Gold nanoparticle-mediated generation of reactive oxygen species during plasmonic photothermal therapy: a comparative study for different particle sizes, shapes, and surface conjugations

Strategies Employed to Design Biocompatible Metal Nanoparticles for Medical Science and Biotechnology Applications

The applicability of nanomaterials has evolved in biomedical domains thanks to advances in biocompatibility strategies and the mitigation of cytotoxic effects, allowing diagnostics, imaging, and therapeutic approaches. The application of nanoparticles (NP), particularly metal nanoparticles (mNPs), such as gold (Au) and silver (Ag), includes inherent challenges related to the material characteristics, surface modification, and bioconjugation techniques. By tailoring the surface properties through appropriate coating with biocompatible molecules or functionalization with active biomolecules, researchers can reach a harmonious interaction with biological systems or samples (mostly fluids or tissues). Thus, this review highlights the mechanisms associated with the obtention of biocompatible mNP and presents a comprehensive overview of methods that facilitate safe and efficient production. Therefore, we consider this review to be a valuable resource for all researchers navigating this dynamic field.

NIR-triggered arsenic-loaded layered double hydroxide-based films for localized thermal synergistic chemotherapy

Portal vein tumor thrombus (PVTT) formed by cancer cell invasion is a major cause of high mortality in hepatocellular carcinoma (HCC), and the formation of thrombus will be accelerated by bacterial colonization on the surface of the implant after surgery. In this work, Polypyrrole-coated arsenic-loaded layered double hydroxide films were in situ constructed on the nickel-titanium alloy for the efficient killing of tumour cells by thermo-therapeutic synergistic chemotherapy. The good near-infrared photothermal conversion ability of polypyrrole enables the sample surface temperature to be raised to about 51 °C at a low photothermal power (0.5 w/cm2), while the elevated temperature could further accelerate the release of drug arsenic. In addition, when NIR light is not applied, the polypyrrole coating also cleverly acts as a "barrier layer" to reduce the natural release of arsenic in normal tissues to avoid toxicity issues. In vivo and in vitro experiments have demonstrated that the platform exhibits excellent antitumor and antibacterial abilities. In contrast to the systemic toxicity issues associated with systemic circulation of nanotherapeutic drugs, this in situ functional film is expected to be used in localised interventions for precise drug delivery, and is also more suitable for surgical treatment scenarios in PVTT surgeries.

Advances in smart nanotechnology-supported photodynamic therapy for cancer

Cancer has emerged as a formidable challenge in the 21st century, impacting society, public health, and the economy. Conventional cancer treatments often exhibit limited efficacy and considerable side effects, particularly in managing the advanced stages of the disease. Photodynamic therapy (PDT), a contemporary non-invasive therapeutic approach, employs photosensitizers (PS) in conjunction with precise light wavelengths to selectively target diseased tissues, inducing the generation of reactive oxygen species and ultimately leading to cancer cell apoptosis. In contrast to conventional therapies, PDT presents a lower incidence of side effects and greater precision in targeting. The integration of intelligent nanotechnology into PDT has markedly improved its effectiveness, as evidenced by the remarkable synergistic antitumor effects observed with the utilization of multifunctional nanoplatforms in conjunction with PDT. This paper provides a concise overview of the principles underlying PS and PDT, while also delving into the utilization of nanomaterial-based PDT in the context of cancer treatment.

Hybrid nanopotentiators with dual cascade amplification for glioma combined interventional therapy

Glioma is an aggressive malignant brain tumor with a very poor prognosis for survival. The poor tumor targeting efficiency and tumor microenvironment penetration barrier also as troubles inhibited the effective glioma chemotherapy. Here, we design a core-shell structure cascade amplified hybrid catalytic nanopotentiators CFpAD with DM1 encapsulated to overcome the glioma therapeutic obstacles. NIR laser-based BBB penetrating enhances the tumor accumulation of CFpAD. When CFpAD, as the cascade amplified drug, is treated on the cancer cells, the bomb-like CFpAD releases gold nanoparticles as glucose oxidase (GOx) and ferric oxide nanoparticles (FNPs) as peroxides (POx) after blasting, producing ROS via a cascade amplification for tumor cell apoptosis. Gold nanoparticles can rest CAFs and reduce ECM secretion, achieving deep penetration of CFpAD. Moreover, CFpAD also cuts off the nutritional supply of the tumor, reduces the pH value, and releases free radicals to destroy the cancer. The glioma cell viability was significantly decreased through DNA damage and ROS aggregation due to the DM1-based chemotherapy synergistically combined with interventional photothermal therapy (IPTT) and radiotherapy (RT). This domino cascade amplified loop, combined with starvation therapy with IPTT and RT, has good tumor penetration and outstanding antitumor efficacy, and is a promising glioma treatment system.

