Gold glyconanoparticles for mimics and measurement of metal ion-mediated carbohydrate-carbohydrate interactions

Investigation of the Binding of Lectins with Polymer Glycoconjugates and the Glycoconjugates Containing Silver Nanoparticles by Means of Optical Spectroscopy and Light Scattering

The synthesis of glycoconjugates, lectin-specific polymers containing a carbohydrate ligand (spacered residue of N-acetyl-D-glucosamine, β-N-Gly-GlcNAc) has been carried out. Glyconanoparticles (glycol-NPs) containing a label detectable by means of spectrophotometry, silver nanoparticles, have been prepared on the basis of the glycoconjugates. Copolymers of maleic anhydride with ethylene or N-vinylpyrrolidone have been used as a carrier to introduce the carbohydrate ligand and a stabilizer of silver nanoparticles. Solutions of the glycoconjugates and the silver glyconanoparticles have been characterized by means of light scattering, UV-visible spectroscopy, and TEM. The interaction of the obtained glycoconjugates and silver glyconanoparticles with N-acetyl-D-glucosamine-specific lectins of Solanum tuberosum agglutinin (STA) and wheat germ agglutinin (WGA) has been investigated by means of light scattering and UV-visible spectro-scopy. The data obtained via these physical methods using the carbohydrate-containing derivatives labeled with silver nanoparticles have been in agreement. It has been shown that the glycoconjugates and silver glyconanoparticles based on more hydrophilic copolymer of maleic acid with N-vinylpyrrolidone are more sensitive than the respective systems based on more hydrophobic copolymer of maleic acid with ethylene. It has been also shown that the considered systems are more sensitive to the STA lectin than to the WGA lectin. The silver glyconanoparticles have allowed more accurate and reliable detection of the lectins by means of light scattering, as compared to the glycopolymer.

A Simple Yet Effective Preanalytical Strategy Enabling the Application of Aptamer-Conjugated Gold Nanoparticles for the Colorimetric Detection of Antibiotic Residues in Raw Milk

The misuse of antibiotics in the cattle sector can lead to milk contamination, with concomitant effects on the dairy industry and human health. Biosensors can be applied in this field; however, the influence of the milk matrix on their activity has been poorly studied in light of the preanalytical process. Herein, aptamer-conjugated gold nanoparticles (nanoaptasensors) were investigated for the colorimetric detection in raw milk of four antibiotics used in cattle. The effect of milk components on the colorimetric response of the nanoaptasensors was analyzed by following the selective aggregation of the nanoparticles, using the absorption ratio A₅₂₀/A₇₂₀. A preanalytical strategy was developed to apply the nanoaptasensors to antibiotic-contaminated raw milk samples, which involves a clarification step with Carrez reagents followed by the removal of cations through dilution, chelation (EDTA) or precipitation (NaHCO₃). The colorimetric signals were detected in spiked samples at concentrations of antibiotics as low as 0.25-fold the maximum residue limits (MRLs) for kanamycin (37.5 μg/L), oxytetracycline (25 μg/L), sulfadimethoxine (6.25 μg/L) and ampicillin (1 μg/L), according to European and Chilean legislation. Overall, we conclude that this methodology holds potential for the semiquantitative analysis of antibiotic residues in raw milk obtained directly from dairy farms.

Glyco disulfide capped gold nanoparticle synthesis: cytotoxicity studies and effects on lung cancer A549 cells

Background: Glyco disulfide gold nanoparticles (GDAuNPs) were prepared by three methods: direct, photochemical irradiation and ligand substitution. Glyco disulfide acted as reducing and capping agents of gold ions, to produce AuNPs GD1-GD16. Results: Shorter chains of glyco disulfides (n = 1 and 2) offered monodispersed and stable GDAuNPs in physiological pH, while longer chains (n = 3) furnished unstable nanoparticles. ζ-potential study of direct method GDAuNPs revealed surface charge dependency on the alkyl unit length. Transmission electron microscope imaging indicated that sizes/shapes of the ligand exchange AuNPs remained post-exchange step. The mechanism of GDAuNP formation was forecast as the Ostwald ripening effect at low pH of ligand (5.1-8.9) and reinforcement of static stabilization at high pH (12.4-13.0). Conclusion: GDAuNPs recorded moderately anticancer activity against the A549 cancer cell line, with IC₅₀ between 14.95 and 64.95 μg/ml.

