Modified PAMAM dendrimers as a matrix for the photostabilization of curcumin

Article abstract of DOI:10.1039/d0nj02737e

Six recently synthesised poly(amidoamine) (PAMAM) dendrimers from zero, first and second generations modified with 1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione (curcumin) and 2,4-dihydroxybenzophenone (CU-1, CU-2, CU-3, CU-4, CU-5 and CU-6) have been investigated in water/dioxane (4 : 1) (v/v) solution by absorption and fluorescence spectroscopy in order to determine their photostability. It has been found that the photostability of curcumin is enhanced upon its incorporation into the dendrimer molecule, and a new additional stabilization is achieved by bonding of 2,4-dihydroxybenzophenone as a UV absorber to the dendrimer molecule. It has also been established that the generation of dendrimers impacts upon this parameter as the photostabilizing effect enhances at a higher dendrimer generation. The photostability of the dendrimers has also been investigated after their deposition onto a polyethylene terephthalate (PET) fabric. This journal is

Full text of DOI:10.1039/d0nj02737e

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Modified PAMAM dendrimers as matrix for
photostabilization of curcumin
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Mohammad Dodangeha,b,*, Ivo Grabchev , Kamaladin Gharanjig , Desislava Staneva , Ren-Cheng Tang ,
c,*
a,d,*
e
b
Matthew Sheridanf
aDepartment of Organic Colorants, Institute for Color Science and Technology, Tehran 16765-654, Iran.
bNational Engineering Laboratory for Modern Silk, College of Textile and Clothing Engineering, Soochow University, 199
Renai Road, Suzhou 215123, China.
cSofia University “St. Kliment Ohridski”, Faculty of Medicine, Sofia1407, Bulgaria.
dCenter of Excellence for Color Science and Technology, Institute for Color Science and Technology, Tehran 16765-654,
Iran.
eUniversity of Chemical Technology and Metallurgy, 1756 Sofia, Bulgaria,
fDepartment of Chemistry, Florida University, United States.
*Corresponding author: i.grabchev@chem.uni-sofia.bg
Six recently synthesised poly(amidoamine) (PAMAM) dendrimers from zero, first and second generations
modified with 1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6- heptadiene-3,5-dione (curcumin) and 2,4-
dihydroxybenzophenone (CU-1, CU-2, CU-3, CU-4, CU-5 and CU-6) have been investigated in water/dioxane
(4:1) (v/v) solution by absorption and fluorescence spectroscopy in order to determine their photostability. It
has been found that the photostability of curcumin is enhanced upon its incorporation into the dendrimer
molecule, and a new additional stabilization is achieved by bonding of 2,4-dihydroxybenzophenone as a UV
absorber to the dendrimer molecule. It has also been established the dendrimers generation impact upon this
parameter as the photostabilizing effect enhances at a higher dendrimer generation. The photostability of
dendrimers have also been investigated after their deposition onto a polyethylene terephthalate (PET) fabric.
Keywords: Curcumin; 2,4-dihydroxybenzophenone; Photostability; Fluorescence; PAMAM.
Introduction
Curcumin is a natural yellow fluorescent dye extracted from the root of the dry rhizomes and has many
applications in health care as a design of fluorescence chemosensor, food and beverages colorant, and in dyeing
of textile fibres.1–8 Nevertheless, the poor photostability of curcumin has limited its application in the
aforementioned areas.9–11 Therefore, to continue expanding its usage and areas of application, it has been
essential to develop procedures aiming at improvement of its photostability.11–14 In this connection the extensive
efforts have been made to photostabilize the curcumin11,13,17–18 including complexation with proteins,17
liposome and phospholipid,18 encapsulation into baker's yeast cells, β-cyclodextrin and starch,19 polymeric
nanoparticles,20,21 copolymer micelles,22 and hydrogels.23 Most of the above mentioned approaches have been

