Functionalised gold nanoparticles for selective induction of in vitro apoptosis among human cancer cell lines

The interaction of citrate- and polyethylene imine (PEI)-functionalised gold nanoparticles (GNP) with cancer cell lines with respect to the cellular response was studied. It was found that GNP/citrate nanoparticles were able to induce apoptosis in human carcinoma lung cell lines A549, but GNP/PEI did not show any reduction in the viability of the cells in human breast cancer cell line MCF-7 and A549 cell lines. FACS data confirmed that the number of apoptotic cells increased with increase in the concentration of GNP/citrate nanoparticles. Decline in cellular expansion and changes in the nuclear morphology were noted after the treatment of GNP/citrate nanoparticles on A549 cell lines, which itself is a direct response for stress induction. The induction of cellular apoptosis was further confirmed by DNA fragmentation assay. These data confirm the potential of GNP/citrate nanoparticle to evoke cell-specific death response in the A549 cell lines.     

Characterisation of gold nanoparticles synthesised by leaf and seed extract of Syzygium cumini L.

Here, Syzygium cumini leaf extract (LE) and seed extract (SE) were explored for the synthesis of gold nanoparticles (GNP). LE and SE as well as their polar (water) fractions showed potential for GNP synthesis. Comparative synthesis kinetics and morphological characterisation studies revealed the synthesis of smaller sized GNP by LE than SE. Only polar (water) fractions showed potential for GNP synthesis, which are smaller in size compared to their respective extracts. SE contained more polyphenols and biochemical constituents than LE and therefore, showed higher synthesis rate and bigger sized GNP. Atomic force microscope and scanning electron microscope analysis indicated that both extracts and their fractions catalysed the synthesis of spherical GNP. The average size of GNP synthesised by LE, leaf water fraction (LWF), SE and seed water fraction (SWF) were 24, 23, 35 and 32?nm, respectively. Fourier transform infrared analysis identified the biomolecules involved in the synthesis and stability of GNP. This study documented the potential of S. cumini for the synthesis of GNP in addition to silver nanoparticles (SNP). However, nature and types of polyphenols involved in GNP synthesis seem to be different from that involved in SNP synthesis. This might be the possible reason for smaller sized GNP that SNP.     

Synthesis of protein–gold nanoparticle hybrid and gold nanoplates in protein aggregates

A straightforward and economically viable approach was developed to biomimetic synthesis of gold nanocrystals by using casein micelles (CMs) without additional reductant. The UV–vis, TEM, SAED, FTIR, DLS and XRD techniques were employed to systematically characterize Au nanocrystals synthesized. Isotropic gold nanoparticle (GNP) and gold nanoplates in good yields (up to 90%) with different sizes can be obtained easily by adjusting the experimental condition. Spherical nanoparticles were obtained with tunable mean sizes at higher pH and casein concentrations. The high colloidal stability of the spherical GNP is attributed to the formation of CM/GNP hybrid under some experimental condition. At lower pH, reaction temperature and casein concentrations, single-crystalline gold nanoplates in good yields (up to 90%) are obtained. The growth of these nanostructures is attributed to an interplay between the faceting tendency of the protein molecules/micelles and the growth kinetics. More importantly, the morphological evolution of large gold nanoplates at different reaction times has been followed, and compared with some earlier protein systems, different formation mechanisms in casein micelles are obtained. The results demonstrate that both the property of individual protein molecules and protein aggregates play important roles in controlling the formation of gold nanocrystals by using amphiphilic protein.     

Proteolytic Fluorescent Signal Amplification on Gold Nanoparticles for a Highly Sensitive and Rapid Protease Assay

A new strategy for highly sensitive and rapid protease assay is developed by mediating proteolytic formation of oligonucleotide duplexes and using the duplexes for signal amplification. In the presence of matrix metalloprotease‐2 (MMP‐2), fragmentation of the intact DNA–peptide on gold nanoparticles (GNP) by hydrolytic cleavage of a peptide bond within the substrate allows diffusion of DNA away from the GNP and the formation of a DNA/RNA heteroduplex, leading to digestion of RNA by RNase H. Because of the high quenching efficacy of GNP to the fluorophore in RNA and multiple digestions of the RNA, the fluorescence signal recovery is amplified. This method permits the assessment of the activity of MMP‐2 at concentrations as low as 10 pM within 4 h. Compared with the reported protease nanosensors using quantum dots, GNP, and magnetic nanoparticles with the same peptide sequence, the assay time of this method is sixfold faster and the limit of detection is 100‐fold more sensitive. The formulations for proteolytic formations of oligonucleotides duplexes for signal amplification on GNP could lead to the development of more sensitive and rapid protease assay techniques, thus extending the role of proteases as therapeutic targets and disease indicators.     

