Chitosan-silver Nanocomposites Research Articles

Evaluation of the antiparasitic activity of the chitosan-silver nanocomposites in the treatment of experimentally infested pigeons with Pseudolynchia canariensis

This study aimed to evaluate the efficacy of chitosan-silver nanocomposites in the treatment of experimentally infested pigeons with Pseudolynchia canariensis (P. canariensis) with evaluation of different immunological parameters before and after treatment. Therefore, fourteen birds were divided into 2 groups; group1(infested group including 12 birds) which subdivided into 6 sub-groups experimentally infested pigeons 2 pigeons each, and five group of them were treated with chitosan-silver nanocomposites and sub-group number 6 was treated with deltamethrin while, group 2 including two pigeons were kept as control negative ones. P. canariensis flies distributed under the wing and /or under the tail in infested group and these pigeons showed significantly lower RBCs and higher WBCs than that in non-infested pigeons. The cell mediated immune response against experimentally infested pigeons with P. canariensis was studied. P. canariensis infestation in pigeons have a negative impact on pigeon’s blood parameters, increase TNF-α and IL-1β cytokines levels. This study cleared out the role of P. canariensis in the induction of a case of oxidative stress indicated by high level of nitric oxide and malondialdehyde (MDA) with low antioxidant capacity in shape of reduced zinc concentration in the sera of experimentally infested pigeon. Chitosan-silver nanocomposite has a promising effect in the elimination of P. canariensis infestation in pigeons.

Characterization and Antifungal Efficacy of Biogenic Silver Nanoparticles and Silver–Chitosan Nanocomposites

The present study aimed for a comparative study of green protocol for the biogenic synthesis of silver nanoparticles (AgNPs) and silver-chitosan nanocomposites (Ag-CS-NCs), characterization, and comparative evaluation of antifungal and anti-aflatoxin B1 activity potentials of both nanoparticles (NPs). The cell-free culture filtrate (CFF) of Aspergillus terreus (KC462061) was utilized to biogenic synthesis AgNPs and Ag-CS-NCs. The physicochemical characterization was done by ultraviolet-visible spectroscopy (UV-Vis), transmission electron microscopy (TEM), high- resolution scanning electron microscopy (HR-SEM), Energy Dispersive Spectroscopy (EDS), Fourier transform-infrared spectroscopy (FTIR). The UV-Vis spectroscopy of the prepared AgNPs and Ag-CS-NCs showed variation in the appearance of specific significant peaks, 425 nm for AgNPs and 275, 425 nm for Ag-CS-NCs. The microscopic analysis was done by TEM and the results revealed that both NPs were spherical in shape, with average size ranged from 10 to 60 nm. The HR-SEM micrographs revealed a rough surface with uneven surface topology of the AgNPs, while Ag-CS-NCs were thin, straight and smooth pipe. FTIR spectroscopy indicated that the functional groups (proteins and secondary metabolites) present in the CFF might be responsible for the bioreduction of Ag+ (ions) to produce stabilized protein-capped AgNPs. This study presents the antifungal activity and anti-aflatoxin B1 of AgNPs and Ag-CS-NCs against an aflatoxigenic isolates of A. flavus. Our in vitro results showed notable antifungal activity and potency in thwarting aflatoxin B1 (AB1) production. In addition, SEM imaging was applied to observe the changes in fungal hyphal morphological features after the interactions with AgNPs and Ag-CS-NCs.

Design and antimicrobial profiling of silver-chitosan nanocomposites for biomedical applications

Design and antimicrobial profiling of silver-chitosan nanocomposites for biomedical applications

Hydrothermal Synthesis and Properties of Chitosan–Silver Nanocomposites

Hydrothermal Synthesis and Properties of Chitosan–Silver Nanocomposites

Biosynthesis of silver nanoparticles for the fabrication of non cytotoxic and antibacterial metallic polymer based nanocomposite system