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considered unavailing for practical purposes due to the complicated preparation procedure, limited efficiency
and insufficient accessibility. Accordingly, the attempts to find a more suitable procedure to improve the
photostability of curcumin are still greatly appreciated.
PAMAM dendrimers are a special class of hyperbranched polymers with a wide range of applications.24,25
Different modified PAMAM dendrimers have been find application in the biomedicine,26,27 sensors,28–31 dyes,32–
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and textiles.35,36 To the best of our knowledge, thus far, the modification of dendrimers with curcumin for
enhancing their photostability have not been investigated. With this regard, recently we have synthesised new
PAMAM dendrimers from zero, first and second generation, modified with curcumin and UV-absorber. They
have been used as days for polyethylene terephthalate fabrics.1,2 Their photophysical characteristics and sensor
ability to detect metal ions and protons has also been investigated.2–3 The photostability of such sensor systems,
containing curcumin as signalling fragment is very important, for which are known to have low light resistance.
The aim of this work is to investigate the effect of the PAMAM dendrimer generation influence upon the
photostability of the chemically bonded curcumin to the dendrimers. The effect of 2,4-dihydroxybenzophenone,
on curcumin photostability has also been investigated. The light resistance of dyed polyethylene terephthalate
fabrics with dendrimers have also been evaluated.
Materials and Methods
All chemicals and instruments used in this study are listed in Table S1 and Table S2, respectively.
Results and discussion
Modified PAMAM dendrimers with curcumin
PAMAM dendrimers of zero, first and second generations were synthesized by a divergent synthetic method
employing the reagent excess method starting from ethylenediamine by consecutive Michael addition and ester
amidation reaction according to our previous reports.29,35 To synthesize the complete generation of PAMAM
dendrimer, ethylenediamine was dissolved in methanol and cooled down. Methyl acrylate was then added drop-
wise at stirring condition and under nitrogen atmosphere. The mixture was kept at ambient temperature for 168
h. The surplus of methyl acrylate and solvent was removed under vacuum at the temperature below 50°C
resulting in a nearly colourless viscous solution of dendrimers. The synthesized dendrimers were modified with
curcumin and 2,4-dihydroxybenzophenone by the method described recently.1,2 Modified with curcumin and
benzophenone PAMAM dendrimers of various generations were obtained in a three-step synthesis. 2,4,6-
Trichloro-1,3,5-triazine (Cyanuric chloride) has been used as a bridging agent between them, and its possibility
of a gradual replacement of chlorine atoms depending on the thermal conditions has been used.

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N
Cl
N
Cl
N
N
NH2
NH
Cl
H N
N
2
Cl
N
Cl
N
NH
NH
O
O
NH
O
O
HN
O
O
N
N
O
O
HN
N
N
Cl
Cl
N
N
NH
HN
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T = 0-5 C
NH
NH
HN
NH2
H N
2
NH
N
N
Cl
Cl
N
N
N
N
Cl
Cl
R -OH
1
o
T = 30-35 C
Cl
N
OR1
N
N
N
OR1
Cl
N
N
NH
NH
NH
O
O
HN
N
N
NH
HN
O
O
NH
NH
N
N
Cl
R O
1
N
N
N
N
R O
1
Cl
R -OH
R -OH
1
2
o
T = 70-75 C
R O
1
R O
OR1
N
OR1
2
N
N
N
N
N
N
N
N
OR1
OR1
R O
N
R O
N
1
2
NH
N
NH
NH
NH
O
O
O
O
NH
O
O
NH
HN
HN
N
N
N
N
NH
NH
NH
HN
O
HN
O
NH
NH
NH
N
N
N
N
N
OR1
OR2
R O
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R O
1
N
N
N
N
N
N
N
CU-1
R O
1
CU-4
R O
1
OR1
OR2
O
O
OH O
MeO
HO
OMe
OH
R -OH =
1
R -OH =
2
HO
curcumin
benzophenone
Scheme 1. Chemical structure and synthesis route of dendrimers CU-1 and CU-4.
The peripheral primary amino groups of PAMAM dendrimers from different generations have been reacted
with cyanuric chloride at low temperature (t = 0-5 °C). The nucleophilic substitution of the second chlorine
atom of the triazine cycle with curcumin was carried out at a temperature of 30-35 °C, while the benzophenone

