Near-monodisperse semiconductor quantum dots (QDs) have been synthesized by wet-chemical methods for fluorescent biological labels [1±5] and light-emitting devices.[6±8] Organic capping of QDs with surfactants can provide electron passivation and form a barrier against aggregation of crystallites. Typically, CdSe QDs capped with trioctylphosphine oxide (TOPO) have a quantum yield (QY) of~10 % at room temperature. [9] Coating of CdSe QDs with semiconductors of larger bandgaps (such as ZnS) has been shown to improve the photoluminescence QY to over 60 % by passivating the surface non-radiative recombination sites.[10] While the assynthesized QDs are stable in non-aqueous solution, their photophysical behavior is affected by the use of other solvents, ligands, and environments. Photobrightening and photodarkening may also be caused by the photoionization of QDs. [11] In order to improve the photostability of QDs, they need to be encapsulated within a rigid matrix. Silica is an ideal choice, and it can be applied as a coating using a versatile sol± gel process.[12]Recent advances in synthetic routes with less-toxic precursors (e.g., CdO) have made it possible to produce highly photoluminescent CdSe nanocrystals.[13±16] However, it is a real challenge to make the plain CdSe dots water-soluble while also achieving colloidal stability, photostability, efficient fluorescence, and low non-specific adsorption under aqueous biological conditions. Two main approaches exist in the literature for the design of water-soluble QDs. The first method involves an organic coating, using either polymers, [17,18] micelles, [5] or thiol groups such as mercaptoacetic acid (MAA) [2] and mercaptoundecanoic acid [19] as the linker molecules. The second method is based on the well-known silica chemistry developed for coating metal nanoparticles. [20±23] This strategy has a number of advantages over organic coating of nanoparticles. Silica acts as a robust, inert layer against the degradation of optical properties and imparts water solubility. Silica-coated (and silanized) QDs are very useful for biological applications since they allow for surface conjugation with amines, thiols, and carboxyl groups, which in turn would facilitate the linking of biomolecules such as biotin and avidin. Alivisatos and co-workers [1] first utilized the silanization approach to coat ZnS±CdSe QDs. Although this was carried out in a more-polar methanol solution using 3-mercaptopropyl trimethoxysilane (MPS), the procedure involved numerous steps and appeared to be complex to control. [24] Conversely, Rogach et al. encapsulated water-soluble CdTe QDs in 40±80 nm silica spheres through the Stöber method, but the emission spectrum was broadened with reduced intensity.[25] Using a reverse microemulsion, monodisperse silica particles can be synthesized.[26] Dyes encapsulated within silica shells showed enhanced luminescence and lifetimes due to improved chemical stability and photostability. [27] This communication describes a simple strategy for making plain CdSe QD...
Herein, we describe the synthesis of functional and multifunctional nanoparticles (NPs), derived from our recent work, for bioimaging and biosensing applications. The functionalized NPs involve quantum dots (QDs), magnetic particles (MPs) and noble metal NPs for the aforementioned applications. A diverse silica coating approaches (reverse microemulsion and thin silanization) are delineated for the design of water-soluble NPs. We also review the synthesis of silica-coated bifunctional NPs consisting of MPs and QDs for live cell imaging of human liver cancer cells (HepG2) and mouse fibroblast cells (NIH-3T3). Using silica coated NPs, various NPs that are functionalized with antibody, oligonucleotide, biotin and dextran are efficiently used for protein detection.
Nanosized hydroxyapatite (nHA) has been proposed as drug delivery vehicles because of its biocompatibility. While the possible risks of nHA inducing inflammation have been highlighted, the specific influence of varying nHA particle morphology is still unclear. In order to establish this understanding, nHA of four different shapes--needle (nHA-ND), plate (nHA-PL), sphere (nHA-SP) and rod (nHA-RD)--were synthesized. The particle effects with the concentration of 10-300 μg/mL on cytotoxicity, oxygen species generation, production of inflammatory cytokines (TNF-α and IL-6), particle-cell association and cellular uptake were evaluated on BEAS-2B and RAW264.7 cells. Results show that nHA-ND and nHA-PL induced the most significant cell death in BEAS-2B cultures compared to nHA-SP and nHA-RD. Necrosis-apoptosis assay by FITC Annexin V and propidium iodide (PI) staining revealed loss of the majority of BEAS-2B by necrosis. No significant cell death was recorded in RAW264.7 cultures exposed to any of the nHA groups. Correspondingly, no significant differences were observed in TNF-α level for RAW264.7 cells upon incubation with nHA of different shapes. In addition, nHA-RD exhibited a higher degree of particle-cell association and internalization in both BEAS-2B and RAW264.7 cells, compared to nHA-ND. The phenomena suggested that higher particle-cell association and increased cellular uptake of nHA need not result in increased cytotoxicity, indicating the importance of particle shape on cytotoxicity. Specifically, needle- and plate-shaped nHA induced the most significant cell-specific cytotoxicity and IL-6 expression but showed the least particle-cell association. Taken collectively, we demonstrated the shape-dependent effects of nHA on cytotoxicity, inflammatory cytokine expression and particle-cell association.
The bioanode is the defining feature of microbial fuel cell (MFC) technology and often limits its performance. In the current work, we report the engineering of a novel hierarchically porous architecture as an efficient bioanode, consisting of biocompatible chitosan and vacuum-stripped graphene (CHI/VSG). With the hierarchical pores and unique VSG, an optimized bioanode delivered a remarkable maximum power density of 1530 mW m(-2) in a mediator-less MFC, 78 times higher than a carbon cloth anode.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.