Combating infections from drug-resistant bacteria: Unleashing synergistic broad-spectrum antibacterial power with high-entropy MXene/CDs.

The growing resistance of bacteria to antibiotics has posed challenges in treating associated bacterial infections, while the development of multi-model antibacterial strategies could efficient sterilization to prevent drug resistance. High-entropy MXene has emerged as a promising candidate for antibacterial synergy with inherent photothermal and photodynamic properties. Herein, a high-entropy nanomaterial of MXene/CDs was synthesized to amplify oxidative stress under near-infrared laser irradiation. Well-exfoliated MXene nanosheets have proven to show an excellent photothermal effect for sterilization. The incorporation of CDs could provide photo-generated electrons for MXene nanosheets to generate ROS, meanwhile reducing the recombination of electron-hole pairs to further accelerate the generation of photo-generated electrons. The MXene/CDs material demonstrates outstanding synergistic photothermal and photodynamic effects, possesses excellent biocompatibility and successfully eliminates drug-resistant bacteria as well as inhibits biofilm formation. While attaining a remarkable killing efficiency of up to 99.99% against drug-resistant Escherichia coli and Staphylococcus aureus, it also demonstrates outstanding antibacterial effects against four additional bacterial strains. This work not only establishes a synthesis precedent for preparing high-entropy MXene materials with CDs but also provides a potential approach for addressing the issue of drug-resistant bacterial infections.

An all-optical multidirectional mechano-sensor inspired by biologically mechano-sensitive hair sensilla.

Mechano-sensitive hair-like sensilla (MSHS) have an ingenious and compact three-dimensional structure and have evolved widely in living organisms to perceive multidirectional mechanical signals. Nearly all MSHS are iontronic or electronic, including their biomimetic counterparts. Here, an all-optical mechano-sensor mimicking MSHS is prototyped and integrated based on a thin-walled glass microbubble as a flexible whispering-gallery-mode resonator. The minimalist integrated device has a good directionality of 32.31 dB in the radial plane of the micro-hair and can detect multidirectional displacements and forces as small as 70 nm and 0.9 µN, respectively. The device can also detect displacements and forces in the axial direction of the micro-hair as small as 2.29 nm and 3.65 µN, respectively, and perceive different vibrations. This mechano-sensor works well as a real-time, directional mechano-sensory whisker in a quadruped cat-type robot, showing its potential for innovative mechano-transduction, artificial perception, and robotics applications.

Engineering a biomimetic system for hepatocyte-specific RNAi treatment of non-alcoholic fatty liver disease.

RNA interference (RNAi) presents great potential against intractable liver diseases. However, the establishment of specific, efficient, and safe delivery systems targeting hepatocytes remains a great challenge. Herein, we described a promising hepatocytes-targeting system through integrating triantennary N-acetylgalactosamine (GalNAc)-engineered cell membrane with biodegradable mesoporous silica nanoparticles, which efficiently and safely delivered siRNA to hepatocytes and silenced the target PCSK9 gene expression for the treatment of non-alcoholic fatty liver disease. Having optimized the GalNAc-engineering strategy, insertion orders, and cell membrane source, we obtained the best-performing GalNAc-formulations allowing strong hepatocyte-specific internalization with reduced Kupffer cell capture, resulting in robust gene silencing and less hepatotoxicity when compared with cationic lipid-based GalNAc-formulations. Consequently, a durable reduction of lipid accumulation and damage was achieved by systemic administering siRNAs targeting PCSK9 in high-fat diet-fed mice, accompanied by displaying desirable safety profiles. Taken together, this GalNAc-engineering biomimetics represented versatile, efficient, and safe carriers for the development of hepatocyte-specific gene therapeutics, and prevention of metabolic diseases. STATEMENT OF SIGNIFICANCE: Compared to MSN@LP-GN3 (MC3-LNP), MSN@CM-GN3 exhibited strong hepatocyte targeting and Kupffer cell escaping, as well as good biocompatibility for safe and efficient siRNA delivery. Furthermore, siPCSK9 delivered by MSN@CM-GN3 reduced both serum and liver LDL-C, TG, TC levels and lipid droplets in HFD-induced mice, resulting in better performance than MSN/siPCSK9@LP-GN3 in terms of lipid-lowering effect and safety profiles. These findings indicated promising advantages of our biomimetic GN3-based systems for hepatocyte-specific gene delivery in chronic liver diseases. Our work addressed the challenges associated with the lower targeting efficiency of cell membrane-mimetic drug delivery systems and the immunogenicity of traditional GalNAc delivery systems. In conclusion, this study provided an effective and versatile approach for efficient and safe gene editing using ligand-integrated biomimetic nanoplatforms.

