Design and applications of gold nanoparticle conjugates by exploiting biomolecule-gold nanoparticle interactions

Engineered nanoparticles for precise targeted drug delivery and enhanced therapeutic efficacy in cancer immunotherapy

The advent of cancer immunotherapy has imparted a transformative impact on cancer treatment paradigms by harnessing the power of the immune system. However, the challenge of practical and precise targeting of malignant cells persists. To address this, engineered nanoparticles (NPs) have emerged as a promising solution for enhancing targeted drug delivery in immunotherapeutic interventions, owing to their small size, low immunogenicity, and ease of surface modification. This comprehensive review delves into contemporary research at the nexus of NP engineering and immunotherapy, encompassing an extensive spectrum of NP morphologies and strategies tailored toward optimizing tumor targeting and augmenting therapeutic effectiveness. Moreover, it underscores the mechanisms that NPs leverage to bypass the numerous obstacles encountered in immunotherapeutic regimens and probes into the combined potential of NPs when co-administered with both established and novel immunotherapeutic modalities. Finally, the review evaluates the existing limitations of NPs as drug delivery platforms in immunotherapy, which could shape the path for future advancements in this promising field.

Sandwich-type aptamer-based biosensors for thrombin detection

Thrombin, a proteolytic enzyme, plays an essential role in catalyzing many blood clotting reactions. Thrombin can act as a marker for some blood-related diseases, such as leukemia, thrombosis, Alzheimer's disease and liver disease. Therefore, its diagnosis is of great importance in the fields of biological and medical research. Biosensors containing sandwich-type structures have attracted much consideration owing to their superior features such as reproducible and stable responses with easy improvement in the sensitivity of detection. Sandwich-type platforms can be designed using a pair of receptors that are able to bind to diverse locations of the same target. Herein, we investigate recent advances in the progress and applications of thrombin aptasensors containing a sandwich-type structure, in which two thrombin-binding aptamers (TBAs) identify different parts of the thrombin molecule, leading to the formation of a sandwich structure and ultimately signal detection. We also discuss the pros and cons of these approaches and outline the most logical approach in each section.

A comprehensive review of cancer therapies mediated by conjugated gold nanoparticles with nucleic acid

Nucleic acids provide a promising therapeutic platform by targeting various cell signaling pathways involved in cancer and genetic disorders. However, maintaining optimal stability during delivery limits their utility. Nucleic acid delivery vehicles are generally categorized into biological and synthetic carriers. Regardless of the efficiency of biological vectors, such as viral vectors, issues related to their immunogenicity and carcinogenesis are very important and vital for clinical applications. On the other hand, synthetic vectors such as lipids or polymers, have been widely used for nucleic acid delivery. Despite their transfection efficiency, low storage stability, targeting inefficiency, and tracking limitations are among the limitations of the clinical application of these vectors. In the past decades, gold nanoparticles with unique properties have been shown to be highly efficient mineral vectors for overcoming these obstacles. In this review, we focus on gold nanoparticle-nucleic acid combinations and highlight their use in the treatment of various types of cancers. Furthermore, by stating the biological applications of these structures, we will discuss their clinical applications.

Identification of Proteins Using Supramolecular Gold Nanoparticle-Dye Sensor Arrays

The rapid detection of proteins is very important in the early diagnosis of diseases. Gold nanoparticles (AuNPs) can be engineered to bind biomolecules efficiently and differentially. Cross-reactive sensor arrays have high sensitivity for sensing proteins using differential interactions between sensor elements and bioanalytes. A new sensor array was fabricated using surface-charged AuNPs with dyes supramolecularly encapsulated into the AuNP monolayer. The fluorescence of dyes is partially quenched by the AuNPs and can be restored or further quenched due to the differential interactions between AuNPs with proteins. This sensing system enables the discrimination of proteins in both buffer and human serum, providing a potential tool for real-world disease diagnostics.

Conjugation monitoring of gold nanoparticles with alkanedithiols by capillary zone electrophoresis

Alkanedithiols were used for the conjugation of gold nanoparticles (AuNP) prepared by a solution plasma process. Capillary zone electrophoresis was utilized for the monitoring of the conjugated AuNP. When 1,6-hexanedithiol (HDT) was used as a linker, a resolved peak from the AuNP was detected in the electropherogram; the resolved peak was attributed to the conjugated AuNP. The resolved peak was developed with increasing concentrations of HDT, while the peak of the AuNP decreased complementary. The resolved peak also tended to develop along with the standing time at least up to 7 weeks. The electrophoretic mobility of the conjugated AuNP was almost identical over the HDT concentrations examined, suggesting that the conjugation of the AuNP did not proceed further, such as aggregate/agglomerate formation. The conjugation monitoring was also examined with some dithiols and monothiols. Resolved peak of the conjugated AuNP was also detected with 1,2-ethanedithiol and 2-aminoethanethiol.

Role of Au-Sn bonding for stabilizing a gold nanocatalyst: a reinvestigation of purple of Cassius

Purple of Cassius is a pigment based on a gold colloid that has been known for hundreds of years. It has had a profound influence on modern nanoscience. But the origin of the small size of the Au nanoparticles (NPs) and their superior stability remains ambiguous. The experiments and characterization studies discussed here confirmed that SnCl₂ functioned not only as a reducing agent but also as an effective surface capping agent through bimetallic Au-Sn bonding. This finding expands the types of Au NP stabilizer from traditional organic examples (e.g., thiolate or phosphine) to metallic examples. The formation of a Au-Sn interface also endows Au NPs with excellent activity and separability for the hydration of alkynes to ketones.

