SPECTRAL ANALYSIS OF IN MONOLITHIC

1
SPECTRAL ANALYSIS OF IN MONOLITHIC

• Katarzyna Polska
• Faculty of Chemistry, Maria
• Pl. M.C. Sklodowskiej 2,

2
CON A H2P INTERACTIONSSILICA GELS

• and Stanislaw Radzki
• Curie-Sklodowska University
• 20-031 Lublin, Poland

3
PURPOSE
Two water-soluble cationic porphyrins
tetrakis4-(trimethylammonio) phenyl porphyrin
(H2TTMePP), tetrakis(1-methyl-4-pyridyl)
porphyrin (H2TMePyP) and their complexes with
lectin concanavalin A (Con A) have been
encapsulated in monolithic silica gels (obtained
by polycondensation of tetraethoxysilane) and
studied using absorption and fluorescence
spectroscopic techniques. The sugar-binding and
haemagglutinating properties of lectins are used
for preparative and analytical purposes in
chemistry, cell biology and immunology. Some
lectins have ability to interact preferentially
with transformed cells and they have been
suggested for use as carriers in targeted
delivery to tumour cells. Finding lectins with
high affinity for porphyrins can open up new
possibilities, such complexes can be employed in
photodyna-mic therapy (PDT) or as a built-in
sensors. Studies of lectin -porphyrin
interactions are also important from the point of
view of the effect of lectins on
porphyrin-containing biomolecules in organisms.
4
CONCANAVALIN A
is the lectin of the jack bean (Canavalia
Ensiformis), its conformation depends on pH,
beetwen pH 4 and 5 it exists as a dimer and at pH
above 7 it is predominantly tetrameric

a
b
Fig. 1. Structure of Concanavalin A protomer (a)
and 11 H2TTMePP-Con A complex (b).
5
CATIONIC PORPHYRINS
H2TTMePP H2TMePyP
5,10,15,20-tetrakis 4-trimethyl
ammonio)phenylporphyrin
5,10,15,20-tetrakis4-(1-methyl- 4-pyridyl)-21H,2
3H-porphyrin
6
SOL-GEL PREPARATION


7
Fig. 3. Monoliths of silica gel immobilized with
H2TTMePP after 7 days, 1 month and 6 months of
drying.
8

Fig. 4. Silica gel monoliths immobilized with
H2TTMePP (A), Con A (B) and H2TTMePP / Con A
complex (AB) after 6 months of drying.
9
SOLUTION
SOL-GEL
Fig. 2. Absorption and emission spectra of
H2TTMePP and H2TTMePP / Con A systems
measured in tris solution (pH 8.7) and in
monolithic silica gels.
10
CONCLUSIONS
Biologically important compounds encapsulated in
silica gels have many unique features, as good
mechanical durability, high resistance to
chemical and biological degradation and, what is
the most important, they retain their
spectroscopic properties and biological activity.
The advantages of biologicals captured in
sol-gels might give them applications as
biosensors, diagnostic devices and
catalysts. Monolithic silica gels immobilized
with Con A H2P systems were obtained by the
sol-gel polymerization of TEOS. Those monoliths
were characterized by UV-Vis absorption and
fluorescence methods. The results suggest that
there is complexation between Con A and cationic
porphyrins. The binding with Con A was found to
increase the porphyrin fluorescence intensity and
the red-shift in the absorption and emission
maxima have been observed.