Periodic Reporting for period 2 - SILK-EYE (Silk-based ocular implants: treating eye conditions at the interface of photonics and biology)
Reporting period: 2021-07-01 to 2022-12-31
Prevalent eye diseases, such as myopia, presbyopia, and corneal disease affect millions worldwide, but for now cannot be prevented. Surgical interventions of these conditions are turning to additive surgery, exemplified by corneal implants or the replacement of the natural crystalline lens by (or addition of) an intraocular lens, as it reduces complications of tissue removal surgeries.
Current eye treatments involving adding tissue or lenses exist in the form of amnion bandages, corneal inlays, and intraocular lenses. However, those approaches suffer from a number of shortcomings: corneal haze or rejection; risk of disease transmission, short lifespan, need of cryopreservation and donor tissue; lack of compliance of lens designs and biomaterials. In particular, no material has been found that fully meets the requirements for mechanical properties, transparency, biocompatibility and versatility for applications in the cornea and in accommodating intraocular lenses.
In recent years, silk fibroin derived from silkworm cocoons has emerged as a protein polymer for biomaterial applications. SILK-EYE will develop a new generation of corneal and intraocular implants, using silk-based materials tuned to each specific application and light enabling procedure. The silk-based implants will feature both the accessibility advantages of synthetic materials and the structural and biocompatibility properties of allografts, capitalizing on silk’s unique potential for transparency, controllable stiffness and degradability, refractive index and permeability, and their potential for light-induced cross-linking and bonding in the eye. SILK-EYE will design radically novel corneal dressings and implants, and accommodating intraocular lenses that are more biocompatible and functional than current synthetic implants, and are safer, more tunable, accessible and affordable than donor allografts, potentially revolutionizing how the major corrective procedures in ophthalmology are performed.
Current eye treatments involving adding tissue or lenses exist in the form of amnion bandages, corneal inlays, and intraocular lenses. However, those approaches suffer from a number of shortcomings: corneal haze or rejection; risk of disease transmission, short lifespan, need of cryopreservation and donor tissue; lack of compliance of lens designs and biomaterials. In particular, no material has been found that fully meets the requirements for mechanical properties, transparency, biocompatibility and versatility for applications in the cornea and in accommodating intraocular lenses.
In recent years, silk fibroin derived from silkworm cocoons has emerged as a protein polymer for biomaterial applications. SILK-EYE will develop a new generation of corneal and intraocular implants, using silk-based materials tuned to each specific application and light enabling procedure. The silk-based implants will feature both the accessibility advantages of synthetic materials and the structural and biocompatibility properties of allografts, capitalizing on silk’s unique potential for transparency, controllable stiffness and degradability, refractive index and permeability, and their potential for light-induced cross-linking and bonding in the eye. SILK-EYE will design radically novel corneal dressings and implants, and accommodating intraocular lenses that are more biocompatible and functional than current synthetic implants, and are safer, more tunable, accessible and affordable than donor allografts, potentially revolutionizing how the major corrective procedures in ophthalmology are performed.
A polymer chemistry lab has been set up, provided with all the needed equipment to extract the silk fibroin and produce silk fibroin-based materials with standardized protocols.
We have developed silk fibroin-based membranes cross-linked with different agents (ethanol, glycerol, horseradish peroxidase, polyethylene glycol…), being able to fine-tune the mechanical, transparency and degradability properties. The physical and chemical properties of the silk fibroin-membranes have been studied through different techniques: uniaxial extensiometry, Fourier transform infrared (FTIR) spectrophotometer, Scanning Electron Microscopy (SEM), Atomic Force Microscope (AFM), Second Harmonic Microscope, Optical Coherence Tomography (OCT), Elipsometry, X-ray diffraction (XRD), UV-Visible spectroscopy.
Biocompatibility essays with corneal fibroblasts and stability tests have narrowed down the silk fibroin-based membranes candidates from an initial pool of membrane production approaches. Silk fibroin membranes cross-linked with polyethylene glycol have more than 90% light transmission and are stable for more than 3 months. Alternative studied strategies include loading of the silk-fibroin membranes with frowth factors. Sustained release has been demonstrated with both growth-factor doped silk membranes through solution soaking and covalent bonding.
Extensive fibroblast cell cultures have demonstrated an adequate cell growth on top of membrane substrates and would closer under inserts made out of silk fibroin membranes cross-linked with polyethylene glycol. In addition, ex vivo experiments of silk fibroin-based membranes (rectangular bangages and contact lenses) which allowed obtained optimal dosage of photoinitiator concentration and irradiation dosages.
Following development of dedicated surgical procedures, we have demonstrated successful photobonding of silk-membranes to rabbit corneas in vivo, with appropriate re-epithelization and corneal healing.,
A new copolymer has been developed, which may be suitable as a material for corneal inlays. The bulk material has proved transparent, long residence times (>1 year un-degraded in saline solution) and glucose permeability near the diffusion coefficient of the human cornea, and therefore as a promising candidate for intrastromal implantation.
