The increased intensity (IS3 > IS2 > IS1) of the major silver peak (111) reflected the improvement in crystallinity of the deposited material which might be due to the enhanced density of decorated crystalline AgNPs on the Co-cores [39,40]. Upon addition of reducing and stabilizing agents, the colour of the solution turned from pink to milky pink which then turned to purple/dark purple and then finally black with the heat treatment (figure 2b–e). By changing the density of decorated AgNPs, the available surface area and thus the amount of the loaded drug can be controlled.

The antibacterial properties of Co-cores (S0), as well as all AgNP-decorated composite structures (S1, S2 and S3) were tested for E. coli and B. subtilis by Kirby Bauer disc diffusion method [34]. Thus, SEM micrographs clearly showed the decoration of AgNPs on Co-cores and their enhanced concentration with increasing the amount of silver precursor in the solution.

These characteristic peaks could be attributed to reflection planes (111), (200), (220) and (311) of FCC structure of pure metallic silver according to JCPDS file no. The structural properties of all samples were studied by XRD and the results are shown in figure 3. Incubation was done in a humidified controlled atmosphere at 37°C under 5% CO2.

The increased antibacterial activity of nanocomposites with a higher density of AgNPs (sample S3) revealed that perhaps higher concentration of AgNPs released more silver ions (Ag+) which subsequently enhanced bactericidal performance against E. coli and B. subtilis. The authors acknowledge Dr Muhammad Javaid Iqbal, Dr Shahid Atiq and Dr Syed Sajjad Hussain from Centre of Excellence in Solid State Physics, University of the Punjab, Lahore, Pakistan for their cooperation in experimental work and useful discussions in manuscript writing.

(f) Demonstration of different colours of final colloidal samples; (S0) no silver content, (S1) 0.01 g silver content, (S2) 0.1 g Silver content and (S3) 0.2 g silver content.Download figureOpen in new tabDownload powerPoint. Potential bactericidal mechanisms of [email protected] against bacterial cells. A graphical demonstration of the measured results is shown in figure 8c,d.

The XRD pattern of sample S1 is shown by the green line in figure 3. On dissolving the cobalt acetate in EG, the solution acquired a pink colour (figure 2a). x��=k��Hr� �?�SB-�����p~��N|�ds�gPT�ijDjIJ�?ʿLUuS�H�h�j9@�!�MVu������M��Y�z�������x_�o��/׷�����M�2k����������&�������y��|!�K��{��R��K$�ī�����W�|�������Bl����A��c��KZ��ϟco��g�)�%���/_|��/��?�|�|��/_:��~��λ�۪m�����������Y$��A������Og�xv�ÖA=��m����#�_���%~ ��] ?��(�k���Gʟؚ�b�Z����sFK�PG9S24�- "���+�$H��,ܓ2P0X0���y��y�� R�@%�l����{�հ=�*>�Y)E��c�?�0�� ��L��� It can be observed that the bactericidal performance of synthesized samples against both bacterial strains increased from minimum to maximum as the silver content was enhanced from no silver (S0) to the maximum (S3).

In figure 3, the indexed diffraction spectra of sample S2 and S3 are represented by blue and red lines, respectively. The peaks of the XRD pattern for nano Ni corresponded to the fcc Ni structure (Fig.

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This SEM image suggests that silver content was deposited on the Co-cores in the form of shells as nano-sized structures (30–50 nm).

The solution was heated up to 120°C and kept for 15 min under continuous stirring. In the next step atoms are bond together to form silver nanoparticles[18]. The synthesized hybrid nanocomposites with magnetic ability and tenable antibacterial performance can be considered as effective drug carriers.

The graphical representation of all measured ZOI against (c) E. coli and (d) B. subtilis. ), mixed by stirring (100 r.p.m.)

The increased amount of Ag-content further enhanced the concentration of AgNPs on Co-cores, thus intensifying the pinning effect [25,31]. Typically, a predetermined amount of silver acetate was mixed mechanically (stirring at 100 r.p.m.) The morphological study was performed by SEM and obtained micrographs are presented in figure 4.

and S.N. Published by the Royal Society under the terms of the Creative Commons Attribution License

conducted the characterization measurements and helped in the interpretation of data. )���o]� The manageable surface to volume ratio of these nanocomposites due to the presence of AgNPs makes them more beneficial than core–shell structures. 2017 What is antimicrobial resistance? FOROUGH, FARHADI X-ray diffraction analysis The dry powders of the silver nanoparticles were used for XRD analysis. (a–e) Manifestation of colour changes that occurred during the synthesis of Co-cores indicating different stages of the reaction; (a) precursor solution, (b) after the addition of reducing and stabilizing agents, (c–e) upon heating the solution up to 195°C. Because of the availability of promising sites on the Co-particles, a heterogeneous nucleation mechanism might occur making a way to the formation of AgNPs on the Co-cores [25,26,35].

