Incorporation of silver nanoparticles into self-assembled bacterial cellulose-starch nanocomposites for antibacterial application

Date

4-2014

Degree

Bachelor of Science in Chemistry

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Evelyn B. Rodriguez

Restrictions

Restricted: Not available to the general public. Access is available only after consultation with author/thesis adviser and only to those bound by the confidentiality agreement.

Abstract

Bacterial cellulose was synthesized using the traditional procedure in making nata de coco. Despite its unique and remarkable properties, it has a number of drawbacks thus addition of other materials in its network was done. Starch was introduced as second phase through the bottom-up process to increase the rehydration ability of bacterial cellulose. Silver nanoparticles on the other hand were incorporated into the bacterial cellulose and bacterial cellulose-starch nanocomposites to introduce antimicrobial activity. Hydrothermal synthesis was used to do this in which bacterial cellulose and bacterial cellulose-starch nanocomposite served as the reducing agent as well as the template. Bacterial cellulose-starch silver nanoparticles nanocomposite was produced with the combined properties of the three materials: bacterial cellulose, starch and silver nanoparticles. Several tests were done to prove this. Energy dispersive X-ray analysis (EDX) was employed to detect the presence of silver in the nanocomposites. Surface plasmon resonance of metal nanoparticles allowed the use of UV-Vis spectrophotometry to detect the silver nanoparticles. The morphology of pure bacterial cellulose and bacterial cellulose-starch were compared using scanning electron microscopy (SEM). The SEM micrograph showed that starch covered the network of bacterial cellulose forming a quasi-homogeneous material. To determine the diameter of bacterial cellulose and bacterial cellulose-starch strands as well as the diameter of the silver nanoparticles, atomic force microscopy (AFM) was used. The AFM micrographs illustrated that the bacterial cellulose strand was 68.6 ± 8.76 nm and bacterial cellulose-starch strand was 87.50 ± 3.87 nm. And the silver nanoparticles in the bacterial cellulose silver nanoparticles nanocomposites (BC-AgNp) was 12.60 ± 3.90 nm and in the bacterial cellulose-starch silver nanoparticles (BC-S-AgNp) was 32.01 ± 2.48 nm. Quantification of the silver nanoparticles in both the BC-AgNp and BC-S-AgNp was done by disintegrating the matrix and converting silver to silver-gelatin complex. BCAgNp contained 2.537 ± 0.925 mg Ag/g nanocomposite and that BC-S-AgNp contained 1.841 ± 0.415 mg Ag/g nanocomposite. To determine if bacterial cellulose and bacterial cellulose-starch nanocomposites were effective templates for silver nanoparticles, the lowest peak in the transmittance spectrum corresponding to its maximum absorbance wavelength was obtained for 90 days. It was found that the maximum absorbance wavelength, 442 nm, did not change for the first 50 days after which it became 445 nm. From the surface plasmon resonance principle, this result indicated that the silver nanoparticles did not aggregate thus making the two matrices effective templates. Evaluation of the swelling ratio and rehydration ability of bacterial cellulose and bacterial cellulose-starch nanocomposites showed that the addition of starch did not significantly increase both parameters. Both BC-AgNp and BC-S-AgNp were tested as antibacterial wound dressing by evaluating the release of silver, antibacterial and angiogenic activities. The release of silver was done in saline phosphate buffer to mimic human epidermal condition. It was found that the release of silver from both nanocomposites continuously increased for a period of 7 days signifying that the availability of a continuous supply of the nanoparticle to the wound making both good antibacterial wound dressings. The antibacterial activity was evaluated using disk diffusion method and two-compartment method against two bacteria usually present in wound: gram negative Pseudomonas aeruginosaATCC 27853 and gram positive Staphylococcus aureus ATCC 25923. No inhibition zone was observed for both nanocomposites but it was observed that there was no bacterial growth on the surface in contact with the nanocomposites. From the two compartment method the percent reduction for BC-AgNp against Pseudomonas aeruginosa and Staphylococcus aureuswas 76.05 ± 9.33% and 96.85 ± 1.13%, respectively. For BC-S-AgNp it was 88.62 ± 10.70% for Pseudomonas aeruginosa and 96.19 ± 1.29% for Staphylococcus aureus. Evaluation of the angiogenic property of the nanocomposites using duck embryo CAM assay showed that both BC-AgNp and BC-S-AgNp increased the number of blood vessels but decreased the mean length and the size of the blood vessels. These results indicated the pro-angiogenic activity and thus could be used as an effective wound dressing since wound healing process can be hastened by angiogenesis.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

LG 993.5 2014 C42 /A68

Document Type

Thesis

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