Prop-2-ynyloxybenzyloxy substituted phthalocyanine-based polymeric nanoparticles: synthesis, photophysical properties and in?vitro PDT efficacy

Article abstract of DOI:10.1080/00958972.2020.1766683

Two prop-2-ynyloxybenzyloxy axially/peripherally substituted zinc/silicon phthalocyanines (YSiPc and YZnPc) were synthesized. They were encapsulated into an amphiphilic block copolymeric micelle polyethylene glycol monomethyl ether-polycaprolactone (MPEG₅₀₀₀–PCL₂₀₀₀) to form polymeric nanoparticles YSiPc@MPEG₅₀₀₀–PCL₂₀₀₀ and YZnPc@MPEG₅₀₀₀–PCL₂₀₀₀. The photophysical and photochemical properties of these polymeric nanoparticles were studied by UV/Vis and fluorescence spectroscopy. The cellular uptake and reactive oxygen species (ROS) production abilities of two polymeric nanoparticles in MCF-7 breast cancer cells were evaluated by confocal laser scanning imaging. YSiPc@MPEG₅₀₀₀–PCL₂₀₀₀ exhibited a higher cellular uptake, higher ROS generation ability as well as higher photodynamic efficacy against MCF-7 cells. YSiPc@MPEG₅₀₀₀–PCL₂₀₀₀ is a promising photosensitizer for photodynamic therapy.

Full text of DOI:10.1080/00958972.2020.1766683

Journal of Coordination Chemistry
ISSN: 0095-8972 (Print) 1029-0389 (Online) Journal homepage: https://www.tandfonline.com/loi/gcoo20
Prop-2-ynyloxybenzyloxy substituted
phthalocyanine-based polymeric nanoparticles:
synthesis, photophysical properties and in vitro
PDT efficacy
Shuanghuang Xiao, Xiuqin Chen, Qiuhao Ye, Kuizhi Chen, Wenling Xiao,
Xinqiao Guan, Bingcheng Huang, Guowei Liu, Hui Wei & Yiru Peng
To cite this article: Shuanghuang Xiao, Xiuqin Chen, Qiuhao Ye, Kuizhi Chen, Wenling
Xiao, Xinqiao Guan, Bingcheng Huang, Guowei Liu, Hui Wei & Yiru Peng (2020): Prop-2-
ynyloxybenzyloxy substituted phthalocyanine-based polymeric nanoparticles: synthesis,
photophysical properties and in vitro PDT efficacy, Journal of Coordination Chemistry, DOI:
10.1080/00958972.2020.1766683
To link to this article: https://doi.org/10.1080/00958972.2020.1766683
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JOURNAL OF COORDINATION CHEMISTRY
https://doi.org/10.1080/00958972.2020.1766683
Prop-2-ynyloxybenzyloxy substituted phthalocyanine-
based polymeric nanoparticles: synthesis, photophysical
properties and in vitro PDT efficacy
a
a
a
a
a
Shuanghuang Xiao , Xiuqin Chen , Qiuhao Ye , Kuizhi Chen , Wenling Xiao ,
a
a
a
b
a
Xinqiao Guan , Bingcheng Huang , Guowei Liu , Hui Wei and Yiru Peng
a
College of Chemistry & Material, Fujian Provincial Key Laboratory of Advanced Materials Oriented
Chemical Engineering, Fujian Province Key Laboratory of Polymer Materials, Fujian Normal University,
b
Fuzhou, China; Institute of Plant Protection, Academy of Agricultural Sciences, Fuzhou, China
ABSTRACT
ARTICLE HISTORY
Two prop-2-ynyloxybenzyloxy axially/peripherally substituted zinc/
silicon phthalocyanines (YSiPc and YZnPc) were synthesized. They
were encapsulated into an amphiphilic block copolymeric
micelle polyethylene glycol monomethyl ether-polycaprolactone
Received 20 February 2020
Accepted 14 April 2020
KEYWORDS
(
MPEG5000–PCL2000
)
to form polymeric nanoparticles YSiPc@
Phthalocyanine; alkynyl;
polymeric nanoparticle;
photodynamic therapy
MPEG5000–PCL2000 and YZnPc@MPEG5000–PCL2000. The photophysi-
cal and photochemical properties of these polymeric nanoparticles
were studied by UV/Vis and fluorescence spectroscopy. The cellular
uptake and reactive oxygen species (ROS) production abilities of two
polymeric nanoparticles in MCF-7 breast cancer cells were evaluated by
confocal laser scanning imaging. YSiPc@MPEG5000–PCL2000 exhibited a
higher cellular uptake, higher ROS generation ability as well as higher
photodynamic efficacy against MCF-7 cells. YSiPc@ MPEG5000–PCL2000 is
a promising photosensitizer for photodynamic therapy.
CONTACT Hui Wei
weihui@Faas.cn; Yiru Peng
Yirupeng@Fjnu.edu.cn
Shuanghuang Xiao and Xiuqin Chen contributed equally to the paper.
ß 2020 Informa UK Limited, trading as Taylor & Francis Group

