Review: Bioanalytical applications of biomolecule-functionalized nanometer-sized doped silica particles

Overview on the Development of Electrochemical Immunosensors by the Signal Amplification of Enzyme- or Nanozyme-Based Catalysis Plus Redox Cycling

Enzyme-linked electrochemical immunosensors have attracted considerable attention for the sensitive and selective detection of various targets in clinical diagnosis, food quality control, and environmental analysis. In order to improve the performances of conventional immunoassays, significant efforts have been made to couple enzyme-linked or nanozyme-based catalysis and redox cycling for signal amplification. The current review summarizes the recent advances in the development of enzyme- or nanozyme-based electrochemical immunosensors with redox cycling for signal amplification. The special features of redox cycling reactions and their synergistic functions in signal amplification are discussed. Additionally, the current challenges and future directions of enzyme- or nanozyme-based electrochemical immunosensors with redox cycling are addressed.

Controlled Growth of Large SiO2 Shells onto Semiconductor Colloidal Nanocrystals: A Pathway Toward Photonic Integration

The growth of SiO2 shells on semiconductor nanocrystals is an established procedure and it is widely employed to provide dispersibility in polar solvents, and increased stability or biocompatibility. However, to exploit this shell to integrate photonic components on semiconductor nanocrystals, the growth procedure must be finely tunable and able to reach large particle sizes (around 100 nm or above). Here, we demonstrate that these goals are achievable through a design of experiment approach. Indeed, the use of a sequential full-factorial design allows us to carefully tune the growth of SiO2 shells to large values while maintaining a reduced size dispersion. Moreover, we show that the growth of a dielectric shell alone can be beneficial in terms of emission efficiency for the nanocrystal. We also demonstrate that, according to our modeling, the subsequent growth of two shells with increasing refractive index leads to an improved emission efficiency already at a reduced SiO2 sphere radius.

Sensitive electrochemical gold nanoparticle-based immunosensor for norovirus detection in food samples

Norovirus (NoV) infection is one of the most common non-bacterial causes of gastroenteritis among the population worldwide. From the point of view of medical diagnostics, it is important to develop a system that would sensitively and selectively detect norovirus from a patient's sample in order to control and limit its spread. In this paper, we present a stable and sensitive NoV (mouse model) detection matrix in infected food samples. The bio-platform was made of a modified gold electrode with a self-assembled l-cysteine monolayer, covered with gold nanoparticles, a linker and an antibody specific to the VP1 surface protein of the virus. Binding of the VP1 protein to the antibody caused a decrease in the current strength confirmed by electrochemical techniques - cyclic voltammetry (CV) and differential pulse voltammetry. The reduction of the current was proportional to the concentration of NoV sample. The biosensors showed high sensitivity and linearity in a range from 1 × 10-9 to 1 × 10-18 TCID50, with the detection limit of 1 × 10-18 TCID50. CV showed a diffusion-controlled process. In addition, each modification step was confirmed by scanning electron microscopy, electrochemical impedance spectroscopy, and CV. The described immunosensor showed excellent recovery values, good linearity and long-term stability, crucial parameters for biosensor construction.

Recent Breakthroughs in Using Quantum Dots for Cancer Imaging and Drug Delivery Purposes

Cancer is one of the leading causes of death worldwide. Because each person's cancer may be unique, diagnosing and treating cancer is challenging. Advances in nanomedicine have made it possible to detect tumors and quickly investigate tumor cells at a cellular level in contrast to prior diagnostic techniques. Quantum dots (QDs) are functional nanoparticles reported to be useful for diagnosis. QDs are semiconducting tiny nanocrystals, 2-10 nm in diameter, with exceptional and useful optoelectronic properties that can be tailored to sensitively report on their environment. This review highlights these exceptional semiconducting QDs and their properties and synthesis methods when used in cancer diagnostics. The conjugation of reporting or binding molecules to the QD surface is discussed. This review summarizes the most recent advances in using QDs for in vitro imaging, in vivo imaging, and targeted drug delivery platforms in cancer applications.

Functionalized nanoparticles: Tailoring properties through surface energetics and coordination chemistry for advanced biomedical applications

Significant advances in nanoparticle-related research have been made in the past decade, and amelioration of properties is considered of utmost importance for improving nanoparticle bioavailability, specificity, and catalytic performance. Nanoparticle properties can be tuned through in-synthesis and post-synthesis functionalization operations, with thermodynamic and kinetic parameters playing a crucial role. In spite of robust functionalization techniques based on surface chemistry, scalable technologies have not been explored well. The coordination enhancement via surface functionalization through organic/inorganic/biomolecules material has attracted much attention with morphology modification and shape tuning, which are indispensable aspects in the colloidal phase during biomedical applications. It is envisioned that surface amelioration influences the anchoring properties of nano interfaces for the immobilization of functional groups and biomolecules. In this work, various nanostructure and anchoring methodologies have been discussed, aiming to exploit their full potential in precision engineering applications. Simultaneous discussions on emerging characterization strategies for functionalized assemblies have been made to gain insights into functionalization chemistry. An overview of current advances and prospects of functionalized nanoparticles has been presented, with an emphasis on controllable attributes such as size, shape, morphology, functionality, surface features, Debye and Casimir interactions.

