Synthesis, properties, and optical applications of noble metal nanoparticle-biomolecule conjugates

Synthesis of Silicon and Germanium Oxide Nanostructures via Photonic Curing; a Facile Approach to Scale Up Fabrication

Silicon and Germanium oxide (SiOx and GeOx) nanostructures are promising materials for energy storage applications due to their potentially high energy density, large lithiation capacity (~10X carbon), low toxicity, low cost, and high thermal stability. This work reports a unique approach to achieving controlled synthesis of SiOx and GeOx nanostructures via photonic curing. Unlike conventional methods like rapid thermal annealing, quenching during pulsed photonic curing occurs rapidly (sub-millisecond), allowing the trapping of metastable states to form unique phases and nanostructures. We explored the possible underlying mechanism of photonic curing by incorporating laws of photophysics, photochemistry, and simulated temperature profile of thin film. The results show that photonic curing of spray coated 0.1 M molarity Si and Ge Acetyl Acetate precursor solution, at total fluence 80 J cm-2 can yield GeOx and SiOx nanostructures. The as-synthesized nanostructures are ester functionalized due to photoinitiated chemical reactions in thin film during photonic curing. Results also showed that nanoparticle size changes from ~48 nm to ~11 nm if overall fluence is increased by increasing the number of pulses. These results are an important contribution towards large-scale synthesis of the Ge and Si oxide nanostructured materials which is necessary for next-generation energy storage devices.

A colorimetric detection of Hg2+ based on gold nanoparticles synthesized oxidized N-methylpyrrolidone as a reducing agent

In this study, a gold nanoparticles colorimetric probe (AuNPs) with direct response to mercury ions (Hg2+) were developed using treated N-methylpyrrolidone (NMP) and chloroauric acid (HAuCl4) as precursors. NMP showed good reducibility after high temperature hydrolysis and could be used as reducing and stabilizing agent to synthesize AuNPs. The prepared AuNPs have obvious characteristic absorption peaks and appear wine-red. At the same time, it was found that the presence of Hg2+ can cause the aggregation of AuNPs, increased the absorbance at 700 nm, and changed the color of the solution into blue-gray. This method is capable of sensitive and specific determination of Hg2+ ranging from 1 to 30 μM, with the limit of detection (LOD) at 0.3 μM. The method showed good specificity for the determination of Hg2+ and has the potential to be applied to Hg2+ detection in sewage samples in the environment.

Investigation of the Performance of Heterogeneous MOF-Silver Nanocube Nanocomposites as CO2 Reduction Photocatalysts by In Situ Raman Spectroscopy

Here, we fabricated two different heterogeneous nanocomposites, core-shell MOF-AgNC and corner MOF-AgNC, as photocatalysts for CO₂ conversion by generating metal-organic frameworks (MOFs) on silver nanocube templates. These MOF-AgNC nanocomposites showed good CO₂ adsorption features and high CO₂ reduction reactivity. The performances of these MOF-AgNC nanocomposites in CO₂ adsorption and CO₂ reduction reactions can be characterized by in situ Raman spectrum measurement. The corner MOF-AgNC nanocomposite exhibited a faster CO₂ adsorption rate than the core-shell MOF-AgNC nanocomposite, which was due to the higher surface area/volume ratio of the MOF in corner MOF-AgNC. The CO₂ reaction reactivity and mechanisms (products of the reaction) of CO₂ reduction also depended on the morphologies of MOF-AgNC nanocomposites, which were caused by different reaction environments at the interface between the MOF and AgNCs. The CO₂ reduction reactivity of MOF-AgNC nanocomposites also exhibited high sensitivity to the irradiation intensity and wavelength, which was caused by the variation of the number of hot electrons and their positions in AgNCs with the irradiation intensity and irradiation wavelength, respectively. This method for the synthesis of heterogeneous nanocomposites should make it possible to design photocatalysts for various reactions by carefully designing the morphology and composition of nanocomposites.

