A dual computational and experimental strategy to enhance TSLP antibody affinity for improved asthma treatment.

Thymic stromal lymphopoietin is a key cytokine involved in the pathogenesis of asthma and other allergic diseases. Targeting TSLP and its signaling pathways is increasingly recognized as an effective strategy for asthma treatment. This study focused on enhancing the affinity of the T6 antibody, which specifically targets TSLP, by integrating computational and experimental methods. The initial affinity of the T6 antibody for TSLP was lower than the benchmark antibody AMG157. To improve this, we utilized alanine scanning, molecular docking, and computational tools including mCSM-PPI2 and GEO-PPI to identify critical amino acid residues for site-directed mutagenesis. Subsequent mutations and experimental validations resulted in an antibody with significantly enhanced blocking capacity against TSLP. Our findings demonstrate the potential of computer-assisted techniques in expediting antibody affinity maturation, thereby reducing both the time and cost of experiments. The integration of computational methods with experimental approaches holds great promise for the development of targeted therapeutic antibodies for TSLP-related diseases.

A high-throughput single cell-based antibody discovery approach against the full-length SARS-CoV-2 spike protein suggests a lack of neutralizing antibodies targeting the highly conserved S2 domain.

Coronavirus disease 2019 pandemic continues globally with a growing number of infections, but there are currently no effective antibody drugs against the virus. In addition, 90% amino acid sequence identity between the S2 subunit of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and SARS-CoV S proteins attracts us to examine S2-targeted cross-neutralizing antibodies that are not yet well defined. We therefore immunized RenMab mice with the full-length S protein and constructed a high-throughput antibody discovery method based on single-cell sequencing technology to isolate SARS-CoV-2 S-targeted neutralizing antibodies and cross-neutralizing antibodies against the S2 region of SARS-CoV-2/SARS-CoV S. Diversity of antibody sequences in RenMab mice and consistency in B-cell immune responses between RenMab mice and humans enabled screening of fully human virus-neutralizing antibodies. From all the frequency >1 paired clonotypes obtained from single-cell V(D)J sequencing, 215 antibodies with binding affinities were identified and primarily bound S2. However, only two receptor-binding domain-targeted clonotypes had neutralizing activity against SARS-CoV-2. Moreover, 5' single-cell RNA sequencing indicated that these sorted splenic B cells are mainly plasmablasts, germinal center (GC)-dependent memory B-cells and GC B-cells. Among them, plasmablasts and GC-dependent memory B-cells were considered the most significant possibility of producing virus-specific antibodies. Altogether, using a high-throughput single cell-based antibody discovery approach, our study highlighted the challenges of developing S2-binding neutralizing antibodies against SARS-CoV-2 and provided a novel direction for the enrichment of antigen-specific B-cells.

Novel 15N Metabolic Labeling-Based Large-Scale Absolute Quantitative Proteomics Method for Corynebacterium glutamicum.

With fast growth, synthetic biology powers us with the capability to produce high commercial value products in an efficient resource/energy-consuming manner. Comprehensive knowledge of the protein regulatory network of a bacterial host chassis, e.g., the actual amount of the given proteins, is the key to building cell factories for certain target hyperproduction. Many talent methods have been introduced for absolute quantitative proteomics. However, for most cases, a set of reference peptides with isotopic labeling (e.g., SIL, AQUA, QconCAT) or a set of reference proteins (e.g., commercial UPS2 kit) needs to be prepared. The higher cost hinders these methods for large sample research. In this work, we proposed a novel metabolic labeling-based absolute quantification approach (termed nMAQ). The reference Corynebacterium glutamicum strain is metabolically labeled with 15N, and a set of endogenous anchor proteins of the reference proteome is quantified by chemically synthesized light (14N) peptides. The prequantified reference proteome was then utilized as an internal standard (IS) and spiked into the target (14N) samples. SWATH-MS analysis is performed to obtain the absolute expression levels of the proteins from the target cells. The cost for nMAQ is estimated to be less than 10 dollars per sample. We have benchmarked the quantitative performance of the novel method. We believe this method will help with the deep understanding of the intrinsic regulatory mechanism of C. glutamicum during bioengineering and will promote the process of building cell factories for synthetic biology.

