Antibacterial Chitosan-Gelatin Microcapsules Modified with Green-Synthesized Silver Nanoparticles for Food Packaging

Silver nanoparticles(Ag NPs)are an effective antibacterial agent,but their application in food packaging is limited due to their easy agglomeration and oxidation.In this study,antibacterial microcapsules were fabricated using Ginkgo biloba essential oil(GBEO)as core material and chitosan and type B gelatin biopolymer as capsule mate-rials.These antibacterial microcapsules were then modified with green-synthesized Ag NPs,blended into the bio-polymer polylactic acid(PLA),and finally formed as films.Physicochemical properties and antibacterial activity against Escherichia coli(E.coli)and Staphylococcus aureus(S.aureus)were evaluated.Results showed that the prepared antibacterial PLA films exhibited excellent antibacterial activity against foodborne pathogens.Its TVC exceeded the limit value of 7 log CFU/g at 7 days compared with the 5 days of pure PLA films.Therefore,these films can extend the shelf life of grass carp fillets by 2–3 days under refrigeration.

Preparation of Gallic Acid-chitosan Copolymer and Its Antibacterial Activity against Staphylococcus Aureus and Escherichia Coli

To synthesize three different grafting ratios of gallic acid(GA)-chitosan(CS)copolymer by a free radical mediated grafting method,which is further applied to the field of antibacterial materials,crosslinking structures of the compound GA-CS copolymer were characterized,fully indicating that gallic acid is resoundingly grafted onto chitosan.The grafting ratios of three copolymers GA-CS are 45.71%(Ⅰ),36.12%(Ⅱ),and 18.96%(Ⅲ)were determined by UV-Vis spectrophotometer.The minimum inhibitory concentrations of three GA-CS copolymers are 30μg/mL against Escherichia coli and are ranged from 250 to 550μg/mL against Staphylococcus aureus.By counting viable bacterial colonies,it can be found that antibacterial property is preferable by increasing the grafting ratio of GA-CS copolymers.Findings of investigation on aforementioned bacteria experiment indicate that the CFU/mL values of GA-CS(Ⅰ,Ⅱ,Ⅲ)are 2.04×10^(6),7.56×10^(6),1.48×10^(7) to Staphylococcus aureus,and 2.96×10^(6),1.01×10^(7),2.14×10^(7) to Escherichia coli after 12 h treatment.In addition,the interaction process between GA-CS copolymer and bacteria can be observed through a transmission electron microscope.The specific manifestation is that the bacterial cell membranes are ruptured after being treated with the copolymer,which causes the cell contents to flow out,and the cell morphology is shrunk and out ofshape.

Effect of addition of chitosan to self-etching primer:antibacterial activity and push-out bond strength to radicular dentin

The purpose of this study was to evaluate the antibacterial activity of a modified self-etching primer incorporating chitosan and whether this modification affected the bond strength to radicular dentin.A modified self-etching primer was prepared by adding chitosan solutions at 0.03%,0.06%,0.12% and 0.25%（W/W） to RealSeal selfetching primer.RealSeal primer without chitosan was used as the control.The antibacterial activity of the modified self-etching primer was evaluated using the direct contact test against Enterococcus faecalis.The bonding ability of the RealSeal system to radicular dentin was evaluated using the push-out bond strength test.The modes of failure were examined under a stereomicroscope.Data were analyzed using analysis of variance（ANOVA） and Tukey’s test,with a P-value 〈 0.05 indicating statistical significance.The results showed that the antibacterial properties of the freshly prepared and aged modified self-etching primer incorporating chitosan exhibited potent antibacterial effect against Enterococcus faecalis compared with the unmodified primer.The RealSeal system with the aged modified self-etching primer incorporating chitosan showed no significant differences in the bond strength as compared with the control（P = 0.99）.The findings suggest that modified self-etching primer incorporating chitosan is a promising antibacterial primer which does not adversely affect the bond strength of the RealSeal system to radicular dentin.

