Radiation Physics and Chemistry 92 (2013) 54–60

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Radiation Physics and Chemistry

0969-80http://d

n CorrE-m

journal homepage: www.elsevier.com/locate/radphyschem

Radiation synthesis of nanosilver nanohydrogelsof poly(methacrylic acid)

Bhuvanesh Gupta a,n, Deepti Gautam a, Sadiya Anjum a, Shalini Saxena a, Arti Kapil b

a Bioengineering Laboratory, Department of Textile Technology, Indian Institute of Technology, New Delhi 110016, Indiab Department of Microbiology, All India Institute of Medical Science, New Delhi 110029, India

H I G H L I G H T S

� Nanosilver nanohydrogels of PMAA were synthesized and stabilized using Υ-irradiation.

� The mean size of silver nanoparticles ranging is 10–50 nm.� Antibacterial studies of nSnH suggest it to be a good candidate for biomedical applications.

a r t i c l e i n f o

Article history:Received 28 February 2013Accepted 18 July 2013Available online 24 July 2013

Keywords:NanosilverRadiationPoly(methacrylic acid)HydrogelAntibacterial

6X/$ - see front matter & 2013 Elsevier Ltd. Ax.doi.org/10.1016/j.radphyschem.2013.07.020

esponding author. Tel.: +91 11 26591416; fax:ail address: bgupta@textile.iitd.ernet.in (B. Gu

a b s t r a c t

Nanosilver nanohydrogels (nSnH) of poly(methacrylic acid) were synthesized and stabilized usinggamma irradiation. The main objective of this study was to develop silver nanoparticles and to evaluatethe antimicrobial activity. Radiation helps in the polymerization, crosslinking and reduction of silvernitrate as well. Highly stable and uniformly distributed silver nanoparticles have been obtained withinhydrogel network by water in oil nanoemulsion polymerization and were evaluated by dynamic lightscattering (DLS) and transmission electron microscopy (TEM) respectively. TEM showed almost sphericaland uniform distribution of silver nanoparticles through the hydrogel network. The mean size of silvernanoparticles ranging is 10–50 nm. The nanohydrogels showed good swelling in water. Antibacterialstudies of nSnH suggest that it can be a good candidate as coating material in biomedical applications.

& 2013 Elsevier Ltd. All rights reserved.

1. Introduction

Infection is the serious problem leading to severe health concernsglobally. Efforts are being made to develop material that wouldexhibits antimicrobial nature against various microbes. Nanosilverhas been found to be an excellent material with enormous potentialagainst virus and bacteria where silver inactivates bacteria byinteracting with the thiol groups of bacterial proteins and enzymes(Chun et al., 2006). This is enormous interest in silver as antimicro-bial material for burn dressings (Klasen, 2000). Introduction of silverinto hydrogels provides antibacterial activity, which is highly desiredin medical, clothing and household approaches. This is a significantlyeffective approach due to the high surface to bulk ratio of silvernanoparticles (Badr and Mahmoud, 2006; Hong et al., 2006; Beecroftand Ober, 1995). Several studies have been carried out for thesynthesis of nanoclusters, nanocomposites, nanocolloids and nano-particles using gamma radiation (Mostafavi et al.; 1989, Henglein,1993; Belloni et al., 1998; El-Hag et al., 2003). Hydrogels are the most

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+91 11 26581061.pta).

promising polymers because they do not dissolve in water but swellconsiderably in an aqueous medium (Kim et al., 2003; Schmedlenet al., 2002) and have been used for a number of biomedicalapplications due to high hydrophilicity and biocompatibility (Kimet al., 2002; Biswas et al., 2006; Ping et al., 1994).

The binding of nanosilver to the surface is very difficult althoughpeople are trying to encapsulate the nanosilver via crosslinking.In several cases the nanosilver has been encapsulated within thematrix by in-situ reduction process. Scientists have carried out thereduction of silver nitrate by fructose and ascorbic acid (Ho et al.,2004; Mohan et al., 2007). Zhou et al. on the other hand preparednanoparticles employing a matrix of gelatin and carboxymethylchitosan and observed their antimicrobial nature against Escherichiacoli (Zhou et al., 2012). Alternatively, radiation has been used for thepreparation of silver nanoparticles (Belloni et al., 1998). Biswal et al.synthesized guar gum stabilized nanosilver particles by gammaradiation. Particles of size 10–30 nm were obtained (Biswal et al.,2009). Wang et al. described the one-pot approach to the preparationof silver-PMMA “shell–core” nanocomposite. The methyl methacrylate(MMA) is at first emulsified by poly(oxyethyleneoctylphenol ether)(OP-10) to form micelle and the mercaptoethanol used in the forma-tion of silver-PMMA shell–core structure. Polymerization of MMA

