Long-term antimicrobial effect of nisin released from electrospun triaxial fiber membranes

Dual-Mode Release of IL-4 and TCP from a PGA-SF Core-Shell Electrospinning Scaffold for Enhanced Bone Regeneration through Synergistic Immunoregulation and Osteogenesis

The successful filling of bone defects remains challenging due to the incongruity between bone graft materials and the dynamic process of bone healing. Developing multifunctional materials matching the dynamic process of bone healing offers a viable solution to the current dilemma. Lines of evidence have shown that engineering osteoimmunomodulatory biomaterials can modulate the function of immune cells and thus promote bone regeneration. Herein, we utilized silk fibroin (SF) and polyglycolic acid (PGA) to create a PGA-SF core-shell fibrous scaffold, incorporating interleukin-4 (IL-4) and tricalcium phosphate (TCP) as a codelivery system (PGA/TCP-SF/IL-4), aiming to achieve an initial rapid release of IL-4 and sustained release of TCP. The PGA/TCP-SF/IL-4 scaffold mimicked the native bone structure and showed superior tenacity in the wetting regime. In vitro studies demonstrated that the PGA/TCP-SF/IL-4 scaffold significantly reduced the inflammatory response by upregulating the M2 macrophages, created a favorable microenvironment for osteogenesis, and facilitated osteogenic differentiation and mineralization. Implantation of the PGA/TCP-SF/IL-4 scaffold into the rat skull defect model notably increased the formation of new bones. IL-4 and TCP acted synergistically in attenuating inflammation and enhancing osteogenic differentiation. Overall, this multifunctional scaffold comprehensively considers the various demands in the bone defect region, which might have a significant potential for application in bone reconstruction.

Temperature-sensitive poly(N-isopropylacrylamide)/polylactic acid/lemon essential oil nanofiber films prepared via different electrospinning processes: Controlled release and preservation effect

To develop an optimized controlled-release system based on temperature-sensitive poly(N-isopropylacrylamide) (PNIPAAm) nanofibers, we prepared three types of temperature-controlled preservative films. These films were composed of PNIPAAm, polyvinyl alcohol (PVA), polylactic acid (PLA), and lemon essential oil (LEO), and were fabricated using uniaxial, coaxial, and layered spinning techniques. The nanofiber films obtained by layered spinning exhibited a sandwich structure, demonstrating superior physical barrier properties, mechanical strength, and thermal resistance. Fourier-transform infrared spectroscopy confirmed the hydrogen bonding interaction between the polylactic acid/lemon essential oil and PNIPAAm layers. LEO release tests showed that PNIPAAm functions as a temperature-responsive switch, suppressing LEO release below and promoting it above the critical solution temperature. After a sustained release at 40 °C for 5 days, the layered film maintained significant antibacterial activity, effectively extending the shelf life of blackberries to 4 days. Considering its physical barrier, mechanical, and sustained-release properties, the layered film derived from PNIPAAm shows great potential as an intelligent temperature-controlled cling film to effectively extend the freshness of perishable products.

Advances in Transdermal Delivery of Antimicrobial Peptides for Wound Management: Biomaterial-Based Approaches and Future Perspectives

Antimicrobial peptides (AMPs), distinguished by their cationic and amphiphilic nature, represent a critical frontier in the battle against antimicrobial resistance due to their potent antimicrobial activity and a broad spectrum of action. However, the clinical translation of AMPs faces hurdles, including their susceptibility to degradation, limited bioavailability, and the need for targeted delivery. Transdermal delivery has immense potential for optimizing AMP administration for wound management. Leveraging the skin's accessibility and barrier properties, transdermal delivery offers a noninvasive approach that can circumvent systemic side effects and ensure sustained release. Biomaterial-based delivery systems, encompassing nanofibers, hydrogels, nanoparticles, and liposomes, have emerged as key players in enhancing the efficacy of transdermal AMP delivery. These biomaterial carriers not only shield AMPs from enzymatic degradation but also provide controlled release mechanisms, thereby elevating stability and bioavailability. The synergistic interaction between the transdermal approach and biomaterial-facilitated formulations presents a promising strategy to overcome the multifaceted challenges associated with AMP delivery. Integrating advanced technologies and personalized medicine, this convergence allows the reimagining of wound care. This review amalgamates insights to propose a pathway where AMPs, transdermal delivery, and biomaterial innovation harmonize for effective wound management.

Electrospinning technologies for the delivery of Biopharmaceuticals: Current status and future trends

This review provides an in-depth exploration of electrospinning techniques employed to produce micro- or nanofibres of biopharmaceuticals using polymeric solutions or melts with high-voltage electricity. Distinct from prior reviews, the current work narrows its focus on the recent developments and advanced applications in biopharmaceutical formulations. It begins with an overview of electrospinning principles, covering both solution and melt modes. Various methods for incorporating biopharmaceuticals into electrospun fibres, such as surface adsorption, blending, emulsion, co-axial, and high-throughput electrospinning, are elaborated. The review also surveys a wide array of biopharmaceuticals formulated through electrospinning, thereby identifying both opportunities and challenges in this emerging field. Moreover, it outlines the analytical techniques for characterizing electrospun fibres and discusses the legal and regulatory requirements for their production. This work aims to offer valuable insights into the evolving realm of electrospun biopharmaceutical delivery systems.

Fibrous matrices facilitate pleurocidin killing of wound associated bacterial pathogens

Conventional wound infection treatments neither actively promote wound healing nor address the growing problem of antibacterial resistance. Antimicrobial peptides (AMPs) are natural defense molecules, released from host cells, which may be rapidly bactericidal, modulate host-immune responses, and/or act as endogenous mediators for wound healing. However, their routine clinical use has hitherto been hindered due to their instability in the wound environment. Here we describe an electrospun carrier system for topical application of pleurocidin, demonstrating sufficient AMP release from matrices to kill wound-associated pathogens including Acinetobacter baumannii and Pseudomonas aeruginosa. Pleurocidin can be incorporated into polyvinyl alcohol (PVA) fiber matrices, using coaxial electrospinning, without major drug loss with a peptide content of 0.7% w/w predicted sufficient to kill most wound associated species. Pleurocidin retains its activity on release from the electrospun fiber matrix and completely inhibits growth of two strains of A. baumannii (AYE; ATCC 17978) and other ESKAPE pathogens. Inhibition of P. aeruginosa strains (PAO1; NCTC 13437) is, however, matrix weight per volume dependent, with only larger/thicker matrices maintaining complete inhibition. The resulting estimation of pleurocidin release from the matrix reveals high efficiency, facilitating a greater AMP potency. Wound matrices are often applied in parallel or sequentially with the use of standard wound care with biocides, therefore the presence and effect of biocides on pleurocidin potency was tested. It was revealed that combinations displayed additive or modestly synergistic effects depending on the biocide and pathogens which should be considered during the therapy. Taken together, we show that electrospun, pleurocidin-loaded wound matrices have potential to be investigated for wound infection treatment.

