Rabbit Aqueous Humor Research Articles

A Simple Validated LC-UV Method for the Simultaneous Determination of Brimonidine and Brinzolamide in the Presence of Brinzolamide's Degradation Product (Major Metabolite) in Rabbit Aqueous Humor.

A sensitive, specific, reliable and low-cost LC-UV method has been developed and validated for simultaneous quantification of brimonidine tartrate (BM) and brinzolamide (BZ) in rabbit aqueous humor (AH) in the presence of N-desethyl-brinzolamide (NDBZ); BZ is a major degradation product, and it is also considered to be its major metabolite. Dorzolamide hydrochloride (DZ) was used as an internal standard (IS). The analytes were extracted from rabbit AH samples by a simple pre-treatment utilizing ZnSO4.7H2O as a deproteinizing agent. The analytes were separated on a cyanopropyl Waters column (4.6 × 200mm, 5μm) with an isocratic mobile phase consisting of 25mM ammonium acetate pH4.5 (adjusted with 85% phosphoric acid):methanol:acetonitrile (94:4.5:1.5, v/v) at a flow rate of 1.0mLmin-1. The detection was done at 254nm. The lower limit of quantification in rabbit AH was 100.0ngmL-1. The method was validated according to EMA guidelines. The method was confirmed to be accurate, precise and linear over a range of 100.0-1000.0ngmL-1 for BM and BZ. The method developed herein is simple, safe, eco-friendly, rapid and accurately applied for the quantification of BM and BZ, along with the successful separation of NDBZ, which is considered as a potential irritant degradation product of BZ.

Novel Carbon Nanotubes/Gold Nanoparticles Modified Carbon Paste Electrochemical Sensor for Antazoline Determination in Aqueous Humor

Antazoline (ANT) is a H1 histamine receptor antagonist having anticholinergic properties used to decrease nasal congestion. It is found in eye drops usually in combination with either tetryzoline (TET) or xylometazoline (XLO). In this work, a novel electrochemical sensor based on carbon paste electrode (CPE) is developed for simple, rapid, sensitive, and selective determination of antazoline in pure form, different pharmaceutical formulations and in presence of aqueous humor. CPE is modified with nanoparticles multiwalled carbon nanotube (MWCNT) composite and further decorated with gold nanoparticles using amperometric electrodeposition technique to attain Au-NP@MWCNT/CPE for enhancing sensor sensitivity. Linearity is divided into two linear segments and found to be 2 × 10–7 − 2 × 10−6 (1st Linear segment) and 2 × 10–6 − 2 × 10−5 (2nd Linear segment) with limit of detection and quantification of 1.77 × 10−7 and 5.37 × 10−7, respectively. High sensitivity, selectivity, and reproducibility of the modified electrode towards determination of antazoline have promoted its applicability in different dosage forms and in rabbit aqueous humor. This method has noticeable potential applications in quality control, pharmacokinetic studies, and routine determination of antazoline drug in binary pharmaceutical formulations.

Impressive merger between green analytical approaches and quality- by- design for alcaftadine determination in eye drops and rabbit aqueous humor; application to stability study by two validated chromatographic methods

Nowadays, the main target of many researchers is to develop green environmentally friendly techniques that could separate drugs without using hazardous solvents which may lead to a dreadful impact on the environment. Proceeding from this lofty goal, the main concern of this work is to develop two green chromatographic techniques, namely, HPLC and TLC to determine alcaftadine (ALF) in pharmaceutical formulation, rabbit aqueous humor, and in presence of its degradate. Fortunately, and for the first time in the history of ALF analysis, the developed HPLC technique in this work succeeded to determine ALF in the presence of its oxidative degradate via a fruitful integration between green analytical chemistry and analytical quality-by-design resulting in increasing efficiency and minimizing environmental impacts. Utilizing an XBridge® C18 (4.6 × 250 mm, 5 µm) column, optimized chromatographic separation was accomplished utilizing isocratic elution with an ammonium acetate buffer (pH 5.0): ethanol (60:40, by volume) as the mobile phase, a flow rate of 1.5 mL/min, and UV detection at 282.0 nm. Over a concentration range of 0.1 to 8.0 µg/mL, linearity was attained. Additionally, this work succeeded to determine ALF through a stability indicating study using thin layer chromatographic technique on TLC plates precoated with silica gel 60F-254 as a stationary phase using a developing system consisting of dichloromethane: ethanol: ammonia (5:5:0.1, by volume) and scanned at 282.0 nm with 0.5–20.0 µg/band linearity range. Finally, the proposed methods were further assessed for their greenness profile using various greenness assessment tools. Fortunately, the developed methods proved to be safe, green, and eco-friendly.

