Amphiphilic gold nanoparticles displaying flexible bifurcated ligands as a carrier for siRNA delivery into the cell cytosol

Stimuli-Responsive Adaptive Nanotoxin to Directly Penetrate the Cellular Membrane by Molecular Folding and Unfolding

Biological nanomachines, including proteins and nucleic acids whose function is activated by conformational changes, are involved in every biological process, in which their dynamic and responsive behaviors are controlled by supramolecular recognition. The development of artificial nanomachines that mimic the biological functions for potential application as therapeutics is emerging; however, it is still limited to the lower hierarchical level of the molecular components. In this work, we report a synthetic machinery nanostructure in which actuatable molecular components are integrated into a hierarchical nanomaterial in response to external stimuli to regulate biological functions. Two nanometers core-sized gold nanoparticles are covered with ligand layers as actuatable components, whose folding/unfolding motional response to the cellular environment enables the direct penetration of the nanoparticles across the cellular membrane to disrupt intracellular organelles. Furthermore, the pH-responsive conformational movements of the molecular components can induce the apoptosis of cancer cells. This strategy based on the mechanical motion of molecular components on a hierarchical nanocluster would be useful to design biomimetic nanotoxins.

Engineering the Interface between Inorganic Nanoparticles and Biological Systems through Ligand Design

Nanoparticles (NPs) provide multipurpose platforms for a wide range of biological applications. These applications are enabled through molecular design of surface coverages, modulating NP interactions with biosystems. In this review, we highlight approaches to functionalize nanoparticles with "small" organic ligands (Mw < 1000), providing insight into how organic synthesis can be used to engineer NPs for nanobiology and nanomedicine.

Understanding cellular interactions with nanomaterials: towards a rational design of medical nanodevices

Biomedical applications increasingly require fully characterized new nanomaterials. There is strong evidence showing that nanomaterials not only interact with cells passively but also actively, mediating essential molecular processes for the regulation of cellular functions, but we are only starting to understand the mechanisms of those interactions. Systematic studies about cell behavior as a response to specific nanoparticle properties are scarce in the literature even when they are necessary for the rational design of medical nanodevices. Information in the literature shows that the physicochemical properties determine the bioactivity, biocompatibility, and safety of nanomaterials. The information available regarding the interaction and responses of cells to nanomaterials has not been analyzed and discussed in a single document. Hence, in this review, we present the latest advances about cellular responses to nanomaterials and integrate the available information into concrete considerations for the development of innovative, efficient, specific and, more importantly, safe biomedical nanodevices. We focus on how physicochemical nanoparticle properties (size, chemical surface, shape, charge, and topography) influence cell behavior in a first attempt to provide a practical guide for designing medical nanodevices, avoiding common experimental omissions that may lead to data misinterpretation. Finally, we emphasize the importance of the systematic study of nano-bio interactions to acquire sufficient reproducible information that allows accurate control of cell behavior based on tuning of nanomaterial properties. This information is useful to guide the design of specific nanodevices and nanomaterials to elicit desired cell responses, like targeting, drug delivery, cell attachment, differentiation, etc, or to avoid undesired side effects.

Non-cationic Material Design for Nucleic Acid Delivery

Nucleic acid delivery provides effective options to control intracellular gene expression and protein production. Efficient delivery of nucleic acid typically requires delivery vehicles to facilitate the entry of nucleic acid into cells. Among non-viral delivery vehicles, cationic materials are favored because of their high loading capacity of nucleic acids and prominent cellular uptake efficiency through electrostatic interaction. However, cationic moieties at high dosage tend to induce severe cytotoxicity due to the interference on cell membrane integrity. In contrast, non-cationic materials present alternative delivery approaches with less safety concerns than cationic materials. In this Progress Report, principles of non-cationic material design for nucleic acid delivery are discussed. Examples of such non-cationic platforms are highlighted, including complexation or conjugation with nucleic acids and self-assembled nucleic acid structures.

Current status and future perspectives of gold nanoparticle vectors for siRNA delivery

Discovering the vast therapeutic potential of siRNA opened up new clinical research areas focussing on a number of diseases and applications; however significant problems with siRNA stability and delivery have hindered its clinical applicability. As a result, interest in the development of practical siRNA delivery systems has grown in recent years. Of the numerous siRNA delivery strategies currently on offer, gold nanoparticles (AuNPs) stand out thanks to their biocompatibility and capacity to protect siRNA against degradation; not to mention the versatility offered by their tuneable shape, size and optical properties. Herein this review provides a complete summary of the methodologies for functionalizing AuNPs with siRNA, paying singular attention to the AuNP shape, size and surface coating, since these key factors heavily influence cellular interaction, internalization and, ultimately, the efficacy of the hybrid particle. The most noteworthy hybridization strategies have been highlighted along with the most innovative and outstanding in vivo studies with a view to increasing clinical interest in the use of AuNPs as siRNA nanocarriers.