Ultrastructural Analysis of Chitosan Antibacterial Activity against Clinical Isolates of <i>Staphylococcus aureus</i>and <i>Escherichia coli</i>

The continuous search for an antimicrobial agent led to the identification of potential antimicrobial biomaterials based on polymers naturals, such as chitosan (CS). However, the mechanism of action of antibacterial activity of CS for gram-positive and gram-negative bacteria was not completely elucidated. The aim of this work is to report the antibacterial activity of CS through ultrastructural analyses of the clinical isolates Staphylococcus aureus and Escherichia coli by Transmission Electron Microscopy. The CS has a bactericidal action against S. aureus and E. coli which alters its cellular ultrastructure, such as with collapsed cell walls, condensed chromatin and the increase of intracellulares structures like vacuoles and cell debris. In this way, the CS represents a potential model for the future design of antibacterial in order to control bacterial resistance of patients in hospital settings.

Preparation and Properties of Antibacterial Lyocell Fibers Containing Chitosan Derivative

The O-carboxymethyl chitosan sodium salt, NaCMCh, was initially synthesized and analyzed with better antibacterial activity than chitesan. Then NaCMCh was dissolved in the N-mcthylmorpholine-N-oxide, NMMO, solution with cellulose for spinning of the lyocell fiber. The results showed that the lyocell fibers modified with over 2 wt% NaCMCh has good antibacterial activity in against the E. coli and with NaCMCh content below 6 wt% has considerable mechanical properties.

In vitro antibacterial activity of Hibiscus rosa-sinensis flower extract against human pathogens

Objective:To access the in vitro antibacterial activity of Hibiscus rosa-sinensis(H.rosa-sinensis) flower extract against human pathogens.Methods:Antibacterial activity was evaluated by using disc and agar diffusion methods.The protein was run through poly acrylmide gel electrophoresis to view their protein profile.Results:The results showed that the cold extraction illustrates a maximum zone of inhibition against Bacillus suhtillis(B.suhtillis),Escherichia coli(E.coli) viz.,(17.00±2.91),(14.50±1.71)mm.followed by hot extraction against.E.coli.Salmonella sp.as(11.66 ±3.14),(10.60±3.09)mm.In methanol extraction showed a highest zone of inhibition recorded against B.suhtillis,E.coli as(18.86±0.18),(18.00±1.63) mm pursued by ethanol extraction shower) utmost zone of inhibition recorded against Salmonella sp.at(20.40±1.54) mm.The crude protein from flower showed a maximum inhibitory zone observed against Salmonella sp.,E.coli viz.,(16.55±1.16),(14.30±2.86)mm.The flower material can be taken as an alternative source of antibacterial agent against the human pathogens.Conclusions:The extracts of the H.rosasinensis art;proved to have potential antibacterial activity,further studies arc highly need for the drug development.

LOW MOLECULAR WEIGHT O-CARBOXYMETHYLATED CHITOSANS DERIVED FROM IRRADIATED CHITOSAN AND THEIR ANTIBACTERIAL ACTIVITY

Original chitosan with M-v of 2.7 x 10(5) was degraded by irradiation with gamma-rays and a series of low molecular weight O-carboxymethylated chitosans (O-CMCh) were prepared based on the irradiated chitosan. A kinetic model of the irradiation of chitosan was put forward. Results show that the irradiation degradation of chitosan obeys the rule of random degradation and the degree of deacetylation of irradiated chitosan is slightly raised. The antibacterial activity of O-CMCh is significantly influenced by its MW, and a suppositional antibacterial peak appears when M-v is equal to 2 x 10(5).