Nanotechnology in drug and gene delivery

Over the last decade, nanotechnology has widely addressed many nanomaterials in the biomedical area with an opportunity to achieve better-targeted delivery, effective treatment, and an improved safety profile. Nanocarriers have the potential property to protect the active molecule during drug delivery. Depending on the employing nanosystem, the delivery of drugs and genes has enhanced the bioavailability of the molecule at the disease site and exercised an excellent control of the molecule release. Herein, the chapter discusses various advanced nanomaterials designed to develop better nanocarrier systems used to face different diseases such as cancer, heart failure, and malaria. Furthermore, we demonstrate the great attention to the promising role of nanocarriers in ease diagnostic and biodistribution for successful clinical cancer therapy.

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.

Surface functionalization of nanomaterials by aryl diazonium salts for biomedical sciences

Nanoparticles (NPs) can be prepared by simple reactions and methods from a number of materials. Their small size opens up a number of applications in different fields, among which biomedicine, including: i) drug delivery, ii) biosensors, iii) bioimaging, iv) antibacterial activity. To be able to perform such tasks, NPs must be modified with a variety of functional molecules, such as drugs, targeting groups, chemical tags or antibacterial agents, and must also be prevented from aggregation. The attachment must be stable to resist during the transportation to the targeted location. Diazonium salts, which have been widely used for coupling applications and surface modification, fulfil such criteria. Moreover, they are simple to prepare and can be easily substituted with a large number of organic groups. This review describes the use of these compounds in nanomedicine with a focus on the construction of nanohybrids derived from metal, oxide and carbon-based NPs as well as viruses.

Self-Assembly of 2D Gold Nanoparticle Superlattice in a Polymer Vesicle Layer Driven by Hydrophobic Interaction

Self-assembly of gold nanoparticles (AuNPs) into highly ordered superstructures provides a promising route toward fabricating materials with new functionalities or enhanced physical properties. Although self-assembly of AuNPs has garnered significant research attention recently, a highly ordered superlattice of AuNPs under a low concentration in a confined geometry formed by nonfunctionalized materials has not been reported. Herein, we investigate the self-assembly of a 2D AuNPs superlattice in a polymer vesicle layer using hydrophobic interactions, which exhibits centered rectangular lattice symmetry. To create the highly ordered AuNPs superlattice, the P(EG_x-b-iPGE_y) block copolymers that form the thickness of the hydrophobic vesicle layer comparable to the size of the AuNP are used as a template to control the AuNP degree of freedom. To the best of our knowledge, this study provides the first demonstration of a centered rectangular structure formation of AuNPs at the vesicle layer in 2D confined geometry.

On the Metal-Aided Catalytic Mechanism for Phosphodiester Bond Cleavage Performed by Nanozymes

Recent studies have shown that gold nanoparticles (AuNPs) functionalized with Zn(II) complexes can cleave phosphate esters and nucleic acids. Remarkably, such synthetic nanonucleases appear to catalyze metal (Zn)-aided hydrolytic reactions of nucleic acids similar to metallonuclease enzymes. To clarify the reaction mechanism of these nanocatalysts, here we have comparatively analyzed two nanonucleases with a >10-fold difference in the catalytic efficiency for the hydrolysis of the 2-hydroxypropyl-4-nitrophenylphosphate (HPNP, a typical RNA model substrate). We have used microsecond-long atomistic simulations, integrated with NMR experiments, to investigate the structure and dynamics of the outer coating monolayer of these nanoparticles, either alone or in complex with HPNP, in solution. We show that the most efficient one is characterized by coating ligands that promote a well-organized monolayer structure, with the formation of solvated bimetallic catalytic sites. Importantly, we have found that these nanoparticles can mimic two-metal-ion enzymes for nucleic acid processing, with Zn ions that promote HPNP binding at the reaction center. Thus, the two-metal-ion-aided hydrolytic strategy of such nanonucleases helps in explaining their catalytic efficiency for substrate hydrolysis, in accordance with the experimental evidence. These mechanistic insights reinforce the parallelism between such functionalized AuNPs and proteins toward the rational design of more efficient catalysts.

Triple signal amplification strategy for the ultrasensitive electrochemical detection of human papillomavirus 16 E6/E7 mRNA

Human papilloma virus (HPV) is the primary causative agent of cervical, vaginal, and vulvar cancers. HPV E6/E7 mRNA detection has been proven to improve the specificity and positive predictive value compared with HPV DNA testing in screening, whereby, it may possess higher diagnostic potential. Herein, to establish the ultrasensitive and specific detection of HPV E6/E7 mRNA, we developed a novel triple signal amplification strategy, combined with gold nanoparticles (AuNPs), reverse transcription loop-mediated isothermal amplification (RT-LAMP) and high affinity biotin-avidin system. This novel proposed signal amplification strategy exhibits the desired detection limit of 0.08 fM (approximately 100 copies) and a wide linear range from 0.1 pmol/mL to 100 nmol/mL for HPV16 E6/E7 mRNA detection. Importantly, the present novel biosensor is 10-100 times more sensitive than conventional RT-PCR in detecting HPV16 E6/E7 mRNA positive clinical samples. Conclusively, this biosensor shows good stability, selectivity, and reproducibility, which demonstrates its potential in future clinical diagnosis with desirable sensitivity and specificity.

Combining Gold Nanoparticles with Other Radiosensitizing Agents for Unlocking the Full Potential of Cancer Radiotherapy

About half of cancer patients (50%) receive radiotherapy (RT) for the treatment of local tumors. However, one of the main obstacles in RT is the close proximity of adjacent organs at risk, resulting in treatment doses being limited by significant tissue toxicity, hence preventing the necessary dose escalation that would guarantee local control. Effective local cancer therapy is needed to avoid progression of tumors and to decrease the development of systemic metastases which may further increase the possibility of resection. In an effort to do so, radiosensitizing agents are introduced to further increase damage to the tumor while minimizing normal tissue toxicity. Cisplatin and docetaxel (DTX) are currently being used as radiation dose enhancers in RT. Recent research shows the potential of gold nanoparticles (GNPs) as a radiosensitizing agent. GNPs are biocompatible and have been tested in phase I clinical trials. The focus will be on exploring the effects of adding other radiosensitizing agents such as DTX and cisplatin to the GNP-RT platform. Therefore, a combined use of local radiosensitizing agents, such as GNPs, with currently available radiosensitizing drugs could make a significant impact in future RT. The ultimate goal is to develop treatments that have limited or nonexistent side effects to improve the quality of life of all cancer patients.

