Tese_TÃ¢nia Vieira.pdf - Ubi Thesis

More documents

Recommendations

Info

Chapter III – Results and Discussion was more intense with the increasing of the AgNO 3 concentration and if the reducing agent is, again, NaBH 4 . Another difference between the chitosan/dextran nanoparticles alone and these with silver in general (both AgNO 3 and AgNPs) was the change in the relative intensities of the infrared bands located around 1530 cm -1 . Such band appeared due to the specific interaction between chitosan and dextran. Therefore, considering a change in the intensity of such band, it can be depicted that silver (in general) interacts with the complex chitosan/dextran. The peak at 3300–3430 cm −1 for the chitosan/dextran nanoparticles spectrum has showed a relative decrease of transmittance when AgNO 3 and AgNPs were attached to them, indicating that the N-H vibration of chitosan (characteristic of this spectrum) was affected due to the attachment of the NH 2 groups of chitosan with the Ag + during the electrochemical process (Reicha et al. 2012). Also, a relative reduction in the intensity of the peak at 1630 cm −1 has been noted due to the deformation vibration of the amine groups of chitosan (Ali et al. 2011; Reicha et al. 2012). Figure 11 – FT-IR spectra of chitosan/dextran nanoparticles with AgNPs produced with NaBH 4 (green), chitosan/dextran nanoparticles with AgNPs produced with C 6 H 8 O 6 (brown), chitosan/dextran nanoparticles with AgNO 3 and NaBH 4 (red), and chitosan/dextran nanoparticles with AgNO 3 and C 6 H 8 O 6 (yellow). 38
Chapter III – Results and Discussion 3.4. Evaluation of the antibacterial activity of the produced nanoparticles The antibacterial properties of the produced nanoparticles were evaluated against one bacterial strain a Gram-negative E. coli. The bacterial strain was deemed appropriate for testing the antibacterial properties of the nanoparticles since it has been reported to be the most common Gram-negative pathogen found in biomaterial-associated infections (Juan et al. 2010). The antibacterial effects of the produced nanoparticles were evaluated using the MIC and MBC, which are the standard microbiological procedures used to evaluate the bacteriostatic and bactericidal properties of antimicrobial agents. As already referred in the previous chapter, to determine MIC values, the nanoparticles were diluted 8 times with 100 µL of LB Broth inoculated with the tested bacteria at a concentration of 2.5×10 5 CFU/mL. The MIC was analyzed after 24 h of incubation, at 37 °C, based on culture turbidity. In cases where the nanoparticles affected the turbidity, rezazurin was used to determine the MIC value. The MIC was determined as the lowest concentration that inhibited the visible growth of the bacteria (Guzmán et al. 2009). Control bactericidal tests of chitosan and AgNO 3 solutions were also performed. To verify the reproducibility of the results, all antibacterial activity tests were performed in triplicate in three different days. The MBC was also determined by an imprinted method in an agar plate and it was also analyzed after 24 h of incubation, at 37 °C, based on the absence of colonies on the agar plate. The results of the tests of MIC and MBC of the nanoparticles against Gram-negative bacteria are listed in table 3 and 4, respectively. Figure 12 shows a representative experiment for the determination of the MIC and MBC. Table 3 – MIC obtained for the different tested nanoparticles. Materials tested MIC (µg/mL) Chitosan/Dextran nanoparticles 107.100 Chitosan solution 62.500 Chitosan/Dextran nanoparticles + AgNPs (NaBH 4 ) 1.500 Chitosan/Dextran nanoparticles + AgNPs (C 6 H 8 O 6 ) 3.000 Chitosan/Dextran nanoparticles + AgNO 3 + C 6 H 8 O 6 11.750 Chitosan/Dextran nanoparticles + AgNO 3 + NaBH 4 23.500 AgNPs (NaBH 4 ) 10.000 AgNPs (C 6 H 8 O 6 ) >10.000 AgNO 3 15.625 39
Page 1 and 2:
UNIVERSIDADE DA BEIRA INTERIOR Ciê
Page 3 and 4:
iii
Page 5:
Acknowledgments First of all, I wou
Page 8 and 9: viii
Page 11 and 12: Table of Contents 1. Introduction .
Page 13 and 14: xiii
Page 16 and 17: List of Tables Chapter I - Introduc
Page 18 and 19: List of Acronyms Ag 0 Metallic silv
Page 21 and 22: Chapter I Introduction
Page 23 and 24: Chapter I - Introduction al. 2011).
Page 25 and 26: Chapter I - Introduction Due to the
Page 27 and 28: Chapter I - Introduction materials
Page 29 and 30: Chapter I - Introduction Besides it
Page 31 and 32: Chapter I - Introduction Table 1 -
Page 33 and 34: Chapter I - Introduction ROS produc
Page 35 and 36: Chapter I - Introduction central is
Page 37 and 38: Chapter I - Introduction Furthermor
Page 39 and 40: Chapter I - Introduction 1.4. Objec
Page 41 and 42: Chapter II - Materials and Methods
Page 47 and 48: Chapter III - Results and Discussio
Page 57: Chapter III - Results and Discussio
Page 69 and 70: Chapter IV Conclusions and future p
Page 71 and 72: Chapter IV - Conclusions and Future
Page 73 and 74: Bibliography 5. Bibliography Albers
Page 75 and 76: Bibliography Fernebro, J. (2011). "
Page 77 and 78: Bibliography Li, W.R., Xie X.B., Sh
Page 79 and 80: Bibliography Pal, S., Tak Y.K. and
Page 81 and 82: Bibliography Speranza, G., Gottardi
show all

Tese_TÃ¢nia Vieira.pdf - Ubi Thesis

Create successful ePaper yourself

Delete template?

Save as template?