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EVALUATION OF SWELLING AND MECHANICAL PROPERTIES OF
NANOSTRUCTURED CHITOSAN/GOLD FILMS J.H. Rodriguez1*, G. Ayala1, L.C.O Vercik1, A. Vercik1.
1Basic Sciences Department ZAB/FZEA, University of São Paulo, Av.
Duque de Caxias Norte 225, 13635-900 Pirassununga, SP, Brazil.
*E-mail: [email protected]
Mechanical properties of organic materials have attracted attention for
optimizing engineered biocompatible and biodegradable materials, with
promising potential applications in biomedicine and food engineering.
Polymers obtained from natural sources have unique features such as
high biodegradability, non-toxicity, and different mechanical properties,
depending on the composition and structure. The properties of the
polymer matrix can be improved by including various elements. For
example, gold nanoparticles have already been used to improve
electrical conductivity and as signal boosters in the development of
biosensors [1,2], but they can also affect mechanical properties, limiting
the lifetime of the devices. In recent years, the production of low-cost
metal nanoparticles with biological resources have had a promising
approach for use; the green synthesis is used for the production of gold
nanoparticles, using nontoxic chemicals and renewable materials
through environmentally friendly wastes [3]. This work aims to show first
results of a study on the effects of the incorporation of AuNPs into
chitosan films for use in biosensors.
The presence of AuNPs modifies the type of interaction and intermolecular strength
of a chitosan matrix having a direct correlation with the alteration of the physical and
chemical properties of nanostructured films of chitosan. In this first study we showed
that AuNPs affect the polymer viscosity whereas the Young’s modulus is not altered.
[1] Yinyong Li, Xiaolei Guo, Pengfei Lin, Congcheng Fan, Yihu Song. Preparation
and Functional properties of blend films of gliadins and chitosan. Carbohydrate
Polymers. 81, 2010, 484-490
[2] Wei, D., & Quian, W., Facile synthesis of Ag and Au nanoparticles utilizing
chitosan as a mediator agent. Colloids and surface B: Biointerfaces 62, 2008, 136-
142
[3] G.S. Ghodake, N.G. Deshpande, Y.P. Lee, E.S. Jin. Pear fruit extract-assisted
room-temperature biosynthesis of gold nanoplates. Colloids and surfaces B:
Biointerfaces 75, 2010, 584-589
Addition of AuNPs lead to appreciable morphological differences between chitosan (Fig. 2A) and chitosan/AuNPs films (Fig. 2B). Nanostructured films
present a granular structure, which is not observed in chitosan films. These results are consistent with those reported by EDS, Figure 2C shows the
absence of gold particles whereas Figure 2D shows the presence of AuNPs. On the other hand, the presence of nanoparticles in the polymer matrix
directly affects the types of bonds present in chitosan allowing greater absorption of moisture, which is directly related to the concentration of AuNPs and
the hydrogen potential present in the medium. In an acidic medium, the higher moisture absorption was observed for the matrix with a highest
concentration of nanoparticles (13 mM) Fig . 3A, whereas in basic medium the matrix with a lower concentration of nanoparticles (8 mM) exhibited
higher absorption of moisture (Fig 3B) . Figure 4A shows how the concentration AuNPs affect the mechanical properties of the film exhibiting an increase
of Young’s modulus for films with AuNPs independently of the concentration (approximately the same value for the samples with varying AuNPs). Figure
4B shows the creep test results for the samples with AuNPs; in this case, the characteristic time depends on the AuNPs concentration.
AuNPs 90ºC for 3h
HAuCl4 (8 mM & 13 mM)
4 mL
Chitosan solution (6.92 mg/ml)
10 mL
Chitosan solution (20 mg/ml)
13.5 mL
AuNPs (8 mM & 13 mM)
13. mL
Films drying
24h • SEM and EDS was used for analysis of
surface morphology of the organic films
containing the AuNP and to confirm the
presence of elemental gold.
• The swelling of the nanostructured matrix
was performed with buffer solution at pH
acid (5) and basic (9). The water absorption
capacity (swelling) of the samples was
calculated by weighing the samples at fixed
times and passed over filter paper to
remove excess surface water.
Figure 1. Tensile and Creep test
• The mechanical characterization of chitosan films was performed in a texturometer
Stable Micro System (Figure 1). Tensile and Creep tests were carried out in samples of
pure chitosan and chitosan with AuNPs.
Figure 2. Morphological comparison via SEM of polymeric films without AuNPs (A) and with
AuNPs (B). EDS of both type of samples are shown in (C) and (D). The characteristic peaks
of Au are shown. A Ca peak in the pure chitosan sample is associated to residuals of the decarbonation process.
Figure 3. Water uptake related weight gain
with respect to time for chitosan with different
concentrations of AuNPs in acidic pH (A) and basic pH (B)
Figure 4. Effects of the AuNP on the
mechanical properties: A) Stress-strain
curve; B) Creep tests for films with AuNP
(8mM and 13mM). The Young’s Modulus
and characteristic times are shown in the figure.
FAPESP, CAPES, IQ-Unesp (Araraquara)
A
B
C
D
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