Cobalt oxide nanoparticles modified coated graphite potentiometric sensor for quantification of sulfacetamide sodium in its pharmaceutical dosage form and spiked rabbit aqueous humor samples with greenness assessment

This study presents the fabrication of an innovative coated graphite electrode modified with cobalt oxide nanoparticles, for potentiometric determination of Sulfacetamide sodium. The functionalized nano-electrode was compared to a classical one; to study the advantages of addition of nanoparticles which was found to improve the performance characteristics of the electrode including improved sensitivity and selectivity, as well as, extended operational lifespan. The functionalized nano-electrode was more sensitive than the classical one with linearity range (1 × 10−7–1 × 10−2 M) and a limit of detection down to 2.24 × 10−8 M. This small modification increased the electrode’s potential stability by preventing the formation of a water layer on the surface of the solid contact electrode. The electrochemical performance of the proposed sensors was evaluated according to the IUPAC recommendation data and was found to be within the acceptable ranges. These developed potentiometric platforms were applied to quantitatively analyze Sulfacetamide sodium in its pure solutions, pharmaceutical dosage form and spiked rabbit aqueous humor with satisfactory recovery percentages without pre-extraction procedure nor interference of the co-formulated drug; Prednisolone acetate and excipients. The proposed method was statistically compared with the reported method in literature and no statistically significant difference was found. The proposed method was evaluated for its environmental sustainability utilizing the Green Analytical Procedure index (GAPI) as a greenness assessment tool.

Exquisite integration of quality-by-design and green analytical approaches for simultaneous determination of xylometazoline and antazoline in eye drops and rabbit aqueous humor, application to stability study

This work implements a stability indicating HPLC method developed to simultaneously determine xylometazoline (XYLO) and antazoline (ANT) in their binary mixture, rabbit aqueous humor and cited drug’s degradates by applying analytical quality-by-design (AQbD) combined with green analytical chemistry (GAC) experiment for the first time. This integration was designed to maximize efficiency and minimize environmental impacts, as well as energy and solvent consumption. Analytical quality-by-design was applied to achieve our aim starting with evaluation of quality risk and scouting analysis, tracked via five parameters chromatographic screening using Placket-Burman design namely: pH, temperature, organic solvent percentage, flow rate, and wavelength detection. Recognizing the critical method parameters was done followed by optimization employing central composite design and Derringer’s desirability toward assess optimum conditions that attained best resolution with satisfactory peak symmetry with short run time. Optimal chromatographic separation was attained by means of an XBridge® C18 (4.6 × 250 mm, 5 µm) column through isocratic elution using a mobile phase consists of phosphate buffer (pH 3.0): ethanol (60:40, by volume) at a 1.6 mL/min flow rate and 230.0 nm UV detection. Linearity acquired over a concentration range of 1.0–100.0 µg/mL and 0.5–100.0 µg/mL for XYLO and ANT, respectively. Furthermore, imperiling cited drugs' stock solutions to stress various conditions and satisfactory peaks of degradation products were obtained indicating that cited drugs are vulnerable to oxidative degradation and basic hydrolysis. Degradates' structures were elucidated using mass spectrometry. Applying various assessment tools; namely: analytical greenness (AGREE), green analytical procedure index (GAPI), analytical eco-scale, and national environmental method index (NEMI), Greenness method’s evaluation was applied and proved to be green. In fact, the developed method is established to be perceptive, accurate, and selective to assess cited drugs for routine analysis.

