Gold Nanoparticles in Nanomedicine: Unique Properties and Therapeutic Potential

Gold nanoparticles (NPs) have demonstrated significance in several important fields, including drug delivery and anticancer research, due to their unique properties. Gold NPs possess significant optical characteristics that enhance their application in biosensor development for diagnosis, in photothermal and photodynamic therapies for anticancer treatment, and in targeted drug delivery and bioimaging. The broad surface modification possibilities of gold NPs have been utilized in the delivery of various molecules, including nucleic acids, drugs, and proteins. Moreover, gold NPs possess strong localized surface plasmon resonance (LSPR) properties, facilitating their use in surface-enhanced Raman scattering for precise and efficient biomolecule detection. These optical properties are extensively utilized in anticancer research. Both photothermal and photodynamic therapies show significant results in anticancer treatments using gold NPs. Additionally, the properties of gold NPs demonstrate potential in other biological areas, particularly in antimicrobial activity. In addition to delivering antigens, peptides, and antibiotics to enhance antimicrobial activity, gold NPs can penetrate cell membranes and induce apoptosis through various intracellular mechanisms. Among other types of metal NPs, gold NPs show more tolerable toxicity capacity, supporting their application in wide-ranging areas. Gold NPs hold a special position in nanomaterial research, offering limited toxicity and unique properties. This review aims to address recently highlighted applications and the current status of gold NP research and to discuss their future in nanomedicine.

Gold Nanoparticles: Multifunctional Properties, Synthesis, and Future Prospects

Gold nanoparticles (NPs) are among the most commonly employed metal NPs in biological applications, with distinctive physicochemical features. Their extraordinary optical properties, stemming from strong localized surface plasmon resonance (LSPR), contribute to the development of novel approaches in the areas of bioimaging, biosensing, and cancer research, especially for photothermal and photodynamic therapy. The ease of functionalization with various ligands provides a novel approach to the precise delivery of these molecules to targeted areas. Gold NPs' ability to transfer heat and electricity positions them as valuable materials for advancing thermal management and electronic systems. Moreover, their inherent characteristics, such as inertness, give rise to the synthesis of novel antibacterial and antioxidant agents as they provide a biocompatible and low-toxicity approach. Chemical and physical synthesis methods are utilized to produce gold NPs. The pursuit of more ecologically sustainable and economically viable large-scale technologies, such as environmentally benign biological processes referred to as green/biological synthesis, has garnered increasing interest among global researchers. Green synthesis methods are more favorable than other synthesis techniques as they minimize the necessity for hazardous chemicals in the reduction process due to their simplicity, cost-effectiveness, energy efficiency, and biocompatibility. This article discusses the importance of gold NPs, their optical, conductivity, antibacterial, antioxidant, and anticancer properties, synthesis methods, contemporary uses, and biosafety, emphasizing the need to understand toxicology principles and green commercialization strategies.

Temperature Sensitive PNIPAm-g-PEI/Gold Nanotriangle for Gene Delivery Promotion

As a two-dimensional material, gold nanotriangles (GNTs) are rarely studied in the field of gene delivery. In this study, a temperature-responsive GNTs was developed as a novel carrier for gene delivery. The temperature-sensitive copolymer PNIPAm-g-PEI was grafted onto the surface of GNTs to construct a PNIPAm-g-PEI/GNTs composite controllable release platform. The lower critical solution temperature (LCST) of PNIPAm-g-PEI/GNTs was found to be 42 °C, and the particle size of PNIPAm-g-PEI/GNTs was 150 nm at this temperature. Gel electrophoresis experiments showed that PNIPAm-g-PEI/GNTs completely condensed DNA at 20 μg/mL, and PNIPAm-g-PEI/GNTs promoted the release of DNA under laser irradiation. Luciferase and green fluorescent protein reporter gene assays demonstrated that the transfection efficiency of PNIPAm-g-PEI/GNTs was 1.5 and 7.2 times that of PEI, respectively. These results demonstrated the promising potential of temperature-responsive GNTs as effective and safe gene delivery vectors.