2
S. XIAO ET AL.
1. Introduction
Phthalocyanine derivatives (Pcs) have been widely applied in technological and medical
fields such as electrochromic displays [1], optical-limiting devices [2], solar cells [3], liquid
crystals [4], chemical transducers [5], catalysts [6], and photosensitizers for photodynamic
therapy (PDT) of cancer and non-cancer diseases [7, 8]. Pcs are promising photosensitizers
because of their strong absorption in near-red light region and high singlet oxygen gener-
ation ability [9, 10]. However, a limitation for Pcs is their limited-solubility in common
organic solvents or in water, which leads to low PDT efficacy. The introduction of functional
groups on the peripheral or axial position of phthalocyanines could improve their solubility
and modulate their physical and chemical properties. In the past few years, Pcs substituted
with various functional groups such as carboxylic, hydroxy, amine, azide, or alkynyl groups
have been synthesized and characterized [11]. Alkynyl substituted phthalocyanines have
attracted more attention because of their potential utilizations in click chemistry [12, 13].
Another limitation for phthalocyanines is their limited tumor targeting ability. In order to
improve their selectivity to tumors, some nanocarriers were used to encapsulate phthalo-
cyanines to form nanoparticles. These nanocarriers included dendrimers, liposomes, poly-
meric micelles, etc. Nanoparticles could deliver Pcs to tumors through enhanced
permeation and retention effect. [14–17]. Polyethylene glycol monomethyl ether-polycap-
rolactone (PEG–PCL) copolymer micelle is an amphipathic polymer because its hydrophilic
PEG segment exhibited resistance reticuloendothelial system uptake ability [18, 19] and its
biocompatible and biodegradable PCL segment could form hydrophobic core to encapsu-
late therapeutic agents [20]. Master et al. encapsulated silicon phthalocyanine 4 (Pc 4) by
PEG–PCL to form Pc 4 nanoparticle-loaded micelles. After irradiation, Pc 4 nanoparticle
showed a significantly enhanced photocytotoxicity to MCF-7 cells [21]. Guo et al. reported
that the photosensitizer hypocrellin A encapsulated by a lipase-sensitive methoxy poly
(ethylene glycol)-block-poly(e-caprolactone)micelle showed higher in vitro and in vivo anti-
bacterial PDT activity than the hypocrellin A alone [22]. In our work, two prop-2-ynyloxy-
benzyloxy substituted zinc/silicon phthalocyanines, di-[3,5-bis(prop-2-ynyloxy)benzyloxy]
silicon(IV) phthalocyanine (YSiPc) and tetra-[3,5-bis(prop-2-ynyloxy)benzyloxy] zinc(II)
phthalocyanine (YZnPc), have been synthesized. Their structures were characterized by
1
elemental analysis, H NMR, IR, and ESI-MS methods. Amphiphilic block copolymeric
micelle polyethylene glycol monomethyl ether-polycaprolactone (MPEG5000–PCL2000) was
used as a nanocarrier to encapsulate YSiPc or YZnPc to form polymeric nanoparticles,
YSiPc@MPEG5000–PCL2000 or YZnPc@MPEG5000–PCL2000, respectively. The photophysical
properties of YSiPc, YZnPc, and polymeric nanoparticles YSiPc@MPEG5000–PCL2000 and
YZnPc@MPEG5000–PCL2000 were studied and compared by UV/Vis and fluorescence spec-
troscopy. The cellular uptake ability and reactive oxygen species (ROS) produce photo-
dynamic efficacies of the two polymeric nanoparticles against MCF-7 breast cancer cells.
2. Experimental
2.1. Materials and equipment
All reagents and solvents were of reagent grade and obtained from commercial suppli-
ers. Dichloro-phthalocyanine silicon (SiPcCl ) and unsubstituted zinc(II) phthalocyanine
2

