Journal of Biomaterials and Nanobiotechnology, 2013, 4, 357-364
http://dx.doi.org/10.4236/jbnb.2013.44045 Published Online October 2013 (http://www.scirp.org/journal/jbnb)
357
Upon the Delivery Properties of a Polymeric System Based
on Poly(2-Hydroxyethyl Methacrylate) Prepared with
Protective Colloids
Loredana E. Nita1, Aurica P. Chiriac1, Manuela Nistor1, Tatiana Budtova2*
1“Petru Poni” Institute of Macromolecular Chemistry, Iasi, Romania; 2Centre de Mise en Forme des Matériaux, Mines ParisTech,
UMR CNRS 7635, Sophia-Antipolis, France.
Received June 30th, 2013; revised July 30th, 2013; accepted August 15th, 2013
Copyright © 2013 Loredana E. Nita et al. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
ABSTRACT
A comparative study related to the preparation of poly(2-hydroxyethyl methacrylate) (pHEMA) through radical polym-
erization process in the presence of three different protective colloid substances, respectively poly(vinyl alcohol) (PVA),
β-cyclodextrin, or poly(aspartic acid) (PAS), is presented. The dependence of the thermal behavior of the polymers as
well as their morphological aspect, on the protective colloids used in synthesis was evidenced by polymers characteri-
zation. It is also demonstrated that the swelling capacity is dependent on the protective colloid variant present during the
pHEMA preparation. This behavior induces as well interdependence on the ability to load bioactive compounds onto
the polymeric matrices. The distribution of the indomethacin (INN), as model drug, into the pHEMA network was put
into evidence by near infrared chemical imaging (NIR-CI), a non-destructive technique and with its correspondingly
statistical analysis.
Keywords: Biocompatible Polymers; Polymer Network; β Cyclodextrin; Poly(Aspartic Acid)
1. Introduction
Methacrylic polymers and copolymers are widely used
for various medical and pharmaceutical applications.
Among them poly(2-(hydroxyethyl) methacrylate) (pHE-
MA) is favored for preparing intraocular lenses, and
microbeads for vascular embolization, immobilization of
cells, enzymes or pharmacological drugs. The hydroxye-
thyl pending groups of the polymer ensure high hydro-
philicity, good biocompatibility and the possibility to
prepare pHEMA in the form of a hydrogel [1,2].
As it is well known, the heterogeneous free radical
polymerization process involves the relative solubiliza-
tion of the hydrophobic monomers in water for example
by an oil-in-water emulsifier, followed by the initiation
reaction with either a water insoluble initiator or an oil-
soluble initiator [3]. During polymerization an extremely
large oil-water interfacial area is generated as the particle
nuclei form, which is growing in size with the progress
of the process. Effective stabilizers such as ionic and/or
non-ionic surfactants and protective colloid, which can
be physically adsorbed or chemically incorporated onto
the particle surface, are required to prevent the interac-
tive latex particles from coagulation. Thus, satisfactory
colloidal stability is achieved by the electrostatic stabili-
zation mechanism [4], the steric stabilization mechanism
[5] or both. The formation of stable colloidal particles
during polymerization of 2-hydroxyethyl methacrylate,
as water-soluble monomer but insoluble homopolymer,
requires a proper choice of initiator and/or surfactant.
Thus, stable latex products were produced from 2-hy-
droxyethyl methacrylate, only if hydrophobic initiators
(e.g. AIBN or benzoyl peroxide) in combination with
alkyl sulfate with the alkyl chain length greater than 10
or surface-active initiators (e.g. 2, 20-azobis(N-20-me-
thylpropanoyl-2-amino-alkyl-1)-sulfonate) with the alkyl
chain length greater than eight were used [6].
The preparation of poly(2-hydroxyethyl methacrylate)
latex with adequately high solid content is not easy at all
compared to the hydrogel preparation, since the mono-
mer exhibits an extremely high aqueous solubility and
the latex faces coagulation easily [7]. The polymerization
*Corresponding author.
Member of the European Polysaccharide Network of Excellence (EP-
N
OE), www.epnoe.eu.

Upon the Delivery Properties of a Polymeric System Based on Poly(2-Hydroxyethyl Methacrylate)
Prepared with Protective Colloids
358
of 2-hydroxyethyl methacrylate (HEMA), using a series
of initiators (2,2’-azobisisbutyronitrile, 2,2’-azobis-(2-
amidinopropane) dihydrochloride, 4,4’-azobis(4-cyano-
pentanoic acid) (ACPA), 1,1’-azobis(cyclohexane carbo-
nitrile)) and using either sodium lauryl sulfate (SLS) as
emulsifier or a mixture of SLS and poly(vinyl pyrroli-
done) (PVP) as tensioactive system, has been already
reported [8].
