www.ietdl.org Published in IET Nanobiotechnology Received on 12th February 2013 Revised on 26th June 2013 Accepted on 23rd August 2013 doi: 10.1049/iet-nbt.2013.0010

ISSN 1751-8741

Preparation of an agar-silver nanoparticles (A-AgNp) film for increasing the shelf-life of fruits Janhavi A. Gudadhe1, Alka Yadav1, Aniket Gade1, Priscyla D. Marcato2, Nelson Durán3,4, Mahendra Rai1,3 1

Department of Biotechnology, SGB Amravati University, Amravati 444602, Maharashtra, India Faculty of Pharmaceutical Sciences of Riberão Preto, Universidade de São, Butantã, São Paulo, Brazil 3 Instituto de Química, Biological Chemistry Laboratory, Universidade Estadual de Campinas, Campinas, São Paulo, Brazil 4 Centre of Natural and Human Science, Universidade Federal do ABC, Santo Andre, São Paulo, Brazil E-mail: [email protected] 2

Abstract: Preparation of protective coating possessing antimicrobial properties is present day need as they increase the shelf life of fruits and vegetables. In the present study, preparation of agar-silver nanoparticle film for increasing the shelf life of fruits is reported. Silver nanoparticles (Ag-NPs) biosynthesised using an extract of Ocimum sanctum leaves, were mixed with agar–agar to prepare an agar-silver nanoparticles (A-AgNp) film. This film was surface-coated over the fruits, Citrus aurantifolium (Thornless lime) and Pyrus malus (Apple), and evaluated for the determination of antimicrobial activity of A-AgNp films using disc diffusion method, weight loss and shelf life of fruits. This study demonstrates that these A-AgNp films possess antimicrobial activity and also increase the shelf life of fruits.

1

Introduction

In most of the agriculture-based countries, the principle aim of the farmers is to keep their fruits and vegetables fresh until they reach the consumers [1–3]. As the natural waxy coating of fruits and vegetables is insufficient to prevent weight and water loss during storage [3–5], development of edible coatings and films are presently in demand as they can be used for a wide variety of foods, including vegetables and fruits as they serve as a barrier for moisture, lipid and gas [2, 6, 7]. In addition, they can improve textural properties of food and also serve as a carrier of functional agents like colour, flavour, antioxidants, nutrients and antimicrobials [1, 5, 8]. Spoilage of fruits and vegetables also shortens its shelf life due to surface dehydration, moisture loss, browning and proliferation of spoilage-related microbes [2, 4]. Inorganic nanomaterials serve as good antimicrobial agents, and silver nanoparticles are the metal of choice [9– 12]. Silver has been used as an antimicrobial agent since ancient times because of its outstanding capacity to fight against a wide range of micro-organisms, and silver nanoparticles because of their remarkable physical and chemical properties are coming up as an impressive possibility [13–15]. Silver nanoparticles are exploited in a number of applications like antimicrobial dressings [16–18], surface-coated medical devices [19], antimicrobial paints [20] and so on. The aim of this study exhibits preparation of an agar-supported silver nanoparticle (A-AgNp) film for fruit preservation and checked important parameters in fruit 190 & The Institution of Engineering and Technology 2014

preservation as weight loss and the antimicrobial activity against pathogenic bacteria like Escherichia coli and Staphylococcus aureus.

2

Materials and methods

2.1 Preparation of extract of Ocimum sanctum and synthesis of silver nanoparticles Twenty grams of freshly cut Ocimum sanctum leaves were taken in 100 ml distilled water in a conical flask, and heated for 5 min at boiling temperature. The extract of Ocimum sanctum leaves were collected in another 250 ml flask by filtering through Whatman filter paper No. 42. The extract was stored and cooled. The freshly prepared plant leaf extract was treated with 1 mM AgNO3 solution and incubated at room temperature for 2 h. After incubation the extract was observed for change in colouration from light green to brown and the absorbance were measured by UV– vis spectroscopy. 2.2