Glyco-nanoparticles: New drug delivery systems in cancer therapy

Cancer is known as one of the most common diseases that are associated with high mobility and mortality in the world. Despite several efforts, current cancer treatment modalities often are highly toxic and lack efficacy and specificity. However, the application of nanotechnology has led to the development of effective nanosized drug delivery systems which are highly selective for tumors and allow a slow release of active anticancer agents. Different Nanoparticles (NPs) such as the silicon-based nano-materials, polymers, liposomes and metal NPs have been designed to deliver anti-cancer drugs to tumor sites. Among different drug delivery systems, carbohydrate-functionalized nanomaterials, specially based on their multi-valent binding capacities and desirable bio-compatibility, have attracted considerable attention as an excellent candidate for controlled release of therapeutic agents. In addition, these carbohydrate functionalized nano-carriers are more compatible with construction of the intracellular delivery platforms like the carbohydrate-modified metal NPs, quantum dots, and magnetic nano-materials. In this review, we discuss recent research in the field of multifunctional glycol-nanoparticles (GNPs) intended for cancer drug delivery applications.

Optimized Immobilization of Biomolecules on Nonspherical Gold Nanostructures for Efficient Localized Surface Plasmon Resonance Biosensing

Plasmonic biosensing techniques employ metal nanostructures, commonly gold (Au), often with biomolecules attached to their surfaces either directly or via other linkers. Various surface chemistry methods based on dispersion and covalent interactions are used to attach biomolecules to Au. As a result, when immobilizing a molecule on a metal surface, quantitative estimates of binding efficiency and stability of these surface chemistry methods are needed. Most prior work to compare such methods deals with bulk/thin film configurations or spherical nanoparticles, and very little is known about immobilization of biomolecules on plasmonic nanostructures of different shapes. Besides, due to rapid advancement of modern nanofabrication techniques, there is a growing need to determine an efficient surface chemistry method for immobilization of biomolecules on nonspherical plasmonic nanostructures. Previous comparison of immobilization methods on spherical Au nanoparticles has shown that physical adsorption resulted in the highest concentration of immobilized antibodies. In our work, we conducted a similar study and compared four representative Au surface functionalization methods as well as estimated how efficient these methods are at attaching biomolecules to nonspherical plasmonic Au nanostructures. We estimated the concentration of immobilized antibody that is specific to human C-reactive protein (anti-hCRP) by measuring the localized surface plasmon resonance (LSPR) shifts after exposing the surface of Au nanostructures to the antibody. Our results differ from the previously reported ones since the highest concentration of anti-hCRP was immobilized using 11-mercaptoundecanoic acid (MUA) chemistry. We demonstrated that immobilized antibodies retained their stability and specificity toward hCRP throughout the immunoassay when diluted hCRP or hCRP-spiked human serum samples were used. These findings have important implications for the fields of biosensing and diagnostics that employ nonspherical plasmonic nanostructures since an overall performance of these devices depends on efficient biomolecule immobilization.

Synthesis of tunable DNA-directed trepang-like Au nanocrystals for imaging application

Multi-branched metal nanomaterials can exhibit precisely controllable plasmonic properties with the precise control of their sizes and morphologies. In this study, trepang-like gold nanocrystals (AuNCs) with tunable plasmonic properties were synthesized via DNA-directed self-assembly technology. The gold precursor was precisely controlled to be reduced and grow along the DNA skeleton of DNA-conjugated gold nanorods to form multi-branched trepang-like nanocrystals. It was investigated in detail and proven that several key factors greatly influenced the precise control of the morphology and plasmonic property of the proposed AuNCs during their synthesis, including the gold precursor, reducing agent, surfactant, loading amount of DNA and DNA structure. The relative finite-difference time-domain calculation results suggested that the change in the plasmonic resonance peak is consistent with the precise change in the size and morphology of the as-synthesized AuNCs. The trepang-like AuNCs exhibited broad absorption bands in the wavelength range of 700-1100 nm with a high photothermal conversion efficiency of 36.2%. Finally, the trepang-like AuNCs with good biocompatibility were applied in photothermal therapy and imaging analysis.

The appliances and prospects of aurum nanomaterials in biodiagnostics, imaging, drug delivery and combination therapy

Aurum nanomaterials (ANM), combining the features of nanotechnology and metal elements, have demonstrated enormous potential and aroused great attention on biomedical applications over the past few decades. Particularly, their advantages, such as controllable particle size, flexible surface modification, higher drug loading, good stability and biocompatibility, especially unique optical properties, promote the development of ANM in biomedical field. In this review, we will discuss the advanced preparation process of ANM and summarize their recent applications as well as their prospects in diagnosis and therapy. Besides, multi-functional ANM-based theranostic nanosystems will be introduced in details, including radiotherapy (RT), photothermal therapy (PTT), photodynamic therapy (PDT), immunotherapy (IT), and so on.

Ultrasensitive Electrochemical Biosensor of Bacterial 16S rRNA Gene Based on polyA DNA Probes

Traditional microbiology analysis is usually hindered by the long time-cost and lack of portability in many urgent situations. In this work, we developed a novel electrochemical DNA biosensor (E-biosensor) for sensitive analysis of the 16S rRNA gene of five bacteria, using a consecutive adenine (polyA) probe. The polyA probe consists of a polyA tail and a recognition part. The polyA tail can combine onto the gold surface with improved controllability of the surface density, by conveniently changing the length of polyA. The recognition part of the capture probe together with two biotin-labeled reporter probes hybridize with the target DNA and form a stable DNA-tetramer sandwich structure, and then avidin-HRP enzyme was added to produce a redox current signal for the following electrochemical detection. Finally, we realized sensitive quantification of artificial target DNA with a limit of detection (LOD) of 10 fM, and excellent selectivity and reusability were also demonstrated. Importantly, the detection capability was equally good when facing bacterial genomic DNA, due to the base-stacking force of our multireporter-probe system, which can help to break the second structure and stabilize the probe-target complexes. Our biosensor was constructed on a 16-channel electrode chip without any polymerase chain reaction (PCR) process needed, which took a significant step toward a portable bacteria biosensor.