Nanomaterials have significantly contributed in the field of nanomedicine as this subject matter has combined the usefulness of natural macromolecules with organic and inorganic nanomaterials. In this respect, various types of nanocomposites are increasingly being explored in order to discover an effective approach in controlling high morbidity and mortality rate that had triggered by the evolution and emergence of multidrug resistant microorganisms. Current research is focused towards the production of biogenic silver nanoparticles for the fabrication of antimicrobial metallic-polymer-based non-cytotoxic nanocomposite system. An ecofriendly approach was adapted for the production of silver nanoparticles using fungal biomass (Aspergillus fumigatus KIBGE-IB33). The biologically synthesized nanoparticles were further layered with a biodegradable macromolecule (chitosan) to improve and augment the properties of the developed nanocomposite system. Both nanostructures were characterized using different spectrographic analyses including UV–visible and scanning electron microscopy, energy dispersive X-ray analysis, dynamic light scattering, and Fourier transform infrared spectroscopic technique. The biologically mediated approach adapted in this study resulted in the formation of highly dispersed silver nanoparticles that exhibited an average nano size and zeta potential value of 05 nm (77.0%) and − 22.1 mV, respectively with a polydispersity index of 0.4. Correspondingly, fabricated silver–chitosan nanocomposites revealed a size of 941 nm with a zeta potential and polydispersity index of + 63.2 mV and 0.57, respectively. The successful capping of chitosan on silver nanoparticles prevented the agglomeration of nanomaterial and also facilitated the stabilization of the nano system. Both nanoscopic entities exhibited antimicrobial potential against some pathogenic bacterial species but did not displayed any antifungal activity. The lowest minimal inhibitory concentration of nanocomposite system (1.56 µg ml−1) was noticed against Enterococcus faecalis ATCC 29212. Fractional inhibitory concentration index of the developed nanocomposite system confirmed its improved synergistic behavior against various bacterial species with no cytotoxic effect on NIH/3T3 cell lines. Both nanostructures, developed in the present study, could be utilized in the form of nanomedicines or nanocarrier system after some quantifiable trials as both of them are nonhazardous and have substantial antibacterial properties.

Evaluation of Biopolymer Films Containing Silver–Chitosan Nanocomposites

Chitosan (commercial and shrimp)–silver active agent nanocomposites (Ag–CC–NCs and Ag–SC–NCs) for inclusion in biopolymer films were synthetized in this study and characterized (mechanical, optical, transport, and structural properties and the in vitro antifungal activity). The hydrocolloid was integrated into linseed mucilage (LMF) commercial chitosan (CCF) and shrimp chitosan (SCF) films. The films were transparent, smooth, and continuous. The incorporation of Ag–CC–NCs or Ag–SC–NCs did not modify the film strength but did modify film elasticity. Based on the morphological characterization, the nanocomposites had a spherical shape (100 to 250 nm diameter). The LMF + Ag–SC–NCs film showed the highest water solubility (85.7%). The water vapor permeability increased with the addition of Ag–NCs–chitosan reaching the CCF-based films higher permeabilities (5.491–3.953 g/Pa.s.m × 1010), which indicates that they could be used in foods with high moisture content. The differences between treatments are indicative of the various applications that films can have in foods of different natures.

Preparation of Silver-Chitosan Nanocomposites Colloidal and Film as Antibacteri Material

<p>Colloidal nanocomposites silver-chitosan have been made. Silver nanoparticles were produced by chemical reduction methods assisted microwave irradiation using chitosan from crab shells as a reducing agent and stabilizer, AgNO<sub>3 </sub>as a precursor and NaOH as an accelerator. This study investigated AgNO<sub>3</sub> concentration toward localized surface plasmon resonance (LSPR) phenomenon of nanocomposites colloidal. The size and shape of the silver nanoparticles were confirmed by TEM. Furthermore, the stability of the storage was observed for twelve weeks. Colloidal and film nanocomposites silver- chitosan have been made by casting method by drying at room temperature. After that, the film characterization was carried out, including swelling with gravimetry methods and surface morphology using scanning electron microscopy (SEM). Diffusion methods tested colloid antibacterial activity and silver-chitosan nanocomposite film’s against <em>E. Coli</em> and <em>S. Aureus</em>. The results showed that the formation of silver nanoparticles was identified by the LSPR absorption band's appearance at 413-419 nm. The increasing of AgNO<sub>3</sub> concentration increased the intensity of the LSPR absorption band. Silver nanoparticles with sizes of about 3-9 nm are spherical. The silver nanoparticles were stable at 12 weeks of storage. The higher AgNO<sub>3</sub> concentration tends to increase the swelling of the film. The surface of the silver-chitosan nanocomposite film’s was rougher than that of the chitosan film. The higher the silver nanoparticle concentration, the higher the colloid and film antibacterial activity against <em>E. Coli</em> and <em>S. Aureus.</em></p>

