Iron Oxide Nanoparticles: A Review on the Province of Its Compounds,Properties and Biological Applications

Materials science and technology, with the advent of nanotechnology, has brought about innumerable nanomaterials and multi-functional materials, with intriguing yet profound properties, into the scientific realm. Even a minor functionalization of a nanomaterial brings about vast changes in its properties that could be potentially utilized in various applications, particularly for biological applications, as one of the primary needs at present is for point-of-care devices that can provide swifter, accurate, reliable, and reproducible results for the detection of various physiological conditions, or as elements that could increase the resolution of current bio-imaging procedures. In this regard, iron oxide nanoparticles, a major class of metal oxide nanoparticles, have been sweepingly synthesized, characterized, and studied for their essential properties; there are 14 polymorphs that have been reported so far in the literature. With such a background, this review’s primary focus is the discussion of the different synthesis methods along with their structural, optical, magnetic, rheological and phase transformation properties. Subsequently, the review has been extrapolated to summarize the effective use of these nanoparticles as contrast agents in bio-imaging, therapeutic agents making use of its immune-toxicity and subsequent usage in hyperthermia for the treatment of cancer, electron transfer agents in copious electrochemical based enzymatic or non-enzymatic biosensors and bactericidal coatings over biomaterials to reduce the biofilm formation significantly.     

Label-free plasmonic biosensors for point-of-care diagnostics: a review

Introduction: Optical biosensors, particularly those based on nanoplasmonics technology, have emerged in recent decades as a potential solution for disease diagnostics and therapy follow-up at the point-of-care (POC). These biosensor platforms could overcome some of the challenges faced in conventional diagnosis techniques offering label-free assays with immediate results and employing small and user-friendly devices.

Areas covered: In this review, we will provide a critical overview of the recent advances in the development of nanoplasmonic biosensors for the POC diagnostics. We focus on those systems with demonstrated capabilities for integration in portable platforms, highlighting some of the most relevant diagnostics applications targeting proteins, nucleic acids, and cells as disease biomarkers.

Expert commentary: Despite the attractive features of label-free nanoplasmonic sensors in terms of miniaturization and analytical robustness, the route toward an effective clinical implementation involves the integration of fully automated microfluidic systems for sample processing and analysis, and the optimization of surface biofunctionalization procedures. Additionally, the development of multiplexed sensors for high-throughput analysis and including specific neoantigens and novel biomarkers in detection panels will provide the means for delivering a powerful analytical technology for an accurate and improved medical diagnosis.     

Hierarchical Self‐Assembly of Peptides and its Applications in Bionanotechnology

Self‐assembled structures obtained from organic molecules have shown great potential for applications in a wide range of domains. In this context, short peptides prove to be a particularly versatile class of organic building blocks for self‐assembled materials. These species afford the biocompatibility and polymorphic richness typical of proteins while allowing synthetic availability and robustness typical of smaller molecules. At the nano‐to‐mesoscale, the architectures obtained from peptide units exhibit stability and a large variety of morphologies, the most common of which are nanotubes, nanoribbons, and nanowires. This review describes the formation of peptide‐based self‐assembled structures triggered by different stimuli (e.g., ionic strength, pH, and polarity), and the interactions that drive the assembling processes. It is surveyed how judicious molecular design is exploited to impart favourable assembling properties to afford systems with desired characteristics. A large body of literature provides the experimental and in silico data to predict self‐assembly in a given peptide system and obtain different supramolecular organizations for applications in a wide range of fields, from transport to sensing, from catalysis to drug delivery and tissue regeneration.     

Monitoring single-cell bioenergetics via the coarsening of emulsion droplets

Microorganisms are widely used to generate valuable products, and their efficiency is a major industrial focus. Bioreactors are typically composed of billions of cells, and available measurements only reflect the overall performance of the population. However, cells do not equally contribute, and process optimization would therefore benefit from monitoring this intrapopulation diversity. Such monitoring has so far remained difficult because of the inability to probe concentration changes at the single-cell level. Here, we unlock this limitation by taking advantage of the osmotically driven water flux between a droplet containing a living cell toward surrounding empty droplets, within a concentrated inverse emulsion. With proper formulation, excreted products are far more soluble within the continuous hydrophobic phase compared to initial nutrients (carbohydrates and salts). Fast diffusion of products induces an osmotic mismatch, which further relaxes due to slower diffusion of water through hydrophobic interfaces. By measuring droplet volume variations, we can deduce the metabolic activity down to isolated single cells. As a proof of concept, we present the first direct measurement of the maintenance energy of individual yeast cells. This method does not require any added probes and can in principle apply to any osmotically sensitive bioactivity, opening new routes for screening, and sorting large libraries of microorganisms and biomolecules.     