The Role of Selenium Nanoparticles in the Treatment of Liver Pathologies of Various Natures

The liver is the body's largest gland, and regulates a wide variety of physiological processes. The work of the liver can be disrupted in a variety of pathologies, the number of which is several hundred. It is extremely important to monitor the health of the liver and develop approaches to combat liver diseases. In recent decades, nanomedicine has become increasingly popular in the treatment of various liver pathologies, in which nanosized biomaterials, which are inorganic, polymeric, liposomal, albumin, and other nanoparticles, play an important role. Given the need to develop environmentally safe, inexpensive, simple, and high-performance biomedical agents for theragnostic purposes and showing few side effects, special attention is being paid to nanoparticles based on the important trace element selenium (Se). It is known that the metabolism of the microelement Se occurs in the liver, and its deficiency leads to the development of several serious diseases in this organ. In addition, the liver is the depot for most selenoproteins, which can reduce oxidative stress, inhibit tumor growth, and prevent other liver damage. This review is devoted to the description of the results of recent years, revealing the important role of selenium nanoparticles in the therapy and diagnosis of several liver pathologies, depending on the dose and physicochemical properties. The possibilities of selenium nanoparticles in the treatment of liver diseases, disclosed in the review, will not only reveal the advantages of their hepatoprotective properties but also significantly supplement the data on the role of the trace element selenium in the regulation of these diseases.

Cellular Alterations in Carbohydrate and Lipid Metabolism Due to Interactions with Nanomaterials

Nanoparticles (NPs) have unique physicochemical properties that are useful for a broad range of biomedical and industrial applications; nevertheless, increasing concern exists about their biosafety. This review aims to focus on the implications of nanoparticles in cellular metabolism and their outcomes. In particular, some NPs have the ability to modify glucose and lipid metabolism, and this feature is especially interesting to treat diabetes and obesity and to target cancer cells. However, the lack of specificity to reach target cells and the toxicological evaluation of nontargeted cells can potentially induce detrimental side effects, closely related to inflammation and oxidative stress. Therefore, identifying the metabolic alterations caused by NPs, independent of their application, is highly needed. To our knowledge, this increase would lead to the improvement and safer use with a reduced toxicity, increasing the number of available NPs for diagnosis and treatment of human diseases.

Recent advances in improving intranasal allergen-specific immunotherapy; focus on delivery systems and adjuvants

Allergen-specific Immunotherapy (AIT) is the main therapeutic strategy to control and treat allergic disorders. Intranasal Immunotherapy (INIT) was introduced as a needle-free, noninvasive, and efficient approach among various routes of allergen administration. Since direct exposure of nasal mucosa to allergen extracts could induce local and systemic reactions, recent studies focus on establishing novel formulations using various delivery systems and adjuvants to improve INIT efficacy. This review categorizes and describes natural and synthetic micro/nanoparticles such as chitosan, PLGA, liposome, exosome, and nano-emulation droplets used as delivery systems or immunomodulatory and immune-regulatory agents. Also, multiple microbial agents, including probiotics, mycobacterial and viral components, TLR ligands, and biologic agents, i.e., antibody fragments, recombinant cytokines, vitamin A, and pulsed dendritic cells (DCs), are other platforms that are discussed. In addition, future perspectives and proposed strategies to help INIT were provided.

Effect of high hydrostatic pressure on the in vitro development and molecular quality of transgenic rabbit embryos derived from nano-transfected zygotes