The goal of our investigation was to study the pHEMA
characteristics, especially from the viewpoint of its ca-
pacity of coupling bioactive substances, after preparing
the polymer through radical dispersion polymerization in
the presence of ACPA as initiator and using classic
tensioactive—sodium lauryl sulfate (SLS)—in tandem
with one of the following protective colloids: poly(vinyl
alcohol) (PVA), or β-cyclodextrine (CD) or poly(aspartic
acid) (PAS).
It is known for the beneficial effect of PVA as protec-
tive colloid, which limits the flocculation of the interac-
tive particles, restrains the coalescence between mono-
mer droplets and the polymer particles, and also, improves
generally the performance of the latex characteristics.
CD was also tested in the polymerization processes of
the extremely hydrophobic dodecyl methacrylate or oc-
tadecyl methacrylate to study the role of β cyclodextrine
in the nucleation and growth of particle nuclei and trans-
port of those monomer molecules from monomer drop-
lets to the growing latex particles, as far as CD forms
inclusion with the guest species, and thus, increases the
water solubility of the hydrophobic compounds [9-12].
PAS belonging to the family of synthetic polypeptides
is a typical biocompatible, biodegradable water-soluble
polymer with dispersing activity, and it can be used as
dispersant, antiscalant, or superabsorber, for home deter-
gents, water treatment chemicals, and oil field treatment
additives, for a variety of organic and inorganic solids
and scales dispersal, and in medicines, cosmetics, and
food. It is considered to be a sustainable, environmen-
tally compatible chemical product and its biodegradabil-
ity makes it particularly valuable from the viewpoint of
environmental acceptability and waste disposal [13,14].
Its use as protective colloid will induce the increase of
the absorbent character as well as biocompatibility and
biodegradability for the system.
The thermal stability of the synthesized polymers was
evaluated and the polymer network morphology was
examined by SEM investigations. The new polymeric
structures were also tested from the viewpoint of their
capacity to be loaded with a bioactive compound. Thus,
the swelling degree of the pHEMA was determined re-
lated to the pH and at two temperature values (at room
and respectively physiological temperature). The ability
of pHEMA to be loaded with indomethacin as model
drug, and the release of the bioactive compound from the
polymeric network, were also evaluated.
2. Experimental Part
2.1. Materials
2-Hydroxyethyl Methacrylate (HEMA) (from Fluka,
purity >96%) was purified by passing through an
inhibitor removal column. The tensioactive substance,
sodium lauryl sulfate (SDS) (C12H25O4SNa), was pur-
chased from Sigma-Aldrich. Poly(aspartic acid) (PAS)
(Mw = 15000) was synthesized in our laboratory as it was
detailed in the reference [14] (hydrolysis of polysuc-
cinimide). β-cyclodextrine (CD) (Mw = 1135, purum,
≥99%), from Sigma-Aldrich, and poly(vinyl alcohol)
(PVA), from Oriental Chemical Industry (Mw = 120000
Da, hydrolysis degree = 88), were used without further
purification. The radical initiator 4, 4’-azobis(cyanopen-
tanoic acid) (ACPA) (from Fluka, 98%) was used also
without further purification. The water used in all experi-
ments was purified using an Ultra Clear TWF UV
System.
2.2. Polymer Compounds Preparation
2.2.1. Po lymeri zation Proc ess
The radical polymerization processes were conducted
under nitrogen atmosphere, in a temperature bath at 80˚C,
with a mechanical stirring rate of 180 rpm. The poly-
merization formulations are presented in Table 1.
After synthesis the polymeric particles were precipi-
tated three times with methanol and finally freeze-dried
by lyophilization for 24 h.
2.2.2. Po lymer Matr ices Loading with Indomethacin
In order to evaluate the capacity of the networks of the
synthesized polymers to be loaded with drug, and to
determine as well the release behavior, Indomethacin
(INN), as a model drug, was loaded into the pHEMAPVA,
pHEMAPAS, and respectively pHEMACD polymeric ma-
Table 1. Polymerization recipes (substances are given in
grams).
