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S. Belali et al. / Polymer 109 (2017) 93e105
membrane without any aggregation.[11ꢁ14] Among the different
dyes that can be used as photosensitizer, porphyrins are have been
widely used clinically in PDT for cancer treatments because of their
capability to generate singlet oxygen efficiently and their tendency
to accumulate in tumor tissue.[15ꢁ17] However, porphyrin struc-
ture is unsuitable for biomedical applications because many of
porphyrins are hydrophobic in nature, which makes them unsol-
uble in aqueous and biological environment and tend to aggregate
in aqueous solutions, so exhibiting limited bio-distribution that
resulting in a loss of photochemical activity in biological environ-
ment.[18ꢁ23] One way to overcome this problem is introducing a
hydrophilic group that has good biocompatibility to the porphyrin
which is an effective strategy to increase the biocompatibility and
water solubility of porphyrin derivatives. On the other hand, usu-
ally systemic administration of porphyrin as photosensitizer can
cause high skin photosensitivity. Hence, much attention has been
focused in the development of photosensitizers that accumulate
preferentially in tumor tissue but not in other regions of the
body.[24ꢁ26] Recently, a considerable number of works have been
done on enhancing the properties of porphyrins by chemical
modification or covalent functionalization to obtain new de-
rivatives of porphyrin for specific applications. Zhang et al. inves-
tigated a micelle base on star-shaped amphiphilic copolymer with
porphyrin core for bioimaging and drug delivery. Lovell et al. re-
ported a porphyrin-cross-linked hydrogel for fluorescence-guided
monitoring and surgical resection.[27,28] All these results were
confirmed good biocompatibility and feasible fluorescence effi-
ciency of porphyrin for in vivo application. So, there is a great in-
terest in developing improved delivery systems through
incorporation of the photosensitizer into hydrogels structure and
nanoparticles to obtain photodynamic systems with high photo-
sensitizer activity that accumulate selectively in cancer
cells.[29ꢁ32] We found that design and preparation of polymeric
porphyrin photosensitizers using the porphyrin derivative as a
crosslinker, especially for hydrogels containing porphyrin, have
seldom been reported. Stimuli-responsive hydrogels have attracted
significant attention recently due to their ability to change their
volume in response to environmental stimuli such as temperature
or pH. They can be made responsive to other different factors, such
as, magnetic fields, light, electrical energy and solvent. Among
them, PNIPAAm hydrogels have attracted considerable attention
nowadays. The thermo-responsive hydrogels have been extensively
used as superabsorbents, drug delivery systems, human gene vec-
tors, biocatalysts, and adsorption/desorption sheets for cell cul-
tures, tunable optical devices, in separation and purification of
metal ions and biomolecules. Smart hydrogels based on poly (N-
isopropylacrylamide) (PNIPAAm) are now widely investigated due
to their wide applications in biomedical and pharmaceutical fields
such as controlled drug delivery, artificial muscles, cell adhesion
mediators and so on.[33,34] There is increasing interest in hydro-
gels with low-molecular-weight building blocks. In such systems,
the hydrogel has a fibrillar structure.[35] These fibers like hydrogels
are formed by disc-shaped 5,10,15, 20-tetrakis(4-N-carbonylacrylic
aminophenyl) porphyrin as cross linker to self-assemble the poly
(N-isopropylacrylamide) in aquatic environment into one-
nanodimensional structures.
we tried to design and synthesis of 5,10,15,20-tetrakis(4-N-carbon-
ylacrylicamino phenyl)porphyrin as a new crosslinker and describe
the preparation and characterization of new nanostructured photo-
dynamic hydrogels based on poly(N-isopropylacrylamide-co-
porphyrin) via in situ dispersion polymerization of NIPAAm with
5,10,15,20-tetrakis(4-N-carbonylacrylic aminophenyl) porphyrin (2%
and 4% w/w) cross-linked with MBA in water. The swelling behavior
of the prepared hydrogels was examined at different pHs and tem-
peratures. The LCST behavior of these hydrogels was investigated.
