Antimicrobial Filler Research Articles

Bioactive solids obtained from montmorillonite functionalization by biogenic compounds to be used as antimicrobial filler

The growth of fungi and bacteria on material surfaces negatively impacts human health and produces economic losses, and harmful waste for the environment. In the present research, new eco-friendly and low-cost antimicrobial fillers are actively sought by the functionalization of montmorillonite using biogenic compounds. The synthesized hybrids from montmorillonite, natural surfactant, and geraniol were characterized and showed effective antifungal and antibacterial activity.

Improvement of PLA-PVA/chitosan nanocomposite laminate film for packaging via crosslinking with electron beam irradiation: Mechanical, thermal and antimicrobial analysis

This research investigated and developed a laminate packaging film of poly(lactic acid) (PLA) and poly(vinyl alcohol) (PVA) containing modified chitosan nanoparticles (MCSNPs) treated with 3-(trimethoxysilyl)propyl methacrylate silane (TMSPM) which functioned both as a reinforcement and as an antimicrobial filler. Electron beam irradiation caused crosslink between the PVA and MCSNP molecules via the free radical of carbonyl in the methacrylate group of TMSPM-grafted chitosan nanoparticles and the free radical of hydroxyl group in poly(vinyl alcohol). This improved the PVA hydrophobicity. In addition, the laminate with PVA-g-MCSNPs film irradiated with a 30 kGy electron beam showed the best performance properties due to improved interfacial adhesion between PLA and PVA-g-MCSNPs. As a consequence, the mechanical and thermal properties improved. The 30 kGy irradiated film also had better antibacterial activity against both Escherichia coli and Staphylococcus aureus.

A Temporary Acrylic Soft Denture Lining Material Enriched with Silver-Releasing Filler-Cytotoxicity, Mechanical and Antifungal Properties.

Colonization of temporary denture soft linings and underlying tissues by yeast-like fungi is an important clinical problem due to the negative influence on the process of prosthetic treatment. Typical hygienic procedures are often insufficient to prevent fungal infections, so in this study, an antimicrobial filler (silver sodium hydrogen zirconium phosphate) was introduced into acrylic soft liner at concentrations of 1, 2, 4, 6, 8 and 10% (w/w). The effect of this modification on antifungal properties against Candida albicans, cytotoxicity, Shore A hardness, tensile strength and tensile bond strength, sorption and solubility was investigated, considering the recommended 30-day period of temporary soft lining use. The most favorable compilation of properties was obtained at a 1 to 6% filler content, for which nearly a total reduction in Candida albicans was registered even after 30 days of sample storing. The tensile and bond strength of these composites was at the desired and stable level and did not differ from the results for the control material. Hardness increased with the increasing concentration in filler but were within the range typical for soft lining materials and their changes during the experiment were similar to the control material. The materials were not cytotoxic and sorption and solubility levels were stable.

Comparing digital light processing and stereolithography vat polymerization Technologies for antimicrobial 3D printing using silver oxide as an antimicrobial filler

AbstractVat polymerization technology allows filler particles to be incorporated into photosensitive 3D printing resin to improve the properties of the printed material. This method can be used to produce medical devices with an antimicrobial effect that can reduce biofilm formation and reduce infections due to indwelling devices. Metal oxides have the potential to combat antibiotic‐resistant bacteria, further lowering the risk of hospital‐acquired infections. The antimicrobial agent in this study, silver oxide, was evaluated for its antimicrobial effect against gram‐positive bacteria (Staphylococcus epidermidis) as these are the main cause of biofilm formation. The 3D printed samples demonstrated a strong antimicrobial effect at low concentrations of 1 wt.%. Two vat polymerization technologies, stereolithography (SLA) and digital light processing (DLP), were compared for their suitability for producing 3D printed samples with an antimicrobial effect. DLP successfully produced samples with mechanical properties comparable to the base resin, whereas SLA samples had reduced mechanical strength at higher concentrations of silver oxide filler. Neither printing technology nor silver oxide concentration had a statistically significant effect on the mechanical properties of the printed materials.

