Ex vivo and In vivo Evaluation of Chitosan Coated Nanostructured Lipid Carriers for Ocular Delivery of Acyclovir

Background: Herpes keratitis is the most common infectious cause of blindness in the developed world. It may be treated by acyclovir (ACV), however this antiviral drug is poorly soluble with low ocular bioavailability requiring high and frequent dosing. Nanostructured lipid carriers (NLCs) were investigated to improve the ocular bioavailability of ACV by enhancing corneal penetration as well as prolonging the exposure of infected cells to the antiviral agent. Methods: Cell uptake studies, ex vivo tolerance and cell uptake efficacy as well as in vivo corneal permeation of the developed lipid based formulations were investigated. NLCs were fabricated by the hot microemulsion technique and coated with 0.5% w/v chitosan. NLCs were capable of increasing the cell uptake of encapsulated fluorescein and ACV as examined by fluorescence microscopy and high performance liquid chromatography (HPLC) respectively. Results: When entrapped in NLCs, the antiviral efficacy of ACV was increased by 3.5 fold after 24 hrs of exposure. The in vivo corneal permeation of the formulation was studied on Albino rabbits with NLCs capable of increasing the corneal bioavailability by 4.5 fold when compared to a commercially available ACV ophthalmic ointment. Conclusion: NLCs enhanced the ocular bioavailability and antiviral properties of ACV through cell internalisation, sustained release, and increased corneal permeation

Azithromycin and dexamethasone loaded β-glucan films for the treatment of blepharitis

Background: Blepharitis is considered one of the most common ocular surface conditions in optometry and ophthalmology practice. While azithromycin and dexamethasone have been used successfully to treat blepharitis, they are generally formulated as eye drops requiring frequent administration. Ocular inserts based on biodegradable polymers may overcome some of the problems associated with conventional eye drops such as the fast nasolacrimal drainage. Methods: Inserts with different β-glucan and hydroxypropyl methycellulose (HPMC) compositions were prepared using the solvent-casting method and evaluated in terms of their appearance, thickness, weight, pH, mechanical strength, bioadhesive properties and drug-polymer interactions. The ability of the ocular inserts to provide controlled release of the drugs was assessed through an in vitro release study of dexamethasone and an antibacterial assay for azithromycin. Results: All parameters were found acceptable for ocular use, with the film laminate exhibiting the highest tensile strength and mucoadhesion. Differential Scanning Calorimetry (DSC) and Fourier Transform Infrared Spectroscopy (FTIR) revealed that the drugs were molecularly dispersed within the polymer films with no obvious interactions. Dexamethasone release was fast with 100% released within 1 hr. Azithromycin also showed a high burst release achieving the minimum inhibitory concentration after only 5 min; however, antibacterial activity was maintained for 24 hrs. Conclusion: Ocular inserts were successfully prepared and delivered both drugs over prolonged periods compared to conventional eye drops. However, additional coating may be required to further control the drug release

Characterization and evaluation of β-glucan formulations as injectable implants for protein and peptide delivery

Context: Injectable implants are biodegradable, syringeable formulations that are injected as liquids, but form a gel inside the body due to a change in pH, ions or temperature. Objective: To investigate the effect of polymer concentration, pH, ions and temperature on the gel formation of β-glucan, a natural cell-wall polysaccharide derived from barley, with particular emphasis on two-phase system formation after addition of dextran or PEG. Materials and methods: Oscillation viscometry was used to evaluate the gel character by measuring flow index (N), storage (G′) and loss (G″) moduli. Two-phase systems were further characterized for hardness and syringeability using a texture analyzer. Finally, in vitro release characteristics were determined using Franz diffusion cells. Results: Oscillation viscometry revealed that only addition of dextran or PEG resulted in distinct gel formation. This was seen by a decrease in N after polymer addition. Moreover, hardness (in g) of the gels increased significantly (p < 0.001) from 3.65 ± 0.43 to 34.30 ± 8.90 (dextran) and 805.80 ± 5.30 (PEG) 24 h after polymer addition. In vitro release profiles showed significantly (p < 0.05) reduced AUC₀₈h¹, k and percentage of drug released from two-phase systems compared to β-glucan dispersions, with the PEG system resulting in the lowest amount released over 8 h (15.1 ± 1.6%). Discussion: The unfavorable mixing enthalpy and higher water affinity of PEG resulted in the formation of a dense β-glucan gel. Conclusion: 1.5% (w/w) β-glucan combined with PEG at a ratio of 1:3 seemed to be the most promising injectable formulation with respect to fastest gel formation, increased hardness and sustained release

Preclinical Development of MGO Manuka Honey Microemulsion for Blepharitis Management

