Mater. Res. Soc. Symp. Proc. Vol. 1453 © 2012 Materials Research SocietyDOI: 10.1557/opl.2012.1341

Study on Synthesis Chitosan Oligomer Stabilized Silver Nanoparticles Using Green

Chemistry and Their Burn Wound Healing Effects

Yun Ok Kang1 and Won Ho Park

2

1Department of Nano Technology, Chungnam National University, Daejeon, Korea

2Department of Advanced Organic Materials and Textile System Engineering, Chungnam

National University, Daejeon, Korea

ABSTRACT

The preparation of metal nanoparticles is a major research area in technical engineering

due to their unusual properties, such as catalytic activity, novel electronic, optic and magnetic

properties and biotechnology. Specially, silver has been used for years in the medical field for

antimicrobial applications because it known for its antimicrobial properties and even has shown

to prevent HIV binding to host cells. Common synthesis, chemical and physical methods using

chemical reducing agent and organic solvent are not too suitable to have application to

bioengineering because they should have associated environmental toxicity or biological hazards.

Development of sustainable processes through green chemistry is attractive about the elimination

or minimization of chemical waste. Here, we introduce the green method for preparation of silver

nanoparticles using chitosan oligomer as both reducing and stabilizing agent in water. We expect

that the use of environmentally benign solvent and chitosan oligomer to prepare silver

nanoparticles offers numerous benefits and compatibility for pharmaceutical and biomedical

applications.

INTRODUCTION

The application of nanoscale materials, usually ranging from 1 to 100 nanomerters (nm),

is an emerging area of nanotechnology. Nanomaterials may provide solution to technological and

environmental challenges in the areas of solar energy conversion, catalysis, medicine and water

treatment. Generally, metal nanoparticles can be prepared and stabilized by physical and

chemical methods such as chemical reduction, electrochemical techniques and photochemical

reduction is most widely used. Most research reported these chemical and physical methods

using chemical reducing agents and organic solvent are not too suitable to have application to

biotechnology since they should have associated environmental toxicity or biological hazards.

Over the past decade there has been an increased emphasis on the topic of “green”

chemistry and chemical processes. These efforts aim at the total elimination or at least the

minimization of generated waste, green synthesis is progressively integrating with modern

developments in science and industry. Utilization of nontoxic chemicals, environmentally benign

solvents and renewable materials are some of the key issues that merit important consideration in

a green synthesis. In earlier reports natural polymers like starch and chitosan are reported to

stabilize silver nanoparticles, separate reducing agents were used.

The antimicrobial properties of silver have been known from antiquity: the Egyptians,

Greeks, Romans, and other ancient civilizations used silver vessels to store perishable foods, and

silver cutlery, cups, and dishes were used by the rich. While the discovery of penicillin led to the

era of synthetic antibiotics, increasing antibiotic resistance of bacteria and the ineffectiveness of

synthetic antibiotics against some bacterial strains have led to the reemergence of interest in

silver, silver salts, silver compounds and nanocrystalline silver as antibacterial agents. And also,

it is known that chitosan including chitosan oligomer, the N-deacetylated derivative of chitin, has

significant antibacterial activity against a broad spectrum of bacteria.

In the present work, we not only investigated preparation of silver nanoparticles using

chitosan oligomer acting as both the reducing and stabilizing agent, but also proposed the

possible synergistic combination of chitosan oligomer with silver nanoparticles for improved

antimicrobial efficacy in vitro and against burn infections in a mouse model.

EXPERIMENT

Silver nanoparticles were prepared by the reduction of silver nitrate(AgNO3, Kogima

Chemical Co., LTD.) with chitosan oligomer(Mw<1,000) in water. A series of experiments were

performed varying the order of reactants to obtain perfectly transparent silver particles. In a

typical preparation, 0.5 ml of 0.1 M AgNO3 solution was added to 60 ml of 5%(w/v) chitosan

oligomer solution. After complete dissolution, the mixture was carried out in three-necked glass-

stopper flasks fitted with a double-walled spiral condenser to arrest evaporation and heated to 70 oC, All solution components were purged with nitrogen before use to eliminate oxygen.

The rate of formation of silver nanoparticles (dark yellow color) was followed

spectrophotometrically by monitoring the absorbance at 400 nm (max of silver particle) using a

sampling technique at known time intervals with UV-vis spectrophotometer. The first-order rate

constants (kobs, s-1

) were calculated from the initial part of the slopes of the plots of ln(a/(1-a))

versus reaction time with a fixed time method, where a=At/A and At and A are the absorbance

at times t and , respectively. The zero time was taken when AgNO3 solution added to chitosan

oligomer solution.

