Periodic Reporting for period 1 - PHOTODOCTOR (Photodynamic Ocular Drug Delivery System with Optical Coherence Tomography Oriented Microscale Robots)
Reporting period: 2022-10-01 to 2024-09-30
Retinal diseases are the most common reason for irreversible blindness worldwide. Common retinal diseases, such as diabetic retinopathy, macular degeneration, retinal vein occlusion, and non-infectious uveitis, mostly require intravitreal steroid injections in clinical management. Unfortunately, the intravitreal steroid injections lead to other critical ocular problems, such as elevation of intraocular pressure, intravitreal infections, and progression of cataracts. Because of these reasons, targeted drug delivery systems are necessary for the medical treatment of retinal diseases. Photodynamic Ocular Drug Delivery System with Optical Coherence Tomography Oriented Microscale Robots (PHOTODOCTOR) project combines three novel technologies to solve this significant clinical problem. The first technological advancement for the project is dexamethasone-saturated hyaluronic acid (HA) hydrogels with organo-ruthenium complexes, which enables controllable degradation under visible light exposure. With the help of visible light-controlled degradation, dexamethasone can be released with the light pulses. Then, the hydrogels are supplemented with superparamagnetic iron oxide nanoparticles (SPIONs) and 3D printed as helical small-scale swimmers. Insertion of the SPIONs helps the magnetic actuation of the hydrogel-based small-scale robots in the intraocular space. Lastly, SPION-supplemented HA hydrogels can be observed with a high-resolution optical coherence tomography (OCT) system in the intraocular space to guide them in diseased areas of the retina. While HA-based structures increase penetration in vitreous cells and help attachment to the retina, SPIONs increase the visibility of the small-scale robots in OCT imaging. In this way, a magnetic-driven, visible light-triggered intraocular drug release system with OCT guidance is produced, and it could be used not only for intravitreal steroid delivery but also for the treatment of retinal tumors and other retinal problems.
In this project, we investigated several possibilities for hydrogel-based small-scale robots for intraocular drug delivery methods. We focused on the investigation of the possibilities for intraocular drug delivery with small-scale degradable robots in six main subjects: material selection, 3D-printing method, magnetic actuation, medical imaging, drug delivery, and biocompatibility. In each focused subject, we examined several possible state-of-the-art techniques to advance the current design of the intraocular implants and rebuild them as untethered actuable systems. After a detailed investigation of several possible systems, the current possible intraocular drug delivery system proposal is summarized in the graphical abstract.
After several trials with various combinations, the most feasible, reproducible, and realistic small-scale hydrogel-based degradable robots for intraocular steroid delivery are produced with the digital light processing 3D printing method. We designed and fabricated magnetically controllable degradable milliscale swimmers as intraocular drug implants using magnetic nanoparticle decorated acrylated polyethylene glycol hydrogel precursors with digital light processing 3D printing method. The magnetically controllable hydrogel-based swimmers have comparable dimensions with commercial intraocular implants that achieve high velocities in both aqueous and vitreous humor environments. Thanks to their high drug delivery capacities and slow degradation profiles, they can release the medications without disrupting retinal epithelial viability and barrier function.
In this project, we investigated several possibilities for hydrogel-based small-scale robots for intraocular drug delivery methods. We focused on the investigation of the possibilities for intraocular drug delivery with small-scale degradable robots in six main subjects: material selection, 3D-printing method, magnetic actuation, medical imaging, drug delivery, and biocompatibility. In each focused subject, we examined several possible state-of-the-art techniques to advance the current design of the intraocular implants and rebuild them as untethered actuable systems. After a detailed investigation of several possible systems, the current possible intraocular drug delivery system proposal is summarized in the graphical abstract.
After several trials with various combinations, the most feasible, reproducible, and realistic small-scale hydrogel-based degradable robots for intraocular steroid delivery are produced with the digital light processing 3D printing method. We designed and fabricated magnetically controllable degradable milliscale swimmers as intraocular drug implants using magnetic nanoparticle decorated acrylated polyethylene glycol hydrogel precursors with digital light processing 3D printing method. The magnetically controllable hydrogel-based swimmers have comparable dimensions with commercial intraocular implants that achieve high velocities in both aqueous and vitreous humor environments. Thanks to their high drug delivery capacities and slow degradation profiles, they can release the medications without disrupting retinal epithelial viability and barrier function.
The technical and scientific achievements of the project can be classified into five sections: Materials for intraocular implants, 3D-printing methods, magnetic actuation constraints, medical imaging possibilities, pharmacokinetics of hydrogel-based carriers, and aspects of biocompatibility. While each section is important per se, they are interconnected to each other for successful intraocular robotic implants. A detailed discussion on these topics was included in these two publications during the PHOTODOCTOR project (Bozuyuk U., et al., Adv. Mat., 2024; Wang T., et al., Nat. Rev. Bioeng., 2024).
Durability, strength, and controllable degradation were three important parameters for the hydrogels in this project. Several hydrogels are tested during the project and their stiffnesses, degradation products, and degradation time are investigated (Table 1). While the focus in these experiments was on the organic hydrogels, the durability and degradation mechanisms of the synthetic hydrogels exceed their organic counterparts. Because of that, PEGDA is selected as the main constituent for the hydrogel-based degradable body of the small-scale robots. During these investigations, we also published articles on other hydrogel-based structures, such as hydrogel muscles (Zhang M. et al., Nat. Mat., 2023).