Evaluation of poly(lactic acid) and ECOVIO based biocomposites loaded with antimicrobial sodium phosphate microparticles

Herein, biobased composite materials based on poly(lactic acid) (PLA) and poly(butylene adipate-co-terephthalate) (PBAT) as matrices, sodium hexametaphosphate microparticles (E452i, food additive microparticles, 1 and 5 wt%) as antimicrobial filler and acetyl tributyl citrate (ATBC, 15 wt%) as plasticizer, were developed for potential food packaging applications. Two set of composite films were obtained by melt-extrusion and compression molding, i) based on PLA matrix and ii) based on Ecovio® matrix (PLA/PBAT blend). Thermal characterization by thermogravimetric analysis and differential scanning calorimetry demonstrated that the incorporation of E452i particles improved thermal stability and crystallinity, while the mechanical test showed an increase in the Young's modulus. E452i particles also provide antimicrobial properties to the films against food-borne bacteria Listeria innocua and Staphylococcus aureus, with bacterial reduction percentages higher than 50 % in films with 5 wt% of particles. The films also preserved their disintegradability as demonstrated by an exhaustive characterization of the films under industrial composting conditions. Therefore, the results obtained in this work reveal the potential of these biocomposites as appropriated materials for antibacterial and compostable food packaging films.

Facile preparation of composite antimicrobial Al2O3 particles

Antimicrobial particles can inhibit or kill microorganisms, and have been widely used as antimicrobial filler in coatings and polymers. Herein, we present a facile method to prepare antimicrobial alumina particles by grafting epoxypropyl dimethydodecyl ammonium chloride (EPDDMAC) on γ-Al2O3 or ethylene–vinyl alcohol copolymer (EVOH) coated α-Al2O3.The results show that EPDDMAC can be grafted on γ-Al2O3 or EVOH-coated α-Al2O3 particles effectively, and the grafting rate rises with the increased EPDDMAC amount. The grafted composite particles exhibit excellent antibacterial properties against Escherichia coli and display great potential in antibacterial applications.

The Antifungal Fibers of Polyamide 12 Containing Silver and Metal Oxides.

The textile market is a vast industry that utilizes antimicrobial polymeric materials, including various types of fabrics, for medical and personal protection applications. Therefore, this study focused on examining four types of antimicrobial fillers, namely, metal oxides (zinc, titanium, copper) and nanosilver, as fillers in Polyamide 12 fibers. These fillers can be applied in the knitting or weaving processes to obtain woven polymeric fabrics for medical applications. The production of the fibers in this study involved a two-step approach: twin-screw extrusion and melt spinning. The resulting fibers were then characterized for their thermal properties (TGA, DSC), mechanical performance (tensile test, DMA), and antifungal activity. The findings of the study indicated that all of the fibers modified with fillers kill Candida albicans. However, the fibers containing a combination of metal oxides and silver showed significantly higher antifungal activity (reduction rate % R = 86) compared to the fibers with only a mixture of metal oxides (% R = 21). Furthermore, the inclusion of metal oxides and nanosilver in the Polyamide 12 matrix hindered the formation of the crystal phase and decreased slightly the thermal stability and mechanical properties, especially for the composites with nanosilver. It was attributed to their worse dispersion and the presence of agglomerates.

Assessing the Dispersion Stability of Antimicrobial Fillers in Photosensitive Resin for Vat Polymerization 3D Printing.

Polymers are widely used in healthcare due to their biocompatibility and mechanical properties; however, the use of polymers in medical products can promote biofilm formation, which can be a source of hospital-acquired infections. Due to this, there is a rising demand for inherently antimicrobial polymers for devices in contact with patients. 3D printing as a manufacturing technology has increased exponentially in recent years. Surgical guides, orthotics, and prosthetics, among other medical devices, created by vat polymerization have been used in hospitals to treat patients. Biocompatible resins are available for these applications, but there is a lack of antimicrobial resins, which would further improve the technology for clinical use. The focus of this study was to assess settling of candidate antimicrobial metal and metal oxide fillers in vat polymerization resin to determine which fillers were compatible with the resin. Dispersion stability was assessed by measuring settling over the maximum print duration of the medium priced desktop 3D printers to evaluate printability of 17 potentially antimicrobial resins. Eight materials displayed settling behavior during the test period: molybdenum oxide, zirconium oxide nanopowder, scandium oxide, zirconium oxide, titanium oxide, tungsten oxide, lanthanum oxide, and magnesium oxide. No settling was observed for manganese oxide, magnesium oxide nanopowder, titanium oxide nanopowder, copper oxide, silver oxide, zinc oxide nanopowder, zinc oxide, silver nanopowder, and gold nanopowder during the test period. This method could be applied to assess settling of other fillers introduced into 3D printing resins before actual printing.