Analysis of the Chaotic Component of Photoplethysmography and Its Association with Hemodynamic Parameters.

Wearable technologies face challenges due to signal instability, hindering their usage. Thus, it is crucial to comprehend the connection between dynamic patterns in photoplethysmography (PPG) signals and cardiovascular health. In our study, we collected 401 multimodal recordings from two public databases, evaluating hemodynamic conditions like blood pressure (BP), cardiac output (CO), vascular compliance (C), and peripheral resistance (R). Using irregular-resampling auto-spectral analysis (IRASA), we quantified chaotic components in PPG signals and employed different methods to measure the fractal dimension (FD) and entropy. Our findings revealed that in surgery patients, the power of chaotic components increased with vascular stiffness. As the intensity of CO fluctuations increased, there was a notable strengthening in the correlation between most complexity measures of PPG and these parameters. Interestingly, some conventional morphological features displayed a significant decrease in correlation, indicating a shift from a static to dynamic scenario. Healthy subjects exhibited a higher percentage of chaotic components, and the correlation between complexity measures and hemodynamics in this group tended to be more pronounced. Causal analysis showed that hemodynamic fluctuations are main influencers for FD changes, with observed feedback in most cases. In conclusion, understanding chaotic patterns in PPG signals is vital for assessing cardiovascular health, especially in individuals with unstable hemodynamics or during ambulatory testing. These insights can help overcome the challenges faced by wearable technologies and enhance their usage in real-world scenarios.

Fully integrated on-chip FBG interrogator for high-accuracy measurement of wavelengths.

We present the design and fabrication of an on-chip FBG interrogator based on arrayed waveguide grating (AWG) technology. The spectral overlap between adjacent channels in the integrated AWG is significantly enhanced through a combination approach involving the reduction of the output waveguide spacing and an increase in the input waveguide width. As a result of these design choices, our AWG demonstrates excellent spectral consistency, with spectral cross talk exceeding 30 dB. The interrogator seamlessly combining optical and circuitry components achieves full integration and enables a wide range of interrogation wavelengths, including C-band and L-band. With an interrogation range extending up to 80 nm, it theoretically has the capacity to simultaneously interrogate the wavelengths of 20 FBG sensors. Experimental findings demonstrate an absolute interrogation accuracy of less than 2 pm for the fully integrated interrogator. With its compact size, cost-effectiveness, exceptional precision, and ease of integration, the proposed interrogator holds a substantial promise for widespread application in the realm of FBG sensing.

Multi-Parameter Auto-Tuning Algorithm for Mass Spectrometer Based on Improved Particle Swarm Optimization.

Quadrupole mass spectrometers (QMS) are widely used for clinical diagnosis and chemical analysis. To obtain the best experimental results, mass spectrometers must be calibrated to an ideal setting before use. However, tuning the current QMS is challenging. Traditional tuning techniques possess low automation levels and rely primarily on skilled engineers. Therefore, in this study, we propose an innovative auto-tuning algorithm for QMS based on the improved particle swarm optimization (PSO) algorithm to automatically find the optimal solution of QMS parameters and make the QMS reach the optimal state. The improved PSO algorithm is combined with simulated annealing, multiple inertia weights, dynamic boundaries, and other methods to prevent the traditional PSO algorithm from the issue of a local optimal solution and premature convergence. According to the characteristics of the mass spectrum peaks, a termination function is proposed to simplify the termination conditions of the PSO algorithm and further improve the automation level of the mass spectrometer. The results of auto-calibration testing of resolution and mass axis show that both resolution and mass axis calibration could effectively meet the requirements of mass spectrometry experiments. By the experiment of auto-optimization testing of lens and ion source parameters, these parameters were all in the vicinity of the optimal solution, which achieved the expected performance. Through numerous experiments, the reproducibility of the algorithm was established as meeting the auto-tuning function of the QMS. The proposed method can automatically tune the mass spectrometer from its non-optimal condition to the optimal one, which can effectively reduce the tuning difficulty of QMS.

Temporal complexity in photoplethysmography and its influence on blood pressure.