Chlorogenic acid loaded chitosan nanoparticles with sustained release property,retained antioxidant activity and enhanced bioavailability

In this study,chlorogenic acid(CGA),a phenolic compound widely distributed in fruits and vegetables,was encapsulated into chitosan nanoparticles by ionic gelation method.The particles exhibited the size and zeta potential of 210 nm and 33 mV respectively.A regular,spherical shaped distribution of nanoparticles was observed through scanning electron microscopy(SEM)and the success of entrapment was confirmed by FTIR analysis.The encapsulation efficiency of CGA was at about 59%with the loading efficiency of 5.2%.In vitro ABTS assay indicated that the radical scavenging activity of CAG was retained in the nanostructure and further,the release kinetics study revealed the burst release of 69%CGA from nanoparticles at the end of 100th hours.Pharmacokinetic analysis in rats showed a lower level of Cmax,longer Tmax,longer MRT,larger AUC0et and AUC0e∞for the CGA nanoparticles compared to free CGA.Collectively,these results suggest that the synthesised nanoparticle with sustained release property can therefore ease the fortification of food-matrices targeted for health benefits through effective delivery of CGA in body.

Development and assessment of a multifunctional chitosan-based coating applied on AZ31 magnesium alloy: Corrosion resistance and antibacterial performance against Klebsiella Pneumoniae

This work presents a simple method to functionalise the surface of AZ31 magnesium alloy by applying a duplex MgF_(2)/chitosan coating,which improves its corrosion resistance and provides it with some antibacterial performance.First,the effect of three chitosan solutions with different concentrations on the growth of the bacteria Klebsiella pneumoniae in nutritive medium(TSB)was evaluated by absorbance kinetics experiments,where the chitosan solution at 2%(m/V)was selected for the coating preparation.Before coating application,the AZ31 substrate was pretreated with hydrofluoric acid for 48 hours in order to form a MgF_(2)conversion layer.Subsequently,the coating was applied to the pretreated substrate through the dry-casting method.Samples of the alloy in each surface condition(bare,pretreated,and pretreated+coated with chitosan)were exposed to simulated body fluid(SBF)for 21 days at 37°C,with the solution renewed every 24 hours and the wastes stored.The surfaces were characterised by SEM-EDS,and XPS after the immersion tests,whereas the stored solutions were employed to measure the change in the Mg-ions concentration.Electrochemical impedance spectroscopy and potentiodynamic polarisation were performed in each surface condition to compare their corrosion resistance in SBF.The antibacterial activity of the functionalised surfaces was evaluated by the plate counting method and compared with bare samples.All results were correlated and demonstrate that the modified surface of AZ31 achieved a higher corrosion resistance when it was exposed to SBF,as well as a reduction of the bacterial growth during in vitro tests.

Preparation, Swelling and Antibacterial Behaviors of N-Succinyl Chitosan-g-Poly(Acrylic Acid-co-Acrylamide) Superabsorbent Hydrogels

Superabsorbent hydrogels were prepared successfully from N-succinyl chitosan grafted poly（acrylic acid-co-acrylamide）. The potassium persulfate（KPS）, N, N＇-methylenebisacrylamide（MBA） were used as the initiator and crosslinker, respectively. Fourier transform infrared spectroscopy（FTIR） and scanning electron microscopy（SEM） were used to confirm the porous network structure of superabsorbent hydrogel. The effects of reaction parameters on the swelling behaviors of the superabsorbent hydrogels were investigated. The results indicated that water absorbency increased first, and then decreased gradually with the increase in the contents of monomer（AA＋AM）, KPS, MBA or acrylamide. The product had excellent water absorbency of 1375 g/g in distilled water and 83 g/g in 0.9wt% NaCl solution. Simultaneously, the superabsorbent hydrogels were p H sensitive. The antibacterial activities of the hydrogels against Escherichia coli（E. coli） were improved effectively because of polyamidoamine（PAMAM） dendrimer absorbed in the hydrogels.