JOURNAL OF COORDINATION CHEMISTRY
3
(n-ZnPc) were synthesized according to the literature procedure [23]. Amphiphilic block
copolymer MPEG5000–PCL2000 was obtained from Jinan Daigang Biomaterial Co. (Jinan,
China). Dialysis bag with a molecular weight cut-off (MWCO) of 7000 was purchased
from Beijing Jingke Hongda Biotechnology Co. (Beijing, China). Cell counting kit-8 (CCK-
0 0
8
) was purchased from Beijing TransGen Biotech Co. LTD. [5-(and-6)-chloromethyl-2 ,7 -
dichlorodihydro fluorescein diacetate acetyl ester] (CM-H DCFDA) was purchased from
2
Thermo Fisher Scientific (Shanghai, China). Dulbecco’s Minimum Essential Media
(DMEM)/high glucose and hyclone FBS were purchased from Gibco, USA. MCF-7 breast
cancer cells were purchased from Shanghai Kefeng Biological Technology Co.
(Shanghai, China).
IR spectra were recorded on a Perkin Elmer PE-983G FT-IR spectrophotometer using
1
KBr pellets. H NMR spectra were recorded on a Varian 400 MHz spectrometer using
TMS as an internal standard. Mass spectra were performed on a LCQ Deca XP Max
mass spectrometer. The elemental analyses were performed on an Elementar Vario EL
III elemental analyzer. UV/Vis spectra were recorded on a Varian Cary 50 spectropho-
tometer. Fluorescence spectra were recorded on a Zolix fluorescence spectrophotom-
eter. Dynamic light scattering (DLS) of polymeric nanoparticles were measured using a
Nano-ZS Zetasizer (Malvern Instruments Ltd., UK). Fluorescence microscopy images
were observed on a confocal laser scanning imaging (CLSM, Leica TCS SP8 Ltd.).
2.2. Synthesis
2.2.1. Synthesis of 3,5-bis(prop-2-ynyloxy)benzyl alcohol (Y1)
3
,5-Dihydroxybenzyl alcohol (2.1 g, 14.3 mmol), K CO (6.06 g, 42.8 mmol), and prop-
2 3
argyl bromide (2.80 mL, 35.7 mmol) were dissolved in acetone (50 mL). The reaction
ꢀ
mixture was stirred at 60 C for 48 h under nitrogen. After the insoluble solid was fil-
tered off, the solvent was removed by evaporation. The crude product was purified by
silica column chromatography using dichloromethane (CH Cl ):ethyl acetate (EtOAc)
2
2
1
(
(
4
v/v)¼19:1 as eluent two times to give Y1 (2.5 g, 80.6%) as a white solid. H NMR
400 MHz, CDCl ): d/ppm, 6.63 (d, 2H, J ¼ 2.3 Hz, Ar-H), 6.54 (t, 1H, J ¼ 6.3 Hz, Ar-H),
3
.68 (d, J ¼ 2.4 Hz, 4H, CHꢁCCH O-Ar), 4.65 (d, 2H, J ¼ 5.6 Hz, Ar-CH OH), 2.52 (t, 2H,
2
2
ꢂ1
J ¼ 2.4 Hz, CHꢁCCH O-Ar). IR (KBr, cm ): 1060–1160 (Ar-C-O), 2122(CꢁC), 2925 ꢃ 2866
2
þ
(
–CH ), 3400 (OH). ESI-MS: m/z value at 234.7 [M þ H O] (216.2). Anal. Calcd. for
2
2
C H O : C, 72.21; H, 5.59. Found: C, 72.19; H, 5.56%.
1
3 12 3
2.2.2. Synthesis of di-[3,5-bis(prop-2-ynyloxy)benzyloxy] silicon(IV) phthalocyan-
ine (YSiPc)
A mixture of Y1 (0.194 g, 0.90 mmol), SiPcCl (0.21 g, 0.33 mmol) and pyridine (1.5 mL)
2
ꢀ
was refluxed in dried toluene (50 mL) at 110 C for 48 h. The reaction mixture was
then cooled to room temperature, and the solvent was evaporated under reduced
pressure. The crude product was purified two times by silica column chromatography
using CH Cl :EtOAc(v/v)¼19:1 as eluent to give YSiPc (82 mg, 25.6%) as a blue solid.
2
2
1
H NMR (400 MHz, CDCl ): d/ppm ¼ 9.67 (m, 8H; Pc-aH), 8.36 (m, 8H, Pc-bH), ꢂ0.71 (t,
3
2
H, CHꢁCCH O-Ar), 3.76 (d, 8H, J ¼ 2.4 Hz, CHꢁCCH O-Ar), 5.67 (d, J ¼ 2.3 Hz, 2H, Ar-
2
2
ꢂ1
H), 3.49 (d, J ¼ 2.4 Hz, 4H, Ar-H), 2.27 (t, J ¼ 2.3 Hz, 4H, Ar-CH OH). IR (KBr, cm ):
2

