Khairunisak Abdul Razak

Overview of the main methods used to combine proteins with nanosystems: absorption, bioconjugation, and encapsulation.

The latest development of protein engineering allows the production of proteins having desired properties and large potential markets, but the clinical advances of therapeutical proteins are still limited by their fragility. Nanotechnology could provide optimal vectors able to protect from degradation therapeutical biomolecules such as proteins, enzymes or specific polypeptides. On the other hand, some proteins can be also used as active ligands to help nanoparticles loaded with chemotherapeutic or other drugs to reach particular sites in the body. The aim of this review is to provide an overall picture of the general aspects of the most successful approaches used to combine proteins with nanosystems. This combination is mainly achieved by absorption, bioconjugation and encapsulation. Interactions of nanoparticles with biomolecules and caveats related to protein denaturation are also pointed out. A clear understanding of nanoparticle-protein interactions could make possible the design of precise and versatile hybrid nanosystems. This could further allow control of their pharmacokinetics as well as activity, and safety.

Structural and Morphology of ZnO Nanorods Synthesized Using ZnO Seeded Growth Hydrothermal Method and Its Properties as UV Sensing

In this study, zinc oxide (ZnO) nanorod arrays were synthesized using a simple hydrothermal reaction on ZnO seeds/n-silicon substrate. Several parameters were studied, including the heat-treatment temperature to produce ZnO seeds, zinc nitrate concentration, pH of hydrothermal reaction solution, and hydrothermal reaction time. The optimum heat-treatment temperature to produce uniform nanosized ZnO seeds was 400°C. The nanorod dimensions depended on the hydrothermal reaction parameters. The optimum hydrothermal reaction parameters to produce blunt tip-like nanorods (770 nm long and 80 nm in top diameter) were 0.1 M zinc nitrate, pH 7, and 4 h of growth duration. Phase analysis studies showed that all ZnO nanorods exhibited a strong (002) peak. Thus, the ZnO nanorods grew in a c-axis preferred orientation. A strong ultraviolet (UV) emission peak was observed for ZnO nanorods grown under optimized parameters with a low, deep-level emission peak, which indicated high optical property and crystallinity of the nanorods. The produced ZnO nanorods were also tested for their UV-sensing properties. All samples responded to UV light but with different sensing characteristics. Such different responses could be attributed to the high surface-to-volume ratio of the nanorods that correlated with the final ZnO nanorods morphology formed at different synthesis parameters. The sample grown using optimum synthesis parameters showed the highest responsivity of 0.024 A/W for UV light at 375 nm under a 3 V bias.

The effects of size and synthesis methods of gold nanoparticle-conjugated MαHIgG4 for use in an immunochromatographic strip test to detect brugian filariasis

This study describes the properties of colloidal gold nanoparticles (AuNPs) with sizes of 20, 30 and 40 nm, which were synthesized using citrate reduction or seeding-growth methods. Likewise, the conjugation of these AuNPs to mouse anti-human IgG(4) (MαHIgG(4)) was evaluated for an immunochromatographic (ICG) strip test to detect brugian filariasis. The morphology of the AuNPs was studied based on the degree of ellipticity (G) of the transmission electron microscopy images. The AuNPs produced using the seeding-growth method showed lower ellipticity (G ≤ 1.11) as compared with the AuNPs synthesized using the citrate reduction method (G ≤ 1.18). Zetasizer analysis showed that the AuNPs that were synthesized using the seeding-growth method were almost monodispersed with a lower polydispersity index (PDI; PDI≤0.079), as compared with the AuNPs synthesized using the citrate reduction method (PDI≤0.177). UV-visible spectroscopic analysis showed a red-shift of the absorbance spectra after the reaction with MαHIgG(4), which indicated that the AuNPs were successfully conjugated. The optimum concentration of the BmR1 recombinant antigen that was immobilized on the surface of the ICG strip on the test line was 1.0 mg ml(-1). When used with the ICG test strip assay and brugian filariasis serum samples, the conjugated AuNPs-MαHIgG(4) synthesized using the seeding-growth method had faster detection times, as compared with the AuNPs synthesized using the citrate reduction method. The 30 nm AuNPs-MαHIgG(4), with an optical density of 4 from the seeding-growth method, demonstrated the best performance for labelling ICG strips because it displayed the best sensitivity and the highest specificity when tested with serum samples from brugian filariasis patients and controls.