Design of Solid-contact Ion-selective Electrode with Multiwall-carbon Nanotubes for Assay of Sulfacetamide in Rabbit Aqueous Humour

Background: Inclusion of multiwall-carbon nanotubes (MWCNTs) as ion-to-electron transducers within the ionophore-doped PVC membrane has a great impact on the stability and robustness of the produced sensor performance compared to conventional liquid-based ISEs. Objective: Solid-contact ion selective electrodes (SC-ISEs) were fabricated and optimized for the assay of sulfacetamide sodium in both ophthalmic eye drops and in rabbit aqueous humor. Methods: 2-hydroxypropyl-β-cyclodextrin (2HP-β-CD) was selected as an ionophore to dope the ionselective membrane to enhance its selectivity towards sulfacetamide. The performance of multiwall-CNTs as ion-to-electron transducer was evaluated by comparing MWCNT-based SC-ISE with control sensor which does not include the MWCNTs. The electrochemical performance characteristics of the proposed sensors were assessed in accordance with the IUPAC recommendations. A green profile assessment of the proposed method was performed using Eco-Scale and AGREES metrics. Results: Inclusion of MWCNT into the sensing membrane improved the performance of the developed sensor. The linearity range was (2.5 x 10-4 M - 1.0 x 10-2 M) for both sensors and the LOD was estimated to be 5.6 x 10-5 M for GCE/ISM(CNT) and 1.5x 10-4 M for control sensor GCE/ISM. The results of green assessment for both the developed and the official method showed an excellent greenness of the proposed method. Conclusion: The proposed sensor can be applied successfully for the determination of sulfacetamide in eye drops and rabbit aqueous humour.

Development and Validation of UPLC–MS/MS Method for Quantitative Analysis of 5-Fluorouracil in Aqueous Humor of Rabbits

5-Fluorouracil (5-FU) is now used in eye drops for the management of conjunctival malignant melanoma, intraepithelial neoplasia, and corneal and conjunctival squamous cell carcinoma. The previously used methods for 5-FU quantification in AqH were time-consuming and less sensitive. Herein, a highly perceptive bioanalytical UPLC–MS/MS method was developed for the quantitative determination of 5-FU in the aqueous humor (AqH) of rabbits using allopurinol as the internal standard (IS). The 5-FU and IS were well separated in an Acquity™ HILIC column. Acetonitrile and 10 mM of ammonium acetate at 95:5 (v/v) were isocratically pumped at a 0.3 mL/min flow rate with a total runtime of 2.5 min. AqH samples were processed with a liquid–liquid extraction method in ethyl acetate. The 5-FU and IS were identified in the negative mode with electrospray ionization. The parent to daughter ion transitions for the 5-FU and IS occurred at m/z 128.92→41.68 and 134.80→64.10, respectively, as quantified using the multiple reaction monitoring mode. The developed method was validated with the ICH-Harmonized Guideline for Bioanalytical Method Validation, and the parameters were within acceptable limits. The calibration curve was linear at the 10.5–2000 ng/mL concentration range, with a correlation coefficient (R2) of 0.9946, and the lower limit of detection was 3.55 ng/mL. The developed and validated method was rapid, sensitive, accurate and robustly able to quantify 5-FU in rabbit AqH. The method was effectively applied to establish the ocular pharmacokinetics of 5-FU following the topical instillation of 5-FU-containing preparations in rabbits.

Novel solid-contact ion-selective electrode based on a polyaniline transducer layer for determination of alcaftadine in biological fluid.

Fabrication of a novel ion selective electrode for determining alcaftadine was achieved. The glassy carbon electrode (GCE) was utilized as a substrate in fabrication of an electrochemical sensor containing polyaniline (PANI) as an ion-to-electron transducer layer. A PVC polymeric matrix and nitrophenyl-octyl-ether were employed in designing the ion-sensing membrane (ISM). Potential stability was improved and minimization of electrical signal drift was achieved for inhibition of water layer formation at the electrode interface. Potential stability was achieved by inclusion of PANI between the electronic substrate and the ion-sensing membrane. The sensor's performance was evaluated following IUPAC recommendations. The sensor dynamic linear range was from 1.0 × 10-2 to 1.0 × 10-6 mol L-1 and it had a 6.3 × 10-7 mol L-1 detection limit. The selectivity and capabilities of the formed alcaftadine sensor were tested in the presence of its pharmaceutical formulation excipients as well as its degradation products. Additionally, the sensor was capable of quantifying the studied drug in a rabbit aqueous humor. Method's greenness profile was evaluated by the means of Analytical Greenness (AGREE) metric assessment tool.

