MMT-supported Ag nanoparticles for chitosan nanocomposites: Structural properties and antibacterial activity

Chitosan-based film incorporated with silver-loaded organo-bentonite or organo-bentonite: Synthesis and characterization for potential food packaging material

Biopolymer-clay composite films were synthesized and characterized for food packaging material. The synthesis was conducted in two stages. Cetrimonium bromide-modified bentonite (CTAB-bentonite) was first exchanged with Ag ions to obtain Ag-CTAB-bentonite. Biopolymer-clay composite films were then performed by a solution-casting method between chitosan (biopolymer) and Ag-CTAB-bentonite or between chitosan and CTAB-bentonite. Different weights of CTAB-bentonite (3% and 5% wt.) and Ag-CTAB-bentonite (3% and 5% wt.) were used during the second stage. The resultant films were characterized by X-ray diffraction analysis, Fourier transform infrared spectroscopy, scanning electron microscope coupled with energy dispersive X-ray spectroscopy, atomic force microscopes, thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis, optical measurement, and others (moisture content, swelling behavior, water solubility, antibacterial, shredded carrot preservation, and biodegradability). Results indicated that the properties (thermal stability, thermomechanical ability, UV-visible light barrier, shredded carrot preservation) of the chitosan-based film incorporated with the synthesized composites were enhanced compared to those of the CS film. The CS/(CTAB-bentonite)-3% and CS/(Ag-CTAB-bentonite)-3% films exhibited antibacterial properties against Escherichia coli, Salmonella enterica subp. enterica, Staphylococcus aureus, and Listeria monocytogenes. The chitosan-based film reinforced with the two prepared composites can be potential for food preservation and packaging.

Water-triggered shape memory cellulose / sodium alginate / montmorillonite composite sponges for rapid hemostasis

Uncontrollable bleeding caused by severe trauma is life-threatening. Therefore, it is of great significance to develop hemostatic materials that meet the rapid hemostasis of wounds. In this study, a water-triggered shape memory carboxylated cellulose nanofiber/sodium alginate/montmorillonite (CNSAMMTCa) composite hemostatic sponge was prepared, which can promote coagulation by concentrating the blood and activating intrinsic pathway. The anisotropic three-dimensional porous structure formed by directional freeze-drying technology improved the performance of composite sponges which showed good prospects in rapid hemostasis. The results showed that CNSAMMTCa composite sponge had good porous structure, water absorption ability, cytocompatibility and blood cell aggregation capacity. Simultaneously, we confirmed that CNSA3MMT2Ca has best coagulation performance in the mouse censored bleeding model and liver rupture bleeding model. Therefore, CNSAMMTCa composite hemostatic sponge is a safe and efficient rapid hemostatic material which is expected to become an alternative material for clinical hemostatic materials.

Establishment and inactivation of mono-species biofilm in a semipilot-scale water distribution system using nanocomposite of silver nanoparticles/montmorillonite loaded cationic chitosan

This study presents a novel approach in the synthesis and characterization of nanocomposites comprising cationic chitosan (CCS) blended with varying concentrations of silver nanoparticles/montmorillonite (AgNPs/MMT). AgNPs/MMT was synthesized using soluble starch as a reducing and stabilizing agent. Subsequently, nanocomposites, namely CCS/AgMMT-0, CCS/AgMMT-0.5, CCS/AgMMT-1.5, and CCS/AgMMT-2.5, were developed by blending 2.5 g of CCS with 0, 0.5, 1.5, and 2.5 g of AgNPs/MMT, respectively, and the corresponding nanocomposites were prepared using ball milling technique. Transmission electron microscopy (TEM) analysis revealed the formation of nanocomposites that exhibiting nearly spherical morphologies. Dynamic light scattering (DLS) measurements displayed average particle sizes of 1183 nm, 131 nm, 140 nm, and 188 nm for CCS/AgMMT-0, CCS/AgMMT-0.5, CCS/AgMMT-1.5, and CCS/AgMMT-2.5, respectively. The narrow polydispersity index (~0.5) indicated uniform particle size distributions across the nanocomposites, affirming monodispersity. Moreover, the zeta potential values exceeding 30 mV across all nanocomposites that confirmed their stability against agglomeration. Notably, CCS/AgMMT-2.5 nanocomposite exhibited potent antibacterial and antibiofilm properties against diverse pipeline materials. Findings showed that after 15 days of incubation, the highest populations of biofilm cells, Pseudomonas aeruginosa biofilm, developed over UPVC, MDPE, DCI, and SS, with corresponding HPCs of 4.79, 6.38, 8.81, and 7.24 CFU/cm2. The highest cell densities of Enterococcus faecalis biofilm in the identical situation were 4.19, 5.89, 8.12, and 6.9 CFU/cm2. The nanocomposite CCS/AgMMT-2.5 exhibited the largest measured zone of inhibition (ZOI) against both P. aeruginosa and E. faecalis, with measured ZOI values of 19 ± 0.65 and 17 ± 0.21 mm, respectively. Remarkably, the research indicates that the youngest biofilm exhibited the most notable rate of inactivation when exposed to a dose of 150 mg/L, in comparison to the mature biofilm. These such informative findings could offer valuable insights into the development of effective antibiofilm agents and materials applicable in diverse sectors such as water treatment facilities, medical devices, and industrial pipelines.

