Supplementary Material

Facile Loading of Ag Nanoparticles onto Magnetic Microsphere by the Aid of a

tannic acid -metal Polymer Layer to Synthesize Magnetic Disinfectant with high

Antibacterial Activity

Tao Wanga, Binbin Maa, Awei Jina, Xiaogang Lia, Xiaole Zhanga*, Weijie Wanga*,

Yaqi Caib

aCollege of Life Sciences, North China University of Science and Technology,

Tangshan, 063000, Hebei, China

bState Key Laboratory of Environmental Chemistry and Ecotoxicology of Research

Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing

100085, China

*Corresponding author: Xiaole Zhang

College of Life Science, North China University of Science and Technology,

Tangshan, 063000, Hebei province, China

E-mail Address: smilxin@126.com. (Xiaole Zhang)

Tel: (086) 0315- 8805590; Fax: (086) 0315- 8805590.

The document contains 10 pages, including cover page, 5 Figures and 1 Table.

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Materials

Ferric chloride hexahydrate, trisodium citrate dehydrate, sodium acetate, silver nitrate,

sodium chloride, and ethylene glycol are analytical reagent-grade (≥99.0%) from

Beijing Chemical Reagents Company (Beijing, China). Ammonia water (≥25.0%),

hydrochloric acid (≥36.0%), 2-amino-2-hydroxymethyl-1,3-propanediol (Tris,

99.9%), and anhydrous ethanol (≥99.5%) were also analytical reagents purchased

from Beijing Chemical Reagents Company. Tannic acid (MW=1701.20, ≥99.5%) was

supplied by Sigma-Aldrich (St. Louis, MO). Beef extract, peptone and agar are

biochemical reagents (≥99.0%) obtained from Tianjin InBev Biochemicals Ltd

(Tianjin, China). All the reagents were used as supplied without further purification.

Ultrapure water was prepared with a Milli-Q SP reagent water system purchased from

Millipore (Milford, MA).

Growth conditions and counting of standard reference strains

We used Escherichia coli ATCC 8739 and Staphylococcus aureus ATCC 6538P

(from microbiology laboratory of college of life science, North China University of

Technology) as model bacteria. To prepare the bacterial suspension, each tested strain

was transferred into 50 mL of nutrient broth medium and incubated at 37 °C for 24 h.

The culture was collected by centrifugation, washed twice with phosphate buffered

saline (PBS, 150 mM, pH 7.2), and redispered in PBS solution to obtain a bacterial

suspension of 1 × 108 to 2 × 108 colony forming units per mL (CFU mL-1). The viable

cell number of the reference strain was determined by plate colony counting method

after incubating the gradient dilution of the suspension on the surface of nutrient agar

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at 37 °C for 24 h.

Zone of inhibition test

Paper disks (10 mm in diameter) which had been immerged into the suspension of the

magnetic disinfectant (1-16 mg mL-1) for 2 h were placed at the fixed position of

nutrient agar plate smeared on the surface with 0.2 mL of bacterial suspension (10 -5 -

10-6 CFU mL-1). The inhibition zones around the disks were measured after incubation

at 37 oC for 12 h and each experiment was repeated twice.

Determination of the MIC and MBC of the disinfectant toward tested strains

In tube double dilution method, 0.1mL of test bacteria suspension (10-5 - 10-6 CFU

mL-1) was added to serial dilutions of Fe3O4@PTA@Ag composite in Mueller–Hinton

broth, respectively. Subsequently, the mixtures were incubated under 37 oC for 12

hours and the MIC of the antibacterial material toward tested bacteria was determined

depending on the turbidity of the liquid medium after magnetic seperation. If the

disinfectant concentration was not sufficient to inhibite the growth of the test bacteria,

the test tube mixture would become turbid due to the cell culture. While displaying

clear of the test tube mixture means that the growth of test bacteria in this tube was

inhibited under such disinfectant concentration.

If the disinfectant concentration reaches a fairly high level, the test bacteria in test

tube would be not only inhibited, but also sterilized. The minimum bactericidal

concentration is defined as the concentration killing 99.9% of the original culture after

a period of incubation. To obtain the MBC of the antibacterial material, 0.1mL of the

culture was taken from each tube which exhibited clear in the above MIC experiment

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and smeared evenly onto the surface of nutrient agar plates. The MBC was judged

according to the colony counts of the tested strains formed on the plate after cultured

for 12 hours at 37 oC.

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Figure S1. VSM of Fe3O4@PTA@Ag prepared with Fe3O4@PTA-1 (red),

Fe3O4@PTA-2 (black) and Fe3O4@PTA-3 (blue) MNPs

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Figure S2. EDX spectra and

elemental composition of

Fe3O4@PTA@Ag-3 MNPs

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Element Wt% At% C K 09.57 25.04 O K 15.95 33.61 Ag L 12.75 04.02 Fe K 61.73 37.33

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Figure S3 The inhibition zone of Fe3O4@PTA@Ag-3 MNPs (16 mg mL-1) toward E.

coli (a) and S. aureus (b).

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(a) (b)

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Figure S4. TEM of the Fe3O4@PTA@Ag-3 MNPs after being continuous stirred in

water solution at 150 rpm for 12 h.

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Figure S5. The inactivation curves of Fe3O4@PTA@Ag-3 in each recycle round

toward E. coli (a) and S. aureus (b).

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(a) (b)

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Table S1.

The weight percentage of Ag in each Fe3O4@PTA@Ag composite.

Magnetic composite

Fe3O4@PTA@Ag -1

Fe3O4@PTA@Ag -2

Fe3O4@PTA@Ag -3

Fe3O4@PTA@Ag -4

AgNO3 concentration

0.05 mg mL-1 0.1 mg mL-1 0.2 mg mL-1 0.4 mg mL-1

Wt% of Ag 3.23 6.52 12.75 12.92

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