Preparation and Properties of Poly(amidoamine) Dendrimer/Quaternary Ammonium Chitosan Hydrogels

A novel quaternary ammonium chitosan hydrogel modified by poly（amidoamine）（PAMAM） dendrimer was prepared by using glutaraldehyde as a cross-linker. The hydrogel was characterized by Fourier transform infrared spectroscopy（FTIR） and scanning electron microscopy（SEM）. The results confirmed its highly porous three-dimensional network structure. The swelling test of hydrogel proved that it had excellent swelling and p H-sensitive properties. The increasing PAMAM content or quaternization degree led to the increase in swelling properties. And the hydrogel with lower cross-linking agent concentration or quaternary ammonium chitosan concentration exhibited better swelling properties. The antibacterial results indicated that with the increase in the PAMAM content, quaternary ammonium chitosan concentration or cross-linking agent concentration, the hydrogels showed better antibacterial activities against both Staphylococcus aureus（S. aureus） and Escherichia coli（E. coli）. Thus, the hydrogel could serve as a promising antibacterial material in the future.

Preparation and Characterization of Florfenicol/Chitosan-stearic Acid Polymer Nanomicelle and Its Antibiotic Properties

Amphiphilic CS-SA polymers were prepared using the SA modified by small molecule water-soluble chitosan, and CS-SA nanomicelles and FF/CS-SA nanomicelles were prepared by using CSSA polymers as the material with dialysis-ultrasound method. CS-SA polymers, CS-SA nanomicelles, and FF/CS-SA nanomicelles were characterized by FT-IR, TGA, and SEM. Results showed that the SA was grafted to the amino of CS by amide bond. CS-SA nanomicelles and FF/CS-SA nanomicelles were spherical, smooth without fold. The influence of different molar ratio of FF to CS-SA polymers on the encapsulation efficiency and drug-loading rate determined the best molar ratio that was 1：1.09. In vitro release experiments, drug release performance study found that hydrophobic drug releasing from FF/CS-SA nanomicelles presented sustainedrelease. In vitro bacteriostasis experiments, when the concentration was higher than 4.98 mg/mL, FF/CSSA nanomicelles had antibacterial action and a positive correlation with concentration. The results revealed that amphiphilic chitosan derivative nanomicelles were carriers with broad prospects, increasing solubility of hydrophobic drugs and presenting sustained release for hydrophobic drugs, which provided a new research idea for drug delivery and targeted drug delivery of hydrohobic drugs.

Cerium ions crosslinked sodium alginate-carboxymethyl chitosan spheres with antibacterial activity for wound healing

For wound healing,wound infection caused by bacteria is one of the important reasons that delay wound healing process.Therefore,it is very meaningful to develop a multifunctional wound dressing with antibacterial capability to accelerate wound healing.Sodium alginate(SA)and carboxymethyl chitosan(CMCS)are the most commonly used compositions in wound dressing,but their poor stability inhibits the further applications.Introducing CMCS and using cerium ions(Ce^(3+))to crosslink CMCS and SA to form SA-CMCS hybrid spheres by electrostatic spray method,can not only improve the stability of SA hydrogels,but also endow the spheres with excelle nt antibacterial properties due to the characteristics of Ce^(3+).The gradual release of Ce^(3+)from the SA-CMCS spheres can effectively inhibit the growth of Staphylococcus aureus(S.aureus)and Escherichia coli(E.coli).Combining the wound healing promotion ability of SA and CMCS,this kind of wound dressing can not only avoid wound infection caused by bacteria effectively,but also accelerate wound healing,thus it is an easily prepared material with potential applications in skin defect repair.

Bombyx Mori Chitosan Nanoparticles: Synthesis and Properties

A synthesis of nanochitosan from Bombyx mori chitosan with particle sizes of 20 - 100 nm was carried out. The antibacterial and immunological properties of synthesized nanochitosan were first studied. It was revealed that preparations based on nanochitosan have pronounced antibacterial activity, and are also able to significantly increase the immune response of the living system.

