Long-term and real-time investigation of the dynamic process of pHi changes is critically significant for understanding the related pathogenesis of diseases and the design of intracellular drug delivery systems. Herein, we present a one-step synthetic strategy to construct ratiometric pH sensors, which are made of europium (Eu)-doped one-dimensional silicon nanorods (Eu@SiNRs). The as-prepared Eu@SiNRs have distinct emission maxima peaks at 470 and 620 nm under 405 nm excitation. Of particular note, the fluorescence emission intensity at 470 nm decreases along with the increase of pH, while the one at 620 nm is nearly unaffected by pH changes, making Eu@SiNRs a feasible probe for pH sensing ratiometrically. Moreover, Eu@SiNRs are found to be responsive to a broad pH range (ca. 3–9), biocompatible (e.g., ∼100% of cell viability during 24 h treatment) and photostable (e.g., ∼10% loss of intensity after 40 min continuous UV irradiation). Taking advantages of these merits, we employ Eu@SiNRs for the visualization of the cytoplasmic alkalization process mediated by nigericin in living cells, for around 30 min without interruption, revealing important information for understanding the dynamic process of pHi fluctuations.

There is an increasing interest in the development of surface-enhanced Raman scattering (SERS) sensors for rapid and accurate on-site detection of hidden explosives. However, portable SERS methods for trace explosive detection in real systems remain scarce, mainly due to their relatively poor reliability and portability. Herein, we present the first demonstration of a portable silicon-based SERS analytical platform for signal-on detection of trace trinitrotoluene (TNT) explosives, which is made of silver nanoparticle (AgNP)-decorated silicon wafer chip (0.5 cm × 0.5 cm). In principle, under 514 nm excitation, the Raman signals of p-aminobenzenethiol (PABT) modified on the AgNP surface could be largely lit up due to the formation of electronic resonance-active TNT–PABT complex. In addition, the surface of AgNPs and silicon substrate-induced plasmon resonances also contribute the total SERS enhancement. For quantitative evaluation, the as-prepared chip features ultrahigh sensitivity [limit of detection is down to ∼1 pM (∼45.4 fg/cm2)] and adaptable reproducibility (relative standard deviation is less than 15%) in the detection of TNT standard solutions. More importantly, the developed chip can couple well with a hand-held Raman spectroscopic device using 785 nm excitation, suitable for qualitative analysis of trace TNT even at ∼10–8 M level from environmental samples including lake water, soil, envelope, and liquor with a short data acquisition time (∼1 min). Furthermore, TNT vapors diffusing from TNT residues (∼10–6 M) can be detected by using such a portable device, indicating its feasibility in determination of hidden samples.

Fluorescent imaging techniques for visualization of nuclear structure and function in live cells are fundamentally important for exploring major cellular events. The ideal cellular labeling method is capable of realizing label-free, in situ, real-time, and long-term nucleus labeling in live cells, which can fully obtain the nucleus-relative information and effectively alleviate negative effects of alien probes on cellular metabolism. However, current established fluorescent probes-based strategies (e.g., fluorescent proteins-, organic dyes-, fluorescent organic/inorganic nanoparticles-based imaging techniques) are unable to simultaneously realize label-free, in situ, long-term, and real-time nucleus labeling, resulting in inevitable difficulties in fully visualizing nuclear structure and function in live cells. To this end, we present a type of bioinspired fluorescent probes, which are highly efficacious for in situ and label-free tracking of nucleus in long-term and real-time manners. Typically, the bioinspired polydopamine (PDA) nanoparticles, served as fluorescent probes, can be readily synthesized in situ within live cell nucleus without any further modifications under physiological conditions (37 °C, pH ∼7.4). Compared with other conventional nuclear dyes (e.g., propidium iodide (PI), Hoechst), superior spectroscopic properties (e.g., quantum yield of ∼35.8% and high photostability) and low cytotoxicity of PDA-based probes enable long-term (e.g., 3 h) fluorescence tracking of nucleus. We also demonstrate the generality of this type of bioinspired fluorescent probes in different cell lines and complex biological samples.

The biological toxicity of nanomaterials is a concern because they have many potential applications in biomedical fields. In this study, silkworm hemolymph was exposed to high-dose cadmium telluride quantum dots (CdTe QDs), citric-acid–nitrogen-doped carbon dots (C–NCDs), or silicon nanoparticles (SiNPs) and the differences in the immune responses and programmed cell death induced in hemocytes were compared. Changes in the expression of innate-immunity-related genes and the occurrence of hemocytes in the hemolymph indicated that the three types of nanomaterials entered several types of hemocytes by endocytosis, but their toxicity differed significantly. C–NCDs only induced autophagy in the hemocytes, whereas SiNPs induced both hemocyte autophagy and the simultaneous apoptosis of a large number of cells. CdTe QD exposure rapidly induced hemocyte apoptosis and necrosis. The mechanisms of hemocyte apoptosis induced by the different nanomaterials differed significantly. The apoptosis induced by CdTe QDs was dependent on the lysosomal apoptotic pathway, whereas SiNPs also used the endoplasmic reticulum apoptotic pathway. The autophagy and even apoptosis that appeared in the hemocytes after SiNP exposure quickly self-repaired, whereas the autophagy induced in hemocytes by C–NCD exposure persisted.