The Recent Progress of the Cellulose-Based Antibacterial Hydrogel

Cellulose-based antibacterial hydrogel has good biocompatibility, antibacterial performance, biodegradability, and other characteristics. It can be very compatible with human tissues and degradation, while its good water absorption and moisturizing properties can effectively absorb wound exudates, keep the wound moist, and promote wound healing. In this paper, the structural properties, and physical and chemical cross-linking preparation methods of cellulose-based antibacterial hydrogels were discussed in detail, and the application of cellulose-based hydrogels in the antibacterial field was deeply studied. In general, cellulose-based antibacterial hydrogels, as a new type of biomaterial, have shown good potential in antimicrobial properties and have been widely used. However, there are still some challenges, such as optimizing the preparation process and performance parameters, improving the antibacterial and physical properties, broadening the application range, and evaluating safety. However, with the deepening of research and technological progress, it is believed that cellulose-based antibacterial hydrogels will be applied and developed in more fields in the future.

Synthesis, characterization, and antibacterial activity of chitosan-chelated silver nanoparticles

Bacterial infections pose a significant threat to human health and safety, necessitating the urgent resolution of the problem through the development and implementation of highly effective antibacterial agents. However, the emergence of multidrug-resistant bacteria has diminished the satisfactory effectiveness of antibacterial treatments. To overcome this obstacle, we developed effective antibacterial agents by chemical reduction for inhibiting bacterial proliferation and inducing membrane damage. Specifically, four different types of chitosan/Ag nanoparticle (CS-AgNPs-i) (i-1, 2, 3, 4) complexes were synthesized by varying the quantity of chitosan added during the synthesis process. We found that the amount of CS does not affect the morphology and size of CS-AgNPs-i, which remained at approximately 20 nm and all CS-AgNPs were mostly spherical. The zeta potential measurements indicated that the surface of CS-AgNPs carries a positive charge. Notably, elevating the chitosan concentration led to a more pronounced antibacterial impact, particularly evident in its interaction with the peptidoglycan layer on the bacterial surface. Our experimental results undeniably establish the potent antibacterial efficacy of CS-AgNPs against both Escherichia coli and Staphylococcus aureus. Employing live/dead bacterial staining, we reveal the marked capability of CS-AgNPs to effectively hinder bacterial proliferation. Furthermore, our experimental investigations revealed that CS-AgNPs possess broad-spectrum antimicrobial activity. The results of in vitro cytotoxicity experiments substantiated the high biocompatibility of CS-AgNPs with elevated chitosan loading. The study provides valuable insights into the development of nano-antibacterial agents that exhibit significant potential as a substitute to replace traditional antibiotics for medical applications.