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moieties were introduced to the dendrimer structure at a higher temperature (70-75 °C). Thus, six modified
PAMAM dendrimers of zero (CU-1, CU-4), first (CU-2, CU-5), and second (CU-3, CU-6) generation with
covalently bounded benzophenone and curcumin residues were synthesized (Table S3). Their chemical
structures and synthesis route of these compounds are depicted in Scheme 1 and Scheme 2. Meanwhile, the
1
chemical structure of modified dendrimers was analysed using analytical techniques including FTIR, H-NMR,
13C-NMR, elemental analysis and DSC and results summarized in Table S4.
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R1O
N
OR1
OR1
R O
OR1
OR1
R O
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2
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R O
N
2
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N
N
N
N
N
N
N
NH2
HN
NH2
HN
OR1
OR2
R1O
HN
O
N
N
R O
HN
O
N
N
NH
1
NH
N
N
O
N
N
O
NH
N
NH
N
N
HN
N
HN
HN
O
HN
O
NH
O
NH
O
OR1
OR1
R1O
N
N
R O
N
N
2
NH
NH
O
O
NH
NH
O
O
N
N
N
N
O
O
HN
O
HN
O
O
O
HN
HN
O
O
O
R1O
N
OR1 R O
N
O
N
1
N
OR2
N
N
N
NH
HN
N
NH
HN
N
N
N
HN
NH
N
HN
NH
N
N
HN
NH
N
HN
NH
N
R1O
O
R O
O
NH
2
NH
OR1
OR1
HN
HN
N
N
N
N
N
N
N
N
CU-2
N
CU-5
R O OR2
N
R1O
OR1
R1O
N
OR1
1
R O
N
OR2
1
7
0-75 °C
OR1
R1O
R1O
N
R2O
N
OR1
R2O
N
R2O
N
OR1
R1O
N
OR1
OR1
OR1
N
N
N
N
N
N
N
N
N
N
N
N
N
R1O
N
N
OR1
R2O
OR1
N
N
OR1
N
NH
NH
N
NH
NH
HN
HN
HN
HN
R1O
N
R2O
OR1
N
NH HN
HN
NH HN
N
NH
NH HN
N
N
N
O
N
O
O
O
O
N
OR1
N
O
O
O
N
OR1
R1O
NH
R2O
NH
N
N
N
N
N
N
HN
O
HN
O
NH
NH
O
O
HN
HN
HN
O
HN
HN
O
NH
NH
O
O
N
N
N
HN
N
HN
NH
NH
NH
O
NH
R1O
N
N
O
O
R1O
HN
N
N
O
O
N
O
O
NH
N
OR1
N
O
NH
N
OR2
HN
NH
HN
NH
N
O
NH
N
N
N
N
O
NH
N
N
N
N
N
O
O
R1O
OR1
R2O
OR1
OR2
OR1
N
N
N
OR1
N
N
N
OR1
N
O
N
O
HN
N
HN
N
O
O
R1O
N
HN
HN
R2O
N
HN
HN
O
O
O
O
NH
N
OR1
O
O
O
O
NH
N
OR1
N
N
N
N
HN
HN
HN
HN
NH
NH
NH
HN
NH
HN
N
N
N
N
HN
O
O
HN
O
O
O
NH
O
NH
NH
NH
O
O
O
O
N
N
R1O
N
HN
N
NH
R1O
N
HN
N
NH
N
OR1
N
OR2
O
O
N
N
O
O
N
N
N
O
O
N
1
NH HN
N
NH HN
N
OR1
NH HN
R1O
OR2
NH HN
R O
HN
N
NH
N
HN
N
NH
N
NH
N
HN
NH
N
N
N
N
N
HN
N
N
N
N
R1O
N
R1O
N
OR1N
R1O
N
OR2N
R1O
N
OR1
OR2
CU-3
OR1
R1O
N
CU-6
OR2
R O
N
R O
1
N
OR1
R O
1
N
OR2
1
O
O
OH O
MeO
HO
OMe
OH
R -OH =
1
R -OH =
2
HO
Scheme 2. Chemical structures of curcumin and 2,4-dihydroxybenzophenone conjugated to PAMAM
dendrimer of first and second generations (CU-2, CU-3, CU-5, CU-6).
Photodegradation of curcumin and modified dendrimers in solution based on absorption and
fluorescence measurements
Due to its photosensitivity, curcumin is easily degrading to the different compounds when exposed to the light.15
This research intends to find the photodegradation rate of the curcumin before and after its modification with
PAMAM dendrimer and 2,4-dihydroxybenzophenone as a UV-absorber. Normalised absorption spectra of

