Development of a novel SupraChoroidal-to-Optic-NervE (SCONE) drug delivery system.

PURPOSE: Targeted drug delivery to the optic nerve head may be useful in the preclinical study and later clinical management of optic neuropathies, however, there are no FDA-approved drug delivery systems to achieve this. The purpose of this work was to develop an optic nerve head drug delivery technique. METHODS: Different strategies to approach the optic nerve head were investigated, including standard intravitreal and retroorbital injections. A novel SupraChoroidal-to-Optic-NervE (SCONE) delivery was optimized by creating a sclerotomy and introducing a catheter into the suprachoroidal space. Under direct visualization, the catheter was guided to the optic nerve head. India ink was injected. The suprachoroidal approach was performed in New Zealand White rabbit eyes in vivo (25 animals total). Parameters, including microneedle size and design, catheter design, and catheter tip angle, were optimized ex vivo and in vivo. RESULTS: Out of the candidate optic nerve head approaches, intravitreal, retroorbital, and suprachoroidal approaches were able to localize India ink to within 2 mm of the optic nerve. The suprachoroidal approach was further investigated, and after optimization, was able to deposit India ink directly within the optic nerve head in up to 80% of attempts. In eyes with successful SCONE delivery, latency and amplitude of visual evoked potentials was not different than the naïve untreated eye. CONCLUSIONS: SCONE delivery can be used for targeted drug delivery to the optic nerve head of rabbits without measurable toxicity measured anatomically or functionally. Successful development of this system may yield novel opportunities to study optic nerve head-specific drug delivery in animal models, and paradigm-shifting management strategies for treating optic neuropathies. TRANSLATIONAL RELEVANCE: Here we demonstrate data on a new method for targeted delivery to the optic nerve head, addressing a significant unmet need in therapeutics for optic neuropathies.

Photoactivated growth factor release from bio-orthogonally crosslinked hydrogels for the regeneration of corneal defects.

In situ-forming hydrogels are an attractive option for corneal regeneration, and the delivery of growth factors from such constructs have the potential to improve re-epithelialization and stromal remodeling. However, challenges persist in controlling the release of therapeutic molecules from hydrogels. Here, an in situ-forming bio-orthogonally crosslinked hydrogel containing growth factors tethered via photocleavable linkages (PC-HACol hydrogel) was developed to accelerate corneal regeneration. Epidermal growth factor (EGF) was conjugated to the hydrogel backbone through photo-cleavable (PC) spacer arms and was released when exposed to mild intensity ultraviolet (UV) light (2-5 mW/cm2, 365 nm). The PC-HACol hydrogel rapidly gelled within a few minutes when applied to corneal defects, with excellent transparency and biocompatibility. After subsequent exposure to UV irradiation, the hydrogel promoted the proliferation and migration of corneal epithelial cells in vitro. The rate of re-epithelialization was positively correlated to the frequency of irradiation, verified through ex vivo rabbit cornea organ culture studies. In an in vivo rat corneal wound healing study, the PC-HACol hydrogel exposed to UV light significantly promoted re-epithelialization, the remodeling of stromal layers, and exhibited significant anti-scarring effects, with minimal α-SMA and robust ALDH3A1 expression. Normal differentiation of the regenerated epithelia after healing was evaluated by expression of the corneal epithelial biomarker, CK12. The remodeled cornea exhibited full recovery of corneal thickness and layer number without hyperplasia of the epithelium.

Design and ex vivo development of a suprachoroidal spacer implant to treat glaucoma.

Glaucoma is a leading cause of visual impairment and blindness in the United States and worldwide. Elevated intraocular pressure (IOP) has been identified as the only modifiable risk factor in glaucoma, and there exists a need for a glaucoma procedure that is safe, efficacious, and can be performed in the outpatient clinic setting. Suprachoroidal expansion has been explored as a method to lower IOP previously. The purpose of this work was to design a monolithic hydrogel implant that would not clear or degrade to potentially achieve long term (possibly permanent) IOP reduction. Here, we developed and showed ex vivo testing of a novel photo-crosslinked polyethylene glycol (PEG) suprachoroidal spacer implant delivered via a custom-designed injector system. We optimized the composition, shape, and mechanics of the implant to be suitable for implantation with the suprachoroidal space. We developed a microneedle injector system to deliver this implant. We showed precise control over implant location and volume occupied within the suprachoroidal space. Further preclinical testing is needed to demonstrate efficacy.

Bioabsorbable, elastomer-coated magnesium alloy coils for treating saccular cerebrovascular aneurysms.

Cerebral aneurysm embolization is a therapeutic approach to prevent rupture and resultant clinical sequelae. Current, non-biodegradable metallic coils (platinum or tungsten) are the first-line choice to secure cerebral aneurysms. However, clinical studies report that up to 17% of aneurysms recur within 1 year after coiling, leading to retreatment and additional surgery. It would be ideal for the aneurysm coiling material to induce acute thrombotic occlusion, contribute to a tissue development process to fortify the degenerated vessel wall, and ultimately resorb to avoid leaving a permanent foreign body. With these properties in mind, a new fatty amide-based polyurethane urea (PHEUU) elastomer was synthesized and coated on biodegradable metallic (Mg alloy) coils to prepare a bioabsorbable cerebral saccular aneurysm embolization device. The chemical structure of PHEUU was confirmed using two-dimensional nuclear magnetic resonance spectroscopy. PHEUU showed comparable physical properties to elastomeric biodegradable polyurethanes lacking fatty amide immobilization, modest enzymatic degradation profiles in the first 8 wks, inherent antioxidant activity (>70% at 48 h), no cytotoxicity, and better protection for the underlying Mg alloy than poly(lactic-co-glycolic acid) (PLGA) against surface corrosion and cracking. Rat aortic smooth muscle cell attachment and platelet deposition were higher with the PHEUUs compared to bare or PLGA coated Mg alloy in vitro. PHEUU-coated Mg alloy coils showed the potential to design a fully bioabsorbable embolization coil amenable to clinical placement conditions based on computational mechanics modeling and blood-contacting test using an in vitro aneurysm model. In vivo studies using a mouse aneurysm model elicited comparable inflammatory cytokine expression to a commercially available platinum coil.

