Silicon Nanomaterials for Biosensing and Bioimaging Analysis

Examine the impact of green-synthesized nanomaterials on the germination rates and seedling characteristics of African Marigold (Tagetes erecta L. var. Pusa Narangi Ganda and Pusa Basanti Ganda)

Background

West Bengal is key to India's flower industry, contributing 10.61 % of total production, with marigolds valued at 63.44 thousand tonnes. To achieve good yields, many farmers heavily use chemical fertilizers and insecticides. Marigold seeds typically germinate in about 14 days, but farmers often face issues with uneven germination and poor seedling quality.

Materials and methods

This study was conducted at ICAR-AICRP on Floriculture and Landscape Architecture, HRS, Mandouri, Bidhan Chandra Krishi Vishwavidyalaya, West Bengal, India. We synthesized nanoparticles from Tulsi, Doob grass, and Hibiscus extracts in the lab and analyzed them using XRD, SEM, FTIR, and DLS-Zeta methods. We prepared different concentrations of TiO2 NP, SiO2 NP, and AgNPs to test their effects on two marigold varieties: Pusa Basanti Ganda and Pusa Narangi Ganda.

Findings

Recent trial results showed that treatments T4 and T5 achieved the highest germination percentages, between 90.33 % and 96.67 %, due to increased titanium dioxide nanoparticles (TiO2 NP). The Vigor Index (VI) was lowest in T10 with silver nanoparticles at 521.67, compared to 609.33 for the control group (T0) in Pusa Basanti Ganda. Seeds treated with silver NPs had longer germination times of 4.5-6.4 days, while silica nanoparticles (SiO2 NP) had mean germination times ranging from 4.6 to 5.2 days. The root/shoot ratio positively correlated with shoot dry weight (0.501 at p = 0.05). In Pusa Basanti Ganda, final germination percentage correlated positively with the Germination Rate Index (GRI), Mean Germination Rate (MGR), and Coefficient of Variation (COV) at values of 0.866, 0.756, and 0.743 respectively, all significant at p = 0.01.

Conclusion

The experiment showed that titanium dioxide (TiO2) nanoparticles at high concentrations enhance seed germination, while silver nanoparticles (AgNPs) hinder it. Silicon dioxide (SiO2) NPs at moderate concentrations support seedling growth. Tested salts at specific concentrations can be recommended to farmers for better crop production.

Solid-state synthesis of Si1-xGex nanoalloys with composition-tunable energy gaps and visible to near infrared optical properties

Si1-xGex alloy nanocrystals (NCs) are a class of benign semiconductors that show size and composition-tunable energy gaps and promising optical properties because of the lattice disorder. The random distribution of elements within the alloys can lead to efficient light-matter interactions, making them attractive for Si-compatible optoelectronic devices, transistors, charge storage, and memory applications. However, the fabrication of discrete, quantum-confined alloys has proved a challenging task. Herein, we report solid-state co-disproportionation of a hydrogen silsesquioxane (HSQ)/GeI2 composite precursor to produce homogeneous Si1-xGex NCs with control over the diameter (5.9 ± 0.7-7.8 ± 1.1 nm) and composition (x = 0-14.4%) with strong size confinement effects and visible to near IR absorption and emission properties. As-synthesized alloys show an expanded diamond cubic Si structure, a systematic red-shift of Si-Si Raman peak, and emergence of Si-Ge/Ge-Ge peaks with increasing Ge, consistent with the admixture of isovalent elements. Surface analysis of alloys reveals Si0/Ge0 core and Sin+/Gen+ surface species and efficient surface functionalization with alkyl ligands via thermal hydrosilylation and/or hydrogermylation. Alloy NCs exhibit absorption onsets (2.26-1.92 eV), indirect (1.53-1.80 eV) and direct (2.88-2.47 eV) energy gaps, and photoluminescence (PL) maxima (1.40-1.27 eV) that can be tuned by manipulating the diameter and/or composition. The experimental PL energies are consistent with those predicted by density functional theory (DFT), suggesting that the PL originates from NC core electronic transitions. The facile low-temperature solid-state synthesis and control over physical properties realized in this study will allow discrete Si1-xGex NCs to emerge as low to nontoxic, earth-abundant, and Si-compatible nanostructures for a broad range of electronic and photonic technologies.

Advancements in nanomaterials for nanosensors: a comprehensive review

Nanomaterials (NMs) exhibit unique properties that render them highly suitable for developing sensitive and selective nanosensors across various domains. This review aims to provide a comprehensive overview of nanomaterial-based nanosensors, highlighting their applications and the classification of frequently employed NMs to enhance sensitivity and selectivity. The review introduces various classifications of NMs commonly used in nanosensors, such as carbon-based NMs, metal-based NMs, and others, elucidating their exceptional properties, including high thermal and electrical conductivity, large surface area-to-volume ratio and good biocompatibility. A thorough examination of literature sources was conducted to gather information on NMs-based nanosensors' characteristics, properties, and fabrication methods and their application in diverse sectors such as healthcare, environmental monitoring, industrial processes, and security. Additionally, advanced applications incorporating machine learning techniques were analyzed to enhance the sensor's performance. This review advances the understanding and development of nanosensor technologies by providing insights into fabrication techniques, characterization methods, applications, and future outlook. Key challenges such as robustness, biocompatibility, and scalable manufacturing are also discussed, offering avenues for future research and development in this field.