The aim of this study was to evaluate the effect of high hydrostatic pressure (HHP) on the in vitro developmental abilities of nano-transfected rabbit zygotes, their transfection efficiency, and the molecular quality of the blastocysts generated. This quality was assessed by estimating the quantitative profiles of Oct4, Casp7, and Bcl2 mRNA transcripts. The nano-transfection efficiencies of zygotes that had been pre-treated with either 20 MPa or 40 MPa of HHP (13.5% and 13.7%, respectively) were insignificantly lower than those found in zygotes not exposed to HHP prior to their nano-transfection (20.1%; P≥0.05). Moreover, applying HHP treatment with the parameters of 20 MPa and 40 MPa followed by the nano-transfection of zygotes brought about an insignificant decrease in the rates of embryos at the blastocyst stage (30.4% and 23.0%, respectively) as compared to the control group of nano-transfected zygotes (40.4%; P≥0.05). Furthermore, analyzing the transcriptional activity of Oct4, Bcl2, and Casp7 genes revealed that HHP enhances the relative abundance (RA) of all mRNA transcripts in blastocysts derived from non-transfected rabbit zygotes. In turn, the augmented RAs found in the pro-apoptotic Casp7 and anti-apoptotic Bcl-2 transcripts confirmed the onset and progression of programmed cell death in blastocysts developed from nano-transfected zygotes that had undergone HHP pre-treatment. The conceptualization based not only on a novel nano-transfection approach used to genetically modify in vivo-fertilized rabbit zygotes but also on their HHP pre-treatment is elaborated here for the first time, with an emphasis on further investigations aimed at producing transgenic rabbit and other mammalian species embryos by somatic cell cloning.

Gold-Polymer Nanocomposites for Future Therapeutic and Tissue Engineering Applications

Gold nanoparticles (AuNPs) have been extensively investigated for their use in various biomedical applications. Owing to their biocompatibility, simple surface modifications, and electrical and unique optical properties, AuNPs are considered promising nanomaterials for use in in vitro disease diagnosis, in vivo imaging, drug delivery, and tissue engineering applications. The functionality of AuNPs may be further expanded by producing hybrid nanocomposites with polymers that provide additional functions, responsiveness, and improved biocompatibility. Polymers may deliver large quantities of drugs or genes in therapeutic applications. A polymer alters the surface charges of AuNPs to improve or modulate cellular uptake efficiency and their biodistribution in the body. Furthermore, designing the functionality of nanocomposites to respond to an endo- or exogenous stimulus, such as pH, enzymes, or light, may facilitate the development of novel therapeutic applications. In this review, we focus on the recent progress in the use of AuNPs and Au-polymer nanocomposites in therapeutic applications such as drug or gene delivery, photothermal therapy, and tissue engineering.

Two-Photon Near-Infrared AIE Luminogens as Multifunctional Gene Carriers for Cancer Theranostics

Construction of multifunctional nonviral gene vectors to execute defined tasks holds great potential for the precise and effective treatment of gene-associated diseases. Herein, we have developed four large π-conjugation triphenylamine derivatives bearing two polar [12]aneN₃ heads and a lipophilic tail for applications in gene delivery, one/two-photon-triggered near-infrared (NIR) fluorescence bioimaging, and combined photodynamic therapy (PDT) and gene therapy of cancer. These compounds possess typical NIR aggregation-induced emission characteristics, mega Stokes shifts, strong two-photon excitation fluorescence, and excellent DNA condensation abilities. Among them, vector 4 with a tail of n-hexadecane realized a transfection efficiency as high as 6.7 times that of the commercial transfection agent Lipofectamine 2000 in HEK293T cell lines. Using vector 4 as an example, transfection process tracking and ex vivo/in vivo tumoral imaging and retention with high resolution, high brightness, deep tissue penetration, and good biosafety were demonstrated. In addition, efficient singlet oxygen (¹O₂) generation by the DNA complex formed by vector 4 (4/DNA) resulted in effective PDT. Combined with anticancer gene therapy, collaborative cancer treatment with a dramatically enhanced cancer cell-killing effect was achieved. The development of this "three birds, one stone" approach suggests a new and promising strategy for better cancer treatment and real-time tracking of gene delivery.

Role of gold nanoparticles in advanced biomedical applications

Gold nanoparticles (GNPs) have generated keen interest among researchers in recent years due to their excellent physicochemical properties. In general, GNPs are biocompatible, amenable to desired functionalization, non-corroding, and exhibit size and shape dependent optical and electronic properties. These excellent properties of GNPs exhibit their tremendous potential for use in diverse biomedical applications. Herein, we have evaluated the recent advancements of GNPs to highlight their exceptional potential in the biomedical field. Special focus has been given to emerging biomedical applications including bio-imaging, site specific drug/gene delivery, nano-sensing, diagnostics, photon induced therapeutics, and theranostics. We have also elaborated on the basics, presented a historical preview, and discussed the synthesis strategies, functionalization methods, stabilization techniques, and key properties of GNPs. Lastly, we have concluded this article with key findings and unaddressed challenges. Overall, this review is a complete package to understand the importance and achievements of GNPs in the biomedical field.