Co- and Triaxial Electrospinning for Stem Cell-based Bone Regeneration

Bone tissue is composed of organic minerals and cells. It has the capacity to heal for certain minor damages, but when the bone defects surpass the critical threshold, they need fixing. Bone regeneration through natural and synthetic biodegradable materials requires various steps, such as manufacturing methods and materials selection. A successful biodegradable bone graft should have a high surface area/ volume ratio, strength, and a biocompatible, porous structure capable of promoting cell adhesion, proliferation, and differentiation. Considering these requirements, the electrospinning technique is promising for creating functional nano-sized scaffolds. The multi-axial methods, such as coaxial and triaxial electrospinning, are the most popular techniques to produce double or tri-layered scaffolds, respectively. Recently, stem cell culture on scaffolds and the application of osteogenic differentiation protocols on these scaffolds have opened new possibilities in the field of biomaterials research. This review discusses an overview of the progress in coaxial and triaxial technology through biodegradable composite bone materials. The review also carefully elaborates the osteogenic differentiation using stem cells and their performance with nano-sized scaffolds.

Mimicked Spinal Cord Fibers Trigger Axonal Regeneration and Remyelination after Injury

Spinal cord injury (SCI) causes tissue structure damage and composition changes of the neural parenchyma, resulting in severe consequences for spinal cord function. Mimicking the components and microstructure of spinal cord tissues holds promise for restoring the regenerative microenvironment after SCI. Here, we have utilized electrospinning technology to develop aligned decellularized spinal cord fibers (A-DSCF) without requiring synthetic polymers or organic solvents. A-DSCF preserves multiple types of spinal cord extracellular matrix proteins and forms a parallel-oriented structure. Compared to aligned collagen fibers (A-CF), A-DSCF exhibits stronger mechanical properties, improved enzymatic stability, and superior functionality in the adhesion, proliferation, axonal extension, and myelination of differentiated neural progenitor cells (NPCs). Notably, axon extension or myelination has been primarily linked to Agrin (AGRN), Laminin (LN), or Collagen type IV (COL IV) proteins in A-DSCF. When transplanted into rats with complete SCI, A-DSCF loaded with NPCs improves the survival, maturation, axon regeneration, and motor function of the SCI rats. These findings highlight the potential of structurally and compositionally biomimetic scaffolds to promote axonal extension and remyelination after SCI.

Highly active nisin coated polycaprolactone electrospun fibers against both Staphylococcus aureus and Pseudomonas aeruginosa

In this study, a wound dressing of electrospun polycaprolactone (PCL) fibers incorporating the antimicrobial peptide (AMP) nisin was fabricated. Nisin was physically adsorbed to the PCL fibers and tested for antibacterial activity against both Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa). The PCL fibers had an average diameter of 1.16 μm ± 0.42 μm and no significant change in diameter occurred after nisin adsorption. X-ray photoelectron spectroscopy (XPS) analysis of the fibers detected nitrogen indicative of adsorbed nisin and the signal was used to quantify the levels of coverage on the fiber surfaces. In vitro nisin release studies showed a burst release profile with 80 % of the nisin being released from the fibers within 30 min. Air plasma pre-treatment of the PCL fibers to render them hydrophilic improved nisin loading and release. Antibacterial testing was performed using minimum inhibitory concentration (MIC) and surface attachment assays. The released nisin remained active against both Gram positive S. aureus and Gram negative P. aeruginosa, which has previously been difficult to achieve with single polymer fiber systems. Mammalian cell culture of the nisin coated fibers with L-929 mouse fibroblasts and human epidermal keratinocytes (HEKa) showed that the nisin did not have a significant effect on the biocompatibility of the PCL fibers. The results presented here demonstrate that the physical adsorption, which is a post-treatment, overcomes the potential limitations of harsh chemicals and fabrication conditions of electrospinning from organic solvents and provides a drug loading system having effective antibacterial properties in wound dressings.

The Application of Nano-drug Delivery System With Sequential Drug Release Strategies in Cancer Therapy

Currently, multidrug combinations are often used clinically to improve the efficacy of oncology chemotherapy, but multidrug combinations often lead to multidrug resistance and decreased performance, resulting in more severe side effects than monotherapy. Therefore, sequential drug release strategies in time and space as well as nano-carriers that respond to the tumor microenvironment have been developed. First, the advantage of the sequential release strategy is that they can load multiple drugs simultaneously to meet their spatiotemporal requirements and stability, thus exerting synergistic effects of two or more drugs. Second, in some cases, sequential drug delivery of different molecular targets can improve the sensitivity of cancer cells to drugs. Control the metabolism of cancer cells, and remodel tumor vasculature. Finally, some drug combinations with built-in release control are used for sequential administration. This paper focuses on the use of nanotechnology and built-in control device to construct drug delivery carriers with different stimulation responses, thus achieving the sequential release of drugs. Therefore, the nano-sequential delivery carrier provides a new idea and platform for the therapeutic effect of various drugs and the synergistic effect among drugs.

Electrospun Nanofiber Membranes with Various Structures for Wound Dressing

Electrospun nanofiber membranes (NFMs) have high porosity and a large specific surface area, which provide a suitable environment for the complex and dynamic wound healing process and a large number of sites for carrying wound healing factors. Further, the design of the nanofiber structure can imitate the structure of the human dermis, similar to the natural extracellular matrix, which better promotes the hemostasis, anti-inflammatory and healing of wounds. Therefore, it has been widely studied in the field of wound dressing. This review article overviews the development of electrospinning technology and the application of electrospun nanofibers in wound dressings. It begins with an introduction to the history, working principles, and transformation of electrospinning, with a focus on the selection of electrospun nanofiber materials, incorporation of functional therapeutic factors, and structural design of nanofibers and nanofiber membranes. Moreover, the wide application of electrospun NFMs containing therapeutic factors in wound healing is classified based on their special functions, such as hemostasis, antibacterial and cell proliferation promotion. This article also highlights the structural design of electrospun nanofibers in wound dressing, including porous structures, bead structures, core-shell structures, ordered structures, and multilayer nanofiber membrane structures. Finally, their advantages and limitations are discussed, and the challenges faced in their application for wound dressings are analyzed to promote further research in this field.