Probing the interaction of zinc oxide nanorods with human serum albumin: A spectroscopic approach

Bio-functionalized metal oxide nanoparticles (NPs) have been taken great importance in biomedical fields. The use of nanoparticles as delivery agents of therapeutic molecules led the researchers to emphasize the potential impact of these NPs on bio-macromolecules as protein-nanoparticle complexes, which also extended their importance as vehicles in targeted drug delivery systems due to increased ease of administration, firmness, reduced toxic side effects, and half-life of drugs. Since human serum albumin is the blood protein responsible for transporting materials in the blood system, the interaction of these particles with HSA is essential to be understood before considering the nanoparticles for any individual biomedical application. In the present study, we synthesized zinc-oxide nanorods (ZONRs) using a microwave-assisted synthesis technique, and characterized them by XRD, FTIR, Raman, SEM-EDX, UV-Vis spectroscopy, and photoluminescence (PL) spectroscopy methods. The interaction studies were carried out using fluorescence spectroscopy, and the change in secondary structure was analyzed using CD spectroscopy. The results of MTT cell viability assay demonstrated that the ZONRs has potential cytotoxic properties.

From Synthetic Route of Silica Nanoparticles to Theranostic Applications

The advancements in nanotechnology have quickly developed a new subject with vast applications of nanostructured materials in medicine and pharmaceuticals. The enormous surface-to-volume ratio, ease of surface modification, outstanding biocompatibility, and, in the case of mesoporous nanoparticles, the tunable pore size make the silica nanoparticles (SNPs) a promising candidate for nano-based medical applications. The preparation of SNPs and their contemporary usage as drug carriers, contrast agents for imaging, carrier of photosensitizers (PS) in photodynamic, as well as photothermal treatments are intensely discussed in this review. Furthermore, the potential harmful responses of silica nanoparticles are reviewed using data obtained from in vitro and in vivo experiments conducted by several studies. Moreover, we showcase the engineering of SNPs for the theranostic applications that can address several intrinsic limitations of conventional therapeutics and diagnostics. In the end, a personal perspective was outlined to state SNPs’ current status and future directions, focusing on SNPs’ significant potentiality and opportunities.

Multifunctional Role of Silica in Pharmaceutical Formulations

Due to the high surface area, adjustable surface and pore structures, and excellent biocompatibility, nano- and micro-sized silica have certainly attracted the attention of many researchers in the medical fields. This review focuses on the multifunctional roles of silica in different pharmaceutical formulations including solid preparations, liquid drugs, and advanced drug delivery systems. For traditional solid preparations, it can improve compactibility and flowability, promote disintegration, adjust hygroscopicity, and prevent excessive adhesion. As for liquid drugs and preparations, like volatile oil, ethers, vitamins, and self-emulsifying drug delivery systems, silica with adjustable pore structures is a good adsorbent for solidification. Also, silica with various particle sizes, surface characteristics, pore structure, and surface modification controlled by different synthesis methods has gained wide attention owing to its unparalleled advantages for drug delivery and disease diagnosis. We also collate the latest pharmaceutical applications of silica sorted out by formulations. Finally, we point out the thorny issues for application and survey future trends pertaining to silica in an effort to provide a comprehensive overview of its future development in the medical fields. Graphical Abstract.

Single-step acid-catalyzed synthesis of luminescent colloidal organosilica nanobeads

We present a single-step, room-temperature synthesis of fluorescent organosilica nanobeads (FOS NBs). The FOS NBs were synthesized under aqueous conditions using (3-aminopropyl)triethoxysilane (APTES) as the silicon source in the presence of L-ascorbic acid (L-AA). In the APTES/L-AA/water ternary phase, the hydrolysis and condensation reaction of APTES occurred under acidic conditions to form spherical FOS NBs with an average diameter of 426.8 nm. FOS NBs exhibit excellent colloidal stability in aqueous media. The formation of FOS NBs was complete within a 10 min reaction time, which indicates potential for large-scale mass-production synthesis of luminescent colloidal NBs. The FOS NBs exhibited blue photoluminescence (PL) under UV excitation in the absence of an additional high temperature calcination process or with the incorporation of any fluorophores. This phenomenon is attributed to the presence of carbon-containing defects, which act as luminescent centers formed by the reaction between amino groups in the APTES and L-ascorbic acid reductant. Finally, the results of a cytotoxicity test and cellular uptake experiments revealed that the FOS NBs showed potential as optical contrast agents for bioimaging.

pH-EVD: A pH-Paper-Based Extraction and Visual Detection System for Instrument-Free SARS-CoV-2 Diagnostics

The ongoing pandemic of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused millions of deaths worldwide. However, most SARS-CoV-2 detection methods depend on time-consuming sample preparation and large detection instruments. Herein, a method employing nonbleeding pH paper to achieve both RNA extraction and visual isothermal amplification is proposed, enabling rapid, instrument-free SARS-CoV-2 detection. By taking advantage of capillary forces, pH-paper-based RNA extraction can be accomplished within 1 min without need for any equipment. Further, the pH paper can mediate dye-free visual isothermal amplification detection. In less than a 46-min sample-to-answer time, pH-paper-based extraction and visual detection (termed pH-EVD) can consistently detect 1200 genome equivalents per microliter of SARS-CoV-2 in saliva, which is comparable to TaqMan probe-based quantitative reverse transcription PCR (RT-qPCR). Through coupling with a chemically heated incubator called a smart cup, the instrument-free, pH-EVD-based SARS-CoV-2 detection method on 30 nasopharyngeal swab samples and 33 contrived saliva samples is clinically validated. Thus, the pH-EVD method provides simple, rapid, reliable, low-cost, and instrument-free SARS-CoV-2 detection and has the potential to streamline onsite COVID-19 diagnostics.