Evaluation of in-vitro antibacterial activity and anti-inflammatory activity for different extracts of Rauvolfia tetraphylla L.root bark

Objective:To assess the in-vitro antihacterial activity and anti-inflammatory activity of orally administered different extracts(Hydro-alcoholic,methanolic,ethyl acetate and hexane)of Rauvolfia tetraphylla(R.tetraphylla)root bark in Carrageetiaii induced acute inflammation in rats.Methods:In-vitro antibacterial activity was evaluated for extracts against four Gram positive and four Gram negative bacteria by using cylinder plate assay.Hydro-alcoholic extract(70%v/v ethanol)at 200,400 and 800 mg/kg doses and methanolic,ethyl acetate and hexane extracts at doses 100,200 and 400 mg/kg were tested for anti-inflammatory activity in Carrageenan induced rat paw oedema model and paw thickness was measured every one hour up to 6 hrs.Results:All extracts of R.tetraphylla root bark showed good zone of inhibition against tested bacterial strains.In Carrageenan induced inflammation model,hydro-alcoholic and methanolic extract of R.tetraphylla root bark at three different doses produced significant(P<0.00l)reduction when compared to vehicle treated control group and hexane,ethyl acetate extracts.Conclusions:In the present study extracts of R.tetraphylla root bark shows good in-vitro antibacterial activity and in-vivo anti-inflammatory activity in rats.

In Vitro Anti-Bacterial and Anti-Fungal Activities of Extracts from Different Parts of 7 Zingiberaceae Plants

This study aimed to explore the anti-bacterial and anti-fungal activities of extracts from different parts of plants in the Zingiberaceae family.The inhibitory rate,minimum inhibitory concentration(MIC),and minimum bactericidal concentration(MBC)of leaf and stem,and root and rhizome extracts from Alpinia katsumadai Hayata,Alpinia oxyphylla Miq×Alpinia henryi K.Schumann,Alpinia oblongifolia Hayata,Alpinia nigra(Gaertn.)Burtt,Amomum villosum Lour,Alpinia zerumbet(Pers.)Burtt.et Smith and Alpinia oxyphylla Miq were determined using the fungus cake method and double dilution method.The seven Zingiberaceae plants exhibited characteristic antibacterial activities against pathogenic bacteria and fungi.At a 1.5 mg mL^(−1),A.zerumbet root and rhizome extracts exhibited strong inhibitory activity against S.aureus and E.coli,with 83.23%and 79.62%,respectively.In addition,A.zerumbet leaf and stem extracts had an inhibitory rate of 90.85%against P.aeruginosa.At the same concentration,the leaf and stem,root and rhizome extracts of A.katsumadai had the best anti-bacterial effect against F.oxysporum,with inhibition rates of 84.46%and 84.73%,respectively.Moreover,A.katsumadai and A.zerumbet leaf and stem extracts had the most significant antibacterial effect against S.aureus,with a MIC of 0.063 mg mL^(−1).Thus,both A.katsumadai and A.zerumbet extracts had significant antibacterial activity.In addition,by comparing the inhibitory effect of extracts from different parts,it was found that the inhibitory rate and average inhibitory rate of extracts from leaf and stem were higher than those from root and rhizome.The chemical constituents of A.katsumadai and A.zerumbet,determined by the high-performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS),revealed that citric acid(CA),alpinetin,and pinocembrin(PNCB)were the functional constituents yielding the antibacterial activity.Overall,A.katsumadai and A.zerumbet have the potential to be developed as new plant fungicides and bactericides.

Precise quantification of the antibacterial activity of chitosan by NB medium neutralizer

In the present research,nutrient broth(NB)medium was identified to be able to neutralize the antibacterial activity of chitosan and its derivatives.Therefore,an improved test method independent of NB medium was proposed to precisely quantify the antibacterial effectiveness and efficiency of chitosan.The minimum bactericidal concentration(MBC)of chitosan was 60μg m L^(-1) against S.aureus and E.coli,and 0.01%(w/v)chitosan could kill 100%of bacteria within 3 min.From another point of view,the neutralizing efficiency of NB could be tripled by adding 25 g L^(-1) of sodium chloride.Then the neutralizing mechanism of NB medium was ascribed to flocculation between chitosan and protein.Adding extra sodium chloride could significantly reduce the size of floccules,and smaller floccules would lose the ability of binding with bacteria directly,showing higher neutralizing rate on the macro scale.