Surface-decorated nanoparticles clicked into nanoparticle clusters for oligonucleotide encapsulation

Gold nanoparticles (AuNPs) are the predominant and representative metal nano-carriers used for the tumor-targeted delivery of therapeutics because they possess advantages such as biocompatibility, high drug loading efficiency, and enhanced accumulation at tumor sites via the size-dependent enhanced permeability and retention (EPR) effect. In this study, we designed an AuNP functionalized with block polymers comprising polyethylenimine and azide group-functionalized poly(ethyl glycol) for the electrostatic incorporation of cytosine–guanine oligonucleotide (CpG ODN) on the surface. The ODN-incorporated AuNPs were cross-linked to gold nanoparticle clusters (AuNCs) via click chemistry using a matrix metalloproteinase (MMP)-2 cleavable peptide linker modified with alkyne groups at both ends. In the presence of Cu(i), azide groups and alkyne groups spontaneously cyclize to form a triazole ring with high fidelity and efficiency, and therefore allow single AuNPs to stack to larger AuNCs for increased EPR effect-mediated tumor targeting. ¹H-NMR and Fourier transform infrared spectroscopy revealed the successful synthesis of an azide–PEG-grafted branched polyethylenimine, and the size and morphology of AuNPs fabricated by the synthesized polymer were confirmed to be 4.02 ± 0.45 nm by field emission-transmission electron microscopy. Raman spectroscopy characterization demonstrated the introduction of azide groups on the surface of the synthesized AuNPs. Zeta-potential and gel-retardation analysis of CpG-loaded AuNPs indicated complete CpG sequestration by AuNPs when the CpG : AuNP weight ratio was higher than 1 : 2.5. The clustering process of the CpG-loaded AuNPs was monitored and was demonstrated to be dependent on the alkyne linker-to-AuNP ratio. Thus, the clicked AuNC can be tailored as a gene carrier where a high accumulation of therapeutics is required.

AuNPs with bPEI and azide modification are loaded with CpG and self-assembled to AuNCs by click chemistry using an alkyne-terminated MMP-2 cleavable peptide as a linker. The clusters are dissembled by MMP-2 to release CpG in a stimuli-responsive manner.

The Development of Functional Non-Viral Vectors for Gene Delivery

Gene therapy is manipulation in/of gene expression in specific cells/tissue to treat diseases. This manipulation is carried out by introducing exogenous nucleic acids, such as DNA or RNA, into the cell. Because of their negative charge and considerable larger size, the delivery of these molecules, in general, should be mediated by gene vectors. Non-viral vectors, as promising delivery systems, have received considerable attention due to their low cytotoxicity and non-immunogenicity. As research continued, more and more functional non-viral vectors have emerged. They not only have the ability to deliver a gene into the cells but also have other functions, such as the performance of fluorescence imaging, which aids in monitoring their progress, targeted delivery, and biodegradation. Recently, many reviews related to non-viral vectors, such as polymers and cationic lipids, have been reported. However, there are few reviews regarding functional non-viral vectors. This review summarizes the common functional non-viral vectors developed in the last ten years and their potential applications in the future. The transfection efficiency and the transport mechanism of these materials were also discussed in detail. We hope that this review can help researchers design more new high-efficiency and low-toxicity multifunctional non-viral vectors, and further accelerate the progress of gene therapy.

Multiply clustered gold-based nanoparticles complexed with exogenous pDNA achieve prolonged gene expression in stem cells

Development of a stable and prolonged gene delivery system is a key goal in the gene therapy field. To this end, we designed and fabricated a gene delivery system based on multiply-clustered gold particles that could achieve prolonged gene delivery in stem cells, leading to improved induction of differentiation.