Multifunctional Gold Nanoparticles Overcome MicroRNA Regulatory Network Mediated-Multidrug Resistant Leukemia

Resistance to chemotherapy and molecularly targeted therapies is a major problem in current leukemia treatments. Here, we investigated cross-talk between the miR-221 network and P-glycoprotein (P-gp) in doxorubicin-induced drug resistance of leukemia cells. Multifunctional gold nanoparticles were designed and synthesized to co-deliver three anticancer agents, AS1411, doxorubicin and anti-221, for improving leukemia treatment efficacy. These nanoparticles significantly inhibited the proliferation and clonogenic potential, and induced apoptosis of drug-resistant leukemia cells. The decreased growth of drug-resistant cells induced by these nanoparticles was associated with marked downregulation of miR-221 and DNMT1, leading to restored p27kip1 and p15ink4b tumor suppressor expression, as well as miR-221-mediated reduction of P-gp expression. Finally, primary blasts derived from leukemia patients experiencing chemoresistant relapse that were exposed to these nanoparticles were sensitized to doxorubicin, as evidenced by suppression of leukemic cell growth and a significant reduction of the doxorubicin IC50 value. Our findings provide proof of concept that this novel drug delivery system can precisely reverse the multidrug resistant leukemia phenotype based on preclinical models of leukemia, providing the framework for future clinical trials aimed at overcoming drug resistance and improving patient outcome.

Bio-fabrication of pigment-capped silver nanoparticles encountering antibiotic-resistant strains and their cytotoxic effect towards human epidermoid larynx carcinoma (HEp-2) cells

Bacterial biomolecule-mediated nanoparticle (NP) synthesis constitutes a reliable, eco-friendly approach that ameliorates green-chemistry principles. In this study, stable silver nanoparticles were synthesized by exposing aqueous silver ions to an extracellular diffusible pigment produced by Pseudomonas aeruginosa (PA6) under optimized laboratory conditions. Spectroscopic and microscopic analyses showed the typical characteristics of silver with an average size of ∼28.30 nm and spherical shape. The particles were polydispersed and showed no definite agglomeration with a zeta potential of −32.3 mV, conferring stability. Antimicrobial studies were carried out using 5, 15, 25 and 50 μg mL⁻¹ concentrations of pcAgNPs, which showed significant antibacterial activity toward clinically important pathogens at all concentrations compared to with the control sample. The bactericidal effect induced by pcAgNPs associated with cell damage was well demonstrated using electron microscopic studies. ROS production was measured using the DCFH-DA method and the oxidative stress was assessed by measuring the reduced glutathione (GSH) levels. Cytotoxicity studies on HEp-2 (Human Epidermoid Larynx Carcinoma) cells exposed to pcAgNPs showed dose-dependent cytotoxic effect with IC₅₀ of 14.8 μg mL⁻¹ compared to with IC₅₀ of 7.38 μg mL⁻¹ for the Vero cell control. Mechanistically, the pcAgNPs activated p53 that induced catalase, leading to apoptosis and DNA fragmentation via a p53 transcriptional pathway and electron transport arrest, which resulted in cell death. This synergistic efficacy of pigment-AgNPs demonstrated excellent antimicrobial and anti-proliferative activities, providing a potential lead for developing a broad-spectrum antibacterial agent and improving the therapeutic modalities targeting carcinoma cells at the gene level.

Bacterial biomolecule-mediated nanoparticle (NP) synthesis constitutes a reliable, eco-friendly approach that ameliorates green-chemistry principles.

Detection of chloramphenicol using a novel apta-sensing platform based on aptamer terminal-lock in milk samples

In this paper, a novel apta-sensing colorimetric platform for rapid detection of chloramphenicol (CAP) in raw milk was developed. The AuNPs are stabilized by short-sequences aptamers against salt induced aggregation and this is the base of most colorimetric aptasensors development. However, the statute shows low sensitivity for the long-sequence aptamers. Herein, we propose an alternative strategy that use intact long-sequence aptamers for develop a highly sensitive AuNP-based colorimetric aptasensor. Determination of CAP in animal derived foods is an urgent demanded in the effort to minimize food safety risk. Therefore, we chose it as the representative model to construct the colorimetric sensing platform based on aptamer terminal-lock (ATL). In the ATL, intact aptamer was used as a molecular recognition element and a short-sequence oligonucleotide serving as a locker probe (LP) which is complementary of aptamer terminal fragments. By formation of aptamer/target complex, the LP leaves the ATL and adsorbs on the surface of AuNPs, leading to the AuNPs stabilization against salt-induced aggregation. This aptasensor shows a low limit of detection (0.03 nM) with high selectivity toward CAP. Moreover, the designed sensing platform was successfully applied to detect CAP in the milk samples. These results demonstrate our introduced label-free method for CAP detection is simple, sensitive, and highly selective.

