Release of ranibizumab using a porous poly(dimethylsiloxane) capsule suppressed laser-induced choroidal neovascularization via the transscleral route

The administration of anti-vascular endothelial growth factor drugs in the posterior eye segment with sustained release through less invasive methods is a challenge in the treatment of age-related macular disease. We developed a flexible capsule device using porous poly(dimethylsiloxane) (PDMS) that was able to release ranibizumab. The porous PDMS sheet was fabricated by salt-leaching of a micro-sectioned PDMS sheet containing salt microparticles. Observation with scanning electron microscopy revealed that the pore densities could be adjusted by the concentration of salt. The in vitro release study showed that the release rate of fluorescein isothiocyanate-tagged albumin could be adjusted based on the pore density of the porous PDMS sheet. Ranibizumab could be released in a sustained-release manner for 16 weeks. The device was implanted on the sclera; its efficacy in terms of the suppression of laser-induced choroidal neovascularization (CNV) in rats was compared with that of monthly intravitreal injections of ranibizumab. At 8 and 18 weeks after implantation, the CNV area was significantly reduced in rats that received the ranibizumab-releasing device compared with those that received the placebo device. However, although monthly intravitreal injections of ranibizumab reduced CNV for 8 weeks, this reduction was not sustained for 18 weeks. In conclusion, we demonstrated a novel controlled-release device using a porous PDMS sheet that could suppress CNV via a less invasive transscleral route versus intravitreal injections. This device may also reduce the occurrence of side effects associated with frequent intravitreal injections.

Cyclosporine-loaded micelles for ocular delivery: Investigating the penetration mechanisms

Cyclosporine is an immunomodulatory drug commonly used for the treatment of mild-to-severe dry eye syndrome as well as intermediate and posterior segment diseases as uveitis. The ocular administration is however hampered by its relatively high molecular weight and poor permeability across biological barriers. The aim of this work was to identify a micellar formulation with the ability to solubilize a considerable amount of cyclosporine and promote its transport across ocular barriers. Non-ionic amphiphilic polymers used for micelles preparation were tocopherol polyethylene glycol 1000 succinate (TPGS) and Solutol® HS15. Furthermore, the addition of alpha-linolenic acid was assessed. A second aim was to evaluate micelles fate in the ocular tissues (cornea and sclera) to shed light on penetration mechanisms. This was possible by extracting and quantifying both drug and polymer in the tissues, by studying TPGS hydrolysis in a bio-relevant environment and by following micelles penetration with two-photon microscopy. Furthermore, TPGS role as permeation enhancer on the cornea, with possible irreversible modifications of tissue permeability, was analyzed. Results showed that TPGS micelles (approx. 13 nm in size), loaded with 5 mg/ml of cyclosporine, promoted drug retention in both the cornea and the sclera. Data demonstrated that micelles behavior strictly depends on the tissue: micelles disruption occurs in contact with the cornea, while intact micelles diffuse in the interfibrillar pores of the sclera and form a reservoir that can sustain over time drug delivery to the deeper tissues. Finally, cornea quickly restore the barrier properties after TPGS removal from the tissue, demonstrating its potential good tolerability for ocular application.

Rapidly dissolving bilayer microneedles enabling minimally invasive and efficient protein delivery to the posterior segment of the eye

The discovery of proteins that neutralise vascular endothelial growth factors, such as pegaptanib, ranibizumab and aflibercept, can inhibit the process of angiogenesis, thereby restoring eyesight in individuals with retinal vascular disorders. However, due to the posterior location and chronic nature of retinal diseases, a safe and effective intraocular protein delivery system is currently lacking. Thus, dissolving bilayer microneedles (MNs) with the potential to deliver proteins to the back of the eye in an efficient and minimally invasive manner were developed in this study. A model protein, ovalbumin (OVA), was incorporated into MNs fabricated from different polymers, including hyaluronic acid (HA), polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP). Optimised PVA/PVP MNs were demonstrated to be robust enough to pierce porcine sclera with > 75% of the needle length penetrating the sclera and dissolving within 150 s. SDS-PAGE and OVA-specific ELISA revealed that the bioactivity of the model protein was maintained during the manufacture of MNs. In hen's egg-chorioallantoic membrane test, MNs fabricated from all chosen polymers were classified as non-irritants. Furthermore, ex vivo permeation studies showed that optimised MNs could permeate 86.99 ± 7.37% of OVA through the sclera, twice that of the needle-free patch (42.16 ± 3.95%), highlighting the capability of MNs to circumvent physical barriers and promote protein delivery to the posterior segment of the eye. In this work, a novel, efficient and safe intraocular protein delivery system was successfully established.

