Multifunctional gold-based nanocomposites for theranostics

Silencing of proinflammatory NF-κB and inhibition of herpes simplex virus (HSV) replication by ultrasmall gold nanoparticles (2 nm) conjugated with small-interfering RNA

Azide-terminated ultrasmall gold nanoparticles (2 nm gold core) were covalently functionalized with alkyne-terminated small-interfering siRNA duplexes by copper-catalyzed azide-alkyne cycloaddition (CuAAC; click chemistry). The nanoparticle core was visualized by transmission electron microscopy. The number of attached siRNA molecules per nanoparticle was determined by a combination of atomic absorption spectroscopy (AAS; for gold) and UV-Vis spectroscopy (for siRNA). Each nanoparticle carried between 6 and 10 siRNA duplex molecules which corresponds to a weight ratio of siRNA to gold of about 2.2 : 1. Different kinds of siRNA were conjugated to the nanoparticles, depending on the gene to be silenced. In general, the nanoparticles were readily taken up by cells and highly efficient in gene silencing, in contrast to free siRNA. This was demonstrated in HeLa-eGFP cells (silencing of eGFP) and in LPS-stimulated macrophages (silencing of NF-κB). Furthermore, we demonstrated that nanoparticles carrying antiviral siRNA potently inhibited the replication of Herpes simplex virus 2 (HSV-2) in vitro. This highlights the strong potential of siRNA-functionalized ultrasmall gold nanoparticles in a broad spectrum of applications, including gene silencing and treatment of viral infections, combined with a minimal dose of gold.

Multifunctional Gold Helix Phototheranostic Biohybrid That Enables Targeted Image-Guided Photothermal Therapy in Breast Cancer

The preparation of multifunctional smart theranostic systems is commonly achieved through complicated strategies, limiting their biomedical applications. Spirulina platensis (SP) microalgae, as a natural helix with some of the intrinsic theranostic functionalities (e.g., fluorescent and photosensitizer pigments), not only facilitates the fabrication process but also guarantees their biosafety for clinical applications. Herein, the helical architecture of gold nanoparticles (AuNPs) based on a SP biotemplate was engineered as a safe, biodegradable, and tumor-targeted biohybrid for imaging-guided photothermal therapy (PTT) to combat triple-negative breast cancer. The quasi-spherical AuNPs were embedded throughout the SP cell (Au-SP) with minimally involved reagents, only by controlling the original morphological stability of SP through pH adjustment of the synthesis media. SP thiolation increased the localization of AuNPs selectively on the cell wall without using a reducing agent (Au-TSP). SP autofluorescence, along with the high X-ray absorption of AuNPs, was employed for dual-modal fluorescence and computed tomography (FL/CT) imaging. Furthermore, the theranostic efficacy of Au-SP was improved through a targeting process with folic acid (Au-SP@CF). High tumor inhibition effects were obtained by the excellent photothermal performance of Au-SP@CF in both in vitro and in vivo analyses. Of particular note, a comparison of the photothermal effect of Au-SP@CF with the naked SP and calcined form of Au-SP@CF not only indicated the key role of the helical architecture of AuNPs in achieving a high photothermal effect but also led to the formation of new gold microspiral biohybrids (Au-MS) over the calcination process. In short, well-controllable immobilization of AuNPs, appropriate biodegradability, good hemocompatibility, long-term biosafety, accurate imaging, high tumor suppression, and low tumor metastasis effects under laser irradiation are an array of intriguing attributes, making the proposed biohybrid a promising theranostic system for FL/CT-imaging-guided PTT.

Photoactivatable carbon dots as a label-free fluorescent probe for picric acid detection and light-induced bacterial inactivation

The zero-dimensional carbon nanostructure known as carbon dots showed attractive attributes such as multicolour emission, very high quantum yield, up-conversion, very good aqueous solubility, eco-friendliness, and excellent biocompatibility. These outstanding features of the carbon dots have raised significant interest among the research community worldwide. In the current work, water-soluble nitrogen, silver, and gold co-doped bimetallic carbon dots (BCDs) were prepared using the one-pot hydrothermal method with citric acid as a sole carbon source. As prepared BCDs showed size in the range of 4-8 nm and excitation-independent emission behaviour with maximum emission observed at 427 nm. Additionally, these BCDs showed a very high quantum yield value of 50% and fluorescence lifetime value of 10.1 ns respectively. Interestingly, as prepared BCDs selectively sense picric acid (PA) by exhibiting "selective fluorescence turn-off" behaviour in the presence of PA with a limit of detection value (LOD) of 46 nM. Further, as prepared BCDs were explored for photodynamic therapy to inactivate bacterial growth in the presence of light (400-700 nm) by generating singlet oxygen. Thus as prepared BCDs offer lots of potentials to use a nanoprobe to detect picric acid in an aqueous medium and to design next-generation antibacterial materials.

Dual-molecular targeted NIR II probe with enhanced response for head and neck squamous cell carcinoma imaging

In this research, a fluorescent probe of 7-(diethylamine) coumarin derivatives with multiple binding sites to detect biothiols in tumor cell with strong NIR II luminescencein vivowas synthesized. The biothiols include cysteine (Cys) and glutathione (GSH) in tumor cells, and the tumor-response luminescence was proved by the cell experiment. Importantly, the monolayer functional phospholipid (DSPE-PEG) coating and aggregation induced emission (AIE) dye of TPE modification made the probe have good stability and biocompatibility with little luminescence quenching in aqueous phase, which was proved byin vitroandin vivoexperiments. The final aqueous NIR II probe combined with bevacizumab (for VEGF recognition in the cancer cells) and Capmatinib (for Met protein recognition in the cancer cells) has stronger targeted imaging on head and neck squamous cell carcinoma (HNSCC) cancer with intravenous injection. This GSH/Cys detection in the tumor cell and strong dual-molecular NIR II bioimagingin vivomay provide new strategy to tumor detection.