Characterisation of silver nanoparticles

2.2.1 UV–vis spectrophotometer analysis: The primary detection of silver nanoparticles was carried out by using an UV–vis spectrophotometer (Shimadzu UV-1700). The spectrum was scanned in the range of wavelength 250– 800 nm. 2.2.2 Fourier transform infrared spectroscopy: The characterisation of silver nanoparticles was carried out by IET Nanobiotechnol., 2014, Vol. 8, Iss. 4, pp. 190–195 doi: 10.1049/iet-nbt.2013.0010

www.ietdl.org using Fourier transform infrared (FTIR) spectroscopy (Perkin-Elmer, USA) in the range of 1000–2000 cm−1 at a resolution of 4 cm−1. Single scan of Ocimum sanctum leaf extract and leaf extract treated with 1 mM silver nitrate were taken. The sample for FTIR was prepared by mixing silver nanoparticles with KBr in the ratio of 1:4. 2.2.3 Nanoparticle size analysis: The sample (5 µL) was diluted by 1.5 ml (1:10 dilutions) with nuclease-free water at a concentration of 106 to 109 per ml. Six dilutions of the above sample were made and the last dilution was used for analysis by Nanosight LM20 (UK). Diluted sample was injected onto the sample chamber for observation and the image was captured using the nanoparticle tracking analysis software (NTAS). 2.2.4 Transmission electron microscopy (TEM): The silver nanoparticles were characterised by TEM (Philips, CM 12) on conventional carbon-coated copper grids. A 5 µl of sample was placed on the grid and then dried at room temperature for 1 h. The samples were inspected by operating at 120 KV. 2.2.5 Preparation of agar-silver nanoparticle film: The biosynthesised silver nanoparticles (20 ml in a volume of 100 ml, that is, at a concentration of 2.14 µg of silver nanoparticles) after characterisation were mixed with 4% of agar powder and 1.5 ml of glycerol without diluting. This mixture was poured onto the slide to form a thin film. The antimicrobial activity of this film was evaluated against E. coli and S. aureus using disc diffusion method. The final concentration of silver nanoparticles in the emulsion was 2 µg, which is very negligible in context with the toxicity. 2.2.6 Antimicrobial activity of agar-silver nanoparticle film: The antimicrobial activity of A-AgNP films was tested by using Kierby–Bauer disc diffusion method [21] and their activity was compared with standard antibiotic discs. The antimicrobial activity was assessed against E. coli (ATCC 34923) and S. aureus (ATCC 25923). A single colony of each strain was grown overnight in Muller–Hinton (MH) liquid medium on a rotary shaker (100 rev min−1) at 37 °C. The inocula containing microbial load of 1 × 105 CFU/ml was then applied to the MH plates and discs (6 mm) of agar–agar film without nanoparticles, antibiotic (concentration 10 µg/disc), antibiotic + nanoparticles and A-AgNP film were kept on the plate. The final concentration of silver nanoparticles in the 6 mm A-AgNP film disc was 0.01 µg. The MH plates were then incubated at 37 °C for 24 h and the zone of inhibition was measured. The assays were performed in triplicate and the mean of the results obtained were used as final observation obtained to plot in the form of graphs. 2.2.7 Surface sterilisation and coating of fruits: The fruits (apple and lime) were surface sterilised using 70% alcohol to remove surface contaminants like dust and dirt from fruits and thereby subsequently washed with distilled water. After drying, the fruits were dipped into agar-silver nanoparticle solution for a period of 10 s so that a thin coating was formed over fruit surface. The final concentration of silver nanoparticles in the coated fruit was 0.05 µg. Then the fruits were kept for observation at room temperature for weight loss analysis. 2.2.8 Determination of weight loss and soluble protein content: The fruits coated with A-AgNP film were treated as experimental whereas the fruits without IET Nanobiotechnol., 2014, Vol. 8, Iss. 4, pp. 190–195 doi: 10.1049/iet-nbt.2013.0010

