Broad-spectrum anti-microbial activity of bacterial cellulose silver nanocomposites with sustained release
ShivakalyaniAdepua
a First author, Department of Materials Science and Metallurgical Engineering
Indian Institute of Technology, Hyderabad
NH9, Kandi Village, Sangareddy district
Telangana India 502285
E-mail:
Phone: +91 9701711753
MudrikaKhandelwalb
bCorresponding author, Assistant Professor,
Department of Materials Science and Metallurgical Engineering
Indian Institute of Technology, Hyderabad
NH9, Kandi Village, Sangareddy district
Telangana India 502285
Email:
Phone: 040 23017118
Supplementary material
Thermogravimetric analysis (TGA)
Amount of silver incorporated in BC was determined from the relative mass loss obtained in Thermogravimetric analysis. Fig.S1 shows TGA curves obtained for BC and AgBCcomposites. The thermal degradation of BC occurs in two steps located at approximately 270°C and 400°C. No mass loss observed before 100˚C, this indicates that the samples were devoid of moisture. There is only 20% mass loss upto 270˚C. After that, there is a gradual mass loss of 80% up to 400˚C. From 400˚C to 600˚C, there is a slow mass loss. For pure BC samples, 100% mass loss has been observed at 600˚C. The residual mass about 1% obtained for composites at 600°C is related to silver. The amount of AgNO3 used is same in all the three composites regardless of reducing agent concentration. Therefore, the amount of silver incorporated is same in all the three composites.
Optical images of Ag colloid and AgBC composites
The three dimensional nanofibrous porous network of bacterial cellulose allows easy penetration of AgNO3 and NaBH4 solutions, thereby enhancing the in situ production of silver nanoparticles. As the molar ratio of NaBH4 to AgNO3 goes on increasing from 3:1, 15:1, 30:1, color of the AgBC composite also changed from light brown, dark yellow to light yellow (Fig.S2).
UV-Visible spectra of Ag colloid
UV-VIS absorption spectra of Ag1, Ag5, Ag10 was depicted in fig. S3 With the increase in molar ratio of NaBH4:AgNO3, the absorption maxima was found to shift towards higher wavelength. Ag1, Ag5, Ag10 have shown absorption maxima at 388, 390 and 393 nm respectively.
Supplementary Table.1 Crystallite size of Ag colloid and AgBC composites samples from XRD
2 / h k l / Crystallite Size (in nm)Ag1 / AgBC1 / Ag5 / AgBC5 / Ag10 / AgBC10
38.1 / 111 / 17.06 / 4.75 / 11.5 / 3.75 / 7.5 / 2.45
44.3 / 220 / 17.84 / 4.89 / 11.06 / 3.81 / 7.6 / 2.51
64.3 / 200 / 17.96 / 4.95 / 11.14 / 3.91 / 7.45 / 2.62
77.4 / 311 / 18.25 / 5.20 / 11.85 / 4.25 / 7.23 / 2.89
81.4 / 222 / 18.55 / 5.11 / 11.88 / 4.30 / 7.01 / 2.91
SEM and EDS of AgBC composites
Ag
Preparation of microbial inoculum
Freshly harvested tomatoes were bought from market and were packed in polythene bag and kept at room temperature for 7, 15 and 30days. At 7th, 15th and 30th day (Fig. S5), the rotten tomato was ground using a blender and the juice (Fig. S6) was used as culture for testing. 1gm of juice was transferred to nutrient broth and incubated for 72h for the microbes to multiply. Then, dilutions were prepared from this in fresh broth to adjust the CFU count. Cell density of rotten tomato culture was adjusted with 0.9% normal saline to 1.5 x 108 CFU/mL by measuring optical density with respect to Mcfarland standard 0.5 OD. Microbial load was highest with tomatoes rotten for 30 days amongst 15 and 7 days rotten tomatoes. Anti-microbial activity was tested for all the three. As the composite and colloid has shown activity with 7, 15, 30 days rotten tomatoes, results were reported for activity shown for 30days.
Fig. S5 Optical images of tomatoes stored in polythene bag for 1, 7, 15, 30 days
Fig. S6 Juice extracted from rotten tomatoes at 7th, 15th and 30th days
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