Structure and Dynamics Perturbations in Ubiquitin Adsorbed or Entrapped in Silica Materials Are Related to Disparate Surface Chemistries Resolved by Solid-State NMR Spectroscopy

Protein immobilization on material surfaces is emerging as a powerful tool in the design of devices and active materials for biomedical and pharmaceutical applications as well as for catalysis. Preservation of the protein's biological functionality is crucial to the design process and is dependent on the ability to maintain its structural and dynamical integrity while removed from the natural surroundings. The scientific techniques to validate the structure of immobilized proteins are scarce and usually provide limited information as a result of poor resolution. In this work, we benchmarked the ability of standard solid-state NMR techniques to resolve the effects of binding to dissimilar silica materials on a model protein. In particular, the interactions between ubiquitin and the surfaces of MCM41, SBA15, and silica formed in situ were tested for their influence on the structure and dynamics of the protein. It is shown that the protein's globular fold in the free state is only slightly perturbed in the three silica materials. Local motions on a residue level that are quenched by immobilization or, conversely, that arise from the process are also detailed. NMR measurements show that these perturbations are unique to each silica material and can serve as reporters of the characteristic surface chemistry.

Morphological Analysis of PSMA/PEI Core-Shell Nanoparticles Synthesized by Soap-Free Emulsion Polymerization

Emulsion polymerization presents the disadvantage that the physical properties of polymer particles are altered by surfactant adsorption. Therefore, in the soap-free emulsion polymerization method, a hydrophilic initiator is utilized while inducing repulsion among particles on the polymer particle surface, resulting in stable polymer particle production. In this study, we developed a methodology wherein spherical and uniform poly(styrene-co-maleic anhydride) (PSMA)/polyethyleneimine (PEI) core–shell nanoparticles were prepared. Further, their morphology was analyzed. During PSMA polymerization, the addition of up to 30% maleic anhydride (MA) resulted in stable polymerization. In PSMA/PEI nanoparticle fabrication, the number of reactants increased with increased initial monomer feed amounts; consequently, the particle size increased, and as the complete monomer consumption time increased, the particle distribution widened. The styrene (St) copolymer acted as a stabilizer, reducing particle size and narrowing particle distribution. Furthermore, the monomers were more rapidly consumed at high initiator concentrations, irrespective of the initiator used, resulting in increased particle stability and narrowed particle distribution. The shell thickness and particle size were PEI feed ratio dependent, with 0.08 being the optimal PEI-to-MA ratio. The fabricated nanoparticles possess immense potential for application in environmental science and in chemical and health care industries.

Process Variability in Top-Down Fabrication of Silicon Nanowire-Based Biosensor Arrays

Silicon nanowire field-effect transistors (SiNW-FET) have been studied as ultra-high sensitive sensors for the detection of biomolecules, metal ions, gas molecules and as an interface for biological systems due to their remarkable electronic properties. "Bottom-up" or "top-down" approaches that are used for the fabrication of SiNW-FET sensors have their respective limitations in terms of technology development. The "bottom-up" approach allows the synthesis of silicon nanowires (SiNW) in the range from a few nm to hundreds of nm in diameter. However, it is technologically challenging to realize reproducible bottom-up devices on a large scale for clinical biosensing applications. The top-down approach involves state-of-the-art lithography and nanofabrication techniques to cast SiNW down to a few 10s of nanometers in diameter out of high-quality Silicon-on-Insulator (SOI) wafers in a controlled environment, enabling the large-scale fabrication of sensors for a myriad of applications. The possibility of their wafer-scale integration in standard semiconductor processes makes SiNW-FETs one of the most promising candidates for the next generation of biosensor platforms for applications in healthcare and medicine. Although advanced fabrication techniques are employed for fabricating SiNW, the sensor-to-sensor variation in the fabrication processes is one of the limiting factors for a large-scale production towards commercial applications. To provide a detailed overview of the technical aspects responsible for this sensor-to-sensor variation, we critically review and discuss the fundamental aspects that could lead to such a sensor-to-sensor variation, focusing on fabrication parameters and processes described in the state-of-the-art literature. Furthermore, we discuss the impact of functionalization aspects, surface modification, and system integration of the SiNW-FET biosensors on post-fabrication-induced sensor-to-sensor variations for biosensing experiments.

Recent Advances in Inorganic Nanomaterials Synthesis Using Sonochemistry: A Comprehensive Review on Iron Oxide, Gold and Iron Oxide Coated Gold Nanoparticles

Sonochemistry uses ultrasound to improve or modify chemical reactions. Sonochemistry occurs when the ultrasound causes chemical effects on the reaction system, such as the formation of free radicals, that intensify the reaction. Many studies have investigated the synthesis of nanomaterials by the sonochemical method, but there is still very limited information on the detailed characterization of these physicochemical and morphological nanoparticles. In this comprehensive review, recent advances in the sonochemical synthesis of nanomaterials based on iron oxide nanoparticles (Fe3O4NP), gold nanoparticles (AuNP) and iron oxide-coated gold nanoparticles (Fe3O4@Au NP) are discussed. These materials are the most studied materials for various applications, such as medical and commercial uses. This review will: (1) address the simple processing and observations on the principles of sonochemistry as a starting point for understanding the fundamental mechanisms, (2) summarize and review the most relevant publications and (3) describe the typical shape of the products provided in sonochemistry. All in all, this review's main outcome will provide a comprehensive overview of the available literature knowledge that promotes and encourages future sonochemical work.