Facile and low-cost green synthesis of eco-friendly chitosan-silver nanocomposite as novel and promising corrosion inhibitor for mild steel in chilled water circuits

New promising samples of silver nanoparticles: (SNPs)-chitosan (CT) nanocomposite (NC) abbreviated as (SNPs-CTNC) have been synthesized and characterized using the novel green chemistry approach. All the synthesized formulations showed innovative corrosion inhibition for the mild steel samples in the cooling water system. The experimental conditions for the green synthesis of eco-friendly silver nanoparticles (SNPs) using chitosan (CT) biopolymer as both reducing and protecting coating agent for SNPs have been optimized. The synthesis route presented herein was performed by the reduction of silver nitrate (AgNO3) by CT in an autoclave reactor vessel under 1 bar applied pressure at the reaction temperature of 120 °C and various contact time (2, 4, 8, and 16 h) between (AgNO3) and chitosan (CT). The four prepared samples of SNPs-CT NC have been abbreviated in terms of the reaction or the contact time as (2 h, 4 h, 8 h, and 16 h). The four SNPs-CT NC samples were characterized using: UV–Visible spectroscopy; Fourier transform infrared (FTIR); X-ray diffraction (XRD) and transmission electron microscopy (TEM). The SNPs coated by chitosan biopolymer showed good antimicrobial activity, and have extremely fine particle size approaching that of the quantum dots nanoparticles. The particle size distribution of all the prepared nanocomposite samples lies around the nanometer scale range of 3–6 nm. The corrosion rate of the standard corrosion coupons of mild steel in the industrial chilled water in the absence and the presence of different concentrations of SNPs-CTNC samples were measured by the gravimetric method as well as the electrochemical impedance spectroscopy (EIS) and DC-potentiodynamic polarization techniques. The inhibition efficiency (%IE) of SNPs-CTNC achieved up to 97–98% at the concentration of 150 ppm SNPs-CTNC of all the prepared samples (from chemical gravimetric weight loss results). The inhibition efficiency (%IE) of the best performance SNPs-CTNC sample (8 h) showed inhibition efficiency above 80% at 100 ppm (as evident by the further electrochemical techniques: impedance and potentiodynamic polarization results). Both the inhibition efficiency and the antimicrobial activity of SNPs-CT NC samples remained unchanged on aging for twelve months storage where: The percent inhibition efficiency of all SNPs-CTNC samples remain above the percentage of 93% on aging for this relatively long storage time period, the sample 2 h showed the most constant inhibition efficiency (97.6% for the fresh prepared sample and 97.5% for the twelve months aged sample). In addition, the scanning electron (SEM) micrographs have been showed that: A clean and bright metal surface was maintained after the exposure to the chilled water in the presence of SNPs-CTNC along the immersion time of one year. The nanocomposite samples acted by spontaneous physisorption on the metal surface as indicated by the negative value of ΔG°adsorption (equals −18.002 kJ·mol−1). The adsorption data represented in the surface coverage (θ) were found to be linearly fitted well to Langmuir adsorption isotherm with positive and relatively large value of the binding equilibrium constant (K) (43.6) that represented the strong attraction forces between the adsorbed nanocomposite particles and the metal surface. The mode of the adsorption of these nanocomposite particles on the metal surface has been interpreted in terms of the electrostatic interaction between the negatively charged colloidal SNPs and the positively the charged metal surface.

New Chitosan-Silver Nanocomposites Containing N-Nicontinyl Phosphoric Triamide as an Antibacterial- Enhancer Additive

Three new nanocomposite films of Chitosan/ Ag NPs / N-Nicontinyl phosphoric triamide, containing 3% Ag NPs and 0%, 5% and 10% phosphoric triamide were prepared and characterized by X-ray Powder Diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM) and Energy Dispersive X-ray Spectroscopy (EDS) analysis methods. The nanocomposite films were prepared using ultrasonic waves plus cross-linking the chitosan part of biofilms as the final process and the Ag NPs were synthesized according to the citrate reduction method. XRD graph of the three nanocomposites showed all the characteristic peaks of the phosphoric triamide, Ag NPs, and chitosan, indicating the fact that the preparing process has not made any changes in the phases of the nanocomposites components. All the SEM micrographs and EDS analysis results confirmed the desired structures. In vitro antibacterial activities of the nanocomposite were tested against two Gram-positive bacteria: Staphylococcus aureus (S. aureus), Bacillus cereus (B. cereus) and two Gram-negative bacteria: Escherichia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa) in Brain-Heart Infusion (BHI) medium. Results revealed that the nanocomposite films, containing the phosphoric triamide additive, have better antibacterial effects than the one without this compound. Also, the antibacterial activity of the biofilms depends on the dosage of the phosphoric triamide and increases by raising the percentage of the additive in the structure of the biofilms.