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initial compounds: curcumin and 2,4-dihydroxybenzophenone were plotted in Figure 1. Both compounds
absorb at different spectral region: the absorption maximum of curcumin is at 419 nm, while benzophenone
absorbs in the ultraviolet region with a maximum at 278 nm. The Figure 1 also shows considerable overlap
between the two spectra. The coupling of these substances to the dendrimer structure does not significantly alter
the spectral curve, as can be seen from the absorption spectrum of dendrimer CU-5 and CU-6 given as an
example.
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Figure 1. Normalised UV-vis absorption spectra of curcumin, 2,4-dihydroxybenzophenone, CU-5 and CU-6.
As can be seen from Schemes 1 and 2, the dendrimers tested contain different numbers of curcumin and 2,4-
dihydroxybenzophenone units. Figure 2A shows the dependence of the molar absorption coefficient (ɛ) of the
dendrimer generation, compared to the monomeric units. The results show a progressive increase in the values
of ɛ depending on the number of curcumin and 2,4-dihydroxybenzophenone units bonded to the dendrimer
structure. The lower values of dendrimers CU-4–CU-6 are because in them the number of curcumin units is
smaller due to the presence of 2,4-dihydroxybenzophenone units. These results show that in the dendrimer
structures, the curcumin units are respectively as follows: 8 (CU-1), 16 (CU-2), 32 (CU-3), 4 (CU-4), 8 (CU-5)
and 16 (CU-6), which has also been confirmed by the corresponding NMR spectra (Table S4). A similar
dependence of the fluorescence intensity of dendrimers is recorded, as can be seen from Figure 2B. Dendrimers
have different quantum yields (Curcumin: 0.302, CU-1: 0.414, CU-2: 0.638, CU-3: 0.747) and fluorescence
intensities respectively.1,3 The changes in the fluorescence quantum yields and molar absorption coefficient of
the modified curcumins in accordance with the generation of dendrimers revealed that the photo-induced
electron transfer proceeded from the core of the dendrimer molecule to the curcumin fluorophores located in its
periphery which obviously affect the energy transfer upon excitation, thus increasing the fluorescence intensity
and molar absorption coefficient.28 On the other hand, the values of these indicators may be influenced
by different factors such as the polarity of organic solvents and possible dipole-dipole interactions.
The formation of hydrogen bonds can also lead to a change in the polarization of the curcumin
chromophore system and non-irradiative deactivation processes to predominate in the S
transition. 3
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Figure 2. A: Molar extinction coefficient of curcumin, 2,4-dihydroxybenzophenone and dendrimers (A):
Fluorescence intensity of curcumin and CU-1– CU-3 (B).
The stability of curcumin and its derivatives, CU-1, CU-2, CU-3, CU-4, CU-5 and CU-6 was assessed by
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exposing their solutions (water/dioxane (4:1) (v/v), c=5×10 mol/L) to a UV lamp at 290-315 nm (peak at 302
nm) (9W, 240V) and ambient temperature and then the effect of light on their absorbance and fluorescence
spectra investigated. Figure 3 shows the change of absorbance of curcumin and its dendrimer derivatives
according to the irradiation time (Figure 3a-g). It is clear that the absorption decreases with the irradiation time
due to the destruction of the chromophore system of curcumin. This effect was better pronounced in the case of
monomeric curcumin. The smallest change in the absorption has been observed for CU-6 dendrimer, which
contain sixteen fragments of curcumin and sixteen fragments of 2,4-dihydroxybenzophenone. Furthermore, the
changes in the position of the absorption maximum have been observed. In this case during the irradiation, the
absorption maximum of curcumin and modified dendrimers are hypsochomically shifted with approximately
4
0 nm. The highest change has been achieved for monomeric curcumin, which can be explained by different
absorbance of the respective decomposed products. From the other hand the autooxidative transformation of
curcumin via the mechanism described by Griesser et. al. might be the possible reason for the highest level of
hypsochromic and hypochromic shifts for curcumin.16 Figure 3h plots the photodegradation rate (PR) of
curcumin and modified dendrimers during irradiation based on absorption spectroscopy from which the linear
dependence of the photodegradation process with following equations has been observed: PR
2
2
(
curcumin)(t)=3.67t-4.396 (R =0.981), PR (CU-1)(t)=3.23t-3.256 (R =0.986), PR (CU-2)(t)=2.71t-1.682
2
2
2
(
R =0.994), PR (CU-3)(t)=2.38t-4.342 (R =0.988), PR (CU-4)(t)=1.45t-2.363 (R =0.983), PR (CU-5)(t)=0.99t-
2
2
3
.613 (R =0.953), PR (CU-6)(t)=0.56t-1.076 (R =0.961).