Experimental evidence for the topical use of angiotensin-converting enzyme inhibitors in eye drops for eye ischemia treatment

Purpose: to evaluate the topical use effect of angiotensin-converting enzyme (ACE) inhibitor (iACE) Enalaprilat in eye drops on eye blood flow volume, hypoxia degree, ACE activity, and total antioxidant activity (TAA) in aqueous humor of rabbits with experimental ocular ischemia.Material and methods. Transient ocular ischemia in 30 Chinchilla rabbits was induced by subconjunctivally injecting 0.2 ml of 1 % Phenylephrine. Ocular ischemia degree was assessed by the minute volume of blood flow (MBF), determined with the help of ophthalmic plethysmography. 0.125 % Enalaprilat was administered by instillations. A CE activity in aqueous humor was measured using a spectrofluorometric assay with 0.1 mM Z-Phe-His-Leu substrate; the degree of hypoxia was estimated by the level of lactate in aqueous humor, which was determined by the enzymatic amperometric method. TAA was determined by registering chemiluminescence kinetics in the hemoglobin-H2O2-luminol model system.Results. A single instillation of iACE in the intact rabbit eye caused a decline of MBF value and A CE activity in aqueous humor. In ocular ischemia, ACE activity and t he lactate level in aqueous humor are increasing, while TAA is decreasing. Enalaprilat instillation in the eyes with ischemia lead to the normalization of MBF, ACE activity, lactate level and TAA in aqueous humor.Conclusion. Topical iACE in eye drops can penetrate eye tissues. Instillations of iACE during ischemia cause a remarkable increase of eye blood flow and reduce ACE activity, which is increased in ischemia. The anti-ischemic effect of iACE is accompanied by antihypoxant and antioxidant effects. Thus, iACE in eye drops can be used in ophthalmology as an anti-ischemic agent.

Chromatographic Analysis of Aqueous Humor of Bupivacaine in Different Administration Approaches.

Different administration approaches were investigated for the selection of bupivacaine administration type and a sensitive high-performance liquid chromatographic (HPLC) method has been developed. Developed method was validated and applied for the determination of bupivacaine in rabbit aqueous humor. The separation was achieved using a XTerra, C8 (250×8 mm i.d., particle size 5μm) analytical column with a mobile phase consisted of acetonitrile and sodium dihydrogen phosphate (pH = 3.0, 20mM; 30:70, v/v). Bupivacaine detection was performed by Diode Array detector (DAD) at 220 nm. The retention times for bupivacaine is 15.886 min. HPLC-DAD method was linear in the range of 75-4000 ng/mL. The limit of detection was 25 ng/mL and the limit of quantification of bupivacaine was found to be 75 ng/mL (relative standard deviation, RSD ≤ 15%, n = 6). In intra-day and inter-day precision and accuracy analysis, the RSD was found to be in the range of 0.96 and 7.98%, the bias values were 0.64 and 3.33%. Method was carried out for three different type of bupivacaine application because of the investigation of effective drug administration. Twenty aqueous humor samples were in the range of 0.642 and 5.124 μg/mL.

A High-Throughput LC-MS/MS Method for the Simultaneous Quantification of Twenty-Seven Drug Molecules in Ocular Tissues.

The purpose of this study was to develop a validated LC-MS/MS analytical method for the simultaneous analysis of a large cassette containing a wide range of drug substances with positive, negative, or neutral charge and further apply the method to assess octanol partition coefficient and eye tissue recovery of the drug cassette. A twenty-seven-drug cassette (N-in-one) including beta blockers, NSAIDs, and corticosteroids that range from extremely hydrophilic (sotalol) to very hydrophobic (triamcinolone hexacetanide) was used to develop an LC-MS/MS assay using QTrap 4500. An LC-MS/MS method based on gradient elution, with an eighteen-minute run time including equilibration time, was developed and validated for the rapid and simultaneous quantitation of drugs with a wide range of lipophilicities. Scheduled multiple reaction monitoring was used to maximize the scan time for each peak, ensuring sufficient scans. Method validation included lower limit of quantitation (LLOQ) and intra- and inter-day reproducibility. The LLOQ ranged from 0.5 (sotalol) to 40 fmols (dexamethasone) on column with a %RSD < 20%. The method was tested by measuring octanol:water and octanol:buffer (PBS, pH 7.4) partition coefficients and by quantitation of the drug cassette extracted from rabbit aqueous humor and cornea. Measured partition coefficients correlated positively with predicted values (r2=0.5-0.7). Drug recovery was ≥ 79% from aqueous humor and between 61 and 67% on average from cornea. A rapid, sensitive LC-MS/MS method suitable for N-in-one drug delivery screening was developed for simultaneous quantification of twenty-seven drugs in aqueous solutions and eye tissues.