Methods: Inorganic gold nanoparticles (AuNPs) underwent three rounds of complexation with catechol-functionalized polyethyleneimine (CPEI) and plasmid DNAs (pDNAs), in that order, with addition of heparin (HP) between rounds, yielding multiply-clustered gold-based nanoparticles (mCGNPs). Via metal-catechol group interactions, the AuNP surface was easily coordinated with positively charged CPEIs, which in turn allowed binding of pDNAs.

Results: Negatively charged HP was encapsulated with the positive charge of CPEIs via electrostatic interactions, making the NPs more compact. Repeating the complexation process yielded mCGNPs with improved transfection efficiency in human mesenchymal stem cells (hMSCs); moreover, these particles exhibited lower cytotoxicity and longer expression of pDNAs than conventional NPs. This design was applied to induction of chondrogenesis in hMSCs using pDNA harboring SOX9, an important chondrogenic transcription factor. Prolonged expression of SOX9 induced by mCGNPs triggered expression of chondrocyte extracellular matrix (ECM) protein after 14 days, leading to more efficient chondrogenic differentiation in vitro and in vivo.

A Study of the Activity of Recombinant Mn-Superoxide Dismutase in the Presence of Gold and Silver Nanoparticles

Superoxide dismutase (SOD) is one of the best characterized enzyme maintaining the redox state in the cell. A bacterial expression system was used to produce human recombinant manganese SOD with a His-tag on the C-end of the protein for better purification. In addition, gold and silver nanoparticles were chemically synthesized in a variety of sizes, and then mixed with the enzyme for immobilization. Analysis by dynamic light scattering and scanning transmission electron microscopy revealed no aggregates or agglomerates of the obtained colloids. After immobilization of the protein on AuNPs and AgNPs, the conjugates were analyzed by SDS-PAGE. It was determined that SOD was adsorbed only on the gold nanoparticles. Enzyme activity was analyzed in colloids of the gold and silver nanoparticles bearing SOD. The presence of a nanoparticle did not affect enzyme activity; however, the amount of protein and size of the gold nanoparticle did influence the enzymatic activity of the conjugate. Our findings confirm that active recombinant human superoxide dismutase can be produced using a bacterial expression system, and that the enzyme can be immobilized on metal nanoparticles. The interaction between enzymes and metal nanoparticles requires further investigation.

Recent Progress in Macromolecule-Anchored Hybrid Gold Nanomaterials for Biomedical Applications

Gold nanoparticles (AuNPs), with elegant thermal, optical, or chemical properties due to quantum size effects, may serve as unique species for therapeutic or diagnostic applications. It is worth mentioning that their small size also results in high surface activity, leading to significantly impaired stability, which greatly hinders their biomedical utilizations. To overcome this problem, various types of macromolecular materials are utilized to anchor AuNPs so as to achieve advanced synergistic effect by dispersing, protecting, and stabilizing the AuNPs in polymeric-Au hybrid self-assemblies. In this review, the most recent development of polymer-AuNP hybrid systems, including AuNPs@polymeric nanoparticles, AuNPs@polymeric micelle, AuNPs@polymeric film, and AuNPs@polymeric hydrogel are discussed with respect to their different synthetic strategies. These sophisticated materials with diverse functions, oriented toward biomedical applications, are further summarized into several active domains in the areas of drug delivery, gene delivery, photothermal therapy, antibacterials, bioimaging, etc. Finally, the possible approaches for future design of multifunctional polymer-AuNP hybrids by combining hybrid chemistry with biological interface science are proposed.

Gold nanoparticle coatings as efficient adenovirus carriers to non-infectable stem cells

Mesenchymal stem cells (MSCs) are adult pluripotent cells with the plasticity to be converted into different cell types. Their self-renewal capacity, relative ease of isolation, expansion and inherent migration to tumors, make them perfect candidates for cell therapy against cancer. However, MSCs are notoriously refractory to adenoviral infection, mainly because CAR (Coxsackie-Adenovirus Receptor) expression is absent or downregulated. Over the last years, nanoparticles have attracted a great deal of attention as potential vehicle candidates for gene delivery, but with limited effects on their own. Our data showed that the use of positively charged 14 nm gold nanoparticles either functionalized with arginine-glycine-aspartate (RGD) motif or not, increases the efficiency of adenovirus infection in comparison to commercial reagents without altering cell viability or cell phenotype. This system represents a simple, efficient and safe method for the transduction of MSCs, being attractive for cancer gene and cell therapies.