Selective Gas-Phase Functionalization of SiO2 and SiNx Surfaces with Hydrocarbons

Selective functionalization of dielectric surfaces is required for area-selective atomic layer deposition and etching. We have identified precursors for the selective gas-phase functionalization of plasma-deposited SiO₂ and SiN_x surfaces with hydrocarbons. The corresponding reaction mechanism of the precursor molecules with the two surfaces was studied using in situ surface infrared spectroscopy. We show that at a substrate temperature of 70 °C, cyclic azasilanes preferentially react with an -OH-terminated SiO₂ surface over a -NH_x-terminated SiN_x surface with an attachment selectivity of ∼5.4, which is limited by the partial oxidation of the SiN_x surface. The cyclic azasilane undergoes a ring-opening reaction where the Si-N bond cleaves upon the reaction with surface -OH groups forming a Si-O-Si linkage. After ring opening, the backbone of the grafted hydrocarbon is terminated with a secondary amine, -NHCH₃, which can react with water to form an -OH-terminated surface and release CH₃NH₂ as the product. The surface coverage of the grafted cyclic azasilane is calculated as ∼3.3 × 10¹⁴ cm^-2, assuming that each reacted -OH group contributes to one hydrocarbon linkage. For selective attachment to SiN_x over SiO₂ surfaces, we determined the reaction selectivity of aldehydes. We demonstrate that aldehydes selectively attach to SiN_x over SiO₂ surfaces, and for the specific branched aliphatic aldehyde used in this work, almost no reaction was detected with the SiO₂ surface. A fraction of the aldehyde molecules reacts with surface -NH₂ groups to form an imine (Si-N═C) surface linker with H₂O released as the byproduct. The other fraction of the aldehydes also reacts with surface -NH₂ groups but do not undergo the water-elimination step and remains attached to the surface as an aminoalcohol (Si-NH-COH-). The surface coverage of the grafted aldehyde is calculated as ∼9.8 × 10¹⁴ cm^-2 using a known infrared absorbance cross-section for the -C(CH₃)₃ groups.

Recent advances in the design of inorganic and nano-clay particles for the treatment of brain disorders

Inorganic materials, in particular nanoclays and silica nanoparticles, have attracted enormous attention due to their versatile and tuneable properties, making them ideal candidates for a wide range of biomedical applications, such as drug delivery. This review aims at overviewing recent developments of inorganic nanoparticles (like porous or mesoporous silica particles) and different nano-clay materials (like montmorillonite, laponites or halloysite nanotubes) employed for overcoming the blood brain barrier (BBB) in the treatment and therapy of major brain diseases such as Alzheimer's, Parkinson's, glioma or amyotrophic lateral sclerosis. Recent strategies of crossing the BBB through invasive and not invasive administration routes by using different types of nanoparticles compared to nano-clays and inorganic particles are overviewed.

Biomedical application of mesoporous silica nanoparticles as delivery systems: a biological safety perspective

The application of mesoporous silica nanoparticles (MSNs) as drug delivery systems to deliver drugs, proteins, and genes has expanded considerably in recent years, using in vitro and animal studies. For future translation to clinical applications, the biological safety aspects of MSNs must be considered carefully. This paper reviews the biosafety of MSNs, examining key issues such as biocompatibility, effects on immune cells and erythrocytes, biodistribution, biodegradation and clearance, and how these vary depending on the effects of the physical and chemical properties of MSNs such as particle size, porosity, morphology, surface charge, and chemical modifications. The future use of MSNs as a delivery system must extend beyond what has been learnt thus far using rodent animal models to encompass larger animals.

Controlling the growth of a SiO2 coating on hydrophobic CsPbBr3 nanocrystals towards aqueous transfer and high luminescence

Silica coating can effectively solve the stability issue of lead halide perovskite nanomaterials. However, it is difficult to achieve aqueous SiO₂ coating on hydrophobic CsPbBr₃ nanocrystals (NCs). In this paper, the hydrolysis process of tetramethoxysilane was controlled to get a homogeneous SiO₂ coating or a NC/SiO₂ Janus structure. In step 1, the Cs₄PbBr₆ NCs were silanized using partially hydrolyzed tetramethoxysilane (PH-TMOS). During this process, the Si-OH groups which came from PH-TMOS were absorbed onto the surface of the Cs₄PbBr₆ NCs with the removal of hydrophobic oleic acid (OA) ligands. In step 2, phase transformation from Cs₄PbBr₆ to CsPbBr₃ occurred owing to the injection of water. Meanwhile, further hydrolysis of TMOS took place and generated cross-linked Si-O-Si. Because the silanization in step 1 created lots of growth sites, the condensation of SiO₂ was not limited to the interface between water and hexane. After growing for 12 h, the fully covered CsPbBr₃@SiO₂ capsules were prepared. The anion exchange reactions of the CsPbBr₃@SiO₂ capsules were studied. Only one even and symmetric PL peak was apparent during the anion exchange process, which was different from the bare CsPbBr₃ NCs. This result demonstrated that the SiO₂ shell can act as a buffer layer to block the direct contact of CsPbBr₃ with the excess PbBr₂ precursor in solution. Compared with the CsPbBr₃ NCs, CsPbBr₃@SiO₂ showed better stability in polar solvent and air. A bright green emission was also observed under UV light after 90 days. The successful preparation of CsPbBr₃@SiO₂ capsules with enhanced stability paves the way for the further development of lead halide perovskite nanomaterials.