Photothermal and Photodynamic Therapy of Tumors with Plasmonic Nanoparticles: Challenges and Prospects

Cancer remains one of the leading causes of death in the world. For a number of neoplasms, the efficiency of conventional chemo- and radiation therapies is insufficient because of drug resistance and marked toxicity. Plasmonic photothermal therapy (PPT) using local hyperthermia induced by gold nanoparticles (AuNPs) has recently been extensively explored in tumor treatment. However, despite attractive promises, the current PPT status is limited by laboratory experiments, academic papers, and only a few preclinical studies. Unfortunately, most nanoformulations still share a similar fate: great laboratory promises and fair preclinical trials. This review discusses the current challenges and prospects of plasmonic nanomedicine based on PPT and photodynamic therapy (PDT). We start with consideration of the fundamental principles underlying plasmonic properties of AuNPs to tune their plasmon resonance for the desired NIR-I, NIR-2, and SWIR optical windows. The basic principles for simulation of optical cross-sections and plasmonic heating under CW and pulsed irradiation are discussed. Then, we consider the state-of-the-art methods for wet chemical synthesis of the most popular PPPT AuNPs such as silica/gold nanoshells, Au nanostars, nanorods, and nanocages. The photothermal efficiencies of these nanoparticles are compared, and their applications to current nanomedicine are shortly discussed. In a separate section, we discuss the fabrication of gold and other nanoparticles by the pulsed laser ablation in liquid method. The second part of the review is devoted to our recent experimental results on laser-activated interaction of AuNPs with tumor and healthy tissues and current achievements of other research groups in this application area. The unresolved issues of PPT are the significant accumulation of AuNPs in the organs of the mononuclear phagocyte system, causing potential toxic effects of nanoparticles, and the possibility of tumor recurrence due to the presence of survived tumor cells. The prospective ways of solving these problems are discussed, including developing combined antitumor therapy based on combined PPT and PDT. In the conclusion section, we summarize the most urgent needs of current PPT-based nanomedicine.

Fabricating Dual-Functional Plasmonic-Magnetic Au@MgFe2O4 Nanohybrids for Photothermal Therapy and Magnetic Resonance Imaging

Bifunctional nanohybrids possessing both plasmonic and magnetic functionalities are of great interest for biomedical applications owing to their capability for simultaneous therapy and diagnostics. Herein, we fabricate a core-shell structured plasmonic-magnetic nanocomposite system that can serve as a dual-functional agent due to its combined photothermal therapeutic and magnetic resonance imaging (MRI) functions. The photothermal activity of the hybrid is attributed to its plasmonic Au core, which is capable of absorbing near-infrared (NIR) light and converting it into heat. Meanwhile, the magnetic MgFe₂O₄ shell exerts its ability to act as a MRI contrast agent. Our in vivo studies using tumor-bearing mice demonstrated the nanohybrids' excellent photothermal and MRI properties. As a photothermal therapeutic agent, the nanohybrids were able to dramatically shrink solid tumors in mice through NIR-induced hyperthermia. As T ₂-weighted MRI contrast agents, the nanohybrids were found capable of substantially reducing the MRI signal intensity of the tumor region at 10 min postinjection. With their dual plasmonic-magnetic functionality, these Au@MgFe₂O₄ nanohybrids hold great promise not only in the biomedical field but also in the areas of catalysis and optical sensing.

Advances in FePt-involved nano-system design and application for bioeffect and biosafety

The rapid development and wide application of nanomaterial-involved theranostic agents have drawn surging attention for improving the living standard of humankind and healthcare conditions. In this review, recent developments in the design, synthesis, biocompatibility evaluation and potential nanomedicine applications of FePt-involved nano-systems are summarized, especially for cancer theranostic and biological molecule detection. The in vivo multi-model imaging capability is discussed in detail, including magnetic resonance imaging and computed tomography. Furthermore, we highlight the significant achievements of various FePt-involved nanotherapeutics for cancer treatment, such as drug delivery, chemodynamic therapy, photodynamic therapy, radiotherapy and immunotherapy. In addition, a series of FePt-involved nanocomposites are also applied for biological molecule detection, such as H₂O₂, glucose and naked-eye detection of cancer cells. Ultimately, we also summarize the challenges and prospects of FePt-involved nano-systems in nanocatalytic medicine. This review is expected to give a general pattern for the development of FePt-involved nano-systems in the field of nanocatalytic medicine and analytical determination.

Antibodies as Biosensors' Key Components: State-of-the-Art in Russia 2020-2021

The recognition of biomolecules is crucial in key areas such as the timely diagnosis of somatic and infectious diseases, food quality control, and environmental monitoring. This determines the need to develop highly sensitive display devices based on the achievements of modern science and technology, characterized by high selectivity, high speed, low cost, availability, and small size. Such requirements are met by biosensor systems—devices for reagent-free analysis of compounds that consist of a biologically sensitive element (receptor), a transducer, and a working solution. The diversity of biological material and methods for its immobilization on the surface or in the volume of the transducer and the use of nanotechnologies have led to the appearance of an avalanche-like number of different biosensors, which, depending on the type of biologically sensitive element, can be divided into three groups: enzyme, affinity, and cellular/tissue. Affinity biosensors are one of the rapidly developing areas in immunoassay, where the key point is to register the formation of an antigen–antibody complex. This review analyzes the latest work by Russian researchers concerning the production of molecules used in various immunoassay formats as well as new fundamental scientific data obtained as a result of their use.

Gold nanotheranostics: future emblem of cancer nanomedicine

Cancer nanotheranostics aims at providing alternative approaches to traditional cancer diagnostics and therapies. In this context, plasmonic nanostructures especially gold nanostructures are intensely explored due to their tunable shape, size and surface plasmon resonance (SPR), better photothermal therapy (PTT) and photodynamic therapy (PDT) ability, effective contrast enhancing ability in Magnetic Resonance imaging (MRI) and Computed Tomography (CT) scan. Despite rapid breakthroughs in gold nanostructures based theranostics of cancer, the translation of gold nanostructures from bench side to human applications is still questionable. The major obstacles that have been facing by nanotheranostics are specific targeting, poor resolution and photoinstability during PTT etc. In this regard, various encouraging studies have been carried out recently to overcome few of these obstacles. Use of gold nanocomposites also overcomes the limitations of gold nanostructure probes and emerged as good nanotheranostic probe. Hence, the present article discusses the advances in gold nanostructures based cancer theranostics and mainly emphasizes on the importance of gold nanocomposites which have been designed to decipher the past questions and limitations of in vivo gold nanotheranostics.

