Bioinspired, direct synthesis of aqueous CdSe quantum dots for high-sensitive copper(II) ion detection

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.

Application of Nanotechnology in Analysis and Removal of Heavy Metals in Food and Water Resources

Toxic heavy metal contamination in food and water from environmental pollution is a significant public health issue. Heavy metals do not biodegrade easily yet can be enriched hundreds of times by biological magnification, where toxic substances move up the food chain and eventually enter the human body. Nanotechnology as an emerging field has provided significant improvement in heavy metal analysis and removal from complex matrices. Various techniques have been adapted based on nanomaterials for heavy metal analysis, such as electrochemical, colorimetric, fluorescent, and biosensing technology. Multiple categories of nanomaterials have been utilized for heavy metal removal, such as metal oxide nanoparticles, magnetic nanoparticles, graphene and derivatives, and carbon nanotubes. Nanotechnology-based heavy metal analysis and removal from food and water resources has the advantages of wide linear range, low detection and quantification limits, high sensitivity, and good selectivity. There is a need for easy and safe field application of nanomaterial-based approaches.

Mimicking biological process to detect alkaline phosphatase activity using the vitamin B6 cofactor conjugated bovine serum albumin capped CdS quantum dots

This manuscript presents a novel bioanalytical approach for the selective ratiometric fluorescent sensing of enzymatic activity of the alkaline phosphatase (ALP) in the biological samples. The probe was designed by conjugating the pyridoxal 5'-phosphate (PLP) over the surface of bovine serum albumin (BSA) stabilized CdS quantum dots (QDs) through the interaction of free amine present in BSA with the aldehyde group of PLP. The conjugation of PLP quenched the emission of QDs. Upon addition of the ALP, the emission of QDs was restored due to the dephosphorylation and the conversion of the functionalized PLP in to pyridoxal. With this probe, the ALP activity can be detected down to 0.05 U/L and also successfully applied for the detection of ALP activity in biological samples such as human serum and plasma.

Temperature-Induced Denaturation of BSA Protein Molecules for Improved Surface Passivation Coatings

Bovine serum albumin (BSA) is the most widely used protein for surface passivation applications, although it has relatively weak, nonsticky interactions with hydrophilic surfaces such as silica-based materials. Herein, we report a simple and versatile method to increase the stickiness of BSA protein molecules adsorbing onto silica surfaces, resulting in up to a 10-fold improvement in blocking efficiency against serum biofouling. Circular dichroism spectroscopy, dynamic light scattering, and nanoparticle tracking analysis showed that temperature-induced denaturation of BSA proteins in bulk solution resulted in irreversible unfolding and protein oligomerization, thereby converting weakly adhesive protein monomers into a more adhesive oligomeric form. The heat-treated, denatured BSA oligomers remained stable after cooling. Room-temperature quartz crystal microbalance-dissipation and localized surface plasmon resonance experiments revealed that denatured BSA oligomers adsorbed more quickly and in larger mass quantities onto silica surfaces than native BSA monomers. We also determined that the larger surface contact area of denatured BSA oligomers is an important factor contributing to their more adhesive character. Importantly, denatured BSA oligomers were a superior passivating agent to inhibit biofouling on silica surfaces and also improved Western blot application performance. Taken together, the findings demonstrate how temperature-induced denaturation of BSA protein molecules can lead to improved protein-based coatings for surface passivation applications.

Protein/peptide-templated biomimetic synthesis of inorganic nanoparticles for biomedical applications

Currently, protein/peptide-based biomimetic mineralization has been demonstrated to be an efficient and promising strategy for synthesis of inorganic/metal nanoparticles (NPs) for bioapplications.

Fluorescent nanoprobes for sensing and imaging of metal ions: recent advances and future perspectives

Recent advances in nanoscale science and technology have generated nanomaterials with unique optical properties. Over the past decade, numerous fluorescent nanoprobes have been developed for highly sensitive and selective sensing and imaging of metal ions, both in vitro and in vivo. In this review, we provide an overview of the recent development of the design and optical properties of the different classes of fluorescent nanoprobes based on noble metal nanomaterials, upconversion nanoparticles, semiconductor quantum dots, and carbon-based nanomaterials. We further detail their application in the detection and quantification of metal ions for environmental monitoring, food safety, medical diagnostics, as well as their use in biomedical imaging in living cells and animals.

Thiosemicarbazide chemical functionalized carbon dots as a fluorescent nanosensor for sensing Cu2+and intracellular imaging

Synthesis procedures for the CDs-based nanosensor and schematic diagram of Cu²⁺detection.

Glucose oxidase-directed, instant synthesis of Mn-doped ZnS quantum dots in neutral media with retained enzymatic activity: mechanistic study and biosensing application

Protein-directed synthesis of quantum dots (QDs) is a "greener" alternative to the current high-temperature and aqueous synthetic protocols, which provide water-soluble, biocompatible protein-functionalized QDs in one-pot. However, the protein activity in such synthetic schemes is a critical issue, since the synthetic conditions (for instance, high pH of the precursors, long time of synthesis, and disruption of disulfide bonds) are not suitable for retaining the activity (especially for enzymes). Herein, we present a facile and instant glucose oxidase (GOD)-directed strategy for the preparation of highly luminescent, phosphorescent Mn-doped ZnS (Mn-ZnS) QDs in one-step at room temperature and in neutral aqueous media. With such mild synthetic conditions, the enzymatic activity of GOD was totally retained. Furthermore, we also carried out GOD-directed synthesis of QDs with several other conditions that are reported in the literature. It turned out that the GOD enzymatic activity under these synthetic conditions was lower than that of the proposed protocol, indicating that mild synthetic conditions are the prerequisite for retaining the enzymatic activity. Importantly, the as-prepared GOD-mediated Mn-ZnS QDs exhibited high photostability, high salt tolerance and colloidal stability, and can be stored for months at 4 °C or 25 °C without changing their phosphorescent intensity and enzymatic activity. Via selective chemical modification, the exact functional groups (amino acid residues) of GOD in directing the synthesis of Mn-ZnS QDs were studied in detail. It turned out to be imidazole in histidine residues but not thiol in cysteine residues that directed the formation of Mn-ZnS QDs, and this was further confirmed with several other proteins for synthesis of Mn-ZnS QDs. The as-prepared GOD-capped Mn-ZnS QDs were employed as phosphorescent probes for background-free sensing of glucose in serum samples.

Fluorescent metal ion chemosensors via cation exchange reactions of complexes, quantum dots, and metal–organic frameworks

Overview of a new paradigm in the design of fluorescent chemosensors for detecting metal ions via cation exchange reactions of complexes, quantum dots, and metal–organic frameworks.