A-AgNP were treated as control. Weight loss of fruits coated with A-AgNP film and without A-AgNP film was regularly measured at room temperature by weighing fruits at a three-day interval. The weight loss experiments were performed in triplicates. The mean of the observations obtained were used as final observations to plot graphs. Soluble protein content was estimated by using Bradford’s method [22]. The apples and lime were weighed to about 0.1 g, mixed with 2 ml of distilled water and homogenised for 5 min at room temperature. The tubes were centrifuged at 5000 rpm for 20 min and the supernatant was collected and stored at 4 °C for 2 h before analysis. The protein extract was diluted and was mixed with Coomassie brilliant blue G-250 and incubated for 15 min at room temperature; the absorbance was read at 595 nm using a spectrophotometer [1]. 2.2.9 Microbial treatment of the effluent produced by the fruit washes of silver nanoparticles film: To bioremediate the effluent produced by the fruits washing process, a microbial treatment was afforded. For the microbial treatment, Chromobacterium violaceum (CCT 3496) was used as previously published [23]. Briefly, C. violaceum previously grown were inoculated into 100 ml of liquid collected from five consecutive water washes of the fruits loaded with silver nanoparticles. The concentration of C. violaceum was 105 CFU/ml (incubated at 30 °C for 24 h). The effluent treated with bacteria was filtered and the filtrate was analysed in the presence of silver nanoparticles using atomic absorption spectrophotometry (Model 5100PC Perkin-Elmer), with a graphite furnace unit (Model HGA-600) and by inductively coupled plasma (ICP) spectrometry (Model Perkin-Elmer Optima 3000DV).

3

Results and discussion

Biosynthesis of AgNPs was carried out using Ocimum sanctum leaves. Ocimum leaf extract after treatment with 1 mM silver nitrate depicted change in colouration from greenish yellow to brown (Fig. 1a). The change in colouration was observed due to the excitation of surface plasmon vibrations in metal nanoparticles [11, 24]. The treated leaf extract was further characterised using UV– visible spectroscopy. An absorbance peak at 435 nm (Fig. 1b) was observed, which is characteristic for silver nanoparticles. The results obtained were in agreement with those of [25] for synthesis of AgNPs using Jatropha curcas seed extract. The TEM analyses of the biosynthesised AgNPs also confirmed the synthesis of AgNPs with spherical and quasispherical morphology (Fig. 1c). The size of the AgNPs was found to be 50–200 nm, with an average size of 95 nm (Fig. 1d ). The average size of the nanoparticles was determined using the nanoparticle size analyser. The possible bioactive compounds responsible for the reduction of silver ions and synthesis of AgNPs were determined using FTIR spectroscopy (Fig. 1e). The FTIR spectrum of leaf extract showed an absorbance peak at 1016 cm−1 which might be associated with stretch vibrations of C–O–C bond [26, 27]. The peak observed at 1405 cm−1 is accompanied with the asymmetric stretch vibrations of ionised carboxyl groups of some amino acid residue of peptide chains [26, 28]. The absorbance peak at 1646 cm−1 is associated with the carbonyl stretch vibrations in the amide linkage of peptide chains of biomass [29]. After the synthesis of silver nanoparticles, these peaks were 191

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Fig. 1 Biosynthesis of AgNPs and the results a Leaf extract: left (control) before and right (experimental) after treatment with 1 mM silver nitrate solution b Detection of silver nanoparticles by UV–vis spectrophotometer from the leaf extract of Ocimum sanctum showing absorbance at about 435 nm (control – black and experimental – grey) c Transmission electron micrograph of phytosynthesised silver nanoparticles d Particle size spectra of silver nanoparticles e FTIR spectrum for leaf extract before treatment (control – black) after treatment with 1 mM silver nitrate solution (experimental – red)