A Review on Montmorillonite-Based Nanoantimicrobials: State of the Art

One of the crucial challenges of our time is to effectively use metal and metal oxide nanoparticles (NPs) as an alternative way to combat drug-resistant infections. Metal and metal oxide NPs such as Ag, Ag₂O, Cu, Cu₂O, CuO, and ZnO have found their way against antimicrobial resistance. However, they also suffer from several limitations ranging from toxicity issues to resistance mechanisms by complex structures of bacterial communities, so-called biofilms. In this regard, scientists are urgently looking for convenient approaches to develop heterostructure synergistic nanocomposites which could overcome toxicity issues, enhance antimicrobial activity, improve thermal and mechanical stability, and increase shelf life. These nanocomposites provide a controlled release of bioactive substances into the surrounding medium, are cost effective, reproducible, and scalable for real life applications such as food additives, nanoantimicrobial coating in food technology, food preservation, optical limiters, the bio medical field, and wastewater treatment application. Naturally abundant and non-toxic Montmorillonite (MMT) is a novel support to accommodate NPs, due to its negative surface charge and control release of NPs and ions. At the time of this review, around 250 articles have been published focusing on the incorporation of Ag-, Cu-, and ZnO-based NPs into MMT support and thus furthering their introduction into polymer matrix composites dominantly used for antimicrobial application. Therefore, it is highly relevant to report a comprehensive review of Ag-, Cu-, and ZnO-modified MMT. This review provides a comprehensive overview of MMT-based nanoantimicrobials, particularly dealing with preparation methods, materials characterization, and mechanisms of action, antimicrobial activity on different bacterial strains, real life applications, and environmental and toxicity issues.

AuNP/Chitosan Nanocomposites Synthesized through Plasma Induced Liquid Chemistry and Their Applications in Photothermal Induced Bacteria Eradication

In this work, a facile direct current atmospheric pressure micro-plasma (APM) technology was deployed for the synthesis of functional gold nanoparticle/chitosan (AuNP/CS) nanocomposites for the first time. Different experimental parameters, such as metal salt precursor concentration and chitosan viscosity, have been investigated to understand their effects on the resulting nanocomposite structures and properties. The nanocomposites were fully characterized using a wide range of material characterization techniques such as UV–vis, transmission electron microscope (TEM), Fourier transform infrared (FTIR) spectra and X-ray photoelectron spectroscopy (XPS) analyses. Potential reaction pathways have been proposed for the nanocomposite synthesis process. Finally, potential of the synthesized nanocomposites towards photothermal conversion and bacteria eradiation applications has been demonstrated. The results show that APM is a facile, rapid and versatile technique for the synthesis of AuNP/CS functional nanocomposites. Through this work, a more in-depth understanding of the multi-phase system (consisting of gas, plasma, liquid and solid) has been established and such understanding could shine a light on the future design and fabrication of new functional nanocomposites deploying the APM technique.

Preparation and application of silver/chitosan-sepiolite materials with antimicrobial activities and low cytotoxicity

Antimicrobial materials can prevent microbial infection and affect the beauty and structure of interior walls. Herein, a hybrid material silver/chitosan-sepiolite (Ag/5CTs-Sep) with antimicrobial activities was prepared via impregnation. Its antimicrobial properties were investigated via the disk diffusion method. Results showed that the width of inhibition zone of Ag/5CTs-Sep against Staphylococcus aureus (S. aureus), Escherichia coli (E. coli) and Aspergillus niger reached 58.15, 32.95 and 35.18 mm, respectively. The Sep was a suitable carrier for increasing thermal stability and antimicrobial durability, and chitosan improved the dispersion of silver to enhance antimicrobial activities. In addition, characterization indicated that the modification of Sep by CTs can promote the formation of lattice oxygen in Ag/5CTs-Sep, which can induce a high reactive oxygen species (ROS) content, causing the death of microbials. The antifungal mechanism revealed that the death of Aspergillus niger was due to Ag/5CTs-Sep that induced the production of high ROS level and damaged cell membrane. Moreover, Ag/5CTs-Sep possessed low cytotoxicity, and an applied test of the water-based coatings showed that the addition of Ag/5CTs-Sep could both effectively inhibit microorganisms and meet the performance standards for water-based coatings. This work may provide new guidance for the design and application of antibacterial materials.