Synthesis and characterization of gold nanorods coated by mesoporous silica MCM-41 as a platform bioapplication in photohyperthermia

Gold nanoparticles have been widely investigated for biomedical applications due to their optical properties. These particles present the interesting feature of absorbing light when stimulated with laser radiation to generate heating. Among the possible morphologies for synthetic gold nanoparticles, gold nanorods have properties of great interest for applications in the photohyperthermia processes. Due to their morphology, gold nanorods can absorb light at longer wavelengths comprising specific regions of the electromagnetic spectrum, such as the region of the biological window, in which laser radiation has less interaction with tissues. However, these nanoparticles present limitations in biomedical applications, such as low colloidal and thermal stabilities that can be overcome by coating the gold nanorods with silica MCM-41. The silicate covering can provide greater stability for gold nanorods and allow multifunctionality in treating different diseases through photohyperthermia. This work developed a specific chemical route through seed and growth solutions to synthesize gold nanorods with controlled particle size, rod morphology, and silica covering for photohyperthermia applications. The synthesized samples were characterized through a multi-technique approach that successfully demonstrated the presence of gold nanorods inside the silica coating, presenting high stability and desirable textural and morphological characteristics for bioapplications. Furthermore, silica-coated gold nanorods exhibit high biocompatibility and great performance in generating therapeutic heating by absorbing laser radiation in the biological window range, making the system developed in this work a promising agent in photohyperthermia.

Current Biomedical and Diagnostic Applications of Gold Micro and Nanoparticles

Production of particles and their adaptation in the pharmacology became an object of interest, and they are the currently introduced therapies based on the use of micro and nanoparticles. The use of gold particles is not an exception. This review has focused on the application of gold micro and nanoparticles in pharmacology and biomedicine. The particles can be used for diagnosis respective theranostic of cancer, rheumatoid arthritis and as antimicrobial means. Besides these applications, specifications of gold, gold particles, and colloidal gold manufacturing and their comparison with the solid gold, are described as well. This review is based on a survey of actual scientific literature.

Bioresponsive nanomedicines based on dynamic covalent bonds

Trends in the development of modern medicine necessitate the efficient delivery of therapeutics to achieve the desired treatment outcomes through precise spatiotemporal accumulation of therapeutics at the disease site. Bioresponsive nanomedicine is a promising platform for this purpose. Dynamic covalent bonds (DCBs) have attracted much attention in studies of the fabrication of bioresponsive nanomedicines with an abundance of combinations of therapeutic modules and carrier function units. DCB-based nanomedicines could be designed to maintain biological friendly synthesis and site-specific release for optimal therapeutic effects, allowing the complex to retain an integrated structure before accumulating at the disease site, but disassembling into individual active components without compromising function in the targeted organs or tissues. In this review, we focus on responsive nanomedicines containing dynamic chemical bonds that can be cleaved by various specific stimuli, enabling achievement of targeted drug release for optimal therapy in various diseases.

The Peptide Functionalized Inorganic Nanoparticles for Cancer-Related Bioanalytical and Biomedical Applications

In order to improve their bioapplications, inorganic nanoparticles (NPs) are usually functionalized with specific biomolecules. Peptides with short amino acid sequences have attracted great attention in the NP functionalization since they are easy to be synthesized on a large scale by the automatic synthesizer and can integrate various functionalities including specific biorecognition and therapeutic function into one sequence. Conjugation of peptides with NPs can generate novel theranostic/drug delivery nanosystems with active tumor targeting ability and efficient nanosensing platforms for sensitive detection of various analytes, such as heavy metallic ions and biomarkers. Massive studies demonstrate that applications of the peptide-NP bioconjugates can help to achieve the precise diagnosis and therapy of diseases. In particular, the peptide-NP bioconjugates show tremendous potential for development of effective anti-tumor nanomedicines. This review provides an overview of the effects of properties of peptide functionalized NPs on precise diagnostics and therapy of cancers through summarizing the recent publications on the applications of peptide-NP bioconjugates for biomarkers (antigens and enzymes) and carcinogens (e.g., heavy metallic ions) detection, drug delivery, and imaging-guided therapy. The current challenges and future prospects of the subject are also discussed.

Hyaluronic acid functionalized gold nanorods combined with copper-based therapeutic agents for chemo-photothermal cancer therapy

We herein report a hybrid nanocomposite (AuNRs-CTN@THA) which is based on hyaluronic acid-coated gold nanorods with loading of a copper complex through strong bonds. AuNRs-CTN@THA exhibits durable photothermal conversion capacity for pH-dominant and pH/temperature dual sensitive drug release, accomplishing synergetic antitumor efficacy and deep tumor penetration.

Photostability of Contrast Agents for Photoacoustics: The Case of Gold Nanorods

Plasmonic particles as gold nanorods have emerged as powerful contrast agents for critical applications as the photoacoustic imaging and photothermal ablation of cancer. However, their unique efficiency of photothermal conversion may turn into a practical disadvantage, and expose them to the risk of overheating and irreversible photodamage. Here, we outline the main ideas behind the technology of photoacoustic imaging and the use of relevant contrast agents, with a main focus on gold nanorods. We delve into the processes of premelting and reshaping of gold nanorods under illumination with optical pulses of a typical duration in the order of few ns, and we present different approaches to mitigate this issue. We undertake a retrospective classification of such approaches according to their underlying, often implicit, principles as: constraining the initial shape; or speeding up their thermal coupling to the environment by lowering their interfacial thermal resistance; or redistributing the input energy among more particles. We discuss advantages, disadvantages and contexts of practical interest where one solution may be more appropriate than the other.

