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Recently, zinc oxide nanoparticles (ZnONPs) are gaining much interest of nanobiotechnologists due to their profound biomedical applications. ZnONPs are used as antibacterial agents, which cause both gram-positive and negative bacterial cell death through the generation of reactive free radicals as well as membrane rupture. ZnONPs show excellent antioxidant properties in normal mammalian cells via the scavenging of reactive free radicals and up-regulation of antioxidant enzyme activities. Besides, it also shows hypoglycaemic effect in diabetic animals via pancreatic β-cells mediated increased insulin secretion and glucose uptake by liver, skeletal muscles and adipose tissues. Among the other potential applications, ZnONPs-induced bone and soft-tissue regeneration open a new horizon in the field of tissue engineering. Here, first we reviewed the complete synthesis routes of ZnONPs by physical, chemical, and biological pathways as well as outlined the advantages and disadvantages of the techniques. Further, we discussed the several important aspects of physicochemical analysis of ZnONPs. Additionally, we extensively reviewed the important biomedical applications of ZnONPs as antibacterial, antioxidant, and antidiabetic agents, and in the field of tissue engineering with special emphasis on their mechanisms of actions. Furthermore, the future perspectives of the ZnONPs are also discussed. [Display omitted] • Zinc oxide nanoparticles emerge as excellent candidate in the field of biomedical research. • They can be synthesized by physical, chemical and biological methods. • They can be used as excellent antibacterial, antioxidant, antidiabetic and tissue regenerating agents. • This review summarises the progress of research on synthesis and biomedical applications of zinc oxide nanoparticles. [ABSTRACT FROM AUTHOR]

In recent years, zinc oxide nanoparticles (ZnONPs) emerged as an excellent candidate in the field of optical, electrical, food packaging and particularly in biomedical research. ZnONPs show cancer cell specific toxicity via the pH-dependent (low pH) dissolution into Zn2+ ions, which generate reactive oxygen species and induce cytotoxicity in cancer cells. Further, ZnONPs have also been used as an effective carrier for the targeted delivery of several anticancer drugs into tumor cells. The increasing focus on ZnONPs resulted in the development of various synthesis approaches including chemical, pHysical, and green or biological for the manufacturing of ZnONPs. In this article, at first we have discussed the various synthesis methods of ZnONPs and secondly its biomedical applications. We have extensively reviewed the anticancer mechanism of ZnONPs on different types of cancers considering its size, shape and surface charge dependent cytotoxicity. Photoirradiation with UV light or NIR laser further increase its anticancer activity via synergistic chemo-photodynamic effect. The drug delivery applications of ZnONPs with special emphasis on drug loading mechanism, stimuli-responsive controlled release and therapeutic effects have also been discussed in this review. Finally, its side effects to vital body organs with mechanism via different exposure routes, the future direction of the ZnONPs research and application are also discussed. Unlabelled Image [ABSTRACT FROM AUTHOR]

Nanoparticles (NPs) are widely utilized as an effective carrier for naturally occurring biologically active hydrophobic molecules with a potential to enhance antioxidant and antibacterial activities. Here, a positively charged amine-functionalized ceria nanoparticles (CeO2-NH2NPs) were prepared first, and then a natural flavonoid, morin was adsorbed on the surface of NPs via metal–ligand coordination to form a nanohybrid (morin-CeO2-NH2). The CeO2-NH2NPs displayed almost spherical shape with size of around 3–4 nm, along with the presence of Ce, O, N, C, and Si. The NPs showed ~ 10% drug (morin) loading content, and a sustained release pattern of morin under physiological conditions. The nanohybrids showed excellent free radical (DPPH, superoxide, and hydrogen peroxide) scavenging properties in both cell-free systems as well as in intracellular conditions. Cytotoxicity assessment revealed that the nanohybrids were slightly toxic up to the concentration of 50 μg/mL in normal human kidney epithelial cells. Further, the nanohybrids showed a significant growth inhibition against the tested Gram-negative as well as Gram-positive bacteria due to the production of excessive reactive oxygen species (ROS), DNA degradation, and membrane damage. However, those in vitro assays showed that the nanohybrid exhibited the maximum effect in imparting the antioxidant and antibacterial activity among all the treatment groups. All these results highlighted that the nanoceria-mediated drug delivery systems could help to increase the antioxidant and antibacterial potential of morin. [ABSTRACT FROM AUTHOR]