Abnormal Graphitization Behavior in Near-Surface/Interface Region of Polymer-Derived Ceramics.

The in situ free carbon generated in polymer-derived ceramics (PDCs) plays a crucial role in their unique microstructure and resultant properties. This study advances a new phenomenon of graphitization of PDCs. Specifically, whether in micro-/nanoscale films or millimeter-scale bulks, the surface/interface radically changes the fate of carbon and the evolution of PDC nanodomains, promotes the graphitization of carbon, and evolves a free carbon enriched layer in the near-surface/interface region. Affected by the enrichment behavior of free carbon in the near-surface/interface region, PDCs exhibit highly abnormal properties such as the skin behavior and edge effect of the current. The current intensity in the near-surface/interface region of PDCs is orders of magnitude higher than that in its interior. Ultrahigh conductivity of up to 14.47 S cm-1 is obtained under the action of the interface and surface, which is 5-8 orders of magnitude higher than that of the bulk prepared under the same conditions. Such surface/interface interactions are of interest for the regulation of free carbon and its resultant properties, which are the core of PDC applications. Finally, the first PDC thin-film strain gauge that can survive a butane flame with a high temperature of up to ≈1300 °C is fabricated.

Storage Stability of Blood Samples for miRNAs in Glycosylated Extracellular Vesicles.

Extracellular vesicle (EV) miRNAs are promising biomarkers for clinical diagnosis. However, their stability is a crucial concern affecting reliability and accuracy. Factors such as sample collection, processing, storage conditions, and experimental procedures impact EV miRNA stability. Studying EV miRNA stability aims to find optimal handling and storage methods, ensuring integrity and functionality throughout research. In this study, we used RT-qPCR and GlyExo-Capture technology, which can specifically capture glycosylated EVs by lectin, to assess the stability of glycosylated EV miRNAs. We found that slow acceleration centrifugation and two-step centrifugation methods were suitable for subsequent experiments. To ensure uniformity, we recommend using the two-step centrifugation method. We also studied blood storage before serum separation and recommend separation within 2 h at 4 °C or 25 °C. For separated serum samples, higher temperatures accelerated miRNA degradation, and the storage duration should be adjusted based on laboratory conditions. Short-term storage at -20 °C is acceptable for up to 3 months while avoiding repeated freeze-thaw cycles. We developed protective agents to extend the storage time at 25 °C, meeting clinical requirements. Additionally, Lakebio's cfRNA storage tubes effectively preserved the stability of miRNAs in plasma glycosylated EVs. Understanding EV miRNA stability provides insights into optimizing sample handling, storage strategies, and enhancing reliability in clinical applications.

Molecular mechanism for bidirectional regulation of CD44 for lipid raft affiliation by palmitoylations and PIP2.

The co-localization of Cluster-of-Differentiation-44 protein (CD44) and cytoplasmic adaptors in specific membrane environments is crucial for cell adhesion and migration. The process is controlled by two different pathways: On the one hand palmitoylation keeps CD44 in lipid raft domains and disables the linking to the cytoplasmic adaptor, whereas on the other hand, the presence of phosphatidylinositol-4,5-biphosphate (PIP2) lipids accelerates the formation of the CD44-adaptor complex. The molecular mechanism explaining how CD44 is migrating into and out of the lipid raft domains and its dependence on both palmitoylations and the presence of PIP2 remains, however, elusive. In this study, we performed extensive molecular dynamics simulations to study the raft affinity and translocation of CD44 in phase separated model membranes as well as more realistic plasma membrane environments. We observe a delicate balance between the influence of the palmitoylations and the presence of PIP2 lipids: whereas the palmitoylations of CD44 increases the affinity for raft domains, PIP2 lipids have the opposite effect. Additionally, we studied the association between CD44 and the membrane adaptor FERM in dependence of these factors. We find that the presence of PIP2 lipids allows CD44 and FERM to associate in an experimentally observed binding mode whereas the highly palmitoylated species shows no binding affinity. Together, our results shed light on the sophisticated mechanism on how membrane translocation and peripheral protein association can be controlled by both protein modifications and membrane composition.

