In vitro transcription and translation inhibition via DNA functionalized gold nanoparticles

Role of Tunable Gold Nanostructures in Cancer Nanotheranostics: Implications on Synthesis, Toxicity, Clinical Applications and Their Associated Opportunities and Challenges

The existing diagnosis and treatment modalities have major limitations related to their precision and capability to understand several stages of disease development. A superior therapeutic system consists of a multifunctional approach in early diagnosis of the disease with a simultaneous progressive cure, using a precise medical approach towards complex treatment. These challenges can be addressed via nanotheranostics and explore suitable approaches to improve health care. Nanotechnology in combination with theranostics as an unconventional platform paved the way for developing novel strategies and modalities leading to diagnosis and therapy for complex disease conditions, ranging from acute to chronic levels. Among the metal nanoparticles, gold nanoparticles are being widely used for theranostics due to their inherent non-toxic nature and plasmonic properties. The unique optical and chemical properties of plasmonic metal nanoparticles along with theranostics have led to a promising era of plausible early detection of disease conditions, and they enable real-time monitoring with enhanced non-invasive or minimally invasive imaging of several ailments. This review aims to highlight the improvement and advancement brought to nanotheranostics by gold nanoparticles in the past decade. The clinical use of the metal nanoparticles in nanotheranostics is explained, along with the future perspectives on addressing the key applications related to diagnostics and therapeutics, respectively. The scope of gold nanoparticles and their realistic potential to design a sophisticated theranostic system is discussed in detail, along with their implications in clinical advancements which are the needs of the hour. The review concluded with the challenges, opportunities, and implications on translational potential of using gold nanoparticles in nanotheranostics.

Nanoalumina triggers the antibiotic persistence of Escherichia coli through quorum sensing regulators lrsF and qseB

Nanomaterials with bactericidal effects might provide novel strategies against bacteria. However, some bacteria can survive despite the exposure to nanomaterials, which challenges the safety of antibacterial nanomaterials. Here, we used a high dose of antibiotics to kill the E. coli. that survived under different concentrations of nanoalumina treatment to screen persisters, and found that nanoalumina could significantly trigger persisters formation. Treatment with 50 mg/L nanoalumina for 4 h resulted in the formation of (0.084 ± 0.005) % persisters. Both reactive oxygen species (ROS) and toxin-antitoxin (TA) system were involved in persisters formation. Interestingly, RT-PCR analysis and knockout of the five genes related to ROS and TA confirmed that only hipB was associated with the formation of persisters, suggesting the involvement of other mechanisms. We further identified 73 differentially expressed genes by transcriptome sequencing and analyzed them with bioinformatics tools. We selected six candidate genes and verified that five of them closely related to quorum sensing (QS) that were involved in persisters formation, and further validated that the coexpression of QS factors lrsF and qseB was a novel pathway for persisters. Our findings provided a better understanding on the emergence of bacterial persistence and the microbial behavior under nanomaterials exposure.

Highly extended filaments in aqueous gold nano-particle colloidals

A new regime of filamentation has been discovered in aqueous gold nanoparticle colloidals (AGNC). Different from filamentation in liquids, in this regime, by doping water with gold nanoparticles, there is no observable multiple small-scale filaments, but instead a spatially continuous plasma channel is formed. The length of the filament is more than ten times as compared with that in water. Filamentation in AGNC is characterized by a colorful light channel, with generated supercontinuum ranging from 400 nm to 650 nm which is scattered along a cyan-orange path.

Smuggling gold nanoparticles across cell types - A new role for exosomes in gene silencing

Once released to the extracellular space, exosomes enable the transfer of proteins, lipids and RNA between different cells, being able to modulate the recipient cells' phenotypes. Members of the Rab small GTP-binding protein family, such as RAB27A, are responsible for the coordination of several steps in vesicle trafficking, including budding, mobility, docking and fusion. The use of gold nanoparticles (AuNPs) for gene silencing is considered a cutting-edge technology. Here, AuNPs were functionalized with thiolated oligonucleotides anti-RAB27A (AuNP@PEG@anti-RAB27A) for selective silencing of the gene with a consequent decrease of exosomes´ release by MCF-7 and MDA-MB-453 cells. Furthermore, communication between tumor and normal cells was observed both in terms of alterations in c-Myc gene expression and transportation of the AuNPs, mediating gene silencing in secondary cells.