Extensive investigations have been carried out for evaluating the toxicology of various nanomaterials (e.g., carbon- and metal-based nanomaterials), which offer invaluable information for assessing the feasibility of nanomaterial-based wide-ranging applications. In recent years, sufficient efforts have been made to develop fluorescent small-sized silicon nanoparticles (SiNPs) as a novel optical material simultaneously featuring strong fluorescence and ultrahigh photostability, providing high promise for a myriad of biological, biomedical and electronic applications. It is worth pointing out that, despite the non- or low-toxicity of silicon, sufficient and objective toxicology evaluation of SiNPs is urgently required at both the in vitro and in vivo levels. However, there currently exists scanty information about the intracellular behaviors of the SiNPs, particularly the underlying mechanism of entry into cells and intracellular fate. Herein, we present a report aimed at determining the uptake and intracellular transport of SiNPs of ca. 4 nm diameter. Taking advantage of the strong and stable fluorescent signals of SiNPs, we reveal that these small-sized SiNPs accumulate in the plasma membrane prior to internalization, and are further internalized predominantly by clathrin-mediated and caveolae-dependent endocytosis. After endocytosis, the SiNPs are localized in early endosomes within a short time (∼1 h), while in up to 24 h of incubation the SiNPs are mainly transported to lysosomes in a microtubule-dependent way; and interestingly, to a smaller extent are sorted to the Golgi apparatus. Moreover, we demonstrate that there are no toxic effects of SiNPs on the cell metabolic activity and integrity of the plasma membrane.

Extensive investigations have been carried out for evaluating the toxicology of various nanomaterials (e.g., carbon- and metal-based nanomaterials), which offer invaluable information for assessing the feasibility of nanomaterial-based wide-ranging applications. In recent years, sufficient efforts have been made to develop fluorescent small-sized silicon nanoparticles (SiNPs) as a novel optical material simultaneously featuring strong fluorescence and ultrahigh photostability, providing high promise for a myriad of biological, biomedical and electronic applications. It is worth pointing out that, despite the non- or low-toxicity of silicon, sufficient and objective toxicology evaluation of SiNPs is urgently required at both the in vitro and in vivo levels. However, there currently exists scanty information about the intracellular behaviors of the SiNPs, particularly the underlying mechanism of entry into cells and intracellular fate. Herein, we present a report aimed at determining the uptake and intracellular transport of SiNPs of ca. 4 nm diameter. Taking advantage of the strong and stable fluorescent signals of SiNPs, we reveal that these small-sized SiNPs accumulate in the plasma membrane prior to internalization, and are further internalized predominantly by clathrin-mediated and caveolae-dependent endocytosis. After endocytosis, the SiNPs are localized in early endosomes within a short time (∼1 h), while in up to 24 h of incubation the SiNPs are mainly transported to lysosomes in a microtubule-dependent way; and interestingly, to a smaller extent are sorted to the Golgi apparatus. Moreover, we demonstrate that there are no toxic effects of SiNPs on the cell metabolic activity and integrity of the plasma membrane.

We herein present the first example of one-dimensional silicon nanostructures (i.e., silicon nanoshuttles (SiNSs)), which simultaneously feature bright fluorescence, robust photostability, and distinct paramagnetism. This type of SiNSs, prepared through one-pot microwave chemical synthesis in a rapid and facile manner, hold high promise for various optical and magnetic applications.

By using gramineae plants as natural and accessible reaction precursors, we herein introduce a green synthetic strategy, which is efficacious for the facile production of crystalline, excitation-wavelength-dependent fluorescent and small-sized silicon nanoparticles (SiNPs). We further explore the prepared SiNPs as a novel kind of fluorescent label for anti-counterfeiting applications.

It is of great significance to accurately and reliably detect trace lead(II) (Pb2+) ions, preferably at sub-nM level due to the possible long-term accumulation of Pb2+ in the human body, which may cause serious threats to human health. However, a suitable Pb2+ sensor meeting the demands is still scanty. Herein, we develop a polyadenine-assisted, surface-enhanced Raman scattering (SERS) silicon chip (0.5 cm × 0.5 cm) composed of core (Ag)-satellite (Au) nanoparticles (Ag–Au NPs)-decorated silicon wafers (Ag–Au NPs@Si) for high-performance Pb2+ detection. Typically, strong SERS signals could be measured when DNAzyme conjugated on the SERS silicon chip is specifically activated by Pb2+, cleaving the substrate strand into two free DNA strands. A good linearity exists between the normalized Raman intensities and the logarithmic concentrations of Pb2+ ranging from 10 pM to 1 μM with a good correlation coefficient, R2 of 0.997. Remarkably, Pb2+ ions with a low concentration of 8.9 × 10–12 M can be readily determined via the SERS silicon chip ascribed to its superior SERS enhancement, much lower than those (∼nM) reported by other SERS sensors. Additionally, the developed chip features good selectivity and recyclability (e.g., ∼11.1% loss of Raman intensity after three cycles). More importantly, the as-prepared chip can be used for accurate and reliable determination of unknown Pb2+ ions in real systems including lake water, tap water and industrial wastewater, with the RSD value less than 12%.

