Single Silicon Nanowire‐Based Fluorescent Sensor for Endogenous Hypochlorite in an Individual Cell

Abstract

it is of vital importance to monitor the hypochlorite.So far, many fluorescent probes have been reported for selective signaling of the hypochlorite and they possess great merits such as high sensitivity, fast response time, etc. [5] Owing to some limitations of these research, most sensors would only be able to investigate large numbers of cells. Based on the assumption that the average response represents typical cells within the population, the traditional cellbased assays just measure the average response of cell populations. [6] However, there are significant differences among individuals of the same type of cells. [7] So such average cannot accurately reflect the response from an individual cell and may result in a misleading interpretation. The accurate determination of the hypochlorite at single-cell level could reveal the essence of hypochlorite in life activities and enable physiologists and pathologists to explore the causes of hypochlorite-related diseases and obtain more reliable scientific basis for the development and treatment of the diseases. [8] Thus, it is highly desirable to fabricate a proper fluorescent sensor which could be used to investigate the dynamic activity of the hypochlorite and reveal the biological role of hypochlorite in a single cell.Currently, single-cell study at the nanoscale can present in forms such as pillars, [9] tubes, [10] and wires. [11] These materials as probes are gently inserted into a cell and show great advantages [12] such as active insertion into the cell at the location as we need, realizing subcellular resolution, label-free for a specific location in the cell, decreasing diffusion distance, etc. [13] Modifying a proper molecule on an appropriate anchoring carrier would be a rational strategy to construct sensors for single-cell research. Among the nanomaterials, silicon nanowires (SiNWs) are a competitive alternative as the anchoring substrate. [14] Compared with other nanomaterials, SiNWs own many virtues such as nontoxicity, high stability, easy modification, and praiseworthy biocompatibility. Especially, it can be easily fabricated in good straightness, rigidity, and different lengths. Therefore, it is very favorable to utilize the SiNWs as the anchoring substrate to construct a single nanowire-based sensor for biological detection in a single cell.In this study, we have constructed a single SiNW-based fluorescent sensor for hypochlorite and realized its application in an individual cell with the assistance of micromanipulation and As a prototype of a single-cell detecting technique, a single silicon nanowire-based (SiNW-based) fluorescent sensor for endogenous hypochlorite in a macrophage is constructed. The fluorescent sensor for hypochlorite is prepared by decorating a near-infrared dye, IR780 onto the surface of SiNWs. The sensor exhibits high sensitivity and linear dependence of the fluorescence intensities on the hypochlorite concentrations. With the help of micromanipulation and laser scanning confocal microscopy, detection of endogenous hypoc...

Fluorescent Biosensors Based on Silicon Nanowires

“…By being physically locating in a single cell, the 1D fluorescence sensor could avoid the leakage of small molecules and drift of nanoparticles for cell imaging [34]. For silicon nanostructures, Si NWs arose as a competitive alternative as the an-choring substrate to construct sensors for single-cell research [56,89].…”

“…As far as the fabrication of Si NWs-based fluorescent sensors is concerned, it is possible to generalize 3 types of major Si NW applications as schematized in Figure 1. In particular, (a) Si NWs (or a single Si NW) coupled with fluorescent biomolecules can be employed and used as a substrate [33,34,55,56], (b) metal decorated Si NWs coupled with fluorescent biomolecules can be used as quencher according to the structural conformation of the functionalized material (i.e., quenching when the dye is in close proximitity to gold NP decorated Si NWs) [96,97], (c) light-emitting Si NW directly used as biosensor based on their photoluminescence (PL) quenching [101][102][103]. During the next sections, each one of these interesting strategies will be presented, discussing their major advantages and drawbacks and the type of applications where they have been reported so far.…”

“…Cao et al report on the fabrication of a Si NW sensor for an important reactive species, hypochlorous acid (HClO) [34]. HClO plays a critical role against pathogens in our body [119,120] and can be also found in dissociate hypochlorite ion form (ClO -) [121].…”

“…Si NW sensors were successfully tested not only with the direct target recognition, but also in a system that mimes the HClO production of our enzymatic system [126,127], demonstrating the ability to detect hypochlorite in living organisms. As schematized in Figure 2d, the authors reported on the possibility to load the tip of a micropipette with a single Si NW sensor that can be micromanipulated to be inserted inside cells for fluorescence imaging through confocal microscopy analysis [34]. This result opens the route to the intracellular application of a single Si NW sensor that can be used in intracellular systems.…”

“…Indeed, the development of fluorescent probes that can be precisely located inside the cells is a highly demanded point to investigate certain biomolecule target activity revealing their biological roles [33]. So far, several organic fluorophores have been reported in the literature [34][35][36]. One of the main advantages of organic fluorophores is their readily cost-effective availability.…”