In the current study, carbon dots/cerium oxide (CDs/CeO 2) nanocomposites-modified screen printed carbon electrode, SPCE (CDs/CeO 2 /SPCE) was developed for the highly sensitive and selective detection of doxorubicin (DOX), an anticancer drug. Here, firstly we have synthesized cerium oxide nanoparticles (CeO 2 NPs) from ammonium cerium nitrate and urea by simple refluxing, and then CDs were synthesized by using taurine (an essential amino acid) via thermal decomposition method. After that CDs/CeO 2 nanocomposites have been synthesized with different wt% of CDs (0.5–5 wt%) via a facile hydrothermal method. The synthesized nanocomposites exhibited higher efficiency towards the electrochemical detection of DOX as compared to bare CeO 2 NPs and CDs by promoting electron transfer reaction at SPCE surface with increasing amount of CDs. The 5 wt% nanocomposite (CDs-5.0/CeO 2) showed the highest oxidation response towards DOX (20 μM) at an optimized pH of 5. The cyclic voltammograms revealed that CDs-5.0/CeO 2 /SPCE sensing system exhibited a linear response (correlation coefficient, R2 = 0.98) between oxidation peak current and DOX concentration in the range of 0.2–20 μM, with a low detection limit of 0.09 μM. Moreover, the modified CDs-5.0/CeO 2 /SPCE sensor exhibited superior selectivity towards DOX in the presence of common interferents. This work demonstrated that the novel CDs/CeO 2 /SPCE sensor can be effectively applied to detect DOX in pharmaceutical samples or in biological fluids. [Display omitted] • A novel CDs/CeO 2 nanocomposite was synthesized via a facile hydrothermal method. • The nanocomposite was characterized via HRTEM, XPS, XRD, FTIR, and Raman analysis. • The CDs/CeO 2 /SPCE could detect DOX with detection limit of 0.09 μM. • The CDs/CeO 2 /SPCE sensing system exhibited superior selectivity towards DOX. [ABSTRACT FROM AUTHOR]

Carbon dots (CDs) are the most promising candidates of the carbon family with superior properties like ultra-small size, high aqueous solubility, low cytotoxicity, and inherent photoluminescence which makes them suitable for diverse biomedical applications. Methods have been developed to enhance their applications. Doping/surface passivation of CDs improves their physicochemical properties, visible light absorption probability, and quantum yield by controlling their size, morphology, structure, and band-gap energy. Recently, metal-doped CDs have emerged as an important class of nanomaterials with numerous biomedical applications. Additionally, the conjugation of CDs with semiconductor metal-oxide nanoparticles (NPs) enhances their free radical production rates under visible light irradiation. Conjugation of fluorescent CDs with magnetic NPs leads to the development of multimodal imaging platforms. Similarly, ternary conjugates composed of fluorescent CDs, near-infrared (NIR) responsive, and magnetic NPs are useful for multi-modal imaging-guided, and NIR-responsive synergistic chemo-phototherapy. However, no comprehensive review is published yet which covers metal-doped and hybrid CDs. Therefore, herein we provide detailed information about their synthesis and important biomedical applications. Firstly, we have covered various synthesis methods for CD conjugation including the critical analysis of the effects of the reaction conditions and doping/conjugation on the structure and properties of the CDs. Then we have extensively reviewed their biomedical applications as antimicrobial, antioxidant, and bioimaging agents, and in the field of cancer phototherapy with special emphasis on their mechanisms of actions. Finally, the future directions of research and the applications of the metal-doped and hybrid CDs have been discussed. We believe that this review article will enrich the understanding of different synthetic routes of CD-nanocomposites and their biomedical applications. Unlabelled Image • Metal doped and hybrid carbon dots emerge as an excellent candidate in the field of biomedical research. • They can be synthesized by solvothermal/hydrothermal, reduction, microwave and sonochemical methods. • They can be used as excellent antibacterial, antifungal, antioxidant and bioimaging agents. • They show excellent photothermal and photodynamic therapy effects. • This review summarises the research on the synthesis and biomedical applications of metal doped and hybrid carbon dots. [ABSTRACT FROM AUTHOR]