Exploiting tandem repetitive promoters for high-level production of 3-hydroxypropionic acid.

High-level biosynthesis of desired metabolites is challenging due to complexity of metabolic networks. Here, we report that platform chemical 3-hydroxypropionic acid (3-HP) can be overproduced through promoter engineering and growth-sustaining cultivation, two parallel strategies relying on RNA polymerases (RNAPs). First, we screened a promoter library and revealed that IPTG-inducible tac promoter was most effective for overexpression of PuuC, an endogenous aldehyde dehydrogenase catalyzing 3-HP biosynthesis in Klebsiella pneumoniae. Next, tandem repetitive tac promoters were harnessed to accommodate adequate RNAPs. When three tandem repetitive tac promoters were recruited to overexpress PuuC, up to 102.61 g/L 3-HP was produced. This is the highest 3-HP titer reported so far. In addition, lactic acid completely vanished during the late stage of fermentation. The backflow of lactic acid to pyruvic acid saves the trouble of downstream separation of lactic acid from 3-HP, which has long been a mission impossible because they are small-molecule isomers. Furthermore, timely removal of acid stress and replenishment of nitrogen source are crucial for 3-HP biosynthesis. A mathematical model shows that RNAPs modulate the tradeoff between bacterial growth and 3-HP formation. Overall, promoter engineering and growth-promoting cultivation jointly leverage RNAPs to maximize 3-HP. This study provides a paradigm for maximizing growth-coupled metabolites.

Molecular Dynamics of the Association of L-Selectin and FERM Regulated by PIP2.

Phosphatidylinositol 4,5-bisphosphate (PIP2) acts as a signaling lipid, mediating membrane trafficking and recruitment of proteins to membranes. A key example is the PIP2-dependent regulation of the adhesion of L-selectin to the cytoskeleton adaptors of the N-terminal subdomain of ezrin-radixin-moesin (FERM). The molecular details of the mediating behavior of multivalent anionic PIP2 lipids in this process, however, remain unclear. Here, we use coarse-grained molecular dynamics simulation to explore the mechanistic details of PIP2 in the transformation, translocation, and association of the FERM/L-selectin complex. We compare membranes of different compositions and find that anionic phospholipids are necessary for both FERM and the cytoplasmic domain of L-selectin to absorb on the membrane surface. The subsequent formation of the FERM/L-selectin complex is strongly favored by the presence of PIP2, which clusters around both proteins and triggers a conformational transition in the cytoplasmic domain of L-selectin. We are able to quantify the effect of PIP2 on the association free energy of the complex by means of a potential of mean force. We conclude that PIP2 behaves as an adhesive agent to enhance the stability of the FERM/L-selectin complex and identify key residues involved. The molecular information revealed in this study highlights the specific role of membrane lipids such as PIP2 in protein translocation and potential signaling.

Critical residues and motifs for homodimerization of the first transmembrane domain of the plasma membrane glycoprotein CD36.