Core/Shell Gene Carriers with Different Lengths of PLGA Chains to Transfect Endothelial Cells

In order to improve the transfection efficiency and reduce the cytotoxicity of gene carriers, many strategies have been used to develop novel gene carriers. In this study, five complex micelles (MSP(2 k), MSP(4 k), MSP(6 k), MSP(8 k), and MSP(10 k)) were prepared from methoxy-poly(ethylene glycol)-b-poly(d,l-lactide-co-glycolide) (mPEG-b-PLGA) and sorbitol-poly(d,l-lactide-co-glycolide)-graft-PEI (sorbitol-PLGA-g-PEI, where the designed molecular weights of PLGA chains were 2 kDa, 4 kDa, 6 kDa, 8 kDa, and 10 kDa, respectively) copolymers by a self-assembly method, and the mass ratio of mPEG-b-PLGA to sorbitol-PLGA-g-PEI was 1/3. These complex micelles and their gene complexes had appropriate sizes and zeta potentials, and pEGFP-ZNF580 (pDNA) could be efficiently internalized into EA.hy926 cells by their gene complexes (MSP(2 k)/pDNA, MSP(4 k)/pDNA, MSP(6 k)/pDNA, MSP(8 k)/pDNA, and MSP(10 k)/pDNA). The MTT assay results demonstrated that the gene complexes had low cytotoxicity in vitro. When the hydrophobic PLGA chain increased above 6 kDa, the gene complexes showed higher performance than that prepared from short hydrophobic chains. Moreover, the relative ZNF580 protein expression levels in MSP(6 k)/pDNA, MSP(8 k)/pDNA, and MSP(10 k)/pDNA) groups were 79.6%, 71.2%, and 73%, respectively. These gene complexes could promote the transfection of endothelial cells, while providing important information and insight for the design of new and effective gene carriers to promote the proliferation and migration of endothelial cells.

The promising potentials of capped gold nanoparticles for drug delivery systems

Fabrication and characterisation of gold nanoparticles (GNPs) through reducing agents and different capped agents are one of their most attractive applications in biomedicine. GNPs are coated using various agents such as carbohydrate, amino acids, peptides and proteins. These capped gold nanoparticles (C-GNPs) are applied for wide different applications including drug delivery in the recent decade and potential treatment and diagnosis in drug delivery systems (DDS). Recent studies have shown that these novel compounds and conjugated-nanoparticles drugs play a key role for the promising cure of high-risk refractory diseases. In addition, it seems that these compounds have a capability for potential treatment of certain cancers. In this review, a well-defined description of C-GNPs and the application of these nanoparticles are discussed. Our study revealed that C-GNPs with anticancer drugs or new compounds could be potentially applied for biomedical usage especially in cancer therapy.

Rapid and Reliable Detection of Alkaline Phosphatase by a Hot Spots Amplification Strategy Based on Well-Controlled Assembly on Single Nanoparticle

The first appeal of clinical assay is always accurate and rapid. For alkaline phosphatase (ALP) monitoring in medical treatment, a rapid, reliable surface-enhanced Raman scattering (SERS) test kit is designed based on a "hot spots" amplification strategy. Consisting of alkyne-tagged Au nanoparticles (NPs), Ag⁺, and enzyme substrate, the packaged test kit can achieve one-step clinical assay of ALP in human serum within several minutes, while the operation is simple as it directly inputs the sample into the test kit. Here, Ag⁺ ions are adsorbed onto the surface of Au core due to electrostatic interaction between Ag⁺ and the negatively charged donor surface, then enzymatic biocatalysis of ALP triggers the reduction of Ag⁺ and subsequently silver growth occurs on every Au core surface in a controllable manner, forming "hot spots" between the Au core and Ag shell, in which the SERS signal of alkyne Raman reporters would be highly amplified. Meanwhile, ALP mediates a redox reaction of Ag⁺ as well as the dynamic silver coating process so the increase of SERS intensity is well-controlled and can be recognized with increasing amounts of the targets. Instead of conventional NP aggregation, this leads to a more reproducible result. In particular, the distinct Raman emission from our self-synthesized alkyne reporter is narrow and stable with zero background in the Raman silent region, suffering no optical fluctuation from biosystem inputs and the detection results are therefore reliable with a limit of detection of 0.01 U/L (2.3 pg/mL). Along with ultrahigh stability, this SERS test kit therefore is an important point-of-care candidate for a reliable, efficacious, and highly sensitive detection method for ALP, which potentially decreases the need for time-consuming clinical trials.

Nanoparticle-Based Receptors Mimic Protein-Ligand Recognition

The self-assembly of a monolayer of ligands on the surface of noble-metal nanoparticles dictates the fundamental nanoparticle's behavior and its functionality. In this combined computational-experimental study, we analyze the structure, organization, and dynamics of functionalized coating thiols in monolayer-protected gold nanoparticles (AuNPs). We explain how functionalized coating thiols self-organize through a delicate and somehow counterintuitive balance of interactions within the monolayer itself and with the solvent. We further describe how the nature and plasticity of these interactions modulate nanoparticle-based chemosensing. Importantly, we found that self-organization of coating thiols can induce the formation of binding pockets in AuNPs. These transient cavities can accommodate small molecules, mimicking protein-ligand recognition, which could explain the selectivity and sensitivity observed for different organic analytes in NMR chemosensing experiments. Thus, our findings advocate for the rational design of tailored coating groups to form specific recognition binding sites on monolayer-protected AuNPs.

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Synthesis and molecular simulations of AuNPs for chemosensing

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A rationale for the molecular recognition ability of functionalized AuNPs

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Functionalized coating ligands form transient protein-like binding pockets

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Toward the computational nanodesign of intelligent nanoreceptors for chemosensing

The functionalization of monolayer-protected nanoparticles is at the frontier of nanotechnology, such that innovative applications are emerging in fields such as nanomedicine, chemosensing, and even catalysis. Importantly, the nanoparticle's functionality is mainly defined by the nature of the ligands forming the coating monolayer. Here, we show how the self-organization of functionalized coating ligands in monolayer-protected gold nanoparticles (AuNPs) affects their solubility and molecular recognition abilities. We found that coating ligands form transient, protein-like binding pockets in functionalized AuNPs. Thus, we reveal that nanoparticle-based chemosensing operates through a recognition process that is similar to that for protein-ligand complex formation. These findings could now herald the arrival of the computational nanodesign of intelligent nanodevices with recognition abilities toward small molecules such as drugs, metabolites, illegal drugs, and small molecular markers for cancer.