System
Component PHEMAPAS PHEMAPVA PHEMACD
HEMA 8 8 8
ACPA (initiator)0.05 0.05 0.05
SLS (tensioactive)0.267 0.267 0.267
PAS 0.267 0 0
PVA 0 0.267 0
CD 0 0 0.267
Water 100 100 100

Upon the Delivery Properties of a Polymeric System Based on Poly(2-Hydroxyethyl Methacrylate)
Prepared with Protective Colloids
359
trices. The drug powder was dissolved in ethanol/phos-
phate buffer solution (pH = 7.2) to obtain a concentration
of c = 1.9005 × 10−5 mol/ml. Then the polymers were
immersed in this solution and let to swell till equilibrium
(the ratio INN/copolymer was about 1/10 wt%). The
swollen drug-loaded samples were then dried at ambient
temperature for several days until the prepared particles
had constant mass. The particles were then freeze-dried
to obtain the resultant drug-loaded network to use them
in the release experiments.
2.3. Polymers and Polymer Composites
Characterization
2.3.1. Polymers FTIR Spectra
Polymers FTIR spectra were recorded on a Vertex
Brucker Spectrometer in an absorption mode ranging
from 4000 cm−1 to 400 cm−1 (Figure 1). The polymeric
samples were grounded with potassium bromide (KBr)
powder and compressed into a disc to analysis. Spectra
were acquired at 4 cm−1 resolution as an average of 64
scans. The registered spectra confirms pHEMA achieve-
ment small recorded differences being attributed on the
used protective colloids. Thus, v (O-H) stretching vibra-
tion in HEMA is observed in the 3400 - 3500 cm−1 range
as broad absorptions, and the strong band at ~2950 cm−1
and ~2970 cm−1 is attributed to the v (C-H). Another
strong band at ~1730 cm−1 is assigned to v (C=O) group,
at ~2940 cm−1 to v (C-H) stretching of -CH3, and also at
~1270 cm−1 to v (C-O) stretching vibration.
2.3.2. Thermal Analysis
The thermal characterization of the polymers was
performed on a Jupiter STA 449 F1 (Netzsch) simultane-
ous TGA/DSC device calibrated with high purity che-
micals, respectively with standard indium, tin, zinc and
aluminum. The samples were maintained in a controlled
Figure 1. FTIR spectra of the polymers synthesized accord-
ing to recipes from Table 1.
humidity atmosphere provided by the presence of CaCl2
inorganic salt. 7.5 - 8 mg samples were heated in open
Al2O3 crucible under 50 ml·min−1 nitrogen flow rate. The
runs were performed in the dynamic mode from room
temperature up to 600˚C with a heating rate of
10˚C·min −1.
2.3.3. SEM Studies
were performed on samples fixed by means of colloidal
copper supports. The samples were covered by sputtering
with a thin layer of gold (EMITECH K 550×). The
coated surface was examined by using an Environmental
Scanning Electron Microscope (ESEM) type Quanta 200
operating at 30 kV with secondary electrons in high
vacuum mode.
2.3.4. Swelling Studies
Dynamic swelling measurements were performed in
buffer solutions at two pH values, 2.4 and 7.4, and each
at two temperatures: 24˚C and respectively 37˚C. The
amount of the adsorbed solution was monitored gravi-
metrically: the swollen particles were regularly extracted
from the swelling medium, wetted on the surface,
weighed and placed again in the same bath. The mea-
surements were continued until the constant weight was
reached for each studied sample. The degree of swelling
(Q) was calculated as follows:




00
Q, %MtMM100%

 

(1)
where M(t) is the weight of the swollen particles at time t
and M0 is the weight of the sample before swelling. All
the swelling experiments were performed in triplicate.
2.4. Loading Evaluation
The evaluation of the drug distribution in the polymeric
matrix was made using near infrared chemical imaging
(NIR-CI) technique and the correspondingly statistical
analysis. The original image data sets of samples were
collected by a completely integrated Chemical Imaging
Workstation from SPECIM Spectral Imaging Ltd (Fin-
land). Acquisition of spectral lines was made on the
wavelength range starting from 1100 nm to 2500 nm.
Images with 320 × 640 pixels were recorded with a
spectral camera (NIR model based on an ImSpector
N17E imaging spectrograph).
Data pre-processing, preliminary visualization and the
proper characterization were performed using Evince
program (UmBio, Sweden), a software package designed
for visualization and analysis of hyper spectral image
cubes. The contrast in the chemical images is compared
by methods using the intensity of a single wavelength,
the peak-height ratio of two wavelengths, the correlation
coefficient with a reference spectrum and the principal

Upon the Delivery Properties of a Polymeric System Based on Poly(2-Hydroxyethyl Methacrylate)
Prepared with Protective Colloids
360
component analysis (PCA). The correlation coefficient
method was also compared with the partial least squares
(PLS-DA) regression for further homogeneity investi-
gations.
