We present some selected results indic
ating the fe
asibility of prep
aring ther
apeutic finished ophth
almic
articles, n
amely commerci
ally
av
ail
able soft cont
act lenses, using
a supercritic
al solvent impregn
ation (SSI) technique. Sever
al commerci
al soft cont
act lenses were tested
and,
among these, four lenses were selected for more complete studies:
Nelfilcon A (FocusD
ailies
ae;, CIBA Vision), Om
afilcon A (Procle
ar
ae; Comp
atibles, CooperVision), Meth
afilcon A (Frequency
ae; 55, CooperVision)
and Hil
afilcon B (SofLens
ae; 59 Comfort, B
ausch & Lomb). Supercritic
al c
arbon dioxide (scCO
2) w
as the chosen supercritic
al fluid
and two ophth
almic drugs were tested: flurbiprofen (
a NSAID, hydrophobic)
and timolol m
ale
ate (
an
anti-gl
aucom
a drug, hydrophilic). The effects of oper
ation
al pressure, of impregn
ation dur
ation
and of the
addition of
a cosolvent (eth
anol) were studied on the over
all drug lo
ading yields. Depending on the experiment, we employed pressures from 9 up to 16
a0;MP
a and impregn
ation times from 30 up to 180
a0;min. Temper
ature w
as kept const
ant
and equ
al to 313
a0;K. The employed depressuriz
ation r
ates were kept low
and between 0.1
and 0.2
a0;MP
a/min.
Results are discussed in terms of the employed operational conditions and taking in consideration all the possible interactions between supercritical fluids, drugs, cosolvents and the polymers which compose the employed hydrogel contact lenses. In vitro drug release experiments were carried out in order to evaluate the resulting drug release profiles. Obtained results were also compared with drug-loaded contact lenses obtained by conventional drug “soaking” in aqueous solutions. Results also proved that SSI can be considered as a viable, efficient and safe alternative for the impregnation of drugs, including those of hydrophobic character or presenting low aqueous solubility, into commercial soft contact lenses. SSI proved to be a “tunable” process since the variation of the employed operational conditions indicated that it is possible to control the amount of impregnated drug. In the end, the ophthalmic articles were recovered undamaged and without the presence of harmful solvent residues. This method also permits to process already prepared commercial contact lenses, without interfering with their manufacture methods and, after processing, store them for future use.