Development of mucoadhesive Timolol loaded chitosan-nanocomposite to treat glaucoma.

Timolol Maleate is an aqueous soluble ß-blocker antiglaucoma drug used to suppress intraocular pressure. Several commercially available ocular formulations are not effective in delivering to the target site due to their water-soluble property and low mucoadhesiveness. Hence, there is a requirement for a highly mucoadhesive drug-loaded nanocomposite to suppress intraocular pressure with enhanced bioavailability. Herein, we have prepared a mucoadhesive Timolol-loaded graphene quantum dot-chitosan-nanocomposite to treat glaucoma in response to lysozyme, secreted in the tear fluid. The as-prepared nanocomposite has been characterized through high resolution-transmission electron microscopic, X-ray photoelectron spectroscopic, X-ray diffraction, and Fourier transform infrared spectral studies. The nanocomposite showed 93.74 % encapsulation efficiency with a loading capacity of 7.73 %. Further, 89.26 %, 95.62 %, and 99.29 % of drug release were observed from the nanocomposite in the presence of 1, 1.5, and 2 mg/mL of lysozyme. The mucoadhesion property has been confirmed by the increment in the particle size, fluorescence spectral variations, and Fourier transform infrared spectroscopic studies in the presence of mucin nanoparticles of size 291 nm. Interestingly, mucoadhesion has been demonstrated by pointing to the quenching in the luminescence of mucin. Further, in vitro biocompatibility assay on human corneal epithelial cells showed ≥80 % cell viability. Hence, this study offers the utilization of naturally secreting enzymes for drug delivery applications instead of uncontrolled pH and temperature-triggered releases.

Timolol-loaded ethosomes for ophthalmic delivery: Reduction of high intraocular pressure in vivo.

The beta-adrenoceptor blocker timolol maleate (TML) is a commonly used pharmaceutical agent for the management of glaucoma. Conventional eye drops have limitations due to biological or pharmaceutical factors. Therefore, TML-loaded ethosomes have been designed to mitigate these restrictions and give a viable solution for reducing elevated intraocular pressure (IOP). The ethosomes were prepared using the thin film hydration method. Integrating the Box-Behnken experimental strategy, the optimal formulation was identified. The physicochemical characterization studies were performed on the optimal formulation. Then, in vitro release and ex vivo permeation studies were conducted. The irritation assessment was also carried out with Hen's Egg Test-Chorioallantoic Membrane model (HET-CAM), and in vivo evaluation of the IOP lowering effect was also performed on rats. The physicochemical characterization studies demonstrated that the components of the formulation were compatible with each other. The particle size, zeta potential, and encapsulation efficiency (EE%) were found as 88.23 ± 1.25 nm, -28.7 ± 2.03 mV, and 89.73 ± 0.42 %, respectively. The in vitro drug release mechanism was found as Korsmeyer-Peppas kinetics (R2 = 0.9923). The HET-CAM findings verified the formulation's eligibility for biological applications. The IOP measurements revealed no statistical difference (p > 0.05) between the once-a-day application of the optimal formulation and the three-times-a-day application of the conventional eye drop. A similar pharmacological response was observed at lowered application frequencies. Therefore, it was concluded that the novel TML-loaded ethosomes could be a safe and efficient alternative for glaucoma treatment.

Development and Validation of Facile RP-HPLC Method for Simultaneous Determination of Timolol Maleate, Moxifloxacin Hydrochloride, Diclofenac Sodium and Dexamethasone in Plasma, Aqueous Humor and Pharmaceutical Products.