B. Gupta et al. / Radiation Physics and Chemistry 92 (2013) 54–60 55

takes place when the Ag+ is reduced to Ag (Wang and Chen, 2006). Infurther study the one-step in situ preparation of silver nano-particlesin polymethylmethacrylate (PMMA) using N,N′-dimethylformamide(DMF) as a medium has been investigated. The radical polymerizationof (MMA), in presence of benzoyl peroxide followed by reaction ofsilver source has been successfully employed to synthesize Ag/PMMAnano-composite (Singh and Khanna, 2007).

However, most of the preparation procedures of hybrid systemswere started with a prefabricated nanometal, followed by the additionof nanometal particle into polymer component. For instance, ananoparticle-loaded gel was typically prepared by swelling a gel inthe dispersion of nanometal particles mixing a colloidal solution ofnanometal particles with an aqueous polymer solution, followed bysolvent evaporation (El-Sherif et al., 2011). However, nanosilverparticle should be attached to the carriers, such as polymer matrix,prior to several applications (Mohan et al., 2007; Huang et al., 2008).Therefore, the research efforts are heading towards the synthesis ofnanosilver particles contained polymeric network with certain anti-microbial activity and low cytotoxicity. Studies of Belloni et al. havedescribed in detail about the metal cluster synthesis in solution viaradiolytic reduction which led to the interesting studies in thedevelopment of nanostructures. (Belloni et al., 1998; Nagayasu et al.,2012). In very recent study, the authors investigate the preparation ofpolymethacrylate capped silver nanoparticles in aqueous solution bythe γ-radiolysis method (Nagayasu et al., 2012). The nanoparticlesynthesis and polymerization of methacrylic acid occurred simulta-neously in situ (Biswal et al., 2013). Our aim is to develop nanomater-ials with antimicrobial nature so that it may be used to controlinfection in biomedical field. In our study, nanoemulsion polymeriza-tion has been carried out to develop nanosilver nanohydrogels withthe help of gamma radiation to identify the optimal conditions toprepare the hydrogels for the synthesis of nanosilver nanohydrogels(nSnH). The nanosilver nanohydrogels were investigated by FTIRspectroscopy, dynamic light scattering (DLS), energy dispersive X-raymicroanalysis (EDX), thermogravimetric analysis (TGA) and transmis-sion electron microscopy (TEM).

2. Experimental

2.1. Materials

Sodium bis(2-ethylhexyl) sulfosuccinate (AOT) was received fromFluka. Methacrylic acid (MAA), ethyl methyl ketone (EMK), heptane,silver nitrate and sodium chloride (NaCI) were supplied by MerckIndia. Methacrylic acid was purified by distillation under vacuum.Ultra-pure water with resistivity less than 18MΩ cm produced by aMillipore Milli-Q system was used in all experiments.

2.2. Irradiation

A 60Co gamma radiation source of 800 Ci (dose rate of 0.16 kGy/h),supplied by Bhabha Atomic Research Centre, India, was used for theirradiation of the samples.

2.3. Preparation of nanosilver nanohydrogel

Emulsion polymerization was used to prepare the nanosilvernanohydrogels (nSnH) in w/o system. Silver nitrate solution inwater [AgNO3] (6�10�3 mmol/L) was prepared by dissolvingsilver nitrate in Milli-Q water. The desired concentration ofmonomer [MAA] 1 mL (1.2�10�2 mol/L) was mixed homoge-neously in silver nitrate solution. [AOT] was used as the surfactantfor the stabilization of the nanoemulsion. In oil phase, 8 g(1.8�10�2 mol/L ) of [AOT] was mixed in 100 mL of heptane.The water phase [MAA:AgNO3] (2% by volume) was mixed in oil

phase [AOT:heptane] and the whole mixture was then placed onconstant stirring for 10 min. The solution was transferred in areaction tube also deaerated by bubbling nitrogen for 15 min andwas sealed. The nanoemulsion was subjected to γ-irradiation atambient temperature in inert atmosphere. The polymerization wascarried out for different radiation doses. After the completion ofreaction, the nanoemulsion was destabilized by the addition ofsodium chloride (NaCl) and the nanoparticles settled down. Theprecipitate was washed repeatedly with ethyl methyl ketone toremove the AOT and nanoparticles were separated. The remainingprecipitate (nanoparticles) were repeatedly washed with EMK, anddried in vacuum oven.