TAT-Modified Gold Nanoparticle Carrier with Enhanced Anticancer Activity and Size Effect on Overcoming Multidrug Resistance

Highly efficient targeted delivery is crucial for successful anticancer chemotherapy. In this study, we developed a drug delivery system ANS-TAT-AuNP that loads anticancer molecule 2-(9-anthracenylmethylene)-hydrazinecarbothioamide (ANS) via conjugation with cell-penetrating peptide TAT modified AuNPs. The in vitro study showed that the IC₅₀ value of ANS-TAT-AuNPs_3.8 nm reduced by 11.28- (24 h) and 12.64-fold (48 h) after incubation with liver hepatocellular carcinoma HepG₂ cells compared to that of free ANS, suggesting that TAT modified AuNPs could enhance the antiproliferative activity of ANS. Also, ANS-TAT-AuNPs showed a size effect on overcoming multidrug resistance (MDR). The potential of ANS-TAT-AuNPs in overcoming MDR was assessed with MCF-7/ADR drug-resistant cell line, the drug resistance index (DRI) of which was extremely high (>190). The DRI of ANS-TAT-AuNPs_22.1 nm decreased dramatically to 1.48 (24 h) and 2.20 (48 h), while that of ANS-TAT-AuNPs_3.8 nm decreased to 7.64 (24 h) and 7.77 (48 h), indicating that ANS-TAT-AuNPs_22.1 nm could treat extremely resistant MCF-7/ADR cancer cells as drug sensitive ones. The data suggest that the larger AuNPs had more profound effect on overcoming MDR, which could effectively prevent drug efflux due to their size being much larger than that of the p-glycoprotein channel (9-25 Å).

DNA-mediated inhibition of peroxidase-like activities on platinum nanoparticles for simple and rapid colorimetric detection of nucleic acids

In this research, we found that the peroxidase-like activities of noncovalent DNA-Pt hybrid nanoparticles could be obviously blocked, when Pt nanoparticles (PtNPs) were synthesized in situ using DNA as a template. Moreover, this self-assembled synthetic process was very convenient and rapid (within few mintues), and the inhibition mediated by DNA was also very effective. First, by the paper-based analytical device (PAD) we found the catalytic activities of DNA-Pt hybrid nanoparticles exhibited a linear response to the concentration of DNA in the range from 0.0075 to 0.25µM. Then, with the magnetic bead isolated system and target DNA-induced hybridization chain reaction (HCR), we realized the specific target DNA analysis with a low detection of 0.228nM, and demonstrated its effectivity in distinguishing the target DNA from other interferences. To our knowledge, this is the first report that used the nanoassembly between DNA and PtNPs for colorimetric detection of nucleic acids, which was based on DNA-mediated inhibition of catalytic activities of platinum nanoparticles. The results may be useful for understanding the interactions between DNA and metal nanoparticles, and for development of other convenient and effective analytical strategies.

Synthesis of Gold Nanoparticles with Buffer-Dependent Variations of Size and Morphology in Biological Buffers

The demand for biologically compatible and stable noble metal nanoparticles (NPs) has increased in recent years due to their inert nature and unique optical properties. In this article, we present 11 different synthetic methods for obtaining gold nanoparticles (Au NPs) through the use of common biological buffers. The results demonstrate that the sizes, shapes, and monodispersity of the NPs could be varied depending on the type of buffer used, as these buffers acted as both a reducing agent and a stabilizer in each synthesis. Theoretical simulations and electrochemical experiments were performed to understand the buffer-dependent variations of size and morphology exhibited by these Au NPs, which revealed that surface interactions and the electrostatic energy on the (111) surface of Au were the determining factors. The long-term stability of the synthesized NPs in buffer solution was also investigated. Most NPs synthesized using buffers showed a uniquely wide range of pH stability and excellent cell viability without the need for further modifications.

Enhancing the efficiency of bortezomib conjugated to pegylated gold nanoparticles: an in vitro study on human pancreatic cancer cells and adenocarcinoma human lung alveolar basal epithelial cells

OBJECTIVES

Gold nanoparticles have become promising vectors for cancer diagnosis and treatment. The present study investigates the effect of bortezomib (BTZ), a proteasome inhibitor, conjugated with pegylated gold nanoparticles (PEGAuNPs) in pancreatic and lung cancer cells.

METHODS

Synthesized gold nanoparticles (PEGAuNPs) were conjugated with bortezomib antitumor drug. We investigated the cytotoxicity induced by BTZ conjugated with functionalized gold nanoparticles in vitro, in the human pancreatic (S2-013) and lung (A549) cancer cell lines.

RESULTS

We found an efficient of conjugation of BTZ with PEGAuNPs. In vitro assays showed that after 72 h' incubation with PEGAuNPs-BTZ cancer cells revealed alterations in morphology; also for S2-013 and A549 cancer cells, the IC50 value of free BTZ is respectively 1.5 and 4.3 times higher than the IC50 value of PEGAuNPs-BTZ. Furthermore, for TERT-HPNE, the IC50 value is around 63 times lower for free BTZ than the conjugated nanovehicle. Cell growth inhibition results showed a remarkable enhancement in the effect of BTZ when conjugated with AuNPs.

CONCLUSIONS

Our findings showed that conjugation with PEGAuNPs enhance the BTZ growth-inhibition effect on human cancer cells (S2-013 and A549) and decreases its toxicity against normal cells (TERT-HPNE).