shifted to 1409, 1623 and 1068 cm−1, where peak at 1330 cm−1 might be associated with the C–N stretching vibrations of aromatic amines [30]. These peaks indicate the presence of proteins as a ligand for silver nanoparticles, which increases the stability of biosynthesised nanoparticles [28]. These biosynthesised silver nanoparticles were mixed with agar–agar to form agar-silver nanoparticles (A-AgNp) films. The so-formed films were coated on surface of fruits (apple and orange) and checked for antimicrobial activity, weight loss and shelf life of fruits. The A-AgNP films were checked for their antimicrobial efficiency against pathogenic bacteria like E. coli and S. aureus using disc diffusion method. The A-AgNP films showed considerable activity against both pathogenic bacteria. The microbial efficacy of the A-AgNP film (0.01 µg/disc) was also compared with commercially available antibiotics like Ampicillin (10 µg/disc) 192 & The Institution of Engineering and Technology 2014

and Gentamycin (10 µg/disc). Ampicillin showed negligible activity against both bacteria compared to the A-AgNP film. However, Gentamycin showed a comparatively better activity. The activity of both antibiotics was enhanced when used in combination with silver nanoparticles (Figs. 2 and 3). Thus, from the above results it was observed that the A-AgNP film possesses prominent antibacterial activity and could protect the fruit from microbial infection. The maximum zone of inhibition of agar-silver nanoparticle film (15 mm) was found against E. coli whereas the minimum zone of inhibition (14 mm) was recorded against S. aureus. Pattabi et al. [31] also reported maximum activity of silver nanoparticles against gram-negative bacteria compared to gram-positive bacteria which is due to the presence of peptidoglycan layer that serves as a protective covering for gram-positive bacteria. IET Nanobiotechnol., 2014, Vol. 8, Iss. 4, pp. 190–195 doi: 10.1049/iet-nbt.2013.0010

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Fig. 2 Antibacterial activity of agar-silver nanoparticle film (A-AgNp) against Staphylococcus aureus

Fig. 3 Antibacterial activity of the agar-silver nanoparticles film (A-AgNp) against Escherichia coli

For the weight loss study, uncoated fruits (lime and apple), fruits coated with agar film (lime and apple) and those with A-AgNP film (lime and apple) were kept at room temperature and the weight loss of fruits was measured at a three-day interval (Fig. 4). The results of the above study depicted that the fruits coated with A-AgNP film showed minimum weight loss even after 9 days compared to uncoated fruits and fruits with agar film and thus increased

shelf life (Figs. 5 and 6). There was a little loss in soluble protein content during the storage period. The initial protein contents were 2.5 ± 0.3 and 4.0 ± 0.5 mg/g of fresh weight, for apple and lime, respectively that they are similar to the values described previously in the literature [32, 33]. The soluble protein loss was around 15–20% (final concentrations were 2.0–2.2 mg/g for apple and 3.2–3.4 mg/g for lime) up to 9 days. The above findings resemble with

Fig. 4 Weight loss study a Uncoated thornless lime b Thornless lime coated with agar film c Thornless lime coated with A-AgNP film d Uncoated Apple e Apple coated with agar film f Apple coated with A-AgNp film IET Nanobiotechnol., 2014, Vol. 8, Iss. 4, pp. 190–195 doi: 10.1049/iet-nbt.2013.0010

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www.ietdl.org procedure, that is biofiltering system, that it must applied will be the following: After 72 h of culture of C. violaceum in the presence of silver nanoparticles, the effluents were filtrated in a 0.45 µm filter and the biomass was re-suspended immediately in the culture media. In an optical microscopy analysis, it was possible to see that the C. violaceum culture in the absence of silver nanoparticles exhibited free cells, but in the presence of silver nanoparticles, a clear agglomeration occurred facilitating the bacterial removal by filtration, decantation or centrifugation in the re-use of water in an identical results (results not shown) as previously shown by our group [23]. The water after this process exhibited no silver nanoparticles presence avoiding any ecotoxicological effect. Fig. 5 Observation of weight loss in apple coated with A-AgNP film and apples without A-AgNP film