2.4. Thermogravimetric analysis (TGA)

TGA studies were carried out using a Perkin-ElmerTGA-7 in therange 50–600 1C. The heating rate was 10 1C/min. The measure-ments were made under a constant flow rate (20 mL/min) ofnitrogen.

2.5. Fourier transforms infrared spectroscopy (FTIR)

The IR spectra of samples were recorded on a Perkin-ElmerFTIR System Spectrum GX. The spectra of PMAA without silver andnSnH samples were recorded by using the potassium bromide disktechnique, in the range of 4000–400 cm�1 with a resolution of4 cm�1 and averaged over 25 scans in % transmission mode. Thedisk was prepared from grinded samples (2 mg) and KBr (45 mg)using 400 kg/cm pressure for 10 min.

2.6. Energy dispersive X-ray microanalysis (EDX)

To identify the presence of silver elements in the nanosilvernanohydrogel samples, the SEM-EDX was used. The sample wasplaced on a sample stub and coated with carbon coating withAuto-Fine Coater JFC-1600 (Joel, USA Inc., USA). The images andthe silver content of the samples were obtained with RONTEC'sEDX Model Quan Tax 200 (SDD technology, USA).

2.7. Dynamic light scattering (DLS)

The nanoparticles were characterized by a dynamic light scattering(DLS) using a Beckmann Coulter (DelsaTM Nano). Shining the mono-chromatic light beam of laser onto a solution with spherical particlesin Brownian motion causes a doppler shift when the light hits themoving particle, changing the wavelength of the incoming light. Theaverage values of the particle size and polydispersity, defined as arelative width of the size distribution, were determined from the DLSmeasurements.

2.8. Transmission electron microscopy (TEM)

The morphology of nanoparticles was observed under a Mor-gagni 268D (Fei Electron Optics) transmission electron microscopy(TEM) operated at 300 kV equipped with the recording systemOlympus Soft Imaging Solutions GmbH (software: iTEM; TEMCamera: Morada 4008�2672 pixel max). For TEM measurements,the samples were prepared by dropping 10–20 mL of the dehy-drated alcohol dispersion containing finely grinded lyophilizednanosilver/PMAA composite hydrogels on the grid of copper meshand dried at room temperature. The average diameter and sizedistribution were calculated from 50 pieces of silver nanoparticlesin the TEM image (Tankhiwale and Bajpai, 2010).

GammaIrradiation

nSnHin emulsion

w/o emulsionEmulsion break

byNaCl/Butanone

Separated nSnH particles

Fig. 1. Schematic representation of the preparation cycle of nSnH particles.

36

700

32500

600

28 400

One phase System

ize

(nm

)

ture

(°C

)

B. Gupta et al. / Radiation Physics and Chemistry 92 (2013) 54–6056

2.9. Antimicrobial studies

Antibacterial nature of samples was examined by the colonycount method and viable cell count method, according to the TestMethod AATCC 100–1998. The antibacterial activity was checkedagainst both gram positive bacteria Staphylococcus aureus (S.aureus) (ATCC 25923) and gram negative bacteria Escherichia coli(E. coli) (ATCC 35218) (Saxena et al., 2011).

2.9.1. Colony count methodA suspension of S. aureus (ATCC 25923) or E. coli (ATCC 35218) was

prepared from fresh colonies inMHB and the turbidity was adjusted to0.5 McFarland standards. All the samples (weight of 0.05 g) were putinto contact with 6 mL bacterial suspension in MHB having108 CFUmL�1. All the suspensions were vortexed and incubated at37 1C for 24 h. After 24 h, the suspensions were vortexed again,dilutions were prepared and colonies were counted by the spreadplate method. The inoculum (200 mL) was uniformly spread onnutrient agar plate using sterile cotton swab. The plates wereincubated at 37 1C and the colonies were counted after 24 h. Allexperiments were carried out under sterile conditions. Antibacterialefficiency was expressed according to AATCC 100 and calculated byfollowing equation:

R ð%Þ ¼ A�BA� 100

where, A indicates the number of bacteria recovered from theinoculated test specimen after 24 h incubation with control and B isthe number of bacteria according to “A” conditions with antibacterialnSnH particles. Consequently R (%) is the percentage reduction ratiowhich indicates antimicrobial efficiency.