环介导等温扩增技术检测方法的研究进展

环介导等温扩增技术是一种可用于临床诊断的快速检测方法,可用于检测病毒、细菌、寄生虫等多种病原体。经不断完善,现已在临床检测过程中发挥重要作用。可用显色试剂对反应结果实现可视化,即结果的即时显示,无需后续验证。但是,无论是荧光染料还是显色指示剂,对反应过程都会产生或多或少的影响,目前研究表明羟基萘酚蓝是最好的显色试剂。同时,人们发现电化学技术也可以应用于此,使检测反应更快,操作更加简单。生物传感器可以对多种反应产物进行同步检测,而微流控芯片技术更是方便携带,有望成为实时检测技术的理想载体。     

Direct Electrochemistry and Electrocatalysis of Horseradish Peroxidase Immobilized in a DNA/Chitosan-Fe3O4 Magnetic Nanoparticle Bio-Complex Film

A DNA/chitosan-Fe₃O₄ magnetic nanoparticle bio-complex film was constructed for the immobilization of horseradish peroxidase (HRP) on a glassy carbon electrode. HRP was simply mixed with DNA, chitosan and Fe₃O₄ nanoparticles, and then applied to the electrode surface to form an enzyme-incorporated polyion complex film. Scanning electron microscopy (SEM) was used to study the surface features of DNA/chitosan/Fe₃O₄/HRP layer. The results of electrochemical impedance spectroscopy (EIS) show that Fe₃O₄ and enzyme were successfully immobilized on the electrode surface by the DNA/chitosan bio-polyion complex membrane. Direct electron transfer (DET) and bioelectrocatalysis of HRP in the DNA/chitosan/Fe₃O₄ film were investigated by cyclic voltammetry (CV) and constant potential amperometry. The HRP-immobilized electrode was found to undergo DET and exhibited a fast electron transfer rate constant of 3.7 s⁻¹. The CV results showed that the modified electrode gave rise to well-defined peaks in phosphate buffer, corresponding to the electrochemical redox reaction between HRP(Fe^(III)) and HRP(Fe^(II)). The obtained electrode also displayed an electrocatalytic reduction behavior towards H₂O₂. The resulting DNA/chitosan/Fe₃O₄/HRP/glassy carbon electrode (GCE) shows a high sensitivity (20.8 A·cm⁻²·M⁻¹) toward H₂O₂. A linear response to H₂O₂ measurement was obtained over the range from 2 μM to 100 μM (R² = 0.99) and an amperometric detection limit of 1 μM (S/N = 3). The apparent Michaelis-Menten constant of HRP immobilized on the electrode was 0.28 mM. Furthermore, the electrode exhibits both good operational stability and storage stability.     

Synthesis of Water-Dispersed Ferrecene/Phenylboronic Acid-Modified Bifunctional Gold Nanoparticles and the Application in Biosensing

Phenylboronic acids can form tight covalent bonds with diol-containing biomolecules. In this work, water-dispersed bifunctional gold nanoparticles (AuNPs) modified with ferrecene (Fc)-derivatized peptides and 4-mercaptophenylboronic acids (MBA) (denoted as Fc–MBA–AuNPs) were synthesized and characterized by UV/vis spectrometry and transmission electron microscopy. To demonstrate the application and the analytical merits of the nanoparticles in biosensing, glycoprotein avidin was tested as a model analyte. Specifically, avidin was captured by the biotin-covered gold electrode via the strong biotin-avidin interaction. Then, Fc–MBA–AuNPs were attached by the captured avidin through the formation of tight covalent bonds between the boronic acid moieties of Fc–MBA–AuNPs and the oligosaccharides of avidin. As a result, a detection limit of 0.2 pM was achieved. We believe that the bifunctional nanoparticles would found many applications in amplified detection of diol-containing species by rational design of the surface chemistry of electrode.     

Technologies of time: women’s practices of trying to conceive with ovulation biosensing

Ovulation biosensors are devices worn on or used with the body, which can help women detect ovulation. The manufacturers of such devices claim that if women know when they ovulate, couples can arrange heterosexual intercourse during this time, and thus increase their chances of conceiving. Within the contemporary UK context, in which becoming pregnant is presented in the popular media, and in medical discourses, as more difficult for women in their thirties and forties, manufacturers’ claims are attractive for those trying to conceive. Yet few sociological studies have examined women’s practices of ovulation biosensing. Drawing on women’s accounts of tracking ovulation, this paper explores how such practices fit into their trajectories of trying to conceive. It examines why ovulation biosensing seemingly becomes helpful, relevant or important during this time. Ovulation biosensors, it argues, alter the landscape of trying to become pregnant by introducing new stages and materialities which seemingly place women closer to conception. Women engage in ovulation biosensing, not only to help them become pregnant, but also as a way to manage the complexities of fertility and the uncertainties of becoming pregnant in contemporary society.     

Optical biodetection of cadmium and lead ions in water

A three layer waveguiding silicon dioxide (SiO₂)/silicon nitride (Si₃N₄)/SiO₂ structure on silicon substrate was proposed as an optically efficient biosensor for calibration of heavy metal ions in drinking water. The catalytic activities of urease and acetylcholine esterase (AchE) were inhibited by the presence of cadmium (Cd²⁺) and lead (Pb²⁺) ions. The detection limit as low as 1 ppb was achieved by employing the technique of total reflection at the interface between the Si₃N₄ core and composite polyelectrolyte self-assembled (PESA) membranes containing cyclotetrachromotropylene (CTCT) as an indicator.