Aptamer-functionalized 2D photonic crystal hydrogels for detection of adenosine.

Aptamer-functionalized two-dimensional photonic crystal (2DPC) hydrogels are reported for the detection of adenosine (AD). As a molecular recognition group, an AD-binding aptamer was covalently attached to 2DPC hydrogels. This aptamer selectively and sensitively binds AD, changing the conformation of the aptamer from a long single-stranded structure (AD-free conformation) to a short hairpin loop structure (AD-bound conformation). The AD-binding-induced changes of aptamer conformation reduced the volume of the 2DPC hydrogels and decreased the interparticle spacing of the 2DPC embedded in the hydrogel network. The particle spacing changes being dependent on AD concentration were determined by measuring 2DPC light diffraction using a simple laser pointer. The 2DPC hydrogel sensor showed a large particle spacing decrease of ~ 110 nm in response to 1 mM AD in phosphate-buffered saline (PBS). The linear range of determination of AD was 0.1 nM to 1 mM and the limit of detection was 0.09 nM. The hydrogel sensor response for real samples was then validated in diluted fetal bovine serum (FBS) and human urine. The average % difference in particle spacing changes measured between diluted FBS and pure PBS was only 3.99%. In diluted human urine, the recoveries for the detection of AD were 95-101% and the relative standard deviations were 4.9-7.8%. The results demonstrate the potential applicability of the hydrogel sensor for real samples. This sensing concept, using the aptamer-functionalized 2DPC hydrogels, allows for a simple, sensitive, selective, and reversible detection of AD. It may enable sensor development for a wide variety of analytes by simply changing the aptamer recognition group.

DNA-Crosslinked 2D Photonic Crystal Hydrogels for Detection of Adenosine Actuated by an Adenosine-Binding Aptamer.

There is a need to develop versatile sensing motifs that can be used to detect a variety of chemical targets in resource-limited settings, for example, at the point of care. While numerous sensing technologies have been developed toward this effort, these technologies can be overly complex and require a skilled technician, extensive sample preparation, or sophisticated instrumentation to use, limiting their generalizability and application in resource-limited settings. Here, we report a novel sensing motif that utilizes DNA-crosslinked two-dimensional photonic crystal (2DPC) hydrogels. These hydrogel sensors contain a DNA aptamer recognition group that binds a target analyte. As proof of concept, we fabricated 2DPC hydrogels using a well-studied adenosine-binding aptamer. This adenosine aptamer is duplexed with a partially complementary strand and forms responsive crosslinks in the hydrogel polymer network. When adenosine is introduced, aptamer-adenosine binding occurs, breaking the DNA crosslinks and causing the hydrogel to swell. This in turn increases the particle spacing of an embedded 2DPC array, shifting the 2DPC Bragg diffraction. Thus, adenosine concentration can be monitored through 2DPC Bragg diffraction measurements. A linear range of 20 µM to 2 mM was observed. The detection limits were calculated to be 13.9 µM in adenosine-binding buffer and 26.7 µM in fetal bovine serum. This reported sensing motif has a readout that is simple and rapid and requires minimal equipment. We hypothesize that this sensing motif is generalizable and that other sensors can be easily fabricated by simply exchanging the aptamer that serves as a molecular recognition group.

Human Serum Phenylpyruvate Quantification Using Responsive 2D Photonic Crystal Hydrogels via Chemoselective Oxime Ligation: Progress toward Developing Phenylalanine-Sensing Elements.

There is a need to develop at-home phenylalanine (Phe) test kits, analogous to home glucose meters, for phenylketonuria patients who must measure their blood Phe levels frequently to adjust their diet. Unfortunately, such test kits are not available yet because of the lack of simple and inexpensive Phe-sensing elements. With the goal of developing a Phe-sensing element, we fabricated two-dimensional photonic crystal (2DPC) hydrogels that quantify human serum phenylpyruvate (PhPY), which is the product of the reaction between Phe and the enzyme phenylalanine dehydrogenase. The PhPY-sensing hydrogels have oxyamine recognition groups that link PhPY to the hydrogel polymer network via chemoselective oxime ligation. This structural modification induces the hydrogel to swell, which then increases interparticle spacings within the embedded 2DPC. The PhPY-induced particle spacing changes are measured from light diffraction and used to quantify the PhPY concentrations. The estimated limit of detection of PhPY in human serum for a detection time of 30 min is 19 µM, which is comparable to the minimum blood Phe concentrations of healthy people. Besides the potential application for developing Phe-sensing elements, this new hydrogel sensing approach via chemoselective oxime ligation is generalizable to the development of other chemical sensors working in complex biological environments.