Fabrication of silver-chitosan nanocomposite films and their antibacterial activity

The silver-chitosan nanocomposite film fabrication was carried out by the preparation of silver nanoparticles using chemical reduction methods assisted with microwave irradiation with chitosan as a reducing agent as well as a stabilizer. Silver nitrate is used as a precursor and NaOH as an accelerator. Silver-chitosan nanocomposite colloids were converted into films by casting techniques at the room temperature. Based on UV-Visible spectra, colloidal nanocomposites show absorption peak at the range of 409-412 nm. Based on TEM images, the silver nanoparticles are spherical shaped and distributed with a diameter of 6-10 nm. Based on FTIR spectra, interactions between silver nanoparticles and chitosan occur in the hydroxyl group (-OH) and amine group (-NH) of the chitosan polymer chain. Based on SEM images, the silver-chitosan nanocomposite films show a compact but rough surface morphology. The increase in tensile strength and decrease in elongation at break of the film was in line with the increase in the concentration of silver nitrate, while the value of the elasticity of the film fluctuates depending on the tensile strength and elongation at break. The increasing concentration of silver nitrate also causes an increase in the degree of swelling. silver-chitosan nanocomposite films showed better antibacterial activity against Escherichia coli than Staphylococcus aureus.

Silver/Chitosan Nanocomposites: Preparation and Characterization and Their Fungicidal Activity against Dairy Cattle Toxicosis Penicillium expansum.

This work aimed to evaluate the fungicide activity of chitosan-silver nanocomposites (Ag-Chit-NCs) against Penicillium expansum from feed samples. The physicochemical properties of nanocomposites were characterized by X-ray fluorescence analysis (XRF), small-angle X-ray scattering (SAXS), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The morphological integrity of the nanohybrid was confirmed by electron transmission. By the data of RFA (X-ray fluorescent analysis), the contents of Ag in Ag-chitosan composite were 5.9 w/w%. The size distribution of the Ag nanoparticles incorporated in the chitosan matrix was investigated by SAXS. The main part of the size heterogeneity distribution in the chitosan matrix corresponds to the portion of small particles (3–4 nm). TEM analysis revealed a spherical morphology in the form of non-agglomerated caps, and 72% of the nanoparticles measured up to 4 nm. The minimum inhibitory concentration of NCs was evaluated in petri dishes. Three different concentrations were tested for antifungal activity against the mycotoxigenic P. expansum strain. Changes in the mycelium structure of P. expansum fungi by scanning electron microscopy (SEM) were observed to obtain information about the mode of action of Ag-Chit-NCs. It was shown that NC-Chit-NCs with sizes in the range from 4 to 10 nm have internalized sizes in cells, form agglomerates in the cytoplasm, and bind to cell organelles. Besides, their ability to influence protein and DNA fragmentation was examined in P. expansum. SDS-PAGE explains the apparent cellular protein response to the presence of various Ag-Chit-NCs. The intensity of P. expansum hyphal cell protein lines treated with Ag-Chit-NCs was very thin, indicating that high molecular weight proteins are largely prevented from entering the electrophoretic gel, which reflects cellular protein modification and possible damage caused by the binding of several protein fragments to Ag-Chit-NCs. The current results indicate that Ag-Chit-NCs <10 nm in size have significant antifungal activity against P. expansum, the causative agent of blue mold-contaminated dairy cattle feed.

In Vivo and In Vitro Assessments of the Antibacterial Potential of Chitosan-Silver Nanocomposite Against Methicillin-Resistant Staphylococcus aureus-Induced Infection in Rats.

