Near-Unity Light-Matter Interaction in Mid-Infrared van der Waals Metasurfaces.

Accessing mid-infrared radiation is of great importance for a range of applications, including thermal imaging, sensing, and radiative cooling. Here, we study light interaction with hexagonal boron nitride (hBN) nanocavities and reveal strong and tunable resonances across its hyperbolic transition. In addition to conventional phonon-polariton excitations, we demonstrate that the high refractive index of hexagonal boron nitride outside the Reststrahlen band allows enhanced light-matter interactions in deep subwavelength (<λ/15) nanostructures across a broad 7-8 µm range. Emergence and interplay of Fabry-Perot and Mie-like resonances are examined experimentally and theoretically. Near-unity absorption and high quality (Q ≥ 80) resonance interaction in the vicinity of the hBN transverse optical phonon is further observed. Our study provides avenues to design highly efficient and ultracompact structures for controlling mid-infrared radiation and accessing strong light-matter interactions with hBN.

Atomic-Void van der Waals Channel Waveguides.

Layered van der Waals materials allow creating unique atomic-void channels with subnanometer dimensions. Coupling light into these channels may further advance sensing, quantum information, and single molecule chemistries. Here, we examine theoretically limits of light guiding in atomic-void channels and show that van der Waals materials exhibiting strong resonances, excitonic and polaritonic, are ideally suited for deeply subwavelength light guiding. We predict that excitonic transition metal dichalcogenides can squeeze >70% of optical power in just <λ/100 thick channel in the visible and near-infrared. We also show that polariton resonances of hexagonal boron nitride allow deeply subwavelength (<λ/500) guiding in the mid-infrared. We further reveal effects of natural material anisotropy and discuss the influence of losses. Such van der Waals channel waveguides while offering extreme optical confinement exhibit significantly lower loss compared to plasmonic counterparts, thus paving the way to low-loss and deeply subwavelength optics.

Cancer-on-a-Chip for Modeling Immune Checkpoint Inhibitor and Tumor Interactions.

Cancer immunotherapies, including immune checkpoint inhibitor (ICI)-based therapies, have revolutionized cancer treatment. However, patient response to ICIs is highly variable, necessitating the development of methods to quickly assess efficacy. In this study, an array of miniaturized bioreactors has been developed to model tumor-immune interactions. This immunotherapeutic high-throughput observation chamber (iHOC) is designed to test the effect of anti-PD-1 antibodies on cancer spheroid (MDA-MB-231, PD-L1+) and T cell (Jurkat) interactions. This system facilitates facile monitoring of T cell inhibition and reactivation using metrics such as tumor infiltration and interleukin-2 (IL-2) secretion. Status of the tumor-immune interactions can be easily captured within the iHOC by measuring IL-2 concentration using a micropillar array where sensitive, quantitative detection is allowed after antibody coating on the surface of array. The iHOC is a platform that can be used to model and monitor cancer-immune interactions in response to immunotherapy in a high-throughput manner.

A sub-1V, microwatt power-consumption iontronic pressure sensor based on organic electrochemical transistors.

Wearable and implantable pressure sensors are in great demand for personalized health monitoring. Pressure sensors with low operation voltage and low power-consumption are desired for energy-saving devices. Organic iontronic devices, such as organic electrochemical transistors (OECTs), have demonstrated great potential for low power-consumption bioelectronic sensing applications. The ability to conduct both electrons and ions, in addition to their low-operation voltage has enabled the widespread use of OECTs in different biosensing fields. However, despite these merits, OECTs have not been demonstrated for pressure sensing applications. This is because most OECTs are gated with aqueous electrolyte, which fails to respond to external pressure. Here, a low power-consumption iontronic pressure sensor is presented based on an OECT, in which an ionic hydrogel is used as a solid gating medium. The resultant iontronic device operated at voltages less than 1 V, with a power-consumption between ~ 101-103 µW, while maintaining a tunable sensitivity between 1 ~ 10 kPa-1. This work places OECTs on the frontline for developing low power-consumption iontronic pressure sensors and for biosensing applications.

Clinical study on minimally invasive treatment of femoral head necrosis with two different bone graft materials.

