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Smart Biomarker-Coated PbS Quantum Dots for Deeper Near-Infrared Fluorescence Imaging in the Second Optical Window
Published in Lingyan Shi, Robert R. Alfano, Deep Imaging in Tissue and Biomedical Materials, 2017
As the highly fluorescent PbS/CdS QDs are synthesized using oleylamine as a protecting reagent, the surface of PbS/CdS QDs is hydrophobic and they are insoluble in water. To use the PbS/CdS QDs in aqueous solution, the QDs have to be modified by surface coating. For deep-tissue imaging, small-sized fluorescent QD probes (<ca. 10 nm) are desirable to promote the circulation of probes in tissues and their renal clearance [63]. So far, two approaches have been used for the chemical modification of QD surface to be hydrophilic. One method is the encapsulation of QDs with amphiphilic polymers [64]. In principle, this method maintains the fluorescence brightness of the initial QDs, because the QD surface does not change after the encapsulation. However, the hydrodynamic size of the resulting QDs increases depending on the molecular weights of the amphiphilic polymers. Another method is the ligand-exchange using small molecules such as hydrophilic thiol compounds [65]. In this case, the size of QDs is not significantly changed when using the thiol compounds with small molecular weights. However, the ligand-exchange method often results in significant decrease in the fluorescence brightness and colloidal stability of QDs [65].
Nanoemulsion Formulations for Tumor-Targeted Delivery
Published in Mansoor M. Amiji, Nanotechnology for Cancer Therapy, 2006
Sandip B. Tiwari, Mansoor M. Amiji
Similar to particle size, surface charge of the nanoemulsion droplets has marked effect on the stability of the emulsion system and the droplets’ in vivo disposition and clearance. Conventionally, the surface charge on the emulsion droplets has been expressed in terms of zeta potential (ζ). As the emulsion droplets are a result of interfacial phenomenon brought out by surface active agents, their zeta potential is dependent on the extent of ionization of these surface active agents. According to DLVO electrostatic theory, the stability of the colloid is a balance between the attractive van der Waals’ forces and the electrical repulsion because of the net surface charge.20 If the zeta potential falls below a certain level, the emulsion droplets will aggregate as a result of the attractive forces. Conversely, a high zeta potential (either positive or negative), typically more than 30 mV, maintains a stable system.8,15,19 The zeta potential of the nanoemulsion droplets is routinely measured using a Zetasizer (Malvern Instruments, U.K.) or the ZetaPlus instrument (Brookhaven Instruments Corporation, Holtsville, NY, U.S.A.). The zeta potential of the commercial nanoemulsions used for total parenteral nutrition is reported to be around −40 to −50 mV at pH 7.19 The net negative surface charge is thought to be attributed to the anionic components of the emulsions, mainly the phospholipids.21 One can impart positive charge to the nanoemulsions as well using cationic lipids [e.g., SA,22–24 oleylamine,25 2,3-dioleoyloxypropyl-1-trimethylammonium bromide, DOTMA,26 dimethylaminoethane carbamoyl cholesterol (DC-cholesterol)]27, polymers (e.g., chitosan), 28,29 and cationic surfactants (e.g., cetyltrimethylammonium bromide).30
Gold Nanomaterials at Work in Biomedicine *
Published in Valerio Voliani, Nanomaterials and Neoplasms, 2021
Xuan Yang, Miaoxin Yang, Pang Bo, Madeline Vara, Younan Xia
Recently, there has been an emerging trend to incorporate the radionuclide directly into the lattice of Au nanostructures for improved labeling stability. To this end, 64Cu atoms were successfully incorporated into the lattice of Au nanoparticles to enable the particles with PET imaging capabilities. Specifically, Liu and coworkers synthesized CuAu alloyed nanoparticles of 9.4 ± 1.2 nm in diameter by directly reducing copper(II) acetylacetonate (Cu(acac)2), 64CuCl2, and HAuCl4 in the presence of oleylamine [574]. The same group also reported the synthesis of much smaller CuAu nanoparticles with an average diameter of 2.5 ± 0.8 nm [575]. Compared to their larger counterparts, when coated