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most threatening multidrug-resistant bacteria worldwide. Owing to their efficient antimicrobial properties, nanoparticles have been widely used as an alternative approach for combating the antibiotic-resistant bacteria. Consequently, this study was designed to compare in between the bactericidal effect of low doses (5mg/kg bwt) of nanoparticles of chitosan (Ch-NPs), silver (Ag-NPs), and chitosan-silver nanocomposites (Ch-Ag NCs) both in vitro and in vivo against experimentally chronic infection induced by methicillin-resistant Staphylococcus aureus (MRSA). The three forms of nanoparticles were tested for their in vitro antimicrobial potential against MRSA by detection of MICs and MBCs using microdilution method. In vivo, thirty-five male albino Wistar rats were used and divided into five groups (n = 7). Group l (negative control), group 2 (MRSA infected and untreated), groups 3, 4, and 5 (MRSA infected then treated with Ch-NPs, Ag-NPs, and Ch-Ag NCs respectively for 7days). After 6weeks, blood samples were collected then rats were euthanized to collect different organs (liver, spleen, lungs, and kidneys). Some of them were kept in 10% formalin for histopathological investigations while others used for bacterial re-isolation. Ch-Ag NCs showed the lowest MIC and MBC among the tested nanoparticles. Moreover, the highest histopathological scoring was observed in the infected and untreated group while the lowest scoring was detected in groups treated with Ch-Ag NCs in comparison with the negative control group. The highest bacterial count was noticed in the infected and untreated group followed by those treated with Ch-NPs while the lowest count was observed in group treated with Ch-Ag NCs. Depending on these results, it can be concluded that Ch-Ag NCs have a strong bactericidal effect against MRSA and may be used as alternative option to antibiotics.

Silver-chitosan nanocomposite as a plasmonic platform for SERS sensing of polyaromatic sulfur heterocycles in oil fuel

Herein, a silver-chitosan nanocomposite for application in surface enhanced Raman spectroscopy (SERS) sensing was proposed. It was shown that optically transparent chitosan coatings with 0.8 μm thickness allow penetration of target analytes to silver nanoparticles and the analysis in both polar and nonpolar solvents. Under the chosen conditions, chitosan formed continuously smooth films and coatings stabilizing rough nanostructured metallic surfaces and served as a suitable matrix for immobilization, uniform spreading, and preconcentration of the analytes. Polycyclic aromatic sulfur heterocycles were chosen as target analytes being one of the most important fuel quality markers, hazardous components, and the hardest-to-remove impurities. For the most effective immobilization and even distribution of the analytes onto a nanostructured metallic surface, an additional polymer layer of chitosan was found to be needed. The presence of thin films of chitosan resulted in higher reproducibility of SERS spectra as compared to bare nanostructured silver substrates. Additionally, the developed nanocomposite SERS sensors provided the rapid determination of dibenzothiophene and its derivatives in isooctane with the threshold of detection better than 0.1 μM. This approach was successfully applied in the analysis of real fuel samples and the results agreed well with independently measured FTIR and GC-MS data.

Antibacterial, antibiofilm and cytotoxic activities of biogenic polyvinyl alcohol-silver and chitosan-silver nanocomposites

Using biogenically synthesized silver nanoparticles (AgNPs) by Enterobacter cloacae Ism 26 (KP988024); Polyvinyl Alcohol-Silver (PVA-Ag) and Chitosan-Silver (CS-Ag) nanocomposites were prepared by augmentation. Thermal stability, AgNPs distribution and concentration within nanocomposites were characterized using thermogravimetric analysis (TGA), scanning electron microscope/energy dispersive x-ray (SEM/EDX) and atomic absorption spectroscopy (AAS). Nanocomposites films showed higher thermal stability than pure polymers, different AgNPs concentrations with homogenous distribution. Antibacterial, antibiofilm and cytotoxic activities of nanocomposites films were studied against Multi Drug Resistant (MDR) bacteria including Staphylococcus epidermidis (S.e), Staphylococcus aureus (S.a), Escherichia coli (E.c) and Klebsiella pneumoniae (K.p). PVA-Ag nanocomposite showed larger zones of inhibitions and higher antibiofilm activities than CS-Ag nanocomposite against both Gram-positive and Gram-negative bacteria. AgNPs solution, PVA-Ag and CS-Ag nanocomposites showed low cytotoxic activities against Huh-7 liver cells and IC50 values of 263.20 μg ml−1, 1185.07 μg ml−1 and 119.85 μg ml−1, respectively. PVA-Ag and CS-Ag nanocomposites films showed enhanced thermal stability and biological properties that qualify them for different biomedical applications.

