Abdul Mumin

Multifunctional nanoparticles for rapid bacterial capture, detection, and decontamination

Fluorescent magnetic nanoparticles (FMNPs) with a core–shell structure are synthesized through a one-pot chemical method followed by the bioconjugation of gentamycin (Gm). The average diameter of the FMNPs is estimated to be 65 ± 8 nm. The results of transmission electron microscopy (TEM), X-ray absorption near edge structure spectroscopy (XANES), and fluorospectrometry indicate that the FMNPs consist of a Fe3O4 core and a fluorescent silica (SiO2) shell. The FMNPs show typical superparamagnetic properties with a blocking temperature (TB) of 120 K. We demonstrate that gentamicin (Gm)-bioconjugated FMNPs can capture gram-negative bacteria, i.e. E. coli, (1 × 107 CFU mL−1 from 10 mL of solution) within 20 min. TEM micrographs clearly show that the Gm-FMNPs disrupt the cell wall of E. coli prior to the lysis of E. coli as the interaction time (t) increases; whereas FMNPs without Gm are inert towards E. coli. In addition, the Gm-FMNPs are able to detect diluted E. coli cells at a concentration as low as 1 × 103 CFU mL−1, which is revealed by a slight red-shift in fluorescent emissions from 517 nm to 528 nm along with a dramatic decrease in intensity. The Gm-conjugated FMNPs can be a multifunctional platform for simultaneous rapid capture, sensitive detection, and decontamination of bacteria.

Dendritic cell internalization of foam-structured fluorescent mesoporous silica nanoparticles

In this paper, foam-structured fluorescent mesoporous silica nanoparticles (FMSNs) are produced in a sol-gel method with the introduction of a phosphonate functional group. It is found that the phosphonate functionalized FMSNs with the foam structure minimizes the aggregation of FMSNs in solution. The average particle size of the FMSNs without and with phosphonate functionalization is 46.3 ± 5 nm and 60.5 ± 8 nm in diameter, respectively. The latter one exhibits higher fluorophore loading capacity (~67 ± 2.5%). The excitation wavelength (λ(ex)) of FMSNs is observed at 526 nm, approximate 12 nm larger in the Stoke-shift compared to the free organic dye at 494/514 nm. Furthermore, the photostability of the hydrophobic fluorophore is greatly improved by the FMSNs with the foam structure. In addition, the dose-dependent nature of FMSN uptake is assessed for the immune cells, the bone marrow-derived dendritic immune cells (BMDCs). Our results indicate that approximately 42% of BMDCs are able to take up foam-structured FMSNs (>5 μg/ml) without decreasing the viability of BMDCs. Thus, the phosphonate functionalized FMSNs with the foam structure are suitable to be used for many biomedical applications, especially in cell tracking.

Quantum dots/silica/polymer nanocomposite films with high visible light transmission and UV shielding properties

The dispersion of light-absorbing inorganic nanomaterials in transparent plastics such as poly(ethylene-co-vinyl acetate) (PEVA) is of enormous current interest in emerging solar materials, including photovoltaic (PV) modules and commercial greenhouse films. Nanocrystalline semiconductor or quantum dots (QDs) have the potential to absorb UV light and selectively emit visible light, which can control plant growth in greenhouses or enhance PV panel efficiencies. This work provides a new and simple approach for loading mesoporous silica-encapsulated QDs into PEVA. Highly luminescent CdS and CdS-ZnS core-shell QDs with 5 nm size were synthesized using a modified facile approach based on pyrolysis of the single-molecule precursors and capping the CdS QDs with a thin layer of ZnS. To make both the bare and core-shell structure QDs more resistant against photochemical reactions, a mesoporous silica layer was grown on the QDs through a reverse microemulsion technique based on hydrophobic interactions. By careful experimental tuning, this encapsulation technique enhanced the quantum yield (∼65%) and photostability compared to the bare QDs. Both the encapsulated bare and core-shell QDs were then melt-mixed with EVA pellets using a mini twin-screw extruder and pressed into thin films with controlled thickness. The results demonstrated for the first time that mesoporous silica not only enhanced the quantum yield and photostability of the QDs but also improved the compatibility and dispersibility of QDs throughout the PEVA films. The novel light selective films show high visible light transmission (∼90%) and decreased UV transmission (∼75%).

Supercritical CO2 synthesized TiO2 nanowires covalently linked with core–shell CdS–ZnS quantum dots: enhanced photocatalysis and stability

Semiconductor quantum dots (QDs) sensitized onto nano TiO2 as heterogeneous photocatalysts have drawn considerable interest over the past few years. However, stability of the QDs attached to TiO2 and consistent photocatalysis are still major challenges of this approach. We describe herein, a facile process to fabricate nanocomposites from porous TiO2 nanowires and bare CdS and core–shell CdS–ZnS QDs, where the QD particles are linked covalently to the titania surface through a bifunctional organic linker, mercapto propionic acid (MPA). A thin layer of ZnS was grown on 6 nm CdS QDs to restrain the photocorrosion and passivate the trap states, enhancing the photoluminescence and quantum yield. The bifunctional linking molecule, MPA, was found to effectively disperse and stabilize the QD nanoparticles. The photocatalytic activities of the prepared catalysts were evaluated under ultraviolet and visible light solar irradiation for the photodegradation of methylene blue (MB), an organic dye. The decomposition rate of MB was enhanced as follows: CdSZnS–MPA–TiO2 > CdS–MPA–TiO2 > CdSZnS–TiO2 > CdS–TiO2 > TiO2 > P25. A maximum photodegradation efficiency of MB dye (∼88%) was obtained by core–shell CdS–ZnS QDs linked with nano TiO2. After 3 cycling tests of degradation, the loss of photoactivity was significantly minimized (from 68% to 10%) by CdSZnS–MPA–TiO2 compared to CdSZnS–TiO2 (by direct deposition).