A label-free electrochemical immunosensor based on encapsulated signal molecules in mesoporous silica-coated gold nanorods for ultrasensitive assay of procalcitonin

For immobilization and signal amplification of the probes, it is feasible and promising by using porous nanomaterials as nanocarriers. Herein, a novel label-free electrochemical immmunosensor was efficiently designed for ultrasensitive detection of procalcitonin (PCT). The immunosensor was prepared by using porous silica-coated gold nanorods (Au NRs@m-SiO₂) to load electroactive dye thionine (Thi) on the electrode surface. Apart from the improved electrical conductivity, the porous feature highly increased the loading amount of Thi to boost the detection signals, while the good biocompatibility and protective microenvironment are beneficial to the largely improved stability for the target. For quantification of PCT, the developed immunosensor exhibited a good linear relationship in the antigen concentration range of 0.001-100 ng mL^-1 with an ultra-low limit of detection (LOD, 0.39 pg mL^-1, S/N = 3). Moreover, the built platform was successfully applied to such assay in human serum samples. The research provides some valuable guidelines for clinical screening and diagnosis of other biomarkers.

Optical Sensing and Imaging of pH Values: Spectroscopies, Materials, and Applications

This is the first comprehensive review on methods and materials for use in optical sensing of pH values and on applications of such sensors. The Review starts with an introduction that contains subsections on the definition of the pH value, a brief look back on optical methods for sensing of pH, on the effects of ionic strength on pH values and pKa values, on the selectivity, sensitivity, precision, dynamic ranges, and temperature dependence of such sensors. Commonly used optical sensing schemes are covered in a next main chapter, with subsections on methods based on absorptiometry, reflectometry, luminescence, refractive index, surface plasmon resonance, photonic crystals, turbidity, mechanical displacement, interferometry, and solvatochromism. This is followed by sections on absorptiometric and luminescent molecular probes for use pH in sensors. Further large sections cover polymeric hosts and supports, and methods for immobilization of indicator dyes. Further and more specific sections summarize the state of the art in materials with dual functionality (indicator and host), nanomaterials, sensors based on upconversion and 2-photon absorption, multiparameter sensors, imaging, and sensors for extreme pH values. A chapter on the many sensing formats has subsections on planar, fiber optic, evanescent wave, refractive index, surface plasmon resonance and holography based sensor designs, and on distributed sensing. Another section summarizes selected applications in areas, such as medicine, biology, oceanography, bioprocess monitoring, corrosion studies, on the use of pH sensors as transducers in biosensors and chemical sensors, and their integration into flow-injection analyzers, microfluidic devices, and lab-on-a-chip systems. An extra section is devoted to current challenges, with subsections on challenges of general nature and those of specific nature. A concluding section gives an outlook on potential future trends and perspectives.

Development of Silica-Based Biodegradable Submicrometric Carriers and Investigating Their Characteristics as in Vitro Delivery Vehicles

Nanostructured silica (SiO2)-based materials are attractive carriers for the delivery of bioactive compounds into cells. In this study, we developed hollow submicrometric particles composed of SiO2 capsules that were separately loaded with various bioactive molecules such as dextran, proteins, and nucleic acids. The structural characterization of the reported carriers was conducted using transmission and scanning electron microscopies (TEM/SEM), confocal laser scanning microscopy (CLSM), and dynamic light scattering (DLS). Moreover, the interaction of the developed carriers with cell lines was studied using standard viability, proliferation, and uptake assays. The submicrometric SiO2-based capsules loaded with DNA plasmid encoding green fluorescence proteins (GFP) were used to transfect cell lines. The obtained results were compared with studies made with similar capsules composed of polymers and show that SiO2-based capsules provide better transfection rates on the costs of higher toxicity.

Nanomaterials in Dentistry: State of the Art and Future Challenges

Nanomaterials are commonly considered as those materials in which the shape and molecular composition at a nanometer scale can be controlled. Subsequently, they present extraordinary properties that are being useful for the development of new and improved applications in many fields, including medicine. In dentistry, several research efforts are being conducted, especially during the last decade, for the improvement of the properties of materials used in dentistry. The objective of the present article is to offer the audience a complete and comprehensive review of the main applications that have been developed in dentistry, by the use of these materials, during the last two decades. It was shown how these materials are improving the treatments in mainly all the important areas of dentistry, such as endodontics, periodontics, implants, tissue engineering and restorative dentistry. The scope of the present review is, subsequently, to revise the main applications regarding nano-shaped materials in dentistry, including nanorods, nanofibers, nanotubes, nanospheres/nanoparticles, and zeolites and other orders porous materials. The results of the bibliographic analysis show that the most explored nanomaterials in dentistry are graphene and carbon nanotubes, and their derivatives. A detailed analysis and a comparative study of their applications show that, although they are quite similar, graphene-based materials seem to be more promising for most of the applications of interest in dentistry. The bibliographic study also demonstrated the potential of zeolite-based materials, although the low number of studies on their applications shows that they have not been totally explored, as well as other porous nanomaterials that have found important applications in medicine, such as metal organic frameworks, have not been explored. Subsequently, it is expected that the research effort will concentrate on graphene and zeolite-based materials in the coming years. Thus, the present review paper presents a detailed bibliographic study, with more than 200 references, in order to briefly describe the main achievements that have been described in dentistry using nanomaterials, compare and analyze them in a critical way, with the aim of predicting the future challenges.

