(Spotlight on Nanowerk) What makes contact lenses so attractive for the development of all kinds of biosensors is the fact that they swim on a film of tears – and tear fluid, as well as sweat and saliva, has potential huge for non-invasive monitoring of biological signals as it contains a wide variety of physiological indices such as protein, glucose and pH.
As a source of biosignal monitoring, tears have the advantages of easy access, low sampling complexity, and minimal invasiveness, providing an on-demand supply for continuous, real-time monitoring. of health.
Researchers have already demonstrated biosensor contact lenses using nanomaterials to monitor glucose with transparent transistors and with graphene for diagnosing diabetes and glaucoma.
Previously, we have also reported on various research projects aimed at developing contact lenses as smart electronic sensor devices for various point-of-care monitoring and wireless biomedical detection. A recent example has been long-term continuous glucose monitoring with smart contact lenses based on bimetallic nanocatalysts immobilized in nanoporous hydrogels.
Along with the rapid progress and miniaturization of wearable bioelectronics, there have been many efforts to develop smart contact lenses (SCLs) that sense through tear fluid. Especially after Google smart contact lens project announcement in 2014, global interest in SCL research increased.
These SCL studies range from the detection of biosignals (intraocular pressure, glucose, cortisol) to therapeutic tools (aniridia, chronic ocular inflammation). Additionally, multidisciplinary research continues to develop advanced SCLs with various attributes such as sensitivity enhancement, wireless signal transmission, and custom design using 3D printing technology.
Some of these technologies are already moving from the lab to commercial applications. The start-up Mojo Vision caught the eye in 2020 by introducing the first SCL concept that could demonstrate data display based on augmented reality (AR) technology. The company’s smart contact lens features a tiny sand-grain-sized microLED display to share critical information, and smart sensors powered by solid-state batteries built into a scleral lens that also corrects your vision .
In addition to diagnostic applications of biosensors, contact lenses are an attractive delivery platform for drugs for the treatment of eye diseases. For example, one project demonstrated a drug-dispensing contact lens that delivers glaucoma medication continuously for a month. Even more promising is the first clinical trial of LLT-BMT1, a drug-eluting contact lens MediPrint Ophthalmichas been shown to be safe and well tolerated for the treatment of glaucoma.
Despite these promising prospects and the expectations of smart contact lenses, there are still issues to be resolved with regard to commercialization – transparency (opaque electronic material), reliability (scalability, repeatability), biocompatibility (rigidity, size, irritation) and effects underlying side effects that may occur, such as dry eye syndrome.
An excellent recent review article in Advanced materials (“Contact Lens Laboratory: Recent Advances and Future Opportunities in Diagnostics and Therapeutics”) provides a comprehensive overview of recent advances and future opportunities for the use of SCLs for diagnostic and therapeutic purposes.
The authors begin by reviewing smart contact lens materials and manufacturing methods, followed by an in-depth discussion of SCLs as an effective diagnostic tool for detecting biosignals from ocular or tear fluids. Next, they summarize SCLs for therapeutic applications, including typical characteristics and responsive strategies and offer an overview of current marketable therapeutic SCLs and examples in clinical trials.
With an eye to next-generation wearable sensor platforms, they provide a summary of wearable power systems and wireless transmission technologies, and highlight representative examples of the next generation of SCL wearable platforms. .
Looking ahead, there are several exciting and untapped opportunities that provide ample room for future development across multiple research areas, characterized by six important aspects:
1) New SCL materials with extraordinary properties such as materials with antibiotics, supreme wettability and suitable temperature tolerance.
2) SCL with brand new features. Next-generation lenses should integrate multiple sensing modal components – such as physical vital signs and tear fluid metabolites – to achieve accurate medical care. In addition to the role of biosensing, researchers envision that optical and electrical communications, visual stimulation, and even recording and augmented reality (AR) may be achievable by incorporating electrically conductive coatings or applying contact lens materials that are inherently drivers.
3) SCL platform via wireless power supply. Current power supplies for electric contact lenses have significant limitations with respect to size and long-term operation. Here, a flexible wireless rechargeable battery or supercapacitor with an overall size and power density matching potential SCL applications should be developed. Another futuristic option is a contact lens with integrated micro solar cells – something researchers are already working on.
4) Intelligence and programmability of SCL diagnostic and therapeutic platforms. The integration of artificial intelligence (AI) technologies in the control module is attractive for SCL systems, such as automatically controlled release of drugs. Additionally, AI algorithms can collect long-term data from contact lens biosensors and then transform it into scientific and clinically meaningful information to classify human health conditions and diagnose eye abnormalities and diseases. In addition, the AI-enabled SCL platform can obtain feedback from the lens’s built-in sensor module, eventually realizing closed-loop and autonomous control.
5) Translations and marketing from lab to bedside. Representative examples that have been successfully commercialized with various design philosophies are already available: use to monitor glucose level (e.g., Google Lens project) and detect intraocular pressure (e.g., sentient triggerfish); incorporation of AR (e.g. Mojo Vision, InWith) and head-up display (for example, Innovega eMacula®); feasible drug delivery (e.g., OcuMedic).
6) During the COVID-19 pandemic, there has been evidence that the eye may be a possible route of transmission for the SARS-CoV-2 virus (as well as other viruses). Though there is some reports from the use of therapeutic contact lenses to combat COVID-19, the possible use of the SCL to serve as a drug-dissolving device in viral diseases such as COVID-19 may present a future development opportunity.
As the examples above have shown, the development of next-generation smart contact lens technology is not simply a field of bioelectronics, but rather a complex interdisciplinary effort that includes the development of biocompatible materials; development of intuitive interfaces; and the development of integration technologies capable of conducting smart contact lens research.
Michael is the author of three Royal Society of Chemistry books:
Nano-society: pushing the limits of technology,
Nanotechnology: the future is tinyand
Nanoengineering: the skills and tools that make technology invisible
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