4 ). VSM magnetic hysteresis curves showing the magnetic properties of Co-cores before and after AgNP deposition.Download figureOpen in new tabDownload powerPoint. Feng et al.

A thick film of each sample was achieved on a clean glass substrate by drying the colloidal sample for XRD measurements.

The antibacterial results indicate that each sample exhibited biocidal performance against both strains. A.T. conducted the cell cytotoxicity experiments and helped in data analysis. Figure 1. Figure 2. Asterisks indicate significant differences between 0 µg ml−1 and higher concentrations (5–20 µg ml−1) of each group (S0, S1, S2 and S3; *p < 0.05; **p < 0.01; ***p < 0.001).Download figureOpen in new tabDownload powerPoint. 4 0 obj Sterile paper discs soaked in all prepared colloidal samples were positioned on the E. coli and B. subtilis coated nutrient agar plates. Magnetic cores loaded with metallic nanoparticles can be promising nano-carriers for successful drug delivery at infectious sites.

This band broadening may be ascribed to the size distribution of both core and decorating NPs, synergetic phase retardation effects and electron scattering at the sharing interfaces [31,45].

Similar variations in magnetic properties (decrease in Ms and increase in Hc) of magnetic cores by capping or decorating with various non-magnetic materials have also been reported in other studies [25,49,52–54]. Schematics of the nanocomposite preparation routes. The silver nanoparticles obtained were characterized using Fourier-transform infrared spectroscopy (FT-IR), X-Ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) to determine their morphology and size.

The diffracted intensities were recorded from 20 to 80 at 2 theta angles.The diffraction pattern in Figure 3 corresponds to pure silver metal powder.

t�v�ѤB�.y��5P�)mc�c~��>��0��i��!%ʕoE��#7~�x6�b��0{7�j�kt]�Fы7b¯����b��5�u��K6��~Y-3p��\C{��yS�3��AHt�yx��L8s'��j�r�� ���(}�rzQ�����,�"���@�vVM���xE�xoʶ6�j��v����O!����/�+���b1��c�8s��4��8���P�l�q�O5�vV�ٮWk ���$��sq�-�eK�^��:dK|c �s�Q����3@K�B���sNpa��;8�M���1>M��BS����Sb��DdU{ 7?�۬lྚ�E-Շ Reduction of Ag+ ions into metallic AgNPs on magnetic cores by virtue of anchoring sites was also reported by other researchers [7,20]. This may work under the effect of electrostatic interactions, hydrophobic effects and van der Waals forces.

(a–e) Manifestation of colour changes that occurred during the synthesis of Co-cores indicating different stages of the reaction; (a) precursor solution, (b) after the addition of reducing and stabilizing agents, (c–e) upon heating the solution up to 195°C.

A close observation (figure 4b) revealed the bridge formation between the cobalt particles which could be the result of gold coatings on the sample.

Table 4.

However, the absorbance bands of sample S2 and S3 (denoted by blue and red lines, respectively) in figure 5 exhibited a different trend to sample S0. VSM magnetic hysteresis curves showing the magnetic properties of Co-cores before and after AgNP deposition. Again drop casting approach was employed to achieve enough material of each sample on glass substrates for SEM analysis. <>

Perhaps at lower concentrations, the amount of released Co ions was not high enough to significantly affect the cell viability.

All experiments were performed in triplicate. Cytotoxicity responses of prepared particles against MCF7 cell line showing concentration-dependent cell viability. Perhaps due to overlapping of both peaks, the cobalt peak could not be distinguished.

Indexed XRD pattern of Co-cores (S0) without any silver content is represented by a black line in figure 3. By increasing the amount of silver to 0.1 g (sample S2), these tiny structures appeared as proper spherical AgNPs having diameters from 30 to 80 nm on Co-cores and their concentration also appeared to increase as is evident in figure 4d.



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