Recent Trends in Electrochemical Sensors for Vital Biomedical Markers Using Hybrid Nanostructured Materials

This work provides a succinct insight into the recent developments in electrochemical quantification of vital biomedical markers using hybrid metallic composite nanostructures. After a brief introduction to the biomarkers, five types of crucial biomarkers, which require timely and periodical monitoring, are shortlisted, namely, cancer, cardiac, inflammatory, diabetic and renal biomarkers. This review emphasizes the usage and advantages of hybrid nanostructured materials as the recognition matrices toward the detection of vital biomarkers. Different transduction methods (fluorescence, electrophoresis, chemiluminescence, electrochemiluminescence, surface plasmon resonance, surface-enhanced Raman spectroscopy) reported for the biomarkers are discussed comprehensively to present an overview of the current research works. Recent advancements in the electrochemical (amperometric, voltammetric, and impedimetric) sensor systems constructed with metal nanoparticle-derived hybrid composite nanostructures toward the selective detection of chosen vital biomarkers are specifically analyzed. It describes the challenges involved and the strategies reported for the development of selective, sensitive, and disposable electrochemical biosensors with the details of fabrication, functionalization, and applications of hybrid metallic composite nanostructures.

Tetraphenylethene-Based Supramolecular Coordination Frameworks with Aggregation-Induced Emission for an Artificial Light-Harvesting System

Supramolecular coordination is an efficient strategy to construct supramolecular coordination frameworks with predesigned structures, assembled shapes, and specific function. In this work, we report the synthesis, structural characterization, and photophysical property of two tetraphenylethene-based supramolecular coordination frameworks 1a and 1b formed from 1,1,2,2-tetrakis(4-(pyridin-4-yl)phenyl)ethene (2a) or 1,1,2,2-tetrakis(4-((E)-2-(pyridin-4-yl)vinyl)phenyl)ethene (2b) and a linear difunctional platinum(II) ligand (3a) via coordination-driven self-assembly. Controlled by the specific angularity and geometry of tetraphenylethene (with 60° and 120°) and difunctional Pt(II) linker (with 180°), these supramolecular coordination frameworks possess a well-defined and two-dimensional (2D) rhombic network-type topology with good periodicity and porosity. Given the aggregation-induced emission (AIE) property of tetraphenylethene units and the porosity of frameworks, 1a and 1b have been successfully used as fluorescent platforms and energy donors to fabricate efficient artificial light-harvesting materials with two fluorescent acceptors (Nile Red and Sulforhodamine 101) via noncovalent interactions in aqueous solution. Furthermore, these light-harvesting materials have been applied for promoting cancer cell imaging with a full shift of imaging channels from blue/green channels to the red channel. Thus, this study provides an effective approach to fabricate functional frameworks as fluorescent platforms for developing more fluorescent materials.

Biosensing of prostate specific antigen (PSA) in human plasma samples using biomacromolecule encapsulation into KCC-1-npr-NH2: A new platform for prostate cancer detection

Prostate-specific antigen (PSA) is a high molecular weight glycoprotein that is used as a marker for the diagnosis of prostate cancer and is therefore important in the medical field. In this study, a novel sandwich type immunoassay was designed based on encapsulation of biotinylated antibody into KCC-1-npr-NH₂. KCC-1-npr-NH₂ stabilized the stability of the primary antibody. So, encapsulated Ab1 was immobilized on the surface of glassy carbon electrode. Field emission scanning electron microscope (FE-SEM) was employed to monitor the sensor fabrication. The engineered immunosensor was used for the detection of PSA using differential pulse voltammetry (DPVs) and square wave voltammetry (SWVs) techniques. The proposed interface lead to enhancement of accessible surface area for immobilizing a high amount of anti-PSA antibody, increasing electrical conductivity, boosting stability, catalytic properties and biocompatibility. The intensity of electrochemical signals is also increased by the use of AuNPs functionalized with CysA used in secondary antibody (HRP conjugated PSA) structure. Under optimal conditions, the designed immuno-assay provide a good analytical performance for quantifying the PSA marker in the linear range of 1 to 60 μg/l.

