State of the Art Biocompatible Gold Nanoparticles for Cancer Theragnosis

Targeted Chemotherapy Delivery via Gold Nanoparticles: A Scoping Review of In Vivo Studies

In the field of oncology, a lot of improvements in nanotechnology creates support for better diagnosis and therapeutic opportunities, and due to their physical and chemical properties, gold nanoparticles are highly applicable. We performed a literature review on the studies engaging the usage of gold nanoparticles on murine models with a focus on the type of the carrier, the chemotherapy drug, the target tumoral tissue and outcomes. We identified fifteen studies that fulfilled our search criteria, in which we analyzed the synthesis methods, the most used chemotherapy conjugates of gold nanoparticles in experimental cancer treatment, as well as the improved impact on tumor size and system toxicity. Due to their intrinsic traits, we conclude that chemotherapy conjugates of gold nanoparticles are promising in experimental cancer treatment and may prove to be a safer and improved therapy option than current alternatives.

Facile Green, Room-Temperature Synthesis of Gold Nanoparticles Using Combretum erythrophyllum Leaf Extract: Antibacterial and Cell Viability Studies against Normal and Cancerous Cells

We herein report a facile, green, cost-effective, plant-mediated synthesis of gold nanoparticles (AuNPs) for the first time using Combretum erythrophyllum (CE) plant leaves. The synthesis was conducted at room temperature using CE leaf extract serving as a reducing and capping agent. The as-synthesized AuNPs were found to be crystalline, well dispersed, and spherical in shape with an average diameter of 13.20 nm and an excellent stability of over 60 days. The AuNPs showed broad-spectrum antibacterial activities against both pathogenic Gram-positive (Staphylococcus epidermidis (ATCC14990), Staphylococcus aureus (ATCC 25923), Mycobacterium smegmatis (MC 215)) and Gram-negative bacteria (Proteus mirabilis (ATCC 7002), Escherichia coli (ATCC 25922), Klebsiella pneumoniae (ATCC 13822), Klebsiella oxytoca (ATCC 8724)), with a minimum inhibition concentration of 62.5 µg/mL. In addition, the as-synthesized AuNPs were highly stable with exceptional cell viability towards normal cells (BHK- 21) and cancerous cancer cell lines (cervical and lung cancer).

A novel synthesis of a chlorophyll b-gold nanoconjugate used for enhancing photodynamic therapy: In vitro study

Chlorophyll, the essential green pigment in plants, is considered a promising natural photosensitizer (PS) for photodynamic therapy (PDT). However, it suffers from lower stability in the physiological conditions that depress its efficacy in the PDT. The combination of nanotechnology and PDT is becoming a promising approach to combat tumors. Gold nanoparticles (Au NPs), for example, are proposed as suitable carriers that can increase chlorophyll stability when conjugating together. In the present work, the impact of Au NPs conjugation in enhancing Chlorophyll b (Chl b) efficiency in the PDT of cancer cells has been emphasized. A chemical method using a natural product synthesized a novel Chlorophyll b-gold nanoparticles nanoconjugate (Chl b-Au NCs). The synthesized Chl b-Au NCs were characterized via UV-Vis spectroscopy, Fourier-transform infrared spectroscopy (FTIR), Laser-Induced Fluorescence (LIF), Zeta potential, Dynamic light scattering (DLS), and Transmission electron microscopy (TEM). Chl b is characterized by a formyl group (CHO) which is absent in Chl a. This group leads to the formation of an electrostatic reaction between the positive charge of Chl b and the negative charge present on the surface of the gold nanoparticles. Moreover, Chlorophyll b loading on the biosynthesized gold nanoparticles (Au NPs) increases its photostability. The efficiency of the PDT was then studied on the MCF7 and the HepG2 cells using this conjugation. As a result, the prepared Chl b-Au NCs showed low dark toxicity, excellent photostability under laser irradiation of wavelength 650 nm, in addition to a significantly high PDT efficacy against tumor cells in vitro. This is due to the enhanced cellular uptake and the high reactive oxygen species (ROS) production upon laser irradiation. Therefore, the designed Chl b-Au NCs could be a photo-therapeutic agent for enhancing cancer therapy in future applications.