New insights into targeted therapy of glioblastoma using smart nanoparticles

In recent times, the intersection of nanotechnology and biomedical research has given rise to nanobiomedicine, a captivating realm that holds immense promise for revolutionizing diagnostic and therapeutic approaches in the field of cancer. This innovative fusion of biology, medicine, and nanotechnology aims to create diagnostic and therapeutic agents with enhanced safety and efficacy, particularly in the realm of theranostics for various malignancies. Diverse inorganic, organic, and hybrid organic-inorganic nanoparticles, each possessing unique properties, have been introduced into this domain. This review seeks to highlight the latest strides in targeted glioblastoma therapy by focusing on the application of inorganic smart nanoparticles. Beyond exploring the general role of nanotechnology in medical applications, this review delves into groundbreaking strategies for glioblastoma treatment, showcasing the potential of smart nanoparticles through in vitro studies, in vivo investigations, and ongoing clinical trials.

A mitochondria-targeted ratiometric fluorescent sensor based on naphthalimide derivative-functionalized silica-based nanodots for imaging formaldehyde in living cells and zebrafish

A mitochondria-targeted ratiometric fluorescent sensor (Mito-Si-NA) for formaldehyde (FA) has been constructed by functionalizing silica-based nanodots (silica-based ND). As the fluorescence reference and carrier, the silica-based ND conjugate with small molecule probe for FA via covalent. Further modifying with mitochondria targeting moiety enables the sensor to specifically target mitochondria. In the presence of FA, the emission of silica-based ND remain constant to act as an internal reference (445 nm) while the response signal of small molecule probe was gradually enhanced (545 nm). This sensor exhibits excellent selectivity towards FA with great changes of fluorescence intensity ratio values (I545/I445). The FA ratiometric fluorescence imaging in mitochondria was achieved successfully. In addition, the sensor was also successfully used for imaging FA in zebrafish. The good performance of Mito-Si-NA for FA bioimaging confirms that Mito-Si-NA is an appealing imaging tool to monitor FA in mitochondria and shows great potential to study the functions of FA on mitochondria.

Silica nanoparticles in medicine: overcoming pathologies through advanced drug delivery, diagnostics, and therapeutic strategies

Over the last decades, silica nanoparticles (SiNPs) have been studied for their applications in biomedicine as an alternative used for conventional diagnostics and treatments. Since their properties can be modified and adjusted for the desired use, they have many different potential applications in medicine: they can be used in diagnosis because of their ability to be loaded with dyes and their increased selectivity and sensitivity, which can improve the quality of the diagnostic process. SiNPs can be functionalized by targeting ligands or molecules to detect certain cellular processes or biomarkers with better precision. Targeted delivery is another fundamental use of SiNPs. They could be used as drug delivery systems (DDS) since their structure allows the loading of therapeutic agents or other compounds, and studies have demonstrated their biocompatibility. When SiNPs are used as DDS, the drug's toxicity and the off-target effects are reduced significantly, and they can be used to treat conditions like cancer and neurological diseases and even aid in regenerative processes, such as wound healing or bone repair. However, safety concerns must be considered before SiNPs can be used extensively in clinical practice because NPs can cause toxicity in certain conditions and accumulate at undesired locations. Therefore, an overview of the potential applications that SiNPs could have in medicine, as well as their safety concerns, will be covered in this review paper.

Visualization Materials Using Silicon-Based Optical Nanodisks (ViSiON) for Enhanced NIR Imaging in Ophthalmology

ViSiON (visualization materials composed of silicon-based optical nanodisks) is presented, which offers a unique optical combination of near-infrared (NIR) optical properties and biodegradability. Initially, numerical simulations are conducted to calculate the total extinction and scattering effects of ViSiON by the diameter-to-thickness ratio, predicting precise control over its scattering properties in the NIR region. A top-down patterning technique is employed to synthesize ViSiON with accurate diameter and thickness control. ViSiON with a 50 nm thickness exhibits scattering properties over 400 times higher than that of 30 nm, rendering it suitable as a contrast agent for optical coherence tomography (OCT), especially in ophthalmic applications. Furthermore, ViSiON possesses inherent biodegradability in media, with ≈95% degradation occurring after 48 h, and the degradation rate can be finely tuned based on the quantity of protein coating applied to the surface. Subsequently, the OCT imaging capability is validated even within vessels smaller than 300 µm, simulating retinal vasculature using a retinal phantom. Then, using an ex ovo chick embryo model, it is demonstrated that ViSiON enhances the strength of protein membranes by 6.17 times, thereby presenting the potential for ViSiON as an OCT imaging probe capable of diagnosing retinal diseases.

Silicon nanoparticles in sustainable agriculture: synthesis, absorption, and plant stress alleviation

Silicon (Si) is a widely recognized beneficial element in plants. With the emergence of nanotechnology in agriculture, silicon nanoparticles (SiNPs) demonstrate promising applicability in sustainable agriculture. Particularly, the application of SiNPs has proven to be a high-efficiency and cost-effective strategy for protecting plant against various biotic and abiotic stresses such as insect pests, pathogen diseases, metal stress, drought stress, and salt stress. To date, rapid progress has been made in unveiling the multiple functions and related mechanisms of SiNPs in promoting the sustainability of agricultural production in the recent decade, while a comprehensive summary is still lacking. Here, the review provides an up-to-date overview of the synthesis, uptake and translocation, and application of SiNPs in alleviating stresses aiming for the reasonable usage of SiNPs in nano-enabled agriculture. The major points are listed as following: (1) SiNPs can be synthesized by using physical, chemical, and biological (green synthesis) approaches, while green synthesis using agricultural wastes as raw materials is more suitable for large-scale production and recycling agriculture. (2) The uptake and translocation of SiNPs in plants differs significantly from that of Si, which is determined by plant factors and the properties of SiNPs. (3) Under stressful conditions, SiNPs can regulate plant stress acclimation at morphological, physiological, and molecular levels as growth stimulator; as well as deliver pesticides and plant growth regulating chemicals as nanocarrier, thereby enhancing plant growth and yield. (4) Several key issues deserve further investigation including effective approaches of SiNPs synthesis and modification, molecular basis of SiNPs-induced plant stress resistance, and systematic effects of SiNPs on agricultural ecosystem.