Tumor Microenvironment Modulation via Gold Nanoparticles Targeting Malicious Exosomes: Implications for Cancer Diagnostics and Therapy

Exosomes are nanovesicles formed in the endosomal pathway with an important role in paracrine and autocrine cell communication. Exosomes secreted by cancer cells, malicious exosomes, have important roles in tumor microenvironment maturation and cancer progression. The knowledge of the role of exosomes in tumorigenesis prompted a new era in cancer diagnostics and therapy, taking advantage of the use of circulating exosomes as tumor biomarkers due to their stability in body fluids and targeting malignant exosomes’ release and/or uptake to inhibit or delay tumor development. In recent years, nanotechnology has paved the way for the development of a plethora of new diagnostic and therapeutic platforms, fostering theranostics. The unique physical and chemical properties of gold nanoparticles (AuNPs) make them suitable vehicles to pursuit this goal. AuNPs’ properties such as ease of synthesis with the desired shape and size, high surface:volume ratio, and the possibility of engineering their surface as desired, potentiate AuNPs’ role in nanotheranostics, allowing the use of the same formulation for exosome detection and restraining the effect of malicious exosomes in cancer progression.

Cancer Cell Internalization of Gold Nanostars Impacts Their Photothermal Efficiency In Vitro and In Vivo: Toward a Plasmonic Thermal Fingerprint in Tumoral Environment

Gold nanoparticles are prime candidates for cancer thermotherapy. However, while the ultimate target for nanoparticle-mediated photothermal therapy is the cancer cell, heating performance has not previously been evaluated in the tumoral environment. A systematic investigation of gold nanostar heat-generating efficiency in situ is presented: not only in cancer cells in vitro but also after intratumoral injection in vivo. It is demonstrated that (i) in aqueous dispersion, heat generation is governed by particle size and exciting laser wavelength; (ii) in cancer cells in vitro, heat generation is still very efficient, but irrespective of both particle size and laser wavelength; and (iii) heat generation by nanostars injected into tumors in vivo evolves with time, as the nanostars are trafficked from the extracellular matrix into endosomes. The plasmonic heating response thus serves as a signature of nanoparticle internalization in cells, bringing the ultimate goal of nanoparticle-mediated photothermal therapy a step closer.

Gold Nanotheranostics: Proof-of-Concept or Clinical Tool?

Nanoparticles have been making their way in biomedical applications and personalized medicine, allowing for the coupling of diagnostics and therapeutics into a single nanomaterial—nanotheranostics. Gold nanoparticles, in particular, have unique features that make them excellent nanomaterials for theranostics, enabling the integration of targeting, imaging and therapeutics in a single platform, with proven applicability in the management of heterogeneous diseases, such as cancer. In this review, we focus on gold nanoparticle-based theranostics at the lab bench, through pre-clinical and clinical stages. With few products facing clinical trials, much remains to be done to effectively assess the real benefits of nanotheranostics at the clinical level. Hence, we also discuss the efforts currently being made to translate nanotheranostics into the market, as well as their commercial impact.

Bioresponsive antisense DNA gold nanobeacons as a hybrid in vivo theranostics platform for the inhibition of cancer cells and metastasis

Gold nanobeacons can be used as a powerful tool for cancer theranostics. Here, we proposed a nanomaterial platform based on gold nanobeacons to detect, target and inhibit the expression of a mutant Kras gene in an in vivo murine gastric cancer model. The conjugation of fluorescently-labeled antisense DNA hairpin oligonucleotides to the surface of gold nanoparticles enables using their localized surface plasmon resonance properties to directly track the delivery to the primary gastric tumor and to lung metastatic sites. The fluorescently labeled nanobeacons reports on the interaction with the target as the fluorescent Cy3 signal is quenched by the gold nanoparticle and only emit light following conjugation to the Kras target owing to reorganization and opening of the nanobeacons, thus increasing the distance between the dye and the quencher. The systemic administration of the anti-Kras nanobeacons resulted in approximately 60% tumor size reduction and a 90% reduction in tumor vascularization. More important, the inhibition of the Kras gene expression in gastric tumors prevents the occurrence of metastasis to lung (80% reduction), increasing mice survival in more than 85%. Our developed platform can be easily adjusted to hybridize with any specific target and provide facile diagnosis and treatment for neoplastic diseases.

Strategies for the biofunctionalization of gold and iron oxide nanoparticles

The field of nanotechnology applied to medicine (nanomedicine) is developing at a fast pace and is expected to provide solutions for early diagnosis, targeted therapy, and personalized medicine. However, designing nanomaterials for biomedical applications is not a trivial task. Avoidance of the immune system, stability in physiological media, control over the interaction of a nanomaterial with biological entities such as proteins and cell membranes, low toxicity, and optimal bioperformance are critical for the success of the designed nanomaterial. In this Feature Article we provide a concise overview of some of the most recent advances concerning the derivatization of gold and iron oxide nanoparticles for bioapplications. The most important aspects relating to the functionalization of gold and iron oxide nanoparticles with carbohydrates, peptides, nucleic acids, and antibodies are covered, highlighting the recent contributions from our research group. We suggest tips for the appropriate (bio)functionalization of these inorganic nanoparticles in order to preserve the biological activity of the attached biomolecules and ensure their subsequent stability in physiological media.