Nanomaterial loaded chitosan nanocomposite films for antimicrobial food packaging

Food loss due to spoilage, constitutes is a great economic concern for the food industry. Nanotechnology, being an advanced field comes into play in order to overcome this major global issue of food spoilage. With the help of nanotechnology, unique food packaging techniques can be designed, which can minimise the spoilage and increase the shelf life of food materials. In this study, we prepared and characterised zinc oxide and silver nanomaterials and then prepared chitosan nanocomposite films followed by their characterization. The antimicrobial activity of these films was also evaluated on S. aureus and E. coli by disc assay and cell growth curve analysis. The results showed dose dependent antimicrobial activity of nanocomposites films. It was concluded that the silver-chitosan nanocomposite were more efficient, for use in antimicrobial food packaging applications as compared to the ZnO-chitosan nanocomposite.

Candida albicans Infection Model in Zebrafish (Danio rerio) for Screening Anticandidal Drugs.

Candida albicans is an opportunistic fungal pathogen which causes systemic infections in human. In this study, C. albicans infection model was developed in zebrafish to understand the host-pathogen interactions for straightforward anticandidal drug screening. To develop the infection, 1 × 106cells of C. albicans suspended in phosphate-buffered saline were deposited in zebrafish dorsal muscle by manually operated syringe. The infection progression was externally assessed by a scale of wound-healing events, based on visible changes of yeast deposited in the muscle tissues. Chemotherapy was carried out with known antifungal drugs (fluconazole, nystatin, and amphotericin B) and a potential antifungal agent, chitosan silver nanocomposites (CAgNC), after the infection as direct exposure in the water. Histopathological analysis was performed to identify the pathogen virulence and the host-pathogen interaction during the infection. The light microscopic observations and histopathological analysis revealed the yeast-hyphae transition at the site of infection (at 72hpi) and progression of the infection in the host tissues. The larval survival rate under fluconazole (up to 80μgmL-1) and nystatin (up to 20μgmL-1) was > 90% and for CAgNC it was 40% at 36h post-exposure (hpe). The infection progression was suppressed with the fungicidal treatments. Among inflammatory genes, il-1β has been highly upregulated (14.68-fold) at 24h post infection (hpi). Both il-1β and tnf-α were moderately upregulated in infected fish gills at 72hpi. Among the C. albicans antioxidant genes, cat1 and sod2 have been upregulated during the infection, and relative expression folds were increased from low to moderate levels with the time. We demonstrate the approach for the development of artificial infection model of zebrafish with C. albicans. By this mini vertebrate zebrafish model, researchers will be able to study novel anticandidal compounds in vivo with respect to the host, pathogen, and their interactions.

Safeguarding the catalytic activity and stability of polyaniline chitosan silver nanocomposite bound beta-galactosidase against product inhibitors and structurally related compound

In this study, an attempt has been made to evaluate the effect of products of β-galactosidase (βGS) catalyzed reaction i.e. glucose and galactose and their structurally related compound vitamin C (VC) on the catalytic activity of native and PANI-CS-NC and PANI-CS-Ag-NC adsorbed βGS. Results indicated a decline in catalytic activity of soluble enzyme in the presence of all investigated compounds. The order of inhibition was found to be VC < glucose < galactose. However, the immobilized preparations were found more resistant to inactivation caused by the added compounds. About 48% activity was retained by PANI-CS-Ag-NC-βGS in the presence of galactose (5%, w/v), while the native enzyme exhibited only 18% of its original activity. A significant decrease in absorbance and fluorescence intensity was evaluated in soluble enzyme incubated in the presence of all investigated compounds. Three-dimensional fluorescence graphs, CD and FT-IR spectroscopic studies illustrated noteworthy conformational changes in the secondary structure and microenvironment of the soluble enzyme in the presence of VC and tested sugars. These results suggest that both PANI-CS-NC and PANI-CS-Ag-NC bound βGS are more resistant to the exposure caused by the higher concentration of added glucose, galactose, and VC and, therefore, can be effectively utilized for the production of a hassle-free lactose nano-biosensor.