Cytocompatibility / Antibacterial Activity Trade-off for Knittable Wet-Spun Chitosan Monofilaments Functionalized by the In Situ Incorporation of Cu2+ and Zn2

The wet spinning of cytocompatible, bioresorbable, and knittable chitosan (CTS) monofilaments would be advantageous for a variety of surgical applications. The complexation capacity of chitosan with Cu²⁺ or Zn²⁺ can be leveraged to enhance its antibacterial activity, but not at the expense of cytocompatibility. In this work, a wet-spinning process was adapted for the in situ incorporation of Cu²⁺ or Zn²⁺ with chitosan dopes to produce monofilaments at different drawing ratios (τ_tot) with various cation/glucosamine molar ratios, evaluated in the fibers (r_Cu,f and r_Zn,f). Cytocompatibility and antibacterial activity of wet-spun monofilaments were, respectively, quantified by in vitro live-dead assays on balb 3T3 and by different evaluations of the proliferation inhibition of Staphylococcus epidermidis (Gram+) and Escherichia coli (Gram-). Knittability was tested by a specific tensile test using a knitting needle and evaluated with an industrial knitting machine. It was found that r_Cu,f = 0.01 and r_Zn,f = 0.03 significantly increase the antibacterial activity without compromising cytocompatibility. Wet spinning with τ_tot = 1.6 allowed the production of knittable CTS-Cu monofilaments, as confirmed by knitting assays under industrial conditions.

Functionalization and Antibacterial Applications of Cellulose-Based Composite Hydrogels

Pathogens, especially drug-resistant pathogens caused by the abuse of antibiotics, have become a major threat to human health and public health safety. The exploitation and application of new antibacterial agents is extremely urgent. As a natural biopolymer, cellulose has recently attracted much attention due to its excellent hydrophilicity, economy, biocompatibility, and biodegradability. In particular, the preparation of cellulose-based hydrogels with excellent structure and properties from cellulose and its derivatives has received increasing attention thanks to the existence of abundant hydrophilic functional groups (such as hydroxyl, carboxy, and aldehyde groups) within cellulose and its derivatives. The cellulose-based hydrogels have broad application prospects in antibacterial-related biomedical fields. The latest advances of preparation and antibacterial application of cellulose-based hydrogels has been reviewed, with a focus on the antibacterial applications of composite hydrogels formed from cellulose and metal nanoparticles; metal oxide nanoparticles; antibiotics; polymers; and plant extracts. In addition, the antibacterial mechanism and antibacterial characteristics of different cellulose-based antibacterial hydrogels were also summarized. Furthermore, the prospects and challenges of cellulose-based antibacterial hydrogels in biomedical applications were also discussed.

Silver-sepiolite (Ag-Sep) hybrid reinforced active gelatin/date waste extract (DSWE) blend composite films for food packaging application

In this study, date syrup waste extract (DSWE) (15 wt%) and different content of silver doped sepiolite hybrid (Ag-Sep, 0.25-3 wt%) were incorporated into gelatin matrix to develop a series of active composite packaging films. Incorporating 2 wt% of Ag-Sep increased the modulus of blend film by 98% compared to unmodified gelatin/DSWE blend film. The active gelatin composite film exhibited superior active compounds migration to aqueous food simulants. Besides, Ag-Sep provided a tortuous pathway to the composite film, resulting in high 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical inhibition efficiency (91%) and slow-release kinetics of active compounds to the food simulant. The Ag-Sep hybrid was improved the antimicrobial property of the gelatin/DSWE blend film against both gram-negative and gram-positive microbes. Thus, this study demonstrated that the Ag-Sep hybrid exhibits significant properties in the active gelatin composite films, implying that this hybrid could be an effective additive for various active packaging films.

Investigation of Bioaccumulation and Human Health Risk Assessment of Heavy Metals in Crayfish (Procambarus clarkii) Farming with a Rice-Crayfish-Based Coculture Breeding Modes

Due to the rapid development of the crayfish (Procambarus clarkii) industry in Chinese catering, people are paying more attention to the bioaccumulation of heavy metals in crayfish. To evaluate the health risks associated with the consumption of crayfish, nine types of heavy metals in both crayfish and abdominal muscles of crayfish were investigated. Crayfish samples were collected from rice-crayfish-based coculture breeding modes from different areas located in the middle and lower reaches of the Yangtze River. The average concentrations of heavy metals in the whole crayfish were much higher than the abdominal muscle of crayfish. The estimated daily intake (EDI) of heavy metals in the abdomen of crayfish was calculated to assess the noncarcinogenic risk and the overall noncarcinogenic risk including the target hazard quotient (THQ), the hazard index (HI) and carcinogenic risk (CR). The results of the present study showed that the consumption of crayfish may not present an obvious health risk to human associated with heavy metals. However, the THQ values of As in the abdominal muscles of crayfish for adults in EnShi (ES) and children in JiaYu (JY) should be of concern due to the higher contribution to the potential health risks of crayfish compared to other metals. Through X-ray photoelectron spectroscopy (XPS) detection of heavy metal As, it is found that As in crayfish culture environment mainly exists in the form of As3+.Therefore, the quality and quantity of crayfish consumption should be moderated to prevent the bioaccumulation of As. The results indicate that crayfish cultured in different areas may have similar pollution levels and/or emissions from the same pollution sources.