Silicon-containing nanomedicine and biomaterials: materials chemistry, multi-dimensional design, and biomedical application

The invention of silica-based bioactive glass in the late 1960s has sparked significant interest in exploring a wide range of silicon-containing biomaterials from the macroscale to the nanoscale. Over the past few decades, these biomaterials have been extensively explored for their potential in diverse biomedical applications, considering their remarkable bioactivity, excellent biocompatibility, facile surface functionalization, controllable synthesis, etc. However, to expedite the clinical translation and the unexpected utilization of silicon-composed nanomedicine and biomaterials, it is highly desirable to achieve a thorough comprehension of their characteristics and biological effects from an overall perspective. In this review, we provide a comprehensive discussion on the state-of-the-art progress of silicon-composed biomaterials, including their classification, characteristics, fabrication methods, and versatile biomedical applications. Additionally, we highlight the multi-dimensional design of both pure and hybrid silicon-composed nanomedicine and biomaterials and their intrinsic biological effects and interactions with biological systems. Their extensive biomedical applications span from drug delivery and bioimaging to therapeutic interventions and regenerative medicine, showcasing the significance of their rational design and fabrication to meet specific requirements and optimize their theranostic performance. Additionally, we offer insights into the future prospects and potential challenges regarding silicon-composed nanomedicine and biomaterials. By shedding light on these exciting research advances, we aspire to foster further progress in the biomedical field and drive the development of innovative silicon-composed nanomedicine and biomaterials with transformative applications in biomedicine.

Fluorescent silica nanoparticles as nano-chemosensors for the sequential detection of Pb2+ ions and bacterial-spore biomarker dipicolinic acid (DPA) in aqueous solution

Herein, we report fluorescein-labelled silica nanoparticles (FSNP) which serve as fluorescent nano-chemosensors for sequential detection of Pb2+ (which is a toxic heavy metal) and dipicolinic acid (DPA) (which is a distinctive indicator biomarker of bacterial spores) with high sensitivity and selectivity. The fluorescence of FSNP is quenched because of the complex formation between Pb2+ ions and surface amide groups, however, the fluorescence is recovered in contact with DPA, resulting from the association of DPA with surface bound Pb2+ ions. FSNP-Pb2+ complexes show high sensitivity towards DPA with a low detection limit of 850 nM which is approximately seventy times lower than the infectious dosage of bacterial spores (60 μM). Lateral flow test platform was further developed to show the applicability and practicability of our system.

Functional fluorescent nanomaterials for the detection, diagnosis and control of bacterial infection and biofilm formation: Insight towards mechanistic aspects and advanced applications

Infectious diseases resulting from the high pathogenic potential of several bacteria possesses a major threat to human health and safety. Traditional methods used for screening of these microorganisms face major issues with respect to detection time, selectivity and specificity which may delay treatment for critically ill patients past the optimal time. Thus, a convincing and essential need exists to upgrade the existing methodologies for the fast detection of bacteria. In this context, increasing number of newly emerging nanomaterials (NMs) have been discovered for their effective use and applications in the area of diagnosis in bacterial infections. Recently, functional fluorescent nanomaterials (FNMs) are extensively explored in the field of biomedical research, particularly in developing new diagnostic tools, nanosensors, specific imaging modalities and targeted drug delivery systems for bacterial infection. It is interesting to note that organic fluorophores and fluorescent proteins have played vital role for imaging and sensing technologies for long, however, off lately fluorescent nanomaterials are increasingly replacing these due to the latter's unprecedented fluorescence brightness, stability in the biological environment, high quantum yield along with high sensitivity due to enhanced surface property etc. Again, taking advantage of their photo-excitation property, these can also be used for either photothermal and photodynamic therapy to eradicate bacterial infection and biofilm formation. Here, in this review, we have paid particular attention on summarizing literature reports on FNMs which includes studies detailing fluorescence-based bacterial detection methodologies, antibacterial and antibiofilm applications of the same. It is expected that the present review will attract the attention of the researchers working in this field to develop new engineered FNMs for the comprehensive diagnosis and treatment of bacterial infection and biofilm formation.

Delivery of miR-200c-3p Using Tumor-Targeted Mesoporous Silica Nanoparticles for Breast Cancer Therapy

Despite advances in breast cancer treatment, it remains the leading cause of cancer-related death in women worldwide. In this context, microRNAs have emerged as potential therapeutic targets but still present some limitations for in vivo applications. Particularly, miR-200c-3p is a well-known tumor suppressor microRNA that inhibits tumor progression and metastasis in breast cancer through downregulating ZEB1 and ZEB2. Based on the above, we describe the design and validation of a nanodevice using mesoporous silica nanoparticles for miR-200c-3p delivery for breast cancer treatment. We demonstrate the biocompatibility of the synthesized nanodevices as well as their ability to escape from endosomes/lysosomes and inhibit tumorigenesis, invasion, migration, and proliferation of tumor cells in vitro. Moreover, tumor targeting and effective delivery of miR-200c-3p from the nanoparticles in vivo are confirmed in an orthotopic breast cancer mouse model, and the therapeutic efficacy is also evidenced by a decrease in tumor size and lung metastasis, while showing no signs of toxicity. Overall, our results provide evidence that miR-200c-3p-loaded nanoparticles are a potential strategy for breast cancer therapy and a safe and effective system for tumor-targeted delivery of microRNAs.