Fluorescent SiO2@Tb3+(PET-TEG)3Phen Hybrids as Nucleating Additive for Enhancement of Crystallinity of PET

A hybrid polymer of SiO₂@Tb³⁺(poly(ethylene terephthalate)-tetraglycol)₃ phenanthroline (SiO₂@Tb³⁺(PET-TEG)₃Phen) was synthesized by mixing of inorganic SiO₂ nanoparticles with polymeric segments of PET-TEG, whereas PET-TEG was achieved through multi-step functionalization strategy. Tb³⁺ ions and β-diketonate ligand Phen were added in resulting material. The experimental results demonstrated that it was well blended with PET as a robust additive, and not only promoted the crystallinity, but also possessed excellent luminescence properties. An investigation of the mechanism revealed that the SiO₂ nanoparticles functioned as a crystallization promotor; the Tb³⁺ acted as the fluorescent centre; and the PET-TEG segments played the role of linker and buffer, providing better compatibility of PET matrix with the inorganic component. This work demonstrated that hybrid polymers are appealing as multifunctional additives in the polymer processing and polymer luminescence field.

Coating of upconversion nanoparticles with silica nanoshells of 5-250 nm thickness

A concept for the growth of silica shells with a thickness of 5-250 nm onto oleate-coated NaYF₄:Yb³⁺/Er³⁺ upconversion nanoparticles (UCNP) is presented. The concept enables the precise adjustment of shell thicknesses for the preparation of thick-shelled nanoparticles for applications in plasmonics and sensing. First, an initial 5-11 nm thick shell is grown onto the UCNPs in a reverse microemulsion. This is followed by a stepwise growth of these particles without a purification step, where in each step equal volumes of tetraethyl orthosilicate and ammonia water are added, while the volumes of cyclohexane and the surfactant Igepal^® CO-520 are increased so that the ammonia water and surfactant concentrations remain constant. Hence, the number of micelles stays constant, and their size is increased to accommodate the growing core-shell particles. Consequently, the formation of core-free silica particles is suppressed. When the negative zeta potential of the particles, which continuously decreased during the stepwise growth, falls below -40 mV, the particles can be dispersed in an ammoniacal ethanol solution and grown further by the continuous addition of tetraethyl orthosilicate to a diameter larger than 500 nm. Due to the high colloidal stability, a coalescence of the particles can be suppressed, and single-core particles are obtained. This strategy can be easily transferred to other nanomaterials for the design of plasmonic nanoconstructs and sensor systems.

Efficient Endocytosis of Inorganic Nanoparticles with Zwitterionic Surface Functionalization

PEGylation, which has traditionally been the method of choice to enhance the colloidal stability of nanostructures designed for biological applications and to prevent nonspecific protein adsorption, is now being challenged by short zwitterionic ligands. Inspired by the zwitterionic nature of cell membranes, these ligands have the potential to push forward the field of nanoparticles for nanomedicine. In this work, we report a thorough analysis of the surface chemistry of silica-coated luminescent CdSe/CdS quantum dots functionalized with either PEG-silane or zwitterionic sulfobetaine-silane by quantitative nuclear magnetic resonance spectroscopy. We demonstrate the differences in the cellular uptake propensity between particles with these two ligands. Although both ligands offer good colloidal stability in a crowded cell culture medium, the zwitterionic-functionalized nanoparticles with an optimized ligand density showed to be more easily endocytosed by HeLa cells. This approach can readily be transferred to other nanoparticle systems offering a wealth of unique properties, with great potential for intracellular bioapplications.

Exposure to Zinc oxide nanoparticles during pregnancy induces oocyte DNA damage and affects ovarian reserve of mouse offspring

Zinc oxide nanoparticles (nZnO) have been shown to have higher toxic effects likely due to their ion-shedding ability and low solubility under neutral conditions. In order to investigate whether exposure to nZnO during embryonic development affects ovary development, 12.5 day post coitum (dpc) fetal mouse ovaries were cultured in the presence of nZnO for 6 days. We found that the nanoparticles (NPs) accumulated within the oocyte cytoplasm in a dose dependent manner, caused DNA damage and apoptosis, and result in a significant decrease in oocyte numbers. No such effects were observed when the ovaries were incubated in the presence of ZnSO₄ or bulk ZnO as controls. In addition, we injected intravenously 16 mg/kg body weight nZnO in 12.5 dpc pregnant mice on two consecutive days and analyzed the ovaries of fetuses or offspring at three critical periods of oogenesis: 17.5 dpc, 3 days post-partum (dpp) and 21 dpp. Evidence of increased DNA damage in pachytene oocytes in fetal ovaries and impaired primordial follicle assembly and folliculogenesis dynamics in the ovaries of the offspring were found. Our results indicate that certain types of NPs affect pre- and post-natal oogenesis in vitro and in vivo.

Determination of conjugated protein on nanoparticles by an adaptation of the Coomassie blue dye method

A new accurate spectrophotometric method for protein determination on nanoparticles is described. The method is based on the Coomassie blue dye that binds to the basic and aromatic amino acid residues of proteins, especially arginine and lysine. A known amount of reagent dye was mixed with a variety of protein-loaded nanoparticles. Thereafter the unconjugated reagent was mixed with excess protein (bovine serum albumin) and titrated. In this method, the reacted dye on the protein coating of nanoparticle is directly determined, in opposite to the conventional method, in which the conjugated protein is determined as the difference between the non-conjugated protein found in the supernatant after centrifugation, and the total amount of protein originally used. This method is able to measure amounts of coated protein lower than 1 ppm.

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Simple and accurate method especially adapted for protein-coated nanoparticles.

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The amino acid residues of protein in the nanoparticle surface react with Coomassie brilliant blue dye.

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The unreacted dye is titrated with an excess of a standard protein.