Fluorescent sensors suitable for dynamic measurement of intracellular pH (pHi) fluctuations should feature the following properties: feeble cytotoxicity, wide-pH range response, and strong fluorescence coupled with good photostability, which are still remaining scanty to date. Herein, by functionalizing fluorescent silicon nanoparticles (SiNPs) with pH-sensitive dopamine (DA) and pH-insensitive rhodamine B isothiocyanate (RBITC), we present the first demonstration of fluorescent SiNPs-based sensors, simultaneously exhibiting minimal toxicity (cell viability of treated cells remains above 95% during 24-h treatment), sensitive fluorescent response to a broad pH range (∼4–10), and bright fluorescence coupled with robust photostability (∼9% loss of fluorescence intensity after 40 min continuous excitation; in contrast, fluorescence of Lyso-tracker is rapidly quenched in 5 min under the same experiment conditions). Taking advantage of these merits, we further employ the resultant fluorescent SiNPs sensors for the detection of lysosomal pH change mediated by nigericin in live HeLa and MCF-7 cells in long-term (e.g., 30 min) manners. Interestingly, two consecutive stages, i.e., alkalization lag phase and logarithmic growth phase, are observed based on recording the whole process of pH change, offering important information for understanding the dynamic process of pHi fluctuations.

During the past few decades, thanks to silicon nanomaterials’ outstanding electronic/optical/mechanical properties, large surface-to-volume ratio, abundant surface chemistry, facile tailorability and good compatibility with modern semiconductor industry, different dimensional silicon nanostructures have been widely employed for rationally designing and fabricating high-performance surface-enhanced Raman scattering (SERS) sensors for the detection of various chemical and biological species. Among these, two-dimensional silicon nanostructures made of metal nanoparticle-modified silicon wafers and three-dimensional silicon nanostructures made of metal nanoparticle-decorated SiNW arrays are of particular interest, and have been extensively exploited as promising silicon-based SERS-active substrates for the construction of high-performance SERS sensors. With an aim to retrospect these important and exciting achievements, we herein focus on reviewing recent representative studies on silicon-based SERS sensors for sensing applications from a broad perspective and possible future direction, promoting readers’ awareness of these novel powerful silicon-based SERS sensing technologies. Firstly, we summarize the two unique merits of silicon-based SERS sensors, and those are high sensitivity and good reproducibility. Next, we present recent advances of two- and three-dimensional silicon-based SERS sensors, especially for real applications. Finally, we discuss the major challenges and prospects for the development of silicon-based SERS sensors.

Safe fluorescent gene-transfection vectors are in great demand for basic biological applications and for gene-therapy research. Here, we introduce a new type of luminescent silicon nanoparticle (SiNP)-based gene carrier suitable for determining the intracellular fate of the gene vehicle in a long-term and real-time manner. The presented SiNP-based nanocarriers simultaneously feature strong and stable fluorescence, high DNA-loading capacity and gene-transfection efficiency, as well as favorable biocompatibility. Taking advantage of these unique benefits, we were able to readily observe the behavior of the gene carriers in live cells (e.g. cellular uptake, intracellular trafficking, and endosomal escape) in a long-term and real-time manner. The results demonstrate the potential usability of these fluorescent SiNP-based gene vectors as powerful tools in the field of gene therapy, and provide invaluable information for understanding the intracellular behavior of gene carriers.

Fluorescent silicon nanoparticles (SiNPs), as the most important zero-dimensional silicon nanostructures, hold high promise for long-awaited silicon-based optic applications. There currently remain major challenges for the green, inexpensive, and mass production of fluorescent SiNPs, resulting in difficulties in sufficiently exploiting the properties of these remarkable materials. Here, we show that fluorescent small-sized (∼3.8 nm) SiNPs can be produced through biomimetic synthesis in rapid (10 min), low-cost, and environmentally benign manners. The as-prepared SiNPs simultaneously feature bright fluorescence (quantum yield (QY), ∼15–20%), narrow emission spectral width (full width at half-maximum (fwhm), ∼30 nm), and nontoxicity, making them as high-quality fluorescent probes for biological imaging in vitro and in vivo.

We herein introduce a kind of fluorescent silicon nanoparticles (SiNPs) bioprobes, that is, peptides-conjugated SiNPs, which simultaneously feature small sizes (<10 nm), biological functionality, and stable and strong fluorescence (photoluminescent quantum yield (PLQY): ∼28%), as well as favorable biocompatibility. Taking advantage of these merits, we further demonstrate such resultant SiNPs bioprobes are superbly suitable for real-time immunofluorescence imaging of cancer cells. Meanwhile, malignant tumor cells could be specifically destroyed by the peptides-conjugated SiNPs, suggesting potential promise of simultaneous detection and treatment of cancer cells.