Electrospinning in personal protective equipment for healthcare work

Protection in many service areas is mandatory for good performance in daily activities of workers, especially health areas. Personal protective equipment (PPE) is used to protect patients and health workers from contamination by harmful pathogens and body fluids during clinical attendance. The pandemic scenario caused by SARS-CoV-2 has shown that the world is not prepared to face global disease outbreaks, especially when it comes to the PPE of healthcare workers. In the last years, the world has faced a deficiency in the development of advanced technologies to produce high-quality PPE to attend to the exponential increasing demand. Electrospinning is a technology that can be used to produce high-quality PPE by improving the protective action of clothing. In the face of this concern, this manuscript presents as focus the potential of electrospinning to be applied in protective clothing. PPE mostly used by healthcare workers are also presented. The physico-chemical characteristics and production processes of medical textiles for PPE are addressed. Furthermore, an overview of the electrospinning technique is shown. It is important to highlight most research about electrospinning applied to PPE for health areas presents gaps and challenges; thus, future projections are also addressed in this manuscript.

Polymeric nanomaterial strategies to encapsulate and deliver biological drugs: points to consider between methods

Biological drugs (BDs) play an increasingly irreplaceable role in treating various diseases such as cancer, and cardiovascular and neurodegenerative diseases. The market share of BDs is increasingly promising. However, the effectiveness of BDs is currently limited due to challenges in efficient administration and delivery, and issues with stability and degradation. Thus, the field is using nanotechnology to overcome these limitations. Specifically, polymeric nanomaterials are common BD carriers due to their biocompatibility and ease of synthesis. Different strategies are available for BD transportation, but the use of core-shell encapsulation is preferable for BDs. This review discusses recent articles on manufacturing methods for encapsulating BDs in polymeric materials, including emulsification, nanoprecipitation, self-encapsulation and coaxial electrospraying. The advantages and disadvantages of each method are analysed and discussed. We also explore the impact of critical synthesis parameters on BD activity, such as sonication in emulsifications. Lastly, we provide a vision of future challenges and perspectives for scale-up production and clinical translation.

In vivo and in vitro studies of a propolis-enriched silk fibroin-gelatin composite nanofiber wound dressing

In this study, electrospun nanofibers (NFs) used in trauma dressings were prepared using silk fibroin (SF) and gelatin (GT) as materials and highly volatile formic acid as the solvent, with three different concentrations of propolis extracts (EP), which were loaded through a simple process. The resulting samples were characterized by surface morphology, scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), contact angle meter, water absorption, degradation rate, and mechanical property tests. The incorporation of propolis improved its antibacterial properties against Escherichia coli, and Staphylococcus aureus, compared to those of the silk gelatin nanofiber material (SF/GT) alone. In vitro biocompatibility assays showed that SF/GT-1%EP had good cytocompatibility and hemocompatibility. In addition, it can also significantly promote the migration of L929 cells. SF/GT-1%EP was applied to a mouse model of full thickness skin defects, and it was found to significantly promote wound healing. These results indicate that the SF/GT-EP nanofiber material has good biocompatibility, migrating-promoting capability, antibacterial properties, and healing-promoting ability, providing a new idea for the treatment of full thickness skin defects.

Antimicrobial Active Packaging Containing Nisin for Preservation of Products of Animal Origin: An Overview

The preservation of food represents one of the greatest challenges in the food industry. Active packaging materials are obtained through the incorporation of antimicrobial and/or antioxidant compounds in order to improve their functionality. Further, these materials are used for food packaging applications for shelf-life extension and fulfilling consumer demands for minimal processed foods with great quality and safety. The incorporation of antimicrobial peptides, such as nisin, has been studied lately, with a great interest applied to the food industry. Antimicrobials can be incorporated in various matrices such as nanofibers, nanoemulsions, nanoliposomes, or nanoparticles, which are further used for packaging. Despite the widespread application of nisin as an antimicrobial by directly incorporating it into various foods, the use of nisin by incorporating it into food packaging materials is researched at a much smaller scale. The researchers in this field are still in full development, being specific to the type of product studied. The purpose of this study was to present recent results obtained as a result of using nisin as an antimicrobial agent in food packaging materials, with a focus on applications on products of animal origin. The findings showed that nisin incorporated in packaging materials led to a significant reduction in the bacterial load (the total viable count or inoculated strains), maintained product attributes (physical, chemical, and sensorial), and prolonged their shelf-life.

Electrospun Fibers: Versatile Approaches for Controlled Release Applications

Electrospinning has been one of the most attractive methods of fiber fabrication in the last century. A lot of studies have been conducted, especially in tissue engineering and drug delivery using electrospun fibers. Loading many different drugs and bioactive agents on or within these fibers potentiates the efficacy of such systems; however, there are still no commercial products with this technology available in the market. Various methods have been developed to improve the mechanical and physicochemical behavior of structures toward more controllable delivery systems in terms of time, place, or quantity of release. In this study, most frequent methods used for the fabrication of controlled release electrospun fibers have been reviewed. Although there are a lot of achievements in the fabrication of controlled release fibers, there are still many challenges to be solved to reach a qualified, reproducible system applicable in the pharmaceutical industry.

Bacterial Cellulose Membranes as Carriers for Nisin: Incorporation, Antimicrobial Activity, Cytotoxicity and Morphology

Based on the previous study, in which nisin and bacterial cellulose were utilized, this new experiment loads nisin into bacterial cellulose (N–BC) and evaluates the morphological characteristics, cytotoxicity, antimicrobial activity and stability of the developed system. The load efficiency of nisin in BC was evaluated by an agar diffusion assay, utilizing Lactobacillus sakei, and total proteins. After having found the ideal time and concentration for the loading process, the system stability was evaluated for 100 days at 4, 25 and 37 °C against Staphylococcus aureus and L. sakei. Thus, in this study, there is a system that proves to be efficient, once BC has enhanced the antimicrobial activity of nisin, acting as a selective barrier for other compounds present in the standard solution and protecting the peptide. After 4 h, with 45% of proteins, this activity was almost 2 log10 higher than that of the initial solution. Once the nisin solution was not pure, it is possible to suggest that the BC may have acted as a filter. This barrier enhanced the nisin activity and, as a consequence of the nisin loading, a stable N–BC system formed. The N–BC could create meaningful material for pharmaceutical and food applications.