4

Conclusion

The above study demonstrates that the extract of Ocimum sanctum possesses the capacity to extracellularly synthesise silver nanoparticles. The preparation of A-AgNP films using silver nanoparticles could prove as an efficient mode for increasing shelf life of fruits. No significant changes in weight and soluble protein loss were observed. The A-AgNP films involve incorporation of silver nanoparticles in agar and hence there is no direct contact of silver nanoparticles and fruit surface; thus chances for penetration of silver nanoparticles inside the fruits becomes negligible. The A-AgNP films also depict considerable antimicrobial activity and hence protect fruits from microbial attack. After silver nanoparticles film is used in the fruits, they were washed before used as food and the effluent treated with a microbial film (C. violaceum) and the water can be re-used and used as potable one. Fig. 6 Observation of weight loss in lime coated with A-AgNP film and lime without A-AgNP film

those reported by Fayaz et al. [1], where the authors depicted minimum weight loss and soluble protein content of fruits coated with sodium alginate-silver nanoparticles film as compared to uncoated control fruits. Agar–agar and glycerol which were used for the preparation of these A-AgNP films formed smooth coating on the surface of fruits and prevented water loss. Also, agar–agar is dissolvable in water so when the fruits are washed the film gets easily removed avoiding chances of ingestion of the A-AgNP film. The silver nanoparticles employed for the formation of A-AgNP film are comparatively bigger in size (95 nm) which makes them less toxic [5, 34], and owing to the easy removal of the A-AgNP film the chances of toxicity become negligible. It is important to point out here that the final concentration of silver nanoparticles was so small (at the order of nanograms) that they are not able to exert any cytotoxic or genotoxic effect in humans. The cytotoxic IC50 for silver nanoparticles are > 1 µg/ml and genotocivity > 5 µg/ml [35, 36]. In view of protecting the environment after fruit washes, a procedure was applied to eliminate the silver nanoparticles from an effluent containing these nanostructures. This procedure is supposed that the transportation industry will carry out a clean up of the effluent after washing the coated agar-silver film before sending to the market. Then, the industry must have a local appropriated to treat these effluents in order to eliminate the silver nanoparticles. The 194 & The Institution of Engineering and Technology 2014

5

Acknowledgment

Support from FAPESP, CNPq, Brazilian Network of Nanotoxicology (MCTI/CNPq), INOMAT (MCTI/CNPq), NANOBIOSS (MCTI/CNPq) and Binational Exchange Program-CNPq-Brazil/DST-India are acknowledged.

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References

1 Fayaz, A.M., Balaji, K., Girilal, M., Kalaichelvan, P.T., Venkatesan, R.: ‘Mycobased synthesis of silver nanoparticles and their incorporation into sodium alginate films for vegetable and fruit preservation’, J. Agric. Food Chem., 2009, 57, pp. 6246–6252 2 Fernandez, A., Picouet, P., Lloret, E.: ‘Cellulose-silver nanoparticle hybrid materials to control spoilage-related microflora in absorbent pads located in trays of fresh cut melons’, Int. J. Food Microbiol., 2010, 142, pp. 222–228 3 Kangarlou, H., Shirvaliloo, S.: ‘Protection effect of gold nanoparticles coated on fruit and vegetables using PVD method’, J. Appl. Sci., 2012, 12, (7), pp. 1782–1791 4 Fernandez, A., Soriano, E., Lopez-Carballo, G., et al.: ‘Preservation of aseptic conditions in absorbent pads by using silver nanotechnology’, Food Res. Int., 2009, 42, pp. 1105–1112 5 Rai, M., Gade, A., Yadav, A.: ‘Biogenic nanoparticles: an introduction to what they are how they are synthesized and their applications’, in Rai, M., Durán, N. (Eds.): ‘Metal nanoparticles in microbiology’ (Springer, 2011), pp. 1–14 6 Jochenweiss, P.T., Mc Clements, D.J.: ‘Functional materials in food nanotechnology’, J. Food Sci., 2006, 71, pp. 107–116 7 Durán, N., Marcato, P.D.: ‘Nanobiotechnology perspectives. Role of nanotechnology in the food industry: a review’, Int. J. Food Sci. Technol., 2013, 48, (6), pp. 1127–1134 8 Davidson, P.M.: ‘Chemical preservatives and natural antimicrobial compounds’, in Doyle, M.P., Beuchat, L.R., Montville, T.J. (Eds.): ‘Food microbiology fundamentals and frontiers’ (ASM Press, Washington, DC, 2011), pp. 593–627 IET Nanobiotechnol., 2014, Vol. 8, Iss. 4, pp. 190–195 doi: 10.1049/iet-nbt.2013.0010

