The escape of bladder cancer from immunosurveillance causes monotherapy to exhibit poor efficacy; therefore, designing a multifunctional nanoparticle that boosts programmed cell death and immunoactivation has potential as a treatment strategy. Herein, we developed a facile one-pot coprecipitation reaction to fabricate cluster-structured nanoparticles (CNPs) assembled from Fe3O4 and iron chlorophyll (Chl/Fe) photosensitizers. This nanoassembled CNP, as a multifunctional theranostic agent, could perform red-NIR fluorescence and change the redox balance by the photoinduction of reactive oxygen species (ROS) and attenuate iron-mediated lipid peroxidation by the induction of a Fenton-like reaction. The intravesical instillation of Fe3O4@Chl/Fe CNPs modified with 4-carboxyphenylboronic acid (CPBA) may target the BC wall through glycoproteins in the BC cavity, allowing local killing of cancer cells by photodynamic therapy (PDT)-induced singlet oxygen and causing chemodynamic therapy (CDT)-mediated ferroptosis. An interesting possibility is reprogramming of the tumor microenvironment from immunosuppressive to immunostimulatory after PDT-CDT treatment, which was demonstrated by the reduction of PD-L1 (lower “off” signal to the effector immune cells), IDO-1, TGF-β, and M2-like macrophages and the induction of CD8+ T cells on BC sections. Moreover, the intravesical instillation of Fe3O4@Chl/Fe CNPs may enhance the large-area distribution on the BC wall, improving antitumor efficacy and increasing survival rates from 0 to 91.7%. Our theranostic CNPs not only demonstrated combined PDT-CDT-induced cytotoxicity, ROS production, and ferroptosis to facilitate treatment efficacy but also opened up new horizons for eliminating the immunosuppressive effect by simultaneous PDT-CDT.
We demonstrated a highly-sensitive, wafer-scale, highly-uniform plasmonic nano-mushroom substrate based on plastic for naked-eye plasmonic colorimetry and surface-enhanced Raman spectroscopy (SERS). We gave it the name FlexBrite. The dual-mode functionality of FlexBrite allows for label-free qualitative analysis by SERS with an enhancement factor (EF) of 10(8) and label-free quantitative analysis by naked-eye colorimetry with a sensitivity of 611 nm RIU(-1). The SERS EF of FlexBrite in the wet state was found to be 4.81 × 10(8), 7 times stronger than in the dry state, making FlexBrite suitable for aqueous environments such as microfluid systems. The label-free detection of biotin-streptavidin interaction by both SERS and colorimetry was demonstrated with FlexBrite. The detection of trace amounts of the narcotic drug methamphetamine in drinking water by SERS was implemented with a handheld Raman spectrometer and FlexBrite. This plastic-based dual-mode nano-mushroom substrate has the potential to be used as a sensing platform for easy and fast analysis in chemical and biological assays.
Colorimetric techniques provide a useful approach for sensing application because of their low cost, use of inexpensive equipment, requirement of fewer signal transduction hardware, and, above all, their simple-to-understand results. Colorimetric sensor can be used for both qualitative analyte identification as well as quantitative analysis for many application areas such as clinical diagnosis, food quality control, and environmental monitoring. A gap exists between high-end, accurate, and expensive laboratory equipment and low-cost qualitative point-of-care testing tools. Here, we present a label-free plasmonic-based colorimetric sensor fabricated on a transparent plastic substrate consisting of about one billion nanocups in an array with a subwavelength opening and decorated with metal nanoparticles on the side walls, to bridge that gap. The fabrication techniques of the plasmonic sensor, integration to portable microfluidic devices for lab on chip applications, demonstration of highly sensitive refractive-index sensing, DNA hybridization detection, and protein-protein interaction will be reviewed. Further, we anticipate that the colorimetric sensor can be applied to point-of-care diagnostics by utilizing proper surface functionalization techniques, which seems to be one of the current limiting factors. Finally, the future outlook for the colorimetric plasmonic sensors is discussed.
Comparison between surface-enhanced Raman scattering (SERS) on optically absorbing and nonabsorbing nanostructured substrates has been conducted. Nanostructured Si and Si 3 N 4 substrates covered with silver nanoparticles (AgNPs) were prepared by identical fabrication process based on metal thin film thermal dewetting technique. Images of scanning electron microscopy (SEM) show similar morphology between both devices. According to finite difference time domain (FDTD) simulation, electric field enhancement from localized surface plasmon resonance (LSPR) is stronger in nonabsorbing Si 3 N 4 substrate in comparison to that of the optically absorbing Si with the same structures. The results of Raman measurements agree with FDTD simulated results and consistently show that the enhancement factor (EF) of nanostructured Si 3 N 4 SERS device is higher than that of Si by around 4 times for various targeted analytes and excitation wavelengths. This suggests that optically nonabsorbing material is more appropriate as SERS substrate as compared to absorbing material. ■ INTRODUCTIONSurface-enhanced Raman spectroscopy (SERS) has been discovered a few decades ago and continues to play a significant role in label-free biological and chemical sensing. 1,2 The Raman scattering, which originates from vibrational modes of molecules, results in wavelength-shift peaks in spectra according to different molecular configurations. 3 Therefore, molecular information such as chemical bonding, composition, and intermolecular interaction can be unambiguously identified from Raman spectrum. 4 However, traditional Raman spectroscopy suffers from insufficient Raman scattering cross-section and thus is difficult to apply to low concentration measurement. This hindrance has been overcome by SERS, which amplifies Raman signal significantly by applying roughened metal surfaces or isolated metal nanoparticles in proximity of the targeted analyte. This technique permits the sensing of ultralow concentration to the degree of single molecule detection. 5−7 The physics of this phenomenon can be explained by the combination of electromagnetic (EM) and charge transferring (CT) mechanisms. 8 Between these two models, EM mechanism constitutes a significantly higher contribution to the ultrahigh enhancement of SERS. The enhancement is based on localized surface plasmon resonance (LSPR) of nanoscale structure of metal. 4 By coupling incident and Raman scattering light into LSPR, the intensity of the original Raman signal can be enhanced by approximately the fourth order of the electric field amplitude enhancement. 9 SERS devices have been thus far designed and fabricated by plenty of different methods. In these methods, different kinds of substrate material such as silicon, 10 III−V semiconductor, 11 transparent conductive metal oxide, 12 dielectric, 13 and polymer have been demonstrated. 14 In addition, previous studies have proved that LSPR is sensitive to the surrounding environment 15 and metal thin film adhesion. 16 However, there is no study specifically...
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