Synthesis and bio-applications of carbohydrate–gold nanoconjugates with nanoparticle and nanolayer forms

Carbohydrate-conjugated gold nanoparticles (GNPs) and gold nanolayers (GNLs), which have recently attracted increasing attention as innovative nano-biomaterials, were successfully synthesized using carbohydrate thiosemicarbazones in an aqueous N-methylmorpholine N-oxide (NMMO) system. This system can dissolve various types of carbohydrates including structural polysaccharides, e.g., cellulose. We observed that oxidative NMMO solvent unexpectedly promoted the immediate reduction of [Au^IIICl₄]^– species to nanosized metallic Au⁰, that is GNP. One possible mechanism is that the chloride ligand was oxidized to chlorate via the formation of a hypochlorite intermediate. Site-selective S-labeling of sugar reducing ends with thiosemicarbazide may have enabled regulated self-assembly immobilization to the surfaces of GNPs and GNLs. The carbohydrate–gold nanoconjugates possess unique nanoarchitectures and biofunctions for carbohydrate–cell interactions. Novel and simple approaches for the structural design of carbohydrate-decorated GNPs and GNLs in the NMMO system have potential to inspire a new phase in glyco-biomaterials engineering.     

纳米金与细胞相互作用机理的蛋白质组学研究

应用蛋白质组学结合生物信息学方法研究纳米金与人皮肤成纤维细胞(HDF-f )的作用机理.首先采用柠檬酸钠还原氛金酸法制备20nm的纳米金,然后应用MTT法和流式细胞术评价纳米金的细胞毒性及对细胞周期和细胞凋亡的影响.接着应用蛋白质组学技术和生物信息学方法筛选纳米金作用后细胞发生差异表达的蛋白质并进行基因本体论分析.MT...     

Molecular Hyperthermia: Spatiotemporal Protein Unfolding and Inactivation by Nanosecond Plasmonic Heating

Spatiotemporal control of protein structure and activity in biological systems has important and broad implications in biomedical sciences as evidenced by recent advances in optogenetic approaches. Here, this study demonstrates that nanosecond pulsed laser heating of gold nanoparticles (GNP) leads to an ultrahigh and ultrashort temperature increase, coined as “molecular hyperthermia”, which causes selective unfolding and inactivation of proteins adjacent to the GNP. Protein inactivation is highly dependent on both laser pulse energy and GNP size, and has a well‐defined impact zone in the nanometer scale. It is anticipated that the fine control over protein structure and function enabled by this discovery will be highly enabling within a number of arenas, from probing the biophysics of protein folding/unfolding to the nanoscopic manipulation of biological systems via an optical trigger, to developing novel therapeutics for disease treatment without genetic modification.     

Fluorescence near gold nanoparticles for DNA sensing

We investigated fluorescence quenching and enhancement near gold nanoparticles (GNP) of various sizes using fluorescently labeled hairpin DNA probes of different lengths. A closed hairpin caused intimate contact between the fluorophore and the gold, resulting in an efficient energy transfer (quenching). Upon hybridization with complementary DNA, the DNA probes were stretched yielding a strong increase in fluorescence signal. By carefully quantifying the amount of bound fluorescent probes and the GNP concentrations, we were able to determine the quenching and enhancement efficiencies. We also studied the size and distance dependence theoretically, using both FDTD simulations and the Gersten-Nitzan model and obtained a good agreement between experiments and theory. On the basis of experimental and theoretical studies, we report over 96.8% quenching efficiency for all particle sizes tested and a maximal signal increase of 1.23 after DNA hybridization. The described results also demonstrate the potential of gold nanoparticles for label free DNA sensing.     