Silicon Nanoparticle-Based Ratiometric Fluorescence Probes for Highly Sensitive and Visual Detection of VB2

In this work, blue fluorescent silicon nanoparticles (SiNPs) were prepared by a simple one-step hydrothermal method using (3-aminopropyl) triethoxy silane (APTES) and eriochrome black T as raw materials. The SiNPs showed favorable water solubility, thermal stability, pH stability, salt tolerance, and photobleaching resistance. At an excitation wavelength of 376 nm, the SiNPs emitted bright blue fluorescence at 460 nm. In the presence of vitamin B₂ (VB₂), the fluorescence intensity (FL intensity) of the SiNPs at 460 nm decreased obviously, and a new peak appeared at 521 nm. Based on this, a novel ratiometric fluorescence method was established for VB₂ detection. There was a good linear relationship between the fluorescence intensity ratio (F ₅₂₁/F ₄₆₀) and VB₂ concentration from 0.5 to 60 μM with a detection limit of 135 nM. This method was successfully applied to detect VB₂ content in the samples of vitamin B₂ drugs and beverages. Additionally, a simple paper sensor based on the SiNPs was designed to visualize detection of VB₂. With the support of color recognition software on a smartphone, the visual quantitative analysis of VB₂ was realized, ranging from 40 to 800 μM.

1D and 2D Field Effect Transistors in Gas Sensing: A Comprehensive Review

Rapid progress in the synthesis and fundamental understanding of 1D and 2D materials have solicited the incorporation of these nanomaterials into sensor architectures, especially field effect transistors (FETs), for the monitoring of gas and vapor in environmental, food quality, and healthcare applications. Yet, several challenges have remained unaddressed toward the fabrication of 1D and 2D FET gas sensors for real-field applications, which are related to properties, synthesis, and integration of 1D and 2D materials into the transistor architecture. This review paper encompasses the whole assortment of 1D-i.e., metal oxide semiconductors (MOXs), silicon nanowires (SiNWs), carbon nanotubes (CNTs)-and 2D-i.e., graphene, transition metal dichalcogenides (TMD), phosphorene-materials used in FET gas sensors, critically dissecting how the material synthesis, surface functionalization, and transistor fabrication impact on electrical versus sensing properties of these devices. Eventually, pros and cons of 1D and 2D FETs for gas and vapor sensing applications are discussed, pointing out weakness and highlighting future directions.

Facile synthesis of non-modified yellow emission silicon quantum dots and their visualization of hydrogen sulfide in living cells and onion tissues

Yellow fluorescent silicon quantum dots (y-SiQDs) with 22.2% fluorescence quantum yield were synthesized by a simple hydrothermal method using 3-glycidoxypropyl triethoxysilane (GOTS) and m-aminophenol. The excitation wavelength is 550 nm with an emission wavelength of 574 nm, which effectively avoids the interference of biological autofluorescence. Notably, the synthesis approach does not require any post-modification and the y-SiQDs can be directly used for hydrogen sulfide (H₂S) quantification due to static quenching. It exhibits high sensitivity and excellent selectivity for H₂S with a 0.2-10 μM (R² = 0.9953) linear range and detection limit of 54 nM. y-SiQDs have excellent stability and biocompatibility and can be used for H₂S imaging in living cells and onion tissues.

Nanoparticles as a Promising Strategy to Mitigate Biotic Stress in Agriculture

Nanoparticles are recognized due to their particular physical and chemical properties, which are conferred due to their size, in the range of nanometers. Nanoparticles are recognized for their application in medicine, electronics, and the textile industry, among others, but also in agriculture. The application of nanoparticles as nanofertilizers and biostimulants can help improve growth and crop productivity, and it has therefore been mentioned as an essential tool to control the adverse effects of abiotic stress. However, nanoparticles have also been noted for their exceptional antimicrobial properties. Therefore, this work reviews the state of the art of different nanoparticles that have shown the capacity to control biotic stress in plants. In this regard, metal and metal oxide nanoparticles, polymeric nanoparticles, and others, such as silica nanoparticles, have been described. Moreover, uptake and translocation are covered. Finally, future remarks about the studies on nanoparticles and their beneficial role in biotic stress management are made.

Hybrid Nanobioengineered Nanomaterial-Based Electrochemical Biosensors

Nanoengineering biosensors have become more precise and sophisticated, raising the demand for highly sensitive architectures to monitor target analytes at extremely low concentrations often required, for example, for biomedical applications. We review recent advances in functional nanomaterials, mainly based on novel organic-inorganic hybrids with enhanced electro-physicochemical properties toward fulfilling this need. In this context, this review classifies some recently engineered organic-inorganic metallic-, silicon-, carbonaceous-, and polymeric-nanomaterials and describes their structural properties and features when incorporated into biosensing systems. It further shows the latest advances in ultrasensitive electrochemical biosensors engineered from such innovative nanomaterials highlighting their advantages concerning the concomitant constituents acting alone, fulfilling the gap from other reviews in the literature. Finally, it mentioned the limitations and opportunities of hybrid nanomaterials from the point of view of current nanotechnology and future considerations for advancing their use in enhanced electrochemical platforms.

Synthesis of metal ion-tolerant Mn-doped fluorescence silicon quantum dots with green emission and its application for selective imaging of ·OH in living cells

Monitoring hydroxyl radical (·OH) in living cells remains a big challenge on account of its high reactivity and short half-life. In this work, we designed a fluorescent probe based on manganese-doped silicon quantum dots (Mn-SiQDs) for detecting and imaging of ·OH with good water solubility. The manganese was doped in its ethylene diamine tetra-acetic acid (EDTA) complex form and effectively improved the metal ion tolerance of fluorescence of SiQDs. And m-dihydroxybenzene was used as the reductant to extend the emission of SiQDs to the green region at 515 nm when the excitation wavelength was 424 nm. Basing on the fluorescence quenching of Mn-SiQDs, a linear response of ·OH was observed in the range 0.8-50 μM with a limit of detection (LOD) of 88.4 nM, which is lower than those reported with SiQDs. The interference from other ROS or RNS has been assessed and no impact was found. In fully aqueous systems, the Mn-SiQDs have been applied to monitor and image the endogenous ·OH in HeLa cells. Our work provided a new strategy for designing SiQDs with good biocompatibility, high selectivity and long monitoring wavelength. Synthesis of green-emitting silicon quantum dots with N-[3 -(trimethoxysilyl) propyl] ethylenediamine (DAMO), Ethylenediamine tetraacetic acid disodium salt dehydrate (EDTA-2Na·2H₂O), manganese acetate tetrahydrate (Mn(CH₃COO)₂·4H₂0) and m-dihydroxybenzene. The green fluorescence of the silicon quantum dots can be selectively quenched by hydroxyl radicals.