Development of pH-responsive porphyran-coated gold nanorods for tumor photothermal and immunotherapy

Cancer poses a significant threat to human health, and monotherapy frequently fails to achieve optimal therapeutic outcomes. Based on this premise, porphyran (PHP), a marine polysaccharide with immunomodulatory function, was used as a framework to coat gold nanorods and construct a novel nanomedicine (PHP-MPBA-GNRs) combining photothermal therapy and immunotherapy. In this design, PHP not only maintained the dispersion stability and photothermal stability of gold nanorods but also could be released under weakly acidic conditions to activate anti-tumor immunity. In vivo studies have shown that PHP-MPBA-GNRs can effectively inhibit tumor cell proliferation and reduce metastasis under near-infrared (NIR) light irradiation. Preliminary mechanistic investigations revealed that PHP-MPBA-GNRs could increase reactive oxygen species (ROS) and induce apoptosis in cancer cells. The PHP in PHP-MPBA-GNRs can also activate dendritic cells and up-regulate the expression of co-stimulatory molecules and antigen-presenting complexes. All biological experiments, including in vivo tests, demonstrated that PHP-MPBA-GNRs achieved a combination of photothermal therapy and immunotherapy for tumors.

Bonding states of gold/silver plasmonic nanostructures and sulfur-containing active biological ingredients in biomedical applications: a review

As one of the most instrumental components in the architecture of advanced nanomedicines, plasmonic nanostructures (mainly gold and silver nanomaterials) have been paid a lot of attention. This type of nanomaterial can absorb light photons with a specific wavelength and generate heat or excited electrons through surface resonance, which is a unique physical property. In innovative biomaterials, a significant number of theranostic (therapeutic and diagnostic) materials are produced through the conjugation of thiol-containing ingredients with gold and silver nanoparticles (Au and Ag NPs). Hence, it is essential to investigate Au/Ag-S interfaces precisely and determine the exact bonding states in the active nanobiomaterials. This study intends to provide useful insights into the interactions between Au/Ag NPs and thiol groups that exist in the structure of biomaterials. In this regard, the modeling of Au/Ag-S bonding in active biological ingredients is precisely reviewed. Then, the physiological stability of Au/Ag-based plasmonic nanobioconjugates in real physiological environments (pharmacokinetics) is discussed. Recent experimental validation and achievements of plasmonic theranostics and radiolabelled nanomaterials based on Au/Ag-S conjugation are also profoundly reviewed. This study will also help researchers working on biosensors in which plasmonic devices deal with the thiol-containing biomaterials (e.g., antibodies) inside blood serum and living cells.

Laser-Synthesized Germanium Nanoparticles as Biodegradable Material for Near-Infrared Photoacoustic Imaging and Cancer Phototherapy

Biodegradable nanomaterials can significantly improve the safety profile of nanomedicine. Germanium nanoparticles (Ge NPs) with a safe biodegradation pathway are developed as efficient photothermal converters for biomedical applications. Ge NPs synthesized by femtosecond-laser ablation in liquids rapidly dissolve in physiological-like environment through the oxidation mechanism. The biodegradation of Ge nanoparticles is preserved in tumor cells in vitro and in normal tissues in mice with a half-life as short as 3.5 days. Biocompatibility of Ge NPs is confirmed in vivo by hematological, biochemical, and histological analyses. Strong optical absorption of Ge in the near-infrared spectral range enables photothermal treatment of engrafted tumors in vivo, following intravenous injection of Ge NPs. The photothermal therapy results in a 3.9-fold reduction of the EMT6/P adenocarcinoma tumor growth with significant prolongation of the mice survival. Excellent mass-extinction of Ge NPs (7.9 L g-1 cm-1 at 808 nm) enables photoacoustic imaging of bones and tumors, following intravenous and intratumoral administrations of the nanomaterial. As such, strongly absorbing near-infrared-light biodegradable Ge nanomaterial holds promise for advanced theranostics.

Gold nanoparticles-mediated photothermal and photodynamic therapies for cancer

Cancer remains one of the major causes of death globally, with one out of every six deaths attributed to the disease. The impact of cancer is felt on psychological, physical, and financial levels, affecting individuals, communities, and healthcare institutions. Conventional cancer treatments have many challenges and inadequacies. Nanomedicine, however, presents a promising solution by not only overcoming these problems but also offering the advantage of combined therapy for treatment-resistant cancers. Nanoparticles specifically engineered for use in nanomedicine can be efficiently targeted to cancer cells through a combination of active and passive techniques, leading to superior tumor-specific accumulation, enhanced drug availability, and reduced systemic toxicity. Among various nanoparticle formulations designed for cancer treatment, gold nanoparticles have gained prominence in the field of nanomedicine due to their photothermal, photodynamic, and immunologic effects without the need for photosensitizers or immunotherapeutic agents. To date, there is no comprehensive literature review that focuses on the photothermal, photodynamic, and immunologic effects of gold nanoparticles. In this review, significant attention has been devoted to examining the parameters pertaining to the structure of gold nanoparticles and laser characteristics, which play a crucial role in influencing the efficacy of photothermal therapy (PTT) and photodynamic therapy (PDT). Moreover, this article provides insights into the success of PTT and PDT mediated by gold nanoparticles in primary cancer treatment, as well as the immunological effects of PTT and PDT on metastasis and recurrence, providing a promising strategy for cancer therapy. In summary, gold nanoparticles, with their unique properties, have the potential for clinical application in various cancer therapies, including the treatment of primary cancer, recurrence and metastasis.