4
S. XIAO ET AL.
1
296–1162 (Ar-C-O), 2122(CꢁC), 2952 ꢃ 2853 (–CH ), 1083 (Si-O), 1600(C ¼ N/C ¼ C).
2
þ
ESI-MS: m/z value at 970.6 [M] (971.0). Anal. Calcd. for C H N O Si: C, 71.74; H, 3.94;
58 38 8 6
N, 11.54. Found: C, 71.70; H, 3.91; N, 11.51%.
2.2.3. Synthesis of 4-(3,5-bis(prop-2-ynyloxy)benzyloxy)phthalonitrile (Y2)
A mixture of Y1 (0.65 g, 3.0 mmol), 4-nitrophthalonitrile (0.52 g, 3.02 mmol) and K CO3
2
(0.42 g, 3.02 mmol) in DMSO (15 mL) was stirred at room temperature under nitrogen
for 3 days. The reaction mixture was poured into ice-water. The precipitate was filtered
and dried. The filtered solid was re-dissolved in CH Cl and washed with water three
2
2
times. The organic layer was dried over MgSO and the solvent was evaporated under
4
reduced pressure. The residue was purified by column chromatography on silica gel
1
eluting with CH Cl to afford Y2 (0.36 g, 35.6%) as a white solid. H NMR (400 MHz,
2
2
CDCl ): d, ppm, 5.14 (s, 2H, Ar-CH ), 6.66 (d, J ¼ 2.2 Hz, 2H, Ar-H), 4.71 (d, J ¼ 2.4 Hz, 4H,
3
2
CHꢁCCH O-Ar), 6.64 (d, J ¼ 2.2 Hz, 1H, Ar-H), 2.56 (s, 2H, CHꢁCCH O-Ar), 7.33 (d,
2
2
ꢂ1
J ¼ 2.6 Hz, 1H, Ar-H), 7.26 (m, 1H, Ar-H), 7.72 (d, J ¼ 8.8 Hz, 1H, Ar-H). IR (KBr, cm ):
1
033 ꢃ 1288 (Ar-C-O), 2122(CꢁC), 2952 ꢃ 2853 (–CH ), 2230 (CN), 1600(C ¼ C). ESI-MS:
2
þ
m/z value at 361[M þ H O] (342.3). Anal. Calcd. for C H N O : C, 73.68; H, 4.12; N,
2
21 14 2 3
8
.18. Found: C, 73.59; H, 4.09; N, 8.13%.
2.2.4. Synthesis of tetra-[3,5-bis(prop-2-nyloxy)benzyloxy]zinc(II)phthalocyanine
(
YZnPc)
A mixture of Y2 (0.19 g, 0.55 mmol), Zn(CH COO) (0.025 g, 0.14 mmol) and DBU (35 mL)
3
2
ꢀ
in n-pentanol (3 mL) was heated to 140 C with stirring for 24 h under nitrogen. The
dark blue mixture was cooled to room temperature and then precipitated in methanol.
The precipitate was filtered off and washed with methanol. The crude product was
purified by silica gel column chromatography using CH Cl /acetone (v/v)¼1:1/5:1 as
2
2
ꢂ1
eluent to afford YZnPc (30 mg, 15.6%) as a blue solid. IR (KBr, cm ): 2122(CꢁC),
þ
2
961 ꢃ 2828 (–CH ), 1607 (C ¼ C), 3442 (N-H). ESI-MS: m/z value at 1435.5[M] (1435.5).
2
Anal. Calcd. for C H N O Zn: C, 70.32; H, 3.93; N, 7.81. Found: C, 70.22; H, 3.93;
8
4 56 8 12
N, 7.77%.
2.2.5. Synthesis of polymeric nanoparticles
The polymeric nanoparticles YSiPc@MPEG5000–PCL2000 and YZnPc@MPEG5000–PCL2000
were prepared by a solvent-dialysis method. Briefly, a solution of YSiPc or YZnPc
ꢂ4
(
1 mL, 1 ꢄ 10 M) in N,N-dimethyl formamide (DMF) solution was mixed with 5 mg
MPEG
–PCL
under ultrasonic radiation and then 9 mL of deionized water was
2000
5
000
added dropwise into this solution under vigorous stirring at room temperature for
0
2
.5 h. The mixture was then dialyzed against distilled water at room temperature for
4 h using a dialysis membrane with a molecular weight cut-off of 7000. The dialysis
solution was collected. The polymeric nanoparticles were obtained by filtering through
a 0.2 lm syringe-driven filter.

