Electronic supplementary material

Engineering Polyethersulfone Hollow Fiber Membrane with Improved Blood Compatibility and Antibacterial Property

Zhen-Qiang Shia, Hai-Feng Jia, Hai-Chao Yua, Xue-Lian Huanga, Wei-Feng Zhaoa,b, Shu-

Dong Suna*, Chang-Sheng Zhaoa**

a College of Polymer Science and Engineering, State Key Laboratory of Polymer

Materials Engineering, Sichuan University, Chengdu 610065, China b Fiber and Polymer Technology, School of Chemical Science and Engineering,

Royal Institute of Technology (KTH), Teknikringen 56-58 SE-100 44, Stockholm,

Sweden.

*Corresponding author.

E-mail: [email protected] (*), [email protected] (**)

Tel.: +86-28-85400453; Fax: +86-28-85405402. Experiments

Thermogravimetric analysis (TGA) for the membrane

The thermogravimetric analysis (TGA) curves of the particles were obtained by using a Q500 thermogravimetric analyzer (TA Instruments, USA) under a dry nitrogen atmosphere from 50 to 700 °C at the heating speed of 10 °C/min.

Water contact angle for the hollow fiber membrane

Water contact angle for the hollow fiber membrane was determined by a Micro– wilhelmy technique on the JK99B (Powereach, China) surface tension tester using distilled water as probe liquid[1].

Pore size and distribution for the hollow fiber membrane

Pore size and distribution for the hollow fiber membrane were evaluated using an autoporosity analyzer (Micromeritics TriStar 3000, USA) for the Brunauer-Emmett-

Teller (BET)-N2 adsorption/desorption experiments[2] (the sample was outgassed at 150 °C for 6 h). The pore size distribution was determined from the adsorption branch using the Barrett-Joyner-Halenda (BJH) method.

Porosity of the hollow fiber membrane

Porosity of the hollow fiber membrane was calculated from the density of the polymer and the weight change before and after drying, using the formula[3]:

(1) where WB (g) is the weight of the sample before drying; WA (g) is the weight of the

-3 -3 sample after drying; ρW = 1.0 g/cm the density of water; ρP = 1.43 g/cm is the density of polymer matrix.

Mechanical strength for the hollow fiber membrane

Mechanical strength for the hollow fiber membrane was conducted on a YG001A- 1Model tensile tester, with a crosshead velocity of 20 mm/min and a gauge length of 20 mm. The test was carried out at a constant temperature of 25 ◦C and a relative humidity of 70 %[4]. Twenty single-fiber specimens were measured to obtain the average.

In vitro Ag+ release experiment

To evaluate the release of the Ag nanoparticle and Ag+ from the membranes, Ag- loaded hollow fiber membranes with the effective area of 3 cm2 (about 21 cm in length, dissected and cut into pieces) were immersed in 10 ml phosphate buffered saline (PBS) at 37 ◦C. The PBS was completely replaced with fresh PBS periodically at each sampling time (every 12 h) for 8 times. The amount of thereleased Ag was analyzed every 12 h by flame atomic absorption spectrophotometry (FAAS) (Model AA220Fs, VARIAN, USA). Generally, Ag+ content in the solution could be tested by FAAS, but nonionic Ag nanoparticle could not be tested by FAAS. To test the content of the nonionic Ag nanoparticle, nitric acid (HNO3) was applied to ionize the Ag nanoparticle before testing; and then the amount of the released Ag nanoparticle from the membrane could be evaluated by the difference of the Ag+ content before and after treating with

HNO3[5].

3. Results and discussion

Thermogravimetric analysis (TGA) for the membranes

Fig. S1 TGA curves for HFM-PES, HFM-4-1, HFM-12-3 and HFM-24-6

Basic characterizations of the prepared membranes

a) The water contact angles for all of the membranes were less than 90◦. The pure PES membrane possessed the highest water contact angle of 82.5◦, the water contact angle for the membrane decreased about 30◦ when the poly(MMA-VP-SSNa-SA) was blended into the membrane, indicating that the hydrophilicity of the modified membranes was improved after blending with poly(MMA-VP-SSNa-SA). Besides, compared with HFM-24-6, the water contact angles for HFM-24-6-a, HFM-24-6-b and HFM-24-6-c, onto which Ag nanoparticle were immobilized, increased about 6◦, but still much lower than the pure PES membrane; b) The pore size obtained from the

BET-N2 adsorption/desorption experiments showed the average size of the pores in the dense skin layer, the porous sub-layer and the finger-like structure, and the average pore radiuses for all of the membranes were about 65 nm. Besides, no significant difference was seen in the pore size and distribution for the hollow fiber membranes; c) Compared with HFM-PES, the porosity of the modified membranes increased more than 10%; d) Tensile strength for the membranes decreased slightly after blending with poly(MMA-VP-SSNa-SA), but was still within the acceptable range. Table S1 Basic property of the hollow fiber membranes Sample HFM-PES HFM-4-1 HFM-12-3 HFM-24-6 Water contact angle (◦) 82.5 53.1 50.9 48.9 Average pore radius (nm) 67.2 63.2 65.7 68.3 Porosity (%) 71.2 83.1 82.3 84.2 Tensile strength (MPa) 1.4 1.2 0.9 1.0 Compared with HFM-24-6, the water contact angles for HFM-24-6-a, HFM-24-6-b and HFM-24-6-c increased about 6◦.

Fig. S2 Pore size distribution of the hollow fiber membranes

In vitro Ag+ release experiment

The results of the in vitro Ag+ release experiment indicated the sustained and stable Ag+ release property for the Ag-loaded hollow fiber membranes. As shown in Fig. 3a, all of the Ag-loaded membranes showed a stable Ag+ releasing quantity, even after changing the buffer solution for several times, since the Ag nanoparticle served as a depot to release Ag+ continuously[6]. The average quantities of the Ag+ released from HFM-24-6-a, HFM-24-6-b and HFM-24-6-c for each circle were about 0.49 μg/cm2, 0.32 μg/cm2 and 0.20 μg/cm2, respectively.

+ Fig. 3b shows the Ag content before and after treating with HNO3, and the released amounts of the Ag nanoparticle from the membranes were calculated. The total amounts of the released Ag nanoparticle from the HFM-24-6-a, HFM-24-6-b and HFM-24-6-c after changing the PBS for 8 times were 0.04 μg/cm2, 0.13 μg/cm2 and 0.24 μg/cm2, respectively, indicating the stability of the loaded Ag nanoparticle on the hollow fiber membranes. Fig. S3 (a) in vitro Ag+ releasing properties of the Ag-loaded membranes in PBS; (b) Release quantity changes of Ag+ in PBS for 96 h test before and after treating with

HNO3.

3.2. SEM of the hollow fiber membrane

Fig. S4 SEM images of inside surface of the hollow fiber membranes; magnification,

(a) 10 000 and (b) 50 000 References

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