Phytosynthesis of gold-198 nanoparticles for a potential therapeutic radio-photothermal agent

We produced spherical gold-198 nanoparticles with an average size of 41 nm, good stability, and high radiochemical purity for a promising single agent of radio-photothermal therapy using Curcuma longa rhizome extract as a reducing and capping agent. The combination of in vitro treatment using gold-198 nanoparticles and irradiation of 980 nm wavelength lasers with a power output of 2 W/cm2 induced hyperthermia temperature and exhibited enhancement of the percentage dead on MDA-MB-123 cancer cells compared to gold-198 nanoparticles alone.

The diverse effects of cisplatin on tumor microenvironment: Insights and challenges for the delivery of cisplatin by nanoparticles

Cisplatin is a well-known platinum-based chemotherapy medication that is widely utilized for some malignancies. Despite the direct cytotoxic consequences of cisplatin on tumor cells, studies in the recent decade have revealed that cisplatin can also affect different cells and their secretions in the tumor microenvironment (TME). Cisplatin has complex impacts on the TME, which may contribute to its anti-tumor activity or drug resistance mechanisms. These regulatory effects of cisplatin play a paramount function in tumor growth, invasion, and metastasis. This paper aims to review the diverse impacts of cisplatin and nanoparticles loaded with cisplatin on cancer cells and also non-cancerous cells in TME. The impacts of cisplatin on immune cells, tumor stroma, cancer cells, and also hypoxia will be discussed in the current review. Furthermore, we emphasize the challenges and prospects of using cisplatin in combination with other adjuvants and therapeutic modalities that target TME. We also discuss the potential synergistic effects of cisplatin with immune checkpoint inhibitors (ICIs) and other agents with anticancer potentials such as polyphenols and photosensitizers. Furthermore, the potential of nanoparticles for targeting TME and better delivery of cisplatin into tumors will be discussed.

Plasmonic porous micro- and nano-materials based on Au/Ag nanostructures developed for photothermal cancer therapy: challenges in clinicalization

Photothermal therapy (PTT) has developed in recent decades as a relatively safe method for the treatment of cancers. Recently, various species of gold and silver (Au and Ag) nanostructures have been developed and investigated to achieve PTT due to their highly localized surface plasmon resonance (LSPR) effect. Concisely, the collective oscillation of electrons on the surface of Au and Ag nanostructures upon exposure to a specific wavelength (depending on their size and shape) and further plasmonic resonance leads to the heating of the surface of these particles. Hence, porous species can be equipped with tiny plasmonic ingredients that add plasmonic properties to therapeutic cargoes. In this case, a precise review of the recent achievements is very important to figure out to what extent plasmonic photothermal therapy (PPTT) by Au/Ag-based plasmonic porous nanomedicines successfully treated cancers with satisfactory biosafety. Herein, we classify the various species of LSPR-active micro- and nano-materials. Moreover, the routes for the preparation of Ag/Au-plasmonic porous cargoes and related bench assessments are carefully reviewed. Finally, as the main aim of this study, principal requirements for the clinicalization of Ag/Au-plasmonic porous cargoes and their further challenges are discussed, which are critical for specialists in this field.

Functionalized Gold Nanoparticles Suppress the Proliferation of Human Lung Alveolar Adenocarcinoma Cells by Deubiquitinating Enzymes Inhibition

Functionalized gold nanoparticles (AuNPs) are widely used in therapeutic applications, but little is known regarding the impact of their surface functionalization in the process of toxicity against cancer cells. This study investigates the anticancer effects of 5 nm spherical AuNPs functionalized with tannate, citrate, and PVP on deubiquitinating enzymes (DUBs) in human lung alveolar adenocarcinoma (A549) cells. Our findings show that functionalized AuNPs reduce the cell viability in a concentration- and time-dependent manner as measured by modified lactate dehydrogenase (mLDH) and 3-[4,5-dimethylthiazole-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assays. An increased generation of intracellular reactive oxygen species (ROS) and depletion of glutathione (GSH/GSSG) ratio was observed with the highest AuNP concentration of 10 μg/mL. The expression of DUBs such as ubiquitin specific proteases (USP7, USP8, and USP10) was slightly inhibited when treated with concentrations above 2.5 μg/mL. Moreover, functionalized AuNPs showed an inhibitory effect on protein kinase B/mammalian target of rapamycin (PI3K/AKT/mTOR) and wingless-related integration site (Wnt) signaling proteins, and this could further trigger mitochondrial related-apoptosis by the upregulation of caspase-3, caspase-9, and PARP in A549 cells. Furthermore, our study shows a mechanistic understanding of how functionalized AuNPs inhibit the DUBs, consequently suppressing cell proliferation, and can be modulated as an approach toward anticancer therapy. The study also warrants the need for future work to investigate the effect of functionalized AuNPs on DUB on other cancer cell lines both in vitro and in vivo.