Is it time for a moratorium on the use of benzalkonium chloride in eyedrops?

Is it time for a moratorium on the use of benzalkonium chloride in eyedrops?

Earth-friendly-assessed chromatographic platforms for rapid analysis of sulfacetamide sodium and prednisolone acetate in presence of sulfanilamide impurity: Application on ophthalmic formulation and aqueous humor

Sulfacetamide sodium as an antibacterial agent is co-formulated with prednisolone acetate in Phenamide-P® ophthalmic suspension to cure the ophthalmic infections correlated with inflammatory disorders. For the first time, two innovative, sensitive, specific, and robust chromatographic platforms were developed and their conditions were optimized for rapid analysis of the aforementioned drugs either in the absence or presence of sulfanilamide; a major impurity and degradation product of sulfacetamide sodium. The first platform is HPLC/UV in which separation of the three analytes was performed on a kinetex C18 column (4.6 × 100 mm, 2.6-μm) with isocratic elution using methanol: deionized water pH 3 (adjusted with orthophosphoric acid) in a ratio of (40:60 by volume) as a green mobile phase. The flow rate of the mobile phase was 1 mL/min and the UV detector was set at 262 nm. The second platform is HPTLC/densitometry in which the three analytes were separated on silica gel 60-F254 TLC plates using a developing system of chloroform: acetone: ammonia (6:2:0.1 by volume) and their developed bands were detected at 262 nm. The detection and quantitation limits were found in ranges of (0.01–0.03 μg/mL) and (0.03–0.09 μg/mL) for the HPLC platform while were found in ranges of (0.007–0.01 μg/band) and (0.02–0.04 μg/band) for the HPTLC platform, respectively. The suggested platforms were applied for the determination of sulfacetamide sodium and prednisolone acetate in spiked rabbit aqueous humor without interference by the matrix of aqueous humor. Greenness assessment was performed using eco-scale and GAPI tools revealing the excellent greenness of suggested platforms. According to ICH recommendations, the suggested platforms were validated producing satisfactory results within the accepted limits. The suggested platforms can be successfully applied for routine analysis of the aforementioned drugs not only in QC laboratories but also in the bioavailability centers due to the short analysis time of these platforms.

Chitosan-coated bovine serum albumin nanoparticles for topical tetrandrine delivery in glaucoma: in vitro and in vivo assessment

Glaucoma is one of the leading causes of blindness. Therapies available suffer from several drawbacks including low bioavailability, repeated administration and poor patient compliance with adverse effects thereafter. In this study, bovine serum albumin nanoparticles (BSA-NPs) coated with chitosan(CS) were developed for the topical delivery of tetrandrine (TET) for glaucoma management. Optimized nanoparticles were prepared by desolvation. pH, BSA, CS and cross-linking agent concentrations effects on BSA-NPs colloidal properties were investigated. CS-BSA-NPs with particle size 237.9 nm and zeta potential 24 mV was selected for further evaluation. EE% exceeded 95% with sustained release profile. In vitro mucoadhesion was evaluated based on changes in viscosity and zeta potential upon incubation with mucin. Ex vivo transcorneal permeation was significantly enhanced for CS coated formulation. In vitro cell culture studies on corneal stromal fibroblasts revealed NPs biocompatibility with enhanced cellular uptake and improved antioxidant and anti-proliferative properties for the CS-coated formulation. Moreover, BSA-NPs were nonirritant as shown by HET-CAM test. Also, bioavailability in rabbit aqueous humor showed 2-fold increase for CS-TET-BSA-NPs compared to TET with a sustained reduction in intraocular pressure in a rabbit glaucoma model. Overall, results suggest CS-BSA-NPs as a promising platform for topical ocular TET delivery in the management of glaucoma.

Enhancing Ocular Bioavailability of Ciprofloxacin Using Colloidal Lipid-Based Carrier for the Management of Post-Surgical Infection.