Miktoarm star conjugated multifunctional gold nanoshells: synthesis and an evaluation of biocompatibility and cellular uptake

A simple and highly versatile click chemistry based synthetic strategy to develop an ABC type miktoarm star ligand that is conjugated to gold nanoshells (GNS) is reported. The surface functionalized multifunctional GNS contain lipoic acid (LA) as a model therapeutic agent, poly(ethylene glycol) (PEG₃₅₀) as a solubilizing and stealth agent, and tetraethylene glycol (TEG) with a terminally conjugated thiol moiety. These GNS have an average size of 40 nm, a shell thickness of 6 nm, a well-defined crystal structure lattice (111), and a surface absorption plasmon band in the near infrared (NIR) region. The miktoarm star and GNS functionalized with this ligand are non-cytotoxic for up to 5 μg mL^-1 concentrations, and human umbilical vein endothelial cells internalize more than 85% of these GNS at 5 μg mL^-1. Our results establish that the biocompatible miktoarm star ligand provides a useful platform to synthetically articulate the introduction of multiple functions onto GNS, and enhance their scope by combining their inherent imaging capabilities with efficient delivery and accumulation of active therapeutic agents.

Gold-nanobeacons for gene therapy: evaluation of genotoxicity, cell toxicity and proteome profiling analysis

Antisense therapy is a powerful tool for post-transcriptional gene silencing suitable for down-regulating target genes associated to disease. Gold nanoparticles have been described as effective intracellular delivery vehicles for antisense oligonucleotides providing increased protection against nucleases and targeting capability via simple surface modification. We constructed an antisense gold-nanobeacon consisting of a stem-looped oligonucleotide double-labelled with 3'-Cy3 and 5'-Thiol-C6 and tested for the effective blocking of gene expression in colorectal cancer cells. Due to the beacon conformation, gene silencing was directly detected as fluorescence increases with hybridisation to target, which can be used to assess the level of silencing. Moreover, this system was extensively evaluated for the genotoxic, cytotoxic and proteomic effects of gold-nanobeacon exposure to cancer cells. The exposure was evaluated by two-dimensional protein electrophoresis followed by mass spectrometry to perform a proteomic profile and 3-(4,5-Dimethylthiazol-2-Yl)-2,5-Diphenyltetrazolium Bromide (MTT) assay, glutathione-S-transferase assay, micronucleus test and comet assay to assess the genotoxicity. This integrated toxicology evaluation showed that the proposed nanotheranostics strategy does not exhibit significant toxicity, which is extremely relevant when translating into in vivo systems.

Gold-nanobeacons for simultaneous gene specific silencing and intracellular tracking of the silencing events

The potential of a single molecular nanoconjugate to intersect all RNA pathways: from gene specific downregulation to silencing the silencers, i.e. siRNA and miRNA pathways, is demonstrated. Gold-nanobeacons are capable of efficiently silencing single gene expression, exogenous siRNA and endogenous miRNAs while yielding a quantifiable fluorescence signal directly proportional to the level of silencing. The silencing potential is comparable to that of traditional siRNA but the same nanoconjugates structure is also capable of reversing the effect of an exogenous siRNA. We further demonstrate the Gold-nanobeacons' efficiency at targeting and silencing miR-21, an endogenous miRNA involved in cancer development, which could become a valid nanotheranostics approach. Again, expression of miR-21 was inhibited with concomitant increase of the Au-nanobeacons' fluorescence that can be used to assess the silencing effect. This way, a single nanostructure can be used to intersect all RNA regulatory pathways while allowing for direct assessment of effective silencing and cell localization via a quantifiable fluorescence signal, making cancer nanotheranostics possible.

Functionalized Gold Nanoparticles and Their Biomedical Applications

Metal nanoparticles are being extensively used in various biomedical applications due to their small size to volume ratio and extensive thermal stability. Gold nanoparticles (GNPs) are an obvious choice due to their amenability of synthesis and functionalization, less toxicity and ease of detection. The present review focuses on various methods of functionalization of GNPs and their applications in biomedical research. Functionalization facilitates targeted delivery of these nanoparticles to various cell types, bioimaging, gene delivery, drug delivery and other therapeutic and diagnostic applications. This review is an amalgamation of recent advances in the field of functionalization of gold nanoparticles and their potential applications in the field of medicine and biology.