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Electronic Supplementary Material (ESI) for Journal of Materials Chemistry A

Polydiacetylene Liposome-Encapsulated Alginate

Hydrogel Beads for Pb2+ Detection with Enhanced

Sensitivity

Dong-En Wang, Yaolei Wang, Chang Tian, Longlong Zhang, Xiang Han, Qin Tu, Maosen Yuan, Sheng

Chen and Jinyi Wang*

Colleges of Science and Veterinary, Northwest A&F University, Yangling, Shaanxi 712100, P. R. China

* Corresponding author. Tel: +86-29-87082520; fax: +86-29-87082520

E-mail address: jywang@nwsuaf.edu.cn (J. Wang).

Electronic Supplementary Material (ESI) for Journal of Materials Chemistry A.This journal is © The Royal Society of Chemistry 2015

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SI 1. Characterization and General Methods. 1H-nuclear magnetic resonance (NMR) and 13C-NMR

spectra were recorded using a Bruker Avance DMX 500 MHz/125 MHz spectrometer. Peaks were

based on a tetramethylsilane (TMS) internal standard. Electrospray ionization mass spectroscopy (ESI-

MS) data were obtained using a Thermo Scientific LCQ FLEET mass spectrometer equipped with an

electrospray ion source and controlled by Xcalibur software (Thermo Fisher Scientific, Waltham, MA,

USA).

HO

O

7

8

O

O

7

8

N

O

O

NH

O

7

8

a)

b)

PCDA-NHS

PCDA-DA

HO

HO

Reagents and conditions: a) NHS, EDC, CH2Cl2, RT, 2h; b) Dopamine hydrochloride, DMF, TEA, RT, 24h.

PCDA

Scheme S1. The synthesis route of PCDA-DA

Synthesis of PCDA-NHS: N-hydroxysuccinimide (173 mg, 1.50 mmol) and N-(3-dimethylamino -

propyl)-N'-ethylcarbodiimide hydrochloride (300 mg, 1.56 mmol) were added to a solution of 10,12-

pentacosadiynoic acid (500 mg, 1.33 mmol) in anhydrous methylene chloride (20 mL). The solution

was stirred at room temperature for 2 h and then concentrated under vacuum. The residue was extracted

using ethyl acetate (20 mL) and washed with water. The organic layer was dried over MgSO4 and

concentrated in vacuo to obtain PCDA-NHS as a white solid (580 mg, 92.4%). 1H NMR (500 MHz,

CDCl3) δ (ppm): 0.88–0.91 (t, J = 6.7 Hz, 3H), 1.27–1.55 (m, 30H), 1.72–1.79 (m, 2H), 2.24–2.28 (t, J

= 6.9 Hz, 4H), 2.60–2.64 (t, J = 7.5 Hz, 2H), 2.85–2.86 (d, J = 4.1 Hz, 4H). 13C NMR (125 MHz, CDCl3)

δ (ppm): 14.16, 19.20, 19.22, 22.72, 24.55, 25.61, 28.28, 28.36, 28.72, 28.81, 28.88, 28.92, 29.12, 29.37,

29.50, 29.63, 29.65, 29.67, 30.93, 31.94, 65.19, 65.28, 77.46, 77.64, 168.69, 169.23. ESI MS m/z =

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472.4 [M + H]+, calc. for C23H46NO4+ = 472.3.

Synthesis of PCDA-DA: To a mixture of PCDA-NHS (230 mg, 0.49 mmol) and dopamine

hydrochloride (130 mg, 0.68 mmol) in DMF (5 mL) was slowly added triethylamine (69 mg, 0.68

mmol). The resultant solution was stirred at room temperature overnight. The reaction solution was then

diluted with ethyl acetate (30 mL) and wash with brine. The organic layer was dried over Na2SO4 and

concentrated in vacuo. The crude product was purified by column chromatography (silica, methylene

chloride: methanol, 19:1, followed by 9:1, v/v). The desired PCDA-DA was obtained as a white solid

(230 mg, 90%). 1H NMR (500 MHz, CDCl3) δ (ppm): 0.87–0.89 (t, J = 6.1 Hz, 3H), 1.26–1.51 (m,

36H), 1.54–1.57 (m, 2H), 2.14–2.17 (t, J = 7.3 Hz, 2H), 2.23–2.25 (t, J = 6.9 Hz, 4H), 2.68–2.71 (t, J =