It is of essential importance to precisely probe mercury(II) (Hg2+) ions for environment-protection analysis and detection. To date, there still remain major challenges for accurate, specific, and reliable detection of Hg2+ ions at subppt level. We herein employ gold nanoparticles (AuNPs) decorated silicon nanowire array (SiNWAr) as active surface-enhanced Raman scattering (SERS) substrates to construct a high-performance sensing platform assisted by DNA technology, enabling ultrasensitive detection of trace Hg2+ in ∼64 min and with low sample consumption (∼30 μL). Typically, strong SERS signals could be detected when the single-stranded DNA structure converts to the hairpin structure in the presence of Hg2+ ions, due to the formation of thymine (T)-Hg2+-T. As a result, Hg2+ ions with a low concentration of 1 pM (0.2 ppt) can be readily discriminated, much lower than those (∼nM) reported for conventional analytical strategies. Water samples spiked with various Hg2+ concentrations are further tested, exhibiting a good linear relationship between the normalized Raman intensities and the logarithmic concentrations of Hg2+ ranging from 1 pM to 100 nM, with a correlation coefficient of R2 = 0.998. In addition, such SERS sensor features excellent selectivity, facilely distinguishing Hg2+ ions from various interfering substances. Moreover, this presented SERS sensor possesses good recyclability, preserving adaptable reproducibility during 5-time cyclic detection of Hg2+. Furthermore, unknown Hg2+ concentration in river water can be readily determined through our sensing strategy in accurate and reliable manners, with the RSD value of ∼9%.

In this article, we introduce a Poly adenine (Poly A)-assisted fabrication method for rationally designing surface-enhanced resonance Raman scattering (SERRS) substrates in controllable and reliable manners, enabling construction of core–satellite SERRS assemblies in both aqueous and solid phase (e.g., symmetric core (Au)-satellite (Au) nanoassemblies (Au–Au NPs), and asymmetric Ag–Au NPs-decorated silicon wafers (Ag–Au NPs@Si)). Of particular significance, assembly density is able to be controlled by varying the length of the Poly A block (e.g., 10, 30, and 50 consecutive adenines at the 5′ end of DNA sequence, Poly A10/A30/A50), producing the asymmetric core–satellite nanoassemblies with adjustable surface density of Au NPs assembly on core NPs surface. Based on quantitative interrogation of the relationship between SERRS performance and assemble density, the Ag–Au NPs@Si featuring the strongest SERRS enhancement factor (EF ≈ 107) and excellent reproducibility can be achieved under optimal conditions. We further employ the resultant Ag–Au NPs@Si as a high-performance SERRS sensing platform for the selective and sensitive detection of mercury ions (Hg2+) in a real system, with a low detection limit of 100 fM, which is ∼5 orders of magnitude lower than the United States Environmental Protection Agency (USEPA)-defined limit (10 nM) in drinkable water. These results suggest the Poly A-mediated assembly method as new and powerful tools for designing high-performance SERRS substrates with controllable structures, facilitating improvement of sensitivity, reliability, and reproducibility of SERRS signals.

We herein introduce a facile, low-cost photochemical method capable of rapid (<40 min) and large-quantity (∼10 g) production of highly fluorescent (quantum yield: 25%) silicon nanoparticles (SiNPs) of tunable optical properties (peak emission wavelength in the range of 470–560 nm) under ambient air conditions, by introducing 1,8-naphthalimide as a reducing agent and surface ligands. The as-prepared SiNPs feature robust storage stability and photostability preserving strong and stable fluorescent during long-term (>3 h) high-power UV irradiation, in contrast to the rapid fluorescence quenching within 2 h of conventional organic dyes and II–VI quantum dots under the same conditions. The as-prepared SiNPs serving as photostable nanoprobes are workable for cellular imaging in long-term manners. Our findings provide a powerful method for mild-condition and low-cost, large-quantity production of highly fluorescent and photostable SiNPs for various promising applications.Keywords: bioimaging; large-quantity; long-term; photochemical; silicon nanoparticles;