The plasma transmembrane (TM) glycoprotein CD36 is critically involved in many essential signaling processes, especially the binding/uptake of long-chain fatty acids and oxidized low-density lipoproteins. The association of CD36 potentially activates cytosolic protein tyrosine kinases that are thought to associate with the C-terminal cytoplasmic tail of CD36. To understand the mechanisms by which CD36 mediates ligand binding and signal transduction, we have characterized the homo-oligomeric interaction of CD36 TM domains in membrane environments and with molecular dynamics (MD) simulations. Analysis of pyrene- and coumarin-labeled TM1 peptides in SDS by FRET confirmed the homodimerization of the CD36 TM1 peptide. Homodimerization assays of CD36 TM domains with the TOXCAT technique showed that its first TM (TM1) domain, but not the second TM (TM2) domain, could homodimerize in a cell membrane. Small-residue, site-specific mutation scanning revealed that the CD36 TM1 dimerization is mediated by the conserved small residues Gly12, Gly16, Ala20, and Gly23 Furthermore, molecular dynamics (MD) simulation studies demonstrated that CD36 TM1 exhibited a switching dimerization with two right-handed packing modes driven by the 12GXXXGXXXA20 and 20AXXG23 motifs, and the mutational effect of G16I and G23I revealed these representative conformations of CD36 TM1. This packing switch pattern of CD36 TM1 homodimer was further examined and confirmed by FRET analysis of monobromobimane (mBBr)-labeled CD36 TM1 peptides. Overall, this work provides a structural basis for understanding the role of TM association in regulating signal transduction via CD36.

The dimerization of PSGL-1 is driven by the transmembrane domain via a leucine zipper motif.

P-selectin glycoprotein ligand-1 (PSGL-1) is a homodimeric mucin ligand that is important to mediate the earliest adhesive event during an inflammatory response by rapidly forming and dissociating the selectin-ligand adhesive bonds. Recent research indicates that the noncovalent associations between the PSGL-1 transmembrane domains (TMDs) can substitute for the C320-dependent covalent bond to mediate the dimerization of PSGL-1. In this article, we combined TOXCAT assays and molecular dynamics (MD) simulations to probe the mechanism of PSGL-1 dimerization. The results of TOXCAT assays and Martini coarse-grained molecular dynamics (CG MD) simulations demonstrated that PSGL-1 TMDs strongly dimerized in a natural membrane and a leucine zipper motif was responsible for the noncovalent dimerization of PSGL-1 TMD since mutations of the residues that occupied a or d positions in an (abcdefg)n leucine heptad repeat motif significantly reduced the dimer activity. Furthermore, we studied the effects of the disulfide bond on the PSGL-1 dimer using MD simulations. The disulfide bond was critical to form the leucine zipper structure, by which the disulfide bond further improved the stability of the PSGL-1 dimer. These findings provide insights to understand the transmembrane association of PSGL-1 that is an important structural basis for PSGL-1 preferentially binding to P-selectin to achieve its biochemical and biophysical functions.

Digestion of Dynamic Substrate by Exonuclease Reveals High Single-Mismatch Selectivity.

The distinctive nuclease activity toward nucleic acid substrates enables various applications in analytical chemistry and dynamic DNA nanotechnology. λ Exonuclease is a widely used tool for the processing of PCR products, and DNA sequencing. This enzyme also shows promise for reducing the leakage (i.e., activation in absence of a correct input) in DNA-based analytical methods and nanotechnology due to its sensitivity to mismatches. However, the selectivity of λ exonuclease for single-mismatch in most applications is not high. Inspired by the increased specificity of dynamic probes in DNA nanotechnology, we enhanced the single-mismatch selectivity of λ exonuclease by using very short double-stranded DNA (dsDNA) as the substrate. From the bulk fluorescence measurements, short perfectly matched (PM) substrate which is as a correct input can be effectively digested, but the existence of single-mismatch drastically reduces the digestion rate. Real-time single-molecule kinetics analysis reveals that PM substrate can be selectively stabilized by the binding of λ exonuclease, which combines with the differential stability of transient hybridization of short substrates to yield high single-mismatch selectivity. An excellent selective assay for a single-nucleotide mutation in KRAS was demonstrated, which permits detecting this mutation from cell line at as low as 0.02%, holding potential for detecting rare mutations in circulating tumor DNA of early stage cancers.

Engineering CRISPR interference system in Klebsiella pneumoniae for attenuating lactic acid synthesis.