Conjunctivitis and endogenous bacterial endophthalmitis mostly occurred after ophthalmic surgery. Therefore, the present study aimed to maximize the ocular delivery of ciprofloxacin (CPX) using colloidal lipid-based carrier to control the post-surgical infection. In this study, CPX was formulated as ophthalmic liposomal drops. Two different phospholipids in different ratios were utilized, including phosphatidylcholine (PC) and dimyrestoyl phosphatidylcholine (DMPC). The physiochemical properties of the prepared ophthalmic liposomes were evaluated in terms of particle size, entrapment efficiency, polydispersity index, zeta potential, and cumulative CPX in-vitro release. In addition, the effect of sonication time on particle size and entrapment efficiency of CPX ophthalmic drops was also evaluated. The results revealed that most of the prepared formulations showed particle size in nanometer size range (460–1047 nm) and entrapment efficiency ranging from 36.4–44.7%. The antibacterial activity and minimum inhibitory concentration (MIC) were investigated. Ex vivo antimicrobial effect of promising formulations was carried out against the most common causes of endophthalmitis microorganisms. The pharmacokinetics of the prepared ophthalmic drops were tested in rabbit aqueous humor and compared with commercial CPX ophthalmic drops (Ciloxan®). Observed bacterial suppression was detected in rabbit’s eyes conjunctivitis with an optimized formulation A3 compared with the commercial ophthalmic drops. CPX concentration in the aqueous humor was above MIC against tested bacterial strains. The in vivo data revealed that the tested CPX drops showed superiority over the commercial ones with respect to peak aqueous humor concentration, time to reach peak aqueous humor concentration, elimination rate constant, half-life, and relative bioavailability. Based on these results, it was concluded that the prepared ophthalmic formulations significantly enhanced CPX bioavailability compared with the commercial one.

Effect of peripheral iridectomy on VEGF-A and TGF-\u03b2 levels in rabbit aqueous humour

BackgroundPeripheral iridectomy (PI), routinely performed during glaucoma filtration surgery, may contribute to scarring. This study aims to determine whether PI alters the concentrations of VEGF-A and TGF-β isoforms in the rabbit aqueous humour.MethodsAnterior chamber paracentesis (ACP) was performed in both eyes of six New Zealand white rabbits, with additional surgical PI performed in the right eyes. Eyes were examined on postoperative days (PODs) 1, 7, 30 and 60 by means of the tonopen, slit-lamp biomicroscopy, and bead-based cytokine assays for TGF-β and VEGF-A concentrations in the aqueous humor.ResultsACP caused a significant reduction in intraocular pressure (IOP) from mean preoperative 11.47 ± 1.01 mmHg to 5.67 ± 1.63 mmHg on POD 1 while PI did not cause further IOP reduction. Limbal conjunctival vasculature appeared slightly increased on POD 1 in both ACP and PI eyes with PI also causing mild bleeding from damaged iris vessels. Two PI eyes developed fibrinous anterior chamber reaction and/ or peripheral anterior synechiae. Aqueous VEGF-A levels were not significantly different between eyes treated with ACP and PI. Aqueous TGF-β concentrations distributed in the ratio of 4:800:1 for TGF-β1:TGF-β2:TGF-β3 respectively. While aqueous TGF-β2 was not significantly induced by either procedure at any time point, TGF-β1 and TGF-β3 were significantly induced above baseline levels by PI on POD 1.ConclusionPI increases the risk of inflammation. The combined induction of aqueous TGF-β1 and TGF-β3 by PI in glaucoma surgery may impact surgery success in glaucoma subtypes sensitive to these isoforms.

HPLC-MS/MS studies of brimonidine in rabbit aqueous humor by microdialysis.

Aim: The pharmacokinetic study of the brimonidine tartrate in situ gel in the anterior chamber of the rabbit eye was studied by microdialysis technique, and samples were analyzed by HPLC-MS/MS. Materials & methods: It was monitored in ESI mode at transition 291.9→212.0 and 296.0→216.0 for brimonidine and internal standard, respectively. Acetonitrile and 0.1% aqueous formic acid(50:50, v/v) were used as the mobile phase at 0.4ml/min. Results & conclusion: It showed a good linear correlation between 5 and5000ng/ml in microdialysis solution, and the inter- and intra-day precision (relative standard deviation) was less than 4.0%. The pharmacokinetic study showed that the AUC(0-t) of in situ gel was 3.5-times than that of eyedrops, which significantly improve the bioavailability of brimonidine.

Investigating nanostructured liquid crystalline particles as prospective ocular delivery vehicle for tobramycin sulfate: Ex vivo and in vivo studies.