Characterization of Ag-Ion Releasing Zeolite Filled 3D Printed Resins.

There has been profound growth in the use of 3D printed materials in dentistry in general, including orthodontics. The opportunity to impart antimicrobial properties to 3D printed parts from existing resins requires the capability of forming a stable colloid incorporating antimicrobial fillers. The objective of this research was to characterize a colloid consisting of a 3D printable resin mixed with Ag-ion releasing zeolites and fumed silica to create 3D printed parts with antiviral properties. The final composite was tested for antiviral properties against SARS-CoV-2 and HIV-1. Antiviral activity was measured in terms of the half-life of SARS-CoV-2 and HIV-1 on the composite surface. The inclusion of the zeolite did not interfere with the kinetics measured on the surface of the ATR crystal. While the depth of cure, measured following ISO4049 guidelines, was reduced from 3.8 mm to 1.4 mm in 5 s, this greatly exceeded the resolution required for 3D printing. The colloid was stable for at least 6 months and the rheological behavior was dependent upon the fumed silica loading. The inclusion of zeolites and fumed silica significantly increased the flexural strength of the composite as measured by a 3 point bend test. The composite released approximately 2500 μg/L of silver ion per gram of composite as determined by potentiometry. There was a significant reduction of the average half-life of SARS-CoV-2 (1.9 fold) and HIV-1 (2.7 fold) on the surface of the composite. The inclusion of Ag-ion releasing zeolites into 3D-printable resin can result in stable colloids that generate composites with improved mechanical properties and antiviral properties.

Biocompatibility and biocidal effects of modified polylactide composites.

Polylactide (PLA) materials treated with antimicrobial fillers represent a suitable alternative to the production of medical devices. Their advantage is that they can prevent the growth of microorganisms and the formation of microbial biofilms on the surface and around composites. The work is focused on the evaluation of biocompatibility and biocide effect of PLA composite films filled with vermiculite and graphene oxide modified with silver (Ag+ and Ag nanoparticles), hexadecylpyridinium (HDP) and hexadecyltrimethylammonium (HDTMA) cations and their degradation leachates monitored at 1-3-6-month intervals. The antimicrobial effect of the leachates was detected by microdilution methods on gram-negative (Escherichia coli, Pseudomonas aeruginosa, Proteus mirabilis), gram-positive (Staphylococcus aureus, Streptococcus salivarius) bacteria and yeast (Candida albicans). The biocidal effect of composites on biofilm formation on the surface of composites was monitored by Christensen method and autoaggregation and motility tests. The biocompatibility of the composite and the leachates was assessed by 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) cytotoxicity assay. The evaluation of the antimicrobial effect of the leachates demonstrated that leachates of PLA composite filled with graphene oxide and Ag+ showed a stronger antimicrobial effect than leachates of PLA composite filled with vermiculite and Ag+ and Ag nanoparticles. The leachates of PLA composites containing vermiculite with HDP and HDTMA cations had a higher antimicrobial effect on G+ bacteria and yeast than G- bacteria. Bacterial growth, biofilm formation, autoaggregation and motility of the tested bacteria were most inhibited by the composite with vermiculite and Ag+ and Ag nanoparticles. Even after a 6-month degradation of this composite, bacterial growth and biofilm formation continued to be strongly inhibited up to 42 and 91%, respectively. The cytotoxic effect was proved only in the leachate of the composite with vermiculite containing HDP after 6 months of its degradation. Tests evaluating the biocompatibility of materials have shown that the vermiculite is the most preferred carrier and can be used in the future to bind other compounds. The study confirmed that PLA composite filled with vermiculite and Ag+ and Ag nanoparticles was the most stable and effective composite with the best biocompatible and biocidal properties.

