Enhancing surface immobilization of bioactive molecules via a silica nanoparticle based coating

Investigation of a chondroitin sulfate-based bioactive coating for neural interface applications

Invasive neural implants allow for high-resolution bidirectional communication with the nervous tissue and have demonstrated the ability to record neural activity, stimulate neurons, and sense neurochemical species with high spatial selectivity and resolution. However, upon implantation, they are exposed to a foreign body response which can disrupt the seamless integration of the device with the native tissue and lead to deterioration in device functionality for chronic implantation. Modifying the device surface by incorporating bioactive coatings has been a promising approach to camouflage the device and improve integration while maintaining device performance. In this work, we explored the novel application of a chondroitin sulfate (CS) based hydrophilic coating, with anti-fouling and neurite-growth promoting properties for neural recording electrodes. CS-coated samples exhibited significantly reduced protein-fouling in vitro which was maintained for up to 4-weeks. Cell culture studies revealed a significant increase in neurite attachment and outgrowth and a significant decrease in microglia attachment and activation for the CS group as compared to the control. After 1-week of in vivo implantation in the mouse cortex, the coated probes demonstrated significantly lower biofouling as compared to uncoated controls. Like the in vitro results, increased neuronal population (neuronal nuclei and neurofilament) and decreased microglial activation were observed. To assess the coating's effect on the recording performance of silicon microelectrodes, we implanted coated and uncoated electrodes in the mouse striatum for 1 week and performed impedance and recording measurements. We observed significantly lower impedance in the coated group, likely due to the increased wettability of the coated surface. The peak-to-peak amplitude and the noise floor levels were both lower in the CS group compared to the controls, which led to a comparable signal-to-noise ratio between the two groups. The overall single unit yield (% channels recording a single unit) was 74% for the CS and 67% for the control group on day 1. Taken together, this study demonstrates the effectiveness of the polysaccharide-based coating in reducing biofouling and improving biocompatibility for neural electrode devices.

Improving the Biocompatibility and Functionality of Neural Interface Devices with Silica Nanoparticles

ConspectusNeural interface technologies enable bidirectional communication between the nervous system and external instrumentation. Advancements in neural interface devices not only open new frontiers for neuroscience research, but also hold great promise for clinical diagnosis, therapy, and rehabilitation for various neurological disorders. However, the performance of current neural electrode devices, often termed neural probes, is far from satisfactory. Glial scarring, neuronal degeneration, and electrode degradation eventually cause the devices to lose their connection with the brain. To improve the chronic performance of neural probes, efforts need to be made on two fronts: enhancing the physiochemical properties of the electrode materials and mitigating the undesired host tissue response.In this Account, we discuss our efforts in developing silica-nanoparticle-based (SiNP) coatings aimed at enhancing neural probe electrochemical properties and promoting device-tissue integration. Our work focuses on three approaches:(1) SiNPs' surface texturization to enhance biomimetic protein coatings for promoting neural integration. Through covalent immobilization, SiNP introduces biologically relevant nanotopography to neural probe surfaces, enhancing neuronal cell attachments and inhibiting microglia. The SiNP base coating further increases the binding density and stability of bioactive molecules such as L1CAM and facilitates the widespread dissemination of biomimetic coatings. (2) Doping SiNPs into conductive polymer electrode coatings improves the electrochemical properties and stability. As neural interface devices are moving to subcellular sizes to escape the immune response and high electrode site density to increase spatial resolution, the electrode sites need to be very small. The smaller electrode size comes at the cost of a high electrode impedance, elevated thermal noise, and insufficient charge injection capacity. Electrochemically deposited conductive polymer films reduce electrode impedance but do not endure prolonged electrical cycling. When incorporated into conductive polymer coatings as a dopant, the SiNP provides structural support for the polymer thin films, significantly increasing their stability and durability. Low interfacial impedance maintained by the conducting polymer/SiNP composite is critical for extended electrode longevity and effective charge injection in chronic neural stimulation applications. (3) Porous nanoparticles are used as drug carriers in conductive polymer coatings for local drug/neurochemical delivery. When triggered by external electrical stimuli, drug molecules and neurochemicals can be released in a controlled manner. Such precise focal manipulation of cellular and vascular behavior enables us to probe brain circuitry and develop therapeutic applications.We foresee tremendous opportunities for further advancing the functionality of SiNP coatings by incorporating new nanoscale components and integrating the coating with other design strategies. With an enriched nanoscale toolbox and optimized design strategies, we can create customizable multifunctional and multimodal neural interfaces that can operate at multiple spatial levels and seamlessly integrate with the host tissue for extended applications.

