Dual Behavior Regulation: Tether-Free Deep-Brain Stimulation by Photothermal and Upconversion Hybrid Nanoparticles

Stimuli-Responsive Barcode Probe-Mediated Self-Powered Biosensor Enables Dual-Signal Amplification for Ultrasensitive Detection of Circulating Tumor Cells

Circulating tumor cells (CTCs) serve as valuable biomarkers for early cancer diagnosis in low abundance in the bloodstream. Therefore, the development of a biosensor for the ultrasensitive detection of CTCs is imperative. Herein, an enzymatic biofuel cell (EBFC)-based self-powered biosensor has been developed in which the recognition of CTCs with a stimuli-responsive barcode probe (SRBP) triggers the opening of a circuit "lock" and further activates the DNA dual-signal amplification, achieving ultrasensitive detection of CTCs. The SRBP is fabricated based on the hyaluronic acid (HA)-modified ZIF-8 framework, which is functionalized with Trigger and H2 at a certain ratio and further connected on magnetic beads via the hybridization between Trigger and the aptamer (Apt) of HepG2 cells. The specific recognition of target CTCs, hepatocellular carcinoma cell line G2 (HepG2) cells, by Apt results in the release of SRBP. Upon the stimuli of glutathione (GSH) under weakly acidic conditions (pH 5-6), ZIF-8 is disintegrated, leading to the releasing of Zn2+, accompanied by the liberation of H2 and Trigger. As a result, the dual-signal amplification, that is, DNAzyme-mediated cyclic cleavage of substrate-linked SiO2 (Sub-SiO2) on the bioanode and catalytic hairpin assembly (CHA) on the biocathode, is activated. This self-powered biosensor achieves ultrasensitive detection of HepG2 cells with a detection limit as low as 3 cells/mL and excellent specificity, which exhibits substantial potential for early diagnosis of cancers.

Neural interfaces: Bridging the brain to the world beyond healthcare

Neural interfaces, emerging at the intersection of neurotechnology and urban planning, promise to transform how we interact with our surroundings and communicate. By recording and decoding neural signals, these interfaces facilitate direct connections between the brain and external devices, enabling seamless information exchange and shared experiences. Nevertheless, their development is challenged by complexities in materials science, electrochemistry, and algorithmic design. Electrophysiological crosstalk and the mismatch between electrode rigidity and tissue flexibility further complicate signal fidelity and biocompatibility. Recent closed-loop brain-computer interfaces, while promising for mood regulation and cognitive enhancement, are limited by decoding accuracy and the adaptability of user interfaces. This perspective outlines these challenges and discusses the progress in neural interfaces, contrasting non-invasive and invasive approaches, and explores the dynamics between stimulation and direct interfacing. Emphasis is placed on applications beyond healthcare, highlighting the need for implantable interfaces with high-resolution recording and stimulation capabilities.

"Photo-Thermo-Electric" Dental Implant for Anti-Infection and Enhanced Osteoimmunomodulation

The dental implant market has experienced explosive growth, owing to the widespread acceptance of implants as the core of oral rehabilitation. Clinically, achieving simultaneous anti-infective effects and rapid osseointegration is a crucial but challenging task for implants. The demand for implants with long-term broad-spectrum antibacterial and immune-osteogenic properties is growing. Existing methods are limited by a lack of safety, efficiency, short-lasting anti-infective ability, and inadequate consideration of the immunomodulatory effects on osteogenesis. Herein, a ZnO/black TiO2-x heterojunction surface structure was designed as a near-infrared (NIR) light-responsive nanofilm immobilized on a titanium (Ti) implant surface. This nanofilm introduces abundant oxygen vacancies and heterojunctions, which enhance the photothermal and photoelectric abilities of Ti implants under NIR illumination by narrowing the band gap and improving interfacial charge transfer. The "photo-thermo-electric" implant exhibits excellent broad-spectrum antibacterial efficacy against three dental pathogenic bacteria (Porphyromonas gingivalis, Fusobacterium nucleatum, and Staphylococcus aureus, >99.4%) by destroying the bacterial membrane and increasing the production of intracellular reactive oxygen species. Additionally, the implant can effectively eliminate mature multispecies biofilms and kill bacteria inside the biofilms under NIR irradiation. Meanwhile, this implant can also induce the pro-regenerative transformation of macrophages and promote osteoblast proliferation and differentiation. Moreover, in vivo results confirmed the superior antibacterial and osteoimmunomodulatory properties of this dental implant. RNA sequencing revealed that the underlying osteogenic mechanisms involve activation of the Wnt/β-catenin signaling pathway and bone development. Overall, this versatile "photo-thermo-electric" platform endows implants with anti-infection and bone integration performance simultaneously, which holds great potential for dental implants.