Tobramycin remains the anchor drug for bacterial keratitis treatment and management; however, unlike other aminoglycosides, it does not pass through the gastrointestinal tract. The aim of the current investigation was to formulate tobramycin-loaded nanostructured liquid crystalline particles as an ophthalmic drug delivery system to ameliorate its preocular residence duration and ophthalmic bioavailability. Tobramycin cubosomes were fabricated by liquid–lipid monoolein, water, and poloxamer 407 as a stabilizer. Corneal penetration studies exhibited that the apparent permeation coefficient of tobramycin cubosomes was nearly 3.6-fold greater than marketed tobramycin eye drops. Ocular in vivo analysis performed in rabbits' eyes manifested that the intensity of bacterial keratitis was reduced on day 3, and on day 5, the manifestations were considerably mitigated with tobramycin cubosomes as compared to marked eye drops. Pharmacokinetic study of rabbit aqueous humor demonstrated that the area under curve and the peak concentration of optimized cubosomes were 3.1-fold and 3.3-fold, respectively, which was significantly higher than marketed eye drops. Moreover, histopathological studies illustrated the existence of normal ocular structures, thus indicating that there was no damage to the corneal epithelium or stromal layer. Consequently, the results acquired demonstrated that tobramycin-loaded cubosomal formulation could be a propitious lipid-based nanodelivery system that would enhance retention time and corneal permeability contrast to commercial eye drops.

Monitoring Imidazoline Derivatives via Functionalized Nano‐Potentiometric Platforms in Aqueous Humor and Dosage Forms

AbstractThe determination of two imidazoline derivatives [oxymetazoline HCl (OXY) and xylometazoline HCl (XYLO)] was described using different potentiometric platforms. The first electrode type was constructed using tetraphenyl borate (TPB) as anionic exchanger with β‐cyclodextrins (β‐CD) as ionophore forming oxymetazoline‐tetraphenyl borate (OXY‐TPB) and xylometazoline‐tetraphenyl borate (XYLO‐TPB), respectively. The second electrode type was prepared by modification of the first type by conjugation with magnetic iron oxide nanoparticles (MNP) forming (OXY‐MNP) and (XYLO‐MNP). The synthesized electrodes were fully characterized. The effect of magnetic nano‐sized particles as a highly dispersible material with β‐CDs on the electrode characteristics was investigated and compared against the classical electrodes. The response time, working pH range and selectivity coefficients were studied. The functionalized nano‐electrodes (OXY‐MNP and (XYLO‐MNP) were found to be more sensitive than the classical electrodes with linearity ranges (1×10−6–1×10−2 M). The functionalized nano‐electrodes were successfully applied for the in‐line analysis of OXY and XYLO in pharmaceutical dosage forms and spiked rabbit aqueous humor samples with no prior extraction of treatment. This suggests the future use of these electrodes in clinical studies of both drugs of interest.

Selective spectrofluorimetric determination of two corticosteroids along with their co-formulated drugs and degradation products in ophthalmic solution and aqueous humour.

Prednisolone acetate (PNO) and fluorometholone (FRT) are corticosteroids, co-formulated with moxifloxacin HCl (MFX) and cromolyn sodium (CML), respectively. PNO has a negligible quantum yield and its hydrolytic degradation products have enhanced fluorescence, which is 250-fold greater. FRT is a nonfluorescent drug, but its hydrolytic degradation products show reasonable fluorescence; MFX and CML have native fluorescence. Two methods were proposed based on the determination of PNO and FRT via their hydrolytic degradation products in the presence of other degradation products. Method (A) was developed for simultaneous determination of PNO and MFX in the presence of PNO degradation products by measuring peak amplitudes of the first derivative (1 D) of its enhanced fluorescence; PNO and MFX were measured at 345 and 473nm, respectively. Method (B) is a synchronous fluorescence spectroscopic method for simultaneous determination of FRT and its co-formulated drug CML in the presence of its degradation products. Fluorescence intensities were measured at λem 283 and 347nm for FRT and CML, respectively, using Δλ=99.20nm. Validation of the proposed methods was conducted as per International Council for Harmonisation (ICH) guidelines. The proposed methods were successfully applied for the determination of the proposed drugs in bulk powder, ophthalmic solution, and rabbit's aqueous humour.