The present study aimed to develop a validated RP-HPLC method for the simultaneous determination of timolol maleate (TM), moxifloxacin hydrochloride (MOXI), diclofenac sodium (DS) and dexamethasone (DEXA) in human plasma, bovine aqueous humor and pharmaceutical preparations. The chromatographic separation was studied using the C18 column. The chromatographic conditions, such as composition, pH, the flow rate of mobile phase, the temperature of column, wavelength of absorption and injection volume of the sample, were studied. The method was validated to confirm specificity, linearity and accuracy in accordance with an International Conference on Harmonization guidelines. The optimum conditions for separation included mobile phase 0.05 M monobasic phosphate buffer: acetonitrile (65:35 v/v), pH of buffer adjusted to 6.2 and the flow rate of 1 mL/minute. The optimum temperature of the column was found to be 35°C, absorption wavelength 265 nm and injection volume 50 µL. The baseline separation of all four drugs with good sensitivity, resolution, and a less than 15 min run time was achieved. The retention time of TM, MOXI, DS and DEXA were 4.3,5.7,9.9 and 13.5 minutes respectively. The limit of detection (LOD) values were 6.2, 4.8, 0.8 and 1.2 ng/mL for TM, MOXI, DS and DEXA, respectively, whereas their respective limit of quantification (LOQ) values was: were 42.6, 26.8, 5.6 and 6.2 ng/mL. The coefficient of variation for intra-day and inter-day were in the range of 0.32-1.57 and 1.29-3.07%, respectively. The method was found to be sensitive, precise and accurate in human plasma and bovine aqueous humor and can be applied for the quantification of these compounds in plasma, aqueous humor and pharmaceuticals.

Imprinted ß-ketoenamine-linked covalent organic frameworks as dispersive sorbents for the fluorometric determination of timolol.

Timolol accompanied the formation of fluorescent ß-ketoenamine-linked covalent organic frameworks (COFs) via the Sc(Tof)3-catalyzed condensation of derivated carbaldehyde and hydrazide in a 1,4-dioxane/mesitylene porogen to construct timolol-imprinted COFs (TICOFs). With high imprinting factors, the synthesis-optimized TICOFs were characterized by fluorescence, UV-Vis spectrometry, X-ray diffraction, N2 adsorption/desorption analyses, scanning electron microscopy, and FTIR spectrometry. The TICOF fluorescence measured at 390 nm/510 nm is dynamically quenched by timolol and was thus utilized to quantify timolol in a linear range of 25-500 nM with a LOD of 8 nM. The TICOF recovered 99.4% of 0.5% timolol maleate in a commercial eye drop (RSD = 1.1%, n = 5). In addition, TICOF was used as a dispersive sorbent to recover 95% of 2.0 nM timolol from 20 mg of TICOF in 25 mL phosphate buffer. Dilution factors of 25 and 75 were the maximum tolerated proportions of the urine and serum matrix spiked with 2.0 nM timolol to reach recoveries of 92.4% and 90.3%, respectively.

Multiple drug delivery from the drug-implants-laden silicone contact lens: Addressing the issue of burst drug release.

A fixed combination of bimatoprost/timolol eye drop solution is used to manage the elevated intra-ocular pressure in glaucoma patients, including individuals whose condition is poorly controlled by monotherapy. Eye drop solutions are generally given in high dose, due to poor ocular bioavailability. The high ocular dose of bimatoprost and timolol lead to hyperaemia and systemic cardiac side effects respectively. Here, we introduce multiple implant-laden contact lenses (IM) to passively deliver timolol, bimatoprost and hyaluronic acid at therapeutically relevant doses without high burst release. The drug-loaded implants were individually implanted in the outer periphery of the silicone contact lenses. Atomic force microscopy showed the smooth surface of the implant contact lens, as the implants were inside the contact lens matrix. The implant lens (IM) showed major loss of drugs [timolol = 60.60%, bimatoprost = 61.75% and HA = 46.03%] during the monomer extraction and wet sterilization, while the option of dry radiation sterilization (IM-R lens) and hydration for 24 h prior to use showed relatively lower loss of drugs [timolol = 16.87%, bimatoprost = 47.95% and HA = 24.41%]. The in-vitro drugs release data of IM-R lens, showed sustained release for 72 h, with low burst release in comparison to the soaked (SM) and direct drug-laden contact lenses (DL). The in vivo drug release data in the rabbit tear fluid showed sustained release using IM-R lens in comparison to the SM lens and eye drop therapy. The burst release with the IM-R lens was many folds reduced, which could bypass the side effects associated with multiple eye drop therapy. The in vivo pharmacodynamic study in the rabbit model showed peak and valley profile with multiple eye drop therapy, while IM-R lens showed prolong reduction in intra ocular pressure (IOP) for 120 h. The study demonstrates the application of implantation technology to deliver multiple drug through contact lenses to treat glaucoma.