Electrospun Zein/Polyoxyethylene Core-Sheath Ultrathin Fibers and Their Antibacterial Food Packaging Applications

The purpose of this work is to develop a novel ultrathin fibrous membrane with a core-sheath structure as antibacterial food packaging film. Coaxial electrospinning was exploited to create the core-sheath structure, by which the delivery regulation of the active substance was achieved. Resveratrol (RE) and silver nanoparticles (AgNPs) were loaded into electrospun zein/polyethylene oxide ultrathin fibers to ensure a synergistic antibacterial performance. Under the assessments of a scanning electron microscope and transmission electron microscope, the ultrathin fiber was demonstrated to have a fine linear morphology, smooth surface and obvious core-sheath structure. X-ray diffraction and Fourier transform infrared analyses showed that RE and AgNPs coexisted in the ultrathin fibers and had good compatibility with the polymeric matrices. The water contact angle experiments were conducted to evaluate the hydrophilicity and hygroscopicity of the fibers. In vitro dissolution tests revealed that RE was released in a sustained manner. In the antibacterial experiments against Staphylococcus aureus and Escherichia coli, the diameters of the inhibition zone of the fiber were 8.89 ± 0.09 mm and 7.26 ± 0.10 mm, respectively. Finally, cherry tomatoes were selected as the packaging object and packed with fiber films. In a practical application, the fiber films effectively reduced the bacteria and decreased the quality loss of cherry tomatoes, thereby prolonging the fresh-keeping period of cherry tomatoes to 12 days. Following the protocols reported here, many new food packaging films can be similarly developed in the future.

A review of current advancements for wound healing: Biomaterial applications and medical devices

Wound healing is a complex process that is critical in restoring the skin's barrier function. This process can be interrupted by numerous diseases resulting in chronic wounds that represent a major medical burden. Such wounds fail to follow the stages of healing and are often complicated by a pro‐inflammatory milieu attributed to increased proteinases, hypoxia, and bacterial accumulation. The comprehensive treatment of chronic wounds is still regarded as a significant unmet medical need due to the complex symptoms caused by the metabolic disorder of the wound microenvironment. As a result, several advanced medical devices, such as wound dressings, wearable wound monitors, negative pressure wound therapy devices, and surgical sutures, have been developed to correct the chronic wound environment and achieve skin tissue regeneration. Most medical devices encompass a wide range of products containing natural (e.g., chitosan, keratin, casein, collagen, hyaluronic acid, alginate, and silk fibroin) and synthetic (e.g., polyvinyl alcohol, polyethylene glycol, poly[lactic‐co‐glycolic acid], polycaprolactone, polylactic acid) polymers, as well as bioactive molecules (e.g., chemical drugs, silver, growth factors, stem cells, and plant compounds). This review addresses these medical devices with a focus on biomaterials and applications, aiming to deliver a critical theoretical reference for further research on chronic wound healing.

Quaternized chitin/tannic acid bilayers layer-by-layer deposited poly(lactic acid)/polyurethane nanofibrous mats decorated with photoresponsive complex and silver nanoparticles for antibacterial activity

Chronic wounding treatment based on bacterially infected diabetes suffers an essential limitation in persistent skin injuries due to the resistance of progressive antibiotics, which inhibits the process of healing with wound tissue. Therefore, biologically friendly and nontoxic bio-based mats without antibiotics are taken for granted as a versatile platform for biomedical dressing, but urgently necessitates further functional diversification. Herein, a novel tannic acid (TA)/silver (Ag)-modified poly(lactic acid) (PLA)/Polyurethane (PU) antibacterial hybrid nanofibers were successfully constructed by electrospinning technology. Layer-by-layer (LBL) self-assembly technique was utilized to produce membranes via deposited biocompatible quaternized chitin (QC) and TA. The mats are enabled with outstanding flexibility, antibacterial activity, great hemocompatibility, and good ROS-scavenger in a wounding environment. Consequently, the basis of morphology and structure of electrospun membranes was verified by SEM and FT-IR. Besides, the LBL-structured surface was proved to impart improved wettability and hydrophilic via the test of water contact angle. Additionally, antimicrobial experiments demonstrate the effective broad-spectrum antibacterial ability of as-prepared hybrids, inhibiting infection of gram-positive microbial (S. aureus) as well as gram-negative microbial. Finally, the anti-oxidation performance holds great promise in conducive to the formation favorable physiological environment for wound healing. In conclusion, this work establishes a feasible but effective pathway to construct a multifunctional antibacterial dressing for the skin infection.

Strategies for sustained drug release from electrospun multi-layer nanostructures

Among different kinds of modified release profiles, sustained drug release (SDR) has received the most attention due to its capability to provide a "safe, efficacious, and convenient" drug delivery effect. Electrospun nanofibers have shown their popularity in this interdisciplinary field, as demonstrated by the first reports about SDRs on drug delivery applications of blended nanofibers and core-shell nanofibers. Along with the evolution of electrospinning from a single-fluid blending process to coaxial, tri-axial, side-by-side, and other multi-fluid processes, more multi-chamber nanostructures can be created through a single-step straight forward manner. These multi-chamber nanostructures can act as a powerful platform to support a wide variety of new strategies for the development of novel SDR nanomaterials. Thus, this review describes a combination history of electrospinning and SDR and its further development trend. After a summary of the presently popular multi-chamber core-shell nanostructures, 15 strategies for furnishing SDR profiles are categorized and exemplified. The perspectives of electrospun multi-chamber nanostructures for further promoting SDR are narrated. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Development of a low-temperature extrusion process for production of GRAS bioactive-polymer loaded compounds for targeting antimicrobial-resistant (AMR) bacteria

Antimicrobial resistance (AMR) is recognised globally as one of the greatest threats to human and animal health; thus, discovery of alternative antibacterial agents to address AMR is a priority challenge. This study constitutes the first report of a low-melting temperature, polymer- extrusion process for the smart delivery of thermally-sensitive antimicrobial bioactives, including generally-regarded-as-safe (GRAS) bioactives derived from various sources. Bioactives were assessed before and after extrusion by determining their respective minimum inhibitory concentrations (MIC). WHO-priority AMR-bacterial isolates causing zoonotic infections were evaluated along with use of standard ATCC strains. Findings revealed that this copolymer method was capable of delivering thermally-sensitive bioactives with varying degrees of growth inhibition against the AMR-bacterial strains. The extrusion process was found to increase the effect of nisin against MRSA (4-fold increase) and L. monocytogenes (6.4-fold increase), silver nitrate (AgNO₃) against E. coli (3.6-fold increase) and S. epidermidis (1.25-fold increase), and chitosan against S. aureus (1.25-fold). Findings show the potential applicability of this polymer extrusion process for developing future bioactive-loaded polymer compounds; thus, highlighting the potential of converging bio-based industry with novel materials for enabling 'One-Health' solutions.