Objective: The temporal complexity of photoplethysmography (PPG) provides valuable information about blood pressure (BP). In this study, we aim to interpret the stochastic PPG patterns with a model-based simulation, which may help optimize the BP estimation algorithms. Methods: The classic four-element Windkessel model is adapted in this study to incorporate BP-dependent compliance profiles. Simulations are performed to generate PPG responses to pulse and continuous stimuli at various timescales, aiming to mimic sudden or gradual hemodynamic changes observed in real-life scenarios. To quantify the temporal complexity of PPG, we utilize the Higuchi fractal dimension (HFD) and autocorrelation function (ACF). These measures provide insights into the intricate temporal patterns exhibited by PPG. To validate the simulation results, continuous recordings of BP, PPG, and stroke volume from 40 healthy subjects were used. Results: Pulse simulations showed that central vascular compliance variation during a cardiac cycle, peripheral resistance, and cardiac output (CO) collectively contributed to the time delay, amplitude overshoot, and phase shift of PPG responses. Continuous simulations showed that the PPG complexity could be generated by random stimuli, which were subsequently influenced by the autocorrelation patterns of the stimuli. Importantly, the relationship between complexity and hemodynamics as predicted by our model aligned well with the experimental analysis. HFD and ACF had significant contributions to BP, displaying stability even in the presence of high CO fluctuations. In contrast, morphological features exhibited reduced contribution in unstable hemodynamic conditions. Conclusion: Temporal complexity patterns are essential to single-site PPG-based BP estimation. Understanding the physiological implications of these patterns can aid in the development of algorithms with clear interpretability and optimal structures.

Bifunctional electrochemical biosensor based on PB-MXene films for the real-time analysis and detection of living cancer cells.

Circulating tumor cells (CTCs) are important prognostic markers for cancer diagnosis and metastasis, and their detection is an important means to detect cancer metastasis. Herein, we construct a novel bifunctional electrochemical biosensor based on the PB-MXene composite films. A simple electrostatic self-assembly approach was employed to prepare a film composed of PB nanocubes on the MXene substrates. Given that the PB is an artificial peroxidase for H2O2 sensing, the PB-MXene films can realize the real-time monitoring of H2O2 secretion from living CTCs. Besides, the anti-CEA attached biosensors can be utilized to quantify the corresponding CTCs. The synergic effects of the MXene with a large specific area and PB with enzyme-free catalysis for H2O2 resulted in PB-MXene films exhibiting high electrocatalytic and low cytotoxicity for both H2O2 sensing and living CTCs capturing. As a result, the biosensor shows a low detection limit of 0.57 µM towards H2O2 with a wide linear range (1 µM to 500 µM), as well as an excellent sensing performance for CTCs (an extremely low detection limit of 9 cells/mL in a wide linear range of 1.3 ×101 to 1.3 ×106 cells/mL). Moreover, the prepared biosensor showed satisfactory stability and anti-interference ability for potential applications in clinical cancer diagnosis and tumor metastasis.

Nitrogen-doped orange emitting carbon dots for ß-carotene detection and lysosomal imaging.

ß-Carotene is a natural antioxidant that has an indispensable effect on the growth and immunity of the human body. For intracellular and in vitro detection of ß-carotene, N-doped carbon quantum dots (O-CDs) were prepared by co-heating carbonization of 1,5-naphthalenediamine and nitric acid in ethanol solvent for 2 h at 200 °C. O-CDs have longer wavelength orange light emission, with an optimal excitation peak of 470 nm and an optimal emission peak of 590 nm. According to the principle of the internal filtering effect on which the detection system is based, O-CDs present a good linear relationship with ß-carotene within a wide range of 0-2000 µM, and the R2 coefficient of the linear regression equation is 0.999. In addition, O-CDs showed targeting of lysosomes in cell imaging and could be used to detect intracellular lysosomal movement. These experiments show that O-CDs can be used for in vivo and in vitro detection of ß-carotene and can serve as a potential substitute to commercial lysosome targeting probes.

Preparation and application of high-brightness red carbon quantum dots for pH and oxidized L-glutathione dual response.