JOURNAL OF COORDINATION CHEMISTRY
5
2.3. Photophysical and physicochemical properties
2.3.1. Photophysical parameters
Fluorescence quantum yields of YSiPc, YZnPc and their polymeric nanoparticles were
determined according to Eq. (1):
ꢀ
ꢀ
FX
AZnPc
AX ¼ AZnPcꢄ FZnPc ꢄ
,
(1)
AX
where UZnPc is the fluorescence quantum yield of n-ZnPc in DMF (A
¼ 0.28) and
n-ZnPc
FX and FZnPc are the integrals of fluorescence emission intensity of YSiPc, YZnPc, and
n-ZnPc, respectively. A and A
are the absorbance of YSiPc, YZnPc, and n-ZnPc at
ZnPc
X
the specific excitation wavelength, respectively.
The fluorescence decay curves of YSiPc, YZnPc, and their nanoparticles were fitted
using an iterative nonlinear least squares method and analyzed by a reconvolution of
the instrumental response function.
2.3.2. Singlet oxygen quantum yield
Singlet oxygen quantum yield (A ) determinations were carried out using the chemical
D
trapping method [24]. Typically, 3 mL portion of the sample solutions (concentration ¼
1
ꢄ 105 mol/L) containing 1,3-diphenylisobenzofuran (DPBF) was irradiated at 670 nm in air
oxygen saturated DMF. Singlet oxygen quantum yields (U ) were determined by the rela-
D
tive method using n-ZnPc (in DMF) as a reference. DPBF was used as a chemical quencher
for singlet oxygen. Singlet oxygen quantum yield was calculated according to Eq. (2):
ref
k ꢅ I
ref
a
A ¼ AFD
ꢅ
,
(2)
D
ref
k Ia
where A is the singlet oxygen quantum yield for the standard (0.57 for n-ZnPc in DMF)
D
ref
[
25], k and k are the DPBF photo-bleaching rate constants in the presence of the sam-
ref
ples and standard, respectively. I and Ia are the rates of light absorption by the samples
a
and standard sample, respectively. Their ratios can be obtained according to Eq. (3).
ref
ref
1ꢂ10ꢂA6
70
I
a
¼
:
(3)
ꢂA670
Ia
1 ꢂ 10
The degradation of DPBF at 417 nm was monitored. The light intensity for determi-
2
nations of U was 6.60 ꢄ 1015 photons s/cm .
D
2.4. Cell uptake and subcellular location
MCF-7 breast cancer cells were cultured in a culture medium (DMEM) containing 10%
ꢀ
FBS and 1% penicillin streptomycin at 37 C in 5% CO . Cells were seeded into 35 mm
2
glass-bottom dishes and allowed to grow until a confluence of 80%. Prior to experi-
ment, the medium was removed and the adherent cells were washed twice with PBS
to remove the remnant growth medium. MCF-7 breast cancer cells were incubated
with 100 lL YSiPc@MPEG5 –PCL2000 and YZnPc@MPEG5000–PCL2000, respectively
000
ꢀ
(
1 lM YSiPc or YZnPc), at 37 C for 12 h. After washing with DMEM three times, cells
were used for bioimaging subsequently. YSiPc or YZnPc was excited at 860 nm by
two-photon laser and signal collection from 640 to 700 nm.

6
S. XIAO ET AL.
2.5. Intracellular ROS detection
Intracellular ROS generation of YSiPc@MPEG5000–PCL2000 and YZnPc@MPEG5000
–
PCL were measured using CM-H DCFDA as the probe. 5-(and-6)-Chloromethyl-
2
000
2
0
0
,7 dichlorodihydro-fluorescein (CM-H DCF) did not exhibit fluorescence in solution,
2
2
0
0
while it was oxidized to form 2 ,7 -dichlorofluorescin (CM-DCF), which exhibited bright
fluorescence. The intracellular ROS production can be evaluated by recording the
change of intracellular fluorescence intensity. MCF-7 breast cancer cells were seeded
on 35 mm confocal dishes with a density of 1 ꢄ 105 cells per well. After incubation
with 0.5 lM YSiPc@MPEG5 –PCL
and YZnPc@MPEG
–PCL
for 12 h, the cells
2000
000
2000
5000
2
were irradiated by 670 nm laser (32 mW/cm ) for 5 min. A control experiment was con-
ducted without irradiation. The medium was removed, the cells were rinsed with PBS
and incubated with CM-H DCFDA (5 lM) in 0.5 mL fresh medium for 20 min. Finally,
2
the medium was removed and cells were rinsed with PBS (pH 7.4). The fluorescence of
DCFDA was visualized by CLSM.
2.6. Photocytotoxicity assay
The photocytotoxicity of YSiPc@MPEG5000–PCL2000 and YZnPc@MPEG5000–PCL2000
against MCF-7 breast cancer cells was studied using the CCK-8 assay method. Briefly,
MCF-7 breast cancer cells were seeded into 96-well plates with DMEM culture media
ꢀ
with a density of 1 ꢄ 105 cells per well. The cells were cultured for 24 h at 37 C under
5
% CO before treatment. After the DMEM culture medium was removed,
2
YSiPc@MPEG5000–PCL2000 and YZnPc@MPEG5000–PCL2000 with different concentrations
in DMEM were added to the wells, respectively. The cells were incubated for 12 h at
ꢀ
7 C under 5% CO . Then the cells were irradiated with a 670 nm laser (100 mW/cm )
2
2
3
for 10 min, and a control experiment was conducted without irradiation. The standard
CCK-8 assay was carried out to evaluate the cell viability.
3. Results and discussion
3.1. Synthesis and characterization of YSiPc and YZnPc
The synthetic routes for prop-2-ynyloxybenzyloxy axially/peripherally substituted YSiPc
and YZnPc are shown in Scheme 1. Reaction of SiPcCl with Y1 in the presence of
2
pyridine and toluene led to YSiPc in 25.6% yield. YSiPc was purified by silica gel col-
umn chromatography. To synthesize the peripherally substituted YZnPc, Y1 was
reacted with 4-nitrophthalonitrile through a typical electrophilic substitution reaction
to obtain 4-(3,5-bis(prop-2-ynyloxy)benzyloxy)phthalonitrile, Y2, in 35.6% yield. Y2 con-
densed with Zn(CH COO) using DBU as a catalyst in the presence of n-pentanol to
3
2
obtain YZnPc in 15.6% yield. Both YSiPc and YZnPc showed high solubility in common
organic solvents such as CH Cl , DMF, methanol, chloroform and DMSO.
2
2
These new compounds were characterized by a combination of methods including
1
elemental analysis, IR, H NMR and ESI-MS. The results were consistent with the pro-
posed structures. In the IR spectrum, the structure of YSiPc was clearly confirmed by
ꢂ1
ꢂ1
the vibration of Si-O bond at 1083 cm and the vibration of CꢁC bond at 2122 cm
.