Modulation of population density and size of silver nanoparticles embedded in bacterial cellulose via ammonia exposure: visual detection of volatile compounds in a piece of plasmonic nanopaper

The localized surface plasmon resonance exhibited by noble metal nanoparticles can be sensitively tuned by varying their size and interparticle distances. We report that corrosive vapour (ammonia) exposure dramatically reduces the population density of silver nanoparticles (AgNPs) embedded within bacterial cellulose, leading to a larger distance between the remaining nanoparticles and a decrease in the UV-Vis absorbance associated with the AgNP plasmonic properties. We also found that the size distribution of AgNPs embedded in bacterial cellulose undergoes a reduction in the presence of volatile compounds released during food spoilage, modulating the studied nanoplasmonic properties. In fact, such a plasmonic nanopaper exhibits a change in colour from amber to light amber upon the explored corrosive vapour exposure and from amber to a grey or taupe colour upon fish or meat spoilage exposure. These phenomena are proposed as a simple visual detection of volatile compounds in a flexible, transparent, permeable and stable single-use nanoplasmonic membrane, which opens the way to innovative approaches and capabilities in gas sensing and smart packaging.

Gold Nanoparticle-Based Förster Resonance Energy Transfer (FRET) Analysis of Estrogen Receptor: DNA Interaction

Estrogen receptors play critical roles in regulating genes responsible for development and maintenance of reproductive tissues and other physiological function. The interaction of ERs with DNA sequences, known as estrogen response elements (EREs) (a palindromic repeat separated by three-base spacer, 5'GGTCAnnnTGACC-3'), is required for estrogen regulation of target gene expression. Here, we describe a simple "mix-and-measure"-based method for detecting ER:ERE interactions using ERE-immobilized metal nanoparticles and water-soluble conjugated polyelectrolytes (CPEs) as cooperative sensing elements. This method can differentiate the distinct DNA-binding affinity between ERα and ERβ, and determine ER:ERE-binding stoichiometry. This method can also accurately detect all 15 singly mutated EREs (i.e., three possible base substitutions at each of one to five positions from left to right of the 5' end half site, GGTCA) for their binding energy to ER. This method is compatible with 96-well plate format for high-throughput analysis.

A highly sensitive fluorescence turn-on platform with silver nanoparticles aptasening for human platelet-derived growth factor-BB

In this paper, we demonstrated a simple and highly sensitive fluorescence platform for protein detection. Silver nanoparticles (AgNPs) worked as carriers and quenchers for FAM labeled aptamers (FAM-apt). Biotin labeled aptamers (Bio-apt), FAM-apt functionalized AgNPs (Ag-FAM-apt), and a target protein, human platelet-derived growth factor-BB (PDGF-BB) could form a sandwich-type complex. Once the etching solvents were added, AgNPs were dissolved and the fluorescence resonance energy transfer (FRET) between AgNPs and FAM was broken. FAM-apt were no longer quenched and released into the solution in the 96-well microplates, so the fluorescence signal would turn from "off" state to "on" state. This method had possessed several advantages: Firstly, increased specificity which was contributed by the sandwich binding of aptamers; Secondly, quenching ability of AgNPs which was utilized to make signal turn-on; Thirdly, high throughout in which 96 samples could be detected simultaneously. The results showed a linear relationship between fluorescence intensity and PDGF-BB concentration (10 ng mL(-1)-100 ng mL(-1)), and the detection limit was 7 ng mL(-1). This simple and sensitive method would have a promising future for development and application.

Effects of Size, Shape, Surface Charge and Functionalization on Cytotoxicity of Gold Nanoparticles

Gold nanoparticles ( Au NPs) are emerging as promising nanomaterials from which we construct diagnostic and therapeutic nanosystems. For understanding the fundamental behaviors of Au NPs with biological systems, interactions of Au NPs and cells should be considered first. In this review, we present a detailed analysis of data on the cytotoxicity of most popular Au NPs including gold nanoclusters ( Au NCs), spherical Au NPs, gold nanoshells ( Au NSs) and gold nanorods ( Au NRs). Relationships correlating the cell models, physicochemical properties (size, shape, chemical functionality and surface charge) of Au NPs and cytotoxicity are discussed on the basis of data analysis. Some general conclusions, current challenges and future prospects/solutions on the issue have been provided.

Treating cancer stem cells and cancer metastasis using glucose-coated gold nanoparticles

Cancer ranks among the leading causes of human mortality. Cancer becomes intractable when it spreads from the primary tumor site to various organs (such as bone, lung, liver, and then brain). Unlike solid tumor cells, cancer stem cells and metastatic cancer cells grow in a non-attached (suspension) form when moving from their source to other locations in the body. Due to the non-attached growth nature, metastasis is often first detected in the circulatory systems, for instance in a lymph node near the primary tumor. Cancer research over the past several decades has primarily focused on treating solid tumors, but targeted therapy to treat cancer stem cells and cancer metastasis has yet to be developed. Because cancers undergo faster metabolism and consume more glucose than normal cells, glucose was chosen in this study as a reagent to target cancer cells. In particular, by covalently binding gold nanoparticles (GNPs) with thio-PEG (polyethylene glycol) and thio-glucose, the resulting functionalized GNPs (Glu-GNPs) were created for targeted treatment of cancer metastasis and cancer stem cells. Suspension cancer cell THP-1 (human monocytic cell line derived from acute monocytic leukemia patients) was selected because it has properties similar to cancer stem cells and has been used as a metastatic cancer cell model for in vitro studies. To take advantage of cancer cells' elevated glucose consumption over normal cells, different starvation periods were screened in order to achieve optimal treatment effects. Cancer cells were then fed using Glu-GNPs followed by X-ray irradiation treatment. For comparison, solid tumor MCF-7 cells (breast cancer cell line) were studied as well. Our irradiation experimental results show that Glu-GNPs are better irradiation sensitizers to treat THP-1 cells than MCF-7 cells, or Glu-GNPs enhance the cancer killing of THP-1 cells 20% more than X-ray irradiation alone and GNP treatment alone. This finding can help oncologists to design therapeutic strategies to target cancer stem cells and cancer metastasis.