Uptake quantification of gold nanoparticles inside of cancer cells using high order image correlation spectroscopy

The application of gold nanoparticles (AuNPs) in cancer therapeutics and diagnostics has recently reached a clinical level. Functional use of the AuNP in theranostics first requires effective uptake into the cells, but accurate quantification of AuNPs cellular uptake in real-time is still a challenge due to the destructive nature of existing characterization methods. The optical imaging-based quantification method is highly desirable. Here, we propose the use of high-order image correlation spectroscopy (HICS) as an optical imaging-based nanoparticle quantification technique. Coupled with dark field microscopy (DFM), a non-destructive and easy quantification method could be achieved. We demonstrate HICS analysis on 80 nm AuNPs coated with cetyltrimethylammonium bromide (CTAB) uptake in HeLa cells to calculate the percentage of aggregate species (dimer) in the total uptake and their relative scattering quantum yield inside the cells, the details of which are not available with other quantification techniques. The total particle uptake kinetics measured were in a reasonable agreement with the literature.

Ce6-Conjugated and polydopamine-coated gold nanostars with enhanced photoacoustic imaging and photothermal/photodynamic therapy to inhibit lung metastasis of breast cancer

Metastasis is the main cause of treatment failure in breast cancer, and integrated phototheranostics is a promising strategy to achieve both precision theranostics and metastasis inhibition. In this work, a multifunctional phototheranostic nanoprobe composed of chlorin e6 (Ce6)-conjugated and polydopamine (PDA)-coated gold nanostars (AuNSs) was synthesized for simultaneous photoacoustic (PA) imaging, photothermal therapy (PTT) and photodynamic therapy (PDT). Under the irradiation of near infrared laser, AuNSs@PDA showed enhanced photothermal conversion and amplified PA imaging performance, compared with single AuNSs. By the covalent conjugation of Ce6, the AuNSs@PDA-Ce6 nanoprobe showed robust stability and excellent singlet oxygen (1O2) generation ability. Under the combination of PTT/PDT, the AuNSs@PDA-Ce6 nanoprobes significantly reduced the growth of 4T1 tumors and suppressed their lung metastasis. All the results demonstrated the considerable potential of AuNSs@PDA-Ce6 phototheranostic nanoprobes for precision theranostics and metastasis inhibition of breast cancer.

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.

A pH-sensitive fluorescent protein sensor to follow the pathway of calcium phosphate nanoparticles into cells

Calcium phosphate nanoparticles (100 nm) were fluorescently labelled with poly(ethyleneimine) (PEI_ATTO490LS; red fluorescence). They were loaded with a Tandem fusion protein consisting of mRFP1-eGFP (red and green fluorescence in the same molecule)that acts as smart biological pH sensor to trace nanoparticles inside cells. Its fluorescence is also coupled to the structural integrity of the protein, i.e. it is also a label for a successful delivery of a functional protein into the cell. At pH 7.4, the fluorescence of both proteins (red and green) is detectable. At a pH of 4.5-5 inside the lysosomes, the green fluorescence is quenched due to the protonation of the eGFP chromophore, but the pH-independent red fluorescence of mRFP1 remains. The nanoparticles were taken up by cells (cell lines: HeLa, Caco-2 and A549) via endocytic pathways and then directed to lysosomes. Time-resolved confocal laser scanning microscopy confirmed mRFP1 and nanoparticles co-localizing with lysosomes. The fluorescence of eGFP was only detectable outside lysosomes, i.e. most likely inside early endosomes or at the cell membrane during the uptake, indicating the neutral pH at these locations. The Tandem fusion protein provides a versatile platform to follow the intracellular pathway of bioactive nanocarriers, e.g. therapeutic proteins. The transfection with a Tandem-encoding plasmid by calcium phosphate nanoparticles led to an even intracellular protein distribution in cytosol and nucleoplasm, i.e. very different from direct protein uptake. Neither dissolved protein nor dissolved plasmid DNA were taken up by the cells, underscoring the necessity for a suitable carrier like a nanoparticle. STATEMENT OF SIGNIFICANCE: A pH-sensitive protein ("tandem") was used to follow the pathway of calcium phosphate nanoparticles. This protein consists of a pH-sensitive fluorophore (eGFP; green) and a pH-independent fluorophore (mRFP1; red). This permits to follow the pathway of a nanoparticle inside a cell. At a low pH inside an endolysosome, the green fluorescence vanishes but the red fluorescence persists. This is also a very useful model for the delivery of therapeutic proteins into cells. The delivery by nanoparticles was compared with the protein expression after cell transfection with plasmid DNA encoding for the tandem protein. High-resolution image analysis gave quantitative data on the intracellular protein distribution.

Ultrasmall gold nanoparticles (2 nm) can penetrate and enter cell nuclei in an in vitro 3D brain spheroid model