Distribution of Gold Nanoparticles in the Anterior Chamber of the Eye after Intracameral Injection for Glaucoma Therapy

In glaucoma therapy, nanoparticles (NPs) are a favorable tool for delivering drugs to the outflow tissues of the anterior chamber of the eye where disease development and progression take place. In this context, a prerequisite is an efficient enrichment of NPs in the trabecular meshwork with minimal accumulation in off-target tissues such as the cornea, lens, iris and ciliary body. We evaluated the optimal size for targeting the trabecular meshwork by using gold NPs of 5, 60, 80 and 120 nm with a bare surface (AuNPs) or coated with hyaluronic acid (HA-AuNPs). NPs were compared regarding their colloidal stability, distribution in the anterior chamber of the eye ex vivo and cellular uptake in vitro. HA-AuNPs demonstrated an exceptional colloidal stability. Even after application into porcine eyes ex vivo, the HA coating prevented an aggregation of NPs inside the trabecular meshwork. NPs with a diameter of 120 nm exhibited the highest volume-based accumulation in the trabecular meshwork. Off-target tissues in the anterior chamber demonstrated an exceptionally low gold content. Our findings are particularly important for NPs with encapsulated anti-glaucoma drugs because a higher particle volume would be accompanied by a higher drug payload.

Study of the interactions of gold nanoparticles functionalized with aminolevulinic acid in membrane models

Gold nanoparticles have been intensively studied in cancer therapy to improve drug release, increasing therapeutic action and reducing adverse effects. The interaction between gold nanoparticles and cell membranes can give information about the cell internalization. In this study, gold nanoparticles with aminolevulinic acid (5-ALA) were synthesized using the photoreduction method (5-ALA: AuNPs). The prodrug 5-ALA is responsible for protoporphyrin IX synthesis inside the cell and allows the use of therapies as photodynamic and sonodynamic therapies. The cytotoxicity test was performed on a breast cancer tumor line (MCF-7), and high Content Screening assay was applied to evaluate the entry of nanoparticles into cells. DPPS Langmuir monolayers were assembled at the air/water interface and employed as a simplified membrane model for half of a tumorigenic cell membrane. We assessed the molecular interactions between 5-ALA: AuNPs and phospholipids using tensiometry (π-A isotherms) and vibrational spectroscopy (PM-IRRAS) experiments. We found that the functionalized gold nanoparticles strongly interact with DPPS polar head groups (especially phosphate and carbonyl), changing the phospholipid hydration and leading to a general decrease in the monolayer conformational order. This work then probes that specific interaction between 5-ALA: AuNPs and the negatively charged phospholipid can be assessed using Langmuir monolayers as simplified biomembrane models.

Optical properties and stability of small hollow gold nanoparticles

In the current work, small hollow Au nanoparticles (d ≈ 16 nm) with excellent thermal stability and high photo-thermal conversion efficiency, which have great potential for use in photo-thermal cancer therapy, were prepared through galvanic replacement reaction between Ag nano-templates and gold salt. The position of surface plasmon resonance (SPR) bands for these nanoparticles could be tuned by varying the amount of gold salt. The hydrophobic hollow nanostructures were made water-dispersible by being encapsulated with poly(maleic anhydride-alt-1-octadecene) - PMAO. The obtained nanostructures were stable in an aqueous solution of NaCl with concentration up to 280 mM. The hollow gold nanoparticles (HGNPs) were then heated using an 808 nm laser at different power densities, the obtained data showed that they are highly photo-thermal stable under a high power density laser up to 1.6 W cm^-2 after three circles of irradiation at 20 min per circle (20 min continuous irradiation for each circle). The facile synthesis of small size HGNPs with a plasmon peak in the near infrared range, colloidal and photo-thermal stability, and high capacity of conversion of photon energy into heat makes them a promising material for photo-thermal and imaging applications.

Augmented Therapeutic Potential of Glutaminase Inhibitor CB839 in Glioblastoma Stem Cells Using Gold Nanoparticle Delivery

Gold nanoparticles (Au NPs) are studied as delivery systems to enhance the effect of the glutaminase1 inhibitor CB839, a promising drug candidate already in clinical trials for tumor treatments. Au NPs were synthesized using a bottom-up approach and covered with polymers able to bind CB839 as a Au-polymer-CB839 conjugate. The drug loading efficiency (DLE) was determined using high-performance liquid chromatography and characterization of the CB839-loaded NPs was done with various microscopic and spectroscopic methods. Despite the chemical inertness of CB839, Au NPs were efficient carriers with a DLE of up to 12%, depending on the polymer used. The therapeutic effect of CB839 with and without Au was assessed in vitro in 2D and 3D glioblastoma (GBM) cell models using different assays based on the colony formation ability of GBM stem cells (GSCs). To avoid readout disturbances from the Au metal, viability methods which do not require optical detection were hereby optimized. These showed that Au NP delivery increased the efficacy of CB839 in GSCs, compared to CB839 alone. Fluorescent microscopy proved successful NP penetration into the GSCs. With this first attempt to combine CB839 with Au nanotechnology, we hope to overcome delivery hurdles of this pharmacotherapy and increase bioavailability in target sites.