Sterically controlled docking of gold nanoparticles on ferritin surface by DNA hybridization

Novel assemblies of DNA-functionalized gold nanoparticles (DNA-GNPs) have received considerable interest due to their fascinating properties which are desired for various detection applications. In this study, we present innovative GNP assemblies which have a cage-shaped protein ferritin in the center, and discrete GNPs sterically surrounding the central ferritin. These assemblies were constructed by hybridizing DNA-GNP to chemically DNA-modified ferritin, which has a hollow cavity or an iron NP core. Subsequent gel electrophoresis purification and transmission electron microscopy observation showed that ferritin/DNA/GNP assemblies were successfully constructed and can be isolated as independent functional units, which can be used to investigate not only the interaction between the GNPs of complicated GNP clusters but also the interaction between the GNPs and the internalized NP.     

Fluorophore-gold nanoparticle complex for sensitive optical biosensing and imaging

Fluorophores have been extensively used as the signal mediator in biosensing and bioimaging for a long time. Enhancement of fluorescence can amplify the signal, thus improving the sensitivity, enabling earlier and accurate disease detection and diagnosis. Some metal nanoparticles, such as gold and silver, can generate a strong electromagnetic field on their surface (surface plasmon field) upon receiving photonic energy. When a fluorophore is placed in the field, the field can affect the fluorophore electrons participating in fluorescence emission and change the fluorescence output. The change can be from complete quenching to significant enhancement, depending on the metal type, particle size and shape, excitation/emission wavelengths and quantum yield of the fluorophore, and the distance between the fluorophore and the particle surface. In this study, the effects of these parameters on the fluorescence enhancement of commonly used fluorophores by gold nanoparticles (GNPs) are theoretically analyzed. Experimentally, an NIR contrast agent with enhanced fluorescence was developed by carefully tailoring the distance between Cypate (ICG based fluorophore) and a GNP, via biocompatible spacer constructs. The effect of the GNP size (3.7-16.4 nm) and spacer length (3.2-4.6 nm) on fluorescence enhancement was studied, and the spacer length that provided the significant enhancement was determined. The spacer of 3.9 nm with 16.4 nm GNP provided the fluorescence of 360% of the control. The experimental data qualitatively agreed with the theoretical results and, thus, the theoretical analysis can be used as a guide for significantly improving the sensitivity of existing fluorescent contrast agents by properly utilizing GNPs and spacers.     

Gold nanoparticle induces masking of amines and some therapeutic implications

Citrate capped gold nanoparticles (GNP) are effective in masking protein amines. The extent of such masking is quantified using Fourier Transform Infra Red (FTIR) spectroscopy. A strong correlation is shown to exist between a shift of amide-II peak intensity (1600-1500 cm(-1)) caused by GNP and the number of exposed amines in a given protein. The result is validated using eight different proteins. The expected out-come of such masking is inhibition of interaction between any external ligand and such amines. The prediction is validated using a simple non-enzymatic glycation of clinically important protein like crystallin.     

高活性辣根过氧化物酶-金纳米偶联物的制备与表征

以辣根过氧化物酶（HRP）为模型,研究了一种新型的将蛋白分子固定在金纳米粒子（GNP）表面的方法,制备得到一种高活性的辣根过氧化物酶-金纳米粒子生物偶联物。采用水溶性碳化二亚胺法制备了生物素化辣根过氧化物酶在柠檬酸根离子稳定化的金纳米粒子表面,通过静电吸附链霉亲和素。生物素-亲和素体系方便地制备得到高活性的HRP—GNP生物偶联物,单位酶活力提高了10倍以上。HRP—GNP生物偶联方法在制备高活性的生物探针和固定化酶等领域具有广泛的应用前景。     

Chitosan-mediated synthesis of gold nanoparticles by UV photoactivation and their characterization

Recent researches have largely been focused on chitosan, which is deacetylated chitin, the most abundant natural polysaccharide after cellulose. In this paper, we report the fabrication of gold nanoparticles (GNPs) by UV photoactivation in the presence of biopolymeric chitosan and the tracing of the gold salt solution aging. Detailed UV-visible spectroscopy study witnessed the evolution of the surface plasmon resonance (SPR) adsorption during the GNP growth. The effect of chitosan in aqueous solution for the GNP preparation was investigated in detail. The results indicated the size and distribution of GNPs could be controlled over by altering the concentration of chitosan, and the GNP growth during aging was a chitosan-mediated autocatalytic process. Fourier transform infrared spectroscopy (FTIR) showed the hydroxyl in molecular chitosan was oxidized to carbonyl groups in the fabrication of GNPs after aging and nitrogen atoms are the main sites for the complexation of chitosan with Au atoms. Our synthesis method in the present way can be used to form self-assemble monolayers of GNPs and fabricate biosensors based on surface plasmon resonance effect.     