The neurovascular unit (NVU) is a complex functional and anatomical structure composed of endothelial cells and their blood-brain barrier (BBB) forming tight junctions. It represents an efficient barrier for molecules and drugs. However, it also prevents a targeted transport for the treatment of cerebral diseases. The uptake of ultrasmall nanoparticles as potential drug delivery agents was studied in a three-dimensional co-culture cell model (3D spheroid) composed of primary human cells (astrocytes, pericytes, endothelial cells). Multicellular 3D spheroids show reproducible NVU features and functions. The spheroid core is composed mainly of astrocytes, covered with pericytes, while brain endothelial cells form the surface layer, establishing the NVU that regulates the transport of molecules. After 120 h cultivation, the cells self-assemble into a 350 µm spheroid as shown by confocal laser scanning microscopy. The passage of different types of fluorescent ultrasmall gold nanoparticles (core diameter 2 nm) both into the spheroid and into three constituting cell types was studied by confocal laser scanning microscopy. Three kinds of covalently fluorophore-conjugated gold nanoparticles were used: One with fluorescein (FAM), one with Cy3, and one with the peptide CGGpTPAAK-5,6-FAM-NH₂. In 2D cell co-culture experiments, it was found that all three kinds of nanoparticles readily entered all three cell types. FAM- and Cy3-labelled nanoparticles were able to enter the cell nucleus as well. The three dissolved dyes alone were not taken up by any cell type. A similar situation evolved with 3D spheroids: The three kinds of nanoparticles entered the spheroid, but the dissolved dyes did not. The presence of a functional blood-brain barrier was demonstrated by adding histamine to the spheroids. In that case, the blood-brain barrier opened, and dissolved dyes like a FITC-labelled antibody and FITC alone entered the spheroid. In summary, our results qualify ultrasmall gold nanoparticles as suitable carriers for imaging or drug delivery into brain cells (sometimes including the nucleus), brain cell spheroids, and probably also into the brain. STATEMENT OF SIGNIFICANCE: 3D brain spheroid model and its permeability by ultrasmall gold nanoparticles. We demonstrate that ultrasmall gold nanoparticles can easily penetrate the constituting cells and sometimes even enter the cell nucleus. They can also enter the interior of the blood-brain barrier model. In contrast, small molecules like fluorescing dyes are not able to do that. Thus, ultrasmall gold nanoparticles can serve as carriers of drugs or for imaging inside the brain.

Charge-conversional polyethylenimine-entrapped gold nanoparticles with 131I-labeling for enhanced dual mode SPECT/CT imaging and radiotherapy of tumors

Novel theranostic nanosystems demonstrate great potential to achieve timely diagnosis and effective therapy at the same time. However, due to the relatively low accumulation of theranostic nanosystems at the tumor site, the theranostic efficiency is limited. In this study, a novel theranostic nanosystem with a pH-responsive charge conversion property was constructed to improve the cellular uptake towards cancer cells for enhanced single photon emission computed tomography (SPECT)/computed tomography (CT) dual mode imaging and radiotherapy of tumors. In detail, polyethylenimine (PEI) was utilized as a nanoplatform to link with polyethylene glycol (PEG) monomethyl ether with one end of N-hydroxylsuccinimide (mPEG-NHS), PEG with ends of maleimide and succinimidyl valerate (MAL-PEG-SVA), alkoxyphenyl acylsulfonamide (APAS), 3-(4'-hydroxyphenyl)propionic acid-OSu (HPAO), and fluorescein isothiocyanate (FI), successively. The formed functionalized PEI was then utilized to entrap gold nanoparticles, acetylate the remaining amines of PEI and label with radioactive iodine-131 (¹³¹I) to build theranostic nanosystems. The result demonstrated that the theranostic nanosystem has a 3.8 nm Au core and showed excellent colloidal stability. On account of the charge conversion property of APAS, the APAS linked PEI entrapped gold nanoparticles could switch from neutral to positive in a slightly acidic microenvironment, which induced improved cellular uptake. Above all, after ¹³¹I labeling, the generated theranostic nanosystem could achieve enhanced SPECT/CT dual mode imaging and radiotherapy of cancer cells in vitro and a xenograft tumor model in vivo. The constructed APAS-linked PEI nanosystem has great potential to be used as a model for SPECT/CT imaging and radiotherapy of various types of cancer.

Ampicillin-mediated functionalized gold nanoparticles against ampicillin-resistant bacteria: strategy, preparation and interaction studies

Antibiotic resistance is a highly challenging concern of infectious diseases, and it requires a rational approach to overcome. Through this work, we have synthesized ampicillin-capped gold nanoparticles (Amp-Au NPs) and studied its interaction with bacterial cells. In this process of synthesis, the primary amine group of ampicillin acts as both reducing as well as capping agent. In addition to synthesized gold nanoparticles, the β-lactam ring remains free to interact with bacteria. This approach not only utilizes the maximum efficiency of nanoparticles and antibiotics towards ampicillin sensitive bacterial cells but also proves to be effective against ampicillin resistance bacteria. Our results illustrate that the optimized system of Amp-Au NPs was formulated by taking 1.25 mM ampicillin and 10^-2 of gold ions concentration. UV-vis spectrum of gold nanoparticles and the presence of ampicillin were recorded at around 540 nm and 259 nm, respectively. Microscopic images indicate that particles are nearly spherical and are in size range between 25 and 50 nm. Moreover, formulated Amp-Au NPs show successful accumulation onto the surface of the bacterial cell as a result of which pores were formed into the bacterial membrane. The entry of nanoparticles into bacterial cells was validated through both atomic force microscopy and fluorescent microscopy. The adhesive properties of this coating material and its stability in various pH, i.e. pH 3, pH 7 and pH 10 conditions, could make them a good candidate in the prevention of biofilm formation. Amp-Au NPs show promising antimicrobial activity against ampicillin resistance Escherichia coli bacteria. Furthermore, antimicrobial studies indicate that the efficacy of Amp-Au NPs increased against both ampicillin sensitive and ampicillin resistance bacteria up to sixteen folds and four folds respectively.

Duo of (-)-epigallocatechin-3-gallate and doxorubicin loaded by polydopamine coating ZIF-8 in the regulation of autophagy for chemo-photothermal synergistic therapy

To achieve highly systemic therapeutic efficacy, chemotherapy is combined with photothermal therapy for chemo-photothermal synergistic therapy; however, this strategy suffers from high toxicity and unsatisfactory sensitivity for cancer cells. Herein, we developed a pH- and photothermal-responsive zeolitic imidazolate framework (ZIF-8) compound for loading a dual-drug in the tumor site and improving their curative effects. Since autophagy always accompanies tumor progression and metastasis, there is an unmet need for an anticancer treatment related to the regulation of autophagy. Green tea polyphenols, namely, (-)-epigallocatechin-3-gallate (EGCG) and doxorubicin (DOX), both of which exhibit anticancer activity, were dual-loaded via polydopamine (PDA) coating ZIF-8 (EGCG@ZIF-PDA-PEG-DOX, EZPPD for short) through hierarchical self-assembly. PDA could transfer photothermal energy to increase the temperature under near-infrared (NIR) laser irradiation. Due to its pH-response, EZPPD released EGCG and DOX in the tumor microenvironment, wherein the temperature increased with the help of PDA and NIR laser irradiation. The duo of DOX and EGCG induced autophagic flux and accelerated the formation of autophagosomes. In a mouse HeLa tumor model, photothermal-chemotherapy could ablate the tumor with a significant synergistic effect and potentiate the anticancer efficacy. Thus, the results indicate that EZPPD renders the key traits of a clinically promising candidate to address the challenges associated with synergistic chemotherapy and photothermal utilization in antitumor therapy.