Palladium Nanocapsules for Photothermal Therapy in the Near-Infrared II Biological Window

Recent developments in nanomaterials with programmable optical responses and their capacity to modulate the photothermal effect induced by an extrinsic source of light have elevated plasmonic photothermal therapy (PPTT) to the status of a favored treatment for a variety of malignancies. However, the low penetration depth of near-infrared-I (NIR-I) lights and the need to expose the human body to a high laser power density in PPTT have restricted its clinical translation for cancer therapy. Most nanostructures reported to date exhibit limited performance due to (i) activity only in the NIR-I region, (ii) the use of intense laser, (iii) need of large concentration of nanomaterials, or (iv) prolonged exposure times to achieve the optimal hyperthermia state for cancer phototherapy. To overcome these shortcomings in plasmonic nanomaterials, we report a bimetallic palladium nanocapsule (Pd Ncap)─with a solid gold bead as its core and a thin, perforated palladium shell─with extinction both in the NIR-I as well as the NIR-II region for PPTT applications toward cancer therapy. The Pd Ncap demonstrated exceptional photothermal stability with a photothermal conversion efficiency of ∼49% at the NIR-II (1064 nm) wavelength region at a very low laser power density of 0.5 W/cm2. The nanocapsules were further surface-functionalized with Herceptin (Pd Ncap-Her) to target the breast cancer cell line SK-BR-3 and exploited for in vitro PPTT applications using NIR-II light. Pd Ncap-Her caused more than 98% cell death at a concentration of just 50 μg/mL and a laser power density of 0.5 W/cm2 with an output power of only 100 mW. Flow cytometric and microscopic analyses revealed that Pd Ncap-Her-induced apoptosis in the treated cancer cells during PPTT. Additionally, Pd Ncaps were found to have reactive oxygen species (ROS) scavenging ability, which can potentially reduce the damage to cells or tissues from ROS produced during PPTT. Also, Pd Ncap demonstrated excellent in vivo biocompatibility and was highly efficient in photothermally ablating tumors in mice. With a high photothermal conversion and killing efficiency at very low nanoparticle concentrations and laser power densities, the current nanostructure can operate as an effective phototherapeutic agent for the treatment of different cancers with ROS-protecting ability.

Functionalized Metal Nanoparticles in Cancer Therapy

Currently, there are many studies on the application of nanotechnology in therapy. Metallic nanoparticles are promising nanomaterials in cancer therapy; however, functionalization of these nanoparticles with biomolecules has become relevant as their effect on cancer cells is considerably increased by photothermal and photodynamic therapies, drug nanocarriers, and specificity by antibodies, resulting in new therapies that are more specific against different types of cancer. This review describes studies on the effect of functionalized palladium, gold, silver and platinum nanoparticles in the treatment of cancer, these nanoparticles themselves show an anticancer effect. This effect is further enhanced when the NPs are functionalized with either antibodies, DNA, RNA, peptides, proteins, or folic acid and other molecules. These NPs can penetrate the cell and accumulate in the tumor tissue, resulting in a cytotoxic effect through the generation of ROS, the induction of apoptosis, cell cycle arrest, DNA fragmentation, and a photothermal effect. NP-based therapy is a new strategy that can be used synergistically with chemotherapy and radiotherapy to achieve more effective therapies and reduce side effects.

Influence of Cell Type on the Efficacy of Plasmonic Photothermal Therapy

In plasmonic photothermal therapy (PPTT), illuminated gold nanoparticles are locally heated to produce selective damage in cells. While PPTT is expected to strongly depend on the cell line, available data are sparse and critical parameters remain unclear. To elucidate this pivotal aspect, we present a systematic study of diseased and nondiseased cells from different tissues to evaluate cytotoxicity, uptake of gold nanorods (AuNRs), and viability after PPTT. We identified differences in uptake and toxicity between cell types, linking AuNR concentrations to toxicity. Furthermore, the cell death mechanism is shown to depend on the intensity of the irradiated light and hence the temperature increase. Importantly, the data also underline the need to monitor cell death at different time points. Our work contributes to the definition of systematic protocols with appropriate controls to fully comprehend the effects of PPTT and build meaningful and reproducible data sets, key to translate PPTT to clinical settings.