In parallel, Finite-Element mechanical computational models of the cornea and inlay have been developed to optimize inlay lenticule morphology and predicted the geometrical corneal response to lenticule implantation (as a function of inlay shape, mechanical properties, implantation depth and corneal biomechanical parameters).
As part of sophisticated modelling work, human eye accommodation plant eye models (capsular bag/zonulae/ciliary muscle) in preparation for the accommodating AIOL designs with novel biomaterials have also been developed. This modelling has been informed by ex vivo and in vivo experiments of scleral mechanical properties and crystalline lens morphology and accommodation, as well as patient’s tolerance to multitfocality.
We have developed silk fibroin-based membranes cross-linked with different agents (ethanol, glycerol, horseradish peroxidase, polyethylene glycol…), being able to fine-tune the mechanical, transparency and degradability properties. The physical and chemical properties of the silk fibroin-membranes have been studied through different techniques: uniaxial extensiometry, Fourier transform infrared (FTIR) spectrophotometer, Scanning Electron Microscopy (SEM), Atomic Force Microscope (AFM), Second Harmonic Microscope, Optical Coherence Tomography (OCT), Elipsometry, X-ray diffraction (XRD), UV-Visible spectroscopy.
Biocompatibility essays with corneal fibroblasts and stability tests have narrowed down the silk fibroin-based membranes candidates from an initial pool of membrane production approaches. Silk fibroin membranes cross-linked with polyethylene glycol have more than 90% light transmission and are stable for more than 3 months. Alternative studied strategies include loading of the silk-fibroin membranes with frowth factors. Sustained release has been demonstrated with both growth-factor doped silk membranes through solution soaking and covalent bonding.
Extensive fibroblast cell cultures have demonstrated an adequate cell growth on top of membrane substrates and would closer under inserts made out of silk fibroin membranes cross-linked with polyethylene glycol. In addition, ex vivo experiments of silk fibroin-based membranes (rectangular bangages and contact lenses) which allowed obtained optimal dosage of photoinitiator concentration and irradiation dosages.
Following development of dedicated surgical procedures, we have demonstrated successful photobonding of silk-membranes to rabbit corneas in vivo, with appropriate re-epithelization and corneal healing.,
A new copolymer has been developed, which may be suitable as a material for corneal inlays. The bulk material has proved transparent, long residence times (>1 year un-degraded in saline solution) and glucose permeability near the diffusion coefficient of the human cornea, and therefore as a promising candidate for intrastromal implantation.
In parallel, Finite-Element mechanical computational models of the cornea and inlay have been developed to optimize inlay lenticule morphology and predicted the geometrical corneal response to lenticule implantation (as a function of inlay shape, mechanical properties, implantation depth and corneal biomechanical parameters).
As part of sophisticated modelling work, human eye accommodation plant eye models (capsular bag/zonulae/ciliary muscle) in preparation for the accommodating AIOL designs with novel biomaterials have also been developed. This modelling has been informed by ex vivo and in vivo experiments of scleral mechanical properties and crystalline lens morphology and accommodation, as well as patient’s tolerance to multitfocality.
The following progress beyond the stat-of-the art have been produced:
1.- First silk-fibroin based corneal bandage and photobonding.based surgical procedure, proved on corneal cell culture in vitro, ex vivo and in vivo in a rabbit model
2.- First silk-fibroin co-polymer material for corneal inlays with promising biocompatibility properties based on glucose diffusion measurements, which will need to be proved in vivo. Initiated corneal/Material Finite element modelling, pulsed laser machine of the material into lenticules and ex vivo essays will prove the corneal reshaping capacity of the anticipated corneal inlay
3.- Sophisticated imaging and experimental simulation tools have allowed measurements and understanding compliance of an accommodating IOL with the patient accommodating plant and perception, providing feedback on the design and prospective mechanism of a silk-based accommodating IOL for the correction of presbyopia.
1.- First silk-fibroin based corneal bandage and photobonding.based surgical procedure, proved on corneal cell culture in vitro, ex vivo and in vivo in a rabbit model
2.- First silk-fibroin co-polymer material for corneal inlays with promising biocompatibility properties based on glucose diffusion measurements, which will need to be proved in vivo. Initiated corneal/Material Finite element modelling, pulsed laser machine of the material into lenticules and ex vivo essays will prove the corneal reshaping capacity of the anticipated corneal inlay
3.- Sophisticated imaging and experimental simulation tools have allowed measurements and understanding compliance of an accommodating IOL with the patient accommodating plant and perception, providing feedback on the design and prospective mechanism of a silk-based accommodating IOL for the correction of presbyopia.