24 300

Mic

elle

S

20

Tem

pera

100

200

0 2 4 6 800

Cloud Point not visible

AOT (%)

Fig. 2. Variation of cloud point with AOT concentration. Reaction conditions: oilphase, heptane: [AOT], 1.8�10�2 mol/L; [MAA], 1.2�10�2 mol/L; and [AgNO3],6�10�3 mmol/L.

44

40600

700

32

36500

24

28

Tem

pera

ture

(°C

)

300

400

Mic

elle

Siz

e (n

m)

20

100

200

0 2 4 6 80 0

Water Phase (%)

Fig. 3. Variation of cloud point with water phase. Reaction conditions: oilphase, heptane: [AOT], 1.8�10�2 mol/L; [MAA], 1.2�10�2 mol/L; and [AgNO3],6�10�3 mmol/L.

3. Results and discussion

Preparation of nanosilver nanohydrogels using w/o nanoemulsionhas been carried out to investigate various parameters for theformation of the nanoparticles. These hydrogel networks were pre-pared by nanoemulsion polymerization using the γ-irradiation processwhich takes into account polymerization of MAA, crosslinking ofPMAA and the reduction of silver nitrate, simultaneously. The sche-matic representation of the process is presented in Fig. 1. The influenceof the nanoemulsion composition and polymerization parameters onthe nanohydrogels has been studied in the following sections.

3.1. Phase stability of nanoemulsion

The cloud point for w/o nanoemulsion was ascertained to have apicture on the stability of the system with the variation of AOTconcentration (Fig. 2). These results show a decrease in the cloud pointwith the increase in AOT concentration from 2% to 8%. The phasestabilization of the emulsion seems to be favorable for the polymer-ization under these conditions. The cloud point variation with thewater phase is shown in Fig. 3. This shows an increase in the cloudpoint from 19–42 1C with the w/o ratio from 2% to 8% aggregates,leading eventually to the phase separation. The clouding is ascribed tothe increase in the size of polymer aggregates leading, eventually tophase separation into a polymer rich and water rich phase. Therefore,its occurrence reflects the balance between polymer–polymer andpolymer–water interactions. Less polar conformation would decreasethe polymer solvation, leading to the predominance of polymer–polymer interactions and to phase separation. The tendency of phaseseparation is very much dependent on the concentration of monomerwherein the balance in the interaction between monomer moleculesand micelles controls the behavior of solution, as more polymer wouldfacilitate the occurrence of polymer–polymer contacts. At a certain

0.25cps/eV

0.20

0.15AgAg SNa

C O

Cl

0.10

AgS

SEM image of nSnH

0.05

5 10 15 20

keV

0.00

Fig. 4. EDX-ray studies of nSnH particles. Reaction conditions: oil phase, heptane:[AOT], 1.8�10�2 mol/L; [MAA], 1.2�10�2 mol/L; and [AgNO3], 6�10�3 mmol/L;radiation dose, 15.36 kGy.

6000

5000

4000

LS3000

2000

Hydrogel

Part

icle

Siz

e (n

m)

1000TEM

50 1000

150 200 2500

20

Polymerization Time (h)

Fig. 5. Particle size determination of nSnH particles. Reaction conditions: oil phase,heptane: [AOT], 1.8�10�2 mol/L; [MAA], 1.2�10�2 mol/L; and [AgNO3], 6�10�3

mmol/L; radiation dose, 15.36 kGy.

nSnH(8 days)PMAA

nSnH(1 day)nSnH(2 days)nSnH (4days)

B. Gupta et al. / Radiation Physics and Chemistry 92 (2013) 54–60 57

temperature, water becomes a poor solvent to the polymer, possiblydue to the new and less polar polymer conformation, causing theprevalence of the polymer–polymer interaction and the growth of thepolymer aggregates leading to phase separation.

T (%

)

4000 1500

1726

3416

2927

2360

20003000 1000 400cm-1

3.2. Energy dispersive X-ray microanalysis (EDX)

Elemental analysis and quantification of silver in the nSnHsample were carried out with EDX. The EDX analysis of nSnHsamples shows a distinctive energy peak at around 0.2 keV,characteristic of carbon and oxygen. The new higher X-rayintensity was observed at around 3 keV in nSnH samples due tothe presence of silver in the PMAA matrix (Fig. 4). This is moreclearly demonstrated in the analysis of the silver contents of thesample by EDX. The nSnH sample contained 12.7% (wt) of silversuggesting that the matrix contains silver nanoparticles within thehydrogel matrix.