Structure, physicochemical properties, and adsorption performance of the ethyl cellulose/bentonite composite films

Ethyl cellulose (EC) was filled with bentonite (Bent) particles by mechanical dispersion to produce composite film materials that were studied using various methods. According to X-ray diffraction (XRD) analysis, the inter-chain separation length was larger in EC/Bent composite then those in pure polymer. Infrared spectrometry indicated a formation of hydrogen bonds between the hydroxyl groups of EC and the silanol groups of clay. Tests showed an increase in tensile strength of the polymer material (by 35-40%) when doped with bentonite. It was found that modification of polymer with bentonite resulted in increasing of the adsorption efficiency of methylene blue (MB): the equilibrium concentration of MB ions in adsorbent phase increased 2.5 times. The MB adsorption kinetics obeyed the pseudo-first-order mechanism. Isotherms were in good agreement with Langmuir model. For the composite, the maximum monolayer adsorption capacity was 4 times higher than that for pure polymer.

Mesoporous silica nanoparticles as carriers of active agents for smart anticorrosive organic coatings: a critical review

Mesoporous silica nanoparticles (MSN) have attracted increasing interest for their applicability as smart nanocarriers of corrosion inhibitors, due to their porous structure, resistance to main corrosive environments and good compatibility with polymer coatings. In this review, the main synthetic routes to obtain MSN with tailored textural properties, the design of different loading and stimuli-induced release strategies, the development of advanced organic nanocomposite coatings with MSN and the validation of their anticorrosive performances are reviewed and compared. Through a critical analysis of the literature, the most promising research trends and perspectives to exploit the highly interesting properties of MSN in advanced organic coatings are proposed.

Hybrid levan–Ag/AgCl nanoparticles produced by UV-irradiation: properties, antibacterial efficiency and application in bioactive poly(vinyl alcohol) films

Hybrid Ag/AgCl nanoparticles with high antibacterial activity were synthesised using bacterial levan.

Facile synthesis of Ag nanoparticles-loaded chitosan antibacterial nanocomposite and its application in polypropylene

The development of environmental-friendly antibacterial agents with high efficiency and low cost has become the focus of attention. In this work, the Ag nanoparticles doped into chitosan (Ag NPs-CS) were synthesized by a green and facile method, and the samples were characterized by UV-Vis spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The antibacterial tests implied that Ag NPs-CS obtained from glucose (G-Ag NPs-CS) exhibited the excellent antimicrobial activities against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) microbes. Besides, the utilization of antibacterial agents in polymeric materials plays an significant role in healthy living. The aim is to impart the antibacterial properties and maintain/improve the mechanical properties. Therefore, the G-Ag NPs-CS with 5 wt% Ag was chosen as the optimal additive to endow polypropylene with antimicrobial activity via a simple melt blending method. The results demonstrated that the suppression of bacteria proliferation was enhanced with increasing the amount of antibacterial agent, and the microorganisms were almost killed when the content reached to 8 wt%. Meanwhile, the considerable improvement in elastic modulus and impact strength along with a slight decrease of elongation at break provided the evidence that Ag NPs-CS/PP nanocomposites were the promising candidate for practical applications.

Antimicrobial activity of endodontic sealers and medications containing chitosan and silver nanoparticles against Enterococcus faecalis

BACKGROUND

The main microorganism associated with the failure of endodontic treatments is Enterococcus faecalis. Although several endodontic therapeutics have demonstrated antimicrobial activity against E. faecalis, the antimicrobial effectiveness of chitosan (CsNPs) and silver nanoparticles (AgNPs) included into conventional endodontic sealers for endodontic therapies is still unclear.