PURPOSE: To investigate the clinical efficacy and safety of two different bone graft materials in the minimally invasive treatment of early and middle stage femoral head necrosis. METHODS: A total of 36 patients (39 hips) with avascular necrosis of the femoral head were divided into autologous iliac bone group (ABG) and bioceramics bone group (BBG). Both groups were treated with minimally invasive thick channel decompression to remove dead bone of femoral head. The ABG was treated with autologous iliac bone graft, and BBG was treated with ß-tricalcium phosphate bone graft. The operation time, intra-operative blood loss, haemoglobin, and haematocrit were recorded at three and seven days post-operatively. The clinical efficacy and safety were evaluated by Harris score and imaging examination before, and after treatment and at follow-up stages. RESULTS: The patients were followed up for 24 to 45 (average 29.27 ± 3.56) months. The BBG was significantly better than the ABG in terms of operation time, intra-operative blood loss, haemoglobin, and haematocrit value at three days. Compared with pre-operative, the Harris score of the two groups at 12 months after operation was significantly improved. The Harris score and the imaging evaluation of the last follow-up exhibited significantly better outcome in BBG than those of ABG. CONCLUSION: Bioceramics and autologous iliac bone minimally invasive treatment of early and medium-term femoral head necrosis exhibited satisfactory clinical efficacy in the short and medium-term. The bioceramics graft materials have the advantages of reducing trauma, bleeding, operation time, and quick recovery of post-operative functions.

Gelatin methacryloyl-based tactile sensors for medical wearables.

Gelatin methacryloyl (GelMA) is a widely used hydrogel with skin-derived gelatin acting as the main constituent. However, GelMA has not been used in the development of wearable biosensors, which are emerging devices that enable personalized healthcare monitoring. This work highlights the potential of GelMA for wearable biosensing applications by demonstrating a fully solution-processable and transparent capacitive tactile sensor with microstructured GelMA as the core dielectric layer. A robust chemical bonding and a reliable encapsulation approach are introduced to overcome detachment and water-evaporation issues in hydrogel biosensors. The resultant GelMA tactile sensor shows a high-pressure sensitivity of 0.19 kPa-1 and one order of magnitude lower limit of detection (0.1 Pa) compared to previous hydrogel pressure sensors owing to its excellent mechanical and electrical properties (dielectric constant). Furthermore, it shows durability up to 3000 test cycles because of tough chemical bonding, and long-term stability of 3 days due to the inclusion of an encapsulation layer, which prevents water evaporation (80% water content). Successful monitoring of various human physiological and motion signals demonstrates the potential of these GelMA tactile sensors for wearable biosensing applications.

Flexible patch with printable and antibacterial conductive hydrogel electrodes for accelerated wound healing.

Electrical stimulation can facilitate wound healing with high efficiency and limited side effects. However, current electrical stimulation devices have poor conformability with wounds due to their bulky nature and the rigidity of electrodes utilized. Here, a flexible electrical patch (ePatch) made with conductive hydrogel as electrodes to improve wound management was reported. The conductive hydrogel was synthesized using silver nanowire (AgNW) and methacrylated alginate (MAA), with the former chosen as the electrode material considering its antibacterial properties, and the latter used due to its clinical suitability in wound healing. The composition of the hydrogel was optimized to enable printing on medical-grade patches for personalized wound treatment. The ePatch was shown to promote re-epithelization, enhance angiogenesis, mediate immune response, and prevent infection development in the wound microenvironment. In vitro studies indicated an elevated secretion of growth factors with enhanced cell proliferation and migration ability in response to electrical stimulation. An in vivo study in the Sprague-Dawley rat model revealed a rapid wound closure within 7 days compared to 20 days of usual healing process in rodents.

Light-matter coupling in large-area van der Waals superlattices.

Two-dimensional (2D) crystals have renewed opportunities in design and assembly of artificial lattices without the constraints of epitaxy. However, the lack of thickness control in exfoliated van der Waals (vdW) layers prevents realization of repeat units with high fidelity. Recent availability of uniform, wafer-scale samples permits engineering of both electronic and optical dispersions in stacks of disparate 2D layers with multiple repeating units. Here we present optical dispersion engineering in a superlattice structure comprising alternating layers of 2D excitonic chalcogenides and dielectric insulators. By carefully designing the unit cell parameters, we demonstrate greater than 90% narrow band absorption in less than 4 nm of active layer excitonic absorber medium at room temperature, concurrently with enhanced photoluminescence in square-centimetre samples. These superlattices show evidence of strong light-matter coupling and exciton-polariton formation with geometry-tuneable coupling constants. Our results demonstrate proof of concept structures with engineered optical properties and pave the way for a broad class of scalable, designer optical metamaterials from atomically thin layers.

Treatment of pre-collapse non-traumatic osteonecrosis of the femoral head through Orthopdische Chirurgie München approach combined with autologous bone mixed with ß-tricalcium phosphate porous bioceramic bone graft: a retrospective study of mid-term results.

