Electronic Supplementary Material
Detection of DNA hybridization using a cationic polyfluorene polymer as an enhancer of
the luminol chemiluminescence
Mei Liu,*1 Baoxin Li*2
1
Key Laboratory of Analytical Chemistry for Life Science of Shaanxi Province, College of
Food Engineering and Nutritional Science, Shaanxi Normal University, Xi'an 710062, China
2
Key Laboratory of Analytical Chemistry for Life Science of Shaanxi Province, School of
Chemistry & Chemical Engineering, Xi’an 710062, China
*corresponding author, Phone: 86-29-85310517, Fax: 86-29-85310517, E-mail:
liumei@snnu.edu.cn, E-mail: libaoxin@snnu.edu.cn
The preparation of cationic water-soluble conjugated polymer PFP+
Poly[9,9-bis(3’((N,N-dimethyl)-N-ethylammonium)propyl)-2,7-fluorene-alt-1,4-phenylene]di
bromide (PFP+) was synthesized by following a previously reported procedure with a slight
modification. The quaternization of the neutral precursor of the polymer was carried out in a
mixture of THF and DMSO (v/v = 3:1). The solution was stirred at 50 °C for 5 days. During
the reaction period, intermittent addition of a certain amount of water was needed to dissolve
any precipitation seen in the solution in order to achieve a high yield of quaternization. After
the reaction was finished, THF, water, and the extra bromoethane were evaporated in vacuum.
The remaining DMSO solution containing the target polymer was precipitated by pouring into
a large amount of diethyl ether. The precipitate was collected by centrifugation, washed with
acetone, and dried overnight at 80 °C in a vacuum oven. The synthesized water-soluble
polymer PFP+ inherits the advantages of excellent chemical stability. The structure of the
PFP+ was corroborated by 1HNMR (300MHz, DMSO-d): 7.9-7.5 (m, 10H), 3.18-3.12 (m, 8H),
2.94-2.79 (m, 16H), 2.54-2.51 (m, 4H), 1.02 (m, 10H). The molecular weight of the neutral
precursor of PFP+ was determined to be MW 17.0 kDa (PDI 1.7) by GPC using polystyrene as
standard reference and THF as eluent.
Procedures for CL detection of DNA hybridization
The whole procedure can be divided into two stages: DNA hybridization and CL detection.
First, a total volume of 200 μL containing 1.0×10−8 M probe DNA solution and appropriate
concentration target DNA solution in buffer (0.02 M phosphate, 0.2 M NaCl, pH 7.4) was
heated at 88 °C for 5 min and hybridized at 37 °C for 30 min; second, after the hybridization
solution was slowly cooled to room temperature, 100 μL PFP+ ( [PFP+] =1.0×10−8 M) solution
was added; third, a 100 μL resultant PFP+/DNA hybridization solution was pipetted into a 40
mm×14 mm quartz tube (used as CL reactor), and then 100 μL luminol–H2O2 CL solution (the
volume ratio of 5.0×10−4 M luminol to 1.0×10−3 M H2O2 was 2:1) was injected, and lastly,
CL signal was measured and recorded with the IFFL-D Chemiluminescence Analyzer.
Fig. S1 UV vis absorption spectra of luminol in the presence of polyfluorene conjugated
polymer PFP+ with different concentration. The concentrations of PFP+: (a) 0, (b) 1.0×10−9
M, (c)1.0×10−8 M, (d)1.0×10−7 M, (e) 1.0×10−6 M, [luminol]=1.0×10−4 M
Fig. S2 Absorbance of luminol at 350 nm vs function time of luminol/PFP+ in NaCl aqueous
solution with different concentration.
Fig. S3 The relative CL intensity of luminol-H2O2 respectively in the presence of
ssDNA/PFP+ and dsDNA/PFP+ with different base lengths. [PFP+] = 1.0×10−8 M, [DNA]=
1.0×10−9 M.