Influence of Nisin-Biogel at Subinhibitory Concentrations on Virulence Expression in Staphylococcus aureus Isolates from Diabetic Foot Infections

A new approach to diabetic foot infections (DFIs) has been investigated, using a nisin-biogel combining the antimicrobial peptide (AMP) nisin with the natural polysaccharide guar-gum. Since in in vivo conditions bacteria may be exposed to decreased antimicrobial concentrations, known as subinhibitory concentrations (sub-MICs), effects of nisin-biogel sub-MIC values corresponding to 1/2, 1/4 and 1/8 of nisin's minimum inhibitory concentration (MIC) on virulence expression by six Staphylococcus aureus DFI isolates was evaluated by determining bacteria growth rate; expression of genes encoding for staphylococcal protein A (spA), coagulase (coa), clumping factor A (clfA), autolysin (atl), intracellular adhesin A (icaA), intracellular adhesin D (icaD), and the accessory gene regulator I (agrI); biofilm formation; Coa production; and SpA release. Nisin-biogel sub-MICs decreased bacterial growth in a strain- and dose-dependent manner, decreased agrI, atl and clfA expression, and increased spA, coa, icaA and icaD expression. Biofilm formation increased in the presence of nisin-biogel at 1/4 and 1/8 MIC, whereas 1/2 MIC had no effect. Finally, nisin-biogel at sub-MICs did not affect coagulase production, but decreased SpA production in a dose-dependent manner. Results highlight the importance of optimizing nisin-biogel doses before proceeding to in vivo trials, to reduce the risk of virulence factor's up-regulation due to the presence of inappropriate antimicrobial concentrations.

Functionalized Antimicrobial Nanofibers: Design Criteria and Recent Advances

The rise of antibiotic resistance has become a major threat to human health and it is spreading globally. It can cause common infectious diseases to be difficult to treat and leads to higher medical costs and increased mortality. Hence, multifunctional polymeric nanofibers with distinctive structures and unique physiochemical properties have emerged as a neo-tool to target biofilm and overcome deadly bacterial infections. This review emphasizes electrospun nanofibers' design criteria and properties that can be utilized to enhance their therapeutic activity for antimicrobial therapy. Also, we present recent progress in designing the surface functionalization of antimicrobial nanofibers with non-antibiotic agents for effective antibacterial therapy. Lastly, we discuss the future trends and remaining challenges for polymeric nanofibers.

Enzyme- and Relative Humidity-Responsive Antimicrobial Fibers for Active Food Packaging

Active food packaging materials that are sustainable, biodegradable, and capable of precise delivery of antimicrobial active ingredients (AIs) are in high demand. Here, we report the development of novel enzyme- and relative humidity (RH)-responsive antimicrobial fibers with an average diameter of 225 ± 50 nm, which can be deposited as a functional layer for packaging materials. Cellulose nanocrystals (CNCs), zein (protein), and starch were electrospun to form multistimuli-responsive fibers that incorporated a cocktail of both free nature-derived antimicrobials such as thyme oil, citric acid, and nisin and cyclodextrin-inclusion complexes (CD-ICs) of thyme oil, sorbic acid, and nisin. The multistimuli-responsive fibers were designed to release the free AIs and CD-ICs of AIs in response to enzyme and RH triggers, respectively. Enzyme-responsive release of free AIs is achieved due to the degradation of selected polymers, forming the backbone of the fibers. For instance, protease enzyme can degrade zein polymer, further accelerating the release of AIs from the fibers. Similarly, RH-responsive release is obtained due to the unique chemical nature of CD-ICs, enabling the release of AIs from the cavity at high RH. The successful synthesis of CD-ICs of AIs and incorporation of antimicrobials in the structure of the multistimuli-responsive fibers were confirmed by X-ray diffraction and Fourier transform infrared spectrometry. Fibers were capable of releasing free AIs when triggered by microorganism-exudated enzymes in a dose-dependent manner and releasing CD-IC form of AIs in response to high relative humidity (95% RH). With 24 h of exposure, stimuli-responsive fibers significantly reduced the populations of foodborne pathogenic bacterial surrogates Escherichia coli (by ∼5 log unit) and Listeria innocua (by ∼5 log unit), as well as fungi Aspergillus fumigatus (by >1 log unit). More importantly, the fibers released more AIs at 95% RH than at 50% RH, which resulted in a higher population reduction of E. coli at 95% RH. Such biodegradable, nontoxic, and multistimuli-responsive antimicrobial fibers have great potential for broad applications as active and smart packaging systems.

Photocatalytic Nanofiber Membranes for the Degradation of Micropollutants and Their Antimicrobial Activity: Recent Advances and Future Prospects

This review paper systematically evaluates current progress on the development and performance of photocatalytic nanofiber membranes often used in the removal of micropollutants from water systems. It is demonstrated that nanofiber membranes serve as excellent support materials for photocatalytic nanoparticles, leading to nanofiber membranes with enhanced optical properties, as well as improved recovery, recyclability, and reusability. The tremendous performance of photocatalytic membranes is attributed to the photogenerated reactive oxygen species such as hydroxyl radicals, singlet oxygen, and superoxide anion radicals introduced by catalytic nanoparticles such as TiO₂ and ZnO upon light irradiation. Hydroxyl radicals are the most reactive species responsible for most of the photodegradation processes of these unwanted pollutants. The review also demonstrates that self-cleaning and antimicrobial nanofiber membranes are useful in the removal of microbial species in water. These unique materials are also applicable in other fields such as wound dressing since the membrane allows for oxygen flow in wounds to heal while antimicrobial agents protect wounds against infections. It is demonstrated that antimicrobial activities against bacteria and photocatalytic degradation of micropollutants significantly reduce membrane fouling. Therefore, the review demonstrates that electrospun photocatalytic nanofiber membranes with antimicrobial activity form efficient cost-effective multifunctional composite materials for the removal of unwanted species in water and for use in various other applications such as filtration, adsorption and electrocatalysis.