Itaconic Acid Cross-Linked Biomolecule Immobilization Approach on Amine-Functionalized Silica Nanoparticles for Highly Sensitive Enzyme-Linked Immunosorbent Assay (ELISA)

Biomolecule immobilization on nanomaterials is attractive for biosensors since it enables the capture of a higher concentration of bioreceptor units while also serving as a transduction element. The technique could enhance the accuracy, specificity, and sensitivity of the analytical measurements of biomolecules. However, it was found that the limitation in chemically binding biomolecules on nanoparticle surfaces could only cross-link between the C-terminal and N-terminal. Here, we report the facile one-step synthesis of amine-functionalized silica nanoparticles (AFSNPs). (3-Aminopropyl)triethoxysilane was used as a precursor to modify the functional surface of nanoparticles via the Stöber process. The biomolecules were immobilized to the AFSNPs through itaconic acid, a novel cross-linker that binds between the N-terminal and N-terminal and potentially improves proteins and nucleic acid immobilization onto the nanoparticle surface. The newly developed immobilization approach on AFSNPs for biomolecular detection enhanced the efficiency of ELISA, resulting in increased sensitivity. It might also be easily used to identify different pathogens for clinical diagnostics.

Nanotopography-enhanced biomimetic coating maintains bioactivity after weeks of dry storage and improves chronic neural recording

We developed a nanoparticle base layer technology capable of maintaining the bioactivity of protein-based neural probe coating intended to improve neural recording quality. When covalently bound on thiolated nanoparticle (TNP) modified surfaces, neural adhesion molecule L1 maintained bioactivity throughout 8 weeks of dry storage at room temperature, while those bound to unmodified surfaces lost 66% bioactivity within 3 days. We tested the TNP + L1 coating in mouse brains on two different neural electrode arrays after two different dry storage durations (3 and 28 days). The results show that dry-stored coating is as good as the freshly prepared, and even after 28 days of storage, the number of single units per channel and signal-to-noise ratio of the TNP + L1 coated arrays were significantly higher by 32% and 40% respectively than uncoated controls over 16 weeks. This nanoparticle base layer approach enables the dissemination of biomolecule-functionalized neural probes to users worldwide and may also benefit a broad range of applications that rely on surface-bound biomolecules.

Optically traceable PLGA-silica nanoparticles for cell-triggered doxorubicin delivery

Fluorescent silica nanoparticles with a polymer shell of poly (D, L-lactide-co-glycolide) (PLGA) can provide traceable cell-triggered delivery of the anticancer drug doxorubicin (DOX), protecting the cargo while in transit and releasing it only intracellularly. PLGA with 50:50 lactide:glycolide ratio was grown by surface-initiated ring-opening polymerization (ROP) from silica nanoparticles of ca. 50 nm diameter, doped with a perylenediimide (PDI) fluorescent dye anchored to the silica structure. After loading DOX, release from the core-shell particles was evaluated in solution at physiological pH (7.4), and in human breast cancer cells (MCF-7) after internalization. The hybrid silica-PLGA nanoparticles can accommodate a large cargo of DOX, and the release in solution (PBS) due to PLGA hydrolysis is negligible for at least 72 h. However, once internalized in MCF-7 cells, the nanoparticles release the DOX cargo by degradation of the PLGA. Accumulation of DOX in the nucleus causes cell apoptosis, with the drug-loaded nanoparticles found to be as potent as free DOX. Our fluorescently traceable hybrid silica-PLGA nanoparticles with cell-triggered cargo release offer excellent prospects for the controlled delivery of anticancer drugs, protecting the cargo while in transit and efficiently releasing the drug once inside the cell.