AIM

The objective of this study was to evaluate the antibacterial activity increment (AAI) of endodontic sealers containing CsNPs and AgNPs as well as some chemical components against E. faecalis by direct contact assays.

METHODS

CsNPs and AgNPs were synthesized by reduction and ionic gelation methods, respectively. Nanoparticles were characterized by dynamic light scattering and energy dispersive X-ray analysis. The bactericidal activity was tested on monolayers on agar plates and collagen membrane surface assays against E. faecalis.

RESULTS

The size of CsNPs was 70.6±14.8 nm and zeta potential was 52.0±5.4 mV; the size of AgNPs was 54.2±8.5 nm, and zeta potential was -48.4±6.9 mV. All materials, single or combined, showed an AAI, especially when CsNPs, chlorhexidine (Chx), and the combination of CsNPs-Chx were added. However, the combination of CsNPs-Chx showed the highest (55%) AAI, followed by Chx (35.5%) and CsNPs (11.1%), respectively. There was a significant statistical difference in all comparisons (p < 0.05). Tubliseal (40%) and AH Plus (32%) sealants showed a higher AAI on E. faecalis in the monolayer test and collagen membrane assay analyzed by scanning electron microscopy.

CONCLUSIONS

Tubliseal and AH plus sealers combined with nanoparticles, especially CsNPs-Chx, could be used for conventional endodontic treatments in the control of E. faecalis bacteria.

Ultrasound-Assisted Preparation, Characterization, and Antibacterial Activity of Montmorillonite Modified by ε-Polylysine Hydrochloride

In this study, two types of antibacterial montmorillonites (Mt) were prepared using a facile method. The Mt modified with ε-polylysine hydrochloride (ε-PL) was named PL-Mt, while the Mt dually modified with dioctadecyl dimethylammonium chloride (D1821) and ε-PL was named PL-OMt. The results of the X-ray diffraction, Fourier-transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA) of the PL-Mt indicated that 30% ε-PL was the most suitable amount for intercalating the Mt. The particle size and distribution of the ε-PL in the solution demonstrated that the Mt d-value could not be further increased owing to the increasing ε-PL diameter. The result of the X-ray diffraction of PL-OMt displayed that ultrasonic treatment at 600 W facilitated ε-PL to intercalate into the OMt interlayer space. The PL-OMt prepared with ultrasonic treatment at 600 W exhibited antibacterial activity against Escherichia coli and Bacillus subtilis superior to that of the PL-OMt prepared with higher-power ultrasonic treatment. Thus, the addition of 30% ε-PL based on the dry Mt mass is the most suitable ratio for preparing PL-Mt, while ultrasonic treatment at 600 W is the most suitable for preparing PL-OMt. These findings may expand the application fields of ε-PL.

Water sorption, antimicrobial activity, and thermal and mechanical properties of chitosan/clay/glycerol nanocomposite films

Chitosan-based nanocomposites films with different clay loadings (0, 5, 10, 15 wt %), with (10, 20, 30 wt%) and without glycerol as plasticizer, were prepared by solution casting. The effects of the addition of clay and glycerol on the thermal, mechanical, water absorption, and antimicrobial activity properties of chitosan/clay nanocomposites films were investigated in this study. XRD results indicated that the intercalated structure was obtained in the chitosan/clay nanocomposites with and without glycerol. The thermal stability of the chitosan was significantly enhanced by the presence of clay and glycerol. It was found that the addition of clay into the chitosan improved significantly the tensile strength and tensile modulus. The highest values in strength and stiffness were achieved for the chitosal/clay nanocomposites with 5 wt% of clay and 20 wt% of glycerol. The addition of both clay and glycerol reduced drastically the ductility of chitosan. The best water resistance was obtained for the chitosan film containing 5 wt% of clay and 20 wt% of glycerol. The chitosan/clay nanocomposite film had potential for application of alternative food packing materials.

Cutaneous Melanoma in the Elderly: Review of a Growing Problem

Cutaneous melanoma (CM) causes more deaths than any other skin tumor, and incidence and mortality rates have risen in recent years, especially in patients of advanced age. There are differences in the biological behavior of CM tumors in the elderly as well as differential management of the disease, evidently influenced by such factors as limited life expectancy, the high incidence of concomitant conditions in older patients, and issues of quality of life unrelated to CM itself. We review relevant current literature on the epidemiology, etiology, pathogenesis, and immunology of CM as well as research on the clinical features, prevention, and management of these tumors in the elderly.