Nano optical and electrochemical sensors and biosensors for detection of narrow therapeutic index drugs

For the first time, a comprehensive review is presented on the quantitative determination of narrow therapeutic index drugs (NTIDs) by nano optical and electrochemical sensors and biosensors. NTIDs have a narrow index between their effective doses and those at which they produce adverse toxic effects. Therefore, accurate determination of these drugs is very important for clinicians to provide a clear judgment about drug therapy for patients. Routine analytical techniques have limitations such as being expensive, laborious, and time-consuming, and need a skilled user and therefore  the nano/(bio)sensing technology leads to high interest.

Technological advances in electrochemical biosensors for the detection of disease biomarkers

With an increasing focus on health in contemporary society, interest in the diagnosis, treatment, and prevention of diseases has grown rapidly. Accordingly, the demand for biosensors for the early diagnosis of disease is increasing. However, the measurement range of existing electrochemical sensors is relatively high, which is not suitable for early disease diagnosis, requiring the detection of small amounts of biocomponents. Various attempts have been made to overcome this and amplify the signal, including binding with various labeling molecules, such as DNA, enzymes, nanoparticles, and carbon materials. Efforts are also being made to increase the sensitivity of electrochemical sensors, and the combination of nanomaterials, materials, and biotechnology offers the potential to increase sensitivity in a variety of ways. Recent studies suggest that electrochemical sensors can be a powerful tool in providing comprehensive insights into the targeting and detection of disease-associated biomarkers. Significant advances in nanomaterial and biomolecule approaches for improved sensitivity have resulted in the development of electrochemical biosensors capable of detecting multiple biomarkers in real time in clinically relevant samples. In this review, we have discussed the recent studies on electrochemical sensors for detection of diseases such as diabetes, degenerative diseases, and cancer. Further, we have highlighted new technologies to improve sensitivity using various materials, including DNA, enzymes, nanoparticles, and carbon materials.

"Turning the dials": controlling synthesis, structure, composition, and surface chemistry to tailor silicon nanoparticle properties

Silicon nanoparticles (SiNPs) can be challenging to prepare with defined size, crystallinity, composition, and surface chemistry. As is the case for any nanomaterial, controlling these parameters is essential if SiNPs are to realize their full potential in areas such as alternative energy generation and storage, sensors, and medical imaging. Numerous teams have explored and established innovative synthesis methods, as well as surface functionalization protocols to control these factors. Furthermore, substantial effort has been expended to understand how the abovementioned parameters influence material properties. In the present review we provide a commentary highlighting the benefits and limitations of available methods for preparing silicon nanoparticles as well as demonstrations of tailoring optical and electronic properties through definition of structure (i.e., crystalline vs. amorphous), composition and surface chemistry. Finally, we highlight potential opportunities for future SiNP studies.

Nanomaterials in the Management of Gram-Negative Bacterial Infections

The exploration of multiplexed bacterial virulence factors is a major problem in the early stages of Escherichia coli infection therapy. Traditional methods for detecting Escherichia coli (E. coli), such as serological experiments, immunoassays, polymerase chain reaction, and isothermal microcalorimetry have some drawbacks. As a result, detecting E. coli in a timely, cost-effective, and sensitive manner is critical for various areas of human safety and health. Intelligent devices based on nanotechnology are paving the way for fast and early detection of E. coli at the point of care. Due to their specific optical, magnetic, and electrical capabilities, nanostructures can play an important role in bacterial sensors. Another one of the applications involved use of nanomaterials in fighting microbial infections, including E. coli mediated infections. Various types of nanomaterials, either used directly as an antibacterial agent such as metallic nanoparticles (NPs) (silver, gold, zinc, etc.), or as a nanocarrier to deliver and target the antibiotic to the E. coli and its infected area. Among different types, polymeric NPs, lipidic nanocarriers, metallic nanocarriers, nanomicelles, nanoemulsion/ nanosuspension, dendrimers, graphene, etc. proved to be effective vehicles to deliver the drug in a controlled fashion at the targeted site with lower off-site drug leakage and side effects.

Highly Sensitive Fluorescent pH Microsensors Based on the Ratiometric Dye Pyranine Immobilized on Silica Microparticles

Pyranine (HPTS) is a remarkably interesting pH-sensitive dye that has been used for plenty of applications. Its high quantum yield and extremely sensitive ratiometric fluorescence against pH change makes it a very favorable for pH-sensing applications and the development of pH nano-/microsensors. However, its strong negative charge and lack of easily modifiable functional groups makes it difficult to use with charged substrates such as silica. This study reports a methodology for noncovalent HPTS immobilization on silica microparticles that considers the retention of pH sensitivity as well as the long-term stability of the pH microsensors. The study emphasizes the importance of surface charge for governing the sensitivity of the immobilized HPTS dye molecules on silica microparticles. The importance of the immobilization methodology, which preserves the sensitivity and stability of the microsensors, is also assessed.