Simultaneous Stabilization and Functionalization of Gold Nanoparticles via Biomolecule Conjugation: Progress and Perspectives

Gold nanoparticles (AuNPs) are used in various biological applications because of their small surface area-to-volume ratios, ease of synthesis and modification, low toxicity, and unique optical properties. These properties can vary significantly with changes in AuNP size, shape, composition, and arrangement. Thus, the stabilization of AuNPs is crucial to preserve the properties required for biological applications. In recent years, various polymer-based physical and chemical methods have been extensively used for AuNP stabilization. However, a new stabilization approach using biomolecules has recently attracted considerable attention. Biomolecules such as DNA, RNA, peptides, and proteins are representative of the biomoieties that can functionalize AuNPs. According to several studies, biomolecules can stabilize AuNPs in biological media; in addition, AuNP-conjugated biomolecules can retain certain biological functions. Furthermore, the presence of biomolecules on AuNPs significantly enhances their biocompatibility. This review provides a representative overview of AuNP functionalization using various biomolecules. The strategies and mechanisms of AuNP functionalization using biomolecules are comprehensively discussed in the context of various biological fields.

Transformation of Biowaste for Medical Applications: Incorporation of Biologically Derived Silver Nanoparticles as Antimicrobial Coating

Nanobiotechnology has undoubtedly influenced major breakthroughs in medical sciences. Application of nanosized materials has made it possible for researchers to investigate a broad spectrum of treatments for diseases with minimally invasive procedures. Silver nanoparticles (AgNPs) have been a subject of investigation for numerous applications in agriculture, water treatment, biosensors, textiles, and the food industry as well as in the medical field, mainly due to their antimicrobial properties and nanoparticle nature. In general, AgNPs are known for their superior physical, chemical, and biological properties. The properties of AgNPs differ based on their methods of synthesis and to date, the biological method has been preferred because it is rapid, nontoxic, and can produce well-defined size and morphology under optimized conditions. Nevertheless, the common issue concerning biological or biobased production is its sustainability. Researchers have employed various strategies in addressing this shortcoming, such as recently testing agricultural biowastes such as fruit peels for the synthesis of AgNPs. The use of biowastes is definitely cost-effective and eco-friendly; moreover, it has been reported that the reduction process is simple and rapid with reasonably high yield. This review aims to address the developments in using fruit- and vegetable-based biowastes for biologically producing AgNPs to be applied as antimicrobial coatings in biomedical applications.

Green synthesis of silver nanoparticles using Thymbra spicata L. var. spicata (zahter) aqueous leaf extract and evaluation of their morphology-dependent antibacterial and cytotoxic activity

Silver (Ag) nanoparticles (NPs) were green synthesized at room temperature using different concentrations of the Thymbra spicata L. var. spicata (Zahter) aqueous leaf extracts for the first time. With the synthesis of AgNPs using the leaf extract of Cynara scolymus (Artichoke) and Mentha piperita (Peppermint), the biological activities of the nanoparticles synthesized using leaf extract of three economically significant plants have been studied comparatively. Nanoparticles were characterized by different spectroscopic and microscopic analysis. TEM analysis of the biosynthesized AgNPs revealed that the size and shape of the AgNPs were changed with the plant extract concentration. Biologically synthesized AgNPs from leaf extracts of the three different plants displayed significant differences in antibacterial activity against two different gram-negative and gram-positive bacteria. Also, the results from this study show the shape dependence of the antibacterial and cytotoxic activity of silver nanoparticles synthesized using T. spicata leaf extract. The nanoparticles with different shapes exhibited the strongest antibacterial and cytotoxic activity compared to mostly spherical nanoparticles. Present results clearly indicate that biological activities of silver nanoparticles were affected by nanoparticle shape and the source of the plant extract used in the synthesis.