Here, first we have synthesized carbon dots (CDs) from red Korean ginseng, and modified further with folic acid (FA) for the targeted and controlled delivery of a natual flavonoid, rutin (RUT). FA conjugated and morin loaded CDs (FA-CDs-RUT) displayed size ~70 nm, drug loading content of 14.5 % and a pH-dependent drug release behaviour. Human breast cancer MCF-7 cells were taken for checking the anticancer activities of FA-CDs-RUT. The nanohybrids (FA-CDs-RUT) showed a dose-dependent (10–50 μg/mL) cytotoxicity in MCF-7 cells and caused apoptotic cell death by inducing oxidative stress and mitochondrial damage. Besides, anti-migratory role of FA-CDs-RUT was also observed. The in vivo intravenous (i.v.) administration of FA-CDs-RUT nanohybrid was found to effectively decrease the tumor growth in tumor-bearing mice as compared with bare rutin and CDs. Interestingly, none of the nanoformulations and bare rutin caused any significant alterations in blood biochemical parameters. The enhanced anticancer activity of FA-CDs-RUT is thought to be due to combinatorial anticancer effects of CDs and rutin. We also performed docking study of rutin with Bcl-2 to gain insights into possible pathways of cell growth regulation. Molecular docking study shown that rutin binds with Bcl-2 with binding affinity of −7.6 k Cal/mol. Together, this study provides insight into the usability of FA-CDs-RUT to treat breast cancer with their mechanisms of action. [Display omitted] • A novel FA-conjugated carbon dots (FA-CDs) were synthesized. • The FA-CDs were loaded with rutin (a flavonoid) to form FA-CDs-RUT. • FA-CDs-RUT exhibited pH-dependent drug release property. • FA-CDs-RUT showed significant anticancer effect both in vitro and in vivo. • FA-CDs-RUT did not exhibit any systemic toxicity. [ABSTRACT FROM AUTHOR]

Here, we have prepared a new water-soluble carbon dots (CDs) from a conditionally essential amino acid, "taurine" via thermal decomposition method. The as-synthesized CDs displayed oval/spherical shape with size less than 10 nm. The existence of nitrogen, sulphur and oxygen in the CD was confirmed by x-ray photoelectron spectroscopy. The CDs exhibited a quantum yield value of 7.2% and excitation dependent fluorescence (FL) emission spectra, and they were used for sensitive and selective detection of Cu2+ ions with a limit of detection of 0.62 μM. Furthermore, the aqueous solution of the CDs showed significant stability up to 90 days with very negligible effect on their fluorescence intensity under high salt concentration. After that we have prepared the nanohybrid (CDs-CeO 2) consisting of CDs (0.025–0.3 wt %) and CeO 2 as a visible light photocatalyst for the removal of methyl orange (MO) dye from water. The nanohybrid consisting of 0.1 wt % CDs displayed highest (66%) degradation towards MO at pH ∼ 6 under visible light irradiation for 5 h. However, 85% and 100% MO degradation were observed in strongly basic (pH ∼ 11) and acidic (pH ∼ 3) medium respectively. The enhanced photodegradation ability of the 0.1 wt % CDs-CeO 2 is attributed to the highest visible light absorbing capacity and lowest band gap energy. Superoxide radicals (O 2 −.) were found to play the primary role in the photocatalysis process within the pH range of 3–6. Besides, good stability and reusability of the nanocatalysts were also confirmed. Taken together our synthesized CDs and its nanohybrid with CeO 2 can be considered as a promising candidate for sensing and photocatalytic activities. • At first a novel green carbon dots (CDs) were synthesized from taurine. • Then CDs-CeO 2 nanohybrid was synthesized. • CDs were used for sensitive and selective detection of Cu2+ ions. • The nanohybrid displayed 66% degradation towards methyl orange at the neutral pH under visible light irradiation for 5 h. • 100% methyl orange degradation was observed in an acidic pH of 3 within 25 min. [ABSTRACT FROM AUTHOR]