Silicon nanomaterials are an important class of nanomaterials with great potential for technologies including energy, catalysis, and biotechnology, because of their many unique properties, including biocompatibility, abundance, and unique electronic, optical, and mechanical properties, among others. Silicon nanomaterials are known to have little or no toxicity due to favorable biocompatibility of silicon, which is an important precondition for biological and biomedical applications. In addition, huge surface-to-volume ratios of silicon nanomaterials are responsible for their unique optical, mechanical, or electronic properties, which offer exciting opportunities for design of high-performance silicon-based functional nanoprobes, nanosensors, and nanoagents for biological analysis and detection and disease treatment. Moreover, silicon is the second most abundant element (after oxygen) on earth, providing plentiful and inexpensive resources for large-scale and low-cost preparation of silicon nanomaterials for practical applications. Because of these attractive traits, and in parallel with a growing interest in their design and synthesis, silicon nanomaterials are extensively investigated for wide-ranging applications, including energy, catalysis, optoelectronics, and biology. Among them, bioapplications of silicon nanomaterials are of particular interest.In the past decade, scientists have made an extensive effort to construct a silicon nanomaterials platform for various biological and biomedical applications, such as biosensors, bioimaging, and cancer treatment, as new and powerful tools for disease diagnosis and therapy. Nonetheless, there are few review articles covering these important and promising achievements to promote the awareness of development of silicon nanobiotechnology.In this Account, we summarize recent representative works to highlight the recent developments of silicon functional nanomaterials for a new, powerful platform for biological and biomedical applications, including biosensor, bioimaging, and cancer therapy. First, we show that the interesting photoluminescence properties (e.g., strong fluorescence and robust photostability) and excellent biocompatibility of silicon nanoparticles (SiNPs) are superbly suitable for direct and long-term visualization of biological systems. The strongly fluorescent SiNPs are highly effective for bioimaging applications, especially for long-term cellular labeling, cancer cell detection, and tumor imaging in vitro and in vivo with high sensitivity. Next, we discuss the utilization of silicon nanomaterials to construct high-performance biosensors, such as silicon-based field-effect transistors (FET) and surface-enhanced Raman scattering (SERS) sensors, which hold great promise for ultrasensitive and selective detection of biological species (e.g., DNA and protein). Then, we introduce recent exciting research findings on the applications of silicon nanomaterials for cancer therapy with encouraging therapeutic outcomes. Lastly, we highlight the major challenges and promises in this field, and the prospect of a new nanobiotechnology platform based on silicon nanomaterials.

In this article, we present a kind of silicon-based antibacterial material made of silver nanoparticle (AgNP)-decorated silicon wafers (AgNP@Si), which is facilely and rapidly (30 min) synthesized via a one-step reaction. Significantly, such a resultant silicon-based antibacterial material features stable and high antibacterial activity, preserving >99% antibacterial efficiency against E. coli during 30 day storage.

The first example of silicon nanowire (SiNW)-based in vivo tumor phototherapy is presented. Gold nanoparticle (AuNP)-decorated SiNWs are employed as high-performance NIR hyperthermia agents for highly efficacious in vivo tumour ablation. Significantly, the overall survival time of SiNW-treated mice is drastically prolonged, with 100% of mice being alive and tumor-free for over 8 months, which is the longest survival time ever reported for tumor-bearing mice treated with nanomaterial-based NIR hyperthermia agents.

Surface-enhanced Raman scattering (SERS) is well-recognized as a powerful analytical tool for ultrahighly sensitive detection of analytes. In this article, we present a kind of silicon-based SERS sensing platform made of a hairpin DNA-modified silver nanoparticles decorated silicon wafer (AgNPs@Si). In particular, the AgNPs@Si with a high enhancement factor (EF) value of ∼4.5 × 107 is first achieved under optimum reaction conditions (i.e., pH = 12, reaction time = 20 min) based on systematic investigation. Such resultant AgNPs@Si is then employed for construction of a silicon-based SERS sensing platform through surface modification of hairpin DNA, which is superbly suitable for highly reproducible, multiplexed, and ultrasensitive DNA detection. A detection limit of 1 fM is readily achieved in a very reproducible manner along with high specificity. Most significantly, for the first time, we demonstrate that the silicon-based SERS platform is highly efficacious for discriminating deafness-causing mutations in a real system at the femtomolar level (500 fM), which is about 3–4 orders of magnitude lower than that (∼5 nM) ever reported by conventional detection methods. Our results raise the exciting potential of practical SERS applications in biology and biomedicine.

•The synthetic strategies of fluorescent quantum dots were discussed.•Fluorescent quantum dots-based biomedical optical imaging applications were reviewed.•Risk assessment of fluorescent quantum dots was described.The marriage of nanomaterials with biology has significantly promoted advancement of biological techniques, profoundly facilitating basic research and practical applications in biological and biomedical fields. Taking advantages of unique optical properties (e.g., strong fluorescence, robust photostability, size-tunable emission wavelengths, etc.), fluorescent quantum dots (QDs), appearing as high-performance biological fluorescent nanoprobes, have been extensively explored for a variety of biomedical optical imaging applications. In this review, we present representative synthetic strategies for preparation of QDs and their applications in biomedical optical imaging, as well as risk assessments in vitro and in vivo. Briefly, we first summarize recent progress in fabrication of QDs via two rudimentary approaches, i.e., organometallic route and aqueous synthesis. Next we present representative achievement in QDs-based in vitro and in vivo biomedical optical imaging applications. We further discuss the toxicity assessment of QDs, ranging from cell studies to animal models. In the final section, we discuss challenges and perspectives for the QDs-relative bioapplications in the future.

