Letno poročilo 2005

Laboratorij za elektrokemijo materialov
Laboratory for Materials Electrochemistry
aktivnega materiala. S tem bi pridobili
najbolj{i znani aktivni material za pozitivne
elektrode v litijevih baterijah.
- Stabilizacija amorfnih zdravil z vgradnjo
u~inkovine v mikroporozne anorganske gele
Priprava zdravilne u~inkovine v amorfni obliki
je pogosto za`elena, saj je v tem primeru
njeno raztapljanje v organizmu praviloma
hitrej{e. [e pomembneje je, da amorfne oblike
zdravil niso patentno za{~itene. Najve~ji
problem amorfnih oblik je ta, da niso stabilne
in prehitro kristalizirajo. Tipi~en primer
takega zdravila je nifedipin, ki smo ga v {tudiji
uporabili kot modelsko u~inkovino. Na osnovi
teoreti~nih izra~unov smo predpostavili,
da bi lahko amorfno obliko nifedipina stabilizirali
v porozni strukturi anorganskega
gela. Ra~uni so namre~ pokazali, da v porah,
ki so manj{e od nekaj nanometrov, kristalizacija
nifedipina zaradi prostoskih omejitev ne
more pote~i, zato se lahko izlo~i le v amorfni
obliki. Ker bi bil nifedipin v mikroporah hkrati
izoliran od okolice, bi bilo povsem mo`no,
da bi s tem zelo upo~asnili njegovo degradacijo.
Poskusi so popolnoma potrdili
teoreti~ne predpostavke. ^e smo namre~
nifedipin vgradili v silikatno matrico s
povpre~nimi dimenzijami por okoli 2,5 nm,
je nastala izklju~no amorfna oblika te
u~inkovine, stabilnost pa se je podalj{ala od
tipi~no nekaj dni na nekaj mesecev (morda
{e ve~ - preskus stabilnosti je {e vedno v teku).
SLIKA 1:
Struktura in elektrokemijska karakteristika novega
baterijskega materiala: Li 2 MnSiO 4
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- Stabilization of amorphous drugs by incorporation
of active substance into microporous
inorganic gels
One of the advantages of amorphous drugs
over their crystalline forms could be a faster
dissolution in organism. For developers and
pharmaceutic companies the amorhous
forms of drugs are especially attractive as they
are not patented. The most serious drawback
of amorphous drugs is their instability leading
to rapid and uncontrolled crystallization.
A typical example is nifedipine which was
used as a model substance in the present
study. Based on theoretical calculations, we
assumed that amorphous nifedipine could be
stabilized within the porous structure of inorganic
gels. Namely, as such pores are usually
in the nanometre range, crystallization
of nifedipine should not occur neither from
liquid nor from the solid state - due to spatial
constraint. Being embedded within the
solid matrix and thus isolated from the suroundings,
the drug, although amorphous,
should be considerably stabilized. The experiments
confirmed the predictions. When solidification
of nifedipine took place within
pores with an average size of ca. 2.5 nm, the
resulting solid was completely amorhous and
remained such over a period of several
months instead of several days which is a typical
stability period of the free amorphous
nifedipine.
FIGURE 1:
Structure and electrochemical characteristics of a new
battery material: Li 2 MnSiO 4