ascorbic-acid and ascorbyl-monolaurate

The aim of this work was evaluate the antioxidant effect of ascorbyl laurate (ASC12) based nanostructures applied topically to the cornea of ocular normotensive and hypertensive rabbits. The ASC12 was chosen for its capacity to form liquid lyotropic crystal and keeps its free radical trapping power.. The hypertension model was performed in six rabbits and was obtained by the application of intracameral injections of alpha-chymotrypsin in the right eye. A single 50 ml dose of ascorbyl laurate coagel 2% w/v (COA-ASC12) was applied topically to the cornea of six normotensive and six hypertensive rabbits. The aqueous humor samples were obtained before and after instillation of COA-ASC12 at different times (2 h and 4 h). Antioxidant capacity was determined via the reduction reaction with iron and tripyridyltriazine (FRAP) and the total proteins were measured using the Bradford reagent.. The kinetic antioxidant capacity in the aqueous humor of normotensive and hypertensive rabbits showed a maxim increment at 4 h instillation. Also, the antioxidant capacity in the aqueous humor of hypertensive rabbits was ten times lower than in normotensive rabbits.. This type of nanostructures has the potential to significantly improve the topical formulation for the prophylaxis and treatment of several eye diseases.

Topics: Administration, Ophthalmic; Animals; Antioxidants; Aqueous Humor; Ascorbic Acid; Disease Models, Animal; Gels; Intraocular Pressure; Nanostructures; Ocular Hypertension; Rabbits

Nanobubbles and microbubbles are non-invasive ultrasound imaging contrast agents that may potentially enhance diagnosis of tumors. However, to date, both nanobubbles and microbubbles display poor in vivo tumor-selectivity over non-targeted organs such as liver. We report here cyanine 5.5 conjugated nanobubbles (cy5.5-nanobubbles) of a biocompatible chitosan-vitamin C lipid system as a dual ultrasound-fluorescence contrast agent that achieved tumor-selective imaging in a mouse tumor model. Cy5.5-nanobubble suspension contained single bubble spheres and clusters of bubble spheres with the size ranging between 400-800 nm. In the in vivo mouse study, enhancement of ultrasound signals at tumor site was found to persist over 2 h while tumor-selective fluorescence emission was persistently observed over 24 h with intravenous injection of cy5.5-nanobubbles. In vitro cell study indicated that cy5.5-flurescence dye was able to accumulate in cancer cells due to the unique conjugated nanobubble structure. Further in vivo fluorescence study suggested that cy5.5-nanobubbles were mainly located at tumor site and in the bladder of mice. Subsequent analysis confirmed that accumulation of high fluorescence was present at the intact subcutaneous tumor site and in isolated tumor tissue but not in liver tissue post intravenous injection of cy5.5-nanobubbles. All these results led to the conclusion that cy5.5-nanobubbles with unique crosslinked chitosan-vitamin C lipid system have achieved tumor-selective imaging in vivo.

Topics: Animals; Ascorbic Acid; Carbocyanines; Cell Line, Tumor; Contrast Media; Diagnostic Imaging; Female; Mice; Mice, Inbred BALB C; Microbubbles; Neoplasms; Ultrasonography

To evaluate the performance of 6-O-Lauryl-l-ascorbic acid nanostructures (coagels) as vehicles for acetazolamide (AZM) in ophthalmic administration by in vitro and in vivo experimental tests.. The systems of coagel + AZM were evaluated in terms of their in vitro release (dialysis membrane), permeability (isolated cornea), pharmacological effectiveness [intraocular pressure (IOP)-reduction in normotensive rabbits], and potential irritant effects.. The results concerning AZM permeation were better when vehiculized in coagels compared with ringer solution, which was evident from the AZM steady-state flux and P(app) values (J=1.43 μg/min and P(app)=3.04 cm.s(1)). As a consequence of this increase in permeation, the coagel-AZMs were more effective in lowering the IOP, according to the results obtained from the in vivo assays. Coagels loaded with 0.4% (W/W) of AZM showed a higher hypotensive effect in rabbits compared with the commercial formulation AZOPT(®) (brinzolamide 1%), mainly due to the prolonged effect of the former. In all cases, the intensity of irritation was time dependent. The sodium lauryl sulphate solution (2%) used as a positive control produced serious injury 30 min postadministration. This effect caused irritation, which decreased slowly and even at 180 min, the discomfort was still considerable. However, in the case of coagels, a mild-to-moderate effect was observed.. The incorporation of AZM in coagels seems to improve the ocular bioavailability of this drug. Coagel-AZM 0.4% showed a higher hypotensive effect, with a mild-to-moderate irritant effect. These systems could be administrated in human beings, although more detailed studies still need to be carried out.

Topics: Acetazolamide; Animals; Ascorbic Acid; Biological Availability; Carbonic Anhydrase Inhibitors; Cornea; Dialysis; Drug Carriers; Drug Delivery Systems; Intraocular Pressure; Nanostructures; Ophthalmic Solutions; Permeability; Rabbits

Vitamin C is a popular antioxidant; however, its water solubility limits its function in the lipid environment. As a result, the antioxidative properties of its lipophilic derivatives have aroused research attention, especially L-ascorbyl-6-laurate (VC-12). We have investigated the effect of a high concentration of VC-12 on 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH)-induced haemolysis of human erythrocytes. The findings indicated that VC-12 was capable of protecting erythrocytes against AAPH-induced haemolysis when its concentration was below 60 microM. With an increase in the concentration of VC-12 and a decrease in the concentration of AAPH, VC-12 promoted haemolysis remarkably, the mechanism of which has been proposed as VC-12-mediated peroxidation. When the concentration of VC-12 was increased to above 150 microM, VC-12 promoted haemolysis by its function as a surfactant, to unbalance the osmotic pressure within and outside erythrocytes. High concentrations of VC-12 may have generated radicals via autooxidation, resulting in eventual haemolysis. Therefore, the double-faced effect of VC-12 on haemolysis of human erythrocytes was due to its concentration. This information may be useful for the safe use of lipophilic vitamin C.

Topics: Amidines; Antioxidants; Ascorbic Acid; Dose-Response Relationship, Drug; Erythrocytes; Free Radicals; Hemolysis; Humans; Lipid Peroxidation; Osmotic Pressure; Oxidants; Oxidation-Reduction