Effects of neuronal cell adhesion molecule L1 and nanoparticle surface modification on microglia

Microelectrode arrays for neural recording suffer from low yield and stability partly due to the inflammatory host responses. A neuronal cell adhesion molecule L1 coating has been shown to promote electrode-neuron integration, reduce microglia activation and improve recording. Coupling L1 to surface via a nanoparticle (NP) base layer further increased the protein surface density and stability. However, the exact L1-microglia interaction in these coatings has not been studied. Here we cultured primary microglia on L1 modified surfaces (with and without NP) and characterized microglia activation upon phorbol myristate acetate (PMA) and lipopolysaccharide (LPS) stimulation. Results showed L1 coatings reduced microglia's superoxide production in response to PMA and presented intrinsic antioxidant properties. Meanwhile, L1 decreased iNOS, NO, and pro-inflammatory cytokines (TNF alpha, IL-6, IL-1 beta), while increased anti-inflammatory cytokines (TGF beta 1, IL-10) in LPS stimulated microglia. Furthermore, L1 increased Arg-1 expression and phagocytosis upon LPS stimulation. Rougher NP surface showed lower number of microglia attached per area than their smooth counterpart, lower IL-6 release and superoxide production, and higher intrinsic reducing potential. Finally, we examined the effect of L1 and nanoparticle modifications on microglia response in vivo over 8 weeks with 2-photon imaging. Microglial coverage on the implant surface was found to be lower on the L1 modified substrates relative to unmodified, consistent with the in vitro observation. Our results indicate L1 significantly reduces superoxide production and inflammatory response of microglia and promotes wound healing, while L1 immobilization via a nanoparticle base layer brings added benefit without adverse effects. STATEMENT OF SIGNIFICANCE: Surface modification of microelectrode arrays with L1 has been shown to reduce microglia coverage on neural probe surface in vivo and improves neural recording, but the specific mechanism of action is not fully understood. The results in this study show that surface bound L1 reduces superoxide production from cultured microglia via direct reduction reaction and signaling pathways, increases anti-inflammatory cytokine release and phagocytosis in response to PMA or LPS stimulation. Additionally, roughening the surface with nanoparticles prior to L1 immobilization further increased the benefit of L1 in reducing microglia activation and oxidative stress. Together, our findings shed light on the mechanisms of action of nanotextured and neuroadhesive neural implant coatings and guide future development of seamless tissue interface.

Surface Area and Local Curvature: Why Roughness Improves the Bioactivity of Neural Implants

While roughening the surface of neural implants has been shown to significantly improve their performance, the mechanism for this improvement is not understood, preventing systematic optimization of surfaces. Specifically, prior work has shown that the cellular response to a surface can be significantly enhanced by coating the implant surface with inorganic nanoparticles and neuroadhesion protein L1, and this improvement occurs even when the surface chemistry is identical between the nanoparticle-coated and uncoated electrodes, suggesting the critical importance of surface topography. Here, we use transmission electron microscopy to characterize the topography of bare and nanoparticle-coated implants across 7 orders of magnitude in size, from the device scale to the atomic scale. The results reveal multiscale roughness, which cannot be adequately described using conventional roughness parameters. Indeed, the topography is nearly identical between the two samples at the smallest scales and also at the largest scales but vastly different in the intermediate scales, especially in the range of 5-100 nm. Using a multiscale topography analysis, we show that the coating causes a 76% increase in the available surface area for contact and an order-of-magnitude increase in local surface curvature at characteristic sizes corresponding to specific biological structures. These are correlated with a 75% increase in bound proteins on the surface and a 134% increase in neurite outgrowth. The present investigation presents a framework for analyzing the scale-dependent topography of medical device-relevant surfaces, and suggests the most critical size scales that determine the biological response to implanted materials.

Cell-membrane-inspired polymers for constructing biointerfaces with efficient molecular recognition

Fabrication of devices that accurately recognize, detect, and separate target molecules from mixtures is a crucial aspect of biotechnology for applications in medical, pharmaceutical, and food sciences. This technology has also been recently applied in solving environmental and energy-related problems. In molecular recognition, biomolecules are typically complexed with a substrate, and specific molecules from a mixture are recognized, captured, and reacted. To increase sensitivity and efficiency, the activity of the biomolecules used for capture should be maintained, and non-specific reactions on the surface should be prevented. This review summarizes polymeric materials that are used for constructing biointerfaces. Precise molecular recognition occurring at the surface of cell membranes is fundamental to sustaining life; therefore, materials that mimic the structure and properties of this particular surface are emphasized in this article. The requirements for biointerfaces to eliminate nonspecific interactions of biomolecules are described. In particular, the major issue of protein adsorption on biointerfaces is discussed by focusing on the structure of water near the interface from a thermodynamic viewpoint; moreover, the structure of polymer molecules that control the water structure is considered. Methodologies enabling stable formation of these interfaces on material surfaces are also presented.

