Rapid biosynthesis of irregular shaped gold nanoparticles from macerated aqueous extracellular dried clove buds (Syzygium aromaticum) solution

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Abstract

In this paper, we stress upon rapid synthesis of irregular shape gold nanoparticles from a biological base. Treatment of macerated extracellular aqueous dried clove buds (Syzygium aromaticum) solution with the aqueous gold salt solution yielded irregular shaped stable gold nanoparticles in the range of 5–100 nm. The synthesis and morphology of these gold nanoparticles are understood by UV (UV–vis spectroscopy), FESEM (field emission scanning electron microscopy), TEM (transmission electron microscopy) and AFM (atomic force microscopy) techniques. The formation of these bio-adsorbed gold nanoparticles is rapid as the reaction process completes within few minutes. The XRD (X-ray diffraction studies) and EDAX (energy dispersive X-ray analysis) show that the particles are crystalline in nature. This clean-green method of synthesis is performed under ambient conditions. Probable biochemical pathway of the synthesis is studied using FTIR (Fourier transformed infrared spectroscopy). It is observed that the freely water soluble flavonoids of clove buds are responsible for bioreduction. The possible applications viz., catalysis, sensor, diagnostics, biomedical imaging and photo thermal therapy of these functionalized noble metal nanoparticles are envisaged.

Introduction

Special shaped metal nanoparticles exhibit unique physical and chemical properties in comparison with the spherical ones since intrinsic properties depend vitally on particle shapes [1], [2], [3], [4], [5]. These shape dependent properties of gold nanoparticles (AuNP) have different behaviors and make them suitable for therapeutic utilization. Gold nanoparticles of certain non-regular shapes can readily be adsorbed to the surfaces of the biomolecules which show higher surface plasmon resonance and will have a greater contrast effect than those of photo thermal dyes that are used regularly in detection of cancer cells [6]. Displaying novel properties of different shaped AuNP have wider and more effective biological and medical applications [7], [8], [9], [10], [11], [12], [13]. Irregular shaped nanoparticles, which resemble certain bacteria, can infiltrate the human cells. This phenomenon suggests that altering the shape of nanoparticles can make them more effective in understanding and treating the diseases [12].

This highly intended project of noble metallic nanoparticle synthesis from a biological route is used for the detection and destruction of cancer cells in the preliminary stage. Here the bio-detection sensitivity and biocompatibility parameters become very important. The bio-detection sensitivity of nanoparticles often is associated with their physical and chemical properties, which in turn depend on the shape of the particles [14], [15]. Nanoparticles with different dimensions have been applied widely to detect biological molecules [16]. Colloidal AuNP is used to detect specific DNA sequences and single-base mutations in a homogeneous format [17]. AuNP synthesized with biological base is interesting, predominantly because it exhibits the best compatibility with biomolecules. But, bio-detection sensitivity derived from spherical nanoparticles is not strong enough to trace the interaction of biomolecules [18]. Looking into all these aspects, it is reasonable to infer that the biosynthesis of non-regular shaped nanoparticles hopefully might reach this aim because they display novel properties and may improve biological detection sensitivity greatly.

Biological methods of nanoparticles synthesis using microorganisms such as Fusarium oxysporum [19], Fusarium semitactum [20], [21], Cladosporium sp. [22], Rhodopseudomonas sp. [23], Megatherium sp., [24] and also from different plants like alfalfa [25], Cinnamomum camphora [26], neem [27] and guava [28] have been reported as environment friendly substitutes to chemical and physical methods. In biosynthesis of nanoparticles, it is always beneficial to use plant or part of plant than the organisms as it avoids pathogenic, laborious, time consuming and hygiene maintenance procedures of cell culture [29]. It can also be suitably adopted for large-scale synthesis of nanoparticles. Keeping these aspects in view, we submit a report on the biosynthesis of irregular shaped AuNP from macerated aqueous extracellular dried clove buds (Syzygium aromaticum) solution. This method is simple, carried out at room temperature, and also obeys the juries of green chemistry. The rate of AuNP synthesis using macerated clove buds solution is instant as compared to the chemical and physical methods. This has time related advantage over conventional method of metal nanoparticles synthesis using different microorganisms and other plants. We have selected dried clove buds, as this part of the plant is available everywhere and is used for many other domestic and medicinal purposes. As in the process of AuNP synthesis from different plants [25], [26], [27], [28], it is also observed that the readily available dried clove buds are the potential bio-agent for catalytic reduction of Au3+ ions to AuNP. Unlike gold nanoparticles synthesized using guava leaf extract [28], which also gives polyshaped nanoparticles, the microwave exposed clove buds solution yields highly unpredictable shaped ones which resemble microbes. This is for the first time that a simple macerated dried clove buds solution is used in the metal nanoparticle biosynthesis.

Section snippets

Maceration process

For preparing the macerated aqueous extracellular dried clove buds solution for biosynthesis, 2 g of freshly collected and perfectly dried clove buds coarse powder was taken in a 250 ml wide neck Borosil conical flask and washed several times with deionised water. 200 ml of double distilled water was added to the flask containing washed clove buds powder and macerated. In this process, maceration is done by incubating the flask on an orbital shaker at 27 °C and agitating at 50 rpm for 8 h. After the

Results and discussion

Extracellular production of AuNP treating the macerated clove buds solution with aqueous 10−3 M HAuCl4 solution was investigated. The initial color of the reaction mixture soon after the addition of dried clove buds solution to HAuCl4 salt solution was light brown and does not show any peak in the visible spectrum. The light brown color changes to purple in a short time. The intensity of this purple color rapidly enhances with time. Fig. 1a presents the color change in the mixture with reaction

Conclusion

In conclusion, seeing the best possible medical application of these highly unpredictable and amoebic types of gold nanoparticles, we have successfully biosynthesized the same using macerated aqueous extracellular dried clove buds (S. aromaticum) solution. We infer that the freely water soluble flavonoids are responsible for the biosynthesis and stability of irregular shaped nanoparticles in aqueous medium. The modest maceration process offers a ‘clean-green’ biogenesis of nanoparticles for

Acknowledgements

Financial supports from DST (Grant No. SR/S1/PC-10/2005) and UGC (D.O.No.F.14-4/2001 (Innov.Policy/ASIST)) are acknowledged. We thank to Prof G.U. Kulkarni for fruitful guidance and Selvi Rajan, JNCASR Bangalore for FESEM measurements. Raghunandan Deshpande thank to Dr. Appala Raju, Principal of HKES College of pharmacy, Gulbarga for encouraging the research program.

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