JOURNAL OF COORDINATION CHEMISTRY
7
Scheme 1. The synthetic routes for YSiPc and YZnPc.
ꢂ1
YZnPc also exhibit a characteristic band at 2230 cm which was assigned to the CꢁC
vibration (Supporting Information, Figures S1–S4). YZnPc exhibited bands at
ꢂ1
1
452–1485 cm , which were from the vibration of C ¼ C and C ¼ N groups of the
1
phthalocyanine ring. The H NMR spectra of Y1, Y2 and YSiPc were consistent with
proposed structures ( Supporting Information, Figures S5–S7). The proton belonging
to the alkynyl group was observed at ꢂ0.71 ppm as a singlet. The resonances for 16
aromatic protons of the phthalocyanine ring were observed between 9.6 and 8.3 ppm
and the resonances for aliphatic protons of substituents at 3.76 and 2.77 ppm.
The maximum molecular ion peaks of Y1, Y2, YSiPc and YZnPc were accorded with
the theoretical calculated values of these complexes (Supporting Information,
Figures S8–S11).
In order to endow water solubility and enhance cell target ability of YSiPc and
YZnPc, PEG5000–PCL2000 was used as a nanocarrier to encapsulate YSiPc and YZnPc.
The critical micellar concentration (CMC) of PEG5000–PCL2000 at room temperature is
0.011 g/L, which was measured by UV/Vis spectra (Supporting Information, Figure S12).
3.2. The photophysical and photochemical properties of YSiPc and YZnPc
The photophysical properties of YSiPc and YZnPc in DMF are summarized in
Supporting Information Table S1. The UV/Vis spectra of YSiPc and YZnPc are shown in
Figure 1(A). Typical spectra for YSiPc and YZnPc were observed with a B band at
3
58 nm and a Q band at 675 nm. The Q bands of the YSiPc and YZnPc were red