BACKGROUND: This study aimed to evaluate the clinical efficacy of femoral head and neck fenestration combined with autologous bone mixed with ß-tricalcium phosphate porous bioceramic bone (light bulb procedure) through Orthopdische Chirurgie München approach (OCM approach) for pre-collapse non-traumatic osteonecrosis of the femoral head(ONFH). METHODS: The clinical data of 47 patients (47 hips) with ONFH were retrospectively reviewed. The Harris hip score (HHS) was used to evaluate the clinical outcomes. Imaging was assessed by X-ray. Clinical failure was defined as postoperative total hip arthroplasty (THA) or the HHS was poor (< 70). The Kaplan-Meier survival curve was used to conduct a univariate analysis of risk factors. The analysis factors included gender, age, International Association Research Circulation Osseous (ARCO) stage, etiology, body mass index (BMI), 25-hydroxyvitamin D (25(OH)D), and type I collagen carboxy-terminal peptide (CTX). The COX multivariate risk model was used to analyze the risk factors. RESULTS: All the 47 hips were followed up for 24-58 months, with an average of 45 months. The Harris score (76.29 ± 10.38) at the last follow-up was significantly higher than the preoperative HHS (64.45 ± 2.93) (P < 0.05). The postoperative HHS was excellent with a success rate of 36.17%. Postoperative imaging evaluation showed that 9 hips improved, 28 hips stabilized, and 10 hips progressed. Moreover, 17 out of 47 hips were defined as a postoperative clinical failure and the success rate was 63.83%. 25(OH)D and preoperative ARCO stage were risk factors for postoperative clinical failure (P < 0.05). The COX multivariate risk model analysis showed that IIIA stage was an independent risk factor for postoperative clinical failure (P < 0.05). CONCLUSIONS: The head and neck fenestration and bone grafting via the OCM approach in the treatment of non-traumatic ONFH in the pre-collapse stage can achieve good clinical outcomes. 25(OH)D deficient patients and ARCO IIIA patients had a higher failure rate of bone graft using this approach.

Rhodamine Conjugated Gelatin Methacryloyl Nanoparticles for Stable Cell Imaging.

Fluorescent nanomaterials have been widely used in biological imaging due to their selectivity, sensitivity, and noninvasive nature. These characteristics make the materials suitable for real-time and in situ imaging. However, further development of highly biocompatible nanosystems with long-lasting fluorescent intensity and photostability is needed for advanced bioimaging. We have used electrospraying to generate gelatin methacryloyl (GelMA)-based fluorescent nanoparticles (NPs) with chemically conjugated rhodamine B (RB). The extent of conjugation can be controlled by varying the mass ratio of RB and GelMA precursors to obtain RB-conjugated GelMA (RB-GelMA) NPs with optimal fluorescent properties and particle size. These NPs exhibited superior biocompatibility when compared with pure RB in in vitro cell viability and proliferation assays using multiple cell types. Moreover, RB-GelMA NPs showed enhanced cell internalization and improved brightness compared with unconjugated RB. Our experiments demonstrate that engineered RB-GelMA NPs can be used as a biocompatible fluorescent label for bioimaging.

Room-Temperature-Formed PEDOT:PSS Hydrogels Enable Injectable, Soft, and Healable Organic Bioelectronics.

There is an increasing need to develop conducting hydrogels for bioelectronic applications. In particular, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hydrogels have become a research hotspot due to their excellent biocompatibility and stability. However, injectable PEDOT:PSS hydrogels have been rarely reported. Such syringe-injectable hydrogels are highly desirable for minimally invasive biomedical therapeutics. Here, an approach is demonstrated to develop injectable PEDOT:PSS hydrogels by taking advantage of the room-temperature gelation property of PEDOT:PSS. These PEDOT:PSS hydrogels form spontaneously after syringe injection of the PEDOT:PSS suspension into the desired location, without the need of any additional treatments. A facile strategy is also presented for large-scale production of injectable PEDOT:PSS hydrogel fibers at room temperature. Finally, it is demonstrated that these room-temperature-formed PEDOT:PSS hydrogels (RT-PEDOT:PSS hydrogel) and hydrogel fibers can be used for the development of soft and self-healable hydrogel bioelectronic devices.

Combined Effects of Electric Stimulation and Microgrooves in Cardiac Tissue-on-a-Chip for Drug Screening.

Animal models and traditional cell cultures are essential tools for drug development. However, these platforms can show striking discrepancies in efficacy and side effects when compared to human trials. These differences can lengthen the drug development process and even lead to drug withdrawal from the market. The establishment of preclinical drug screening platforms that have higher relevancy to physiological conditions is desirable to facilitate drug development. Here, a heart-on-a-chip platform, incorporating microgrooves and electrical pulse stimulations to recapitulate the well-aligned structure and synchronous beating of cardiomyocytes (CMs) for drug screening, is reported. Each chip is made with facile lithographic and laser-cutting processes that can be easily scaled up to high-throughput format. The maturation and phenotypic changes of CMs cultured on the heart-on-a-chip is validated and it can be treated with various drugs to evaluate cardiotoxicity and cardioprotective efficacy. The heart-on-a-chip can provide a high-throughput drug screening platform in preclinical drug development.