Levan-Capped Silver Nanoparticles for Bactericidal Formulations: Release and Activity Modelling

An environmentally friendly technique was used to produce levan-capped silver nanoparticles of about 30 nm (with a loading of 30%) that showed bactericide effect, for E. coli and B. subtilis. That effect was mathematically studied with a dose-response model (lethal dose of 12.4 ppm and 6.8 ppm respectively). These silver nanoparticles were subsequently introduced in a gel to create a silver release system with bacteria inhibition activity. Silver release from the gel and its bactericidal activity was theoretically studied to develop a unique model that is able to predict accurately both silver release and lethal dose for any type of bacteria. This model will be useful for performing predictions for future silver in gel applications.

Mussel-inspired nano-silver loaded layered double hydroxides embedded into a biodegradable polymer matrix for enhanced mechanical and gas barrier properties

In this paper, a facile, green and mussel-inspired method is presented to prepare silver loaded layered double hydroxides (Ag-LDHs@PDA and Ag-LDHs@TA–Fe(iii)) using a pre-synthesis polydopamine (PDA)/tannic acid (TA)–Fe(iii) layer as a nanoscale guide and PDA/TA itself as a reducing reagent to form uniform silver nanoparticles (AgNPs) on the surface of modified LDHs. Meanwhile, another kind of LDH, Ag-LDHs(PVP), was prepared via the direct reduction of the precursor [Ag(NH₃)₂]⁺ with polyvinyl pyrrolidone (PVP). And three kinds of Ag-LDHs/poly(ε-caprolactone) (PCL) nanocomposite were prepared by blending Ag-LDHs and pure PCL via a solution casting method to obtain homogeneous films. It is shown that the obtained AgNPs are distributed on the LDH surfaces uniformly. And the high loading and medium size of the AgNPs present in Ag-LDHs(PVP) give it the best antibacterial properties. However, compared with Ag-LDHs(PVP), the better dispersibilities of Ag-LDHs@PDA and Ag-LDHs@TA–Fe(iii) contribute to the greater aspect ratios of Ag-LDHs in the matrices, resulting in an increase in the number of tortuous paths for gas diffusion. Meanwhile, Ag-LDHs@PDA and Ag-LDHs@TA–Fe(iii) have stronger interactions with the PCL matrix, which is favorable for the existence of less interface defects in the matrix, resulting in an improvement in the mechanical and gas barrier properties. Therefore, mussel-inspired antibacterial Ag-LDHs/PCL nanocomposites show preferable mechanical and gas barrier properties.

A facile, green and mussel-inspired method is presented to prepare Ag loaded LDHs using a pre-synthesis PDA/TA–Fe(iii) layer as a nanoscale guide and PDA/TA itself as a reducing reagent to form uniform AgNPs on the surface of modified LDHs.

Current advancements in chitosan-based film production for food technology; A review

Chitosan is obtained from chitin, which could be considered to be the most abundant polymer after cellulose. Owing to these properties, chitosan alone or chitosan-based composite film production is attaining huge attention in terms of applications from researchers and industrialists coming from divergent fields. To enhance the biological (mainly antimicrobial and antioxidant) and physiological (mainly mechanical, thermal and barrier) attributes of the chitosan-based films, a vast medley of plant extracts and supporting polymers has been blended into chitosan films. Considering the up to date literature reports based on chitosan film production and applications, it can be stated that still, the research ratio is low in this field. Chitosan blend/composite films with specific properties (superhydrophobicity, excellent mechanical strength, acceptable barrier properties) can be produced only for specific applications in food technology. In the current review, we tried to summarize the advancements made in the last 5-7 years in the field of chitosan film technology for its application in the food industry.