BACKGROUND: Klebsiella pneumoniae is a promising industrial species for bioproduction of bulk chemicals such as 1,3-propanediol, 2,3-butanediol and 3-hydroxypropionic acid (3-HP). However, lactic acid is a troublesome by-product when optimizing for 3-HP production. Therefore, it is highly desirable to minimize lactic acid. RESULTS: Here, we show that lactic acid synthesis can be largely blocked by an engineered CRISPR interference (CRISPRi) system in K. pneumoniae. EGFP was recruited as a reporter of this CRISPRi system. Fluorescence assay of this CRISPRi system showed that enhanced green fluorescent protein (EGFP) expression level was repressed by 85-90%. To further test this CRISPRi system, guide RNAs were designed to individually or simultaneously target four lactate-producing enzyme genes. Results showed that all lactate-producing enzyme genes were significantly repressed. Notably, D-lactate dehydrogenase (ldhA) was shown to be the most influential enzyme for lactic acid formation in micro-aerobic conditions, as inhibiting ldhA alone led to lactic acid level similar to simultaneously repressing four genes. In shake flask cultivation, the strain coexpressing puuC (an aldehyde dehydrogenase catalyzing 3-hydroxypropionaldehyde to 3-HP) and dCas9-sgRNA inhibiting ldhA produced 1.37-fold 3-HP relative to the reference strain. Furthermore, in bioreactor cultivation, this CRISPRi strain inhibiting ldhA produced 36.7 g/L 3-HP, but only generated 1 g/L lactic acid. Clearly, this engineered CRISPRi system largely simplified downstream separation of 3-HP from its isomer lactic acid, an extreme challenge for 3-HP bioprocess. CONCLUSIONS: This study offers a deep understanding of lactic acid metabolism in diverse species, and we believe that this CRISPRi system will facilitate biomanufacturing and functional genome studies of K. pneumoniae or beyond.

Scaling tunable network model to reproduce the density-driven superlinear relation.

Previous works have shown the universality of allometric scaling under total and density values at the city level, but our understanding of the size effects of regions on the universality of allometric scaling remains inadequate. Here, we revisit the scaling relations between the gross domestic production (GDP) and the population based on the total and density values and first reveal that the allometric scaling under density values for different regions is universal. The scaling exponent ß under the density value is in the range of (1.0, 2.0], which unexpectedly exceeds the range observed by Pan et al. [Nat. Commun. 4, 1961 (2013)]. For the wider range, we propose a network model based on a 2D lattice space with the spatial correlation factor α as a parameter. Numerical experiments prove that the generated scaling exponent ß in our model is fully tunable by the spatial correlation factor α. Our model will furnish a general platform for extensive urban and regional studies.

Insights into the transmembrane helix associations of kit ligand by molecular dynamics simulation and TOXCAT.

Kit ligand (KITL) plays important roles in cell proliferation, differentiation, and survival via interaction with its receptor Kit. The previous studies demonstrated that KITL formed a noncovalent homodimer through transmembrane (TM) domain; however, the undergoing mechanism of transmembrane association that determines KITL TM dimerization is still not clear. Herein, molecular dynamics (MD) simulation strategy and TOXCAT assay were combined to characterize the dimerization interface and structure of KITL TM in details. KITL TM formed a more energetically favorable noncovalent dimer through a conserved SxxxGxxxG motif in the MD simulation. Furthermore, the TOXCAT results demonstrated that KITL TM self-associated strongly in the bilayer membrane environment. Mutating any one of the small residues Ser11, Gly15 or Gly19 to Ile disrupted KITL TM dimerization dramatically, which further validated our MD simulation results. In addition, our results showed that Tyr22 could help to stabilize the TM interactions via interacting with the phosphoric group in the bilayer membrane. Pro7 did not induce helix kinks or swivel angles in KITL TM, but it was related with the pitch of the turn around this residue so as to affect the dimer formation. Combining the results of computer modeling and experimental mutagenesis studies on the KITL TM provide new insights for the transmembrane helix association of KITL dimerization. Proteins 2017; 85:1362-1370. © 2017 Wiley Periodicals, Inc.