A large-scale synthetic strategy is developed for facile one-pot aqueous synthesis of silicon nanoparticles (SiNPs) yielding ∼0.1 g SiNPs of small sizes (∼2.2 nm) in 10 min. The as-prepared SiNPs feature strong fluorescence (photoluminescence quantum yield of 20–25%), favorable biocompatibility, and robust photo- and pH-stability. Moreover, the SiNPs are naturally water dispersible, requiring no additional post-treatment. Such SiNPs can serve as highly photostable bioprobes and are superbly suitable for long-term immunofluorescent cellular imaging.

Surface-enhanced Raman scattering (SERS) is well recognized as a powerful analytical tool, enabling ultrahigh sensitive detection of analytes at low concentrations, even down to single-molecule level. Of particular note, in comparison to sufficient investigations on SERS-based detection of biomolecules (e.g., DNA and protein), there has been relatively scanty information regarding in vitro and in vivo detection. In this Article, we demonstrate a kind of SERS-active substrate, i.e., AgNPs-decorated silicon wafer (AgNPs@Si), as a high-performance in vitro sensing platform for single-cell detection of apoptotic cells. The AgNPs@Si yields highly reproducible SERS signals with an enhancement factor of ∼107. Remarkably, cellular experiments show that facile, noninvasive, label-free, and sensitive detection of apoptotic cells is readily realized using the high-performance SERS-active platform. Three kinds of apoptotic cells treated with apoptosis inducer are facilely and sensitively detected at the single-cell level, suggesting the exciting potential of AgNPs@Si for SERS-based in vitro analysis and detection.

Near-infrared (NIR) hyperthermia agents are of current interest because they hold great promise as highly efficacious tools for cancer photothermal therapy. Although various agents have been reported, a practical NIR hyperthermia agent is yet unavailable. Here, we present the first demonstration that silicon nanomaterials-based NIR hyperthermia agent, that is, gold nanoparticles-decorated silicon nanowires (AuNPs@SiNWs), is capable of high-efficiency destruction of cancer cells. AuNPs@SiNWs are found to possess strong optical absorbance in the NIR spectral window, producing sufficient heat under NIR irradiation. AuNPs@SiNWs are explored as novel NIR hyperthermia agents for photothermal ablation of tumor cells. In particular, three different cancer cells treated with AuNPs@SiNWs were completely destructed within 3 min of NIR irradiation, demonstrating the exciting potential of AuNPs@SiNWs for NIR hyperthermia agents.

The availability of well-controlled and reproducible substrates is critically important for surface-enhanced Raman spectroscopy (SERS)-based applications, but it remains a challenge at present. Herein, we report a facile strategy to prepare a new kind of SERS-active substrate, i.e., a two dimensional (2D) macroporous Ag film composed of a silver nanosheet (AgNS)-coated inverse opal film. The prepared substrate features good SERS reproducibility with a high enhancement factor (6 × 107), enabling the ultra-sensitive detection of 10 fM rhodamine 6G (R6G). Moreover, the resultant substrate can be applied in the label-free detection of DNA with a sensitivity limit as low as 5 nM. Consequently, as a high-performance SERS-active substrate, the 2D AgNS-coated inverse opal film is promising for a myriad of chemical and biochemical sensing applications.

Nanomaterial-based molecular beacons (nanoMBs) have been extensively explored due to unique merits of nanostructures, including gold nanoparticle (AuNP)-, carbon nanotube (CNT)-, and graphene-based nanoMBs. Those nanoMBs are well-studied; however, they possess relatively poor salt stability or low specificity, limiting their wide applications. Here, we present a novel kind of multicolor silicon-based nanoMBs by using AuNP-decorated silicon nanowires as high-performance quenchers. Significantly, the nanoMBs feature robust stability in high-concentration (0.1 M) salt solution and wide-ranging temperature (10–80 °C), high quenching efficiency (>90%) for various fluorophores (e.g., FAM, Cy5, and ROX), and large surfaces for simultaneous assembly of different DNA strands. We further show that silicon-based nanoMBs are highly effective for sensitive and specific multidetection of DNA targets. The unprecedented advantages of silicon-based multicolor nanoMBs would bring new opportunities for challenging bioapplications, such as allele discrimination, early cancer diagnosis, and molecular engineering, etc.Keywords: DNA; gold nanoparticles; molecular beacons; multianalysis; silicon nanowires

Fluorescent silicon quantum dots (SiQDs) are facilely prepared via one-pot microwave-assisted synthesis. The as-prepared SiQDs feature excellent aqueous dispersibility, robust photo- and pH-stability, strong fluorescence, and favorable biocompatibility. Experiments show the SiQDs are superbly suitable for long-term immunofluorescent cellular imaging. Our results provide a new and invaluable methodology for large-scale synthesis of high-quality SiQDs, which are promising for various optoelectronic and biological applications.