Nanosuspension-loaded dissolving bilayer microneedles for hydrophobic drug delivery to the posterior segment of the eye

Intravitreal injections (IVT) are regarded as the gold standard for effective delivery of hydrophobic drugs to the back of the eye. However, as a highly invasive procedure, the injection itself may lead to poor patient compliance and severe complications. In this research work, a hybrid system of nanosuspensions (NS) and dissolving microneedles (MNs) was developed as an alternative to conventional hypodermic needles used in IVT for minimally invasive transscleral delivery of hydrophobic drugs. NS of a hydrophobic drug, triamcinolone acetonide (TA), were fabricated using a wet milling technique. TA NS optimised by central composite factorial design had a proven diameter of 246.65 ± 8.55 nm. After optimisation, TA NS were incorporated into MN arrays to form a bilayer structure by high-speed centrifugation. TA NS-loaded MNs were robust enough to pierce excised porcine sclera with insertion depth higher than 80% of the needle height and showed rapid dissolution (<3 min). In contrast, the plain TA-loaded MNs exhibited poor mechanical and insertion performances and took more than 8 min to be fully dissolved in the scleral tissue. Importantly, transscleral deposition studies showed that 56.46 ± 7.76 μg/mm² of TA was deposited into the sclera after 5 min of NS-loaded MN application, which was 4.5-fold higher than plain drug-loaded MNs (12.56 ± 2.59 μg/mm²). An ex vivo distribution study revealed that MN arrays could promote the transscleral penetration of hydrophobic molecules with higher drug concentrations observed in the deep layer of the sclera. Moreover, the developed TA NS-loaded MN array was biocompatible with ocular tissues, as demonstrated using the hens egg-chorioallantoic membrane assay and cytotoxicity test. The results presented here demonstrate that the hybrid system of NS and dissolving MNs can provide a novel and promising technology to alleviate retinal diseases in a therapeutically effective and minimally invasive manner.

Transscleral sustained ranibizumab delivery using an episcleral implantable device: Suppression of laser-induced choroidal neovascularization in rats

Successful treatment of age-related macular diseases requires an effective controlled drug release system with less invasive route of administration in the eye to reduce the burden of frequent intravitreal injections for patients. In this study, we developed an episcleral implantable device for sustained release of ranibizumab, and evaluated its efficacy on suppression of laser-induced choroidal neovascularization (CNV) in rats. We tested both biodegradable and non-biodegradable sheet-type devices consisting of crosslinked gelatin/chitosan (Gel/CS) and photopolymerized poly(ethyleneglycol) dimethacrylate that incorporated collagen microparticles (PEGDM/COL). In vitro release studies of FITC-labeled albumin showed a constant release from PEGDM/COL sheets compared to Gel/CS sheets. The Gel/CS sheets gradually biodegraded in the sclera during the 24-week implantation; however, the PEGDM/COL sheets did not degrade. FITC-albumin was detected in the retina during 18 weeks implantation in the PEGDM/COL sheet-treated group, and was detected in the Gel/CS sheet-treated group during 6 weeks implantation. CNV was suppressed 18 weeks after application of ranibizumab-loaded PEGDM/COL sheets compared to a placebo PEGDM/COL sheet-treated group, and to the intravitreal ranibizumab-injected group. In conclusion, the PEGDM/COL sheet device suppressed CNV via a transscleral administration route for 18 weeks, indicating that prolonged sustained ranibizumab release could reduce the burden of repeated intravitreal injections.

A drug refillable device for transscleral sustained drug delivery to the retina

Continuous drug administration with better adherence to treatment and less invasive procedures is important in treating retinal diseases such as age-related macular disease. In this study, we report a drug-refillable device consisting of a silicone reservoir and an injectable gelatin/chitosan gel (iGel). The silicone reservoir was fabricated with polydimethylsiloxane (PDMS) using a computer-aided design and manufacturing to have micropores at a releasing side for uniaxial release to the sclera. A stainless steel wire and sheet were combined in the side and bottom of the reservoir to ensure flexibility and to fit on the curvature of the eyeball and prevent irritation to the sclera through the bottom of the reservoir. The drug was injected and formulated in the reservoir by in situ crosslinking of gelatin/chitosan gel with the crosslinker; 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride. The in vitro release study using fluorescein molecules showed that the release rate from encapsulated iGel in the reservoir was slower than that from the original iGel. After reinjecting the iGel into the reservoir, the same release profile as the first injection was observed. The reservoir containing iGel was placed on the sclera of a rabbit and the distribution of 150 kDa fluorescein isothiocyanate-dextran (FD150) in the retina and choroid/retinal pigment epithelium (choroid/RPE) was studied. The cryosections showed that FD150 was observed in the choroid/RPE. Homogenates of the retina and choroid/RPE showed fluorescence during 12 weeks implantation, indicating the drug could be delivered to the retina by using the device. The drug filling was successful into the reservoir implanted on the sclera through the conjunctiva by using a needle. In conclusion, the refillable drug delivery device is a promising tool to administer drugs long-term by reinjection with less invasiveness to intraocular tissues.

A polymeric device for controlled transscleral multi-drug delivery to the posterior segment of the eye

The design of drug delivery systems that can deliver multiple drugs to the posterior segment of the eye is a challenging task in retinal disease treatments. We report a polymeric device for multi-drug transscleral delivery at independently controlled release rates. The device comprises a microfabricated reservoir, controlled-release cover and three different fluorescent formulations, which were made of photopolymeized tri(ethyleneglycol)dimethacrylate (TEGDM) and poly(ethyleneglycol)dimethacrylate (PEGDM). The release rate of each fluorescent is controlled by varying the PEGDM/TEGDM ratio in its formulation and the cover. The release kinetics appeared to be related to the swelling ratio of the PEGDM/TEGDM polymers. When the devices were implanted onto rat sclerae, fluorescence was observable in the ocular tissues during 4 weeks' implantation and distributed locally around the implantation site. Our polymeric system, which can administer multiple compounds with distinct kinetics, provides prolonged action and less invasive transscleral administration, and is expected to provide new tools for the treatment of posterior eye diseases with new therapeutic modalities.