with PEG (MW ~ 350 Da) the small particles showed superior clearance properties, with 36.2% and 40.8% of the injected dose cleared from feces and urine, respectively, 48 h postinjection. This demonstration helps address the clearance issue faced by many nanomaterials, demonstrating that smaller particles are better suited for in vivo application. However, the involvement of radioactive 64CuCl2 makes it difficult to synthesize Au nanostructures with other shapes. An alternative approach is to add the radioactive 64Cu by deposition after the Au nanostructures have been synthesized [573, 576]. As demonstrated by Chen and coworkers, 64Cu could be deposited on the surface of various types of PEG-stabilized Au nanostructures to enable their use for PET imaging. In a typical synthesis, a trace amount of 64Cu was introduced into a suspension of PEG-stabilized Au nanostructures and reduced by hydrazine in the presence of poly(acrylic acid). To compare with a conventional labeling technique based on DOTA, both 64Cu-coated and 64Cu-chelated Au nanoparticles with a diameter of 80 nm were introduced into a mouse model and the signals from bladder and urine were evaluated. Negligible signals were detected in both bladder and urine for the mice injected with 64Cu-coated Au nanoparticles, whereas a significant signal was detected for their counterparts using the conventional chelating technique. These results confirm the possible release of 64Cu2+ ions or 64Cu-chelated polymer chains from the nanoparticles labeled using the chelating method. The authors then demonstrated the capability to modify the surface of Au nanorods (8.0 nm × 25.1 nm) and coat them with 64Cu for tumor targeting and imaging-guided photothermal therapy.
Pronounced capping effect of olaminosomes as nanostructured platforms in ocular candidiasis management
Published in Drug Delivery, 2022
Sadek Ahmed, Maha M. Amin, Sarah Mohamed El-Korany, Sinar Sayed
Recently capping agents are used in frequent to control the growth, prevent aggregation and maintain the physicochemical characteristics in a defined manner (Niu & Li, 2014). Capping agents are amphoteric molecules that are composed of hydrophilic head and lipophilic tail, hence they can boost the compatibility and functionality with alternative phase. There are many capping agents that are used in pharmaceutical industry such as surfactants, small ligands, polymers, dendrimers, cyclodextrins, and polysaccharides. These capping agents succeed to provoke delicate modifications in nanoparticles causing remarkable therapeutic effects (Radini et al., 2018). Therefore, the selection of appropriate capping agent is fundamental in stabilizing the developed nanosystem and regulating their uptake into living cells and the environment. Capping agent alter the surface chemistry and size distribution of the formulated nanoparticles (Javed et al., 2020). In this study, oleylamine was selected as capping agent as it has the capability to form a carboxylate derivatives with the carboxylic group of oleic acid (Safo et al., 2019). Oleylamine is a long-chain primary alkyl amine that utilizes its amine group (NH2-) for interaction. As, amine group has greater affinity for protons resulted from the lone pair of electrons it owns which it simply donates to H. Oleylamine has a high proton that allows it to interact easily (Mbewana-Ntshanka et al., 2020).
A comprehensive review on recent nanosystems for enhancing antifungal activity of fenticonazole nitrate from different routes of administration
Published in Drug Delivery, 2023
Sadek Ahmed, Maha M. Amin, Sinar Sayed
Regarding ocular nanosystems, olaminosomes represent novel nanocarriers that are chiefly composed of oleic acid, oleylamine and surfactant (Abd-Elsalam & ElKasabgy, 2019). Oleic acid is an unsaturated free fatty acid that is widely used in nanosystems formulation as a result of its safety, biodegradability and biocompatibility. Oleylamine is a long-chain amino compound with pronounced capping properties that extremely affect the stability, permeability and activity (Safo et al., 2019). Surfactants are extensively used in nanosystems as they optimize their surface and penetration properties (Abd-Elsalam & Ibrahim, 2021). Span 80 was used in O-OLN and O-NV.