Initial studies using aliphatic beta-nitro alcohols for therapeutic corneal cross-linking.
OBJECTIVE
Corneal collagen cross-linking through UVA-riboflavin photochemistry (UVAR) has been shown to be an effective treatment for keratoconus and related keratectasias. In recent studies using sclera, the authors observed that short-chain aliphatic beta-nitro alcohols can cross-link collagenous tissue under physiologic conditions. Thus, this study was undertaken to evaluate these agents as potential pharmacologic alternatives to UVAR.


METHODS
Porcine corneal strips (8 x 4 mm) and corneoscleral complexes were cross-linked using 1 to 100 mM 2-nitroethanol (2ne), 2-nitro-1-propanol (2nprop), and 3-nitro-2-pentanol (3n2pent) at pH 7.4, 34 degrees C. Cross-linking by UVAR was carried out for comparison. Thermal shrinkage temperature analysis was used to evaluate cross-linking effects, and changes in corneal light transmission were determined with a fiber-optic spectrophotometer.


RESULTS
At 10 and 100 mM for 96 hours, initial shrinkage temperature (T(i)) was shifted by 3.3 degrees C (P < 0.001) and 9.8 degrees C (P < 0.001) for 2ne, 2.9 degrees C (P = 0.008) and 4.9 degrees C (P < 0.001) for 2nprop, and 3.8 degrees C (P = 0.003) and 4.9 degrees C (P < 0.001) for 3n2pent. Reacting at 1 mM through daily exchange of fluid over 7 days shifted T(i) by 3.8 degrees C (P < 0.001), 4.4 degrees C (P = 0.002), and 3.2 degrees C (P = 0.005), for 2ne, 2nprop, and 3n2pent, respectively. These shifts were greater than cross-linking using UVAR (T(i) = 1.9 degrees C; P = 0.012). In the blue light region (400-500 nm), transmission was decreased by 5.6% (P = 0.003), 2.1% (P = 0.260), and 0% (P = 0.428) for 2ne, 2nprop, and 3n2pent, respectively.


CONCLUSIONS
beta-Nitro alcohols can induce corneal cross-linking in vitro better than the UVAR technique and can induce negligible effects on light transmission. These early results suggest that such compounds could be used as topical stiffening agents for keratoconus and related disorders.
Paik
David C
DC
Department of Ophthalmology, Edward S Harkness Eye Institute, Columbia University, College of Physicians and Surgeons, New York, New York 10032, USA.
Wen
Quan
Q
Braunstein
Richard E
RE
Airiani
Suzanna
S
Trokel
Stephen L
SL
D000818:Animals; D001831:Body Temperature; D003094:Collagen / Q000378:metabolism*; D003315:Cornea / Q000187:drug effects* / Q000502:physiology; D003432:Cross-Linking Reagents / Q000494:pharmacology*; D005486:Flavin Mononucleotide / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D008027:Light; D009574:Nitro Compounds / Q000494:pharmacology*; D000439:Pentanols / Q000494:pharmacology*; D017319:Photosensitizing Agents / Q000494:pharmacology; D020005:Propanols / Q000494:pharmacology*; D011489:Protein Denaturation; D012590:Sclera / Q000378:metabolism; D013552:Swine; D014466:Ultraviolet Rays
C496417:2-nitropropanol; C539264:3-nitro-2-pentanol; D003432:Cross-Linking Reagents; D009574:Nitro Compounds; D000439:Pentanols; D017319:Photosensitizing Agents; D020005:Propanols; D005486:Flavin Mononucleotide; D003094:Collagen