Multifunctional phototheranostic nanomedicine for cancer imaging and treatment

Cancer, as one of the most life-threatening diseases, shows a high fatality rate around the world. When improving the therapeutic efficacy of conventional cancer treatments, researchers also conduct extensive studies into alternative therapeutic approaches, which are safe, valid, and economical. Phototherapies, including photodynamic therapy (PDT) and photothermal therapy (PTT), are tumor-ablative and function-reserving oncologic interventions, showing strong potential in clinical cancer treatment. During phototherapies, the non-toxic phototherapeutic agents can be activated upon light irradiation to induce cell death without causing much damage to normal tissues. Besides, with the rapid development of nanotechnology in the past decades, phototheranostic nanomedicine also has attracted tremendous interests aiming to continuously refine their performance. Herein, we reviewed the recent progress of phototheranostic nanomedicine for improved cancer therapy. After a brief introduction of the therapeutic principles and related phototherapeutic agents for PDT and PTT, the existing works on developing of phototheranostic nanomedicine by mainly focusing on their categories and applications, particularly on phototherapy-synergized cancer immunotherapy, are comprehensively reviewed. More importantly, a brief conclusion and future challenges of phototheranostic nanomedicine from our point of view are delivered in the last part of this article.

Multifunctional Magnetic Resonance Imaging Probes

Magnetic resonance imaging is characterized by high spatial resolution and unsurpassed soft tissue discrimination. Development and characterization of both intrinsic and extrinsic magnetic resonance (MR) imaging probes in the last decade has further strengthened the pivotal role MR imaging holds in the assessment of cancer in preclinical and translational settings. Sophisticated chemical modifications of a variety of nanoparticulate probes hold the potential to deliver valuable multifunctional tools applicable in diagnostics and/or treatment in human oncology. MR imaging suffers from a lack of sensitivity achievable by, e.g., nuclear medicine imaging methods. Advantages of including additional functionality/functionalities in a probe suitable for MR imaging are thus numerous, comprising the addition of fundamentally different imaging information (diagnostics), drug delivery (therapy), or the combination of both (theranostics). In recent years, we have witnessed a plethora of preclinical multimodal or multifunctional imaging probes being published mainly as proof-of-principle studies, yet only a handful are readily applicable in clinical settings. This chapter summarizes recent innovations in the development of multifunctional MR imaging probes and discusses the suitability of these probes for clinical transfer.

Gold nanoparticles in chemo-, immuno-, and combined therapy: review [Invited]

Functionalized gold nanoparticles (GNPs) with controlled geometrical and optical properties have been the subject of intense research and biomedical applications. This review summarizes recent data and topical problems in nanomedicine that are related to the use of variously sized, shaped, and structured GNPs. We focus on three topical fields in current nanomedicine: (1) use of GNP-based nanoplatforms for the targeted delivery of anticancer and antimicrobial drugs and of genes; (2) GNP-based cancer immunotherapy; and (3) combined chemo-, immuno-, and phototherapy. We present a summary of the available literature data and a short discussion of future work.

Recent Progress in the Development of Poly(lactic-co-glycolic acid)-Based Nanostructures for Cancer Imaging and Therapy

Diverse nanosystems for use in cancer imaging and therapy have been designed and their clinical applications have been assessed. Among a variety of materials available to fabricate nanosystems, poly(lactic-co-glycolic acid) (PLGA) has been widely used due to its biocompatibility and biodegradability. In order to provide tumor-targeting and diagnostic properties, PLGA or PLGA nanoparticles (NPs) can be modified with other functional materials. Hydrophobic or hydrophilic therapeutic cargos can be placed in the internal space or adsorbed onto the surface of PLGA NPs. Protocols for the fabrication of PLGA-based NPs for cancer imaging and therapy are already well established. Moreover, the biocompatibility and biodegradability of PLGA may elevate its feasibility for clinical application in injection formulations. Size-controlled NP’s properties and ligand–receptor interactions may provide passive and active tumor-targeting abilities, respectively, after intravenous administration. Additionally, the introduction of several imaging modalities to PLGA-based NPs can enable drug delivery guided by in vivo imaging. Versatile platform technology of PLGA-based NPs can be applied to the delivery of small chemicals, peptides, proteins, and nucleic acids for use in cancer therapy. This review describes recent findings and insights into the development of tumor-targeted PLGA-based NPs for use of cancer imaging and therapy.

Click Chemistry on the Surface of Ultrasmall Gold Nanoparticles (2 nm) for Covalent Ligand Attachment Followed by NMR Spectroscopy

Ultrasmall gold nanoparticles (core diameter 2 nm) were surface-conjugated with azide groups by attaching the azide-functionalized tripeptide lysine(N₃)-cysteine-asparagine with ∼117 molecules on each nanoparticle. A covalent surface modification with alkyne-containing molecules was then possible by copper-catalyzed click chemistry. The successful clicking to the nanoparticle surface was demonstrated with ¹³C-labeled propargyl alcohol. All steps of the nanoparticle surface conjugation were verified by extensive NMR spectroscopy on dispersed nanoparticles. The particle diameter and the dispersion state were assessed by high-resolution transmission electron microscopy (HRTEM), differential centrifugal sedimentation (DCS), and ¹H-DOSY NMR spectroscopy. The clicking of fluorescein (FAM-alkyne) gave strongly fluorescing ultrasmall nanoparticles that were traced inside eukaryotic cells. The uptake of these nanoparticles after 24 h by HeLa cells was very efficient and showed that the nanoparticles even penetrated the nuclear membrane to a very high degree (in contrast to dissolved FAM-alkyne alone that did not enter the cell). About 8 fluorescein molecules were clicked to each nanoparticle.

