Retinal prostheses: progress toward the next generation implants

In the last decade, various clinical trials proved the capability of visual prostheses, in particular retinal implants, to restore a useful form of vision. These encouraging results promoted the emerging of several strategies for neuronal stimulation aiming at the restoration of sight. Besides the traditional approach based on electrical stimulation through metal electrodes in the different areas of the visual path (e.g., the visual cortex, the lateral geniculate nucleus, the optic nerve, and the retina), novel concepts for neuronal stimulation have been mostly exploited as building blocks of the next generation of retinal implants. This review is focused on critically discussing recent major advancements in the field of retinal stimulation with particular attention to the findings in the application of novel concepts and materials. Last, the major challenges in the field and their clinical implications will be outlined

Validation of a Foldable and Photovoltaic Wide-Field Epiretinal Prosthesis

Inspired by intra ocular lenses, we designed a foldable and wide-field epiretinal prosthesis capable of achieving a wireless photovoltaic stimulation of retinal ganglion cells with a remarkable increase in its retinal coverage and in the number of stimulating pixels. Within a visual angle of 46.9 degrees, it embeds 2215 stimulating pixels, of which 967 are in the central area of 5 mm. It is foldable to limit the scleral incision during implantation and it has a hemispherical shape to remain in tight contact with the retina. We also demonstrate that the prosthesis is not cytotoxic, while accelerated ageing shows a lifetime of at least 2 years. Moreover, it fulfills optical and thermal safety requirements. Last, the flexibility of the fabrication process may allow the production of a hemispherical prosthesis adjusted to the real eye curvature of the patient. These advances provide a solution towards the improvement of both visual acuity and visual field in blind patients

Ultra-Miniaturised CMOS Current Driver for Wireless Biphasic Intracortical Microstimulation

This work shows an ultra-miniaturised and ultralow-power CMOS current driver for biphasic intracortical microstimulation. The CMOS driver is composed of a leakage-based voltage-to-current converter and an H-bridge circuit providing biphasic charge-balanced current stimulation. The circuit has been simulated, fabricated and tested. The current driver consumes 1.87 µW with a supply voltage of 1.8 V, and it occupies a silicon area of 15×12.4 µm 2 . The driver works in linearity in the current range between 23−92 µ

Long COVID-19 in Children: From the Pathogenesis to the Biologically Plausible Roots of the Syndrome

Long Coronavirus disease-19 (COVID-19) refers to the persistence of symptoms related to the infection with severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2). This condition is described as persistent and can manifest in various combinations of signs and symptoms, such as fatigue, headache, dyspnea, depression, cognitive impairment, and altered perception of smells and tastes. Long COVID-19 may be due to long-term damage to different organs-such as lung, brain, kidney, and heart-caused by persisting viral-induced inflammation, immune dysregulation, autoimmunity, diffuse endothelial damage, and micro thrombosis. In this review, we discuss the potential and biologically plausible role of some vitamins, essential elements, and functional foods based on the hypothesis that an individual's dietary status may play an important adjunctive role in protective immunity against COVID-19 and possibly against its long-term consequences

Transient electronics for edible neuroprosthetics

Transient electronics is a recent challenging research field aiming at the realization of functional electronic devices able to disappear in a controlled and predefined manner. Amongst different applications, biomedical devices based on transient technology have raised a lot of interest. Their ability to dissolve within the biological environment, thus avoiding infections due to a prolonged stay and risks related to surgical retrieval, is their main appealing characteristic. In many cases the device relies on silicon-based electronics, but the incorporation of polymers in the design, mostly as flexible substrate or for drug-release purposes, is becoming more and more exploited. Due to the intrinsic versatility of polymeric materials, which potentially allow for a great variety of customized application and fabrication techniques, fully polymer-based transient electronic devices represent the natural step forward in this research area. We therefore intend to contribute to the progress in the field of transient electronics by fabricating probes for neural signal recording based on biocompatible and biodegradable polymers, both as substrate and active material, thus introducing the edible neuroprosthetics concept. In the specific case, we relied on Polycaprolactone (PCL) or Poly Lactic-co-Glycolic Acid (PLGA) as substrate and Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (Pedot:PSS) as conductive conjugated polymer. With these materials as building blocks, a series of passive neural probes were fabricated and implanted in mice brains (visual cortex area) to assess their in-vivo durability. Several time-points (1, 3, 6 and 9 months) have been established for the implants analysis in order to have a better comprehension of the degradation process within the biological environment and the response of the biological environment itself to the insertion of an external object. Preliminary results show that after one month of implantation the astrocytes are visibly activated as expected, whereas there is no evidence of activated microglia. In the near future, implantation of active neural probes will give insight also on the recording capacity of the devices

An Ultra-Miniaturised CMOS Clock and Data Recovery System for Wireless ASK Transmission

Over the years, several clock and data recovery architectures have been proposed for wireless Amplitude Shift Keying (ASK) transmitted signals. State-of-the-art architectures mainly rely on synchronous phase-locked loop circuits or self- sampling systems, both resulting in large area consumption. This work presents a novel CMOS architecture for Clock and Data Recovery (CDR) in miniaturised and wirelessly powered implants. The proposed CDR architecture works at 433.92 MHz and includes: an ASK-demodulator, an on-chip oscillator, a power-on-reset, a control and a recovering block operating in feedback-loop. The ASK-demodulator works for a data rate as high as 6 Mbps and a modulation index in the range of 9-30%. A novel communication protocol is presented for a separated clock and data transmission. The entire CDR architecture occupies 17×89μm2 and consumes 15.01μW while operating with a clock rate of 6 Mbps

A 20 Mbps, 433 MHz RF ASK Transmitter to Inductively Power a Distributed Network of Miniaturised Neural Implants

Simultaneous wireless information and power transfer is an emerging technique in neurotechnology. This work presents an efficient transmitter for both power transfer and downlink data communication to multiple, miniaturised and inductively-powered chips. We designed, implemented and tested a radio-frequency transmitter operating at 433.92 MHz of the industrial, scientific and medical band. A new structure is proposed to efficiently modulate the carrier, exploiting an amplitude-shift keying modulation reaching a data rate as high as 20 Mbps together with a variable modulation index as low as 8%