CD44-Receptor Targeted Gold-Doxorubicin Nanocomposite for Pulsatile Chemo-Photothermal Therapy of Triple-Negative Breast Cancer Cells

This study reports the CD44 receptor-targeted gold-doxorubicin nanocomposite (TGNC-DOX) for pulsatile chemo-photothermal therapy of triple-negative breast cancer (TNBC). The developed TGNC-DOX was nanometric, having a particle size of 71.34 ± 3.66 nm. The doxorubicin was loaded by electrostatic interaction with high entrapment and loading efficiency (>75%). TGNC-DOX showed potent photothermal response and reversible photothermal stability following irradiation with 808 nm NIR laser irradiation. Further, TGNC-DOX showed laser-responsive and pH-dependent drug release behavior suggesting its suitability for chemo-photothermal therapy, specifically at the tumor microenvironment site. Cellular viability, cellular uptake, ROS generation, and apoptosis assays suggested selective localization of TGNC-DOX in cancer cells that showed a significant cytotoxic effect against MDA-MB-231 breast cancer cells. Moreover, the developed TGNC-DOX showed ferroptosis in MDA-MB-231 cells. The event of TGNC-DOX-mediated thermal ablation is marked by a significant generation of reactive oxygen species (ROS) and apoptosis, as affirmed by flow cytometry. NIR-808 laser-responsive photothermal therapy of cancer cells was found to be more effective than without NIR-808 laser-treated cells, suggesting the fundamental role of photothermal ablation. The outcome concludes developed TGNC-DOX is a novel and potential tool to mediate laser-guided chemo-photothermal ablation treatment of cancer cells.

Nanomaterial-enabled photothermal-based solar water disinfection processes: Fundamentals, recent advances, and mechanisms

The pathogenic microorganisms in water pose a great threat to human health. Photothermal and photothermocatalytic disinfection using nanomaterials (NPs) has offered a promising and effective strategy to address the challenges in solar water disinfection (SODIS), especially in the point-of-use operations. This review aims at providing comprehensive and state-of-the-art knowledge of photothermal-based disinfection by NPs. The fundamentals and principles of photothermal-based disinfection were first introduced. Then, recent advances in developing photothermal/photothermocatalytic catalysts were systematically summarized. The light-to-heat conversion and disinfection performance of a large variety of photothermal materials were presented. Given the complicated mechanisms of photothermal-based disinfection, the attacks from reactive oxygen species and heat, the destruction of bacterial cells, and the antibacterial effects of released metal ions were highlighted. Finally, future challenges and opportunities associated with the development of cost-effective photothermal/photothermocatalytic disinfection systems were outlined. This review will provide guidance in designing future NPs and inspire more research efforts from environmental nano-communities to move towards practical water disinfection operations.

Assessment of the Potential Health Risk of Gold Nanoparticles Used in Nanomedicine

Due to unique properties, nanoparticles (NPs) have become a preferred material in biomedicine. The benefits of their use are indisputable, but their safety and potential toxicity are becoming more and more important. Especially, excessive production of reactive oxygen species (ROS) induced by the strong oxidation potential of metal NPs could evoke adverse effects associated with damage to nucleic acids, proteins and lipids. Our study gives a view on the potential cytotoxicity of gold NPs (Au NPs) of different size from the perspective of the redox state of healthy (HEK 293 T) and cancer (A375 and A594) cell lines. These cells were incubated in the presence of two concentrations of Au NPs for 24 h or 72 h and total antioxidant capacity, 8-isoprostane, and protein carbonyl levels were determined. Furthermore, the activity of antioxidant enzymes such as superoxide dismutase, glutathione peroxidase, and catalase was detected in cell lysates. Our results compared to the results of other laboratories are very contradictory. The outcomes also differ between healthy and cancer cell lines. However, there are certainly changes in the activities of antioxidant enzymes, as well as the damage to biological molecules due to increased NP-induced oxidative stress. But the final decision of the effect of Au NPs on the oxidative state of selected cell lines requires further research.

Comparing extracellular vesicles and cell membranes as biocompatible coatings for gold nanorods: Implications for targeted theranostics

Extracellular vesicles (EVs) and cell membrane nanoghosts are excellent coatings for nanomaterials, providing enhanced delivery in the target sites and evasion of the immune system. These cell-derived coatings allow the exploration of the delivery properties of the nanoparticles without stimulation of the immune system. Despite the advances reported on the use of EVs and cell-membrane coatings for nanomedicine applications, there are no standards to compare the benefits and main differences between these technologies. Here we investigated macrophage-derived EVs and cell membranes-coated gold nanorods and compared both systems in terms of target delivery in cancer and stromal cells. Our results reveal a higher tendency of EV-coated nanorods to interact with macrophages yet both EV and cell membrane-coated nanorods were internalized in the metastatic breast cancer cells. The main differences between these nanoparticles are related to the presence or absence of CD47 in the coating material, not usually addressed in EVs characterization. Our findings highlight important delivery differences exhibited by EVs- or cell membranes- coated nanorods which understanding may be important to the design and development of theragnostic nanomaterials using these coatings for target delivery.