Carbon dots (CDs) with red fluorescence emission are highly desirable for use in bioimaging and trace- substance detection, with potential applications in biotherapy, photothermal therapy, and tumor visualization. Most CDs emit green or blue fluorescence, thus limiting their applicability. We report a novel fluorescent detection platform based on high-brightness red fluorescence emission carbon dots (R-CDs) co-doped with nitrogen and bromine, which exhibit pH and oxidized L-glutathione (GSSG) dual-responsive characteristics. The absolute quantum yield of the R-CDs was as high as 11.93%. We discovered that the R-CDs were able to detect acidic pH in live cells and zebrafish owing to protonation and deprotonation. In addition, GSSG was detected in vitro over a broad linear range (8-200 µM) using the R-CDs with excitation-independent emission. Furthermore, cell imaging and bioimaging experiments demonstrated that the R-CDs were highly cytocompatible and could be used as fluorescent probes to target lysosomes and nucleolus. These studies highlight the promising prospects of R-CDs as biosensing tools for bioimaging and trace-substance detection applications.

Biomimetic Nanovaccines Potentiating Dendritic Cell Internalization via CXCR4-Mediated Macropinocytosis.

Although targeted delivery of nanoparticulate vaccines to dendritic cells (DCs) holds tremendous potential, it still faces insufficient internalization and endosome degradation via the receptor-mediated endocytosis pathway. Inspired by the advantages of CXC-chemokine receptor type 4 (CXCR4)-mediated macropinocytosis in the internalization of DCs, a multifunctional vaccine is constructed based on a reactive oxygen species (ROS)-responsive nanoparticulate core and macropinocytosis-inducing peptide-fused cancer membrane shell, allowing the direct cytosolic delivery of cancer membrane-associated antigen and a stimulator of interferon genes (STING) agonist, cGAMP for highly efficient cancer immunotherapy. The biomimetic nanovaccines show a dramatically enhanced cellular uptake by DCs via CXCR4-mediated macropinocytosis. Such a direct delivery process promotes cytosolic release of cGAMP in response to ROS, and together promoted DC maturation and T cell priming by activating the STING pathway. Consequently, the biomimetic nanovaccines not only result in a great tumor rejection in prophylactic B16-F10 melanoma murine model, but also markedly suppress the growth of established melanoma tumors when combined with anti-PD-1 checkpoint blockade. This study advances the design of biomimetic nanovaccines and provides a promising strategy for macropinocytosis-mediated cancer vaccination.

Highly sensitive detection of low-concentration sodium chloride solutions based on polymeric nanofilms coated long period fiber grating.

Long period fiber gratings (LPFGs) have special advantages in the detection of salt concentrations due to small volume, corrosion resistance and immunity to electromagnetic interference. However, it is very difficult to distinguish low-concentration salt solutions with usual LPFGs owing to the poor sensitivity. In this paper, the detection capability of the LPFG to low-concentration salt solutions was significantly improved by assembling salt-containing poly (diallyldimethylammonium chloride) (PDDA) and salt-containing poly (sodium-p-styrenesulfonate) (PSS). Experimental results showed that, the responsive wavelength range of the LPFG was remarkably broadened in low-concentration salt solutions after assembling nanofilms. The suitable detection range of the PDDA/PSS films coated LPFG for salt concentrations was 0-3%. In such a range, the average refractive index sensitivity and the average salinity sensitivity of the LPFG was as high as 29545.9 nm/RIU and 52.2 nm/% respectively. Compared with the LPFG without nanofilms, the discrimination ability of the PDDA/PSS films coated LPFG to 0-3% salt solutions increased by 568 times. The analysis demonstrated that PDDA and salt in the assembly solutions played a pivotal role in the above effects. The proposed sensor has extensive application prospects in the monitoring of salt concentration in many fields such as seawater, food processing, fermentation process, etc.

A time-resolved fluorescence microsphere-lateral flow immunochromatographic strip for quantitative detection of Pregnanediol-3-glucuronide in urine samples.

Introduction: Pregnanediol-3-glucuronide (PdG), as the main metabolite of progesterone in urine, plays a significant role in the prediction of ovulation, threatened abortion, and menstrual cycle maintenance. Methods: To achieve a rapid and sensitive assay, we have designed a competitive model-based time-resolved fluorescence microsphere-lateral flow immunochromatography (TRFM-LFIA) strip. Results: The optimized TRFM-LFIA strip exhibited a wonderful response to PdG over the range of 30-2,000 ng/mL, the corresponding limit of detection (LOD) was calculated as low as 8.39 ng/mL. More importantly, the TRFM-LFIA strip was innovatively used for the quantitative detection of PdG in urine sample, and excellent recovery results were also obtained, ranging from 97.39% to 112.64%. Discussion: The TRFMLFIA strip possessed robust sensitivity and selectivity in the determination of PdG, indicating the great potential of being powerful tools in the biomedical and diagnosis region.