Photo-physical properties enhancement of bare and core-shell quantum dots

Semiconductor nanocrystals (NCs) (also known as quantum dots, QDs) have attracted immense attention for their size-tunable optical properties that makes them impressive candidates for solar cells, light emitting devices, lasers, as well as biomedical imaging. However monodispersity, high and consistent photoluminescence, photostability, and biocompatibility are still major challenges. This work focuses on optimizing the photophysical properties and biocompatibility of QDs by forming core-shell nanostructures and their encapsulation by a carrier. Highly luminescent CdS and CdS-ZnS core-shell QDs with 5 nm sizes were synthesized using a facile approach based on pyrolysis of the single molecule precursors. After capping the CdS QDs with a thin layer of ZnS to reduce toxicity, the photoluminescence and photostability of the core-shell QDs was significantly enhanced. To make both the bare and core/shell structure QDs more resistant against photochemical reactions, a mesoporous silica layer was grown on the QDs...

Fabrication of fluorescent labeled ginseng polysaccharide nanoparticles for bioimaging and their immunomodulatory activity on macrophage cell lines

Polysaccharides are a major active component of American ginseng root showing various biological activities including anti-carcinogenic, anti-aging, immunostimulatory and antioxidant effects. Although their biological activity has been reported by several groups, no research has explored their cellular uptake and biodistribution, owing to the lack of suitable detection techniques in living cells. This work examines a novel, simple and efficient fluorescent labeling procedure of ginseng polysaccharides (PS), in order to examine their cellular distribution using confocal microscopy. This procedure utilized a one-pot strategy with fluorescein-5-thiosemicarbazide (FTSC) to introduce a thiosemicarbazide group onto the aldehyde group at the reducing saccharide end to form a stable amino derivative through reductive amination. This polysaccharide-FTSC derivative was then characterized by GPC, UV, FTIR, photoluminescence and fluorescence microscopy to confirm attachment and any structural changes. The results demonstrated that the labeled ginseng PS nanostructure showed high fluorescence with minimal changes in PS molecular weight. The labeled PS exhibited almost no cytotoxicity effect against tumor induced macrophage cell lines (RAW 264.7) while retaining high immunostimulating activity similar to the non-labeled ginseng PS. Therefore, the developed approach provides a convenient and highly efficient fluorescent labeling procedure for understanding the mechanism of ginseng PS uptake in macrophage cell lines.

Enhancement of Photocurrent in Dye-Sensitized Solar Cells Using Bismuth Doped TiO2- Graphene as a Hot Carrier Transport

Enhancement of Photocurrent in Dye-Sensitized Solar Cells Using Bismuth Doped TiO2- Graphene as a Hot Carrier Transport Dye-sensitized solar cells (DSSCs) are of tremendous current interest, but they suffer from a lack of ability to harness the majority of visible light, or require heavy metal addition such as Pb or Cd which are not considered environmentally friendly. By decorating doped metal oxides such as titania with earth abundant and friendly metals on functionalized graphene sheets (FGSs), functional mats are enabled for enhanced light harvesting. In this work, novel highly crystalline bismuth doped TiO2 nanocrystals were prepared successfully by a facile sol-gel hydrothermal process and attached to FGS’s to make functional catalyst mats.

Local Release of Basic Fibroblast Growth Factor (bFGF) through Silica Nanoparticles-laden Biomimic Matrix

Basic fibroblast growth factor (bFGF), a protein, plays a key role in wound healing and blood vessel regeneration. However, most negative effects in vivo , or in vitro result from the over dosage of bFGF. Furthermore, it needs to keep the bFGF from protein denaturant. Thus, this study aims to develop a new delivery system based on silica nanoparticles (SiO 2 NPs) dispersed in collagen patch for delivery of the bFGF in a local and prolonged manner. In this research, SiO 2 NPs are used to encapsulate bFGF through a modified water-in-oil micro-emulsion. The bFGF-loaded nanoparticles afterwards are dispersed in the collagen-based matrix through a EDC cross-linking step. The in vitro release kinetics of SiO2 NPs - encapsulated bFGF with and without collagen matrix have been monitored through ELISA. In addition, the cytotoxicity of SiO 2 NPs is investigated by studying the viability of Human Umbilical Vein Endothelial Cells (HUVEC) under the different concentrations of SiO 2 NPs. It has found the average diameter ( d ) for SiO 2 NPs encapsulating bFGF is 45 ± 8 nm with a loading efficiency of 72.5±3%. The maximum concentration of bFGF locally released from SiO 2 NPs impregnated collagen matrix can be monitored after 30 days, while bFGF released from SiO 2 NPs can be detected in 20 days. The further prolonged releasing after the nanoparticle-encapsulated bFGF laden collagen matrix is possibly due to the interaction between the nanoparticles and collagen matrix. In addition, the biocompatibility of the SiO 2 NP has been investigated. We found that SiO 2 NPs at the concentration of 50 μg/ml can still keep the cell alive. The results indicate that the nanoparticle-laden collagen matrix can locally deliver growth factor in a prolonged manner. This new delivery system may benefit to blood vessel regeneration and potentiate greater angiogenesis.