Dimerization and Structural Stability of Amyloid Precursor Proteins Affected by the Membrane Microenvironments.

The lipid raft microenvironment is implicated in the generation of the pathological amyloid-ß (Aß) species in amyloid precursor protein (APP) that is associated with neurodegenerative diseases. Evidence shows that APP forms a transmembrane homodimer with changeable structures as a function of the membrane compositions. However, the molecular responsibility of the dimerization and structural alteration for the amyloidogenic process in segregated membranes remains largely unclear. Here, we performed multiple coarse grained (CG) simulations to explore the behavioral preference of the transmembrane domain of APP (called C99) that is affected by the lipid raft microenvironment. The results showed that C99 was anchored at the boundary of the lipid raft relying on the conserved hydrophobic motif of V710xxA713xxxV717xxxV721. Moreover, the dimerization of C99 was greatly destabilized by the lipid raft, which led to a susceptible switching packing conformation. The molecular driving forces were derived from the combined regulation of the saturated lipids and cholesterols rather than from the simple binding competition of cholesterol in the C99 dimerization. The molecular details of the differential dimerization in the raft-forming and bulk fluid bilayer environments were compared, and the structural information was helpful for further understanding the enzymolysis responsiveness of APP.

The impact of antibiotic exposure on antibiotic resistance gene dynamics in the gut microbiota of inflammatory bowel disease patients.

Background: While antibiotics are commonly used to treat inflammatory bowel disease (IBD), their widespread application can disturb the gut microbiota and foster the emergence and spread of antibiotic resistance. However, the dynamic changes to the human gut microbiota and direction of resistance gene transmission under antibiotic effects have not been clearly elucidated. Methods: Based on the Human Microbiome Project, a total of 90 fecal samples were collected from 30 IBD patients before, during and after antibiotic treatment. Through the analysis workflow of metagenomics, we described the dynamic process of changes in bacterial communities and resistance genes pre-treatment, during and post-treatment. We explored potential consistent relationships between gut microbiota and resistance genes, and established gene transmission networks among species before and after antibiotic use. Results: Exposure to antibiotics can induce alterations in the composition of the gut microbiota in IBD patients, particularly a reduction in probiotics, which gradually recovers to a new steady state after cessation of antibiotics. Network analyses revealed intra-phylum transfers of resistance genes, predominantly between taxonomically close organisms. Specific resistance genes showed increased prevalence and inter-species mobility after antibiotic cessation. Conclusion: This study demonstrates that antibiotics shape the gut resistome through selective enrichment and promotion of horizontal gene transfer. The findings provide insights into ecological processes governing resistance gene dynamics and dissemination upon antibiotic perturbation of the microbiota. Optimizing antibiotic usage may help limit unintended consequences like increased resistance in gut bacteria during IBD management.

In search of the ratio of miRNA expression as robust biomarkers for constructing stable diagnostic models among multi-center data.

MicroRNAs (miRNAs) are promising biomarkers for the early detection of disease, and many miRNA-based diagnostic models have been constructed to distinguish patients and healthy individuals. To thoroughly utilize the miRNA-profiling data across different sequencing platforms or multiple centers, the models accounting the batch effects were demanded for the generalization of medical application. We conducted transcription factor (TF)-mediated miRNA-miRNA interaction network analysis and adopted the within-sample expression ratios of miRNA pairs as predictive markers. The ratio of the expression values between each miRNA pair turned out to be stable across multiple data sources. A genetic algorithm-based classifier was constructed to quantify risk scores of the probability of disease and discriminate disease states from normal states in discovery, with a validation dataset for COVID-19, renal cell carcinoma, and lung adenocarcinoma. The predictive models based on the expression ratio of interacting miRNA pairs demonstrated good performances in the discovery and validation datasets, and the classifier may be used accurately for the early detection of disease.