Reactive Oxygen Species Formed by Metal and Metal Oxide Nanoparticles in Physiological Media—A Review of Reactions of Importance to Nanotoxicity and Proposal for Categorization

Diffusely dispersed metal and metal oxide nanoparticles (NPs) can adversely affect living organisms through various mechanisms and exposure routes. One mechanism behind their toxic potency is their ability to generate reactive oxygen species (ROS) directly or indirectly to an extent that depends on the dose, metal speciation, and exposure route. This review provides an overview of the mechanisms of ROS formation associated with metal and metal oxide NPs and proposes a possible way forward for their future categorization. Metal and metal oxide NPs can form ROS via processes related to corrosion, photochemistry, and surface defects, as well as via Fenton, Fenton-like, and Haber–Weiss reactions. Regular ligands such as biomolecules can interact with metallic NP surfaces and influence their properties and thus their capabilities of generating ROS by changing characteristics such as surface charge, surface composition, dissolution behavior, and colloidal stability. Interactions between metallic NPs and cells and their organelles can indirectly induce ROS formation via different biological responses. H₂O₂ can also be generated by a cell due to inflammation, induced by interactions with metallic NPs or released metal species that can initiate Fenton(-like) and Haber–Weiss reactions forming various radicals. This review discusses these different pathways and, in addition, nano-specific aspects such as shifts in the band gaps of metal oxides and how these shifts at biologically relevant energies (similar to activation energies of biological reactions) can be linked to ROS production and indicate which radical species forms. The influences of kinetic aspects, interactions with biomolecules, solution chemistry (e.g., Cl⁻ and pH), and NP characteristics (e.g., size and surface defects) on ROS mechanisms and formation are discussed. Categorization via four tiers is suggested as a way forward to group metal and metal oxide NPs based on the ROS reaction pathways that they may undergo, an approach that does not include kinetics or environmental variations. The criteria for the four tiers are based on the ability of the metallic NPs to induce Fenton(-like) and Haber–Weiss reactions, corrode, and interact with biomolecules and their surface catalytic properties. The importance of considering kinetic data to improve the proposed categorization is highlighted.

Lysosomal activable Vorinostat carrier-prodrug self-assembling with BPQDs enables photothermal oncotherapy to reverse tumor thermotolerance and metastasis

Photothermal therapy (PTT) is becoming increasing prevalent in clinic for eradicating the primary tumor and improving cancer patients' compliance. However, photothermal resistance and distal metastasis still haunt the tumor treatment with PTT. Herein, on the basis that histone deacetylase acetylase inhibitor (HDACis) could activate the expression of anti-tumor gene and accelerate the differentiation and apoptosis of tumor cells, we propose that HDACis supplementing PTT could overcome those obstacles with appropriate drug-controlled release strategy. Thus, we fabricated a nano-complex of lysosomal activable vorinostat (SAHA) carrier-prodrug encapsulating black phosphorus quantum dots (BPQDs@PPS) to counter those challenges in PTT. With spherical morphology and favorable bio-safety, BPQDs@PPS could release BPQDs and Vorinostat spontaneously in lysosome, not only effectively inhibiting tumor growth, but also reversing tumor thermotolerance and metastasis within a PTT procedure. Especially, both western blot and immunofluorescence analysis validate that Vorinostat enables PTT to reverse tumor thermotolerance and distal metastasis by down-regulation of HSP70 and up-regulation of H3. Therefore, this research not only reveals the mechanism how HDACis supplement PTT in reversing tumor thermotolerance and metastasis, but also provides a promising prospect to upgrade clinical photothermal therapy.

Smart Drug Delivery Strategies for Cancer Therapy

Chemotherapy is one of the most widely used strategies to fight cancer, although it has disadvantages such as accumulation in healthy organs and lack of specificity by cancer cells (non-targeted molecules), among others, resulting in adverse effects on patients that limit the dose or follow-up with the same. However, the treatment can also fail due to the resistance mechanisms that cancer cells have to these agents. Because of these limitations, smart drug delivery strategies have been developed to overcome treatment challenges. These smart drug strategies are made with the aim of passively or actively releasing the drug into the tumor environment, increasing the uptake of the chemotherapeutic agent by the cancer cells, thus reducing the adverse effects on other vital organs. Also, these strategies can be guided with molecules on their surface that interact with the tumor microenvironment or with specific receptors on the cancer cell membrane, thus conferring high affinity. This mini review summarizes advances in the development of drug delivery techniques for cancer treatment, including different smart nanocarriers with single or multifunctional stimuli responsiveness. At the same time, we highlight the toxicity and delivery of these strategies in in vivo models. Despite innovation in smart delivery techniques, there are still biodistribution and customization challenges to be overcome in future research.