Bio-integrative design of the neural tissue-device interface

Neural implants enable bidirectional communications with nervous tissue and have demonstrated tremendous potential in research and clinical applications. To obtain high fidelity and stable information exchange, we need to minimize the undesired host responses and achieve intimate neuron-device interaction. This paper highlights the key bio-integrative strategies aimed at seamless integration through intelligent device designs to minimize the immune responses, as well as incorporate bioactive elements to actively modulate cellular reactions. These approaches span from surface modification and bioactive agent delivery, to biomorphic and biohybrid designs. Many of these strategies have shown effectiveness in functional outcome measures, others are exploratory but with fascinating potentials. The combination of bio-integrative strategies may synergistically promote the next generation of neural interfaces.

A multiplexed phospholipid membrane platform for curvature sensitive protein screening

The curvature of lipid membranes plays a key role in many relevant biological processes such as membrane trafficking, vesicular budding and host-virus interactions. In vitro studies on the membrane curvature of simplified biomimetic models in the nanometer range are challenging, due to their complicated nanofabrication processes. In this work, we propose a simple and low-cost platform for curvature sensitive protein screening, prepared through scanning probe lithography (SPL) methods, where lipid bilayer patches of different compositions can be multiplexed onto substrate areas with tailored local curvature. The curvature is imposed by anchoring nanoparticles of the desired size to the substrate prior to lithography. As a proof of principle, we demonstrate that a positive curvature membrane sensitive protein derived from the BAR domain of Nadrin2 binds selectively to lipid patches patterned on substrate areas coated with 100 nm nanoparticles. The platform opens up a path for screening curvature-dependent protein-membrane interaction studies by providing a flexible and easy to prepare substrate with control over lipid composition and membrane curvature.

Nanoparticle and Biomolecule Surface Modification Synergistically Increases Neural Electrode Recording Yield and Minimizes Inflammatory Host Response

Due to their ability to interface with neural tissues, neural electrodes are the key tool used for neurophysiological studies, electrochemical detection, brain computer interfacing, and countless neuromodulation therapies and diagnostic procedures. However, the long-term applications of neural electrodes are limited by the inflammatory host tissue response, decreasing detectable electrical signals, and insulating the device from the native environment. Surface modification methods are proposed to limit these detrimental responses but each has their own limitations. Here, a combinatorial approach is presented toward creating a stable interface between the electrode and host tissues. First, a thiolated nanoparticle (TNP) coating is utilized to increase the surface area and roughness. Next, the neural adhesion molecule L1 is immobilized to the nanoparticle modified substrate. In vitro, the combined nanotopographical and bioactive modifications (TNP+L1) elevate the bioactivity of L1, which is maintained for 28 d. In vivo, TNP+L1 modification improves the recording performance of the neural electrode arrays compared to TNP or L1 modification alone. Postmortem histology reveals greater neural cell density around the TNP+L1 coating while eliminating any inflammatory microglial encapsulation after 4 weeks. These results demonstrate that nanotopographical and bioactive modifications synergistically produce a seamless neural tissue interface for chronic neural implants.

Binding enhancements of antibody functionalized natural and synthetic fibers

Development of low cost biosensing using convenient and environmentally benign materials is important for wide adoption and ultimately improved healthcare and sustainable development. Immobilized antibodies are often incorporated as an essential biorecognition element in point-of-care biosensors but these proteins are costly. We present a strategy of combining convenient and low-cost surface functionalization approaches for increasing the overall binding activity of antibody functionalized natural and synthetic fibers. We demonstrate a simple one-step in situ silica NP growth protocol for increasing the surface area available for functionalization on cotton and polyester fabrics as well as on nanoporous cellulose substrates. Comparing this effect with the widely adopted and low cost plant-based polyphenol coating to enhance antibody immobilization, we find that both approaches can similarly increase overall surface activity, and we illustrate conditions under which the two approaches can produce an additive effect. Furthermore, we introduce co-immobilization of antibodies with a sacrificial “steric helper” protein for further enhancing surface activities. In combination, several hundred percent higher activities compared to physical adsorption can be achieved while maintaining a low amount of antibodies used, thus paving a practical path towards low cost biosensing.