Synthesis and characterization of timolol maleate-loaded quaternized chitosan-based thermosensitive hydrogel: A transparent topical ocular delivery system for the treatment of glaucoma.

The chitosan-based thermosensitive hydrogel is one of the attractive in situ forming drug delivery systems that are suggested for ophthalmic applications. However, the use of this thermogel has been limited by non-transparency, relatively low solubility and prolonged gelation time. In this study, a convenient approach has been reported to develop transparent thermosensitive hydrogel with suitable cytocompatibility and gelation properties for glaucoma treatment. After obtaining the optimum quaternization conditions, the developed in-situ gelling formulation of quaternized chitosan was achieved by mixing sodium hydrogen carbonate with ß-glycerophosphate as a gelling agent. The formulation was a solution below or at room temperature and turned to a transparent hydrogel around ocular surface temperature within several minutes. The results of thermal and rheological evaluations demonstrated that adding sodium hydrogen carbonate has a synergic effect in enhancing the thermosensitivity of the hydrogel. Also, the prepared hydrogels based on quaternized chitosan presented obvious porous architectures, good swelling, and degradability. Hemolysis and cytotoxicity evaluations suggested that the developed hydrogels indicated good biocompatibility as a drug carrier. Finally, the in vitro release profile of timolol maleate as an anti-glaucoma model drug showed the initial burst release in the early hours and a steady linear release of drug from the hydrogel over 1 week. The obtained results confirmed that the developed hydrogel can be considered as an efficient drug delivery candidate for glaucoma therapy.

Rheo-dissolution: A new platform for the simultaneous measurement of rheology and drug release.

There is great potential to improve drug delivery through the use of in-situ gelling delivery systems. Here we demonstrate a technique capable of measuring changes in rheology (gelation and/or dissolution) of in-situ gelling delivery systems on contact with physiological fluid, while simultaneously analysing drug release. An ocular in-situ gelling formulation (gellan and timolol maleate) and an in-situ gelling oral liquid (alginate and metronidazole) were used as exemplar formulations. The method allowed profiling of increasing gellan concentration resulting in a reduction of timolol maleate released into simulated lacrimal fluid. When alginate was used as an in-situ gelling oral formulation there was a rapid increase in G' on contact with simulated gastric fluid. When this was changed to simulated intestinal fluid, drug release rate increased rapidly, coinciding with alginate gel dissolution. This work highlights the potential of this technology as a tool in development and optimisation of these increasingly popular delivery systems.

Development and evaluation of performance characteristics of timolol-loaded composite ocular films as potential delivery platforms for treatment of glaucoma.

Thin and erodible polymeric films were developed as potential ocular drug delivery systems to increase drug retention on the eye with the aim of improving bioavailability and achieving controlled drug release. Two biocompatible film forming polymers, hyaluronic acid (HA) and hydroxypropyl methylcellulose (HPMC), which are currently used as thickening agents in eye drops were employed. Two different films were prepared (i) as single polymer and (ii) as composite formulations by solvent casting method, incorporating glycerol (GLY) as plasticizer and timolol maleate (TM) as model glaucoma drug. After preliminary optimization of transparency and ease of handling, the formulations were further characterized for their physicochemical properties. No indication of significant drug-polymer or polymer-polymer (in composite films) interaction was observed from FTIR results while evaluation by IR mapping revealed uniform distribution of drug throughout the films. Amorphization of TM in the film matrix was confirmed by both DSC and XRD. Swelling studies illustrated remarkable swelling capacity of HA in comparison with HPMC which directly affected the drug release profiles, making HA a suitable polymer for controlled ocular drug delivery. Tensile and mucoadhesion properties confirmed higher elasticity and adhesiveness of HA while HPMC produced stronger films. The effect of sterilization by UV radiation on mechanical properties was also evaluated and showed no significant difference between the sterilized and non-sterilized films. The SEM results confirmed smoothness and homogeneity of film surfaces for all the formulations studied. The in vitro drug dissolution studies showed more extended release profiles of formulations containing HA. Cytotoxicity study (cell viability) using MTT assay on HeLa cells, confirmed that the single polymer and composite films are generally safe for ocular administration. The present work shows excellent film forming ability of HA and HPMC which can be used as single polymer or combined in composite formulations as potential topical ocular drug delivery platform to enhance drug retention on the ocular surface and therefore potential improved bioavailability.