2.4.1. In Vitro Contr olled Re lease of Indomethacin
from Polymer Matrices
Studies concerning the INN release have been carried out
in vitro using the USP padle (apparatus II) method with a
dissolution tester (ERWEKA Dissolution Testers) at 50
rpm, pH = 7.4 and 37˚C temperature. The dried samples
(approx. 200 mg particles of each formulation) loaded
with INN were immersed in the phosfate buffer solution.
700 mL dissolution medium used for the determination
contains potassium dihydrogen phosphate (KH2PO4, 0.2
M), monohydrogen phosphate (K2HPO4, 0.2 M) and
water. Time was recorded as soon as the particles were
put into the dissolution vessels. For the drug release
analysis 2 ml sample solution were withdrawn from
vessel at appropriate time intervals (1, 3, 5, 10, 15, 20, 25,
30, 40, 60, 90, 120, 150, 180, 240, 360 and after that at
each 120 minutes until 1600 minutes). 2 ml of fresh
phosphate buffer solution, heated to 37˚C, was imme-
diately added to the dissolution medium for compensat-
ing the sampling. The dissolution study was carried out for
three samples from each formulation. The amount of the
released INN was determined spectrophotometrically
(Perkin Elmer spectrophotometer) at 319 nm.
3. Results and Discussions
3.1. Thermal Analysis
The evolution of the thermal decomposition of the poly-
mers synthesised with different protective colloids is
illustrated in Figure 2. The registered differences are
attributed to the influence of the protective colloids upon
thermal characteristics of the polymers synthesised in
their presence. For pHEMACD two stages of decom-
position were registered between 167˚C to 223˚C and
respectively from 321˚C to 421˚C. The weight loss
registered at the beginning of the decomposition process
is attributed to the loss of the water of inclusion inside
the cavity of CD, phenomena also reported by other
authors [15]. The pHEMAPAS and pHEMAPVA samples
have as well two stages of decomposition, but the first
one is not as evident as in case of pHEMACD samples.
The specific parameters corresponding to the main de-
composition step, the second one, of the studied samples
are presented in Table 2. These data confirm the in-
fluence of the protective colloid on the stability of the
pHEMA.
The thermal stability of polymers can be ordered as
follows: PHEMACD < PHEMAPAS < PHEMAPVA. The
Figure 2. TG and DTG curves characterizing the thermal
decomposition behaviour of the synthesized polyme r s.
Table 2. Thermal characteristic s of the synthesized samples.
The main decomposition step
Polymers Tonset, ˚C Tmax, ˚C Tend set, ˚C
ΔW, %
PHEMAPVA 252 402 472 98.1
PHEMAPAS 232 400 465 98.4
PHEMACD 228 360 465 98.4
Tonset: Temperature of the beginning decomposition; Tmax: Temperature at
maximum decomposition rate; Tendset: Temperature at the end of decom-
position process; ΔW: Total weight loss percentage at the end steps.
differences registered in the thermal stability are con-
sidered to be in relation with surfactants structure, prac-
tically with the number of physical bonds, especially
hydrogen bonds, performed between pHEMA and the
tested protective colloids. In this context, the molecular
mass of the protective colloids is as well an important
factor in generating intermolecular interactions with the
chains of the new synthesised polymer compound. Thus,
the best thermal stability of the pHEMAPAV is in agree-
ment with the PAV molecular weight of about 70,000,
being followed by pHEMAPAS with MPAS ~15,000 and
finally by pHEMACD.
3.2. SEM Studies
Information concerning the morphology of the studied
polymeric samples are obtained by SEM studies and are
presented in Figures 3(a)-(c). There are clear differences
between the polymers morphology stabilized by PVA
(Figure 3(a)) or CD or PAS as protective colloid (Fig-
ures 2(b) and (c)). Thus, an aspect rather porous presents
pHEMAPVA, while pHEMACD and pHEMAPAS exhibit a
more uniform aspect as self-assembled honeycomb nano-
fibers (pHEMAPAS) or lacing nanofibers (pHEMACD).