A brief insight to the role of glyconanotechnology in modern day diagnostics and therapeutics

Carbohydrate-protein and carbohydrate-carbohydrate interactions are very important for various biological processes. Although the magnitude of these interactions is low compared to that of protein-protein interaction, the magnitude can be boosted by multivalent approach known as glycocluster effect. Nanoparticle platform is one of the best ways to present diverse glycoforms in multivalent manner and thus, the field of glyconanotechnology has emerged as an important field of research considering their potential applications in diagnostics and therapeutics. Considerable advances in the field have been achieved through development of novel techniques, use of diverse metallic and non-metallic cores for better efficacy and application of ever-increasing number of carbohydrate ligands for site-specific interaction. The present review encompasses the recent developments in the area of glyconanotechnology and their future promise as diagnostic and therapeutic tools.

Preparation, Functionalization, Modification, and Applications of Nanostructured Gold: A Critical Review

Gold nanoparticles (Au NPs) play a significant role in science and technology because of their unique size, shape, properties and broad range of potential applications. This review focuses on the various approaches employed for the synthesis, modification and functionalization of nanostructured Au. The potential catalytic applications and their enhancement upon modification of Au nanostructures have also been discussed in detail. The present analysis also offers brief summaries of the major Au nanomaterials synthetic procedures, such as hydrothermal, solvothermal, sol-gel, direct oxidation, chemical vapor deposition, sonochemical deposition, electrochemical deposition, microwave and laser pyrolysis. Among the various strategies used for improving the catalytic performance of nanostructured Au, the modification and functionalization of nanostructured Au produced better results. Therefore, various synthesis, modification and functionalization methods employed for better catalytic outcomes of nanostructured Au have been summarized in this review.

Synthesis and cytotoxic analysis of thiolated xylose derivatives decorated on gold nanoparticles

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Nanoparticles covered with carbohydrates constitute a good bio-mimetic model.

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D-xylose gold nanoparticles with linkages of alkyl or polyethylene glycol synthesized via D-xylosethiols.

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Forming self-assembled monolayers on gold nanoparticles.

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The potential use of intact or thiolated xylose derivatives decorated on AuNPs.

The rapid development of metal nanoparticles capped by an organic monolayer offers the possibility to create a whole new variety of products with novel characteristic, functions and applications. Among these, nanoparticles covered with carbohydrates (glyconanoparticles) constitute a good bio-mimetic model of carbohydrate presentation at the cell surface and are currently centered on many glycobiological and biomedical applications. In this study, a series of novel D-xylose gold nanoparticles (AuNPs) with linkages of alkyl or polyethylene glycol have been synthesized via D-xylosethiols, forming self-assembled monolayers on gold nanoparticles. The nano-gold solution, two carbohydrate derivatives and modified nano-gold solution were tested for cytotoxicity to check the biocompatibility. The MTT assay on NIH 3T3 cell lines confirmed that all the test materials showed no toxicity with the more than 90 % of cell viability in both low concentration (1 μM) and high concentration (100 μM), compared with the control.

Co-functionalization with phosphate and carboxylate on polydiacetylene for colorimetric detection of calcium ions in serum

In this study, co-functionalization with phosphate and carboxylate on polydiacetylene (PDA) was proposed to detect calcium ions in serum, inspired by biologically abundant phosphate-calcium ion and carboxylate-calcium ion binding. The cooperative interaction of calcium ions with phosphate and carboxylate in PDA induced the change of electronic properties in the backbone without aggregation of liposomes, accompanied by blue-to-purple color transition. The cooperative effect through the introduction of mixed ligands facilitated the selective detection of calcium ions over magnesium ions, which was a source of major interference in many calcium ion probes, and in the presence of major serum metal ions. The sensor system exhibited highly sensitive detection of calcium ions with an estimated limit of detection of 0.97 μM. In addition, the detection method was employed to determine the concentration of calcium ions in various serums.