Long-term antimicrobial effect of polylactide-based composites suitable for biomedical use

This work deals with the preparation and characterization of antimicrobial polymeric composite materials based on polylactide, which is currently widely investigated to produce temporary implants. Polylactide was blended with antimicrobial fillers: silver, hexadecylpyridinium or hexadecyltrimethylammonium bromides anchored on vermiculite or graphene oxide matrices in an amount of 1% wt. The prepared samples were characterized by conventional methods, further they were exposed to degradation tests in physiological saline conditions and characterized for their antimicrobial properties using common pathogen microorganisms. It has been proven that the prepared polylactide composites change their antimicrobial effects after being in physiological saline of pH 7 and 9 for 0–6 months. The weight of the composites changed by about 10%, and antimicrobial properties were growing over time. The effectiveness of the composites was confirmed for 6 months at minimum. Therefore, they are suitable for the preparation of temporary stents, catheters or implants suitable for fracture fixation.

Nitrogen doped titanium dioxide as an aesthetic antimicrobial filler in dental polymers

ObjectiveTo develop an aesthetic resin composite using a nitrogen-doped titanium dioxide (NTiO2) filler that possesses antimicrobial properties against cariogenic bacteria. MethodsN-TiO2 powder was manufactured by calcining commercial TiO2 with urea. Free radical release from the N-TiO2 powder under visible light irradiation was analysed using UV-Vis spectrophotometry. The N-TiO2 powder was incorporated into a dental resin and the photocatalytic activity assessed using a dye under both visible light and dark conditions. Using XTT assay to measure the cellular metabolic activity, the antibacterial properties of the N-TiO2 /resin composite discs were tested using Streptococcus mutans. ResultsDoping nitrogen of TiO2 resulted in a band gap shift towards the visible light spectrum, which enabled the powder to release reactive oxygen species when exposed to visible light. When incorporated into a dental resin, the N-TiO2/resin composite still demonstrated sustained release of reactive oxygen species, maintaining its photocatalytic activity and showing an antibacterial effect towards Streptococcus mutans under visible light conditions. SignificanceN-TiO2 filled resin composite shows great promise as a potential aesthetic resin based adhesive for orthodontic bonding.

Cold Crystallization Kinetics and Thermal Degradation of PLA Composites with Metal Oxide Nanofillers

Poly(lactic acid) (PLA) nanocomposites with antimicrobial fillers have been increasingly explored as food packaging materials that are made of a biobased matrix and can minimize food loss due to spoilage. Some of the most commonly studied fillers are zinc oxide (ZnO), titanium dioxide (TiO2), and silver nanoparticles (AgNPs). In this work, nanocomposites with 1 wt.% of each filler were prepared by melt mixing. An extensive study of thermally stimulated processes such as crystallization, nucleation, degradation, and their kinetics was carried out using Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). In detail, non-isothermal cold crystallization studies were performed with DSC and polarized light microscopy (PLM), and kinetics were analyzed with multiple equations. The activation energy of the non-isothermal cold crystallization was calculated with the methods of Kissinger and Friedman. The latter was used to also determine the Hoffman–Lauritzen parameters (Kg and U*) by applying the Vyazovkin method. Additionally, effective activation energy and kinetic parameters of the thermal decomposition process were determined by applying the isoconversional differential method and multivariate non-linear regression method. According to TGA results, metal oxide nanofillers affected the thermal stability of PLA and caused a decrease in the activation energy values. Moreover, the fillers acted as heterogenous nucleating agents, accelerating the non-isothermal crystallization of PLA, thus reducing its activation energy. It can be concluded that metal oxide nanofillers catalytically affect the thermal degradation and crystallization of PLA samples.

Parametric optimization of yield percent of chitosan extracted from fish scale (Labeo rohita) through central composite design approach

Fish scales have been extensively reported as waste material that takes a lot of time to degrade, causing environmental pollution. This work has been substantiated to summarize a sequence of chemical processes (demineralization, deproteinization, and deacetylation) used for the extraction of useful product like chitosan from fish scale (Labeo rohita). The obtained chitosan have been efficiently characterized by SEM, FTIR, XRD, TGA, XRF, and proximate analysis. The small particle size (3.3748 µm) and the high surface area (4.046 m2 /g) of the produced cost-effective chitosan (0.26 USD/g) have justified its applicability as an antimicrobial filler. The degree of deacetylation have been reported to be 52.11% along with a high capacity of water binding (160%) and fat binding (457%), indicating its biodegradable nature. The individual effect of the essential parameters like deacetylation time, deacetylation temperature, and amount of NaOH added, influencing the yield percent have been studied using the central composite design approach of response surface methodology. The maximum yield percent have been reported to be 29.63% for the optimized conditions of 4.48% of NaOH content, 6.624 hr deacetylation time, and 58.2°C deacetylation temperature.