Solution NMR Spectroscopy with Isotope-Labeled Cysteine (13C and 15N) Reveals the Surface Structure of l-Cysteine-Coated Ultrasmall Gold Nanoparticles (1.8 nm)

Ultrasmall gold nanoparticles with a diameter of 1.8 nm were synthesized by reduction of tetrachloroauric acid with sodium borohydride in the presence of l-cysteine, with natural isotope abundance as well as ¹³C-labeled and ¹⁵N-labeled. The particle diameter was determined by high-resolution transmission electron microscopy and differential centrifugal sedimentation. X-ray photoelectron spectroscopy confirmed the presence of metallic gold with only a few percent of oxidized Au(+I) species. The surface structure and the coordination environment of the cysteine ligands on the ultrasmall gold nanoparticles were studied by a variety of homo- and heteronuclear NMR spectroscopic techniques including ¹H-¹³C-heteronuclear single-quantum coherence and ¹³C-¹³C-INADEQUATE. Further information on the binding situation (including the absence of residual or detached l-cysteine in the solution) and on the nanoparticle diameter (indicating the well-dispersed state) was obtained by diffusion-ordered spectroscopy (¹H-, ¹³C-, and ¹H-¹³C-DOSY). Three coordination environments of l-cysteine on the gold surface were identified that were ascribed to different crystallographic sites, supported by geometric considerations of the nanoparticle ultrastructure. The particle size data and the NMR-spectroscopic analysis gave a particle composition of about Au₁₇₄(cysteine)₆₇.

Current Trends in Cancer Nanotheranostics: Metallic, Polymeric, and Lipid-Based Systems

Theranostics has emerged in recent years to provide an efficient and safer alternative in cancer management. This review presents an updated description of nanotheranostic formulations under development for skin cancer (including melanoma), head and neck, thyroid, breast, gynecologic, prostate, and colon cancers, brain-related cancer, and hepatocellular carcinoma. With this focus, we appraised the clinical advantages and drawbacks of metallic, polymeric, and lipid-based nanosystems, such as low invasiveness, low toxicity to the surrounding healthy tissues, high precision, deeper tissue penetration, and dosage adjustment in a real-time setting. Particularly recognizing the increased complexity and multimodality in this area, multifunctional hybrid nanoparticles, comprising different nanomaterials and functionalized with targeting moieties and/or anticancer drugs, present the best characteristics for theranostics. Several examples, focusing on their design, composition, imaging and treatment modalities, and in vitro and in vivo characterization, are detailed herein. Briefly, all studies followed a common trend in the design of these theranostics modalities, such as the use of materials and/or drugs that share both inherent imaging (e.g., contrast agents) and therapeutic properties (e.g., heating or production reactive oxygen species). This rationale allows one to apparently overcome the heterogeneity, complexity, and harsh conditions of tumor microenvironments, leading to the development of successful targeted therapies.

A novel cell transfection platform based on laser optoporation mediated by Au nanostar layers

The recently developed laser-induced cell transfection mediated by Au nanoparticles is a promising alternative to the well-established lipid-based transfection or to electroporation. Optoporation is based on the laser plasmonic heating of nanoparticles located near the cell membrane. However, the uncontrollable cell damage from intense laser pulses and from random attachment of nanoparticles may be crucial for transfection. We present a novel plasmonic optoporation technique that uses Au nanostar layers immobilized in culture microplate wells. HeLa cells were grown directly on Au nanostar layers, after which they were subjected to continuous-wave 808 nm laser irradiation. An Au monolayer density ~15 μg/cm² and an absorbed energy of about 15 to 30 J were found to be optimal for optoporation. Propidium iodide molecules were used as model penetrating agent. The transfection efficiency evaluated using fluorescence microscopy for HeLa cells transfected with pGFP under optimized optoporation conditions (95% ± 5%) was similar to the efficiency of TurboFect. The technique's efficiency (295 ± 10 relative light units, RLU), demonstrated by transfecting HeLa cells with the pCMV-GLuc 2 control plasmid, was greater than that obtained by transfection of HeLa cells with the TurboFect agent (220 ± 10 RLU). The cell viability in plasmonic optoporation (92% ± 7%), too, was greater than that in transfection with TurboFect (75% ± 7%).

Polydopamine-coated Au nanorods for targeted fluorescent cell imaging and photothermal therapy

Au nanorods (AuNRs) have attracted a great interest as a platform for constructing various composite core/shell nanoparticles for theranostics applications. However, the development of robust methods for coating AuNRs with a biocompatible shell of high loading capacity and with functional groups still remains challenging. Here, we coated AuNRs with a polydopamine (PDA) shell and functionalized AuNR-PDA particles with folic acid and rhodamine 123 (R123) to fabricate AuNR-PDA-R123-folate nanocomposites. To the best of our knowledge, such AuNR-PDA-based composites combining fluorescent imaging and plasmonic phothothermal abilities have not been reported previously. The multifunctional nanoparticles were stable in cell buffer, nontoxic and suitable for targeted fluorescent imaging and photothermal therapy of cancer cells. We demonstrate the enhanced accumulation of folate-functionalized nanoparticles in folate-positive HeLa cells in contrast to the folate-negative HEK 293 cells using fluorescent microscopy. The replacement of folic acid with polyethylene glycol (PEG) leads to a decrease in nanoparticle uptake by both folate-positive and folate-negative cells. We performed NIR light-mediated targeted phototherapy using AuNR-PDA-R123-folate and obtained a remarkable cancer cell killing efficiency in vitro in comparison with only weak-efficient nontargeted PEGylated nanoparticles. Our work illustrates that AuNR-PDA could be a promising nanoplatform for multifunctional tumor theranostics in the future.

