PROCEEDINGS OF THE 7 INTERNATIONAL ... - Fizika
PROCEEDINGS OF THE 7 INTERNATIONAL ... - Fizika
PROCEEDINGS OF THE 7 INTERNATIONAL ... - Fizika
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M. Franckevicius / Medical Physics in the Baltic States 7 (2009) 34 - 38<br />
applications [12, 14]. Suppose dendrimers and silver<br />
nanoparticles can compose fluorescent, biocompatible<br />
and highly photostable dendrimer nanocomposite that<br />
may be used for cell labelling [15].<br />
In this work optical properties of liquid crystalline (LC)<br />
poly(propylene-imine) (PPI) dendrimers of fourth<br />
generation with encapsulated silver nanoparticles were<br />
investigated for medical applications.<br />
2. Experiment<br />
Liquid crystalline PPI dendrimer of fourth generation<br />
with –OC5H11 terminal mesogenics units and Ag silver<br />
nanoparticles were used. Synthesis of liquid crystalline<br />
PPI dendrimers were described in detail in ref. [16] by<br />
condensation of 4-(40-ethoxybenzoyloxy)<br />
salicylaldehyde with the terminal amino groups of the G<br />
= 4 of poly(propylene imine) (PPI-(NH2)32) using a<br />
method previously described [17]. For small silver<br />
nanoparticles preparation briefly 200 mL 0.1 mM<br />
AgNO3 solution was reduced with 2 mL 0.5 mM NaBH4<br />
in the presence of tri-sodium citrate (0.3 mM) under<br />
gentle stirring. Immediately after injection of the<br />
reducing agent, 2 mL of a 5 wt% aqueous solution of<br />
PVP was added [18].<br />
Incorporation of silver nanoparticles in dendrimers was<br />
involved by using concentrations of the same molar<br />
ratios of both materials in chloroform solution. Firstly<br />
liquid crystalline dendrimers were dissolved in<br />
chlorophorm solution. Aqueous solution of silver<br />
nanoparticles was evaporated and then nanoparticles<br />
were mixed with dendrimer chloroform solution.<br />
Encapsulated LC PPI dendrimers with silver<br />
nanoparticles were characterized by optical absorption<br />
spectroscopy. Optical spectra were recorded by doublebeam<br />
spectrophotometer Perkin Elmer Lambda 19.<br />
More information of purity of dendrimers was described<br />
in ref. [16]. Structural and optical characteristics of used<br />
silver nanoparticles were described by Bastys et all.<br />
[18].<br />
3. Results<br />
Structure of liquid crystalline PPI dendrimers of fourth<br />
generation is presented in Fig. 1. Also silver<br />
nanoparticles a few nanometer in size in the liquid<br />
crystalline PPI dendrimer were encapsulated.<br />
35<br />
Fig.1. Fourth-generation PPI-[C2]32 liquid crystalline<br />
dendrimer<br />
Figure 2 shows modeled liquid crystalline PPI<br />
dendrimer like-structure consisting of four terminal<br />
flexible chains on periphery were demonstrating empty<br />
spaces inside branching units. In this empty spaces<br />
could be hosted silver nanoparticles. Calculations of the<br />
same dendrimers structures composed of six and eight<br />
terminal chains show occupation of empty spaces are 1<br />
to 3nm 2 in square.<br />
Fig.2. The calculated periphery of the PPI dendrimer<br />
structures composed of 4 terminal flexible chains displaying<br />
empty spaces between chains<br />
These empty spaces can be used as containers or holders<br />
for silver nanoparticles or drugs. According calculations<br />
size of encapsulated silver nanoparticles in to dendrimer<br />
couldn’t be bigger than these calculated sizes.<br />
Figure 3 shows transmission electron microscope<br />
images (TEM) of silver nanoparticles. Background of<br />
the image shows initial nanoparticles, whose are used<br />
for incorporation into liquid crystalline PPI dendrimer.