Effect of Gold Nanostars Plus Amikacin against Carbapenem-Resistant Klebsiella pneumoniae Biofilms

Simple Summary

Carbapenem-resistant Klebsiella pneumoniae (CR-KP) infection rates represent a challenging treatment since the pipeline for effective antibiotics against this pathogen, such as beta-lactams among others, is practically nil. This study aims to evaluate the antibacterial effect of gold nanostars (GNS) alone or associated with some of the most widely used antibiotics for the treatment of CR-KP strains, i.e., meropenem or amikacin, on both planktonic or free-living and sessile forms. GNS were able to inhibit the planktonic growth of CR-KP at 80 µM, to eradicate the bacterial viability at 160 µM, and were unable to inhibit or eradicate the biofilm growth of this bacterium. GNS gave rise to filamentous bacteria through mechanisms mediated by the inhibition of energy-dependent cytoplasmic proteases. The combination of GNS and amikacin was able to inhibit or even eradicate the CR-KP biofilm. This combination was administered to greater wax moth larvae (Galleria mellonella), and this treatment was found to be tolerated well and to prevent the CR-KP infection. Thus, GNS in combination with amikacin represent a promising anti-CR-KP nanomaterial.

Abstract

(1) Background: Carbapenem-resistant Klesiella pneumoniae (CR-KP) infection rates depict an almost pre-antibiotic scenario since the pipeline for effective antibiotics against this pathogen has been almost entirely depleted. This study aims to evaluate the antibacterial effect of gold nanostars (GNS) alone or associated with some of the most widely used antibiotics for the treatment of CR-KP strains, i.e., meropenem or amikacin, on both planktonic and sessile forms. Additionally, we measured the effect of GNS on cell proliferation and biocompatibility in invertebrate in vivo models. (2) Materials and methods: GNS were made from gold seeds grown using a seeded-growth surfactant-free method assisted by silver ions and functionalized with mercapto-poly(ethylene glycol)amino by ligand exchange. The antimicrobial capacity, effect on cell proliferation, and biocompatibility of the most effective combination was evaluated in a Galleria mellonella model. (3) Results: The minimum inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) were 80 and 160 µM of GNS for all strains, respectively. The minimum biofilm inhibitory concentration (MBIC) and minimum biofilm eradication concentration (MBEC) were >320 µM of GNS for both. A synergy was found between GNS and amikacin. Larvae administered GNS plus amikacin were found to tolerate the treatment well, which prevented infection. (4) Conclusions: GNS are a promising anti-CR-KP nanomaterial.

RNA interference (RNAi)-based plasmonic nanomaterials for cancer diagnosis and therapy

RNA interference (RNAi) is being extensively investigated as a potential therapeutic strategy for cancer treatment. However, RNAi-based therapeutics have not yet been used to treat cancer because of their instability and the difficulty of microRNA (miRNA) delivery. Plasmonic nanoparticle-based RNAi nanotherapeutics have been developed for accurate and sensitive diagnosis and a strong therapeutic effect on cancers by leveraging their ease-of-use and specific properties such as photothermal conversion. In this review, recent strategies and advances in plasmonic nanoparticle-based miRNA delivery are briefly presented to facilitate the detection and treatment of several cancers. The challenges and potential opportunities afforded by the RNAi-based theragnosis field are discussed. We expect that the RNAi-integrated plasmonic nanotherapeutics discussed in this review can provide insights for the early diagnosis and effective treatment of cancer.

Exosomes: Powerful weapon for cancer nano-immunoengineering

Cancer immunotherapy (CIT) that targets the tumor immune microenvironment is regarded as a revolutionary advancement in the fight against cancer. The success and failure of CIT are due to the complexity of the immunosuppressive microenvironment. Cancer nanomedicine is a potential adjuvant therapeutic strategy for immune-based combination therapy. Exosomes are natural nanomaterials that play a pivotal role in mediating intercellular communications and package delivery in the tumor microenvironment. They affect the immune response or the effectiveness of immunotherapy. In particular, exosomal PD-L1 promotes cancer progression and resistance to immunotherapy. Exosomes possess high bioavailability, biological stability, targeting specificity, low toxicity, and immune characteristics, which indicate their potential for cancer therapy. They can be engineered to act as effective cancer therapeutic tools that activate anti-tumor immune response and start immune surveillance. In the current review, we introduce the role of exosomes in a tumor immune microenvironment, highlight the application of engineered exosomes to CIT, and discuss the challenges and prospects for clinical application.

Gold Nanoparticles: Can They Be the Next Magic Bullet for Multidrug-Resistant Bacteria?