Tetherless Optical Neuromodulation: Wavelength from Orange-red to Mid-infrared

Optogenetics, a technique that employs light for neuromodulation, has revolutionized the study of neural mechanisms and the treatment of neurological disorders due to its high spatiotemporal resolution and cell-type specificity. However, visible light, particularly blue and green light, commonly used in conventional optogenetics, has limited penetration in biological tissue. This limitation necessitates the implantation of optical fibers for light delivery, especially in deep brain regions, leading to tissue damage and experimental constraints. To overcome these challenges, the use of orange-red and infrared light with greater tissue penetration has emerged as a promising approach for tetherless optical neuromodulation. In this review, we provide an overview of the development and applications of tetherless optical neuromodulation methods with long wavelengths. We first discuss the exploration of orange-red wavelength-responsive rhodopsins and their performance in tetherless optical neuromodulation. Then, we summarize two novel tetherless neuromodulation methods using near-infrared light: upconversion nanoparticle-mediated optogenetics and photothermal neuromodulation. In addition, we discuss recent advances in mid-infrared optical neuromodulation.

Functional nanotransducer-mediated wireless neural modulation techniques

Functional nanomaterials have emerged as versatile nanotransducers for wireless neural modulation because of their minimal invasion and high spatiotemporal resolution. The nanotransducers can convert external excitation sources (e.g. NIR light, x-rays, and magnetic fields) to visible light (or local heat) to activate optogenetic opsins and thermosensitive ion channels for neuromodulation. The present review provides insights into the fundamentals of the mostly used functional nanomaterials in wireless neuromodulation including upconversion nanoparticles, nanoscintillators, and magnetic nanoparticles. We further discussed the recent developments in design strategies of functional nanomaterials with enhanced energy conversion performance that have greatly expanded the field of neuromodulation. We summarized the applications of functional nanomaterials-mediated wireless neuromodulation techniques, including exciting/silencing neurons, modulating brain activity, controlling motor behaviors, and regulating peripheral organ function in mice. Finally, we discussed some key considerations in functional nanotransducer-mediated wireless neuromodulation along with the current challenges and future directions.

Unrestricted molecular motions enable mild photothermy for recurrence-resistant FLASH antitumor radiotherapy

Ultrahigh dose-rate (FLASH) radiotherapy is an emerging technology with excellent therapeutic effects and low biological toxicity. However, tumor recurrence largely impede the effectiveness of FLASH therapy. Overcoming tumor recurrence is crucial for practical FLASH applications. Here, we prepared an agarose-based thermosensitive hydrogel containing a mild photothermal agent (TPE-BBT) and a glutaminase inhibitor (CB-839). Within nanoparticles, TPE-BBT exhibits aggregation-induced emission peaked at 900 nm, while the unrestricted molecular motions endow TPE-BBT with a mild photothermy generation ability. The balanced photothermal effect and photoluminescence are ideal for phototheranostics. Upon 660-nm laser irradiation, the temperature-rising effect softens and hydrolyzes the hydrogel to release TPE-BBT and CB-839 into the tumor site for concurrent mild photothermal therapy and chemotherapy, jointly inhibiting homologous recombination repair of DNA. The enhanced FLASH radiotherapy efficiently kills the tumor tissue without recurrence and obvious systematic toxicity. This work deciphers the unrestricted molecular motions in bright organic fluorophores as a source of photothermy, and provides novel recurrence-resistant radiotherapy without adverse side effects.

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.