To study on in-vitro burn wound healing in mouse, Ag nanoparticles synthesized using

chitosan oligomer in aqueous solution were mixed with white vaseline, stearyl alcohol and

surfactant (HCO-40) at 70 oC to give an emulsion. The emulsion was slowly cooled down to

room temperature to give a CHI-Ag ointment.

DISCUSSION

The use of chitosan oligomer solution for the production of silver nanoparticles is very

simple and faster. After adding AgNO3 solution, the mixture solution turned dark yellow,

indicating the formation of Ag nanoparticles. The typical peak around 380 ~ 400 nm corresponds

to the characteristic surface plasmon resonance of silver nanoparticles. The maximum

absorbance and wavelength curves for the formation of Ag nanoparticles at different reaction

temperature are shown in Figure 1. It shows the existence of two well-defined processes

associated with the nucleation and growth of the particles. Nucleaton implies an increase in the

number of scattering centers (number of particles) for a given system, and therefore, it gives an

increase in the scattered intensity. On the contrary, the growth of particles is associated with a

decrease of the scattered intensity since the observation window corresponds to the diffraction of

smaller particles that are disappearing during the growth process. The reaction rate increased

with an increase in reaction temperature (kobs = 0.93, 1.01, 1.11, 1.43, and 1.88 × 102, s

-1). And

also, the surface plasmon resonance (SPR) bands were gradually red-shifted as a function of

reaction time and temperature. The shift of the maximum wavelength related to increasing the

average diameter of Ag nanoparticles.

Figure 1. Maximum absorbance(a) and wavelength(b) curves for the formation of Ag

nanoparticles at different reaction temperature 50 oC(■), 60

oC(○), 70

oC(▲), 80

oC(▽) or 90

oC (◆).

The size and morphology of synthesized Ag nanoparticles have been imaged using TEM

(Fig. 2).

Figure 2. TEM images and the corresponding particle size distribution (insert) of a series of

silver nanoparticles synthesized with different reaction temperature.

The corresponding histogram of the particles size distribution for the respective samples is

presented along with the TEM images. All nanoparticles appear to be almost spherical. The

variation of the average particles sizes have been observed with an increase in reaction

temperature.

CONCLUSIONS

We have presented a new method for the preparation of Ag nanoparticles with spherical

formation stabilized and reduced by chitosan oligomer at mild condition. The diameter of Ag

nanoparticles by TEM image was found to be between 20 and 70 nm. The resulting nanoparticles

solution displays the characteristic plasmon absorption band around 380 ~ 400 nm. The

reduction rate increased with an increase in reaction temperature. We expect that the use of

environmentally benign solvent and chitosan oligomer to prepare silver nanoparticles offers

numerous benefits and compatibility for pharmaceutical and biomedical applications. Now, we

have been studied for in-vitro burn wound healing in mouse using CHI-Ag ointment.

REFERENCES

1. Z. Khan, S. A. Al-Thabaiti, A. Y. Obaid, and A. O. Al-Youbi, Colloids and surface B:

Biointerfaces 82, 513 (2011).

2. P. Raveendran, J. Fu, and S. L. Wallen, Journal of American Chemical Society, 125,

13940 (2003).

3. V. K. Sharma, R. A. Yngard, and Y Lin, Advances in Colloid and Interface Science, 145,

83 (2009).

4. S. K. Mehta, S. Chaudhary, M. Gradzielski, Journal of Colloid and Interface Science 343,

447 (2010).

5. R. Patakfalvi, S. Papp, and I. Dekany, Journal of Nanoparticle Research 9, 353 (2007).

6. H. V. Tran, L. D. Tran, C. T. Ba, H. D. Vu, T. N. Nguyen, D. G. Pham, and P. S. Nguyen,

Colloids and surfaces A: Physicochemical and Engineering Aspects, 360, 32 (2010).

7. E. I. Rabea, M. E. Badawy, C. V. Stevens, G. Smagghe, W. Steurbaut,

Biomacromolecules 4, 1457 (2003).

8. T. Dai, M. Tanaka, Y-Y. Huang, M. R. Hamblin, Expert Reviews of Anti-infective

Therapy 9, 857 (2011).