular for antimicrobial active food packaging applications.
El desarrollo de nuevos biomateriales con propiedades antimicrobianas para aplicaciones de envasado activo resulta un tema de gran interés en la actualidad. La presente tesis doctoral estudia el desarrollo por vía biotecnológica de polihidroxialcanoatos (PHAs) conteniendo nanometales para aplicaciones de envasado activo antimicrobiano de alimentos. En primer lugar, se produjeron nanopartículas de plata (AgNPs) por reducción química y se estabilizaron in situ en una suspensión de poli (hidroxibutirato-co-hidroxivalerato) no purificado, PHBV18 (18% en moles de valerato), obtenido previamente a partir de cultivos mixtos microbianos. Posteriormente, las AgNPs estabilizadas se utilizaron para desarrollar nanocompuestos de PHAs-AgNPs siguiendo dos estrategias diferentes: 1) un proceso de mezclado-fundido en donde las AgNPs se añadieron al PHBV3 (3% mol de valerato) a partir de un masterbatch de nanopartículas altamente dispersas y distribuidas y, 2) como una estructura bicapa formada por un recubrimiento a base de PHBV/PHBV18/AgNPs depositado sobre un film de PHBV3 obtenido por moldeo por compresión. La aplicación de ambas estrategias dio lugar a nanocompuestos activos con una fuerte actividad antimicrobiana frente a patógenos transmitidos por los alimentos, siendo la estructura bicapa la más eficaz en la reducción de la población bacteriana y viral, incluso a una carga muy baja de AgNPs (de 0.002 a 0.04% en peso).
Como ruta alternativa, también se llevó a cabo un proceso integrado de fermentación con Cupriavidus necator para la síntesis biológica de AgNPs y polihidroxibutirato (PHB). En este trabajo se demostró, por primera vez, la capacidad inherente de C. necator para reducir nitrato de plata y producir AgNPs sin la necesidad de añadir un agente reductor. El proceso fue optimizado y escalado satisfactoriamente a un biorreactor automatizado de 10 litros.
Finalmente, debido a las limitaciones del uso de AgNPs en aplicaciones alimentarias, se prepararon films antimicrobianos de PHAs basados en nanopartículas de óxido de zinc (ZnO) y óxido de cobre (CuO) de acuerdo con las estrategias previamente desarrolladas. Adicionalmente, ambas estrategias se compararon con una tercera basada en la preincorporación de ZnO en fibras de PHBV18 no purificado y su posterior mezclado-fundido con polímero virgen. Se estudió el efecto de la morfología de las nanopartículas de ZnO y del método de incorporación de ZnO/CuO sobre las propiedades morfológicas, ópticas, térmicas, mecánicas y de barrera de los films activos resultantes, así como su influencia en el comportamiento antimicrobiano (bactericida y virucida).
Por lo tanto, esta tesis doctoral representa un avance significativo en la comprensión de la eficacia antimicrobiana de nanometales altamente dispersos y distribuidos y destaca la idoneidad de los materiales desarrollados a base de PHAs y nanometales para aplicaciones antimicrobianas y, en particular, para aplicaciones de envasado de alimentos activos antimicrobianos.
El desenvolupament de nous materials d'origen biològic amb propietats antimicrobianes per a aplicacions d'envasament actiu és un tema d'interès significatiu. La tesi doctoral actual s'ocupa del desenvolupament de polihidroxialcanoats (PHA) reforçats amb nanometals per via biotecnològicament per a aplicacions d'envasat actiu antimicrobià d'aliments. Inicialment, les nanopartícules de plata (AgNPs) van ser produïdes per reducció química i estabilitzades in situ dins en suspensions de poli (hidroxibutirato-co-hidroxivalerato) sense purificar, PHBV18 (18 mol% de valerat), prèviament obtinguts a partir de cultius mixtes microbians. Las AgNPs estabilitzades es van usar posteriorment per a desenvolupar nanocompostos de PHA's- AgNPs seguint dues estratègies diferents: 1) Procés directe de barreja en fusió que no utilitza dissolvents orgànics o estabilitzants addicionals i on es van afegir les AgNPs al PHBV3 (3% mol valerato) a partir d¿un masterbath on estaven perfectament disperses i distribuïdes 2) com una estructura bicapa formada per un recobriment de PHBV3 / PHBV18/AgNPS que es deposita sobre un film de PHBV3 obtingut per modelat per compressió. L'aplicació d'ambdues estratègies va donar lloc a nanocompostos actius amb una forta activitat antibacteriana enfront de patògens transmesos pels aliments, sent l'estructura de doble capa la més eficaç en la reducció de la població bacteriana i viral, fins i tot a una càrrega molt baixa de AgNPs (de 0.002-0.04% en pes).
Com ruta alternativa, també es va dur a terme un procés integrat de fermentació amb Cupriavidus necator per a la síntesi biològica de AgNPs i polihidroxibutirato (PHB). En aquest treball es demostra, per primera vegada, la capacitat inherent de C. necator per reduir la sal de plata i produir AgNPs sense la necessitat d'afegir un agent reductor. El procés va ser optimitzat i escalat satisfactòriament a un bioreactor de 10 litres.
Finalment, a causa de les limitacions de l'ús de nanopartícules de plata en aplicacions alimentàries, es van preparar films antimicrobians de PHA que incorporessin nanopartícules d'òxid de zinc (ZnO) i òxid de coure (CuO) d'acord amb les estratègies prèviament desenvolupades. Les dues estratègies es van comparar amb una tercera basada en la preincorporació de ZnO en fibres de PHBV18 no purificat i aquestes fibres es van barrejar posteriorment amb polímer verge. Es va estudiar l'efecte de la morfologia de les nanopartícules de ZnO i el mètode de la incorporació de ZnO/CuO sobre les propietats morfològiques, òptiques, tèrmiques, mecàniques i de barrera dels films actius resultants, així com la seva influència en el comportament antimicrobià (bactericida i virucida).
Per tant, aquesta tesi doctoral representa un pas endavant significatiu en la comprensió de l'eficàcia antimicrobiana de nanometales altament dispersos i distribuïts i posa en relleu la idoneïtat dels materials desenvolupats basats en PHAs i nanometals per a aplicacions antimicrobianes i, en particular, per a aplicacions d'envasat d'aliments actius antimicrobians.
Castro Mayorga, JL. (2017). Biotechnological routes for the development of antimicrobial nano-metal based polyhydroxyalkanoates for active food packaging applications Tesis doctoral no publicada. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/85678
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