Postoperatively Noninvasive Optogenetic Stimulation via Upconversion Nanoparticles Enhancing Sciatic Nerve Repair

The efficacy of electrical stimulation facilitating peripheral nerve regeneration is evidenced extensively, while the associated secondary damage resulting from repeated electrode invasion and indiscriminate stimulation is inevitable. Here, we present an optogenetics strategy that utilizes upconversion nanoparticles (UCNPs) to convert deeply penetrating near-infrared excitation into blue emission, which activates an adeno-associated virus-encoding ChR2 photoresponsive ion channel on cell membranes. The induced Ca2+ flux, similar to the ion flux in the electrical stimulation approach, efficiently regulates viability and proliferation, secretion of nerve growth factor, and neural function of RSC96 cells. Furthermore, deep near-infrared excitation is harnessed to stimulate autologous Schwann cells in situ via a UCNP-composited scaffold, which enhances nerve sprouting and myelination, consequently promoting functional recovery, electrophysiological restoration, and reinnervation of damaged nerves. This developed postoperatively noninvasive optogenetics strategy presents a novel, minimally traumatic, and enduring therapeutic stimulus to effectively promote peripheral nerve repair.

Control of Luminescence and Interfacial Properties as Perspective for Upconversion Nanoparticles

Near-infrared (NIR) light is highly suitable for studying biological systems due to its minimal scattering and lack of background fluorescence excitation, resulting in high signal-to-noise ratios. By combining NIR light with lanthanide-based upconversion nanoparticles (UCNPs), upconversion is used to generate UV or visible light within tissue. This remarkable property has gained significant research interest over the past two decades. Synthesis methods are developed to produce particles of various sizes, shapes, and complex core-shell architectures and new strategies are explored to optimize particle properties for specific bioapplications. The diverse photophysics of lanthanide ions offers extensive possibilities to tailor spectral characteristics by incorporating different ions and manipulating their arrangement within the nanocrystal. However, several challenges remain before UCNPs can be widely applied. Understanding the behavior of particle surfaces when exposed to complex biological environments is crucial. In applications where deep tissue penetration is required, such as photodynamic therapy and optogenetics, UCNPs show great potential as nanolamps. These nanoparticles can combine diagnostics and therapeutics in a minimally invasive, efficient manner, making them ideal upconversion probes. This article provides an overview of recent UCNP design trends, highlights past research achievements, and outlines potential future directions to bring upconversion research to the next level.

Emerging optogenetics technologies in biomedical applications

Optogenetics is a cutting-edge technology that merges light control and genetics to achieve targeted control of tissue cells. Compared to traditional methods, optogenetics offers several advantages in terms of time and space precision, accuracy, and reduced damage to the research object. Currently, optogenetics is primarily used in pathway research, drug screening, gene expression regulation, and the stimulation of molecule release to treat various diseases. The selection of light-sensitive proteins is the most crucial aspect of optogenetic technology; structural changes occur or downstream channels are activated to achieve signal transmission or factor release, allowing efficient and controllable disease treatment. In this review, we examine the extensive research conducted in the field of biomedicine concerning optogenetics, including the selection of light-sensitive proteins, the study of carriers and delivery devices, and the application of disease treatment. Additionally, we offer critical insights and future implications of optogenetics in the realm of clinical medicine.

AIEgen-Based Covalent Organic Frameworks for Preventing Malignant Ventricular Arrhythmias Via Local Hyperthermia Therapy

The engineering of aggregation-induced emission luminogens (AIEgen) based covalent organic frameworks (COFs), TDTA-COF, BTDTA-COF, and BTDBETA-COF are reported, as hyperthermia agents for inhibiting the occurrence of malignant ventricular arrhythmias (VAs). These AIE COFs exhibit dual functionality, as they not only directly modulate the function and neural activity of stellate ganglion (SG) through local hyperthermia therapy (LHT) but also induce the browning of white fat and improve the neuroinflammation peri-SG microenvironment, which is favorable for inhibiting ischemia-induced VAs. In vivo studies have confirmed that BTDBETA-COF-mediated LHT enhances thermogenesis and browning-related gene expression, thereby serving a synergistic role in combating VAs. Transcriptome analysis of peri-SG adipose tissue reveals a substantial downregulation of inflammatory cytokines, highlighting the potency of BTDBETA-COF-mediated LHT in ameliorating the neuroinflammation peri-SG microenvironment and offering myocardial and arrhythmia protection. The work on AIE COF-based hyperthermia agent for VAs inhibition provides a new avenue for mitigating cardiac sympathetic nerve hyperactivity.