Recent applications of electrical, centrifugal, and pressurised emerging technologies for fibrous structure engineering in drug delivery, regenerative medicine and theranostics

Advancements in technology and material development in recent years has led to significant breakthroughs in the remit of fiber engineering. Conventional methods such as wet spinning, melt spinning, phase separation and template synthesis have been reported to develop fibrous structures for an array of applications. However, these methods have limitations with respect to processing conditions (e.g. high processing temperatures, shear stresses) and production (e.g. non-continuous fibers). The materials that can be processed using these methods are also limited, deterring their use in practical applications. Producing fibrous structures on a nanometer scale, in sync with the advancements in nanotechnology is another challenge met by these conventional methods. In this review we aim to present a brief overview of conventional methods of fiber fabrication and focus on the emerging fiber engineering techniques namely electrospinning, centrifugal spinning and pressurised gyration. This review will discuss the fundamental principles and factors governing each fabrication method and converge on the applications of the resulting spun fibers; specifically, in the drug delivery remit and in regenerative medicine.

Encapsulation of Pharmaceutical and Nutraceutical Active Ingredients Using Electrospinning Processes

Electrospinning is an inexpensive and powerful method that employs a polymer solution and strong electric field to produce nanofibers. These can be applied in diverse biological and medical applications. Due to their large surface area, controllable surface functionalization and properties, and typically high biocompatibility electrospun nanofibers are recognized as promising materials for the manufacturing of drug delivery systems. Electrospinning offers the potential to formulate poorly soluble drugs as amorphous solid dispersions to improve solubility, bioavailability and targeting of drug release. It is also a successful strategy for the encapsulation of nutraceuticals. This review aims to briefly discuss the concept of electrospinning and recent progress in manufacturing electrospun drug delivery systems. It will further consider in detail the encapsulation of nutraceuticals, particularly probiotics.

Impact of a Single Point Mutation on the Antimicrobial and Fibrillogenic Properties of Cryptides from Human Apolipoprotein B

Host defense peptides (HDPs) are gaining increasing interest, since they are endowed with multiple activities, are often effective on multidrug resistant bacteria and do not generally lead to the development of resistance phenotypes. Cryptic HDPs have been recently identified in human apolipoprotein B and found to be endowed with a broad-spectrum antimicrobial activity, with anti-biofilm, wound healing and immunomodulatory properties, and with the ability to synergistically act in combination with conventional antibiotics, while being not toxic for eukaryotic cells. Here, a multidisciplinary approach was used, including time killing curves, differential scanning calorimetry, circular dichroism, ThT binding assays, and transmission electron microscopy analyses. The effects of a single point mutation (Pro → Ala in position 7) on the biological properties of ApoB-derived peptide r(P)ApoB_L^Pro have been evaluated. Although the two versions of the peptide share similar antimicrobial and anti-biofilm properties, only r(P)ApoB_L^Ala peptide was found to exert bactericidal effects. Interestingly, antimicrobial activity of both peptide versions appears to be dependent from their interaction with specific components of bacterial surfaces, such as LPS or LTA, which induce peptides to form β-sheet-rich amyloid-like structures. Altogether, obtained data indicate a correlation between ApoB-derived peptides self-assembling state and their antibacterial activity.

Nanofibers as drug-delivery systems for antimicrobial peptides

Microbial infections are a major worldwide public health problem because a number of microorganisms can show drug resistance. Antimicrobial peptides (AMPs) are small biomolecules that present antimicrobial and immunomodulatory activities. Despite their great potential, there are still many barriers to the formulation of these molecules. In this context, nanotechnological approaches such as nanofibers are candidate drug-delivery systems for AMP formulations. These nanomaterials have a large contact surface and may carry several AMPs (single or multilayer), directing them to specific targets. Thus, this review describes the main advances related to the use of nanofibers as drug-delivery systems for AMPs. These strategies can contribute directly to the design of new multifunctional wound dressings, coatings for prostheses, and tissue engineering applications.

Characteristics and therapeutic applications of antimicrobial peptides

The demand for novel antimicrobial compounds is rapidly growing due to the phenomenon of antibiotic resistance in bacteria. In response, numerous alternative approaches are being taken including use of polymers, metals, combinatorial approaches, and antimicrobial peptides (AMPs). AMPs are a naturally occurring part of the immune system of all higher organisms and display remarkable broad-spectrum activity and high selectivity for bacterial cells over host cells. However, despite good activity and safety profiles, AMPs have struggled to find success in the clinic. In this review, we outline the fundamental properties of AMPs that make them effective antimicrobials and extend this into three main approaches being used to help AMPs become viable clinical options. These three approaches are the incorporation of non-natural amino acids into the AMP sequence to impart better pharmacological properties, the incorporation of AMPs in hydrogels, and the chemical modification of surfaces with AMPs for device applications. These approaches are being developed to enhance the biocompatibility, stability, and/or bioavailability of AMPs as clinical options.

Weathering of Antibacterial Melt-Spun Polyfilaments Modified by Pine Rosin

For many antibacterial polymer fibres, especially for those with natural functional additives, the antibacterial response might not last over time. Moreover, the mechanical performance of polymeric fibres degrades significantly during the intended operation, such as usage in textile and industrial filter applications. The degradation process and overall ageing can lead to emitted volatile organic compounds (VOCs). This work focused on the usage of pine rosin as natural antibacterial chemical and analysed the weathering of melt-spun polyethylene (PE) and poly lactic acid (PLA) polyfilaments. A selected copolymer surfactant, as an additional chemical, was studied to better integrate rosin with the molecular structure of the plastics. The results reveal that a high 20 w-% of rosin content can be obtained by surfactant addition in non-oriented PE and PLA melt-spun polyfilaments. According to the VOC analysis, interestingly, the total emissions from the melt-spun PE and PLA fibres were lower for rosin-modified (10 w-%) fibres and when analysed below 60 °C. The PE fibres of the polyfilaments were found to be clearly more durable in terms of the entire weathering study, i.e., five weeks of ultraviolet radiation, thermal ageing and standard washing. The antibacterial response against Gram-positive Staphylococcus aureus by the rosin-containing fibres was determined to be at the same level (decrease of 3–5 logs cfu/mL) as when using 1.0 w-% of commercial silver-containing antimicrobial. For the PE polyfilaments with rosin (10 w-%), full killing response (decrease of 3–5 logs cfu/mL) remained after four weeks of accelerated ageing at 60 °C.