X-ray powder diffraction to analyse bimetallic core–shell nanoparticles (gold and palladium; 7–8 nm)

A comparative X-ray powder diffraction study on poly(N-vinyl pyrrolidone) (PVP)-stabilized palladium and gold nanoparticles and bimetallic Pd–Au nanoparticles (both types of core–shell nanostructures) was performed.

Bioresponsive-controlled release of methylene blue from magnetic mesoporous silica from the electrochemical detection of telomerase activity

An electrochemical sensing platform was designed to monitor telomerase activity in HeLa cells, using bioresponsively controlled cargo release from magnetic mesoporous silica nanocontainers (MMSNs). The aminated MMSNs were first synthesized by a wet-chemistry method, then methylene blue (indicator) molecules were loaded into the pores with the aid of specifically designed wrapping DNA strands, and then the wrapping DNA-gated MMSNs were immobilized on a magnetic removable screen-printing carbon electrode. Upon target telomerase and dNTP introduction into the detection cell, the wrapping DNA strands on the MMSNs were prolonged to form rigid hairpin-like DNA structures, thus resulting in the dissociation of wrapping DNA strands from the MMSNs. Thereafter, the loaded methylene blue with redox activity was released out from the pores, thereby causing the increase in the electrochemical signal relative to the background signal. Under optimal conditions, an MMSN-based sensing system exhibited good voltammetric responses toward target telomerase activity within the dynamic linear range of 50-5000 cells per mL at a detection limit of 12 cells per mL in the HeLa extract. The reproducibility and generality of our strategy were acceptable by using somatic tumor cell lines. In addition, the inhibition effect of this system was also evaluated by using 3'-azido-3'-deoxythymidine as a telomerase inhibitor, receiving good results in this screening research.

pH-sensitive radiolabeled and superfluorinated ultra-small palladium nanosheet as a high-performance multimodal platform for tumor theranostics

Radiolabeled nanomaterials, especially those with ultra-small structures, have been the research focus in recent years, and thus may open up new prospects for clinical diseases theranostics. Herein, fluorinated Pd nanosheets labeled with Gd or radionuclides are developed as multimodal platforms for tumor theranostics. These nanomaterials decorated by functional polyethylene glycol demonstrate ultrahigh ¹⁹F MRI signal, ultrasmall size and good dispersibility. These ultrasmall materials exhibit good biocompatibility and easily to be modified for multimodal imaging (SPECT/MRI/PAI) by assembling the functional groups like building blocks. Furthermore, with high accumulation in tumor sites, under the guidance of multimodal imaging, combined photothermal therapy and radiotherapy are performed and synergistic effects are obtained. By comparing the in vivo behaviors of nanostructures labeled by different nuclides, the present study suggests the pH-sensitive radioiodinated Pd nanosheet which has unexpected T/NT ratio (>4-fold tumor-to-muscle ratio) in SPECT imaging and solves the critical high background issue of nanoprobes, could improve diagnostic accuracy and guide combination therapy. In summary, this functionalized nanoplatform with promising imaging and therapeutic efficacy has great potential for precision theranostic nanomedicines.

Gold and gold-silver alloy nanoparticles enhance the myogenic differentiation of myoblasts through p38 MAPK signaling pathway and promote in vivo skeletal muscle regeneration

Under the severe trauma condition, the skeletal muscles regeneration process is inhibited by forming fibrous scar tissues. Understanding the interaction between bioactive nanomaterials and myoblasts perhaps has important effect on the enhanced skeletal muscle tissue regeneration. Herein, we investigate the effect of monodispersed gold and gold-silver nanoparticles (AuNPs and Au-AgNPs) on the proliferation, myogenic differentiation and associated molecular mechanism of myoblasts (C2C12), as well as the in vivo skeletal muscle tissue regeneration. Our results showed that AuNPs and Au-AgNPs could support myoblast attachment and proliferation with negligible cytotoxicity. Under various incubation conditions (normal and differentiation medium), AuNPs and Au-AuNPs significantly enhanced the myogenic differentiation of myoblasts by upregulating the expressions of myosin heavy chain (MHC) protein and myogenic genes (MyoD, MyoG and Tnnt-1). The further analysis demonstrated that AuNPs and Au-AgNPs could activate the p38α mitogen-activated protein kinase pathway (p38α MAPK) signaling pathway and enhance the myogenic differentiation. Additionally, the AuNPs and Au-AgNPs significantly promote the in vivo skeletal muscle regeneration in a tibialis anterior muscle defect model of rat. This study may provide a nanomaterials-based strategy to improve the skeletal muscle repair and regeneration.

Photoinduced Rapid Transformation from Au Nanoagglomerates to Drug-Conjugated Au Nanovesicles

Gold (Au) agglomerates (AGs) are reassembled using Triton X-100 (T) and doxorubicin (D) dissolved in ethanol under 185 nm photoirradiation to form TAuD nanovesicles (NVs) under ambient gas flow conditions. The positively charged Au particles are then electrostatically conjugated with the anionic chains of TD components via a flowing drop (FD) reaction. Photoirradiation of the droplets in a tubular reactor continues the photophysicochemical reactions, resulting in the reassembly of Au AGs and TD into TAuD NVs. The fabricated NVs are electrostatically collected onto a polished aluminum rod in a single-pass configuration. The dispersion of NVs is employed for bioassays to confirm uptake by cells and accumulation in tumors. The chemo-photothermal activity is determined both in vitro and in vivo. Different combinations of components are also used to fabricate NVs using the FD reaction, and these NVs are suitable for gene delivery as well. This newly designed gaseous single-pass process results in the reassembly of Au AGs for incorporation with TD without the need of batch wet chemical reactions, modifications, separations, or purifications. Thus, this process offers an efficient platform for preparing biofunctional Au nanostructures that requires neither complex physicochemical steps nor special storage techniques.