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Figure 3. UV-vis absorption spectra of curcumin (a) and dendrimers CU-1 (b), CU-2 (c), CU-3 (d), CU-4 (e),
-6
CU-5 (f), CU-6 (g) in water/dioxane solution (4:1) (v/v) at concentration c=5×10 gl/L and dependence of
photodegradation to the irradiation time (h).
After irradiation of 24 hours, 88% of curcumin, 77% of CU-1, 65% of CU-2, 57% of CU-3, 35% of CU-4, 24%
of CU-5 and 12% of CU-6 have been degraded (Figure 4). This clearly shows that, after the binding of curcumin
to the dendrimer periphery, its photodestruction has been reduced and this is proportional to the number of
curcumin fragments. At dendrimers CU-1 - CU-3, the photostability of the CU-3, containing 32 photoactive
curcumin fragments is highest i.e. the dendrimer structure affects the stability of curcumin. On the other hand,
the incorporation of 2,4-dihydroxybenzophenone into the dendrimer molecule at a ratio of 1:1 to curcumin,
stabilizes its photodestruction processes by 55-79%. This indicates that the 2,4-dihydroxybenzophenone has a
strong influence on the photostability of curcumin, with the dendrimer generation also having a stabilizing
impact. This effect is similar in the cases of dendrimer sensors, dendrimers with microbiological activity or
drug delivery systems.37,38
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CU
CU1CU4
CU2CU5
CU3CU6
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PAMAM Generation
Figure 4. Photodegradation of curcumin (CU) and PAMAM dendrimers (CU1–CU6) after 24h irradiation.
Table 1. Photodegradation Rate (PR) of curcumin and dendrimers CU-1—CU-6 based on absorbance,
fluorescence in solution and fluorescence on solid PET.
Compounds
Absorbance
Fluorescence
PR (%/h) R2
Fluorescence on PET
PR (%/h) R2
PR (%/h)
R2
Curcumin
CU-1
3.67
3.23
2.71
2.38
1.45
0.99
0.52
0.980
0.986
0.995
0.988
0.983
0.873
0.961
3.42
3.07
2.34
2.15
1.23
0.83
0.33
0.958
0.957
0.972
0.966
0.985
0.929
0.904
3.21
2.55
2.00
1.78
0.99
0.53
0.24
0.953
0.963
0.982
0.983
0.970
0.950
0.933
CU-2
CU-3
CU-4
CU-5
CU-6

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The photodegradation of curcumin and dendrimers has also been investigated by fluorescence spectroscopy as
more precise analytic method. The fluorescence intensity of all compounds has been measured after their
excitation at the absorption maxima. The photodegradation rate of dendrimers has also been evaluated on the
basis of fluorescence intensity during the irradiation (Figure 5). The photodegradation process of curcumin had
occurred easily and quickly in comparison to those of the modified dendrimers. The highest and lowest
photodegradation rates were obtained for curcumin (3.42) and dendrimer CU-6 (0.33) respectively, what is in
accordance with the results obtained by absorption spectroscopy (Table 1).
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Figure 5. Dependence of photodegradation of curcumin and dendrimers CU-1–CU-6 to time in water/dioxane
-6
(
4:1) (v/v) solution at concentration of 5×10 mol/L based on fluorescence intensity.
Figure 6 shows the change in the fluorescence spectra of curcumin and its dendrimer derivatives CU-3 and
CU-6 as a typical example. The difference between the dendrimers is only in the nature of the substituents.
Dendrimer CU-3, has thirty-two curcumin units, while for CU-6 they are sixteen and the remaining sixteen are
substituted with 2,4-dihydroxybenzophenone. The three compounds have different quantum yields and
fluorescence intensities respectively.1,3 The comparison of their properties gives us a good possibility for the
explanation of the effect of substituents on curcumin photostabilization. It was observed that the
photodegradation of the initial curcumin is the greatest extent (Figure 6A). After its binding to the dendrimer
molecule, the destruction is delayed (Figure 6B). In the case of dendrimer CU-6 which molecule have sixteen
2
,4-dihydroxybenzophenone units, this process was very low pronounced (Figure 6C).