8
S. XIAO ET AL.
Figure 1. UV/Vis spectra, fluorescence spectra, and fluorescence decay curves of YSiPc and YZnPc.
A) UV/Vis spectra; (B) fluorescence spectra; (C) fluorescence decay curves (CYSiPc/YZnPc ¼ 10 lM).
(
shifted compared to unsubstituted zinc phthalocyanine (at 670 nm), which could be
explained by the electron-withdrawing effect of alkynyl groups of the YSiPc and
YZnPc. Compared with YSiPc, the Q band of YZnPc was red-shifted about 3 nm, per-
haps due to the electron-withdrawing ability of the alkynyl substituents. The more
alkyl groups, the more red-shifted Q band was observed [26].
The fluorescence spectra and fluorescence decay curves of YSiPc and YZnPc in DMF
are shown in Figure 1(B–C). The numbers of alkynyl groups also affected the fluores-
cence intensity, fluorescence lifetimes as well as fluorescence quantum yields of YSiPc
and YZnPc. The fluorescence emissions of YSiPc and YZnPc were observed at 685 and
689 nm, respectively. The fluorescence spectra of YSiPc and YZnPc were mirror images
of absorption spectra, suggesting that the structures of molecules did not change
upon excitation in DMF. Compared with the fluorescence spectrum of YSiPc, YZnPc
exhibited weaker fluorescence intensity but bigger Stokes shifts. The fluorescence
quantum yields (U ) of YSiPc and YZnPc were 0.13 and 0.08, respectively. The fluores-
F
cence lifetimes were 7.99 ns for YSiPc and 3.66 ns for YZnPc. The fluorescence quan-
tum yield (U ) and fluorescence lifetime of YSiPc were larger than that of YZnPc. This
F
could be explained that phthalocyanines with peripheral substituents could form
aggregates easier than that with axial substitution [27]. The singlet oxygen quantum
yields (U ) of YSiPc and YZnPc were determined by a chemical method. DPBF was
D
used as a singlet oxygen quencher in DMF. The absorption spectra of DPBF solution
containing YSiPc and YZnPc are shown in Supporting Information Figure S13. The UD
values of YSiPc and YZnPc were 0.46 and 0.50, respectively (Supporting Information
Table S1). The U value of YZnPc was larger than YSiPc, attributed to the tetra-substi-
D
tuted derivative has more alkynyl groups compared to axially substituted derivative,
which increase the intersystem crossing from singlet state to triplet state [28].
3.3. Characterization of polymeric nanoparticles
The morphologies and hydrodynamic sizes of YSiPc@MPEG5000–PCL2000 and YZnPc@
MPEG5000–PCL2000 were studied by transmission electron microscope (TEM) and
dynamic light scattering (DLS) (Figure 2). The mean hydrodynamic diameters of
YSiPc@MPEG5000–PCL2000 and YZnPc@MPEG5000–PCL2000 were 111 and 77 nm,
respectively. The TEM images showed that the polymeric nanoparticles are spherical
with a diameter of 90 nm for YSiPc@MPEG5000–PCL2000 and 62 nm for YZnPc@
MPEG5000–PCL2000. The sizes of nanoparticles observed by TEM were smaller than their

JOURNAL OF COORDINATION CHEMISTRY
9
Figure 2. The TEM images and DLS of polymeric nanoparticles. (A) YSiPc@MPEG5000–PCL2000; (B)
YZnPc@MPEG5000–PCL2000
.
corresponding hydrodynamic diameters, which could be attributed to the swollen
state of polymeric nanoparticles in water. The UV-Vis spectra, fluorescence spectra
and fluorescence lifetimes of polymeric nanoparticles are shown in Figure 3. The
absorption and fluorescence intensity of YSiPc@MPEG5000–PCL2000 and YZnPc@
MPEG5000–PCL2000 were lower than that of free YSiPc and YZnPc, which could be due
to aggregation of YSiPc and YZnPc in nanoparticle microenvironments (the encapsula-
tion efficiencies (EE) of YSiPc and YZnPc in nanoparticle are shown in Supporting
Information Table S2). Meanwhile, the maximum fluorescence emission of
YSiPc@MPEG5000–PCL2000 and YZnPc@MPEG5000–PCL2000 are red-shifted compared to
the corresponding free YSiPc and YZnPc. The fluorescence lifetimes were 3.15 ns for
YSiPc@MPEG5000–PCL2000 and 2.89 ns for YZnPc@MPEG5000–PCL2000 in water, which
was shorter than YSiPc and YZnPc in DMF. This may be due to the microenvironment
of the nanoparticles which lead the aggregation of the phthalocyanines, quenching
the fluorescence of YSiPc and YZnPc [29].
3
.4. Cellular uptake of polymeric nanoparticles
After the polymeric nanoparticles were incubated with MCF-7 breast cancer cells for
2 h, a bright fluorescence was observed for both YSiPc@MPEG5000–PCL2000 and
1
YZnPc@MPEG5000–PCL2000 in breast cancer cells (Figure 4), indicating that the poly-
meric nanoparticles incorporated in cells.
3.5. Cellular ROS produce ability
ROS is a crucial indicator for evaluating the PDT efficiencies of polymeric nanoparticles.
CM-H DCFDA was used as a probe to detect the ROS generation ability of two poly-
2
meric nanoparticles in MCF-7 cells. MCF-7 breast cancer cells were first incubated with
YSiPc@MPEG5000–PCL2000 and YZnPc@MPEG5000–PCL2000, then they were incubated
with CM-H DCFDA. After being incubated with the breast cells, CM-H DCFDA is con-
2
2
verted to CM-H DCF inside the cells, which is non-fluorescent. CM-H DCF reacted with
2
2