Effective adsorption of nisin on the surface of polystyrene using hydrophobin HGFI

Herein, a new method was demonstrated for effective immobilization of the antibacterial peptide nisin on Grifola frondosa hydrophobin (HGFI), without the need of any additional complex reaction. Hydrophobin can self-assemble as a monolayer to form continuous negative-charged surfaces with enhanced wettability and biocompatibility. Adding nisin solution to such hydrophobin surface created antibacterial surfaces. The quantification analysis revealed that more nisin could be adsorbed on the HGFI-coated than to control polystyrene surfaces at different pH values. This suggested that electronic attraction and wettability may play important roles in this process. The transmission electron microscopy, atomic force microscopy and fourier transform infrared (FTIR) analysis indicated the adsorption mode of nisin on the HGFI film, i.e., hydrophobins served as an adhesive layer for binding charged peptides to interfaces. The antibacterial activity of the treated surface was investigated via counting, a nucleic acid release test, scanning electron microscopy, and biofilm detection. These results indicated the excellent antibacterial activity of nisin adsorbed on the HGFI-coated surfaces. The activity retention of adsorbed nisin was demonstrated by immersing the modified substrates in a flowed liquid condition.

Potential Novel Food-Related and Biomedical Applications of Nanomaterials Combined with Bacteriocins

Bacteriocins are antimicrobial peptides or proteinaceous materials produced by bacteria against pathogens. These molecules have high efficiency and specificity and are equipped with many properties useful in food-related applications, such as food preservatives and additives, as well as biomedical applications, such as serving as alternatives to current antibacterial, antiviral, anticancer, and antibiofilm agents. Despite their advantages as alternative therapeutics over existing strategies, several limitations of bacteriocins, such as the high cost of isolation and purification, narrow spectrum of activity, low stability and solubility, and easy enzymatic degradation, need to be improved. Nanomaterials are promising agents in many biological applications. They are widely used in the conjugation or decoration of bacteriocins to augment the activity of bacteriocins or reduce problems related to their use in biomedical applications. Therefore, bacteriocins combined with nanomaterials have emerged as promising molecules that can be used in various biomedical applications. This review highlights the features of bacteriocins and their limitations in biomedical applications and provides a detailed overview of the uses of different nanomaterials in improving the limitations. Our review focuses on the potential applications of nanomaterials combined with bacteriocins as new designer molecules for use in future therapeutic strategies.

Current approaches and future prospects of nanofibers: a special focus on antimicrobial drug delivery

Antibacterial nanofibers have a great potential for effective treatment of infections. They act as drug reservoir systems that release higher quantities of antibacterial agents/drug in a controlled manner at infection sites and prevent drug resistance, while concomitantly decreasing the systemic toxicity. With this drug delivery system, it is also possible to achieve multiple drug entrapment and also simultaneous or sequential release kinetics at the site of action. Therefore, advances in antibacterial nanofibers as drug delivery systems were overviewed within this article. Recently published data on antibacterial drug delivery was also summarised to provide a view of the current state of art in this field. Although antibacterial use seems to be limited and one can ask that 'what is left to be discovered?'; recent update literatures in this field highlighted the use of nanofibers from very different perspectives. We believe that readers will be benefiting this review for enlightening of novel ideas.

Electrospinning for healthcare: recent advancements

This perspective explores recent developments and innovations in the electrospinning technique and their potential applications in biomedicine.

An antimicrobial peptide-immobilized nanofiber mat with superior performances than the commercial silver-containing dressing

Silver-containing dressings are widely used for the treatment of infected wounds in clinics, but the potential risks of heavy metals are still a common concern. In this study, we prepared a type of electrospun starch nanofiber mat containing the antimicrobial peptide ε-poly-lysine (Starch-EPL) and compared its relevant properties with a representative silver-containing dressing 3M™ Tegaderm™ Alginate Ag (Alginate-Ag). SEM, FTIR and EDAX results show the two samples have similar fiber structures and are loaded with antibacterial agents. The comparison results indicate that the Starch-EPL nanofiber mat has equivalent permeability and absorbency with Alginate-Ag but higher mechanical property and wettability. Moreover, the Starch-EPL nanofiber mat has comparable antibacterial activity against both Gram-negative and Gram-positive bacteria with Alginate-Ag, but markedly better biocompatibility than that. The Starch-EPL nanofiber mat can inhibit the growth of bacteria for at least 14 days by sustainably releasing EPL, showing great potential as a long-term antibacterial dressing. All these results demonstrate that the Starch-EPL nanofiber mat may be a good candidate to replace the traditional silver-containing dressings.

Application of blocking and immobilization of electrospun fiber in the biomedical field

The fiber obtained by electrospinning technology is a kind of biomaterial with excellent properties, which not only has a unique micro-nanostructure that gives it a large specific surface area and porosity, but also has satisfactory biocompatibility and degradability (if the spinning material used is a degradable polymer). These biomaterials provide a suitable place for cell attachment and proliferation, and can also achieve immobilization. On the other hand, its large porosity and three-dimensional spatial structure show unique blocking properties in drug delivery applications in order to achieve the purpose of slow release or even controlled release. The immobilization effect or blocking effect of these materials is mainly reflected in the hollow or core-shell structure. The purpose of this paper is to understand the application of the electrospun fiber based on biodegradable polymers (aliphatic polyesters) in the biomedical field, especially the immobilization or blocking effect of the electrospun fiber membrane on cells, drugs or enzymes. This paper focuses on the performance of these materials in tissue engineering, wound dressing, drug delivery system, and enzyme immobilization technology. Finally, based on the existing research basis of the electrospun fiber in the biomedical field, a potential research direction in the future is put forward, and few suggestions are also given for the technical problems that urgently need to be solved.