In Vitro evaluation of cytotoxicity of colloidal amorphous silica nanoparticles designed for drug delivery on human cell lines

Silica nanoparticles are being developed and tested vigorously in drug delivery systems to treat various diseases. There are many advantages of using silica nanoparticles as a nanodelivery system because they are relatively inexpensive to produce, chemically inert, thermally stable and can be tailored to contain porous structures for drug encapsulation and to be hydrophilic for higher solubility in the human body. Despite these tremendous benefits, one of the pivotal requirements of these drug delivery systems is to be biocompatible with the human body. In this study, the cytotoxicity of colloidal amorphous silica nanoparticles synthesized using the micelle formation method has been tested against normal human foreskin fibroblast cell line (Hs27) as well as selected human bone carcinoma (U-2 OS), human breast cancer (MCF-7), and human cervical carcinoma (HeLa) and (Ca Ski) cell lines to determine the IC50 values. Two different sizes of silica nanoparticles, 20nm and 40 nm, were used to study the relationship between their size and the level of toxicity exerted on the different cells being tested. The cytotoxicity results indicated that 20nm and 40 nm silica nanoparticles significantly reduce cell viability in a dose- and cell-type-dependent manner in the normal and cancerous cells tested.

Sintering of Silver–Aluminum Nanopaste With Varying Aluminum Weight Percent for Use as a High-Temperature Die-Attach Material

A new Ag-Al nanopaste die-attach system for high-temperature use is introduced for the first time in this paper. The Ag-Al nanopaste with varying Al nanoparticle weight percent (wt%) is sintered at 380°C for 30 min. The effects of organic burn-off from the nanopaste in aiding solid-state fusion between the Ag and Al nanoparticles are investigated. The formation of Ag2Al and Ag3Al is detected in post-sintered nanopaste layers. Thermal and electrical conductivity measurements are also conducted to understand the properties of the post-sintered Ag-Al die-attach material in relation to increasing Al content. Thermal expansion analysis is performed to gauge the expansion of the post-sintered Ag-Al nanopaste against other high-temperature packaging components, as it is critical to avoid thermal stresses during device operation.

Gold nanoparticles deposited on linker-free silicon substrate and embedded in aluminum Schottky contact

Given the enormous importance of Au nanoparticles (NPs) deposition on Si substrates as the precursor for various applications, we present an alternative approach to deposit Au NPs on linker-free n- and p-type Si substrates. It is demonstrated that, all conditions being similar, there is a significant difference between densities of the deposited NPs on both substrates. The Zeta-potential and polarity of charges surrounding the hydroxylamine reduced seeded growth Au NPs, are determined by a Zetasizer. To investigate the surface properties of Si substrates, contact angle measurement is performed. Field-emission scanning electron microscope is then utilized to distinguish the NPs density on the substrates. Finally, Al/Si Schottky barrier diodes with embedded Au NPs are fabricated, and their structural and electrical characteristics are further evaluated using an energy-filtered transmission electron microscope and current-voltage measurements, respectively. The results reveal that the density of NPs is significantly higher on n-type Si substrate and consequently has more pronounced effects on the electrical characteristics of the diode. It is concluded that protonation of Si-OH group on Si surface in low pH is responsible for the immobilization of Au NPs, which eventually contributes to the lowering of barrier height and enhances the electrical characteristics.