1
0
S. XIAO ET AL.
Figure 3. Photophysical properties of YSiPc, YZnPc, YSiPc@MPEG5000–PCL2000
,
and
YZnPc@MPEG5000–PCL2000. (A) UV/Vis spectra; (B) fluorescence spectra; (C) fluorescence decay curves
of YSiPc, YZnPc, YSiPc@MPEG5000–PCL2000, and YZnPc@MPEG5000–PCL2000 (CYSiPc/YZnPc ¼ 10 lM).
Figure 4. Cellular fluorescence images of polymeric nanoparticles in MCF-7 breast cancer cells after
incubation for 12 h. YSiPc@MPEG5000–PCL2000; (B) YZnPc@MPEG5000–PCL2000 (all at 1 lM, kex
¼
860 nm, kem ¼ 640–700 nm).
1
O generated in the cells leading to CM-DCF which exhibited green fluorescence. As
2
shown in Figure 5, for MCF-7 cells treated with CM-H DCFDA without light, almost no
2
fluorescence was observed for YSiPc@MPEG5000–PCL2000 or YZnPc@MPEG5000–PCL2000
,
1
indicating little O generation in the cells. For MCF-7 cells, CM-H DCFDA, and poly-
2
2
meric nanoparticles treated with light, strong green fluorescence was observed in the
1
cells, demonstrating that intracellular O2 could be generated. Compared with
YZnPc@MPEG5000–PCL2000, stronger fluorescence was observed for YSiPc@MPEG5000
–
PCL2000 suggesting the YSiPc@MPEG5000–PCL2000 possessed better singlet oxygen
producing ability.

JOURNAL OF COORDINATION CHEMISTRY
11
Figure 5. Confocal images of the ROS generation ability of polymeric nanoparticles in MCF-7 cells
before or after irradiation using CM-H DCFDA as the probe. (A) YSiPc@MPEG5000–PCL2000; (B)
2
2
YZnPc@MPEG5000–PCL2000 (k ¼ 670 nm, 32 mW/cm , 5 min).
Figure 6. The cytotoxicity and phototoxicity of polymeric nanoparticles against MCF-7 cells in the
2
absence and presence of light (k ¼ 670 nm, 100 mW/cm , 10 min). (A) YSiPc@MPEG5000–PCL2000; (B)
YZnPc@MPEG –PCL .
2000
5
000
3.6. Photocytotoxicity of polymeric nanoparticles
The cytotoxicity as well as phototoxicity of YSiPc@MPEG5000–PCL2000 and YZnPc@
MPEG5000–PCL2000 were evaluated by a CCK-8 assay method. As shown in Figure 6,
YSiPc@MPEG5000–PCL2000 and YZnPc@MPEG5000–PCL2000 showed almost no toxicity to MCF-7
cells in the absence of light. After being incubated with the same concentration nanoparticles (4
uM), 70% of cell viability was observed for YZnPc@MPEG5000–PCL2000, but only 8% of cell viabil-
ity was observed for YSiPc@MPEG5000–PCL2000. The IC50 value was 0.35 lM for
YSiPc@MPEG5000–PCL2000, which exhibited better PDT efficacy and is a good candidate for PDT.
4. Conclusion
Two prop-2-ynyloxybenzyloxy axially/peripherally substituted zinc/silicon phthalocya-
nines (YSiPc and YZnPc) were synthesized and characterized. The photophysical and

1
2
S. XIAO ET AL.
photochemical properties of these phthalocyanines exhibited central metal ion
dependence. The fluorescence intensity, fluorescence quantum yield and fluorescence
lifetime of YSiPc were higher than for YZnPc. Therefore, prop-2-ynyloxybenzyloxy
groups at axial positions could suppress aggregation better than that at a peripheral
position. YSiPc and YZnPc were encapsulated into MPEG5000–PCL2000 to form poly-
meric nanoparticles. Nanoparticles were effectively internalized into MCF-7 breast can-
cer cells. YSiPc@MPEG5000–PCL2000 exhibited higher intracellular ROS generation ability
than YZnPc@MPEG5000–PCL2000. Upon irradiation, YSiPc@MPEG5000–PCL2000 exhibited
higher
photocytotoxicity
against
MCF-7
breast
cancer
cells
than
YZnPc@MPEG5000–PCL2000. YSiPc@MPEG5000–PCL2000 is a promising photosensitizer
for PDT.
Disclosure statement
No potential conflict of interest was declared by the authors.
Funding
This research was supported by the National Key Basic Research Program of China (973 project)
(2015CB352006), the National Natural Science Foundation of China (21274021), the Natural
Science Foundation of Fujian (2019Y0007), the Scientific Research Innovation Team Construction
Programme of Fujian Normal University (IRTL 1702), Special funds of the Central Government
Guiding Local Science and Technology Development (2017L3009) and the Science and
Technology Fund project of Fujian province (No. 2018Y9081) and the Joint Funds of Fujian
Provincial Health and Education Research (2019-WK-23).
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