The results show that the increase in porphyrin content make the
LCST increase. The combination of 5, 10, 15, 20-tetrakis(4-N-car-
bonylacrylicaminophenyl)porphyrin with PNIPAAm is promising to
lead to fluorescent, pH-thermo dual responsive and photodynamic
hydrogels with unique properties for various applications. Produc-
tion of reactive singlet oxygen, cytotoxity and phototoxicity of P
[NIPAAm-co-CAA-TPP (2%)] and P[NIPAAm-co-CAA-TPP(4%)] as
photodynamic therapy (PDT) systems were investigated on
A453 cells. The study showed that the singlet oxygen production
ability of P[NIPAAm-co-CAA-TPP(2%)] can be well controlled by
irradiation time compared with free porphyrin. The results exhibited
that they are promising photodynamic systems for cancer therapy.
2. Experimental section
2.1. Material
p-Nitrobenzaldehyde, N-isopropylacrylamide (NIPAAm, 99%),
methylenebisacrylamide (MBA 99%), poly (N-vinylpyrrolidone)
25(PVP, average MW~292.23 g/mol) were purchased from Sigma-
Aldrich (St. Louis, USA). Potassium persulfate (KPS, 99%) was got
from Fluka (Sleeze, Germany). Pyrrole was vacuum distilled and
purchased from Sigma-Aldrich (St. Louis, USA). and other chemicals
were purchased from SigmaeAldrich, France. Deionized and
distilled water was used for all solution preparations.
2.2. Characterization
1H NMR data was obtained by a Bruker (Advance DPX300,
Switzerland) spectrometer with CDCl3, DMSO-d6 or D2O as solvent
at room temperature. The FT-IR spectroscopic measurements were
conducted on a Nicolet FT-IR spectrophotometer (Nexus 470,
Thermo Electron Corporation) at frequencies ranging from 400 to
4000 cmꢁ1, using KBr disks at room temperature (25 ꢀC). Fluores-
cence spectrum was performed at room temperature using a
fluorescence spectrophotometer (Cary Eclipse, AUS). The spectra
were recorded using the excitation mode. Ultravioletevisible
spectroscopy was recorded at room temperature using a Spectrum
lab54 UVevisible spectrophotometer. For Morphology observation,
hydrogels that swell to equilibrium at 25 ꢀC were freeze dried in a
freeze dry system (LANCONCO) to remove water completely. After
drying, the gel samples were sputter coated with gold, and struc-
tures and morphologies of the gel surfaces were then visualized by
a scanning electron microscope (Hitachi-X650). The rheological
properties of the hydrogels were determined using a modular
compact rheometer (MCR 300). The measurements were per-
formed in the dynamic mode and 25 mm parallel plate geometry
with gap setting of about 2 mm. The rheometer was equipped with
a convection oven in compressed air for temperature control. In
order to determine the effect of temperature, the heating rate was
set at 2 ꢀC/min in the range of 25e60 ꢀC. The storage modulus (G0)
and loss modulus (G00) were measured under a frequency of 0.1 Hz.
Thus, frequency sweep tests were carried out for all the samples, at
25 ꢀC (below LCST) and 45 ꢀC (above LCST), the frequency range was
0.01e1 HZ. The swelling kinetics of hydrogels was measured
gravimetrically. The dried samples were placed in distilled water at
However, LCST of PNIPAAm hydrogel is low, which hamper their
practical applications in biomedical fields. Therefore, improving the
LCST has become an important topic in the field of hydrogel mate-
rials. A desirable phase transition temperature of these materials
should be at or near the physiologic temperature (37 ꢀC).[36] In
recent years, much attention has been focused in the functionaliza-
tion of hydrogels based on PNIPAAm by bioactive compounds to
make bioactive materials with novel medical and therapeutic activ-
ities for applications in biomedical fields.[37] In the current report,