There are several fabrication methods to build hydrogel-based small-scale robots, but only 3-D printing methods have both high throughput and high fidelity. Thus, we focused on various 3D printing methods, from two-photon polymerization to digital light processing. We found out that digital light processing (DLP) based 3D printing is significantly more reproducible, accessible, and affordable compared to other methods. Thus the small-scale intraocular robots produced with DLP 3D printing can easily integrate into the clinical practice and enhance personalized medicine options. We presented these results at the most prestigious conference in ophthalmology (Yildiz E., et al., IOVS, 2024).
During the investigation of the magnetic actuation systems for the small-scale robots, electromagnetic coils, and rotating permanent magnets are investigated. While electromagnetic coils can create more complex magnetic fields, rotating permanent magnets can enable the clinical usage of magnetic actuators without high-voltage electrical supplies. Because of their low energy profile and transportability, the rotating permanent magnets are selected as magnetic actuation controllers. Also, magnetic nanoparticles with high ferromagnetic profiles are required for the precise control and cargo-carrying capacity of the small-scale robots. For this reason, several magnetic nanoparticles were investigated, such as nickel-gold, iron-oxide, and iron platinum. At the end of the production of several nanoparticles in-house, iron platinum nanoparticles were selected for the magnetic actuation of small-scale robots. During this part of the project, we also build other magnetic microscale robots with other magnetic nanoparticles (Han M., et al., Nat. Comm., 2024).
In the last steps of the project, we focused on the pharmacokinetics and biocompatibility of these robotic implants. We investigated both dexamethasone levels and the negative effects of high-concentration dexamethasone on both retinal epithelium and immune cells. These results indicate that the slow-release profile of the passively degrading hydrogels can be better for clinical scenarios. Due to that, we avoided the actively induced degradation of hydrogels with light. The detailed results of both pharmacokinetics and biocompatibility will be shared with the public in the latest article of the project (Yildiz E., et al., In prep., 2024).
Durability, strength, and controllable degradation were three important parameters for the hydrogels in this project. Several hydrogels are tested during the project and their stiffnesses, degradation products, and degradation time are investigated (Table 1). While the focus in these experiments was on the organic hydrogels, the durability and degradation mechanisms of the synthetic hydrogels exceed their organic counterparts. Because of that, PEGDA is selected as the main constituent for the hydrogel-based degradable body of the small-scale robots. During these investigations, we also published articles on other hydrogel-based structures, such as hydrogel muscles (Zhang M. et al., Nat. Mat., 2023).
There are several fabrication methods to build hydrogel-based small-scale robots, but only 3-D printing methods have both high throughput and high fidelity. Thus, we focused on various 3D printing methods, from two-photon polymerization to digital light processing. We found out that digital light processing (DLP) based 3D printing is significantly more reproducible, accessible, and affordable compared to other methods. Thus the small-scale intraocular robots produced with DLP 3D printing can easily integrate into the clinical practice and enhance personalized medicine options. We presented these results at the most prestigious conference in ophthalmology (Yildiz E., et al., IOVS, 2024).
During the investigation of the magnetic actuation systems for the small-scale robots, electromagnetic coils, and rotating permanent magnets are investigated. While electromagnetic coils can create more complex magnetic fields, rotating permanent magnets can enable the clinical usage of magnetic actuators without high-voltage electrical supplies. Because of their low energy profile and transportability, the rotating permanent magnets are selected as magnetic actuation controllers. Also, magnetic nanoparticles with high ferromagnetic profiles are required for the precise control and cargo-carrying capacity of the small-scale robots. For this reason, several magnetic nanoparticles were investigated, such as nickel-gold, iron-oxide, and iron platinum. At the end of the production of several nanoparticles in-house, iron platinum nanoparticles were selected for the magnetic actuation of small-scale robots. During this part of the project, we also build other magnetic microscale robots with other magnetic nanoparticles (Han M., et al., Nat. Comm., 2024).
In the last steps of the project, we focused on the pharmacokinetics and biocompatibility of these robotic implants. We investigated both dexamethasone levels and the negative effects of high-concentration dexamethasone on both retinal epithelium and immune cells. These results indicate that the slow-release profile of the passively degrading hydrogels can be better for clinical scenarios. Due to that, we avoided the actively induced degradation of hydrogels with light. The detailed results of both pharmacokinetics and biocompatibility will be shared with the public in the latest article of the project (Yildiz E., et al., In prep., 2024).
The PHOTODOCTOR project built a guideline for the investigation of robotic implants for intraocular drug delivery. In this project, we characterized each step with several tests. We characterized the magnetic nanoparticles with a superresolution transmitting electron microscope and a vibrating sample magnetometer. Then, nanoparticles were coated with polydopamine polymers to enhance biocompatibility and hydrophilicity. The coating of the nanoparticles was observed with both UV and visible light spectrometers and a transmitting electron microscope. At the same time, the dexamethasone-loaded hydrogels were characterized with infrared spectroscope and hybrid rheometer measurements. Magnetic nanoparticle-coated hydrogel-based robotic implants characterized under microscope and other biomedical imaging modalities, such as optical coherence tomography, and optoacoustic imaging, for their actuation mechanism and untethered control. Both degradation and drug release of the robotic implants were measured with high-performance liquid chromatography. Lastly, the biocompatibility, efficiency, and immunocompatibility of the robotic implants were tested on both retinal pigment epithelial cells (ARPE-19) and microglia (EOC13.31) and reported (Yildiz E., et al., In prep., 2024).