A nanostructured complex, silicon nanowires (SiNWs) coated with in situ grown AgNPs (SiNWs@AgNPs), is developed as a well-defined surface-enhanced Raman Scattering (SERS)-active platform for ultrasensitive DNA detection. Such SiNWs@AgNPs nanostructure possesses an extremely high SERS enhancement factor of ∼1010. We design a DNA sensor based on the nanostructure via immobilization of capture probe DNA at the surface of AgNPs, and a sandwich strategy for the detection of target DNA that brings a reporter probe labeled with a dye to the proximity of the surface, leading to high SERS signals. This silicon nanostructure-based biosensor platform can detect a remarkably low DNA concentration at ∼1 fM, which is comparable to the lowest DNA concentration ever detected via SERS. We expect this highly sensitive and robust SiNWs-based SERS platform may serve as a practical and powerful tool for biomolecular sensing and biomedical analysis.Graphical abstractResearch highlights► A new silicon nanowires (SiNWs)-based SERS-active platform is developed for ultrahigh-sensitive DNA detection. ► This SiNWs-based platform possesses an exceptionally high SERS enhancement factor (∼1010), which is developed to a high-performance DNA biosensor. ► This silicon-based biosensor can readily detect a remarkably low DNA concentration at 1 fM, which is the lowest DNA concentration ever detected via SERS.

Fluorescent Ⅱ–Ⅳ Quantum dots (QDs) have demonstrated to be highly promising biological probes for various biological and biomedical applications due to their many attractive merits, such as robust photostabilty, strong photoluminescence, and size-tunable fluorescence. Along with wide ranging bioapplications, concerns about their biosafety have attracted increasingly intensive attentions. In comparison to full investigation of in vitro toxicity, there has been only scanty information regarding in vivo toxicity of the QDs. Particularly, while in vivo toxicity of organic synthesized QDs (orQDs) have been investigated recently, there exist no comprehensive studies concerning in vivo behavior of aqueous synthesized QDs (aqQDs) up to present. Herein, we investigate short- and long-term in vivo biodistribution, pharmacokinetics, and toxicity of the aqQDs. Particularly, the aqQDs are initially accumulated in liver after short-time (0.5–4 h) post-injection, and then are increasingly absorbed by kidney during long-time (15–80 days) blood circulation. Moreover, obviously size-dependent biodistribution is observed: aqQDs with larger sizes are more quickly accumulated in the spleen. Furthermore, histological and biochemical analysis, and body weight measurement demonstrate that there is no overt toxicity of aqQDs in mice even at long-time exposure time. Our studies provide invaluable information for the design and development of aqQDs for biological and biomedical applications.

There has been rapidly increasing interest in design and synthesis of silicon-based nanostructured materials for bioapplications. In this review, we focus on recent research progress in design, synthesis and bioapplications of two silicon-based nanostructures, zero-dimensional silicon quantum dots and one-dimensional silicon nanowires. These two low-dimensional silicon nanomaterials have found important applications in ultrasensitive biomolecular detection and fluorescent cellular imaging. We further highlight major challenges and promises in this area.

The NF-κB pathway plays crucial roles in inflammatory responses and cell survival. Aberrant constitutive NF-κB activation is associated with various human diseases including cancer and inflammatory and auto-immune diseases. Consequently, it is highly desirable to develop new kinds of inhibitors, which are highly efficacious for blocking the NF-κB pathway. In this study, by using a typical kind of aqueous synthesized quantum dots (QDs), i.e., CdTe QDs, as a model, we for the first time demonstrated that the QDs could selectively affect the cellular nuclear factor-κB (NF-κB) signaling pathway, but do not affect the AKT or ERK pathways. Typically, the QDs efficiently inhibited the activation of IKKα and IKKβ, resulting in the suppression of both the canonical and the non-canonical NF-κB signaling pathways. Inhibition of NF-κB by QDs downregulates anti-apoptotic genes and promotes apoptosis in cancer cells. The QDs induced NF-κB inhibition and cytotoxicity could be blocked by N-acetylcysteine due to the reduced cellular uptake of QDs. Importantly, inhibition of NF-κB by QDs displayed promising effects against the viral replication and in vivo bacterial endotoxin-induced inflammatory responses. These data suggest the QDs as potent inhibitors of the NF-κB signaling pathway, both in vitro and in vivo. Our findings highlight the potential of using QDs in the development of anti-cancer, anti-viral, and anti-inflammatory approaches, and also facilitate better understanding of QDs-related cellular behavior under the molecular level.