www.ietdl.org 9 Narayanan, K.B., Sakthivel, N.: ‘Biological synthesis of metal nanoparticles by microbes’, Adv. Colloid Surf., 2010, 156, pp. 1–13 10 Durán, N., Marcato, P.D., De Conti, R., Alves, O.L., Costa, F.T.M., Brocchi, M.: ‘Potential use of silver nanoparticles on pathogenic bacteria, their toxicity and possible mechanisms of action’, J. Braz. Chem. Soc., 2010, 21, pp. 949–959 11 Durán, N., Marcato, P.D., Ingle, A., Gade, A., Rai, M.: ‘Fungi mediated synthesis of silver nanoparticles: characterization processes and applications’, in Rai, M., Kövics, G. (Eds.): ‘Progress in mycology’ (Scientific Publishers, Jodhpur, 2010), ch. 16, pp. 425–449 12 Durán, N., Marcato, P.D., Durán, M., Yadav, A., Gade, A., Rai, M.: ‘Mechanistic aspects in the biogenic synthesis of extracellular metal nanoparticles by peptides, bacteria, fungi and plants’, Appl. Microbiol. Biotechnol., 2011, 190, pp. 1609–1624 13 Rai, M., Yadav, A., Gade, A.: ‘Silver nanoparticles: as a new generation of antimicrobials’, Biotechnol. Adv., 2009, 27, pp. 76–83 14 Nasrollahi, A., Pourshamsian, K.H., Mansourkiaee, P.: ‘Antifungal activity of silver nanoparticles on some of fungi’, Int. J. Nano Dimens., 2011, 1, pp. 233–239 15 Lkhagvajav, N., Yasa, I., Celik, E., Koizhaiganova, M., Sari, O.: ‘Antimicrobial activity of colloidal silver nanoparticles prepared by sol gel method’, Dig. J. Nanomater. Biomater., 2011, 6, pp. 149–154 16 Sharma, V.K., Yngard, R.A., Lin, Y.: ‘Silver nanoparticles: Green synthesis and their antimicrobial activities’, Adv. Colloid Interf. Sci., 2009, 145, pp. 83–96 17 Durán, N., Marcato, P.D., De Souza, G.I.H., Alves, O.L., Esposito, E.: ‘Antibacterial effect of silver nanoparticles produced by fungal process on textile fabrics and their effluent treatment’, J. Biomed. Nanotechnol., 2007, 3, pp. 203–208 18 Marcato, P.D., Durán, N.: ‘Biogenic silver nanoparticles: applications in medicines and textiles and their health implications’, in Rai, M., Durán, N. (eds.): ‘Metal nanoparticles in microbiology’ (Springer, Germany, 2011), ch. 11, pp. 249–267 19 Knetsch, M.L.W., Koole, L.H.: ‘New strategies in the development of antimicrobial coatings: the example of increasing usage of silver and silver nanoparticles’, Polymers, 2011, 3, pp. 340–366 20 Kumar, A., Vemula, P.K., Ajayan, P.M., John, G.: ‘Silver-nanoparticleembedded antimicrobial paints based on vegetable oil’, Nat. Mater., 2008, 7, pp. 236–241 21 Bauer, A.W., Kirby, M., Sherris, J.C., Turck, M.: ‘Antibiotic susceptibility testing by a standardized single disk method’, Am. J. Clin. Pathol., 1966, 45, pp. 493–496 22 Bradford, M.: ‘A rapid and sensitive method for the quantification of protein using the principle of protein-dye binding’, Anal. Biochem., 1997, 72, pp. 248–254

