Supplementary Material (ESI) for Chemical Communications This journal is (c) The Royal Society of Chemistry 2006
Encapsulating Fluorescein Using Adipic Acid Self-assembly on the Surface of PPI-3 Dendrimer Minghui Chai,*a Aaron K. Holleyb and Michael Kruskampa a
Department of Chemistry, Central Michigan University, Mt. Pleasant, MI 48859, USA. Fax: 1 989 774 3883; Tel: 1 989 774 3955; Email:
[email protected] b Department of Chemistry, Marshall University, Huntington, WV 25701, USA Experimental General. PPI dendrimers were obtained from Aldrich Chemical Co. Adipic acid was obtained from Lancaster Synthesis Inc. Fluorescein (disodium salt) was obtained from Central Chemical Co. Deuterium oxide was purchased from Cambridge Isotope Labs. All chemicals were used as received without further purification. All solutions for UV-VIS and fluorescence studies were prepared using deionized water. The pH of each dye solution was adjusted using 0.1M NaOH or 0.1M HCl. pH measurements were made using an IQ Scientific Instruments pH/mV/temp meter (model IQ150). UV-Vis Spectroscopy. All UV-VIS spectra were obtained using a Hewlett-Packard 8452A diode-array spectrophotometer equipped with a temperature control device (distilled water blank, 28oC). 0.002 M fluorescein solution was added to a 1-cm cuvette containing 2 mL deionized H2O, followed 0.01 M PPI-3 solution, and then a stoichiometric amount of 0.05 M adipic acid (8:1 molar ratio of adipic acid to PPI-3). UV-VIS spectra were obtained after the addition of each component. A modified procedure was also used in which adipic acid was added before PPI-3 to determine the relationship between the addition of reagents and change in UV-Vis spectra of fluorescein. When adipic acid was added to a fluorescein solution, there was a significant blue-shift of the λmax to 442 nm. This blue-shift was due to reduction in the
Supplementary Material (ESI) for Chemical Communications This journal is (c) The Royal Society of Chemistry 2006
pH of the reaction mixture upon addition of the acid.1 Addition of PPI-3 caused a redshift of the peak to 498 nm (see Figure 1). This red shift to 498 nm upon addition of PPI3 suggested that the encapsulation of fluorescein and the formation of the PPI-3/adipic acid self-assembly were instantaneous. This also indicated that order of addition of reagents was not a factor in encapsulation of the dye. The effects of pH on
2
fluorescein
absorbance
1.5
alone
fluorescein/adipic
and
acid/PPI-3
system were also explored.
1
Solutions of fluorescein (pH = 0.5
4.0, 6.0, 8.0) and fluorescein in 0 400
450
500
550
wavelength (nm)
Figure 1S. UV-Vis spectra of fluorescein: alone (z), plus adipic acid (), plus adipic acid and PPI-3 (S).
the self-assembly of PPI-3 and adipic acid (pH = 2.0, 4.0, 6.0, 7.0,
8.0,
9.0,
10.0)
were
prepared. Concentrations of fluorescein were maintained at 3.72 × 10-5 M so that the solutions would be suitable for UV-Vis spectroscopy. Fluorescence Spectroscopy. All fluorescence spectra were obtained using a SPEX Fluorolog III lifetime fluorimeter. Fluorescein solution (10-5 M in deionized H2O) was added to a 1-cm fluorescence cuvette containing 2 mL deionized H2O, followed by PPI-3 solution (10-5 M; 2:1 mole ratio PPI-3-to-fluorescein), and adipic acid solution (5 × 10-5 M; 8:1 molar ratio of adipic acid-to-PPI-3) and an emission spectrum was obtained after each addition of the component in the encapsulation system (468 nm used as the excitation wavelength).
Supplementary Material (ESI) for Chemical Communications This journal is (c) The Royal Society of Chemistry 2006
For UV-Vis and fluorescence studies, control experiments using ethylenediamine instead of PPI-3 were performed for each dye to determine the effect of a classical amine on the properties of the dyes. Ethylenediamine concentration was adjusted to match the primary amine concentration of PPI-3 used in the study. NMR Spectroscopy. NMR samples of fluorescein, PPI-3, PPI-3/adipic acid, fluorescein/PPI-3 and fluorescein/PPI-3/adipic acid were prepared respectively in 0.7 mL D2O in 5 mm NMR tubes. All spectra were acquired using a Varian Inova 500 MHz NMR spectrometer with a Varian 1H/13C/X triple resonance gradient probe. All spectra were obtained at ambient temperature. 1H NMR spectra were acquired at 499.212 MHz, using 3.0 s acquisition time, 8 kHz spectral width, 3.9 μs (45º) pulse width and 16 transient for each spectrum. 1H spin-lattice relaxation (T1) measurements were also performed for fluorescein and fluorescein/adipic acid/PPI-3 systems. 2D NOESY spectrum was obtained for the fluorescein/adipic acid/PPI-3 sample and acquired at 499.209 MHz, using 0.5 s mixing time and 7.8 μs 1H 90° pulse width. The experiment was done with a 5 s relaxation delay and 0.5 s acquisition time; 16 transients were averaged for each 2 × 256 complex t1 increments. The data were processed with Gaussian weighting in both dimensions and zero filling to display data on a 4096 × 1024 2D-matrix. All data were processed with Varian VNMR software on a SUN Blade 2000 workstation.
Supplemental NMR Data
Supplementary Material (ESI) for Chemical Communications This journal is (c) The Royal Society of Chemistry 2006
Table 1S. 1H T1 Values of Fluorescein in D2O Solutions 1
Protonsa of fluorescein
a
H T1 Relaxation Time (s)
Fluorescein alone
Fluorescein encapsulated in Self-assembly
% Difference
a, a’
4.127
1.954
-53
b, b’
3.439
1.954
-43
c, c’
2.184
1.806
-17
d
1.945
1.633
-16
e
2.150
1.699
-26
f
2.150
1.699
-26
g
3.348
2.695
-20
The labels for protons are the same as those in Figure 4 of the paper.
Figure 2S. Partial expansions of 13C NMR spectra of fluorescein in D2O: (A) with PPI3 and adipic acid; (B) with PPI-3; (C) alone. The labels for carbon atoms are the same as those in Scheme 2 of the paper. 2 1 O
O 3
4 59
O
7
6
8
10
10 11 9
5
12
7
O
14
13
A
O
11 12
5
9, 11 10
7
12
B 5 9 10 11
7
12
C 134
133
132
131
130
129
128
127
1. R. Sjöback; J. Nygren; M. Kubista Spectrochimica Acta Part A 1995, 51, L7-L21.
126
ppm