6.6 Hz, 2H), 3.48–3.49 (d, J = 6.0 Hz, 2H), 5.70 (s, 1H), 6.55–6.57 (d, J = 7.8 Hz, 1H), 6.75 (s, 1H),

6.80–6.82 (d, J = 7.9 Hz, 1H). 13C NMR (125 MHz, CDCl3) δ (ppm):14.15, 19.20, 19.24, 22.72, 25.71,

28.30, 28.40, 28.77, 28.87, 28.90, 29.11, 29.13, 29.37, 29.51, 29.64, 29.66, 29.68, 31.95, 34.95, 36.82,

41.04, 65.28, 65.34, 76.79, 77.04, 77.30, 77.53, 77.69, 115.12, 115.43, 120.41, 130.47, 143.22, 144.38,

174.48. ESI MS m/z = 510.2 [M + H]+, calc. for C33H52NO3+ = 510.4.

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SI 2. NMR Spectra of PCDA-DA.

Figure S1. 1H-NMR spectrum of PCDA-DA in CDCl3.

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Figure S2. 13C-NMR spectrum of PCDA-DA in CDCl3.

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SI 3. Optimization of PDA Liposome Components.

Figure S3. (A) CR (%) values of PDA liposomes prepared from different mole ratios of PCDA and

PCDA-DA (10:0, 1:9, 2:8, 3:7, 4:6, 5:5, 0:10) in the presence of Pb2+ (100 µM). (B) Corresponding

color changes of the above mentioned liposomes before and after adding Pb2+ (100 µM).

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SI 4. Study on the Size Distribution of PDA-DA Liposomes by DLS.

Figure S4. DLS particle size distribution of PDA-DA liposomes in HEPES (10 mM, pH 7.4) (A) before

and (B) after UV irradiation (254 nm).

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Figure S5. DLS particle size distribution of PDA-DA liposomes in HEPES (10 mM, pH 7.4) in the

presence of (A) 0 μM, (B) 50 μM, and (C) 100 μM of Pb2+.

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SI 5. In situ 1H-NMR Spectroscopy Studies of PCDA and PCDA-DA in the Presence of Pb2+.

Figure S6. The partial 1H-NMR spectra (DMSO-d6, 500 MHz) of the mixture containing PCDA and

PCDA-DA after the addition of Pb2+ as a function of time.

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SI 6. Study on the Response Time of PDA-DA Liposomes for Pb2+.

Figure S7. (A) UV-vis absorbance spectra of PDA-DA liposomes (100 μM) upon the addition of Pb2+

(40 μM) as a function of time. (B) Corresponding CR (%) value changes of PDA-DA liposomes upon

the addition of Pb2+ with the time increasing.

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SI 7. Study on the Selectivity of PDA Liposomes Prepared from Pure PCDA.

Figure S8. (A) UV-vis spectra and (B) related CR (%) values of PDA liposomes prepared from pure

PCDA in HEPES (10 mM, pH 7.4) in the presence of different metal ions (100 μM) in HEPES buffer

(10 mM, pH 7.4) at room temperature. (C) Corresponding color changes of PDA liposomes prepared

from pure PCDA after adding different metal ions. Control group was set as the CR (%) value and color

change of PDA-DA lipsomes in the presence of Pb2+ (100 μM).

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SI 8. Study on the Morphology of PDA-DA Liposome-Encapsulated Hydrogel Microbeads by FE-

SEM.

Figure S9. (A) FE-SEM image of the as-prepared PDA-DA liposome-encapsulated hydrogel

microbeads, inset shows the enlarged view of a single hydrogel microbead. (B) The internal morphology

of the hydrogel microbead characterized by FE-SEM.

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SI 9. The Colorimetric Responses of PDA-DA Liposome-Encapsulated Hydrogel Microbeads for

Pb2+.

Quantification of the color transitions of the PDA-DA liposome-encapsulated hydrogel microbeads

was based on a published RGB analysis (K. P. Kootery, et al. Acs Appl. Mater. Interfaces, 2014, 6,

8613). In brief, hydrogel microbeads containing PDA-DA liposome incubated with different

concentrations of Pb2+ were observed by an inverted microscope. Images were captured to produce 24

bit color depth red-green-blue (RGB) images (1600 × 1200). The RGB values of each image within the

hydrogel beads were then extracted by using Software Image-Pro Plus 6.0. The relative intensity of the

red color component defined as the red chromaticity level (r) could be calculated as:

r = R / (R + G + B)

where R, G, B are the intensities of the three primary color components (red, green and blue).

Figure S10. (A) Optical images of the PDA-DA liposome-encapsulated hydrogel microbeads upon the

addition of different concentrations of Pb2+. (B) Plot of the red chromaticity level as a function of Pb2+

concentration.