Also, the pore size decreases from about 17 µm for
PHEMAPVA to ~3 µm for PHEMA
CD and ~2 µm for

Upon the Delivery Properties of a Polymeric System Based on Poly(2-Hydroxyethyl Methacrylate)
Prepared with Protective Colloids
361
(a) (b)
(c)
Figure 3. Comparison between PHEMAPVA (a), PHEMAPAS
(b), PHEMACD polymers morphology (SEM micrographs at
2000×).
PHEMAPAS. The cause for the size modification of the
network meshes was attributed to the molecular weights
of the used protective colloids and to their specific
intermolecular interactions with the pHEMA chains [6].
3.3. The Swelling Behavior
It is well known the hydrophobic character of pHEMA.
At the same time, when the polymer is subjected to water
it swells due to the hydrophilic pendant groups. It is
expected as the protective colloid type, used for the
PHEMA synthesis, to influence as well the capacity of
water absorption.
The swelling kinetic of the polymeric particles related
on the swelling conditions, respectively at two pH values
(2.4 and 7.2) and correspondingly at two temperatures
(24˚C and 37˚C), is illustrated in Figure 4. The highest
swelling capacity was recorded for pHEMAPAS sample,
followed by PHEMACD, while the lowest swelling be-
havior corresponds to PHEMAPVA variant, no matter the
swelling conditions are (Table 3). The swelling behavior
of pHEMAPAS is justified by the superabsorbent and
polyelectrolyte character of PAS, the intervened electro-
static forces contributing to the improvement of the poly-
mer swelling capacity. Regarding the pHEMAPVA swell-
ing behavior it is justified by the hydrogen bonds come
along PAV and pHEMA polymer chains (Figure 5) into
the detriment of bonds between pHEMA and solvent.
Figure 4. Swelling behavior of the PHEMA polymers re-
lated on the pH and temper variation: (a) pH = 2.4, t = 24˚C;
(b) pH = 2.4, t = 37˚C; (c) pH = 7.2, t = 24˚C; (d) pH = 7.2, t
= (caption: PHEMAPAS (1), PHEMACD (2) AND PHEMAPVA
(3)).
Table 3. The swelling degree related on the conditions of
determination.
Equilibrium swelling degree, %
Samples pH = 2.4;
t = 24˚C
pH = 2.4;
t = 37˚C
pH = 7.2;
t = 24˚C
pH = 7.2;
t = 37˚C
PHEMAPAV 117 155 45 52
PHEMAPAS 300 226 173 145
PHEMACD 184 155 137 124
The swelling behavior of pHEMAPVA is improved in
acidic medium both at room temperature and at 37˚C.
The most sensitive sample is pHEMAPAS, its behavior at
swelling being slightly decreased with the increase of the
temperature in acid and neutral medium. Thus, swelling
is two times smaller at 37˚C comparing with the room
temperature. At the same time, pHEMACD is practically
not sensitive either to pH or temperature, in the studied
intervals.
In the context of the obtained results the higher
swelling behaviour registered at the acidic pH was attri-
buted to the decrease of the osmotic pressure. Between
the carboxylic groups of PAS and the ionized groups of
medium appear the repulsion forces which reduce the
osmotic pressure allowing the solvent molecules to pene-
trate the network meshes and thus increasing the poly-
mers swelling capacity.

Upon the Delivery Properties of a Polymeric System Based on Poly(2-Hydroxyethyl Methacrylate)
Prepared with Protective Colloids
362
coupling bioactive compounds and to control the drug
release in biological medium [16]. Near-infrared che-
mical imaging (NIR-CI) was used as non-destructive me-
thod, to evaluate the distribution of indomethacin (INN)
in the synthesized polymeric samples. The method re-
presents a challenging combination for visualizing the
spatial distribution and homogeneity of drug accom-
panied with chemometrics tools and image-processing
method [17]. Evaluation of drug loading degree and
indomethacin/polymeric system homogeneity was esti-
mated by PLS-DA (Partial least squares—Discriminant
Analysis). Figure 6 illustrates the score images derived
from the indomethacin component class. In the score
images, the pixels with higher and lower score values are
indicated by light gray and dark code colors, respectively.
For the polymeric network loaded with indomethacin, the
code color in the most region of the score images is gray,
the intermediate color between light gray (the cod color
of the polymers) and dark gray colors (the code color of
indomethacin). The predominantly gray score images
evidences the homogeneity distribution of drug in the
synthesized polymeric matrices. Also, the code color
attests the qualitative differences between the polymeric
networks variants loaded with drug.