Evaluation of local anesthetic effects of Lidocaine-Ibuprofen ionic liquid stabilized silver nanoparticles in Male Swiss mice

A simple approach for the synthesis of Lidocaine-Ibuprofen ionic liquid stabilized silver nanoparticles (IL-AgNPs) was reported in this work. The shape, size and surface morphology of the Lidocaine-Ibuprofen ionic liquid stabilized AgNPs were characterized by using spectroscopic and microscopic techniques such as Ultraviolet-visible spectroscopy (UV-Visible), X-ray diffraction (XRD) analysis, Selected area electron diffraction (SAED), Transmission electron microscopy (TEM). TEM analysis showed the formation of 20-30nm size of IL-AgNPs with very clear lattice fringes. SAED pattern confirmed the highly crystalline nature of fabricated IL stabilized AgNPs. EDS results confirmed the formation of nanosilver. The fabricated IL-AgNPs were studied for their local anesthetic effect in rats. The results of local anesthetic effect showed that the time for onset of action by IL-AgNPs is 10min, which is significantly higher than that for EMLA. Further, tactile test results confirmed the stronger and faster local anesthetic effect of IL-AgNPs when compared to that of EMLA.

Environment friendly approach for size controllable synthesis of biocompatible Silver nanoparticles using diastase

A green, facile method for the size selective synthesis of silver nanoparticles (AgNPs) using diastase as green reducing and stabilizing agent is reported. The thiol groups present in the diastase are mainly responsible for the rapid reaction rate of silver nanoparticles synthesis. The variation in the size and morphology of AgNPs were studied by changing the pH of diastase. The prepared silver nanoparticles were characterized by using UV-vis, XRD, FTIR, TEM and SAED. The FTIR analysis revealed the stabilization of diastase molecules on the surface of AgNPs. Additionally, in-vitro cytotoxicity experiments concluded that the cytotoxicity of the as-synthesized AgNPs towards mouse fibroblast (3T3) cell lines is dose and size dependent. Furthermore, the present method is an alternative to the traditional chemical methods of size controlled AgNPs synthesis.

Cost effective surface functionalization of gold nanoparticles with a mixed DNA and PEG monolayer for nanotechnology applications

We report a cost effective and generally applicable method for co-functionalization of gold nanoparticles with a mixed DNA and PEG polymer layer.

Surface Modification Chemistries of Materials Used in Diagnostic Platforms with Biomolecules

Biomolecules including DNA, protein, and enzymes are of prime importance in biomedical field. There are several reports on the technologies for the detection of these biomolecules on various diagnostic platforms. It is important to note that the performance of the biosensor is highly dependent on the substrate material used and its meticulous modification for particular applications. Therefore, it is critical to understand the principles of a biosensor to identify the correct substrate material and its surface modification chemistry. The imperative surface modification for the attachment of biomolecules without losing their bioactivity is a key to sensitive detection. Therefore, finding of a modification method which gives minimum damage to the surface as well as biomolecule is highly inevitable. Different surface modification technologies are invented according to the type of a substrate used. Surface modification techniques of the materials used as platforms in the fabrication of biosensors are reviewed in this paper.

Fabrication and spectroscopic studies of folic acid-conjugated Fe3O4@Au core-shell for targeted drug delivery application

Gold coated magnetite core shell is a kind of nanoparticle that include magnetic iron oxide core with a thin layer nanogold. Fe3O4-gold core-shell nanostructure can be used in biomedical applications such as magnetic bioseparation, bioimaging, targeting drug delivery and cancer treatment. In this study, the synthesis and characterization of gold coated magnetite nanoparticles were discussed. Magnetite nanoparticles with an average size of 6 nm in diameter were synthesized by the chemical co-precipitation method and gold-coated Fe3O4 core-shell nanostructures were produced with an average size of 11.5 nm in diameter by reduction of Au(3+) with citrate ion in the presence of Fe3O4. Folate-conjugated gold coated magnetite nanoparticles were synthesized to targeting folate receptor that is overexpressed on the surface of cancerous cells. For this purpose, we used l-cysteine, as a bi-functional linker for attachment to gold surface and it was linked to the gold nanoparticles surface through its thiol group. Then, we conjugated amino-terminated nanoparticles to folic acid with an amide-linkage formation. These gold magnetic nanoparticles were characterized by various techniques such as X-ray powder diffraction (XRD) analysis, Fourier transform infrared spectrometer (FT-IR), UV-visible spectroscopy, transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), dispersive analysis of X-ray (EDAX) and vibrating sample magnetometer (VSM) analysis. The magnetic and optical properties of Fe3O4 nanostructure were changed by gold coating and attachment of l-cysteine and folic acid to Fe3O4@Au nanoparticles.