•A type of plasmonic Ag@Si chips composing of Si supported Ag film was fabricated.•The chips show viable integration into fluorescent immunoassays for enhancement.•The chips show up to 57 times enhancement at 800 nm in fluorescence protein assay.•The chips show up to 4.1 times fluorescence enhancement for cell and tissue imaging.Metal-enhanced fluorescence shows great potential for improving the sensitivity of fluoroscopy, which has been widely used in protein and nucleic acid detection for biosensor and bioassay applications. In comparison with the traditional glass-supported metal nanoparticles (MNPs), the introduction of a silicon substrate has been shown to provide an increased surface-enhanced Raman scattering (SERS) effect due to the coupling between the MNPs and the semiconducting silicon substrate. In this work, we further study the fluorescence-enhanced effect of the silicon-supported silver-island (Ag@Si) plasmonic chips. In particular, we investigate their practical application of improving the traditional immunoassay such as the biotin-streptavidin-based protein assay and the protein-/nucleic acid-labeled cell and tissue samples. The protein assay shows a wavelength-dependent enhancement effect of the Ag@Si chip, with an enhancement factor ranging from 1.2 (at 532 nm) to 57.3 (at 800 nm). Moreover, for the protein- and nucleic acid-labeled cell and tissue samples, the Ag@Si chip provides a fluorescence enhancement factor of 3.0–4.1 (at 800 nm) and a significant improvement in the signal/background ratio for the microscopy images. Such a ready accommodation of the fluorescence-enhanced effect for the immunoassay samples with simple manipulations indicates broad potential for applications of the Ag@Si chip not only in biological studies but also in the clinical field.

We herein report a kind of one-dimensional biocompatible fluorescent silicon nanorods (SiNRs) with tunable lengths ranging ∼100–250 nm, which can be facilely prepared through one-pot microwave synthesis. In addition to the strong fluorescence (quantum yield value: ∼15%) and negligible toxicity, the resultant SiNRs exhibit excitation wavelength-dependent photoluminescence whose maximum emission wavelength ranges from ∼450 to ∼600 nm under serial excitation wavelengths from 390 to 560 nm, providing feasibility for multicolor biological imaging. More significantly, the SiNRs are ultrahighly photostable, preserving strong and nearly unchanged fluorescence under 400 min high-power UV irradiation, which is in sharp contrast to severe fluorescence quenching of organic dyes (e.g., FITC) or II–VI quantum dots (QDs) (e.g., CdTe QDs and CdSe/ZnS QDs) within 15 or 160 min UV treatment under the same experiment conditions, respectively. Taking advantage of these attractive merits, we further exploit the SiNRs as a novel type of color converters for the construction of white light-emitting diodes (LED), which is the first proof-of-concept demonstration of LED device fabricated using the one-dimensional fluorescent silicon nanostructures.

Herein, we demonstrate that at room temperature (20–25 °C) and under atmospheric pressure, small-sized (∼3.1 nm) SiNPs can be rapidly formed in aqueous phase within 60 min, with high photoluminescence quantum yield (PLQY) of ∼50%. This approach is readily scalable and could potentially be used to produce high-quality SiNPs at an industrial level.

We herein present the first example of one-dimensional silicon nanostructures (i.e., silicon nanoshuttles (SiNSs)), which simultaneously feature bright fluorescence, robust photostability, and distinct paramagnetism. This type of SiNSs, prepared through one-pot microwave chemical synthesis in a rapid and facile manner, hold high promise for various optical and magnetic applications.

By using gramineae plants as natural and accessible reaction precursors, we herein introduce a green synthetic strategy, which is efficacious for the facile production of crystalline, excitation-wavelength-dependent fluorescent and small-sized silicon nanoparticles (SiNPs). We further explore the prepared SiNPs as a novel kind of fluorescent label for anti-counterfeiting applications.

In this article, we present a kind of silicon-based antibacterial material made of silver nanoparticle (AgNP)-decorated silicon wafers (AgNP@Si), which is facilely and rapidly (30 min) synthesized via a one-step reaction. Significantly, such a resultant silicon-based antibacterial material features stable and high antibacterial activity, preserving >99% antibacterial efficiency against E. coli during 30 day storage.

The availability of well-controlled and reproducible substrates is critically important for surface-enhanced Raman spectroscopy (SERS)-based applications, but it remains a challenge at present. Herein, we report a facile strategy to prepare a new kind of SERS-active substrate, i.e., a two dimensional (2D) macroporous Ag film composed of a silver nanosheet (AgNS)-coated inverse opal film. The prepared substrate features good SERS reproducibility with a high enhancement factor (6 × 107), enabling the ultra-sensitive detection of 10 fM rhodamine 6G (R6G). Moreover, the resultant substrate can be applied in the label-free detection of DNA with a sensitivity limit as low as 5 nM. Consequently, as a high-performance SERS-active substrate, the 2D AgNS-coated inverse opal film is promising for a myriad of chemical and biochemical sensing applications.

The first example of silicon nanowire (SiNW)-based in vivo tumor phototherapy is presented. Gold nanoparticle (AuNP)-decorated SiNWs are employed as high-performance NIR hyperthermia agents for highly efficacious in vivo tumour ablation. Significantly, the overall survival time of SiNW-treated mice is drastically prolonged, with 100% of mice being alive and tumor-free for over 8 months, which is the longest survival time ever reported for tumor-bearing mice treated with nanomaterial-based NIR hyperthermia agents.