Development of Nano-Antimicrobial Biomaterials for Biomedical Applications

Around the globe, there is a great concern about controlling growth of pathogenic microorganisms for the prevention of infectious diseases. Moreover, the greater incidences of cross contamination and overuse of drugs has contributed towards the development of drug resistant microbial strains making conditions even worse. Hospital acquired infections pose one of the leading complications associated with implantation of any biomaterial after surgery and critical care. In this regard, developing non-conventional antimicrobial agents which would prevent the aforementioned causes is under the quest. The rapid development in nanoscience and nanotechnology has shown promising potential for developing novel biocidal agents that would integrate with a biomaterial to prevent bacterial colonization and biofilm formation. Metals with inherent antimicrobial properties such as silver, copper, zinc at nano scale constitute a special class of antimicrobials which have broad spectrum antimicrobial nature and pose minimum toxicity to humans. Hence, novel biomaterials that inhibit microbial growth would be of great significance to eliminate medical device/instruments associated infections. This chapter comprises the state-of-art advancements in the development of nano-antimicrobial biomaterials for biomedical applications. Several strategies have been targeted to satisfy few important concern such as enhanced long term antimicrobial activity and stability, minimize leaching of antimicrobial material and promote reuse. The proposed strategies to develop new hybrid antimicrobial biomaterials would offer a potent antibacterial solution in healthcare sector such as wound healing applications, tissue scaffolds, medical implants, surgical devices and instruments.

Self-assembly fabrication, microstructures and antibacterial performance of layer-structured montmorillonite nanocomposites with cationic silica nanoparticles

Layer-structured montmorillonite nanocomposites containing cationic silica nanoparticles were fabricated for an enhancement in thermal stability and antibacterial performance.

Chitosan nanocomposites based on distinct inorganic fillers for biomedical applications

Chitosan (CHI), a biocompatible and biodegradable polysaccharide with the ability to provide a non-protein matrix for tissue growth, is considered to be an ideal material in the biomedical field. However, the lack of good mechanical properties limits its applications. In order to overcome this drawback, CHI has been combined with different polymers and fillers, leading to a variety of chitosan-based nanocomposites. The extensive research on CHI nanocomposites as well as their main biomedical applications are reviewed in this paper. An overview of the different fillers and assembly techniques available to produce CHI nanocomposites is presented. Finally, the properties of such nanocomposites are discussed with particular focus on bone regeneration, drug delivery, wound healing and biosensing applications.

Chitosan films incorporated with nettle (Urtica Dioica L.) extract-loaded nanoliposomes: II. Antioxidant activity and release properties

Chitosan films were loaded with NE nettle (Urtica dioica L.) extract (NE) at concentrations of 0, 0.5, 1 and 1.5%w/w in the free or nanoliposomal form to obtain active and nanoactive films, respectively. The antioxidant potential of the films containing NE-loaded nanoliposomes was decreased in comparison of free NE incorporated films. Diffusion of NE to soybean oil was enough to delay the induction of the oxidation of soybean oil stored for 60 days in contact with chitosan based films. Release studies indicated that the release rate of NE in 95% ethanol simulant significantly decreased by the nanoencapsulation of NE. The diffusion coefficient (D) for chitosan films containing 1.5%w/w of free and encapsulated NE at 25 °C was 18.80 and 3.68 × 10^-7 cm² s^-1, respectively. Moreover, the formation of nanoliposomes diminished the increasing effect of temperature on the release rate as when storage temperature increased from 4 °C to 40 °C.

Characterization of chitosan-nanoclay bionanocomposite active films containing milk thistle extract

Nowadays, bio-based and antioxidant active packaging is attracting significant attention as one of the preferred emerging technologies to prevent sensitive oxidation of foods. In this study, chitosan/nanoclay nanocomposite active films containing three different levels of sodium montmorillonite (MMT) (1, 3 and 5% w/w based on chitosan) and Silybum marianum L. extract (SME) (0.5, 1 and 1.5% v/v) were prepared. The obtained films were characterized in terms of structural, thermal, mechanical, and barrier properties as well as antioxidant behavior. X-ray diffraction patterns confirmed the exfoliated dispersion form of MMT nanolayers. Scanning electron microscopy images showed an increase in films' surface roughness by the addition of MMT. The results indicated that water vapor permeability and solubility of films reduced significantly (p<0.05) by incorporation of MMT and SME. The mechanical and optical properties of films were significantly affected by the content of MMT and SME (p<0.05). Antioxidant properties of the films also were improved by SME incorporation, suggesting that the formulated bionanocomposites could be considered as a promising antioxidant active packaging material.