In 2017 the World Health Organization (WHO) announced a list of the 12 multidrug-resistant (MDR) families of bacteria that pose the greatest threat to human health, and recommended that new measures should be taken to promote the development of new therapies against these superbugs. Few antibiotics have been developed in the last two decades. Part of this slow progression can be attributed to the surge in the resistance acquired by bacteria, which is holding back pharma companies from taking the risk to invest in new antibiotic entities. With limited antibiotic options and an escalating bacterial resistance there is an urgent need to explore alternative ways of meeting this global challenge. The field of medical nanotechnology has emerged as an innovative and a powerful tool for treating some of the most complicated health conditions. Different inorganic nanomaterials including gold, silver, and others have showed potential antibacterial efficacies. Interestingly, gold nanoparticles (AuNPs) have gained specific attention, due to their biocompatibility, ease of surface functionalization, and their optical properties. In this review, we will focus on the latest research, done in the field of antibacterial gold nanoparticles; by discussing the mechanisms of action, antibacterial efficacies, and future implementations of these innovative antibacterial systems.

External and Internal Stimuli-Responsive Metallic Nanotherapeutics for Enhanced Anticancer Therapy

Therapeutic, diagnostic, and imaging approaches based on nanotechnology offer distinct advantages in cancer treatment. Various nanotherapeutics have been presented as potential alternatives to traditional anticancer therapies such as chemotherapy, radiotherapy, and surgical intervention. Notably, the advantage of nanotherapeutics is mainly attributable to their accumulation and targeting ability toward cancer cells, multiple drug-carrying abilities, combined therapies, and imaging approaches. To date, numerous nanoparticle formulations have been developed for anticancer therapy and among them, metallic nanotherapeutics reportedly demonstrate promising cancer therapeutic and diagnostic efficiencies owing to their dense surface functionalization ability, uniform size distribution, and shape-dependent optical responses, easy and cost-effective synthesis procedure, and multiple anti-cancer effects. Metallic nanotherapeutics can remodel the tumor microenvironment by changing unfavorable therapeutic conditions into therapeutically accessible ones with the help of different stimuli, including light, heat, ultrasound, an alternative magnetic field, redox, and reactive oxygen species. The combination of metallic nanotherapeutics with both external and internal stimuli can be used to trigger the on-demand release of therapeutic molecules, augmenting the therapeutic efficacies of anticancer therapies such as photothermal therapy, photodynamic therapy, magnetic hyperthermia, sonodynamic therapy, chemodynamic therapy, and immunotherapy. In this review, we have summarized the role of different metallic nanotherapeutics in anti-cancer therapy, as well as their combinational effects with multiple stimuli for enhanced anticancer therapy.

Photothermal conversion of SiO2@Au nanoparticles mediated by surface morphology of gold cluster layer

Photothermal effects in SiO2@Au core-shell nanoparticles have demonstrated great potential in various applications for drug delivery, thermo-photovoltaics and photothermal cancer therapy, etc. However, the photothermal conversion of SiO2@Au nanoparticles partially covered by disconnected gold clusters has rarely been investigated systematically. Here, we control the surface morphology of gold clusters on the photothermal conversion performance of SiO2@Au core-shell nanoparticles by means of chemically adjusting the synthesis parameters, including amounts of gold salts, pH value and reducing agent. The macroscopic variations of the photothermal heating of different nanoparticle dispersions are significantly influenced by the nanoscale differences of gold cluster morphologies on the silica core. The temperature rise can be enhanced by the strong near-field coupling and collective heating among gold clusters with a relatively uniform distribution on the silica core. A numerical model of the simplified photothermal system is formulated to interpret the physical mechanism of the experimental observation, and shows a similar trend of temperature rise implying a reasonably good agreement with experimental data. Our work opens new possibilities for manipulating the light-to-heat conversion performance of SiO2@Au core-shell nanoparticles and potential applications of heat delivery with spatial resolution on the nanoscale.

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.

Photothermally active nanoparticles as a promising tool for eliminating bacteria and biofilms

Bacterial contamination is a severe issue that affects medical devices, hospital tools and surfaces. When microorganisms adhere to a surface (e.g., medical devices or implants) they can develop into a biofilm, thereby becoming more resistant to conventional biocides and disinfectants. Nanoparticles can be used as an antibacterial agent in medical instruments or as a protective coating in implantable devices. In particular, attention is being drawn to photothermally active nanoparticles that are capable of converting absorbed light into heat. These nanoparticles can efficiently eradicate bacteria and biofilms upon light activation (predominantly near the infrared to near-infrared spectral region) due a rapid and pronounced local temperature increase. By using this approach new, protective, antibacterial surfaces and materials can be developed that can be remotely activated on demand. In this review, we summarize the state-of-the art regarding the application of various photothermally active nanoparticles and their corresponding nanocomposites for the light-triggered eradication of bacteria and biofilms.