Antibacterial and antifungal properties of clear coating film containing silver–cytokinin complex as a filler

A silver–cytokinin complex filler was synthesized by a mild thermal process; then, the complex was mixed with an aqueous emulsion paint as an antimicrobial filler. Coating films were prepared by a typical method using 0.254 mm applicator. The results of antibacterial activity measurements indicated that the films exhibited strong activities against Escherichia coli and Staphylococcus aureus. Values of the antibacterial activity (n = 3) were 5.7 and 4.9, respectively. As for the mixture of five kinds of fungi, after cultivation (n = 5), no colony growth on the film surface was observed by microscopy. From the appearance of the film surfaces, it was revealed that the silver–cytokinin complex filler for emulsion paints possessed better paintability and transparency compared to a commercialized paint filler.

Mechanical and Antimicrobial Polyethylene Composites with CaO Nanoparticles.

Low-density polyethylene composites containing different sizes of calcium oxide (CaO) nanoparticles were obtained by melt mixing. The CaO nanoparticles were synthesized by either the sol-gel or sonication methods, obtaining two different sizes: ca. 55 nm and 25 nm. These nanoparticles were used either as-synthesized or were modified organically on the surface with oleic acid (Mod-CaO), at concentrations of 3, 5, and 10 wt% in the polymer. The Mod-CaO nanoparticles of 25 nm can act as nucleating agents, increasing the polymer’s crystallinity. The Young’s Modulus increased with the Mod-CaO nanoparticles, rendering higher reinforcement effects with an increase as high as 36%. The reduction in Escherichia coli bacteria in the nanocomposites increased with the amount of CaO nanoparticles, the size reduction, and the surface modification. The highest antimicrobial behavior was found in the composites with a Mod-CaO of 25 nm, presenting a reduction of 99.99%. This strong antimicrobial effect can be associated with the release of the Ca2+ from the composites, as studied for the composite with 10 wt% nanoparticles. The ion release was dependent on the size of the nanoparticles and their surface modification. These findings show that CaO nanoparticles are an excellent alternative as an antimicrobial filler in polymer nanocomposites to be applied for food packaging or medical devices.

Constructing a Contact-Active Antimicrobial Surface Based on Quarternized Amphiphilic Carbonaceous Particles against Biofilms.

Although contact-active antimicrobial surfaces (CAASs) are efficient, persistent, and safe in inhibiting bacterial adhesion and biofilm formation and much more desirable for applications in the fields ranging from industry to medical devices than others, the intrinsic defects, such as time and cost consumption and uncertainty in the stable immobilization of biocides, of previously established strategies affect their scaling-up preparations. Herein, a CAAS containing amphiphilic carbonaceous particles (ACPs), quarternized polyethyleneimine (QPEI), and thermoplastic polyurethane (TPU) was constructed by a carrier dispersion strategy. Its procedures included the immobilization of QPEI onto ACPs (ACPs-QPEI) and the incorporation of these modified particles into TPU. Its contact-medicated biocidal activity and other properties mentioned above were confirmed by in vitro/in vivo studies. As a crucial component of this surface, ACPs-QPEI showed good amphiphilic nature and strong antimicrobial activity. Its uniform incorporation not only endowed the TPU membrane with strong antimicrobial activity but also enlarged its strength and hydrophilicity at a proper dosage range. Its lethal dosages for 106 cfu mL-1 of Staphylococcus aureus, Escherichia coli, Candida albicans, and MRSA were all below 0.1 mg mL-1. Their amphiphilic nature would enable them to be compatible with different polarities of polymers theoretically, which means that much more CAASs could be prepared using this antimicrobial filler. The strategy was facile and feasible and might open an avenue for CAAS construction and applications.