COOH-Terminated Silicon Quantum Dots as a Highly Efficient Drug Nanocarrier for Targeted Tumor Cell Imaging

Fluorescent silicon quantum dots (SiQDs) characterized by exceptional photostability and colloidal robustness as well as beneficial biocompatibility are fast becoming new pharmaceutical nanocarriers. With a view to efficiently loading cisplatin (CDDP) onto SiQDs, carboxylate group (COOH) terminated SiQDs were imperative because of chelate formation with CDDP. In this work, we employed a facial microwave irradiation route for rapidly synthesizing high-quality COOH-SiQDs through the use of 3-aminopropyl trimethoxy silane (APTMS) molecules to fulfil the role of silicon precursor and maleic acid (MA) as the agent for facilitating reduction. The SiQDs showed blue fluorescence with an associated photoluminescence quantum yield (PLQY) of 40.2%, the size of which was small at 3.2 ±0.6 nm, and long-lasting stability (an extensive range in pH (4-12) and concentrations of electrolytes reaching 3 Molarity of a solution of sodium chloride). As nanocarriers, carboxylic acids chelation generated a high loading of CDDP onto SiQDs (drug loading capacity, DLC up to 32.2% at pH = 9) and a drug release of CDDP up to 57.6% at pH = 5. Furthermore, the MTT assays demonstrated the non or low cytotoxicity of SiQDs and the role of the controlled release of SiQD-CDDP Finally, the prepared SiQD-CDDP were used for cell imaging, and further targeted labeling of some tumors after folic acid (FA) conjugation. These characteristics allow for the deployment of SiQDs as a highly efficient nanocarrier that facilitate the delivery of clinical drugs for the future.

Nanomaterial-Based Dual-Emission Ratiometric Fluorescent Sensors for Biosensing and Cell Imaging

Owing to the unique optophysical properties of nanomaterials and their self-calibration characteristics, nanomaterial-based (e.g., polymer dots (Pdots) quantum dots (QDs), silicon nanorods (SiNRs), and gold nanoparticle (AuNPs), etc.) ratiometric fluorescent sensors play an essential role in numerous biosensing and cell imaging applications. The dual-emission ratiometric fluorescence technique has the function of effective internal referencing, thereby avoiding the influence of various analyte-independent confounding factors. The sensitivity and precision of the detection can therefore be greatly improved. In this review, the recent progress in nanomaterial-based dual-emission ratiometric fluorescent biosensors is systematically summarized. First, we introduce two general design approaches for dual-emission ratiometric fluorescent sensors, involving ratiometric fluorescence with changes of one response signal and two reversible signals. Then, some recent typical examples of nanomaterial-based dual-emission ratiometric fluorescent biosensors are illustrated in detail. Finally, probable challenges and future outlooks for dual-emission ratiometric fluorescent nanosensors for biosensing and cell imaging are rationally discussed.

Photoluminescent Nanoparticles for Chemical and Biological Analysis and Imaging

Research related to the development and application of luminescent nanoparticles (LNPs) for chemical and biological analysis and imaging is flourishing. Novel materials and new applications continue to be reported after two decades of research. This review provides a comprehensive and heuristic overview of this field. It is targeted to both newcomers and experts who are interested in a critical assessment of LNP materials, their properties, strengths and weaknesses, and prospective applications. Numerous LNP materials are cataloged by fundamental descriptions of their chemical identities and physical morphology, quantitative photoluminescence (PL) properties, PL mechanisms, and surface chemistry. These materials include various semiconductor quantum dots, carbon nanotubes, graphene derivatives, carbon dots, nanodiamonds, luminescent metal nanoclusters, lanthanide-doped upconversion nanoparticles and downshifting nanoparticles, triplet-triplet annihilation nanoparticles, persistent-luminescence nanoparticles, conjugated polymer nanoparticles and semiconducting polymer dots, multi-nanoparticle assemblies, and doped and labeled nanoparticles, including but not limited to those based on polymers and silica. As an exercise in the critical assessment of LNP properties, these materials are ranked by several application-related functional criteria. Additional sections highlight recent examples of advances in chemical and biological analysis, point-of-care diagnostics, and cellular, tissue, and in vivo imaging and theranostics. These examples are drawn from the recent literature and organized by both LNP material and the particular properties that are leveraged to an advantage. Finally, a perspective on what comes next for the field is offered.

A simple fluorescence-based lateral flow test platform for rapid influenza B virus screening

A simple fluorescence-based lateral flow test platform for rapid influenza B virus screening as a model target molecule was successfully developed. In this work, Cy5-loaded silica nanoparticles were directly conjugated to monoclonal antibodies, specific to the influenza B nucleoprotein, via a direct physisorption method and used as detector probes. Using this approach, the signal response to the detection was further determined using a fluorescent signal intensity measurement method via a portable reader, in combination with fluorescence imaging analysis. The degree to which the fluorescence signal response is detected is proportional to the amount of the target virus protein present in the system, reflected by the accumulation of the formed particle-antibody conjugates within the test system. Under optimized conditions, the system is capable of detecting the influenza B virus protein at a level of 0.55 μg per test within 30 min, using small sample volumes as low as 100 μL (R² = 0.9544). In addition to its simplicity, further application of the system in detecting the influenza B virus protein was demonstrated using the viral transport media as specimen matrices. It was also shown that the system can perform the detection without cross-reactivity to other closely related respiratory viruses.