Shape-dependent adjuvanticity of nanoparticle-conjugated RNA adjuvants for intranasal inactivated influenza vaccines

Conjugation with gold nanorods enhanced the adjuvanticity of RNA adjuvant for intranasal inactivated influenza vaccines, providing efficient protection against infection in mice.

Hydrophobic and Hydrophilic Au and Ag Nanoparticles. Breakthroughs and Perspectives

This review provides a broad look on the recent investigations on the synthesis, characterization and physico-chemical properties of noble metal nanoparticles, mainly gold and silver nanoparticles, stabilized with ligands of different chemical nature. A comprehensive review of the available literature in this field may be far too large and only some selected representative examples will be reported here, together with some recent achievements from our group, that will be discussed in more detail. Many efforts in finding synthetic routes have been performed so far to achieve metal nanoparticles with well-defined size, morphology and stability in different environments, to match the large variety of applications that can be foreseen for these materials. In particular, the synthesis and stabilization of gold and silver nanoparticles together with their properties in different emerging fields of nanomedicine, optics and sensors are reviewed and briefly commented.

Amphiphilic N-Heterocyclic Carbene-Stabilized Gold Nanoparticles and Their Self-Assembly in Polar Solvents

Soft matter-directed self-assembly of amphiphilic inorganic nanoparticles (NPs) has recently emerged as a promising approach to access NP ensembles with superior collective properties. While thiol-terminated molecules are primarily employed to tether the amphiphilic ligand to the metal, concerns remain regarding the stabilities of the resulting NPs and their corresponding aggregates. As an alternative, we report amphiphilic N-heterocyclic carbene (NHC)-functionalized gold nanoparticles (AuNPs). To accomplish this, an amphiphilic NHC-Au^I complex based on an asymmetric triethylene glycol-/dodecyl-functionalized benzimidazole was first synthesized and used to prepare the corresponding stable amphiphilic NHC-decorated AuNPs. The resulting NPs were comprehensively characterized using both solution- and solid-state-based techniques such as proton nuclear magnetic resonance spectroscopy, dynamic light scattering, transmission electron microscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy. By optimizing the self-assembly behavior of these amphiphilic AuNPs in deionized water, ethanol, and their mixtures, we were able to fine-tune the plasmonic properties of the AuNPs in the wide range of 525-640 nm. Furthermore, when treated with thiols, the ensembles showed greater stability compared to their parent discrete AuNP counterparts at room temperature.

Enhanced Fluorescence ELISA Based on HAT Triggering Fluorescence "Turn-on" with Enzyme-Antibody Dual Labeled AuNP Probes for Ultrasensitive Detection of AFP and HBsAg

At present, enzyme-linked immunosorbent assay (ELISA) is considered to be the most appropriate approach in clinical biomarker detection, with good specificity, low cost, and straightforward readout. However, unsatisfactory sensitivity severely hampers its wide application in clinical diagnosis. Herein, we designed a new kind of enhanced fluorescence enzyme-linked immunosorbent assay (FELISA) based on the human alpha-thrombin (HAT) triggering fluorescence "turn-on" signals. In this system, detection antibodies (Ab₂) and HAT were labeled on the gold nanoparticles (AuNPs) to form the detection probes, and a bisamide derivative of Rhodamine₁₁₀ with fluorescence quenched served as the substrate of HAT. After the sandwich immunoreaction, HAT on the sandwich structure could catalyze the cleavage of the fluorescence-quenched substrate, leading to a strong fluorescence signal for sensing ultralow levels of alpha fetoprotein (AFP) and hepatitis B virus surface antigen (HBsAg). Under the optimized reaction conditions, AFP and HBsAg were detected at the ultralow concentrations of 10^-8 ng mL^-1 and 5 × 10^-4 IU mL^-1, respectively, which were at least 10⁴ times lower than those of the conventional fluorescence assay and 10⁶ times lower than those of the conventional ELISA. In addition, we further discussed the efficiency of the sensitive FELISA in clinical serum samples, showing great potential in practical applications.

Recent advances in siRNA delivery

In the 1990s an unexpected gene-silencing phenomena in plants, the later called RNA interference (RNAi), perplexed scientists. Following the proof of activity in mammalian cells, small interfering RNAs (siRNAs) have quickly crept into biomedical research as a new powerful tool for the potential treatment of different human diseases based on altered gene expression. In the past decades, several promising data from ongoing clinical trials have been reported. However, despite surprising successes in many pre-clinical studies, concrete obstacles still need to be overcome to translate therapeutic siRNAs into clinical reality. Here, we provide an update on the recent advances of RNAi-based therapeutics and highlight novel synthetic platforms for the intracellular delivery of siRNAs.

In-depth study on the gene silencing capability of silica nanoparticles with different pore sizes: degree and duration of RNA interference

The mesoporous silica nanoparticles (MSN) having different pore sizes were synthesized and utilized for siRNA delivery system capable of controlling kinetics of RNA interference.

Influence of the size and charge of gold nanoclusters on complexation with siRNA: a molecular dynamics simulation study

The complexation of siRNA with positively charged gold nanoclusters has been studied using classical molecular dynamics simulations.