Nitrogen-doped cyan-emissive carbon quantum dots for fluorescence tetracycline detection and lysosome imaging.

Tetracyclines (TCs) prevent the growth of peptide chains and the synthesis of proteins, and they are widely used to inhibit Gram-positive and -negative bacteria. For the detection of tetracyclines in cell and in vitro, a convenient and simple detection system based on nitrogen-doped cyan carbon quantum dots (C-CQDs) was developed. C-CQDs have excellent excitation-independent properties, the best optimal excitation peak is 360 nm and the best emission peak is 480 nm. Based on the inner filter effect (IFE), the fluorescence intensity of C-CQDs in solution decreases with the increase of tetracyclines. In the range of 0-100 µM, C-CQDs present a good linear relationship with three tetracyclines (CTC, TET, OCT), with R 2 all greater than 0.999. C-CQDs can detect tetracycline in milk samples with recovery in the range of 98.2-103.6%, which demonstrates their potential and broad application in real samples. Furthermore, C-CQDs exhibit excellent lysosomal targeting, as indicated by a Pearson's coefficient of 0.914 and an overlap of 0.985. The internalisation of C-CQDs was mainly affected by lipid raft-mediated endocytosis in endocytic pathway experiments. These experiments indicate that C-CQDs can be effectively used to detect TC content and target lysosomes as an alternative to commercial dyes.

Injectable Carbon Dots-Based Hydrogel for Combined Photothermal Therapy and Photodynamic Therapy of Cancer.

Hydrogel has been widely used in modern biotherapeutics due to its excellent biocompatibility, degradability, and high drug loading capacity. Among them, the construction of a phototherapy system including photosensitizer and hydrogel has aroused great interest in tumor therapy. Unfortunately, complex modifications are necessary to integrate different photosensitizers into the hydrogel. In this work, an injectable hydrogel was proposed by the Schiff base reaction between HA-CHO and carbon dots (CDs), which can realize PTT and PTT simultaneously. Notably, the CDs with rich -NH2 can be used not only as a photosensitizer but also as an efficient cross-linking agent for the Schiff base reaction to form a hydrogel network. The CD@Hydrogel with outstanding biosafety showed a high antitumor effect after 660 nm laser irradiation in in vitro and in vivo experiments. In summary, the CD@Hydrogel can not only realize PTT and PDT synergistic treatment under one light source but also act as a cross-linking agent to react with HA-CHO to form hydrogel, which is simple and efficient, providing a new strategy for cancer phototherapy.

An automated system for nucleic acid extraction from formalin-fixed paraffin-embedded samples using high intensity focused ultrasound technology.

Formalin-fixed paraffin-embedded (FFPE) tissue samples are routinely used in prospective and retrospective studies. It is crucial to obtain high-quality nucleic acid (NA) from FFPE samples for downstream molecular analysis, such as quantitative polymerase chain reaction (PCR), Sanger sequencing, next-generation sequencing, and microarray, in both clinical diagnosis and basic research. The current NA extraction methods from FFPE samples using chemical solvent are tedious, environmentally unfriendly, and unamenable to automation or field deployment. We present a tool for NA extraction from FFPE samples using a high-intensity focused ultrasound (HIFU) technology. A cartridge strip containing reagents for FFPE sample deparaffinization and NA extraction and purification is operated by an automation tool consisting of a HIFU module, a liquid handling robot unit, and accessories including a thermal block and magnets. The HIFU module is a single concaved piezoelectric ceramic plate driven by a current-mode class-D power amplifier. Based on the ultrasonic cavitation effects, the HIFU module provides highly concentrated energy introducing paraffin emulsification and disintegration. The high quantity and quality of NA extracted using the reported system are evaluated by PCR and compared with the quantity and quality of NA extracted using the current standard methods.

Hierarchical Au nanoarrays functionalized 2D Ti2CTx MXene membranes for the detection of exosomes isolated from human lung carcinoma cells.