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Figure 6. Fluorescence spectra of curcumin (A) and dendrimers CU-3 (B), CU-6 (C), in water/dioxane solution
-6
(
4:1) (v/v) (c=5×10 mol/L), depending on the irradiation time (λex= 420 nm)
It is known that the hydroxyl group from 2,4-dihydroxybenzophenone is rapidly converted into a "phenol" form
by absorption of light energy (Scheme 3). This phenomenon arises from its ability to undergo intramolecular
proton transfer from the hydroxyl group to the adjacent carbonyl group following light absorption in the UV
region. This is an internal conversion process, as the absorbed UV light energy dissipates as harmless heat, with
39
almost 100% efficiency. On the other hand, it might be attributed to the fact that during the absorption of the
light, dendritic structure converts the light energy into fluorescence emission and reduced the destructive effect
of light.40
Scheme 3. Proposed internal conversion process of the 2,4-dihydroxybenzophenone with absorbing the UV
light energy.
Photodegradation of dyed polyethylene terephthalate (PET) fabrics
UV absorbers and antioxidant compounds could be used to neutralize the destructive effect of the energy
3
7
absorbed from the UV light. For this purpose, the UV absorbers and antioxidant could be applied on textiles
materials by different procedures, while most of them need to be used in a separate process that is time and
energy-consuming. The synthesised dendrimers in this research included a UV absorber which could be
attached to the textiles at the same step of dyeing processes. To examine the photostability of the synthesized
compounds, PET fabrics were dyed using curcumin, CU-1, CU-2, CU-3, CU-4, CU-5 and CU-6 according to
our previous works.41,42 Then, the dyed fabrics were irradiated for 24 hours and their fluorescence spectra were
recorded in dependence of irradiation time. The fluorescence spectra of dyed PET fabrics have also been studied

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during the irradiation and the results were plotted in Figure 7. The figure shows that upon irradiation, the
fluorescence intensity of the fabrics decreases, and this decrease depends on the type of the dendrimer. The
photodegradation rate of the PET fabrics dyed with curcumin and modified dendrimers during the irradiation
was determined (Figure 7h).
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Figure 7. Fluorescence spectra of PET fabrics dyed with curcumin (a) and synthesized compounds CU-1 (b),
CU-2 (c), CU-3 (d), CU-4 (e), CU-5 (f), CU-6 (g), dependence of photodegradation rate from the irradiation
time of curcumin and dendrimers CU-1–CU-6 on PET fabric (h).
It was of interest to compare the results from the photodestruction of curcumin and the corresponding
dendrimers in solution and after deposition of the PET fabrics using absorption and fluorescence spectroscopy
(
Figure 8). In all cases the photodestruction rate of monomeric curcumin is the highest. Its degradation has been
stabilised upon the attachment to dendrimer molecules. The introduction of more curcumin units leads to their
stabilization. Further stabilisation has been achieved using 2,4-dihydroxybenzophenone as a photostabiliser,
and the effect also depends on its amount into the dendrimeric structure. All calculated photodegradation rates
constants in the solid state are lower, if compared with those in the solution. This is most likely due to the
accelerated photodegradation process in humid environments which atmospheric humidity conditions play an
important role in the photocatalysed degradation of curcumin and all dendrimers.43
Figure 8. Photodegradation rate of curcumin and modified dendrimers in solution and on PET fabric by
absorption and fluorescence spectroscopy
Conclusions
The photostability of six recently synthetized PAMAM dendrimers from zero, first and second generation
modified with curcumin and 2,4-dihydroxybenzophenone as UV-absorber has been investigated in solution and
after their deposition on the PET fabric. The results have showed an increase in the photostability of curcumin

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after its binding to the dendrimer molecule. Further enhancement of photostability has been obtained inVie
presence of 2,4-dihydroxybenzophenone and the best results have been obtained for dendrimer CU-6. It has
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been shown that, the dendrimer generation also influences on the photostability, which increases with the
dendrimer generation. Curcumin and all dendrimers have been loaded on a polyethylene terephthalate fabric
and their photostability has been investigated by measuring the fluorescence intensity before and after
irradiation. The same dependence has been found as that from the investigations in solution, what indicates that
the test compounds retain their properties after being applied to the textile matrix. On the other hand, it means
the absence of negative influence of the textile matrix upon the dendrimers photodestruction. The good results
indicate that binding of curcumin to dendrimers leads to its photostabilization. On the other hand, the
multifunctionality of the dendrimer structures allows the introduction of compounds with UV absorber
properties, thus further stabilizing the light resistance of curcumin. These results upgrade our previous studies
of the same compounds and extend the possibility of using them as photostable sensors for metal ions and
protons or dendritic dyes.
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Conflicts of interest
There are no conflicts to declare.
Appendix A. Supplementary data
Supplementary data to this article can be found online at,,,,,,
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Graphical abstract