In vitro antioxidant and antimicrobial activity cycloart-23-ene-3β,25-diol(B2) isolated from Pongamia pinnata(L.Pierre)

Objective:To evaluate the in-vitro antioxidant and antimicrobial activity of cvcloart-23- ene-3β,25-diol(called as B2) isolated from stem bark of Pongamia pinnata.Methods:In vitro antioxidant activity of B2 was determined by methods for determination of Dl’PH radical scavenging,reducing power,superoxide anion radical scavenging,hydroxyl radical scavenging, hydrogen peroxide scavenging,metal chelating and nitric oxide radical scavenging at the doses of 20.40.60.80 and 100μg/mL,respectively.3 -tocopherol with same concentration was used as a standard antioxidant.In vitro antimicrobial activity of B2 was determined by cup plate method in different concentration range of 10-100μg/mL.Results:The results indicated that dose dependent%reduction against DPPH radical,reducing power,superoxide anion radical scavenging,hydroxyl radical scavenging,metal chelating,hydrogen peroxide scavenging and nitric oxide radical scavenging by B2 andβ-tocopherol.Conclusions:It is concluded that cycloart 23-ene-3β,25 diol(B2) showed dose dependent antioxidant activity.B2 showed more DPPH radical scavenging,reducing power,superoxide scavenging,hydroxyl radical scavenging, metal chelating scavenging,hydrogen peroxide radical scavenging and nitric oxide radical scavenging activity thanβ-tocopherol and in case of antimicrobial activity B2 exhibited broad-spectrum activ ity against bacteria and strong activity against yeast type of fungi.

GREEN SYNTHESIS OF ANTIBACTERIAL CHITOSAN FILMS LOADED WITH SILVER NANOPARTICLES

An eco-friendly chemical reduction method was successfully used for the preparation of chitosan （CTS） composite films loaded with silver nanoparticles （AgNPs） by self assembly method using poly（ethylene glycol） as both reducing and stabilizing agent. UV-Vis spectra of the prepared chitosan loaded silver nanoparticles （CTSLAg） films reveal that full reduction of silver ions to silver nanoparticles takes place at 90 ℃. The effect of reaction conditions on the silver nanoparticles formation was investigated using UV-Vis spectrophotometer. The morphology of the films was tested by scanning electron microscopy （SEM）. The DSC curves showed that the CTSLAg film had a favorable compatibility and heat stability. AgNPs were confirmed by XRD and UV-Vis spectroscopy. The TEM findings revealed that the silver nanoparticles synthesized were spherical in shape with uniform dispersal, and by increasing CTS：PEG ratio larger silver nanoparticles could be obtained. The results of antibacterial study reveal that the prepared nanoeomposite films exhibited potential inhibition.

In vitro prebiotic effects of seaweed polysaccharides

Although prebiotic activities of alginate and agar oligosaccharides isolated from seaweeds have been reported, it remains unknown whether seaweed polysaccharides have prebiotic activity. In this study, we isolated polysaccharides from four species of seaweeds, such as Grateloupia fi licina(GFP), Eucheuma spinosum(ESP), Ulva pertusa(UPP), and A scophyllum nodosum(ANP), and characterized their structures and prebiotic ef fects in vitro. The results showed that these polysaccharides were dif ferent in total sugar and sulfate contents as well as monosaccharide composition. GFP and ESP significantly promoted bifi dobacterium proliferation and 0.1% ESP and 0.4% GFP resulted in the highest proliferation rates of beneficial bacteria, whereas UPP and ANP inhibited the growth of beneficial bacteria at all tested concentrations(0.1%–0.5%). The different behaviors of the four seaweed-originated polysaccharides might be refl ected by differences in monosaccharide composition and structure. Therefore, polysaccharides isolated from GFP and ESP could be utilized as prebiotics. However, more studies must be carried out in vivo.