Functionalization of Gold Nanoparticles by Inorganic Entities

The great affinity of gold surface for numerous electron-donating groups has largely contributed to the rapid development of functionalized gold nanoparticles (Au-NPs). In the last years, a new subclass of nanocomposite has emerged, based on the association of inorganic molecular entities (IME) with Au-NPs. This highly extended and diversified subclass was promoted by the synergy between the intrinsic properties of the shell and the gold core. This review-divided into four main parts-focuses on an introductory section of the basic notions related to the stabilization of gold nanoparticles and defines in a second part the key role played by the functionalizing agent. Then, we present a wide range of inorganic molecular entities used to prepare these nanocomposites (NCs). In particular, we focus on four different types of inorganic systems, their topologies, and their current applications. Finally, the most recent applications are described before an overview of this new emerging field of research.

Probing the glycopolymer–ion interaction via specific ion effects

Specific ion effects were used to probe the interactions between thermoresponsive glycopolymers and different ions.

Self-assembly of bacteria cellulose hydrogels carrying multiple carbohydrate appendages to visualize carbohydrate-carbohydrate interactions

Nata de coco was chemically modified to afford the bacterial cellulose hydrogels carrying terminal alkynes. The resultant hydrogels were then converted into hydrogels carrying lactosides or those carrying α-2,3-sialyllactosides by the Cu⁺-catalyzed alkyne-azide cyclization. The stable homo association of the hydrogels carrying lactosides was observed in an aqueous solution containing Ca²⁺, thereby demonstrating the Ca²⁺-mediated lactoside-lactoside interactions. Ca²⁺ also stabilized the hetero associations among the hydrogels carrying lactosides and those carrying α-2,3-sialyllactosides, thereby also demonstrating the Ca²⁺-induced interactions between the lactosides and the α-2,3-sialyllactosides. The sizes of these hydrogels were of the order of ca. 5 mm, and their associations could thus be readily monitored with the naked eye.

Synthesis of Glycosylated Metal Complexes for Probing Carbohydrate-Carbohydrate Interactions

Densely packed carbohydrate clusters on cell surfaces play essential roles in varieties of bioprocesses. Little information has been, however, accumulated so far concerning their structural/functional details. In this chapter, we discuss artificial systems to investigate carbohydrate-carbohydrate interactions within/between the carbohydrate cluster(s). Among such artificial systems, much attention will be especially placed on glycosylated tris-bipyridine ferrous complexes for monitoring not only carbohydrate-carbohydrate interactions within the glycocluster but also their resultant conformational changes.

Synthesis and conformational analysis of poly(phenylacetylene)s with serinol-tethered carbohydrate appendages

We synthesized phenylacetylenes containing β-lactoside, β-cellobioside, or β-maltoside, and polymerized them to produce the corresponding poly (phenylacetylene)s. In these poly (phenylacetylene)s, the pendent carbohydrates were tethered to the mainchains by serinol spacers. Because similar glycosyl serinol units are found in the natural glycosphingolipids in cell membranes, the densely packed carbohydrate clusters along the poly (phenylacetylene) mainchains act as molecular mimics of cell surface glycoclusters. We analyzed the conformation of the glycosylated poly (phenylacetylene)s using circular dichroism spectroscopy, and found that the spatial carbohydrate packing within the glycoclusters changed on the addition of salts.

Predicting the Structures of Glycans, Glycoproteins, and Their Complexes

Complex carbohydrates are ubiquitous in nature, and together with proteins and nucleic acids they comprise the building blocks of life. But unlike proteins and nucleic acids, carbohydrates form nonlinear polymers, and they are not characterized by robust secondary or tertiary structures but rather by distributions of well-defined conformational states. Their molecular flexibility means that oligosaccharides are often refractory to crystallization, and nuclear magnetic resonance (NMR) spectroscopy augmented by molecular dynamics (MD) simulation is the leading method for their characterization in solution. The biological importance of carbohydrate-protein interactions, in organismal development as well as in disease, places urgency on the creation of innovative experimental and theoretical methods that can predict the specificity of such interactions and quantify their strengths. Additionally, the emerging realization that protein glycosylation impacts protein function and immunogenicity places the ability to define the mechanisms by which glycosylation impacts these features at the forefront of carbohydrate modeling. This review will discuss the relevant theoretical approaches to studying the three-dimensional structures of this fascinating class of molecules and interactions, with reference to the relevant experimental data and techniques that are key for validation of the theoretical predictions.

