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.

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.

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.

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.

Silver Mesoporous Silica Nanoparticles: Fabrication to Combination Therapies for Cancer and Infection.

The integration of silver nanoparticles (Ag NPs) with mesoporous silica nanoparticles (MSNs) protects the former from aggregation and promotes the controlled release of silver ions, resulting in therapeutic significance on cancer and infection. The unique size, shape, pore structure and silver distribution of silver mesoporous silica nanoparticles (Ag-MSNs) embellish them with the potential to perform combined imaging and therapeutic actions via modulating optical and drug release properties. Here, we comprehensively review the recent progress in the fabrication and application of Ag-MSNs for combination therapies for cancer and infection. We first elaborate on the fabrication of star-shaped structure, core-shell structure, and Janus structure Ag-MSNs. We then highlight Ag-MSNs as a multifunctional nanoplatform to surface-enhanced Raman scattering-based detection, non-photo-based cancer theranostics and photo-based cancer theranostics. In addition, we detail Ag-MSNs for combined antibacterial therapy via drug delivery and phototherapy. Overall, we summarize the challenges and future perspectives of Ag-MSNs that make them promising for diagnosis and therapy of cancer and infection.

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.

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.

Light-triggered multifunctional nanoplatform for efficient cancer photo-immunotherapy.

Cancer immunotherapy is limited by the immune escape of tumor cells and adverse effects. Photo-immunotherapy, the combination of immunotherapy and phototherapy (such as photodynamic therapy (PDT) and photothermal therapy (PTT)), can improve the effectiveness of immunotherapy in cancer treatment. Here, we first explored mesoporous hexagonal core-shell zinc porphyrin-silica nanoparticles (MPSNs), which are composed of a zinc porphyrin core and a mesoporous silica shell, and exhibit high laser-triggered photodynamic and photothermal activity, as well as outstanding drug loading capacity. In other words, MPSNs can be used not only as excellent photosensitizers for photo-immunotherapy, but also as an ideal drug carrier to achieve more efficient synergy. After loading with R837 (imiquimod, a toll-like receptor-7 agonist), MPSNs@R837 will elicit high-efficiency immunogenic cell death via PDT and PTT, and promote dendritic cell maturation after the PH-responsive release of R837, thereby, inducing tumor-specific immune responses. When combined with a programmed death ligand-1 checkpoint blockade, the photo-immunotherapy system markedly restrains primary tumors and metastatic tumors with negligible systemic toxicity. Therefore, the therapeutic strategy of integrating PTT, PDT and checkpoint blockade, shows great potential for suppressing cancer metastasis.

Coordination and Redox Dual-Responsive Mesoporous Organosilica Nanoparticles Amplify Immunogenic Cell Death for Cancer Chemoimmunotherapy.

Amplifying the chemotherapy-driven immunogenic cell death (ICD) for efficient and safe cancer chemoimmunotherapy remains a challenge. Here, a potential ICD nanoamplifier containing diselenide-bridged mesoporous organosilica nanoparticles (MONs) and chemotherapeutic ruthenium compound (KP1339) to achieve cancer chemoimmunotherapy is tailored. KP1339-loaded MONs show controlled drug release profiles via glutathione (GSH)-responsive competitive coordination and matrix degradation. High concentration of MONs selectively evoked reactive oxygen species production, GSH depletion, and endoplasmic reticulum stress in cancer cells, thus amplifying the ICD of KP1339 and boosting robust antitumor immunological responses. After the combination of PD-L1 checkpoint blockade, cancer cell membrane-cloaked KP1339-loaded MONs not only regress primary tumor growth with low systemic toxicity, but also inhibit distant tumor growth and pulmonary metastasis of breast cancer. The results have shown the potential of coordination and redox dual-responsive MONs boosting amplified ICD for cancer chemoimmunotherapy.

Extremely sensitive multi-order mode refractive index sensor using TiO2 nanograss film and weakly bounded waveguide modes.

An extremely sensitive multi-order mode refractive index (RI) sensor was fabricated by coupling titanium dioxide nanograss film coated FTO conductive glass with Kretschmann prism. Both calculation and experimental studies were carried out. Theoretical analysis by employing resonant waveguide modes indicated that the maximum sensitivity could be achieved when the mode worked at the weakly-bounded condition. The experimental results showed that for p-polarized and s-polarized light, the sensor exhibited a maximum RI sensitivity of 2938.21 nm/RI unit (RIU) and 1484.39 nm/RIU in the 1st order mode, respectively. Its maximum figure of merit was as high as 77.77. The proposed sensor is promising to be applied in environmental monitoring, immune analysis, nucleic acid test, etc.

Iron and nitrogen-co-doped carbon quantum dots for the sensitive and selective detection of hematin and ferric ions and cell imaging.