Biosensing platforms based on silicon nanostructures: A critical review

Biosensors are revolutionizing the health-care systems worldwide, permitting to survey several diseases, even at their early stage, by using different biomolecules such as proteins, DNA, and other biomarkers. However, these sensing approaches are still scarcely diffused outside the specialized medical and research facilities. Silicon is the undiscussed leader of the whole microelectronics industry, and novel sensors based on this material may completely change the health-care scenario. In this review, we will show how novel sensing platforms based on Si nanostructures may have a disruptive impact on applications with a real commercial transfer. A critical study for the main Si-based biosensors is herein presented with a comparison of their advantages and drawbacks. The most appealing sensing devices are discussed, starting from electronic transducers, with Si nanowires field-effect transistor (FET) and porous Si, to their optical alternatives, such as effective optical thickness porous silicon, photonic crystals, luminescent Si quantum dots, and finally luminescent Si NWs. All these sensors are investigated in terms of working principle, sensitivity, and selectivity with a specific focus on the possibility of their industrial transfer, and which ones may be preferred for a medical device.

Recent advances in bioelectronics chemistry

Research in bioelectronics is highly interdisciplinary, with many new developments being based on techniques from across the physical and life sciences. Advances in our understanding of the fundamental chemistry underlying the materials used in bioelectronic applications have been a crucial component of many recent discoveries. In this review, we highlight ways in which a chemistry-oriented perspective may facilitate novel and deep insights into both the fundamental scientific understanding and the design of materials, which can in turn tune the functionality and biocompatibility of bioelectronic devices. We provide an in-depth examination of several developments in the field, organized by the chemical properties of the materials. We conclude by surveying how some of the latest major topics of chemical research may be further integrated with bioelectronics.

Recent advances in bioelectronics chemistry

Research in bioelectronics is highly interdisciplinary, with many new developments being based on techniques from across the physical and life sciences. Advances in our understanding of the fundamental chemistry underlying the materials used in bioelectronic applications have been a crucial component of many recent discoveries. In this review, we highlight ways in which a chemistry-oriented perspective may facilitate novel and deep insights into both the fundamental scientific understanding and the design of materials, which can in turn tune the functionality and biocompatibility of bioelectronic devices. We provide an in-depth examination of several developments in the field, organized by the chemical properties of the materials. We conclude by surveying how some of the latest major topics of chemical research may be further integrated with bioelectronics.

The influence of the fluid nature on femtosecond laser ablation properties of a SiO2/Si target and synthesis of ultrafine-grained Si nanoparticles

Nanocrystalline silicon nanoparticles with a median crystallite size of 3-4 nm and several crystalline phases and defects (e.g. twin boundary) were produced by femtosecond laser processing of a SiO2/Si target in various organic fluids. Furthermore, a nanoscaled amorphous oxide layer and a few atomic layers of a graphite shell were detected in ethanol and 2-butanol correspondingly. The ultrafast laser pulses may manipulate nanostructures at the atomic level and generate a high density of defects; this may be correlated with significant thermal stresses on nanoparticles and rapid condensation of primary nanoparticles with high cooling rates. Size distribution width and a polydispersity index slightly increased with increasing laser fluence in ethanol. In 2-butanol, the maximum ablation volume was observed. The specific ablation rates in 2-butanol and ethanol were approximately five times higher than n-hexane. The lowest ablation efficiency in n-hexane can be associated with femtosecond laser-induced photolysis and pyrolysis of solvent molecules, as total energy deposition on the material may be reduced due to the formation of carbonaceous products. The roughened zones (average roughness of ∼400 nm) in circumferences of the ablated craters in 2-butanol may be related to a correlation between the erosive power of the vapour bubble collapse and higher pressure at the bubble wall in relatively high dynamic viscosity fluids. Furthermore, sputtering of a pristine surface by releasing nanoparticles from the collective collapse of up-flow vapour bubbles can also contribute to the generation of roughened regions.

Amine functionalised silicon nanocrystals with bright red and long-lived emission

When functionalised with amines, silicon nanocrystals (SiNCs) are known to have surface-state emission with loss of colour tunability, low quantum yield and short nanosecond lifetimes. These changes in optical properties are produced by direct amine bonding on the silicon surface. In this article, secondary amine functionalised SiNCs with bright, red (λmax = 750 nm) and long-lived emission (τ ca. 50 μs) are reported for the first time via a three-step synthetic approach. These SiNCs are colloidally stable in several polar solvents and can be further functionalised by reaction with carboxylic acid groups. We proved the feasibility of further functionalization with pyrene butyric acid: ca. 40 pyrene units per nanoparticle were attached via amide bond formation. The resulting hybrid system works as a light-harvesting antenna: excitation of pyrene units at 345 nm results in sensitised emission at 700 nm by the silicon core.

Silicon Quantum Dots: Synthesis, Encapsulation, and Application in Light-Emitting Diodes

Silicon quantum dots (SiQDs) are semiconductor Si nanoparticles ranging from 1 to 10 nm that hold great applicative potential as optoelectronic devices and fluorescent bio-marking agents due to their ability to fluoresce blue and red light. Their biocompatibility compared to conventional toxic Group II-VI and III-V metal-based quantum dots makes their practical utilization even more attractive to prevent environmental pollution and harm to living organisms. This work focuses on their possible use for light-emitting diode (LED) manufacturing. Summarizing the main achievements over the past few years concerning different Si quantum dot synthetic methods, LED formation and characteristics, and strategies for their stabilization by microencapsulation and modification of their surface by specific ligands, this work aims to provide guidance en route to the development of the first stable Si-based light-emitting diodes.

Introductory lecture: origins and applications of efficient visible photoluminescence from silicon-based nanostructures

This review highlights many spectroscopy-based studies and selected phenomenological studies of silicon-based nanostructures that provide insight into their likely PL mechanisms, and also covers six application areas.