Co-Delivery of Timolol and Brimonidine with a Polymer Thin-Film Intraocular Device.

PURPOSE: We developed a polycaprolactone (PCL) co-delivery implant that achieves zero-order release of 2 ocular hypotensive agents, timolol maleate and brimonidine tartrate. We also demonstrate intraocular pressure (IOP)-lowering effects of the implant for 3 months in vivo. METHODS: Two PCL thin-film compartments were attached to form a V-shaped co-delivery device using film thicknesses of ∼40 and 20 µm for timolol and brimonidine compartments, respectively. In vitro release kinetics were measured in pH- and temperature-controlled fluid chambers. Empty or drug-loaded devices were implanted intracamerally in normotensive rabbits for up to 13 weeks with weekly measurements of IOP. For ocular concentrations, rabbits were euthanized at 4, 8, or 13 weeks, aqueous fluid was collected, and ocular tissues were dissected. Drug concentrations were measured by liquid chromatography-tandem mass spectrometry. RESULTS: In vitro studies show zero-order release kinetics for both timolol (1.75 µg/day) and brimonidine (0.48 µg/day) for up to 60 days. In rabbit eyes, the device achieved an average aqueous fluid concentration of 98.1 ± 68.3 ng/mL for timolol and 5.5 ± 3.6 ng/mL for brimonidine. Over 13 weeks, the drug-loaded co-delivery device resulted in a statistically significant cumulative reduction in IOP compared to untreated eyes (P < 0.05) and empty-device eyes (P < 0.05). CONCLUSIONS: The co-delivery device demonstrated a zero-order release profile in vitro for 2 hypotensive agents over 60 days. In vivo, the device led to significant cumulative IOP reduction of 3.4 ± 1.6 mmHg over 13 weeks. Acceptable ocular tolerance was seen, and systemic drug levels were unmeasurable.

Thermo-sensitive nanogel-laden bicontinuous microemulsion drug-eluting contact lenses.

The bicontinuous microemulsion contact lens (BMCL) has nanoporous biphasic structures (100-250 nm) that are interconnected via multiple nano-channels, providing suitable retention of various drugs for glaucoma. Timolol maleate (TM)-carried thermosensitive poly(N-isopropylacrylamide) (PNIPAM) nanogel (30-50 nm) was incorporated into BMCLs by soaking or by centrifuging plus soaking. Here, we present drug-loading and release in silicon- or polyethylene oxide-microemulsion BMCLs under various conditions. Nanoporous BMCLs containing thermosensitive TM-laden nanogel were capable of potent body-temperature-triggered release of TM. Daily drug release was controllable according to the initial volume of drug-loaded (VDL) and loading method for sustained drug release, making them reduce drug-loss during transportation or storage. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1159-1169, 2019.

Development of a novel ion-pairing UPLC method with cation-exchange solid-phase extraction for determination of free timolol in human plasma.

A novel UPLC-UV method was developed for analysis of timolol in human plasma using a simple, fast, and cost effective ion-exchange SPE procedure, followed by separation on a C18 UPLC column with a mobile phase consisting of acetonitrile, phosphate buffer, and sodium 1-octane sulfonate as an ion pairing agent. The method was fully validated according to US-FDA guidelines, and was found to be sufficiently accurate and precise for analysis of timolol in human plasma for clinical pharmacokinetic studies. The application of ion-exchange SPE cartridges for purification of timolol in plasma produced excellent percent recoveries and good sample clean-up, while the ion-pairing separation described here allowed quantitation of timolol without interference from endogenous sample components. The method lower limit of detection was 1.7 ng/mL and the lower limit of quantitation was 5.0 ng/mL, allowing for analysis of therapeutic concentrations of timolol in plasma.