Iron, nitrogen-co-doped carbon quantum dots (Fe,N-CDs) were prepared via a simple one-step hydrothermal method. The quantum yield of fluorescence reached about 27.6% and the blue-emissive Fe,N-CDs had a mean size of 3.76 nm. The as-prepared carbon quantum dots showed good solubility, a high quantum yield, good biocompatibility, low cytotoxicity, and high photostability. Interestingly, the as-prepared Fe,N-CDs exhibited good selectivity and sensitivity toward both hematin and ferric ions, and the limit of detection for hematin and ferric ions was calculated to be about 0.024 µM and 0.64 µM, respectively. At the same time, Fe,N-CDs were used for imaging HeLa cells and showed that most Fe,N-CDs were detained in the lysosome. Thus, this fluorescent probe has potential application in the quantitative detection of hematin or Fe3+ in a complex environment and for determining Fe3+ at the cellular level.

Superior reducing carbon dots from proanthocyanidin for free-radical scavenging and for cell imaging.

The presence of excessive ROS can cause much harm to the human body and can even cause diseases. Therefore, it is important to detect and remove ROS, but there is no ideal method available for this at present. In this research, using procyanidins, a type of plant extract with strong reducibility, as raw materials, fluorescent carbon dots (CDs) were prepared by a hydrothermal method. The proanthocyanidin-based carbon dots (PCDs) emit a light-green colored light under UV irradiation. The PCDs retain the strong reducibility of procyanidins and are highly water-soluble compared with procyanidins. The PCDs, in addition to having good biocompatibility, also have the superior properties of radical scavenging activity and cell imaging. In in vitro experiments, 1,1-diphenyl-2-picrylhydrazyl (DPPH; 100 µM) was reduced by 30% when PCDs were added up to a concentration of 87.5 µg mL-1. At the same time, the fluorescence quenching correlates with the concentration of hypochlorite and hydrogen peroxide and has a good linearity in the range of 250-2250 nM and 60-180 µM with a detection limit of 3.676 nM and 0.602 µM, respectively. Based on the previously described advantages, PCDs have potential as a biomedicine.

Yttrium-mediated red fluorescent carbon dots for sensitive and selective detection of calcium ions.

As the second messenger in cells, calcium ions are indispensable in various physiological activities of the body. In this work, a special red fluorescent carbon dot was designed and synthesized using the secondary hydrothermal method with yttrium, p-phenylenediamine, and ethylene glycol tetraacetic acid as precursors for the detection of calcium ions. The designed carbon dot exhibited bright red fluorescence, and the fluorescence emission wavelength showed good photostability. When the calcium ion concentration was controlled from 0 to 400 µM, the carbon dot tended to respond to fluorescence quenching. At the same time, a test paper experiment was carried out, which proved the potential application of the nano-sensor in detecting calcium ions.

Simultaneous Recognition of Dopamine and Uric Acid in the Presence of Ascorbic Acid via an Intercalated MXene/PPy Nanocomposite.

Two-dimensional (2D) MXenes have shown a great potential for chemical sensing due to their electric properties. In this work, a Ti3C2Tx/polypyrrole (MXene/PPy) nanocomposite has been synthesized and immobilized into a glassy carbon electrode to enable the simultaneous recognition of dopamine (DA) and uric acid (UA) under the interference of ascorbic acid (AA). The multilayer Ti3C2Tx MXene was prepared via the aqueous acid etching method and delaminated to a single layer nanosheet, benefiting the in-situ growth of PPy nanowires. The controllable preparation strategy and the compounding of PPy material remain great challenges for further practical application. A facile chemical oxidation method was proposed to regulate magnitude and density during the forming process of PPy nanowire, which promotes the conductivity and the electrochemical active site of this as-prepared nanomaterial. The MXene/PPy nanocomposite-modified electrode exhibited the selective determination of DA and UA in the presence of a high concentration of AA, as well as a wide linear range (DA: 12.5-125 µM, UA: 50-500 µM) and a low detection limit (DA: 0.37 µM, UA: 0.15 µM). More importantly, the simultaneous sensing for the co-existence of DA and UA was successfully achieved via the as-prepared sensor.

Theoretical Study on the Photoinduced Electron Transfer Mechanisms of Different Peroxynitrite Probes.

The development of probes for rapid and selective detection of peroxynitrite in vivo is of great importance in biological science. We investigate different photoinduced electron transfer (PIET) processes of two generations of peroxynitrite probes. Each has fluorescein and phenol moieties; one is conjugated by an ether linkage while the other is conjugated via an amine linkage. Using theoretical calculations, we demonstrated that the PIET in the probe with an ether linkage occurs from the benzoic acid to the xanthene moiety. In contrast, the PIET in the probe with an amine linkage occurs from the phenol moiety to the fluorescein. This suggests that better sensitivity can be accomplished in probes with an amine linkage than with an ether linkage. Following this model, we designed two novel peroxynitrite probes and simulated their detection capabilities in the near-infrared region.

The influence of polyanion molecular weight on polyelectrolyte multilayers at surfaces: elasticity and susceptibility to saloplasticity of strongly dissociated synthetic polymers at fluid-fluid interfaces.