Release of silver from silver doped PET bottles

• Production of silver-doped PET containers. • Release of Ag + from them was depended on percentage of antimicrobial filler, temperature and acidic strength of simulant. • Ag + release into distilled water was not detected for nanosilver-doped PET containers. • Diffusion coefficients of Ag + in PET were observed to be between 3.2 × 10 −17 and 1.7 × 10 −15 cm 2 /s. • By enhancing the ratio of surface to filling volume, a higher silver content in the solution was achieved. Development of active packaging based on polymers doped with silver has gained increasing interest. PET bottles were produced by injection and stretch blow molding under addition of silver phosphate (Ag 3 PO 4 ) glass at 3 % and 10 % (w/w) and of AgPURE masterbatch at 10 % (w/w) which contained 6500 ppm silver nanoparticles (AgNPs). These bottles underwent release tests. Silver released into distilled water, 0.5 % and 3 % (w/w) acetic acid was quantified using inductively coupled plasma mass spectrometry (ICP-MS). The amount of silver released ranged from 2 μgL −1 to 72 μgL −1 after 10 days at either 21 °C or 43 °C. For PET bottles containing AgNPs no release of silver was detected. Release was dependent on percentage of antimicrobial filler in the polymer, temperature, and acidic strength. Diffusion coefficients of silver ion (Ag + ) in PET were observed to be between 3.2 × 10 −17 and 1.7 × 10 −15 cm 2 /s. Bottles containing 3% (w/w) did not exceed the proposed specific migration level of 0.05 mg Ag per kg food, whereas bottles containing 10 % (w/w) did.

Current perspectives and the future of Candida albicans-associated denture stomatitis treatment.

Denture stomatitis (DS) is a multifactorial disease, but the proliferation of Candida albicans (C. albicans) is the main causative factor. Different modalities have been suggested for the prevention and treatment of DS. Among the different approaches that have been implemented to inhibit and control DS there are the topical application of antifungal agents, the surface modification of the denture base and the incorporation of antimicrobial agents into the denture base material. Antifungal agents can effectively control DS, but the recurrence of the disease is common. Accordingly, it has been suggested that coating the surface of the acrylic denture base may result in a decreased fungal adhesion. In recent years, nanotechnology has dominated the research, and several nanoparticles have demonstrated antifungal effects. Therefore, the aim of this article was to review the antifungal effects of the different methods that have been suggested for the prevention and/or control of DS as well as the antimicrobial activity of denture base acrylic resin additives, including nanoparticles. Studies reporting the incorporation of antifungal/antimicrobial agents into the polymethyl methacrylate (PMMA) denture base were included in this review. The PubMed, Web of Science, Google Scholar, and Scopus databases were searched for the articles published between January 2000 and December 2018 using the following key words: dental prosthesis, denture stomatitis, candidiasis, antifungal agents, biofilm formation, polymethyl methacrylate, and PMMA. The antimicrobial material incorporated into the resin may have a superior effect in preventing DS over simply coating the surface of the denture base. However, some antimicrobial fillers can have adverse effects on the physical and mechanical properties of the denture base resin.

Thermo-mechanical and antimicrobial properties of natural rubber-based polyurethane nanocomposites for biomedical applications

A polyester-type polyurethane (PU) was prepared using hydroxyl-terminated natural rubber (HTNR) as the soft polymer segments, 4,4-methylene dicyclohexyl diisocyanate (H12MDI) as the hard segments and 1,4-butane diol (BDO) as a chain extender. A simple one-shot bulk polymerization method using tetrahydrofuran (THF) as the solvent was chosen. The molar ratio of (H12MDI:HTNR:BDO) was fixed at 1.05:0.5:0.5. The pristine PU and its composite films with titanium nanoparticles (TiO2), silver nanoparticles (AgNPs) and benzoic acid (BA) were prepared with a constant 0.5 wt% loading of the antimicrobial fillers. The pristine PU and PU composite films were obtained by solution casting and drying at 60 °C in a vacuum oven. The effects of the antimicrobial fillers on the physical structure, mechanical properties, thermal properties, and antimicrobial activities were investigated. The SEM images showed that TiO2 and AgNPs aggregated. The aggregates reduced the films’ tensile strength as they obstructed the transfer of mechanical loads from PU matrix to the dispersed fillers. In contrast, BA was clearly well dispersed in the matrix giving much better mechanical properties (12 MPa tensile strength and 278% strain at break) and the PU–BA films were transparent. The PU–BA composites appear promising for biomedical applications.