Preparation of Fluorescence-Encoded Microspheres Based on Hydrophobic Conjugated Polymer-Dye Combination and the Immunoassay

Fluorescent microspheres are greatly demanded in many applications based on high-throughput suspension array technology. To realize the multiplexed assay, microspheres should be encoded to identify the interaction between analytes and spheres. This study advanced a strategy for preparing fluorescence-encoded microspheres, employing two hydrophobic fluorophores, poly(p-phenyleneethylene) (PPE), and Nile Red (NR), as well as the monodisperse amino-modified porous substrate polymeric spheres, poly(glycidyl methacrylate) microspheres (APGMA). Loading the fluorophores sequentially onto the substrate spheres via adsorption by immersing the spheres in the dipping solution of fluorophores resulted in the APGMA-PPE-NR spheres. By varying the concentration and combination of fluorophores in the solution, an array of 64-code APGMA-PPE-NR spheres was obtained and could be easily individually decoded via flow cytometry. A 2D dot plot from the flow cytometry of a set of mixed spheres with four different codes could also be differentiated, coincident with the overlaid plots of the spheres' corresponding codes but measured individually. These spheres were found to have good stability against washing, photobleaching, and thermal treatment. In addition, a sandwich immunoassay for the detection of goat IgG was performed, and the capability of the encoded spheres to be used in suspension array technology was demonstrated.

The Role of Electrochemical Immunosensors in Clinical Analysis

An immunosensor is a kind of affinity biosensor based on interactions between an antigen and specific antigen immobilized on a transducer surface. Immunosensors possess high selectivity and sensitivity due to the specific binding between antibody and corresponding antigen, making them a suitable platform for several applications especially in the medical and bioanalysis fields. Electrochemical immunosensors rely on the measurements of an electrical signal recorded by an electrochemical transducer and can be classed as amperometric, potentiometric, conductometric, or impedimetric depending on the signal type. Among the immunosensors, electrochemical immunosensors have been more perfected due to their simplicity and, especially their ability to be portable, and for in situ or automated detection. This review addresses the potential of immunosensors destined for application in clinical analysis, especially cancer biomarker diagnosis. The emphasis is on the approaches used to fabricate electrochemical immunosensors. A general overview of recent applications of the developed electrochemical immunosensors in the clinical approach is described.

De Novo Iron Oxide Hydroxide, Ferrihydrite Produced by Comamonas testosteroni Exhibiting Intrinsic Peroxidase-Like Activity and Their Analytical Applications

Natural enzyme mimics have attracted considerable attention due to leakage of enzymes and their easy denaturation during their storage and immobilization procedure. Here in this study, for the first time, a new iron oxide hydroxide, ferrihydrite - Fe_1.44O_0.32 (OH) _3.68 magnetic nanoparticles were synthesized by bacterial strain named Comamonas testosteroni. The characterization of the produced magnetic nanoparticles was confirmed by transmission electron microscopy (TEM), Fourier-transform spectroscopy (FTIR), X-ray diffraction (XRD), and magnetization hysteresis loops. Further, these extracted nanoparticles were proven to have biogenic magnetic behavior and to exhibit enhanced peroxidase-like activity. It is capable of catalyzing the oxidation of 3, 3', 5, 5'-Tetramethylbenzidine (TMB) by H₂O₂ to produce blue color (typical color reactions). Catalysis was examined to follow Michaelis-Menton kinetics and the good affinity to both H₂O₂ and TMB. The K _m value of the Fe_1.44O_0.32 (OH) _3.68 with H₂O₂ and TMB as the substrate was 0.0775 and 0.0155 mM, respectively, which were lower than that of the natural enzyme (HRP). Experiments of electron spin resonance (ESR) spectroscopy proved that the BMNPs could catalyze H₂O₂ to produce hydroxyl radicals. As a new peroxidase mimetic, the BMNPs were exhibited to offer a simple, sensitive, and selective colorimetric method for determination of H₂O₂ and glucose and efficiently catalyze the detection of glucose in real blood samples.

Robust Fluorine-Free and Self-Healing Superhydrophobic Coatings by H3BO3 Incorporation with SiO2-Alkyl-Silane@PDMS on Cotton Fabric

Limited robustness is a serious drawback for superhydrophobic coatings and degrades the performance of superhydrophobic surfaces in practical applications. Although fluororeagents have excellent durability for superhydrophobicity, their use has been restricted due to various health and environmental concerns. In this work, we describe a facile and efficient fabrication strategy for creating robust fluorine-free superhydrophobic composite coatings that are prepared by a simple dip-dry method, in which the H₃BO₃-incorporated SiO₂-alkyl-silane coatings are deposited on woven cotton fabric surfaces followed by polydimethylsiloxane modification. The coated surface shows a large water contact angle of 157.95 ± 2° and a small sliding hysteresis angle (SHA) of 3.8 ± 0.6°, demonstrating excellent superhydrophobicity. The coated fabric surface also exhibited robustness and durability, withstanding a tape-peeling test (under 48.05 kPa) for around 80 repetitions and sandpaper rubbing (loaded 100 g) for 40 cycles. Furthermore, the coated fabric surface displayed self-healing and oil-water separation capacities. The developed superhydrophobic coatings in this study are robust, environmentally benign, and easy to fabricate, showing promising applications in textile industries.