Green synthesis of silver-chitosan nanocomposite and their application as antibacterial material

It has been studied green synthesis of silver-chitosan nanocomposite using chitosan as a reducing agent as well as a stabilizing agent and NaOH accelerator. This research develops a new strategy for preparation silver-chitosan nanocomposite through gel phase. The silver-chitosan nanocomposite gel is transformed into colloidal by dissolving into chitosan solution. Localized surface plasmon resonance (LSPR) phenomenon of the colloidal silver nanoparticles were investigated using a UV-Vis spectrophotometer. The shape and size of the nanoparticle silver were analyzed using Transmission Electron Microscopy (TEM). Antibacterial activity test of silver-chitosan nanocomposite against E. coli and S. aureus bacteria by disc diffusion method. The formation of silver nanoparticles in the synthesis of silver nanocomposite-chitosan chitosan through the gel phase is characterized by the appearance of LSPRabsorption peak at 402.4 - 414.5 nm. The optimum conditions of silver-chitosan nanocomposite formation were the use of chitosan (1%) of 60 mL, AgNO3 0.07 mmol, NaOH 7 mmol within 18 hours. Based on TEM image of spherical particles with dominated at particle size between 5 - 11 nm. The antibacterial activity of silver-chitosan nanocomposite is high enough that it is potentially used as an antibacterial material for medical applications.

Effect of metal ions present in milk on the structure and functional integrity of native and polyaniline chitosan nanocomposites bound β-galactosidase: A multi-spectroscopic approach

β-Galactosidase is vital to dairy industries because it catalyzes the hydrolysis of lactose into glucose and galactose making it useful for lactose intolerant patients to consume milk and its products. The present study demonstrates the effect of metal ions commonly found in milk, namely Zn2+, K+, Ca2+ and Mn2+ on the activity of native and polyaniline chitosan nanocomposites bound Aspergillus oryzae β-galactosidase. In polyaniline chitosan silver nanocomposite adsorbed β-galactosidase, a multi-fold enhancement in catalytic activity was observed in the presence of cocktail of Zn2+, K+, Ca2+ and Mn2+ ions. 3D fluorescence, CD and FTIR studies established significant conformational changes in the secondary structure of polyaniline chitosan silver nanocomposite bound β-galactosidase on addition of metal ions as compared to the native and other bound enzyme. This enhanced catalytic efficiency of the immobilized enzyme in presence of metal ions can promote its economic use for lactose hydrolysis in milk.

Elucidating the binding efficacy of β‐galactosidase on polyaniline–chitosan nanocomposite and polyaniline–chitosan–silver nanocomposite: activity and molecular docking insights

AbstractBACKGROUNDAspergillus oryzae β‐galactosidase (β‐gal; EC 3.2.1.23) was physically adsorbed on polyaniline–chitosan nanocomposite (PANI‐CS‐NC) and polyaniline–chitosan–silver nanocomposite (PANI‐CS‐Ag‐NC). Stability and kinetic studies were assessed, along with reusability and molecular docking interactions.RESULTSAccording to transmission electron microscopy images, the sizes of the respective NCs were found to be in the range of 23–39 and 6–18 nm. The η (effectiveness factor) values for PANI‐CS‐NC‐ and PANI‐CS‐Ag‐NC‐bound β‐gal were calculated to be 0.89 and 1.23, respectively, suggesting an enhancement in the activity of the enzyme in the presence of silver ions. Significant broadening was observed in pH and temperature profiles. Kinetic properties of PANI‐CS‐NC‐ and PANI‐CS‐Ag‐NC‐bound β‐gal showed lower Km, and two‐ and fourfold higher Vmax, respectively, compared to free enzyme. PANI‐CS‐Ag‐NC‐bound β‐gal was able to retain 94% of its initial activity after 10 repeated uses. Circular dichroism analysis revealed conformational changes in the secondary structure of protein upon immobilization. The genotoxic assessment revealed non‐toxic behaviour of both free and enzyme‐bound NC. The rate of lactose hydrolysis at 50 °C exhibited by PANI‐CS‐‐Ag‐NC bound β‐gal was 7% higher than that for the native enzyme. In‐silico analysis showed efficient binding of β‐gal on PANI‐CS‐ NCs due to interaction with residues that were exclusive of the active site of the enzyme.CONCLUSIONPANI‐CS‐Ag‐NC‐bound β‐gal preparation proved to be a robust nano‐biocatalyst due to remarkable enhancement in catalytic activity along with excellent stability and reusability characteristics, which could be further utilized for efficient construction of nano‐biosensors for producing lactose‐free dairy products to feed lactose‐intolerant patients. © 2018 Society of Chemical Industry