Tumor Targeting Strategies of Smart Fluorescent Nanoparticles and Their Applications in Cancer Diagnosis and Treatment

Advantages such as strong signal strength, resistance to photobleaching, tunable fluorescence emissions, high sensitivity, and biocompatibility are the driving forces for the application of fluorescent nanoparticles (FNPs) in cancer diagnosis and therapy. In addition, the large surface area and easy modification of FNPs provide a platform for the design of multifunctional nanoparticles (MFNPs) for tumor targeting, diagnosis, and treatment. In order to obtain better targeting and therapeutic effects, it is necessary to understand the properties and targeting mechanisms of FNPs, which are the foundation and play a key role in the targeting design of nanoparticles (NPs). Widely accepted and applied targeting mechanisms such as enhanced permeability and retention (EPR) effect, active targeting, and tumor microenvironment (TME) targeting are summarized here. Additionally, a freshly discovered targeting mechanism is introduced, termed cell membrane permeability targeting (CMPT), which improves the tumor-targeting rate from less than 5% of the EPR effect to more than 50%. A new design strategy is also summarized, which is promising for future clinical targeting NPs/nanomedicines design. The targeting mechanism and design strategy will inspire new insights and thoughts on targeting design and will speed up precision medicine and contribute to cancer therapy and early diagnosis.

Internalization Characterization of Si Nanorod with Camouflaged Cell Membrane Proteins Reveals ATXN2 as a Negative Regulator

The fabrication of shape-controlled nanocarriers is critical for efficient delivery of biomolecules across the cell membrane. Surface coating of the nanocarrier can improve internalization efficiency. Here, we developed a facile method of silicon nanorod fabrication leading to a controlled size and shape. We then systematically evaluated five surface modifications with membrane proteins from different cancer cell lines including MCF7, MD231, Hela, Panc-PDX, and Panc-1. We demonstrated that silicon nanorods coated with either a homolytic or heterolytic membrane protein coating have significantly improved internalization efficiency as compared with uncoated Si nanorods. To elucidate the molecular mechanism of the improved efficiency associated with a modified coating, we analyzed the coating membrane proteins derived from five cell lines with proteomics and identified 601 proteins shared by different cell sources. These proteins may function as cell-substrate adhesion molecules that contribute to the enhanced internalization. We also tested the internalization efficiency of nanorods with different coatings in each of the five cell lines to determine the influencing factors from target cells. We found that the internalization efficiency varied among different target cells, and the ranking of the average efficiency was as follows: Hela > Panc-PDX > MD231 > MCF7 > Panc-1. The bioinformatics analysis suggested that the low internalization efficiency in Panc-1 cells might be associated with the upregulation of ATXN2, which is a negative regulator of endocytosis. We further demonstrated that ATXN2 knockdown with specific siRNA significantly improved nanorod internalization efficiency in Panc-1 cells suggesting that ATXN2 can be a reference for efficiency prediction of nanoparticle delivery to tumor cells. Thus, we studied the effect of different cancer cell membrane proteins on nanorod uptake efficiencies. These results can improve nanorod internalization to cancer cells, including a fundamental understanding of the internalization efficiency of cancer cells.

Surface Effects and Optical Properties of Self-Assembled Nanostructured a-Si:Al

We present a study of the surface effects and optical properties of the self-assembled nanostructures comprised of vertically aligned 5 nm-diameter Al nanowires embedded in an amorphous Si matrix (a-Si:Al). The controlled (partial) removal of Al nanowires in a selective etching process yielded nanoporous a-Si media with a variable effective surface area. Different spectroscopy techniques, such as X-ray photoelectron spectroscopy (XPS), UV-Vis spectrophotometry and photoluminescence (PL), have been combined to investigate the impact of such nanostructuring on optical absorption and emission properties. We also examine long-term exposure to air ambient and show that increasing level of surface oxidation determines the oxide defect-related nature of the dominant PL emission from the nanoporous structures. The role of bulk, nanosize and surface effects in optical properties has been separated and quantified, providing a better understanding of the potential of such nanoporous a-Si:Al structures for future device developments.

Highly sensitive detection of CTLA-4-positive T-cell subgroups based on nanobody and fluorescent carbon quantum dots

The detection of cytotoxic T-lymphocyte antigen-4-positive (CTLA-4⁺) T-cell subgroups in peripheral blood samples and tumor tissues is of great significance. In the present study, a rapid, succinct and efficient method was designed for the detection of CTLA-4⁺ human T cells using a CTLA-4-specific nanobody-fluorescent carbon quantum dots complex (QDs-Nb36). QDs-Nb36 was used for high sensitivity detection of CTLA-4⁺ T cells by flow cytometry or immumofluorescent staining. The present study demonstrated that the novel technique was more specific and effective in the detection of CTLA-4⁺ T-cell ratio in the peripheral blood and tumor tissues compared with a traditional monoclonal antibody approach. Furthermore, no significant toxicity was identified in vitro and in vivo, thus suggesting that the method may have broad applications for the detection of certain lowly expressed targets.

Forty-five-year evolution of probiotic therapy

In the past forty-five years, the field of probiotics has grown from a handful of laboratory studies and clinical ideas into a legitimate research and translational entity conferring multiple benefits to humans around the world. This has been founded upon three principles: (i) the need for alterna-tives to drugs that either have sub-optimal efficacy or severe adverse effects; (ii) a growing interest in natural products and microbes, in particular cata-lyzed by studies showing the extent of microbes within humans and on our planet; and (iii) evidence on the genetics and metabolic properties of probi-otic strains, and clinical studies showing their effectiveness. While some man-ufacturers have sadly taken advantage of the market growth to sell supple-ments and foods they term probiotic, without the necessary human study evidence, there are more and more companies basing their formulations on science. Adherence to the definition of what constitutes a probiotic, conclu-sions based on tested products not generalizations of the whole field, and applications emanating from microbiome research identifying new strains that provide benefits, will make the next forty-five years significantly changed approaches to health management. Exciting applications will emerge for car-diovascular, urogenital, respiratory, brain, digestive and skin health, detoxifi-cation, as well as usage across the world's ecosystems.