Self-Reporting Colorimetric Analysis of Drug Release by Molecular Imprinted Structural Color Contact Lens.

As a prospective ophthalmic drug delivery device, contact lenses attract a lot of attention because of the improved drug residence time and bioavailability. Herein, we proposed and fabricated a molecular imprinted structural color contact lens for sustained timolol release which could self-report the release process by color change. The specific recognition of target timolol by molecular imprinted sites can not only increase the loading amount and the residence time of the drug but also endow the structure color of lens remarkable blue shift with the accumulative release of timolol. The fascinating contact lens can be further used for controlling release of a large number of ophthalmic drugs and has high potential to be a new generation of functional contact lenses.

Exploring gelatin nanoparticles as novel nanocarriers for Timolol Maleate: Augmented in-vivo efficacy and safe histological profile.

The use of gelatin has been gaining recognition in ocular delivery for its safety profile and biocompatible properties. Timolol Maleate (TM) is an anti-glaucoma drug possessing poor corneal penetration while causing eye irritation making it an ideal candidate for novel nanoparticulate systems. Timolol Maleate loaded Gelatin Nanoparticles (GNPs) were prepared using the double desolvation method utilizing glutaraldehyde as the crosslinking agent. Optimization of the nanoparticles was achieved through a full-factorial design. An optimum formulation possessing particle size of 205 nm, zetapotential of 12.5 mV and an entrapment efficiency of 74.72% was selected. TEM imaging of the optimized nanoparticles was performed and the stability was tracked over 6 months. The in-vitro release studies showed a burst effect followed by a sustained profile. The selected formulae were tested in-vivo and compared to a Timolol marketed product on albino rabbits and were proven superior regarding intraocular pressure lowering and sustained efficacy. The prepared nanoparticles successfully passed Draize irritancy test and showed normal histology. These data indicate that the prepared GNPs possessed all needed qualities of a successful ocular system; corneal affinity, suitable particle size, high entrapment efficiency, sustained release, good stability, efficient lowering of intraocular pressure, high drug bioavailability and lack of irritancy.

Molecular interaction of some cardiovascular drugs with human serum albumin at physiological-like conditions: A new approach.

In the present study, the interaction of human serum albumin (HSA) with some cardiovascular drugs (CARs) under physiological conditions was investigated via the fluorescence spectroscopic and Fourier transform infrared spectroscopy. The CAR included Captopril, Timolol, Propranolol, Atenolol, and Amiodarone. Cardiovascular drugs can effectively quench the endogenous fluorescence of HSA by static quenching mechanism. The fluorescence quenching of HSA is mainly caused by complex formation of HSA with CAR. The binding reaction of CAR with HSA can be concluded that hydrophobic and electrostatic interactions are the main binding forces in the CAR-HSA system. The results showed that CAR strongly quenched the intrinsic fluorescence of HSA through a static quenching procedure, and nonradiation energy transfer happened within molecules. Fourier transform infrared spectroscopy absorption studies showed that the secondary structure was changed according to the interaction of HSA and CAR. The binding reaction of CAR with HSA can be concluded that hydrophobic and electrostatic interactions are the main binding forces in the CAR-HSA system. The results obtained herein will be of biological significance in pharmacology and clinical medicines.

In situ formation of injectable chitosan-gelatin hydrogels through double crosslinking for sustained intraocular drug delivery.