Cotton, nanoporous cellulose and polyester fabric surfaces are functionalized with combinations of in situ grown silica NPs, polyphenol coating, and protein co-immobilization to enhance surface area, antibody binding efficiency, and biosensing.

Elucidating the Surface Functionality of Biomimetic RGD Peptides Immobilized on Nano-P(3HB-co-4HB) for H9c2 Myoblast Cell Proliferation

Biomaterial scaffolds play crucial role to promote cell proliferation and foster the regeneration of new tissues. The progress in material science has paved the way for the generation of ingenious biomaterials. However, these biomaterials require further optimization to be effectively used in existing clinical treatments. It is crucial to develop biomaterials which mimics structure that can be actively involved in delivering signals to cells for the formation of the regenerated tissue. In this research we nanoengineered a functional scaffold to support the proliferation of myoblast cells. Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] copolymer is chosen as scaffold material owing to its desirable mechanical and physical properties combined with good biocompatibility, thus eliciting appropriate host tissue responses. In this study P(3HB-co-4HB) copolymer was biosynthesized using Cupriavidus malaysiensis USMAA1020 transformant harboring additional PHA synthase gene, and the viability of a novel P(3HB-co-4HB) electrospun nanofiber scaffold, surface functionalized with RGD peptides, was explored. In order to immobilize RGD peptides molecules onto the P(3HB-co-4HB) nanofibers surface, an aminolysis reaction was performed. The nanoengineered scaffolds were characterized using SEM, organic elemental analysis (CHN analysis), FTIR, surface wettability and their in vitro degradation behavior was evaluated. The cell culture study using H9c2 myoblast cells was conducted to assess the in vitro cellular response of the engineered scaffold. Our results demonstrated that nano-P(3HB-co-4HB)-RGD scaffold possessed an average fiber diameter distribution between 200 and 300 nm, closely biomimicking, from a morphological point of view, the structural ECM components, thus acting as potential ECM analogs. This study indicates that the surface conjugation of biomimetic RGD peptide to the nano-P(3HB-co-4HB) fibers increased the surface wettability (15 ± 2°) and enhanced H9c2 myoblast cells attachment and proliferation. In summary, the study reveals that nano-P(3HB-co-4HB)-RGD scaffold can be considered a promising candidate to be further explored as cardiac construct for building cardiac construct.

Neuroadhesive protein coating improves the chronic performance of neuroelectronics in mouse brain

Intracortical microelectrodes are being developed to both record and stimulate neurons to understand brain circuitry or restore lost functions. However, the success of these probes is hampered partly due to the inflammatory host tissue responses to implants. To minimize the foreign body reactions, L1, a brain derived neuronal specific cell adhesion molecule, has been covalently bound to the neural electrode array surface. Here we evaluated the chronic recording performance of L1-coated silicon based laminar neural electrode arrays implanted into V1m cortex of mice. The L1 coating enhanced the overall visually evoked single-unit (SU) yield and SU amplitude, as well as signal-to-noise-ratio (SNR) in the mouse brain compared to the uncoated arrays across the 0-1500 μm depth. The improvement in recording is most dramatic in the hippocampus region, where the control group showed severe recording yield decrease after one week, while the L1 implants maintained a high SU yield throughout the 16 weeks. Immunohistological analysis revealed significant increases of axonal and neuronal density along with significantly lowered microglia activation around the L1 probe after 16 weeks. These results collectively confirm the effectiveness of L1 based biomimetic coating on minimizing inflammatory tissue response and improving neural recording quality and longevity. Improving chronic recording will benefit the brain-computer interface technologies and neuroscience studies involving chronic tracking of neural activities.

