276
poor solubility and hydrophobic nature, it causes problems in its
efficient clinical usage. For instance in the ocular applications of
DEX, low residence time of formulations in the eye results in only
about 5% drug penetration and thus a need for frequent administration arises. A NS carrier-based system may serve to increase the
residence time in the eye and release the drug in a controlled manner, thereby also reducing the associated side effects [113]. Three
NSs were prepared by cross-linking β-CD and diphenyl carbonate
(DFC) at different β-CD:DFC molar ratios (1:2, 1:4, and 1:8) and
loading DEX through incubation method followed by lyophilization of the drug-loaded NSs.
NS formulations were checked for safety in excised bovine corneas. For a formulation to be suitable for ocular delivery it must
have uniform particle size (Fig. 9). The most desirable formulation
NS (1:4) showed a denser core as compared to other types. This
could pave a platform for improving the permeability of various
other drugs for ocular ailments, combining encapsulation abilities,
safety, and colloidal properties together with the adhesive effect to
obtain superior dosage forms [114].
NSs obtained by cross-linking with pyromellitic dianhydride can
swell to a very great extent and form a hydrated gel. β-Pyromellitic
NS with high degree of swelling was exploited to form gels or
cream-gel for diclofenac (DIC) delivery to the skin. In addition,
the NS was used to solubilize and stabilize the photosensitizing
agent benzoporphyrin derivative monoacid ring A (BPDMA) and
the light-sensitive all-trans retinoic acid (atRA).
The effect of the pyromellitic NS concentration on the viscosity of the corresponding water dispersions was preliminarily
assessed. At increasing NS concentrations, viscosity increased up to
1200 cps at 2% NS concentration and then progressively decreased.
As viscosity obtained was not high enough for a gel suitable for
application to the skin, the NS gel was reinforced with a 1%
Carbopol 940 (CB). DIC was incorporated in the gels by dissolution in water. pH of the gels was adjusted at 7.0 with triethanolamine. Stability of the drug in the formulations was evaluated by
thermal aging and cycle test. DIC transport through porcine ear
skin (selected on the basis of its demonstrated similarity with
human skin) was later assessed on Franz-type diffusion cell area of
0.785 cm
2
. Extraction technique was validated by placing known
amounts of DIC in contact with tape, epidermis, and derma, and
the drug has been extracted. A recovery yield higher than 98% was
obtained. After 24 h, the permeation experiment showed that the
amount of DIC found in the stratum corneum and epidermis was
the highest for the NS–CB gel as compared with the other formulations. As a result, the NS showed the ability to modulate drug
transport through the skin in addition to the ability to improve
2.18 Cyclodextrin
Nanosponges
with Photosensitizing/
Photooxidation Agents
Maria Tannous et al.
poor solubility and hydrophobic nature, it causes problems in its
efficient clinical usage. For instance in the ocular applications of
DEX, low residence time of formulations in the eye results in only
about 5% drug penetration and thus a need for frequent administration arises. A NS carrier-based system may serve to increase the
residence time in the eye and release the drug in a controlled manner, thereby also reducing the associated side effects [113]. Three
NSs were prepared by cross-linking β-CD and diphenyl carbonate
(DFC) at different β-CD:DFC molar ratios (1:2, 1:4, and 1:8) and
loading DEX through incubation method followed by lyophilization of the drug-loaded NSs.
NS formulations were checked for safety in excised bovine corneas. For a formulation to be suitable for ocular delivery it must
have uniform particle size (Fig. 9). The most desirable formulation
NS (1:4) showed a denser core as compared to other types. This
could pave a platform for improving the permeability of various
other drugs for ocular ailments, combining encapsulation abilities,
safety, and colloidal properties together with the adhesive effect to
obtain superior dosage forms [114].
NSs obtained by cross-linking with pyromellitic dianhydride can
swell to a very great extent and form a hydrated gel. β-Pyromellitic
NS with high degree of swelling was exploited to form gels or
cream-gel for diclofenac (DIC) delivery to the skin. In addition,
the NS was used to solubilize and stabilize the photosensitizing
agent benzoporphyrin derivative monoacid ring A (BPDMA) and
the light-sensitive all-trans retinoic acid (atRA).
The effect of the pyromellitic NS concentration on the viscosity of the corresponding water dispersions was preliminarily
assessed. At increasing NS concentrations, viscosity increased up to
1200 cps at 2% NS concentration and then progressively decreased.
As viscosity obtained was not high enough for a gel suitable for
application to the skin, the NS gel was reinforced with a 1%
Carbopol 940 (CB). DIC was incorporated in the gels by dissolution in water. pH of the gels was adjusted at 7.0 with triethanolamine. Stability of the drug in the formulations was evaluated by
thermal aging and cycle test. DIC transport through porcine ear
skin (selected on the basis of its demonstrated similarity with
human skin) was later assessed on Franz-type diffusion cell area of
0.785 cm
2
. Extraction technique was validated by placing known
amounts of DIC in contact with tape, epidermis, and derma, and
the drug has been extracted. A recovery yield higher than 98% was
obtained. After 24 h, the permeation experiment showed that the
amount of DIC found in the stratum corneum and epidermis was
the highest for the NS–CB gel as compared with the other formulations. As a result, the NS showed the ability to modulate drug
transport through the skin in addition to the ability to improve
2.18 Cyclodextrin
Nanosponges
with Photosensitizing/
Photooxidation Agents
Maria Tannous et al.