Rapid clearance and low ocular bioavailability are drawbacks of conventional ophthalmic eye drops. To increase the ocular drug resistance time and improve efficacy, an in situ forming and thermosensitive chitosan-gelatin hydrogel was developed. The feasibility of using this hydrogel as a topical eye drop formulation for sustained release of timolol maleate was evaluated. The flexible hydrogel that was co-crosslinked with ß­glycerophosphate disodium salt hydrate (ß-GD) and genipin showed a fast gel formation at 37 °C. The swelling properties and in vitro biodegradation characteristics showed a strong relationship with the initial genipin concentration. In vitro release profiles demonstrated that crosslinking with genipin reduced the release rate of entrapped model drugs and timolol maleate. In vitro cytotoxicity tests showed that the hydrogel was non-toxic to Chinese hamster fibroblast V79 cells. The hydrogel was further applied as eye drop formulations for sustained release of timolol maleate to reduce intraocular pressure (IOP). A fast gel formation was observed after instilling the chitosan-gelatin solution into the lower conjunctival sac of the rabbit eyes, and the in situ formed hydrogels protected the drugs from clearance by tears, and released the drugs in a sustained manner. Furthermore, administration of timolol maleate containing chitosan-gelatin hydrogels showed a long-lasting and effective IOP lowering efficacy for up to 24 h compared with the conventional eye drops. These results suggested that ß-GD and genipin co-crosslinked chitosan-gelatin hydrogels could be a useful ocular drug delivery platform with enhanced therapeutic effects and reduced side effects.

Proposal of degradation pathway with toxicity prediction for hydrolytic and photolytic degradation products of timolol.

Timolol (TIM) is a potent ß-adrenergic blocker, useful in treatment of ocular hypertension or open-angle glaucoma. Development and validation of stability indicating LCMS assay method for TIM was accomplished coherent with ICH guideline. Successful chromatographic separation of TIM with its four degradation products was attained by using gradient elution mode on reverse phase column using ammonium acetate buffer, pH 4.6 as mobile phase A and organic solvent as the mobile phase B. Chromatographic conditions were set such as 1.0 mL min-1 flow rate, 20 µL injection volume, 30 °C column temperature and 320 nm detection wavelength. Four major degradation products obtained from hydrolysis and photolysis, were identified and characterized with the combination of liquid chromatography-electrospray ionization mass spectrometry (LC-ESI/MS/MS) and accurate mass measurements. Degradation pathways were identified based on a comparison of the fragmentation pattern of the [M+H]+ ions of TIM and its degradation products. The method validation was performed as per ICH guideline Q2 (R1).

Sustained release timolol maleate loaded ocusert based on biopolymer composite.

In the present investigation, the effect of timolol maleate loaded ocuserts was studied as an alternative for conventional anti-glaucoma formulation. Ocuserts were prepared using natural polymer sodium alginate and ethyl cellulose. Physico-chemical properties along with drug entrapment efficiency (94-98%), content uniformity (93.1% ±â€¯0.264-98.00% ±â€¯0.321), in vitro drug release (83.42% ±â€¯0.35 at end of 12 h), ex vivo permeation all showed satisfactory results, which was found to follow zero order kinetics. Ex vivo permeation studies showed better results, revealed that the permeability coefficient was dependent on polymer type. The sterility test accelerated stability studies and in vivo studies such as eye irritancy test, in vivo drug release of the optimized ocusert was determined. The anti-glaucoma activity was measured using Schiotz tonometer at different time interval. Significant reduction in Intra ocular pressure (IOP) within 3 days was observed in case of rabbits treated with ocusert in comparison to the rabbit treated with marketed eye drop formulation. Hence timolol maleate loaded ocuserts proved to be a promising and viable alternative over conventional eye formulation for the sustained and controlled ophthalmic drug delivery, targeting the drug within the ocular globe thus improving patient compliance for the treatment of glaucoma.

Design and Evaluation of Transdermal Patches of Timolol Maleate.

BACKGROUND: Continuous intravenous infusion of controlled drug delivery has certain risks. This could be diligently duplicated devoid of its hassles by using the skin as the port of drug entry. Transdermal drug delivery system is the main route with discrete, self-contained dosage forms when placed on the skin, transporting the medicament through the skin into the systemic circulation in a wellcontrolled manner. OBJECTIVE: The rationale of the current work was to formulate and evaluate a transdermal patch of an antihypertensive drug by using different grades of polymers with a view to circumvent the hepatic first pass metabolism and also to escalate its bioavailability. METHODS: Solvent-casting method was used to prepare transdermal patches of timolol maleate using Eudragit RL100, Eudragit RS100, ethyl cellulose as polymers, and dibutyl phthalate as the plasticizer. The formulated patches were evaluated for their physiochemical parameters such as folding endurance, percentage moisture content, thickness, and water vapour transmission. The formulated patches were subjected to in-vitro permeation studies by using a Franz diffusion cell with a dialysis sac. The optimized formulation chosen on the basis of physiochemical characteristics and in-vitro studies was subjected to in-vivo studies on methyl prednisolone acetate-induced hypertensive rats. RESULTS: The data from release kinetics disclosed that the Korsmayer-Peppas could be the best fitting model. The results obtained from in-vitro studies disclosed that formulation with high proportion of Eudragit grade RL100 in acetone solvent system exhibited better drug release compared to rest of the formulations. The output obtained from in-vivo studies performed on rats revealed that the optimized formulation showed decrease in blood pressure from 158.53 ± 0.39 to 128.91 ± 0.50 mmHg. CONCLUSION: It was concluded that timolol maleate patch could be formulated into a matrix-type transdermal patch for the management of hypertension.