The effect of the number of parallel DNA molecules on electric charge transport through 'standing DNA'

We present morphological and electrical characterization of double-stranded DNA (dsDNA) molecules covalently bound to two metal electrodes: an underlying gold surface and a gold nanoparticle (GNP). Conductive atomic force microscope (cAFM) with a metallized tip is used to perform current-voltage (I-V) measurements through dsDNA molecules, connected to GNPs of different diameters 5, 10 and 20?nm. The number of DNA molecules coating the GNP is expected to vary with the surface area of the GNP. This number and the portion of the GNP surface area enabling hybridization of the DNA determine the number of DNA molecules connecting the GNP to the gold surface. The larger the diameter of the GNP the higher the expected number of dsDNA molecules connecting it to the gold surface and thus the expected current. Our results show similar currents for all three GNP sizes, indicating that current flows through the same number of molecules regardless of the diameter of the measured GNP. The measured currents, 220 nA at 2?V, are in accordance with our previous reports (Cohen et al 2005 Proc. Natl Acad. Sci. USA 102 11589-93; Cohen et al 2006 Faraday Discuss. 131 367-76) in which we demonstrated the validity of the experimental system. In particular, for the 5?nm GNP, we conclude that the current possibly flows through two to three molecules, likely only one, and that a single short dsDNA molecule can support at least ～70?nA, and probably 220?nA.     

Localized surface plasmon coupled fluorescence fiber-optic biosensor with gold nanoparticles

A novel fiber-optic biosensor based on a localized surface plasmon coupled fluorescence (LSPCF) system is proposed and developed. This biosensor consists of a biomolecular complex in a sandwich format of . It is immobilized on the surface of an optical fiber where a complex forms the fluorescence probe and is produced by mixing Cy5-labeled antibody and protein A conjugated gold nanoparticles (Au-PA). The LSPCF is excited by localized surface plasmon on the GNP surface where the evanescent field is applied near the core surface of the optical fiber. At the same time, the fluorescence signal is detected by a photomultiplier tube located beside the unclad optical fiber with high collection efficiency. Experimentally, this novel LSPCF biosensor is able to detect mouse immunoglobulin G (IgG) at a minimum concentration of 1 pg/mL (7 fM) during the biomolecular interaction of the IgG with anti-mouse IgG. The analysis is expanded by a discussion of the amplification of the LSPCF intensity by GNP coupling, and overall, this LSPCF biosensor is confirmed experimentally as a biosensor with very high sensitivity.     

Measuring the flexibility of immunoglobulin by gold nanoparticles

We measured the flexibility of Fab and Fc arms of immunoglobulin using gold nanoparticles (GNPs). Enzyme-linked immunosorbent assay was performed to measure the affinity of anti-5 nm GNP antiserum against various sizes of GNPs. The flexibility of Fc was also measured by electron microscopy. The restricted binding affinity indicated that only a very limited amount of freedom was allowed for the Fab-Fab hinge, while Fab-Fc showed a much larger degree of freedom.     

Room temperature direct space-selective growth of gold nanoparticles inside a silica matrix based on a femtosecond laser irradiation

A one-step procedure without heat-treatment was carried out to yield the space-selective growth of gold nanoparticles inside a transparent silica matrix. A silica porous monolith was prepared via a sol-gel route and then post-doped with an aqueous solution of hydrogen tetrachloroaurate (HAuCl₄) as a gold precursor, in the presence of sodium carbonate as an additive. Direct and local precipitation of gold nanoparticles inside the deep volume of the silica matrix was induced by a femtosecond laser irradiation at room temperature. Gold nanoparticles with size of about 50-60 nm were evidenced by absorption spectroscopy and transmission electron microscopy. The additive is assumed to be involved in a photo-electrochemical mechanism including redox reactions, which is necessary to the formation of gold nanoparticles.     