IET Nanobiotechnol., 2014, Vol. 8, Iss. 4, pp. 190–195 doi: 10.1049/iet-nbt.2013.0010

23 Durán, N., Marcato, P.D., Alves, O.L., et al.: ‘Ecosystem protection by effluent bioremediation: silver nanoparticles impregnation in a textile fabrics process’, J. Nanopart. Res., 2010, 12, pp. 285–292 24 Parashar, U.K., Saxena, P.S., Shrivastava, A.: ‘Bioinspired synthesis of silver nanoparticles’, Dig. J. Nanomater. Biostruct., 2009, 4, pp. 159–166 25 Bar, H., Bhui, D.K., Sahoo, G.P., Sarkar, P., De, S.P., Misra, A.: ‘Green synthesis of silver nanoparticles using latex of Jatropha curcas’, Colloids Surf. A: Physicochem. Eng. Aspects, 2009, 339, pp. 134–139 26 Huang, J., Chen, C., He, N., et al.: ‘Biosynthesis of silver and gold nanoparticles by novel sundried Cinnamomum camphora leaf’, Nanotechnology, 2007, 18, pp. 105–106 27 Kasthuri, J., Kanthiravan, K., Rajendiran, N.: ‘Phyllanthin-assisted biosynthesis of silver and gold nanoparticles: a novel biological approach’, J. Nanopart. Res., 2008, 15, pp. 1075–1085 28 Bar, H., Bhui, D.K., Sahoo, G.P., Sarkar, P., Pyne, S., Misra, A.: ‘Green synthesis of silver nanoparticles using seed extract of Jatropha curcas‘, Colloids Surf. A: Physicochem. Eng. Aspects, 2009, 348, pp. 212–216 29 Bawaskar, M., Gaikwad, S., Ingle, A., et al.: ‘A new report on mycosynthesis of silver nanoparticles by Fusarium culmorum’, Curr. Nanosci., 2010, 6, pp. 376–380 30 Sanghi, R., Verma, P.: ‘Biomimetic synthesis and characterization of protein capped silver nanoparticles’, Biores. Technol., 2009, 100, pp. 501–504 31 Pattabi, R.M., Sridhar, K.R., Gopakumar, S., Vinaychandra, B., Pattabi, M.: ‘Antibacterial potential of silver nanoparticles synthesized by electron beam irradiation’, Int. J. Nanopar. Res., 2010, 3, pp. 53–64 32 Marzban, G., Puehringer, H., Dey, R., et al.: ‘Localisation and distribution of the major allergens in apple fruits’, Plant Sci., 2005, 169, pp. 387–394 33 USDA 2012 http://ndb.nal.usda.gov/ndb/foods/show/2141?fg=&man= &lfacet=&format=&count=&max=25&offset=&sort=&qlookup=apple (accessed at December 23, 2012) 34 An, J., Zhang, M., Wang, S., Tang, J.: ‘Physical, chemical and microbiological changes in stored green asparagus spears as affected by coating of silver nanoparticles-PVP’. LWT, 2008, pp. 1100–1107 35 Lima, R., Feitosa, L.O., Ballottin, D., Marcato, P.D., Tasic, L., Durán, N.: ‘Cytotoxicity and genotoxicity of biogenic silver nanoparticles’, J. Phys. Conf. Ser., 429, pp. 012020 36 De Lima, R., Seabra, A.B., Durán, N.: ‘Silver nanoparticles: a brief review of cytotoxicity and genotoxicity of chemically and biogenically synthesized nanoparticles’, J. Appl. Toxicol., 2012, 32, pp. 867–879

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Preparation of an agar-silver nanoparticles (A-AgNp) film for increasing the shelf-life of fruits.

Preparation of protective coating possessing antimicrobial properties is present day need as they increase the shelf life of fruits and vegetables. In...
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