Fig. 6. FTIR spectra of pure PMAA and different nSnH particles. Reaction condi-tions: oil phase, heptane: [AOT], 1.8�10�2 mol/L; [MAA], 1.2�10�2 mol/L; and[AgNO3], 6�10�3 mmol/L.

3.3. Dynamic light scattering (DLS)

Fig. 5 shows the dynamic light scattering (DLS) measurementsof nanosilver nanohydrogel. The nanoparticles exhibit hydrogelnature as observed by the swelling of the matrix. In our systemnanosilver formation is taking place within the nanohydrogel bygamma radiation therefore the resulting product is nanoparticle ofmethacrylic acid having nanosilver in it. The size of nSnH in therange of 3000–5000 nm is in swollen state which shows hydrogelnature.

DLS measurements of the nanoemulsion showed the existenceof discreet particles. The diameter of the composite nanoparticleincreased with the increase in the irradiation time reaching themaximum at 100 h, beyond which the size showed a decreasingtrend. It seems that the irradiation follows a cumulative approachcomprising of three independent process i.e., polymerization ofMAA followed by reduction of the silver nitrate and then thecrosslinking of long PMAA chains. Initially, MA polymerizes andforms larger chains with increase of irradiation, till 100 h effi-ciently. Although crosslinking initiates right from the beginning ofthe irradiation, it seems that the crosslinking in reaction dom-inates beyond 100 h. This involves the interlinking of the polymerchains and reduces the expansion of the particle in contact withthe water and hence leads to the decrease in the particle size.

3.4. Fourier transforms infrared spectroscopy (FTIR)

The FTIR spectra of PMAA without silver and nSnH arepresented in Fig. 6. The characteristic features of FTIR spectrumof nSnH are almost similar to those of PMAA without silver.A broad peak corresponding to –COOH of methacrylic acid isobserved in the range 3400–3600 cm�1. Similarly, in case of nSnH,the broad band in the region of 3400–3700 cm�1 also shortenedand splitted into several peaks. This clearly indicates that Aginteracts with the active functional groups of PMAA. Peak shiftingoccurs due to co-ordination between heavy metal atom (Ag) andelectron rich group (oxygen). The peak at 2360 cm�1 shows adistinct change as the irradiation time increases, the intensityincreases suggesting C–C asymmetric stretching. This causes anincrease in bond length, ultimately leads to the shifting offrequency. The peak at 2927 cm�1 splits into doublet because itcorresponds to the –CH2 symmetric and asymmetric stretching.This causes an increase in bond length, ultimately leads to shiftingof frequency. In case of PMAA without silver, characteristic peakcorresponding to the carbonyl group of the carboxyl moiety of thePMAA unit is observed at 1726 cm�1. However, in the nSnH, thestretching vibrations of CQO gets highly reduced and shifted to

B. Gupta et al. / Radiation Physics and Chemistry 92 (2013) 54–6058

1702 cm�1. The interaction between the oxygen function of thepolymer support and the metal atoms generally results in a blue-shift of the band corresponding to the oxygen functions in the FTIRspectra (Bajpai et al., 2013).

3.5. Thermogravimetric analysis (TGA)

The thermal characterization of PMAA without silver and nSnHwas evaluated by thermogravimetric analysis. The process ofdegradation is qualitatively characterized by the onset tempera-ture, the temperature of 50% weight loss, as well as by the residueamount at 744 1C due to the loss of moisture (Fig. 7). According tothese data, the weight loss in thermogram of PMAA without silveris due to the removal of moisture from the hydrogel. The thermaldecomposition of PMAA without silver begins above 220 1C as adistinct step. In nSnH, the decomposition starts above 250 1C,probably due to the strong interaction between organic andinorganic components and moisture in the matrix. Major decom-position of PMAA takes place till 480 1C results into completedegradation at 720 1C. On the other hand the nSnH sample showsalmost stable thermogram up to 780 1C and the following degra-dation indicates that whatever is left beyond ∼450 1C is silvernanoparticle.