Conformal Fabrication of Thick Film Platinum Strain Gauge Via Error Regulation Strategies for In Situ High-Temperature Strain Detection.

Monitoring high-temperature strain on curved components in harsh environments is a challenge for a wide range of applications, including in aircraft engines, gas turbines, and hypersonic vehicles. Although there are significant improvements in the preparation of high-temperature piezoresistive film on planar surfaces using 3D printing methods, there are still difficulties with poor surface compatibility and high-temperature strain testing on curved surfaces. Herein, a conformal direct ink writing (CDIW) system coupled with an error feedback regulation strategy was used to fabricate high-precision, thick films on curved surfaces. This strategy enabled the maximum amount of error in the distance between the needle and the substrate on a curved surface to be regulated from 155 to 4 µm. A conformal Pt thick-film strain gauge (CPTFSG) with a room-temperature strain coefficient of 1.7 was created on a curved metallic substrate for the first time. The resistance drift rate at 800 °C for 1 h was 1.1%, which demonstrated the excellent stability and oxidation resistance of the CPTFSG. High-temperature dynamic strain tests up to 769 °C revealed that the sensor had excellent high-temperature strain test performance. Furthermore, the CPTFSG was conformally deposited on an aero-engine turbine blade to perform in situ tensile and compressive strain testing at room temperature. High-temperature strain tests were conducted at 100 and 200 °C for 600 and 580 µÎµ, respectively, demonstrating a high steady-state response consistent with the commercial high-temperature strain transducer. In addition, steady-state strain tests at high temperatures up to 496 °C were tested. The CDIW error modulation strategy provides a highly promising approach for the high-precision fabrication of Pt thick films on complex surfaces and driving in situ sensing of high-temperature parameters on curved components toward practical applications.

Observation of topological frequency combs.

On-chip generation of optical frequency combs using nonlinear ring resonators has enabled numerous applications of combs that were otherwise limited to mode-locked lasers. Nevertheless, on-chip frequency combs have relied predominantly on single-ring resonators. In this study, we experimentally demonstrate the generation of a novel class of frequency combs, the topological frequency combs, in a two-dimensional lattice of hundreds of ring resonators that hosts fabrication-robust topological edge states with linear dispersion. By pumping these edge states, we demonstrate the generation of a nested frequency comb that shows oscillation of multiple edge state resonances across ≈40 longitudinal modes and is spatially confined at the lattice edge. Our results provide an opportunity to explore the interplay between topological physics and nonlinear frequency comb generation in a commercially available nanophotonic platform.

Rapid laser fabrication of indium tin oxide and polymer-derived ceramic composite thin films for high-temperature sensors.

Thin-film sensors are essential for real-time monitoring of components in high-temperature environments. Traditional fabrication methods often involve complicated fabrication steps or require prolonged high-temperature annealing, limiting their practical applicability. Here, we present an approach using direct ink writing and laser scanning (DIW-LS) to fabricate high-temperature functional thin films. An indium tin oxide (ITO)/preceramic polymer (PP) ink suitable for DIW was developed. Under LS, the ITO/PP thin film shrank in volume. Meanwhile, the rapid pyrolysis of PP into amorphous precursor-derived ceramic (PDC) facilitated the faster sintering of ITO nanoparticles and improved the densification of the thin film. This process realized the formation of a conductive network of interconnected ITO nanoparticles. The results show that the ITO/PDC thin film exhibits excellent stability, with a drift rate of 4.7 % at 1000 °C for 25 h, and withstands temperatures up to 1250 °C in the ambient atmosphere. It is also sensitive to strain, with a maximum gauge factor of -6.0. As a proof of concept, we have used DIW-LS technology to fabricate a thin-film heat flux sensor on the surface of the turbine blade, capable of measuring heat flux densities over 1 MW/m2. This DIW-LS process provides a viable approach for the integrated, rapid, and flexible fabrication of thin film sensors for harsh environments.