Photothermal therapy with silver nanoplates in HeLa cells studied by in situ fluorescence microscopy

Photothermal therapy (PTT) is a noninvasive treatment for cancer relying on the incorporation of NIR-light absorbing nanomaterials into cells, which upon illumination release heat causing thermally induced cell death. We prove that irradiation of aqueous suspensions of poly(vinylpyrrolidone)-coated silver nanoplates (PVPAgNP) or PVPAgNP in HeLa cells with red or NIR lasers causes a sizeable photothermal effect, which in cells can be visualized with the temperature sensing fluorophore Rhodamine B (RhB) using spinning disk confocal fluorescence microscopy or fluorescence lifetime imaging. Upon red-light irradiation of cells that were incubated with both, RhB and PVPAgNP at concentrations with no adverse effects on cell viability, a substantial heat release is detected. Initiation of cell death by photothermal effect is observed by positive signals of fluorescent markers for early and late apoptosis. Surprisingly, a new nanomaterial-assisted cell killing mode is operating when PVPAgNP-loaded HeLa cells are excited with moderate powers of fs-pulsed NIR light. Small roundish areas are generated with bright and fast (<1 ns) decaying emission, which expand fast and destroy the whole cell in seconds. This characteristic emission is assigned to efficient optical breakdown initiation around the strongly absorbing PVPAgNP leading to plasma formation that spreads fast through the cell.

Saccorhiza polyschides used to synthesize gold and silver nanoparticles with enhanced antiproliferative and immunostimulant activity

Over the last years, there has been an increasing trend towards the use of environmentally friendly processes to synthesize nanomaterials. In the case of nanomedicine, the use of bionanofactories with associated biological properties, such as seaweed, has emerged as a promising field of work due to the possibility they open for both the preservation of those properties in the nanomaterials synthesized and/or the reduction of their toxicity. In the present study, gold (Au@SP) and silver (Ag@SP) nanoparticles were synthesized using an aqueous extract of Saccorhiza polyschides (SP). Several techniques showed that the nanoparticles formed were spherical and stable, with mean diameters of 14 ± 2 nm for Au@SP and 15 ± 3 nm for Ag@SP. The composition of the biomolecules in the extract and the nanoparticles were also analyzed. The analyses performed indicate that the extract acts as a protective medium, with the particles embedded in it preventing aggregation and coalescence. Au@SP and Ag@SP showed superior immunostimulant and antiproliferative activity on immune and tumor cells, respectively, to that of the SP extract. Moreover, the nanoparticles were able to modulate the release of reactive oxygen species depending on the concentration. Hence, both nanoparticles have a significant therapeutic potential for the treatment of cancer or in immunostimulant therapy.

Plasmonic Nanocomposite Implants for Interstitial Thermotherapy: Experimental and Computational Analysis

The ferromagnetic implant (thermoseeds) technique offers desirable features for interstitial thermotherapy. However, its efficacy has been reported to be limited by issues that are related to the properties of the metal alloys that are used to fabricate them and the high number of thermoseeds needed to achieve therapeutic temperature levels. Here, we present the results of a combination of experimental and computational analysis of plasmonic nanocomposite implants (photoseeds)—a combination of Au nanoparticles (NPs) and poly-dimethylsiloxane (PDMS)—as a model material. We performed structural and optical characterization of the Au NPs and repared Au-PDMS nanocomposites, followed by an elucidation of the heat generation capabilities of the Au-PDMS photoseeds in aqueous solution and in-vitro cancer cell suspension. Based on the experimental results, we developed a three-dimensional (3D) finite element method (FEM) model to predict in-vivo thermal damage profiles in breast tissue. The optical absorbance of the Au-PDMS photoseeds were increasing with the concentration of Au NPs. The photothermal measurements and the in-vivo predictions showed that the photothermal properties of the photoseeds, characteristics of the laser sources, and the duration of heating can be tuned to achieve therapeutic temperature levels under in-vitro and in-vivo conditions. Collectively, the results demonstrate the feasibility of using photoseeds for interstitial thermotherapy.