Self-Assembly of a Double Hydrophilic Block Glycopolymer and the Investigation of Its Mechanism

We report the self-assembly of a double hydrophilic block glycopolymer (DHBG) via hydrogen bonding and coordinate bonding. This DHBG, composed of poly(ethylene)glycol (PEG) and glycopolymer, self-assembled into a well-defined structure. The DHBG was prepared through the controlled radical polymerization of trimethylsilyl-protected propargyl methacrylate using a PEG-based reversible addition-fragmentation chain transfer reagent, followed by sugar conjugation using click chemistry. The DHBG self-assembly capability was investigated by transmission electron microscopy and dynamic light scattering. Interestingly, the DHBG self-assembled into a spherical structure in aqueous solution. Hydrogen bonding and coordinate bonding with Ca²⁺ were identified as the driving forces for self-assembly.

Immobilization of glycans on solid surfaces for application in glycomics

Carbohydrates are an important class of biomolecules which are involved in a multitude of cellular functions. In the field of glycomics, the structure and function of various carbohydrates, oligosaccharides, glycans and their conjugates are constantly under investigation. In the continuing quest to understand the roles of carbohydrates in their interactions with proteins, immunogens, and other cell-surface carbohydrates, scientists have developed methods for observing the effects of specific saccharide sequences on various cellular components. Carbohydrate immobilization has allowed researchers to study the impact of specific sequences, leading to a deeper understanding of many cellular processes. The goal of this review is to highlight the chemical reactions and interactions that have been used for glycan immobilization.

Triggerable Multivalent Glyconanoparticles for Probing Carbohydrate-Carbohydrate Interactions

Carbohydrate-carbohydrate interactions are proposed to be biologically significant but have lower affinities than the well-studied carbohydrate-protein interactions. Here we introduce multivalent glyconanostructures where the surface expression of lactose can be triggered by an external stimulus, and a gold nanoparticle core enables colorimetric signal outputs to probe binding. Macromolecular engineering of a responsive polymer "gate" enables the lactose moieties to be presented only when an external stimulus is present, mimicking how nature uses enzymes to dynamically regulate glycan expression. Two different carbohydrate-carbohydrate interactions are investigated using this tool.

Multimerization of DAB-1 onto Au GNPs affords new potent and selective N-acetylgalactosamine-6-sulfatase (GALNS) inhibitors

Gold glyconanoparticles (Au GNPs) decorated with the natural iminosugar DAB-1 at different densities are reported.

Targeted photodynamic therapy of breast cancer cells using lactose-phthalocyanine functionalized gold nanoparticles

Gold nanoparticles (AuNPs), which have been widely used for the delivery of photosensitizers for photodynamic therapy (PDT) of cancer, can be dispersed in aqueous solutions improving the delivery of the hydrophobic photosensitizer into the body. Furthermore, the large surface of AuNPs can be functionalized with a variety of ligands, including proteins, nucleic acids and carbohydrates, that allow selective targeting to cancer tissue. In this study, gold nanoparticles were functionalized with a mixed monolayer of a zinc phthalocyanine and a lactose derivative. For the first time, a carbohydrate was used with a dual purpose, as the stabilizing agent of the gold nanoparticles in aqueous solutions and as the targeting agent for breast cancer cells. The functionalization of the phthalocyanine-AuNPs with lactose led to the production of water-dispersible nanoparticles that are able to generate singlet oxygen and effect cell death upon irradiation. The targeting ability of lactose of the lactose-phthalocyanine functionalized AuNPs was studied in vitro towards the galectin-1 receptor on the surface of breast cancer cells. The targeting studies showed the exciting potential of lactose as a specific targeting agent for galactose-binding receptors overexpressed on breast cancer cells.

Plasmon-Based Colorimetric Nanosensors for Ultrasensitive Molecular Diagnostics

Colorimetric detection of target analytes with high specificity and sensitivity is of fundamental importance to clinical and personalized point-of-care diagnostics. Because of their extraordinary optical properties, plasmonic nanomaterials have been introduced into colorimetric sensing systems, which provide significantly improved sensitivity in various biosensing applications. Here we review the recent progress on these plasmonic nanoparticles-based colorimetric nanosensors for ultrasensitive molecular diagnostics. According to their different colorimetric signal generation mechanisms, these plasmonic nanosensors are classified into two categories: (1) interparticle distance-dependent colorimetric assay based on target-induced forming cross-linking assembly/aggregate of plasmonic nanoparticles; and (2) size/morphology-dependent colorimetric assay by target-controlled growth/etching of the plasmonic nanoparticles. The sensing fundamentals and cutting-edge applications will be provided for each of them, particularly focusing on signal generation and/or amplification mechanisms that realize ultrasensitive molecular detection. Finally, we also discuss the challenge and give our future perspective in this emerging field.