Drug-eluting silicone hydrogel for therapeutic contact lenses: Impact of sterilization methods on the system performance.

Although contact lenses are promising platforms for ocular drug delivery and have been extensively studied for that purpose, the influence of sterilization methods on these systems remains barely investigated. In this work, a silicone-based hydrogel was produced and loaded with different ophthalmic drugs: levofloxacin, chlorhexidine, diclofenac and timolol. The drug release profiles, along with several material properties, were evaluated before and after sterilization by three different methods steam heat, γ-irradiation and ozone gas. Independently of the sterilization method used, the results of the swelling and mechanical properties tests strongly indicate the occurrence of specific drug-polymer interactions promoted by the sterilization. In general, these interactions led to a decrease on the amount of drug released. It is shown that γ-irradiation and ozone led to significant degradation of all of the drugs used in this study. Thus, it was concluded that steam heat is the sterilization method with less impact on the devices. More importantly, the present work shows that the development of efficient and functional drug delivery devices for ophthalmic purposes cannot be done independently of a careful analysis of the influence of the sterilization procedures and methods on the degradation of these polymeric systems as a whole.

Fabrication and Characterization of Timolol Maleate and Brinzolamide Loaded Nanostructured Lipid Carrier System for Ocular Drug Delivery.

BACKGROUND: The combination of timolol maleate (TM) and brinzolamide (BRZ) has potential therapeutic prospects for treating glaucoma. However, the conventional formulation of TM and BRZ exhibits sub optimal therapeutic effects attributable to the poor ocular bioavailability of these drugs. OBJECTIVE: Therefore, the aim of the present study was to design and evaluate TM and BRZ loaded nanostructured lipid carrier (NLC) to enhance the bioavailabilities, permeation and precorneal residence time of these drugs that would result in efficacious treatment of glaucoma. METHODS: In this study, combination of drugs with different characteristic properties was loaded in NLC. The dual drugs loaded NLC was prepared by melt emulsification technique and evaluated for characteristic properties such as particle size (PS), polydispersity index (PDI), entrapment efficiency (EE) and drug loading (DL), in vitro drug release and ex vivo drug penetration studies. RESULTS: The PS and PDI of optimized NLC formulation were found to be 110.36 ±0.47 nm and 0.24 ± 0.00 respectively. The EE and DL of optimized NLC formulation were found to be 77.12 ± 0.64 % and 0.360 ± 0.01 % for TM respectively; whereas, 70.73±0.64 % and 0.71 ± 0.02 %for BRZ respectively. In vitro drug release studies showed a comparable initial rapid release of around 34 ± 2.90 % for TM and 38 ± 3.10 % for BRZ in the first 5 h followed by sustained drug release around 72.29 ± 5.90 % for TM and 70.08 ± 6.40 % for BRZ until last 24 h. Ex vivo drug penetration studies showed about 33.47 ± 2.80 % of TM and 36.20 ± 2.80 % of BRZ permeated in the first 5 h followed by 72.30 ± 6.40% of TM and 67.69 ± 6.500 % of BRZ until 24 h. There was remarkable enhancement in the release pattern and permeation of both the drugs from NLC as compared to that from their suspension. CONCLUSION: With dextrous optimization of dose and excipients concentration, the dual drugs with different characteristic properties can be successfully loaded in NLC formulation.