Effective and safe in vivo gene delivery based on polyglutamic acid complexes with heterocyclic amine modified-polyethylenimine

Polyethylenimine (PEI) has been extensively used for non-viral gene delivery. Increasing the molecular weight of PEI often improves transfection efficiency, but enhances cytotoxicity and non-specific interaction with plasma proteins, limiting its use in clinical applications. In this study, poly-l-glutamic acid (L-PGA) as an anionic polymer, was introduced to piperazine-modified PEI to improve its in vivo properties. The physicochemical properties, cytotoxicity, in vitro and in vivo tranfection efficiency of these carriers were evaluated. Conjugation of 50% of primary amines of PEI 25 kDa with piperazine in the presence of PGA_1% (PEI₂₅Pip_50%/PGA_1%) could significantly increase transfection efficiency even in the presence of serum compared to PEI 25 kDa. Increasing the PGA content led to lower cytotoxicity of DNA/PEI₂₅Pip_50%/PGA_1% triplexes. Systemic administration of triplexes in Balb/c mice resulted in significant enhancement of luciferase gene expression in brain, spleen, and liver compared to PEI 25 kDa. In a 30-day survival study, no significant changes were observed in mice body weights in DNA/PEI₂₅Pip_50%/PGA_1% group. Moreover, this group exhibited a survival rate of 100% compared to 0% in mice receiving PEI 25 kDa. This novel PEI₂₅Pip_50%/PGA_1% carrier could be used to overcome the serum inhibitory effects on gene expression in vivo, providing a promising gene delivery system for tissue-specific targeting.

siRNA-loaded selenium nanoparticle modified with hyaluronic acid for enhanced hepatocellular carcinoma therapy

BACKGROUND

Small interfering RNA (siRNA) as a new therapeutic modality holds promise for cancer treatment. However, the traditional viral carriers are prone to immunogenicity and risk of insertional mutagenesis.

METHODS

In order to provide a tumor-targeted delivery carrier of siRNA in cancer therapy, the hyaluronic acid (HA)-selenium (Se)-polyethylenimine (PEI) nanoparticle (NP) was fabricated by decorating SeNP with HA as a tumor-targeting moiety and by linking the polycationic polymers polyethylenimine PEI onto the surface of SeNP. The siRNA was loaded to the surface of SeNP HA-Se-PEI via the electrostatic interaction between siRNA and PEI to prepare the functionalized SeNP HA-Se-PEI@siRNA.

RESULTS

The HA-Se-PEI@siRNA was internalized into the HepG2 cell mainly in a clathrin-mediated endocytosis manner. Owing to the active tumor-targeted effect mediated by HA, HA-Se-PEI@siRNA achieved the obvious higher transfection efficiency, greater gene silencing ability, and stronger cytotoxicity in the HepG2 cell compared with the passive tumor-targeted NP Se-PEI@siRNA. The knockdown of hairy and enhancer of split 5 by HA-Se-PEI@siRNA induced the HepG2 cell cycle arrest at the G0/G1 phase and apoptosis. Furthermore, the treatment with HA-Se-PEI@siRNA resulted in greater antitumor efficacy compared with the Se-PEI@siRNA in vitro and in vivo. In addition, the HA-Se-PEI@siRNA was almost no toxic to the key organs of mice.

CONCLUSION

These findings provided an alternative therapeutic route for targeted cancer treatments.

Non-viral Gene Delivery

Although viral vectors comprise the majority of gene delivery vectors, their various safety, production, and other practical concerns have left a research gap to be addressed. The non-viral vector space encompasses a growing variety of physical and chemical methods capable of gene delivery into the nuclei of target cells. Major physical methods described in this chapter are microinjection, electroporation, and ballistic injection, magnetofection, sonoporation, optical transfection, and localized hyperthermia. Major chemical methods described in this chapter are lipofection, polyfection, gold complexation, and carbon-based methods. Combination approaches to improve transfection efficiency or reduce immunological response have shown great promise in expanding the scope of non-viral gene delivery.