Nano-carbohydrates: Synthesis and application in genetics, biotechnology, and medicine

Combining nanoparticles with carbohydrate has triggered an exponential growth of research activities for the design of novel functional bionanomaterials, nano-carbohydrates. Recent advances in versatile synthesis of glycosylated nanoparticles have paved the way towards diverse biomedical applications. The accessibility of a wide variety of these structured nanosystems, in terms of shape, size, and organization around stable nanoparticles, has readily contributed to their development and application in nanomedicine. Glycosylated gold nanoparticles, glycosylated quantum dots, fullerenes, single-wall nanotubes, and self-assembled glyconanoparticles using amphiphilic glycopolymers or glycodendrimers have received considerable attention for their application in powerful imaging, therapeutic, and biodiagnostic devices. Recently, nano-carbohydrates were used for different types of microarrays to detect proteins and nucleic acids.

1,4-Benzenediboronic-Acid-Induced Aggregation of Gold Nanoparticles: Application to Hydrogen Peroxide Detection and Biotin-Avidin-Mediated Immunoassay with Naked-Eye Detection

Hydrogen-peroxide (H2O2)-induced growth of small-sized gold nanoparticles (AuNPs) is often implemented for H2O2 sensing and plasmonic immunoassay. In contrast, there is little-to-no information in the literature regarding the application of H2O2-inhibited aggregation of citrate-capped AuNPs. This study discloses that benzene-1,4-diboronic acid (BDBA) was effective in driving the aggregation of citrate-capped AuNPs through an interaction between α-hydroxycarboxylate of citrate and boronic acids of BDBA. The H2O2-mediated oxidation of BDBA resulted in the conversion of boronic acid groups to phenol groups. The oxidized BDBA was incapable of triggering the aggregation of citrate-capped AuNPs. Thus, the presence of H2O2 prohibited BDBA-induced aggregation of citrate-capped AuNPs. The BDBA-induced aggregation of citrate-capped AuNPs can be paired with the glucose oxidase (GOx)-glucose system to design a colorimetric probe for glucose. Moreover, a H2O2·BDBA·AuNP probe was integrated with sandwich immunoassay, biotinylated antibody, and avidin-conjugated GOx for the selective naked-eye detection of rabbit immunoglobulin G (IgG) and human-prostate-specific antigen (PSA). The lowest detectable concentrations of rabbit IgG and human PSA by the naked eye were down to 0.1 and 4 ng/mL, respectively. More importantly, the proposed plasmonic immunoassay allowed the naked-eye quantification of 0-10 ng/mL PSA at an interval of 2 ng/mL in plasma samples.

Size-optimized galactose-capped gold nanoparticles for the colorimetric detection of heat-labile enterotoxin at nanomolar concentrations

The development of a galactose-capped gold nanoparticle-based colorimetric sensor for the detection of the lectin heat-labile enterotoxin is reported. Heat-labile enterotoxin is one of the pathogenic agents responsible for the intestinal disease called 'traveller's diarrhoea'. By means of specific interaction between galactose moieties attached to the surface of gold nanoparticles and receptors on the B-subunit of heat-labile enterotoxin (LTB), the gold nanoparticles reported here act as an efficient colorimetric sensor, which can detect the toxin at nanomolar concentrations. The effect of gold nanoparticle size on the detection sensitivity was investigated in detail. Amongst the various sizes of gold nanoparticles studied (2, 7, 12, and 20 nm), the 12 nm sized gold nanoparticles were found to be the most efficient, with a minimum heat-labile enterotoxin detection concentration of 100 nM. The red to purple colour change of the gold nanoparticle solution occurred within two minutes, indicating rapid toxin sensing.

Facile fabrication of glycopolymer-based iron oxide nanoparticles and their applications in the carbohydrate–lectin interaction and targeted cell imaging

A novel method for facile fabrication of glycopolymer-based iron oxide nanoparticles (GIONs) is developed.