We studied the interfacial mechanical properties of polyelectrolyte multilayer assemblies of poly(diallylamine hydrochloride) (PAH) and poly(4-styrenesulfonate)sodium salt (PSS) at the air-water interface using axisymmetric drop shape analysis (ADSA) during hydrostatic inflation as a function of aqueous salt concentration and two different polyanion molecular weights (Mw ∼ 13 and 70 kDa). Surface elastic moduli (Gs) ranged from 50 to 300 mN m-1. Using the measured film thickness, the bulk moduli (G) ranged from 10 to 90 MPa consistent with elastomeric solids. This solid-like interface was evidenced by a systematic departure of the inflated shape from the Young-Laplace equation, which assumes a liquid-like interface. Surface elastic moduli increased and bulk elastic moduli decreased with increasing nanomembrane transverse dimension, and multilayers with the lower molecular weight anion were more transversely compact than those of higher molecular weight and displayed a larger elastic modulus. The bulk moduli of both types of multilayer assemblies asymptotically approach a constant value for films with more than two bilayers of polyelectrolyte, consistent with the observed transition from a 'glassy' to 'rubbery' state. Both types of multilayer assemblies displayed plasticization with increasing sodium chloride concentration in the adjoining aqueous phase, i.e. saloplasticity, and exhibited a transition from elastic to plastic response to deformation. The restored mobility of the polyelectrolyte resulting from the shift from intrinsic to extrinsic charge complexation, restores fluidity to the interface and is evidenced by experimental observation of a liquid-like interface when loaded. The higher molecular weight polyanion multilayers plasticized at lower salt concentrations suggesting that the lower melting point of the higher molecular weight polyanion assembly is attributable to a lesser extent of electrostatic cross-linking underscoring the unconventional dependence of molecular weight on saloplasticity in strongly dissociated polyelectrolytes.

Highly sensitive refractive index sensor based on a TiO2 nanowire array.

We propose a novel, highly sensitive refractive index (RI) sensor by means of combining the Kretschmann prism with a TiO2 nanowire array and do not use a metallic layer in the Kretschmann configuration. Its RI sensing performance was investigated through measuring different concentrations of sodium chloride solution. Experimental results showed that, with increasing RI of liquid, the resonant wavelength in the reflectance spectrum redshifted gradually in the visible light range. There was a very good linear relationship between resonant wavelength and RI in the range of 1.3330 to 1.3546. More importantly, in contrast to the surface plasmon resonance (SPR) sensor, the interferometric sensors showed higher sensitivity to the external RI. In the case of the transverse magnetic mode, the RI sensitivity is up to 320,700.93 a.u./RIU (refractive index unit) by expression of light intensity, which is 9.55 times that of the SPR sensor. As for the transverse electric mode, it achieves 4371.76 nm/RIU by expression of the resonant wavelength, which is increased by a factor of 1.4 in comparison with the SPR sensor. Moreover, the experimental results have favorable repeatability. A TiO2 nanowire array sensor has also other advantages, such as easy manufacturing, low cost, and in situ determination, etc. To our knowledge, this fact is reported for the first time. It has great potential applications in the field of biological and chemical sensing.

An Ultrasensitive Long-Period Fiber Grating-Based Refractive Index Sensor with Long Wavelengths.

The response of a novel long-period fiber grating (LPFG) with a period of 180 µm to a surrounding refractive index (RI) was investigated. The results displayed that, with the increase in RI of the surrounding media of cladding glass in the grating region, the resonant peak located at 1336.4 nm in the transmission spectrum gradually shifts towards a shorter wavelength, while the resonant peak located at 1618 nm gradually shifted towards a longer wavelength. Moreover, the resonant peak at 1618 nm is much more sensitive to the surrounding RI than that of the one at 1336.4 nm. Compared with the conventional LPFG and other types of wavelength-interrogated RI sensors, such as ring resonators, surface plasmon resonance sensors, and Fabry-Perot interferometric sensors, this novel LPFG possesses a higher sensitivity, which achieved 10,792.45 nm/RIU (RI unit) over a RI range of 1.4436-1.4489.

Customization of Protein Single Nanowires for Optical Biosensing.

An all-protein single-nanowire optical biosensor is constructed by a facile and general femtosecond laser direct writing approach with nanoscale structural customization. As-formed protein single nanowires show excellent optical properties (fine waveguiding performance and bio-applicable transmission windows), and are utilized as evanescent optical nanobiosensors for label-free biotin detection.

Ultrasensitive Detection of Testosterone Using Microring Resonator with Molecularly Imprinted Polymers.

We report ultrasensitive and highly selective detection of testosterone based on microring resonance sensor using molecularly imprinted polymers (MIP). A silicon-on-insulator (SOI) micoring resonator was modified by MIP films (MIPs) on a surface. The MIPs was synthesized by thermopolymerization using methacrylic acid as functional monomer and ethylene glycol dimethacrylate as crosslinking agent. The concentration of detected testosterone varies from 0.05 ng/mL to 10 ng/mL. The detection limit reaches 48.7 pg/mL. Ultrahigh sensitivity, good specificity and reproducibility have been demonstrated, indicating the great potential of making a cost effective and easy to operate lab-on-Chip and down scaling micro-fluidics devices in biosensing.