Objective To evaluate the in vitro antimicrobial effects of cyclodextrin-complexed and uncomplexed Manuka honey on bacteria commonly associated with blepharitis, and in vivo rabbit eye tolerability of a cyclodextrin-complexed methylglyoxal (MGO) Manuka Honey microemulsion (MHME). Methods and analysis In vitro phase: Bacterial growth inhibition was assessed by area under the growth curve (AUC) for Staphylococcus aureus, and the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) for S. aureus, Staphylococcus epidermidis and Pseudomonas aeruginosa with cyclodextrin-complexed and uncomplexed Manuka honey were determined. In vivo phase: Six rabbits were administered 20 µL of MHME (at 1:10 dilution) to the right eye (treated) and 20 µL of saline to the left eye (control) daily, for 5 days. Tear evaporation, production, osmolarity, lipid layer, conjunctival hyperaemia and fluorescein staining were assessed daily, before and 15 min after instillation. Results In vitro phase: The relative AUC for cyclodextrin-complexed Manuka honey was lower than that of uncomplexed honey at both 250 and 550 mg/kg of MGO (both p <0.05). Cyclodextrin-complexed honey had lower MIC and MBC than uncomplexed honey for both S. aureus and S. epidermidis, but not P. aeruginosa. In vivo phase: No significant changes were observed in the parameters assessed in either treated or control eyes (all p >0.05). Conclusion Overall, antimicrobial potency of cyclodextrin-complexed Manuka honey was greater than uncomplexed honey. No significant immediate or cumulative adverse effects were observed with MHME application on rabbit eyes, supporting future conduct of clinical safety and tolerability trials in human subjects

Critical Evaluation of Multifunctional Betaxolol Hydrochloride Nanoformulations for Effective Sustained Intraocular Pressure Reduction

Jie Hu,1,&ast; Huihui Li,1,&ast; Yingshan Zhao,1 Yuancheng Ke,1 Ilva D Rupenthal,2 Hanyu Liu,1 Jinghua Ye,1 Xinyue Han,1 Fan Yang,1 Wei Li,3 Huaqing Lin,1 Dongzhi Hou1 1Guangdong Provincial Key Laboratory of Advanced Drug Delivery Systems and Guangdong Provincial Engineering Center of Topical Precise Drug Delivery System, College of Pharmacy, Guangdong Pharmaceutical University, Guangzhou, Guangdong, People’s Republic of China; 2Buchanan Ocular Therapeutics Unit, Department of Ophthalmology, New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, 1142, New Zealand; 3Guangzhou Institute for Drug Control, Guangzhou, Guangdong, People’s Republic of China&ast;These authors contributed equally to this workCorrespondence: Huaqing Lin; Dongzhi Hou, Guangdong Pharmaceutical University, Guangzhou Higher Education Mega Center, 280 Wai Huan Dong Road, Guangzhou, People’s Republic of China, Tel +86 180 2631 2508, Fax +86 20 3935 2117, Email [email protected]; [email protected]: Glaucoma is a chronic disease that requires long-term adherence to treatment. Topical application of conventional eye drops results in substantial drug loss due to rapid tear turnover, with poor drug bioavailability being a major challenge for efficient glaucoma treatment. We aimed to prepare the anti-glaucoma drug betaxolol hydrochloride (BH) as a novel nano-delivery system that prolonged the retention time at the ocular surface and improved bioavailability.Methods: We constructed multifunctional nanoparticles (MMt-BH-HA/CS-ED NPs) by ion cross-linking-solvent evaporation method. The particle size, zeta potential, encapsulation efficiency and drug loading of MMt-BH-HA/CS-ED NPs were physicochemically characterized. The structure of the preparations was characterized by microscopic techniques of SEM, TEM, XPS, XRD, FTIR and TGA, and evaluated for their in vitro release performance as well as adhesion properties. Its safety was investigated using irritation assays of hemolysis experiment, Draize test and histopathology examination. Precorneal retention was examined by in vivo fluorescence tracer method and pharmacokinetics in tear fluid was studied. A model of high IOP successfully induced by injection of compound carbomer solution was used to assess the IOP-lowering efficacy of the formulation, and it was proposed that micro-interactions between the formulation and the tear film would be used to analyze the behavior at the ocular surface.Results: The positively charged MMt-BH-HA/CS-ED NPs were successfully prepared with good two-step release properties, higher viscosity, and slower pre-corneal diffusion rate along with longer precorneal retention time compared to BH solution. The micro-interactions between nanoparticles and tear film converted the drug clearance from being controlled by fast aqueous layer turnover to slow mucin layer turnover, resulting in higher drug concentration on the ocular surface, providing more durable and stable IOP-lowering efficacy.Conclusion: The novel multifunctional MMt-BH-HA/CS-ED NPs can effectively reduce IOP and are suitable for the treatment of chronic disease glaucoma.Graphical Abstract: Keywords: glaucoma, nanoparticles, betaxolol hydrochloride, BH, precorneal retention, micro-interaction