Glyconanoparticles for colorimetric bioassays

Carbohydrate molecules are involved in many of the cellular processes that are important for life. By combining the specific analyte targeting of carbohydrates with the multivalent structure and change of solution colour as a consequence of plasmonic interactions with the aggregation of metal nanoparticles, glyconanoparticles have been used extensively for the development of bioanalytical assays. The noble metals used to create the nanocore, the methodologies used to assemble the carbohydrates on the nanoparticle surface, the carbohydrate chosen for each specific target, the length of the tether that separates the carbohydrate from the nanocore and the density of carbohydrates on the surface all impact on the structural formation of metal based glyconanoparticles. This tutorial review highlights these key components, which directly impact on the selectivity and sensitivity of the developed bioassay, for the colorimetric detection of lectins, toxins and viruses.

Novel bio-friendly and non-toxic thiocarbohydrate stabilizers of gold nanoparticles

A new class of stabilizers for gold nanoparticles has been develop with non-toxic thiocarbohydrates that were prepared from d-(+)-gluconic acid δ-lactone and aminoalkylthiols.

Evaluation of intermolecular association of glycosaminoglycan oligosaccharides using nanoelectrospray ionization mass spectrometry

This study examines the non-covalent interactions between glycosaminoglycan (GAG) oligosaccharides using nanoelectrospray ionization mass spectrometry (nanoESI-MS). It is the first time that interactions between oligosaccharides have been observed using MS. The importance of interactions between GAGs has recently attracted much interest because they are related to biological functions. For instance, hyaluronic acid (HA) is known to associate with chondroitin sulfates (CSs), although the details of the interaction remain unclear. In general, non-covalent interactions between glycans are too weak to detect by general means. In this work, we applied nanoESI-MS with high sensitivity, which is widely used to observe non-covalent interactions, to investigate the interaction between HA and CSs. HA and CS oligosaccharides are used to discuss the results in a simplified manner. Our approach is aimed at interpreting the behavior of GAG polysaccharides from the information obtained using the oligosaccharides. HA and CS tetrasaccharides were demonstrated to associate to form heterodimer ions that were easily detected using nanoESI-MS. We also determined the stoichiometry of the interaction and calculated the K(d) values of the interactions between HA and CS tetrasaccharides. How these structures affect the strength and stability of the non-covalent complexes is discussed. Further study of the interactions between HA and CS oligosaccharides will clarify the biological meaning of the coexistence of HA and CS in body fluids and tissues.

Visual detection of Ca2+based on aggregation-induced emission of Au(i)–Cys complexes with superb selectivity

An interesting Au(i)–Cys complex was employed for the optical detection of Ca²⁺based on an aggregation-induced emission phenomenon. This AIE property of Au(i)–thiol complexes may provide a universal sensing strategy by employing different mercapto-appended ligands.

Structural basis of multivalent galactose-based dendrimer recognition by human galectin-7

Galectins are evolutionarily conserved and ubiquitously present animal lectins with a high affinity for β-galactose-containing oligosaccharides. To date, 15 mammalian galectins have been identified. Their involvement in cell-cell and cell-matrix interactions has highlighted their importance in signal transduction and other intracellular processes. Human galectin-7 (hGal-7) is a 15 kDa proto type galectin that forms a dimer in solution and its involvement in the stimulation and development of tumour growth has been reported. Previously, we reported the crystal structure of hGal-7 and its complex with galactose and lactose which provided insight into its molecular recognition and detailed interactions. Here, we present newly obtained high-resolution structural data on carbohydrate-based dendrons in complex with hGal-7. Our crystallographic data reveal how multivalent ligands interact with and form cross-links with these galectin molecules. Understanding how these dendrimeric compounds interact with hGal-7 would help in the design of new tools to investigate the recognition of carbohydrates by lectins.

Visualization and quantification of neurochemicals with gold nanoparticles: opportunities and challenges

Gold nanoparticle (Au-NP)-based colorimetric assays offer new opportunitites for the visualization and quantification of neurochemicals involved in physiological and pathological processes due to their high sensitivity, designability, and low technical demands. In this Research News, we systematically review the advances on the development of Au-NP-based colorimetric methods for visualization and quantification of neurochemicals and their potential applications for effectively monitoring neurochemicals in the central nervous system. By integration of the favourable surface chemistry with the high extinction coefficient of Au-NPs, some new principles and methods could be developed for the quantification of neurochemicals involved in brain functions. New strategies to design the surface chemistry of Au-NPs, along with the key challenges yet to be addressed to achieve online visualization and quantification of neurochemicals in the central nervous system, are illustrated and discussed. The questions opened here should inspire future investigations and lead to discoveries that continue the development of the effective analytical protocols based on Au-NPs for neurochemical visualization and quantification.