PolyA-tailed and fluorophore-labeled aptamer-gold nanoparticle conjugate for fluorescence turn-on bioassay using iodide-induced ligand displacement

Depending on the strong affinity of polyA sequence to gold (or silver) surface, applicability of polyA-tailed DNA-gold (or silver) nanoparticle conjugates in homogeneous and heterogeneous protein assays was first demonstrated. Interestingly, when using polyA-tailed, fluophore-labeled DNA-AuNP conjugate, it was found that iodide and thiosulfate anions could act as the ligand displacing reagent to detach polyA-tailed DNA strands from AuNP surface and simultaneously activate the AuNP-quenched fluorophores by destroying the polyA-AuNP interaction via a divide-and-conquer strategy. Based on this new discovery, we have developed a novel, cost-effective and sandwich-type fluorescence turn-on aptasensor for highly sensitive and specific thrombin detection, what took advantage of aptamer-conjugated magnetic beads (apt-MBs) for protein capture and separation, and iodide-induced fluorescence recovery of activatable polyA-based AuNP probes through ligand displacement for fluorescence turn-on detection. This proposed aptasensor could detect thrombin specifically with a detection limit as low as 89pM, which was better than or comparable to many existing fluorescent thrombin assays. Importantly, employment of such polyA-based AuNP conjugate not only avoids the use of thiolated oligonucleotides and thiol-containing displacing reagents, but also offers new possibilities for fabricating convenient and cost-effective bioanalytical applications.

Statistical analysis of gold nanoparticle-induced oxidative stress and apoptosis in myoblast (C2C12) cells

Nanoscale gold particles (Au-NPs) with a diameter below 20nm are notably important candidates for various important applications because of their extraordinary quantum size effects. Their high surface area-to-volume ratio facilitates their very high reactivities; therefore, they can be utilised in different ways in biomedical applications. For example, these nanoparticles can penetrate into cells and bind with proteins or DNA and are therefore potential nanostructures employed for sensing and detecting various biological identities. In the present work, we synthesised Au-NPs via a colloidal process using chloroauric acid (HAuCl4·4H2O) and trisodium citrate dihydrate (N3C6H5O7) as a reducing agent. The shape evolution and the structural properties of these NPs were investigated in detail using TEM and high resolution HR-TEM investigations. Different doses of Au NPs have been applied to treat C2C12 myoblast cells in a 24-h incubation period, and a dose-dependent study has also been performed. The cells were cultivated in DMEM with FBS and antibiotics (strepto-penicillin) at 37°C in a 5% humidified environment of CO2 and 95% air. Cell viability analysis using MTT assays revealed that increased concentration of Au NPs (100-1000 ng/mL) resulted in a decreased density of cells. The amount of reactive oxygen species (ROS) in C2C12 cells analysed with Au-NPs (in a dose-dependent manner), and the RT-PCR data demonstrated the up-regulation of caspase-3 and caspase-7 genes in C2C12 cells after treatment with Au-NPs. These results have been confirmed by detailed confocal microscopy (CLSM) studies. In addition, the quantitative analysis of the Au-NPs was also confirmed by statistical analytical parameters, such as precision, accuracy, linearity, limits of detection (LOD) and limit of quantitation (LOQ), quantitative recoveries and relative standard deviation (RSD), and the analyses again exhibited a significant and large effect of Au NPs on C2C12 cells.

Pre-miRNA expressing plasmid delivery for anti-cancer therapy

The premiR145/GFP expressing plasmid DNA was delivered into glioma cells and the transcripted miRNA145 efficiently decreases the expression of CTGF.

Hybrid sensor using gold nanoparticles and conjugated polyelectrolytes for studying sequence rule in protein-DNA interactions

Protein-DNA interactions play center roles in many biological processes. Studying sequence specific protein-DNA interactions and revealing sequence rules require sensitive and quantitative methodologies that are capable of capturing subtle affinity difference with high accuracy and in a high throughput manner. In this study, double stranded DNA-conjugated gold nanoparticles (dsDNA-AuNPs) and water-soluble conjugated polyelectrolytes (CPEs) are used as cooperative sensing elements to construct a suit of hybrid sensors for detecting protein-DNA interactions, exploiting the differential Förster resonance energy transfer (FRET) with and without protein binding. Through a proper selection of CPEs in terms of charge properties relative to the charge of dsDNA-AuNPs and emission wavelengths relative to the AuNP extinction peak, the hybrid sensors can be constructed into "light-on", "light-off", and "two-way" models. Protein binding can be detected by fluorescence recovery, fluorescence quenching, or both ways, respectively. The "two-way" sensor allows for detection of proteins of any charge properties or unknown charge properties. With estrogen receptor (ERα and ERβ), their consensus DNA (5'-GGTCAnnnTGACC-5') element, and all 15 possible singly mutated elements (i.e., 3 possible base substitutions at each of 1 to 5 positions from left to right of the 5' end half site, GGTCA), we have demonstrated the accuracy of the hybrids sensors for determination of binding affinity constant, binding stoichiometry, and site- and nucleotide-specific binding energy matrix. The in vitro binding energy determined by the hybrid sensors correlates very well with the energy matrix computed from in vivo genome-wide ERα binding data using Thermodynamic Modeling of ChIP-Seq (rank correlation coefficient 0.98). The high degree of correlation of the in vitro energy matrix versus the in vivo matrix renders the new method a highly reliable alternative for understanding in vivo protein binding in the whole genome.

Multiple strategies to activate gold nanoparticles as antibiotics

Widespread antibiotic resistance calls for new strategies. Nanotechnology provides a chance to overcome antibiotic resistance by multiple antibiotic mechanisms. This paper reviews the progress in activating gold nanoparticles with nonantibiotic or antibiotic molecules to combat bacterial resistance, analyzes the gap between experimental achievements and real clinical application, and suggests some potential directions in developing antibacterial nanodrugs.