Long-Term Antibacterial Effect of Electrospun Polyvinyl Alcohol/Polyacrylate Sodium Nanofiber Containing Nisin-Loaded Nanoparticles

Response Surface Methodology (RSM) was used to assess the optimal conditions for a Water/Oil/Water (W/O/W) emulsion for encapsulated nisin (EN). Nano-encapsulated nisin had high encapsulation efficiencies (EE) (86.66 ± 1.59%), small particle size (320 ± 20 nm), and low polydispersity index (0.27). Biodegradable polyvinyl alcohol (PVA) and polyacrylate sodium (PAAS) were blended with EN and prepared by electrospinning. Scanning electron microscopy (SEM) revealed PVA/PAAS/EN nanofibers with good morphology, and that their EN activity and mechanical properties were enhanced. When the ultrasonication time was 15 min and 15% EN was added, the nanofibers had optimal mechanical, light transmittance, and barrier properties. Besides, the release behavior of nisin from the nanofibers fit the Korsemeyer–Peppas (KP) model, a maximum nisin release rate of 85.28 ± 2.38% was achieved over 16 days. At 4 °C, the growth of Escherichia coli and Staphylococcus aureus was inhibited for 16 days in nanofibers under different ultrasonic times. The application of the fiber in food packaging can effectively inhibit the activity of food microorganisms and prolong the shelf life of strawberries, displaying a great potential application for food preservation.

Fabrication of Promising Antimicrobial Aloe Vera/PVA Electrospun Nanofibers for Protective Clothing

In the present condition of COVID-19, the demand for antimicrobial products such as face masks and surgical gowns has increased. Because of this increasing demand, there is a need to conduct a study on the development of antimicrobial material. Therefore, this study was conducted on the development of Aloe Vera and Polyvinyl Alcohol (AV/PVA) electrospun nanofibers. Four different fibers were developed by varying the concentrations of Aloe vera (0.5%, 1.5%, 2.5%, and 3%) while maintaining the concentration of PVA constant. The developed samples were subjected to different characterization techniques such as SEM, FTIR, XRD, TGA, and ICP studies. After that, the antimicrobial activity of the developed Aloe Vera/PVA electrospun nanofibers was checked against Gram-positive (Staphylococcus aureus) bacteria and Gram-negative (Escherichia coli) bacteria. The developed nanofibers had high profile antibacterial activity against both bacteria, but showed excellent results against S. aureus bacteria as compared with E. coli. These nanofibers have potential applications in the development of surgical gowns, gloves, etc.

Porous Silicon Nanoparticles Embedded in Poly(lactic-co-glycolic acid) Nanofiber Scaffolds Deliver Neurotrophic Payloads to Enhance Neuronal Growth

Scaffolds made from biocompatible polymers provide physical cues to direct the extension of neurites and to encourage repair of damaged nerves. The inclusion of neurotrophic payloads in these scaffolds can substantially enhance regrowth and repair processes. However, many promising neurotrophic candidates are excluded from this approach due to incompatibilities with the polymer or with the polymer processing conditions. This work provides one solution to this problem by incorporating porous silicon nanoparticles (pSiNPs) that are pre-loaded with the therapeutic into a polymer scaffold during fabrication. The nanoparticle-drug-polymer hybrids are prepared in the form of oriented poly(lactic-co-glycolic acid) nanofiber scaffolds. We test three different therapeutic payloads: bpV(HOpic), a small molecule inhibitor of phosphatase and tensin homolog (PTEN); an RNA aptamer specific to tropomyosin-related kinase receptor type B (TrkB); and the protein nerve growth factor (NGF). Each therapeutic is loaded using a loading chemistry that is optimized to slow the rate of release of these water-soluble payloads. The drug-loaded pSiNP-nanofiber hybrids release approximately half of their TrkB aptamer, bpV(HOpic), or NGF payload in 2, 10, and >40 days, respectively. The nanofiber hybrids increase neurite extension relative to drug-free control nanofibers in a dorsal root ganglion explant assay.

Chitosan-glucan complex hollow fibers reinforced collagen wound dressing embedded with aloe vera. II. Multifunctional properties to promote cutaneous wound healing

This study presents an innovative multifunctional system in fabricating new functional wound dressing (FWD) products that could be used for skin regeneration, especially in cases of infected chronic wounds and ulcers. The innovation is based on the extraction, characterization, and application of collagen (CO)/chitosan-glucan complex hollow fibers (CSGC)/aloe vera (AV) as a novel FWS. For the first time, specific hollow fibers were extracted with controlled inner (500-900 nm)/outer (2-3 µm) diameters from mycelium of Schizophyllum commune. Further on, research and evaluation of morphology, hydrolytic stability, and swelling characteristics of CO/CSGC@AV were carried out. The obtained FWS showed high hydrolytic stability with enhanced swelling characteristics compared to native collagen. The hemostatic effect of FWS increased significantly in the presence of CSGC, compared to native CO and displayed excellent biocompatibility which was tested by using normal human dermal fibroblast (NHDF). The FWS showed high antibacterial activity against different types of bacteria (positive/negative grams). From in vivo measurements, the novel FWS increased the percentage of wound closure after one week of treatment. All these results imply that the new CO/CSGC@AV-FWD has the potential for clinical skin regeneration and applying for controlled drug release.

Antimicrobial-loaded nanocarriers for food packaging applications

Increasing the demands of consumers for organic and safer foods has led to applying new technologies for food preservation. Active packaging (AP) containing natural antimicrobial agents is a good candidate for promoting the shelf life of food products. The efficiency of AP has been enhanced through nanoencapsulation methods, in which antimicrobial-loaded nanocarriers could provide a controlled release of antimicrobial active packaging for keeping the quality of foods during storage. The main objective of this review is to introduce common methods for designing novel encapsulation delivery systems offering controlled release of antimicrobials in the AP systems. The common nanocarriers for enveloping antimicrobial agents are described and the current state of art in the application of nanoencapsulated antimicrobials in development of antimicrobial APs have been summarized and tabulated. Incorporation of a carrier loaded with natural antimicrobial agents is the most effective method for developing AP in the food packaging sector which has become possible by using nanoencapsulated antimicrobials in films or coating structures, instead of using their free form. Nanoencapsulation approaches provide many advantages including protection against environmental stresses, release control, and improving the solubility and absorption of natural antimicrobials in AP, which are the main achievements overcoming the barriers for using natural antimicrobials in food packaging.