Nanoporous Gold Monolith for High Loading of Unmodified Doxorubicin and Sustained Co-Release of Doxorubicin-Rapamycin

Nanoparticles (NPs) have been widely explored for delivering doxorubicin (DOX), an anticancer drug, to minimize cardiotoxicity. However, their efficiency is marred by a necessity to chemically modify DOX, NPs, or both and low deposition of the administered NPs on tumors. Therefore, alternative strategies should be developed to improve therapeutic efficacy and decrease toxicity. Here we report the possibility of employing a monolithic nanoporous gold (np-Au) rod as an implant for delivering DOX. The np-Au has very high DOX encapsulation efficiency (>98%) with maximum loading of 93.4 mg cm-3 without any chemical modification required of DOX or np-Au. We provide a plausible mechanism for the high loading of DOX in np-Au. The DOX sustained release for 26 days from np-Au in different pH conditions at 37 °C, which was monitored using UV-Vis spectroscopy. Additionally, we encased the DOX-loaded np-Au with rapamycin (RAPA)-trapped poly(D,L-lactide-co-glycolide) (PLGA) to fabricate an np-Au@PLGA/RAPA implant and optimized the combinatorial release of DOX and RAPA. Further exploiting the effect of the protein corona around np-Au and np-Au@PLGA/RAPA showed zero-order release kinetics of DOX. This work proves that the np-Au-based implant has the potential to be used as a DOX carrier of potential use in cancer treatment.

A DNA nanosensor for monitoring ligand-induced i-motif formation

A GNP-based DNA nanosensor has been developed that identifies i-motif inducing ligands at physiological pH from a chemical library.

Metal Nanoparticles for Electrochemical Sensing: Progress and Challenges in the Clinical Transition of Point-of-Care Testing

With the rise in public health awareness, research on point-of-care testing (POCT) has significantly advanced. Electrochemical biosensors (ECBs) are one of the most promising candidates for the future of POCT due to their quick and accurate response, ease of operation, and cost effectiveness. This review focuses on the use of metal nanoparticles (MNPs) for fabricating ECBs that has a potential to be used for POCT. The field has expanded remarkably from its initial enzymatic and immunosensor-based setups. This review provides a concise categorization of the ECBs to allow for a better understanding of the development process. The influence of structural aspects of MNPs in biocompatibility and effective sensor design has been explored. The advances in MNP-based ECBs for the detection of some of the most prominent cancer biomarkers (carcinoembryonic antigen (CEA), cancer antigen 125 (CA125), Herceptin-2 (HER2), etc.) and small biomolecules (glucose, dopamine, hydrogen peroxide, etc.) have been discussed in detail. Additionally, the novel coronavirus (2019-nCoV) ECBs have been briefly discussed. Beyond that, the limitations and challenges that ECBs face in clinical applications are examined and possible pathways for overcoming these limitations are discussed.

Interactions of Zinc Oxide Nanostructures with Mammalian Cells: Cytotoxicity and Photocatalytic Toxicity

This article presents a state-of-the-art review and analysis of literature studies on the morphological structure, fabrication, cytotoxicity, and photocatalytic toxicity of zinc oxide nanostructures (nZnO) of mammalian cells. nZnO with different morphologies, e.g., quantum dots, nanoparticles, nanorods, and nanotetrapods are toxic to a wide variety of mammalian cell lines due to in vitro cell-material interactions. Several mechanisms responsible for in vitro cytotoxicity have been proposed. These include the penetration of nZnO into the cytoplasm, generating reactive oxygen species (ROS) that degrade mitochondrial function, induce endoplasmic reticulum stress, and damage deoxyribonucleic acid (DNA), lipid, and protein molecules. Otherwise, nZnO dissolve extracellularly into zinc ions and the subsequent diffusion of ions into the cytoplasm can create ROS. Furthermore, internalization of nZnO and localization in acidic lysosomes result in their dissolution into zinc ions, producing ROS too in cytoplasm. These ROS-mediated responses induce caspase-dependent apoptosis via the activation of B-cell lymphoma 2 (Bcl2), Bcl2-associated X protein (Bax), CCAAT/enhancer-binding protein homologous protein (chop), and phosphoprotein p53 gene expressions. In vivo studies on a mouse model reveal the adverse impacts of nZnO on internal organs through different administration routes. The administration of ZnO nanoparticles into mice via intraperitoneal instillation and intravenous injection facilitates their accumulation in target organs, such as the liver, spleen, and lung. ZnO is a semiconductor with a large bandgap showing photocatalytic behavior under ultraviolet (UV) light irradiation. As such, photogenerated electron-hole pairs react with adsorbed oxygen and water molecules to produce ROS. So, the ROS-mediated selective killing for human tumor cells is beneficial for cancer treatment in photodynamic therapy. The photoinduced effects of noble metal doped nZnO for creating ROS under UV and visible light for killing cancer cells are also addressed.