Colorimetric detection of manganese(II) ions using gold/dopa nanoparticles

We report here a one-pot, greener, eco-friendly strategy for the synthesis of gold nanoparticles using L-dopa. The as-prepared dopa-functionalized gold nanoparticles (AuNPs/dopa) can detect low concentrations of manganese(II) metal ions in aqueous solution. The binding forces between dopa and Mn(2+) ions cause dopa-functionalized gold nanoparticles to come closer together, decreasing the interparticle distance and aggregating it with a change in color of colloidal solution from red to purplish-blue. Dynamic light scattering (DLS) analysis showed a decreased surface charge on the surface of gold nanoparticles when exposed to Mn(2+) ions, which caused cross-linking aggregation. Transmission electron microscopic (TEM) images also revealed the aggregation of gold nanoparticles with the addition of Mn(2+) ions. The extinction ratio of absorbance at 700-550nm (A700/A550) was linear against the concentration of [Mn(2+)] ions. Thus, the optical absorption spectra of gold colloidal solution before and after the addition of Mn(2+) ions reveal the concentration of Mn(2+) ions in solution.

Glyconanomaterials: Emerging applications in biomedical research

Carbohydrates constitute the most abundant organic matter in nature, serving as structural components and energy sources, and mediating a wide range of cellular activities. The emergence of nanomaterials with distinct optical, magnetic, and electronic properties has witnessed a rapid adoption of these materials for biomedical research and applications. Nanomaterials of various shapes and sizes having large specific surface areas can be used as multivalent scaffolds to present carbohydrate ligands. The resulting glyconanomaterials effectively amplify the glycan-mediated interactions, making it possible to use these materials for sensing, imaging, diagnosis, and therapy. In this review, we summarize the synthetic strategies for the preparation of various glyconanomaterials. Examples are given where these glyconanomaterials have been used in sensing and differentiation of proteins and cells, as well as in imaging glycan-medicated cellular responses.

Revisiting 30 years of biofunctionalization and surface chemistry of inorganic nanoparticles for nanomedicine

In the last 30 years we have assisted to a massive advance of nanomaterials in material science. Nanomaterials and structures, in addition to their small size, have properties that differ from those of larger bulk materials, making them ideal for a host of novel applications. The spread of nanotechnology in the last years has been due to the improvement of synthesis and characterization methods on the nanoscale, a field rich in new physical phenomena and synthetic opportunities. In fact, the development of functional nanoparticles has progressed exponentially over the past two decades. This work aims to extensively review 30 years of different strategies of surface modification and functionalization of noble metal (gold) nanoparticles, magnetic nanocrystals and semiconductor nanoparticles, such as quantum dots. The aim of this review is not only to provide in-depth insights into the different biofunctionalization and characterization methods, but also to give an overview of possibilities and limitations of the available nanoparticles.

Glyco-Inside Micelles and Vesicles Directed by Protection-Deprotection Chemistry

Protection-deprotection of carbohydrate is often required in the preparation of glycopolymers, which causes an obvious polarity change of the polymers, but it has been neglected in the studies of self-assembly. In this paper, a new strategy for self-assembly of sugar-containing block copolymers is suggested based on the protection-deprotection chemistry. We found that deacetylation of a series of block copolymers of PS-b-PManAc (PS, polystyrene block; PManAc, "sugar block" with acetylated α-mannopyranoside side groups) in THF resulted in glyco-inside structures of the deprotected copolymer PS-b-PMan, i.e., vesicles with a sugar wall and micelles with a sugar core. Besides, vesicle-to-micelle transition of the assemblies with decreasing the relative length of the sugar block was observed. These unique glyco-inside assemblies show interesting functions, such as generating homogeneous Au nanoparticles within the layer of the glyco-block from AuCl^4- without any additional reducing reagents or energy input. Control experiments prove that the polar layer of glyco-polymer inside the vesicle provides an essential reduction environment.