Direct formation of gold nanoparticles on substrates using a novel ZnO sacrificial templated-growth hydrothermal approach and their properties in organic memory device

This study describes a novel fabrication technique to grow gold nanoparticles (AuNPs) directly on seeded ZnO sacrificial template/polymethylsilsesquioxanes (PMSSQ)/Si using low-temperature hydrothermal reaction at 80°C for 4 h. The effect of non-annealing and various annealing temperatures, 200°C, 300°C, and 400°C, of the ZnO-seeded template on AuNP size and distribution was systematically studied. Another PMMSQ layer was spin-coated on AuNPs to study the memory properties of organic insulator-embedded AuNPs. Well-distributed and controllable AuNP sizes were successfully grown directly on the substrate, as observed using a field emission scanning electron microscope followed by an elemental analysis study. A phase analysis study confirmed that the ZnO sacrificial template was eliminated during the hydrothermal reaction. The AuNP formation mechanism using this hydrothermal reaction approach was proposed. In this study, the AuNPs were charge-trapped sites and showed excellent memory effects when embedded in PMSSQ. Optimum memory properties of PMMSQ-embedded AuNPs were obtained for AuNPs synthesized on a seeded ZnO template annealed at 300°C, with 54 electrons trapped per AuNP and excellent current–voltage response between an erased and programmed device.

The formation of WO3 nanorods using the surfactant-assisted hydrothermal reaction

Monoclinic tungsten oxide (WO3) nanorods were grown using the hydrothermal method on a seeded W foil. The seed layer was formed by thermal oxidation of W foil at 400°C for 30 min. Cetyltrimethylammonium bromide (CTAB) or hexamethylamine (HMT) was used in the reactive hydrothermal bath, along with sodium tungstate dihydrate (Na2WO4.2H2O) and hydrochloric acid (HCl). The concentration of CTAB was varied from 0.01 M to 0.07 M and the concentration of HMT was varied from 0.01 M and 0.05 M. The result showed that CTAB-assisted hydrothermal reaction produced WO3 nanorods with 4–7 nm diameter, and provided that CTAB concentration was less than 0.07 M. WO3 nanorods could not be obtained when CTAB concentration was 0.07 M. Columnar structured WO3 was produced with the presence of HMT in the hydrothermal bath. This was due to decomposition of HMT to form hydroxyl ions (OH−) that inhibited the growth of nanorods. Cyclic voltammetry (CV) analysis showed better electrochromic property of WO3 nanorods compared to columnar structured WO3.

Properties of gold nanoparticles synthesized in aqueous solution

This work describes the properties of gold nanoparticles synthesized in an aqueous solution via seed mediated growth method. With the seeds mediated growth method, gold nanorods and bipyramids nanoparticles were formed by changing the initial precursors such as concentration of silver nitrate (AgNO3), concentration of cetyltrimethylammonium bromide (CTAB), and volume of seed solution. The optimum AgNO3 concentration to synthesize gold nanorods and bipyramids nanoparticles was at 0.004 M. Above 0.004 M AgNO3, the yield of gold nanorods and bipyramids nanoparticles produced decreased and some facet nanoparticles with tips were produced. The optimum CTAB concentration to produce the highest yield of gold nanorods and bipyramids nanoparticles was 0.2 M. Lesser than 0.2 M CTAB lead to formation of irregularly facet nanoparticles with tips. While higher than 0.2 M CTAB, shorter gold nanorod and bipyramids nanoparticles were formed. The optimum volume of seed solution to synthesize gold nanorods and bipyramids n...

Encapsulation efficacy of natural and synthetic photosensitizers by silica nanoparticles for photodynamic applications.

This study analysed the physical effects of Cichorium Pumilum (CP), as a natural photosensitizer (PS), and Protoporphyrin IX (PpIX), as a synthetic PS, encapsulated with silica nanoparticles (SiNPs) in photodynamic therapy. The optimum concentrations of CP and PpIX, needed to destroy Red Blood Cells (RBC), were determined and the efficacy of encapsulated CP and PpIX were compared with naked CP and PpIX was verified. The results confirmed the applicability of CP and PpIX encapsulated in SiNPs on RBCs, and established a relationship between the encapsulated CP and PpIX concentration and the time required to rupture 50% of the RBCs (t50). The CP and PpIX encapsulated in SiNPs exhibited higher efficacy compared with that of naked CP and PpIX, respectively, and CP had less efficacy compared with PpIX.