Exosome is considered an important biomarker of liquid biopsy in early cancer screening, which can reflect the physiological and pathological status of cancer cells. Herein, we construct a novel electrochemical biosensor based on hierarchical Au nanoarray-modified 2D Ti2CTx MXene membranes for sensitive detection of exosomes. Ti2CTx MXene nanosheets were fabricated as the building blocks for preparing 2D membranes as the sensing platform via vacuum filtration. To enhance the conductivity of the MXene membrane, for the first time, hierarchical Au nanoarrays were further deposited in situ on the MXene membrane surface. The combination of MXene membrane with a large specific area and hierarchical Au nanoarrays with excellent conductivity make higher electrocatalytic and more active sites in aptamer immobilization. In this strategy, the composite membrane modified by EpCAM recognized aptamer can specifically capture target exosomes, meanwhile, these target exosomes anchor aptamer for CD63 to further enhance the sensing sensitivity and accuracy of the biosensor. As a result, the biosensor achieved high sensitivity and reliable performance for exosome sensing, with a low detection limit (58 particles/µL) in the linear range of 1 × 102 to 1 × 107 particles/µL. In addition, this biosensor showed satisfactory electrochemical stability and anti-interference ability for the detection of exosomes in real serum samples.

Design, Synthesis, and Application of Carbon Dots With Synergistic Antibacterial Activity.

The diversity of bacteria and their ability to acquire drug resistance lead to many challenges in traditional antibacterial methods. Photothermal therapies that convert light energy into localized physical heat to kill target microorganisms do not induce resistance and provide an alternative for antibacterial treatment. However, many photothermal materials cannot specifically target bacteria, which can lead to thermal damage to normal tissues, thus seriously affecting their biological applications. Here, we designed and synthesized bacteria-affinitive photothermal carbon dots (BAPTCDs) targeting MurD ligase that catalyzes the synthesis of peptidoglycan (PG) in bacteria. BAPTCDs presented specific recognition ability and excellent photothermal properties. BAPTCDs can bind to bacteria very tightly due to their chiral structure and inhibit enzyme activity by competing with D-glutamic acid to bind to MurD ligases, thus inhibiting the synthesis of bacterial walls. It also improves the accuracy of bacteria treatment by laser irradiation. Through the synergy of biochemical and physical effects, the material offers outstanding antibacterial effects and potentially contributes to tackling the spread of antibiotic resistance and facilitation of antibiotic stewardship.

Construction of Multi-color fluorescent carbon dots by Aggregation-Induced emission.

Aggregation-induced emission luminogens (AIEgens) have garnered significant attention because of their outstanding photophysical characteristics. AIEgens are used in fluorescence imaging, sensors, tumor treatment, and other related fields. However, the synthese of these AIEgens are relatively complicated and requires expensive raw materials. These drawbacks limit their applications and development to a certain extent. In this study, using cheap and convenient materials, we developed a new type of carbon dots (O-CDs) using a one-step solvothermal method, which has the potential to become a new AIEgen. O-CDs exhibit different fluorescence colors in different solvents, and they exist as monomers in ethylic acid and, ethanol alcohol, etc., exhibiting blue fluorescence. After adding water, the fluorescence of O-CDs gradually turns orange red, because the internal rotation of the disulfide bond molecules is restricted and the AIE effect occurs. Using the unique AIE performance of O-CDs, we fabricated an anti-counterfeiting luminous ink, that can be used for encryption in the reversible double switch mode.

Ultra-bright carbon quantum dots for rapid cell staining.

Cellular imaging using carbon dots is an important research method in several fields. Herein, green-emissive carbon quantum dots (G-CDs) with a pretty high absolute quantum yield (QY) were fabricated via a one-step solvothermal method by using m-phenylenediamine and concentrated hydrochloric acid. G-CDs displayed strong green fluorescence with excitation/emission peaks at 460/500 nm, and their absolute quantum yield was as high as 58.65%. Further experiments suggested that the G-CDs we prepared have good solubility, excellent biocompatibility, and the capacity of rapidly imaging HeLa and 4T1 cells. Over expectations, the G-CDs could penetrate cells in only 10 s and the confocal images showed that the G-CDs could target the nucleus of cells. Moreover, by using 920 nm as the excitation wavelength, two-photon imaging has been successfully applied to 4T1 cells, overcoming the inherent limitations of single-photon imaging. The extremely high absolute quantum efficiency, ultra-fast imaging speed, and two-photon imaging capability make the G-CDs have good application potential in biomedical analysis and the clinical diagnostic field.