3.6. Transmission electron microscopy (TEM)

TEM was used for visual observation of the silver nanoparticleswith typical morphology as shown in Fig. 8, which represents the

nSnH(4 days)

100PMAA

75

50

Wei

ght (

%)

25

60 420 780600 9600

Temperature (ºC)240

Fig. 7. Thermo gravimetric analysis of pure PMAA and nSnH particles. Reactionconditions: oil phase, heptane: [AOT], 1.8�10�2 mol/L; [MAA], 1.2�10�2 mol/L;and [AgNO3], 6�10�3 mmol/L; radiation dose, 15.36 kGy.

nSnH (1 day) (Χ 50nm) nSnH (4 days)

Fig. 8. Transmission electron microscopy studies of nSnH particles. Reaction conditions6�10�3 mmol/L.

images and size distributions of the silver nanoparticles in nSnHwith radiation doses of 3.84, 7.68 and 15.36 kGy. Spherical silvernanoparticles were found to be dispersed homogeneously in allsamples with slight agglomeration. In addition, nSnH preparedwith maximum radiation dose, the particle size become larger(Chen et al., 2000). During the irradiation process, when theradiation time buildups, the particle size of nSnH increases. Highlydense nSnH networks tend to establish more inter molecularattraction between gel networks resulting in less free space inthe hydrogel networks (Mohan et al., 2007).

3.7. Antimicrobial studies

Silver, both as a metal and in ionic form, exhibits strongcytotoxicity towards a broad range of microorganisms, and itsuse as an antibacterial agent is well known. It has been reportedthat the mode of antibacterial action of silver nanoparticles issimilar to that of silver ion. However, the effective biocidalconcentration of silver nanoparticles is, at a nanomolar level, incontrast to that in a micromolar level of silver ions. Silver has anoligodynamic effect, that is, silver is capable of causing a bacterio-static (CFU) or a bactericidal (antibacterial impact). The nSnH showremarkable antimicrobial activity. The nSnH show 98% reductionin bacterial colony formation after 24 h of observation against S.aureus and E. coli suggesting that nSnH is capable of inhibiting thegrowth of microbes (Fig. 9). The sample, prepared with a highercontent of ionic monomer in the feed mixture, contains moresilver nanoparticles and hence should demonstrate greater anti-microbial activities. Zhou et al. studied the antimicrobial nature ofsilver nanohydrogel within the gelatin/carboxymethyl chitosanmatrix and formed well defined zone of inhibition against E. coli.It seems that silver ions leach out to the surrounding medium andexist in the antimicrobial matrix (Zhou et al., 2012).

4. Conclusion

Silver nanoparticles in the PMAA matrix were synthesized bynanoemulsion polymerization using γ-irradiation, where AOTserved as stabilizer in the w/o system. The particle size of thenSnH depends on the amount of monomer in the feed mixture andthe dose absorbed. By selecting appropriate combinations ofreaction parameters and silver concentration, the nSnH are around10–50 nm in diameter. Transmission electron microscopy (TEM)was used to reveal the formation and the corresponding morphol-ogy of the silver nanoparticles in the PMAA matrix. The nano-silver hydrogels were characterized using FTIR, TEM and EDX.The antimicrobial activities of these in-situ synthesized nSnH were

nSnH (8 days) (Χ 50nm)(Χ 100nm)

: oil phase, heptane:[AOT], 1.8�10�2 mol/L; [MAA], 1.2�10�2 mol/L; and [AgNO3],

Fig. 9. Antimicrobial studies of nSnH particles against E. coli (ATCC35218) and S. aureus (ATCC25923). Reaction conditions: oil phase, heptane: [AOT], 1.8�10�2 mol/L;[MAA], 1.2�10�2 mol/L; [AgNO3], 6�10�3 mmol/L; radiation dose, 15.36 kGy; and observation time, 24 h. (a) Control sample against E. coli, (b) nSnH sample against E. coli,(c) control sample against S. aureus and (d) nSnH sample against S. aureus.

B. Gupta et al. / Radiation Physics and Chemistry 92 (2013) 54–60 59

investigated against E. coli and S. aureus. Bacteriological testsshowed that either bacterial growth inhibition or cell deathoccurred, depending on the concentrations of silver nanoparticlesand of the type of bacteria that was tested on. Our results showedthe inhibition of bacterial growth against silver nanoparticlescontaining hydrogel. From the results of the above study, it maybe concluded that silver nanoparticles can be produced within theswollen polymer hydrogel network. Therefore, it should be con-sidered as potential candidate for healthcare applications.

Acknowledgment

The authors are grateful for the financial support provided byDepartment of Biotechnology (DBT), New Delhi, India to carry outthis work at IIT Delhi and AIIMS (New Delhi, India).

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