A superoxide scavenging coating for improving tissue response to neural implants

The advancement of neural prostheses requires implantable neural electrodes capable of electrically stimulating or recording signals from neurons chronically. Unfortunately, the implantation injury and presence of foreign bodies lead to chronic inflammation, resulting in neuronal death in the vicinity of electrodes. A key mediator of inflammation and neuronal loss are reactive oxygen and nitrogen species (RONS). To mitigate the effect of RONS, a superoxide dismutase mimic compound, manganese(III) meso-tetrakis-(N-(2-aminoethyl)pyridinium-2-yl) porphyrin (iSODm), was synthesized to covalently attach to the neural probe surfaces. This new compound showed high catalytic superoxide scavenging activity. In microglia cell line cultures, the iSODm coating effectively reduced superoxide production and altered expression of iNOS, NADPH oxidase, and arginase. After 1 week of implantation, iSODm coated electrodes showed significantly lower expression of markers for oxidative stress immediately adjacent to the electrode surface, as well as significantly less neurons undergoing apoptosis. STATEMENT OF SIGNIFICANCE: One critical challenge in the translation of neural electrode technology to clinically viable devices for brain computer interface or deep brain stimulation applications is the chronic degradation of the device performance due to neuronal degeneration around the implants. One of the key mediators of inflammation and neuronal degeneration is reactive oxygen and nitrogen species released by injured neurons and inflammatory microglia. This research takes a biomimetic approach to synthesize a compound having similar reactivity as superoxide dismutase, which can catalytically scavenge reactive oxygen and nitrogen species, thereby reducing oxidative stress and decreasing neuronal degeneration. By immobilizing the compound covalently on the surface of neural implants, we show that the neuronal degeneration and oxidative stress around the implants is significantly reduced.

Nanoparticle Doped PEDOT for Enhanced Electrode Coatings and Drug Delivery

In order to address material limitations of biologically interfacing electrodes, modified silica nanoparticles are utilized as dopants for conducting polymers. Silica precursors are selected to form a thiol modified particle (TNP), following which the particles are oxidized to sulfonate modified nanoparticles (SNPs). The selective inclusion of hexadecyl trimethylammonium bromide allows for synthesis of both porous and nonporous SNPs. Nonporous nanoparticle doped polyethylenedioxythiophene (PEDOT) films possess low interfacial impedance, high charge injection (4.8 mC cm-2 ), and improved stability under stimulation compared to PEDOT/poly(styrenesulfonate). Porous SNP dopants can serve as drug reservoirs and greatly enhance the capability of conducting polymer-based, electrically controlled drug release technology. Using the SNP dopants, drug loading and release is increased up to 16.8 times, in addition to greatly expanding the range of drug candidates to include both cationic and electroactive compounds, all while maintaining their bioactivity. Finally, the PEDOT/SNP composite is capable of precisely modulating neural activity in vivo by timed release of a glutamate receptor antagonist from coated microelectrode sites. Together, this work demonstrates the feasibility and potential of doping conducting polymers with engineered nanoparticles, creating countless options to produce composite materials for enhanced electrical stimulation, neural recording, chemical sensing, and on demand drug delivery.

Gene-Embedded Nanostructural Biotic-Abiotic Optoelectrode Arrays Applied for Synchronous Brain Optogenetics and Neural Signal Recording

Optogenetics is a recently established neuromodulation technique in which photostimulation is used to manipulate neurons with high temporal and spatial precision. However, sequential genetic and optical insertion with double brain implantation tends to cause excessive tissue damage. In addition, the incorporation of light-sensitive genes requires the utilization of viral vectors, which remains a safety concern. Here, by combining device fabrication design, nanotechnology, and cell targeting technology, we developed a new gene-embedded optoelectrode array for neural implantation to enable spatiotemporal electroporation (EP) for gene delivery/transfection, photomodulation, and synchronous electrical monitoring of neural signals in the brain via one-time implantation. A biotic-abiotic neural interface (called PG) composed of reduced graphene oxide and conductive polyelectrolyte 3,4-ethylenedioxythiophene-modified amphiphilic chitosan was developed to form a nanostructural hydrogel with assembled nanodomains for encapsulating nonviral gene vectors (called PEI-NT-pDNA) formulated by neurotensin (NT) and polyethylenimine (PEI)-coupled plasmid DNA (pDNA). The PG can maintain high charge storage ability to respond to a minimal current of 125 μA for controllable gene delivery. The in vitro analysis of PG-PEI-NT-pDNA on the microelectrode array chip showed that the microelectrodes provided electrically inductive electropermeabilization, which permitted gene transfection into localized rat adrenal pheochromocytoma cells with a strong green fluorescent protein expression that was up to 8-fold higher than that in nontreated cells. Furthermore, the in vivo implantation enabled on-demand spatiotemporal gene transfection to neurons with 10-fold enhancement of targeting ability compared with astrocytes. Finally, using the real optogenetic opsin channelrhodopsin-2, the flexible neural probe incorporated with an optical waveguide fiber displayed photoevoked extracellular spikes in the thalamic ventrobasal region after focal EP for only 7 days, which provided a proof of concept for the use of photomodulation to facilitate neural therapies.