3.5. In Vitro Controlled Release of Indomethacin
Figure 5. Illustration of the chemical structures involved in
the polymerization processes. As it is well known the physicochemical properties of the
polymeric network as well as the drug loading method
determine the further release mechanism of the bioactive
product [18]. The release profiles of INN from the poly-
meric loaded samples, in physiological buffer solution
(pH = 7.4, and 37˚C) are presented in Figure 7. For all
polymer/INN complex formulations (Figure 8), the sus-
3.4. The Evaluation of the Drug Homogeneity
into Polymeric Matrices
PAS, CD and PVA were used during pHEMA synthesis
not only for their character as protective colloids but as
well to improve the ability of the homopolymer for
(a) (b) (c)
Figure 6. Score images of the indomethacin inclusion into the polymeric networks PHEMAPVA (a); PHEMAPAS (b); and
PHEMACD (c).

Upon the Delivery Properties of a Polymeric System Based on Poly(2-Hydroxyethyl Methacrylate)
Prepared with Protective Colloids
363
Figure 7. The INN releasing profile from the polymeric ma-
trices.
Figure 8. Illustration of the poly(2-hydroxyethylmethacry-
late)/INN complex formation.
tained release behavior was observed. During the first
300 minutes, all samples present a faster release of INN
(burst effect). The burst release is owing to the presence
of the drug at the surface of the polymeric particles. After
this interval of time the release kinetic is slowed, be-
havior which is attributed to the links intervened between
drug and the protective colloid. Thus, pHEMAPAV sam-
ples present the slowest release rates, while the pHEMACD
and pHEMAPAS samples are releasing much faster the
drug. This aspect is sustained as well by the largest pores
of pHEMAPAV (Figure 3) which can keep and maintain
the drug inside the network, and not only at surface as in
case of pHEMACD and pHEMAPAS samples. And more
then that PHEMAPAV have the lowest swelling degree
which may explain as well this slowest release. The
entire quantity of loaded indomethacin was released from
pHEMAPAS and pHEMACD samples during the time of
observation, while just 79% of drug was released from
PHEMAPAV.
4. Conclusion
The study evidences the possibility of using poly(vinyl
alcohol), β cyclodextrin or poly(aspartic acid) as pro-
tective colloids for the preparation of poly(2-hydroxye-
thyl methacrylate) through radical processes of poly-
merization. FTIR spectra confirm the synthesis of pHEMA
as well as the presence of PVA, CD or PAS. The in-
fluence of the protective colloids was put into evidence
by the different behaviors of the synthesized homopoly-
mers during thermal decomposition. Thus, polymers can
be ranked in the following order of their thermal stability:
pHEMAPAV > pHEMAPAS > pHEMACD, behaviour justi-
fied by the increased numbers of hydrogen bonds inter-
vened between the molecular chains and related to the
molecular weights of the protective colloids. The shape
and morphology of the pHEMA structure were found to
be the effective result of the used protective colloids.
Therefore, complementary SEM observations evidenced
the role played by the surfactants: the particles are changed
from irregular aggregates in the case of using PVA, to
well-defined filaments in the case of PAS, or tracery when
CD is used. The swelling capacity is also depending on
the protective colloids variant used during pHEMA syn-
thesis. Thus, the swelling degree of the polymers is
growing in the following order: pHEMAPAV < pHEMACD
< pHEMAPAS. The behavior was justified by the core/
shell structure of the PHEMA micelles with 1) the hydro-
phobic segment of PAV shell oriented on the exterior of
the micelle surface, as well as 2) the superabsorber
character of PAS and 3) hydrophilic nature of CD. The
synthesized pHEMA particles were used as matrix for
coupling indomethacin as model drug. The NIR-CI me-

Upon the Delivery Properties of a Polymeric System Based on Poly(2-Hydroxyethyl Methacrylate)
Prepared with Protective Colloids
364
thod confirmed the homogeneous distribution of the INN
in the polymeric network. The INN release was also
dependent on the protective colloids variant used for the
pHEMA preparation. Thus, pHEMAPAS as well as
pHEMACD matrices release almost the entire quantity of
the coupled INN. During the same period of releasing
time, pHEMAPAV retains amounts of drug, behaviour jus-
tified by the morphology of the particles, higher mole-
cular weight of PAV, and the hydrophobic surface of the
core/shell pHEMA particles.
5. Acknowledgements
This work was financially supported by the grant of the
Romanian National Authority for Scientific Research,
CNCS-UEFISCDI, project number PN-II-211/2012 “In-
terdisciplinary research on multifunctional hybrid parti-
cles for bio-requirements”.
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