Spectroscopic investigation of interaction between bovine gamma globulin and gold nanoparticles

The interaction of Citrate-capped gold nanoparticles (AuNPs) with Bovine gamma globulin (BGG) was studied using Fourier transform infrared (FTIR), UV-Visible and Fluorescence spectroscopy. FTIR has confirmed the conjugation of AuNPs and BGG. Fluorescence quenching of tryptophan has confirmed the strong interaction between BGG and AuNPs. UV-Visible and Fluorescence spectroscopy have investigated the extent of interaction by determining the binding constants. Binding constants evaluated from UV-Visible and Fluorescence data are in good agreement with each other. An independent class of binding site on BGG for AuNPs has been predicted, where AuNPs interact with a highly solvent accessible tryptophan residue.

Localized surface plasmon resonance as a biosensing platform for developing countries

The discovery of the phenomena known as localized surface plasmon resonance (LSPR) has provided the basis for many research areas, ranging from materials science to biosensing. LSPR has since been viewed as a transduction platform that could yield affordable, portable devices for a multitude of applications. This review aims to outline the potential applications within developing countries and the challenges that are likely to be faced before the technology can be effectively employed.

Effect of the alkyl chain length of secondary amines on the phase transfer of gold nanoparticles from water to toluene

In the present paper we describe a phase transfer of aqueous synthesized gold nanoparticles (AuNPs) from water to toluene using secondary amines: dioctylamine, didodecylamine, and dioctadecylamine. The effect of the hydrocarbon chain length and amount of amines on the transfer efficiency were investigated in the case of nanoparticles (NPs) with three different sizes: 5, 9, and 13 nm. Aqueous colloids were precisely characterized before the transfer process using UV-vis spectroscopy, dynamic light scattering (DLS), small-angle X-ray scattering (SAXS), and transmission electron microscopy (TEM). Nanoparticles were next transferred to toluene and characterized using UV-vis and DLS techniques. It was found that dioctadecylamine provides the most effective transfer of nanoparticles. No time-dependent changes in the NP size were observed after 12 days, showing that the dioctadecylamine-stabilized nanoparticles dispersed in toluene were stable. This indicates that long hydrocarbon chains of dioctadecylamine exhibit sufficiently hydrophobic properties of nanoparticles and consequently their good dispersibility in nonpolar solvent.

Mesoporous silica coated gold nanorods loaded doxorubicin for combined chemo-photothermal therapy

The efficacy of the combined chemo-photothermal therapy, using a mesoporous silica-coated gold nanorods loaded DOX (pGNRs@mSiO2-DOX), was consistently tested both in vitro and in vivo. The prepared nanoparticles that were characterized using transmission electron microscopy (TEM), UV-vis absorption spectroscopy and zeta potential showed high doxorubicin loading capacity in addition to its pH-responsive release. The pGNRs@mSiO2-DOX photo-heat conversion characteristic found to be stable for several repeated NIR irradiated doses was tested in simulated body fluid. In vitro results showed that pGNRs@mSiO2-DOX causes a significant damage in breast cancer cell line MCF-7 compared to free DOX. Contrary to this, it showed low toxicity to human amnion wish cells compared to CTAB coated GNRs and free DOX. In vivo results showed that intravenous administration of pGNRs@mSiO2-DOX (1.7 mg/kg) markedly suppresses the growth of subcutaneous Ehrlich carcinoma in female Balb mice (p<0.0001). Consistently, histopathological examination revealed a complete loss of tumor cellular details for mice that received the combined treatment. Based on the obtained results, this passively targeted pGNRs@mSiO2-DOX could specifically deliver drug and excessive local heat to tumor sites achieving high combined therapeutic efficacy.