Porous Gold Nanoshells on Functional NH2‐MOFs: Facile Synthesis and Designable Platforms for Cancer Multiple Therapy

AuroShell nanoparticles (sealed gold nanoshell on silica) are the only inorganic materials that are approved for clinical trial for photothermal ablation of solid tumors. Based on that, porous gold nanoshell structures are thus critical for cancer multiple theranostics in the future owing to their inherent cargo‐loading ability. Nevertheless, adjusting the diverse experimental parameters of the reported procedures to obtain porous gold nanoshell structures is challenging. Herein, a series of amino‐functionalized porous metal–organic frameworks (NH₂‐MOFs) nanoparticles are uncovered as superior templates for porous gold nanoshell deposition (NH₂‐MOFs@Au_shell) by means of a more facile and general one‐step method, which combines the enriched functionalities of NH₂‐MOFs with those of porous gold nanoshells. Moreover, in order to illustrate the promising applications of this method in biomedicine, platinum nanozymes‐encapsulated NH₂‐MOFs are further designed with porous gold nanoshell coating and photosensitizer chlorin e6 (Ce6)‐loaded nanoparticles with continuous O₂‐evolving ability (Pt@UiO‐66‐NH₂@Au_shell‐Ce6). The combination of photodynamic and photothermal therapy is then carried out both in vitro and in vivo, achieving excellent synergistic therapeutic outcomes. Therefore, this work not only presents a facile strategy to fabricate functionalized porous gold nanoshell structures, but also illustrates an excellent synergistic tumor therapy strategy.     

Synthesis process of gold nanoparticles in solution plasma

We describe the dynamics of the synthesis of gold nanoparticles by a glow discharge in aqueous solutions. A pulsed power supply was used to generate discharges in the aqueous solutions. The initial [AuCl₄]⁻ ion concentration and the voltage applied between the electrodes were varied. The [AuCl₄]⁻ ion was reduced by the H radicals generated in the discharge. The reduction rates were calculated from the changes in the [AuCl₄]⁻ ion concentration during the discharge time. Dendrite-shaped nanoparticles of about 150 nm size were formed in discharge during 1 min. The pH of the solution decreased gradually with the increase of the discharge time. The decrease in pH led to the dissolution of gold nanoparticles. The reduction and the dissolution rates increased proportionately with the applied voltage. The size of the gold nanoparticles decreased at 20 nm after running the discharge during 45 min. Moreover gold nanoparticles with exotic shapes, such as triangle, pentagon, and hexagon were also observed. The particles were confirmed to be as polycrystalline gold nanoparticles by electron diffraction patterns. In summary, when the reduction rate lowered as a result of dissolution, anisotropic nanoparticles were formed and continued to grow in size in the solution.     

Separation of long double-stranded DNA by nanoparticle-filled capillary electrophoresis

We present the first example of the analysis of long double-stranded (ds) DNA molecules by nanoparticle-filled capillary electrophoresis (NFCE). To avoid aggregation of the gold nanoparticles (GNPs) and to allow strong interactions with the DNA molecules, the gold nanoparticles were modified with poly(ethylene oxide) (PEO) via noncovalent bonding to form gold nanoparticle/polymer composites (GNPPs). The neutral GNPPs are heavy (approximately 2.0 x 10(8) g/mol for the 32-nm GNP) and thus slow the DNA molecules that they encounter during the electrophoretic process. Compared to linear polymer solutions, such as hydroxyethyl cellulose and PEO, the GNPPs provide greater efficiency and require significantly shorter times to separate long dsDNA. The separation of lambda-DNA (0.12-23.1 kbp) by NFCE at -250 V/cm was accomplished in 3 min. The ability to separate high molecular weight DNA markers (8.27-48.5 kbp) with plate numbers greater than 10(6) suggests that this novel method may hold great promise for the analysis of long-stranded DNA molecules such as chromosomes. Moreover, this method is simple and affordable when compared to those that use micro- and nanofabricated devices for separating long DNA molecules.