Activity of Retinal Neurons Can Be Modulated by Tunable Near-Infrared Nanoparticle Sensors

Photoreceptor-Mimetic Microflowers for Restoring Light Responses in Degenerative Retina through a 2D Nanopetal/Cell Biointerface

Retinitis pigmentosa is the main cause of inherited human blindness and is associated with dysfunctional photoreceptors (PRs). Compared with traditional methods, optoelectronic stimulation can better preserve the structural integrity and genetic content of the retina. However, enhancing the spatiotemporal accuracy of stimulation is challenging. Quantum dot-doped ZnIn2S4 microflowers (MF) are utilized to construct a biomimetic photoelectric interface with a 0D/3D heterostructure, aiming to restore the light response in PR-degenerative mice. The MF bio interface has dimensions similar to those of natural PRs and can be distributed within the curved spatial region of the retina, mimicking cellular dispersion. The soft 2D nano petals of the MF provide a large specific surface area for photoelectric activation and simulate the flexibility interfacing between cells. This bio interface can selectively restore the light responses of seven types of retina ganglion cells that encode brightness. The distribution of responsive cells forms a pattern similar to that of normal mice, which may reflect the generation of the initial "neural code" in the degenerative retina. Patch-clamp recordings indicate that the bio interface can induce spiking and postsynaptic currents at the single-neuron level. The results will shed light on the development of a potential bionic subretinal prosthetic toolkit for visual function restoration.

High-Performance Graphene Flexible Sensors for Pulse Monitoring and Human-Machine Interaction

Flexible sensors are of great interest due to their potential applications in human physiological signal monitoring, wearable devices, and healthcare. However, sensor devices employed for cardiovascular testing are normally bulky and expensive, which hamper wearability and point-of-care use. Herein, we report a simple method for preparing multifunctional flexible sensors using hydrazine hydrate (N2H4·H2O) as the reducing agent, graphene as the active material, and polyethylene (PE) tape as the encapsulation material. The flexible sensor produced with this method has a low detection limit of 100 mg, a fast response and recovery time of 40 and 20 ms, and shows no performance degradation even after up to 30,000 motion cycles. The sensors we have developed are capable of monitoring the pulse with relative accuracy, which presents an opportunity to replace bulky devices and normalize cardiovascular testing in the future. In order to further broaden the application field, the sensor is installed as a sensor array to recognize objects of different weights and shapes, showing that the sensor has excellent application potential in wearable artificial intelligence.

Graphdiyne as a Highly Efficient and Neuron-Targeted Photothermal Transducer for in Vivo Neuromodulation

Photothermal modulation of neural activity offers a promising approach for understanding brain circuits and developing therapies for neurological disorders. However, the low neuron selectivity and inefficient light-to-heat conversion of existing photothermal nanomaterials significantly limit their potential for neuromodulation. Here, we report that graphdiyne (GDY) can be developed into an efficient neuron-targeted photothermal transducer for in vivo modulation of neuronal activity through rational surface functionalization. We functionalize GDY with polyethylene glycol (PEG) through noncovalent hydrophobic interactions, followed by antibody conjugation to specifically target the temperature-sensitive transient receptor potential cation channel subfamily V member 1 (TRPV1) on the surface of neural cells. The nanotransducer not only exhibits high photothermal conversion efficiency in the near-infrared region but also shows great TRPV1-targeting capability. This enables photothermal activation of TRPV1, leading to neurotransmitter release in cells and modulation of neural firing in living mice. With its precision and selectivity, the GDY-based transducer provides an innovative avenue for understanding brain function and developing therapeutic strategies for neurodegenerative diseases.

Nanoparticle-based optical interfaces for retinal neuromodulation: a review

Degeneration of photoreceptors in the retina is a leading cause of blindness, but commonly leaves the retinal ganglion cells (RGCs) and/or bipolar cells extant. Consequently, these cells are an attractive target for the invasive electrical implants colloquially known as "bionic eyes." However, after more than two decades of concerted effort, interfaces based on conventional electrical stimulation approaches have delivered limited efficacy, primarily due to the current spread in retinal tissue, which precludes high-acuity vision. The ideal prosthetic solution would be less invasive, provide single-cell resolution and an ability to differentiate between different cell types. Nanoparticle-mediated approaches can address some of these requirements, with particular attention being directed at light-sensitive nanoparticles that can be accessed via the intrinsic optics of the eye. Here we survey the available known nanoparticle-based optical transduction mechanisms that can be exploited for neuromodulation. We review the rapid progress in the field, together with outstanding challenges that must be addressed to translate these techniques to clinical practice. In particular, successful translation will likely require efficient delivery of nanoparticles to stable and precisely defined locations in the retinal tissues. Therefore, we also emphasize the current literature relating to the pharmacokinetics of nanoparticles in the eye. While considerable challenges remain to be overcome, progress to date shows great potential for nanoparticle-based interfaces to revolutionize the field of visual prostheses.

A tissue-engineered neural interface with photothermal functionality

Neural interfaces are well-established as a tool to understand the behaviour of the nervous system via recording and stimulation of living neurons, as well as serving as neural prostheses. Conventional neural interfaces based on metals and carbon-based materials are generally optimised for high conductivity; however, a mechanical mismatch between the interface and the neural environment can significantly reduce long-term neuromodulation efficacy by causing an inflammatory response. This paper presents a soft composite material made of gelatin methacryloyl (GelMA) containing graphene oxide (GO) conjugated with gold nanorods (AuNRs). The soft hydrogel presents stiffness within the neural environment range of modulus below 5 kPa, while the AuNRs, when exposed to light in the near infrared range, provide a photothermal response that can be used to improve the spatial and temporal precision of neuromodulation. These favourable properties can be maintained at safer optical power levels when combined with electrical stimulation. In this paper we provide mechanical and biological characterization of the optical activity of the GO-AuNR composite hydrogel. The optical functionality of the material has been evaluated via photothermal stimulation of explanted rat retinal tissue. The outcomes achieved with this study encourage further investigation into optical and electrical costimulation parameters for a range of biomedical applications.