The optical, photothermal, and facile surface chemical properties of gold and silver nanoparticles in biodiagnostics, therapy, and drug delivery

An Overview for the Nanoparticles-Based Quantitative Lateral Flow Assay

The development of the lateral flow assay (LFA) has received much attention in both academia and industry because of their broad applications to food safety, environmental monitoring, clinical diagnosis, and so forth. The user friendliness, low cost, and easy operation are the most attractive advantages of the LFA. In recent years, quantitative detection has become another focus of LFA development. Here, the most recent studies of quantitative LFAs are reviewed. First, the principles and corresponding formats of quantitative LFAs are introduced. In the biomaterial and nanomaterial sections, the detection, capture, and signal amplification biomolecules and the optical, fluorescent, luminescent, and magnetic labels used in LFAs are described. The invention of dedicated strip readers has drawn further interest in exploiting the better performance of LFAs. Therefore, next, the development of dedicated reader devices is described and the usefulness and specifications of these devices for LFAs are discussed. Finally, the applications of LFAs in the detection of metal ions, biotoxins, pathogenic microorganisms, veterinary drugs, and pesticides in the fields of food safety and environmental health and the detection of nucleic acids, biomarkers, and viruses in clinical analyses are summarized.

Utility of Silver-nanoparticles for Nano-fluorimetric Determination of Vancomycin Hydrochloride in Pharmaceutical Formulation and Biological Fluids: Greenness Assessment

Vancomycin hydrochloride (VANH) is a glycopeptide antibiotic commonly employed in the prophylaxis and therapy of various gram-positive bacterial life-threatening infections. Due to the narrow therapeutic window of VANH, its serum levels should be well-monitored to avoid its toxicity and to optimize its therapy. Herein, an innovative silver-nanoparticles enhanced fluorescence technique was designed for VANH rapid analysis in its pharmaceutical formulation and biological fluids. This technique is based on reinforcement of VANH fluorescence intensity with silver-nanoparticles that were synthesized by a redox reaction between VANH and silver nitrate in NaOH alkaline medium using polyvinylpyrrolidone as a stabilizer. The produced silver-nanoparticles were characterized by using UV-visible spectroscopy where they have an intense absorption maximum at 415 nm and transmission electron microscope (TEM) micrograph where they are spherical in shape with smooth surface morphology and size of 10.74 ± 2.44 nm. The fluorescence intensity was measured at 394 nm after excitation at 259 nm. Under optimum conditions, a good linear relationship was accomplished between the VANH concentration and the fluorescence intensity in a range of (1-36) ng/mL with a limit of detection of 0.29 ng/mL. Greenness assessment was performed using two assessment tools namely; eco-scale scoring and green analytical procedure index revealing excellent greenness of the proposed technique. The proposed technique was validated according to the International Conference on Harmonisation (ICH) recommendations and statistically compared with the reported HPLC method revealing no significant difference concerning accuracy and precision at p = 0.05. The proposed technique depended primarily on water as a cheap and eco-friendly solvent.

Combining antibiotics with silver nanoparticles: A potential treatment strategy against antimicrobial resistance

Growing resistance to currently approved antibiotics is posing serious concern worldwide. The multidrug-resistant organisms are a major cause of mortality and morbidity around the globe. The limited options to treat infections caused by resistant organism requires alternative strategies to increase the effectiveness of antibiotic for better clinical outcomes. Recent advances in nanotechnology have enabled the drugs to be used in nanoscale to increase the effectiveness of antibiotics. The use of nanoparticles to treat infectious diseases has a long history in the pharmaceutical market, and the versatility of these particles to incorporate various materials as carriers make it an attractive option to combat the current crisis of emerging antibacterial resistance. Silver, a metal with many medical applications, has inherent antimicrobial properties. Therefore, silver NPs are appearing as one of the best options to be used in combination with antibiotics to increase effectiveness against resistant bacteria. Here, we discuss the applications and mechanisms of silver NPs to treat microbial resistance in light of recent research.

The lowest-energy structure of the gold cluster Au10: planar vs. nonplanar?

The onset of the transition from 2D to 3D structures in pure gold clusters remains a matter of continuing debate. In this theoretical study we revisit several planar and non-planar structural motifs of the size Au₁₀ with the aim to clarify this issue. Computations using a long-range corrected exchange-correlation functional LC-BLYP, coupled-cluster theories CCSD(T) and PNO-LCCSD(T)-F12 reveal that, at variance with previous reports on the preference of a planar elongated hexagon, both planar and nonplanar isomers of the neutral Au₁₀ are energetically degenerated up to 300 K. Its 3D equilibrium geometry is a core-shell structure which can be built up from a trigonal prism by capping four extra Au atoms outside. A comparison to the available experimental vibrational spectra allows us to argue that both lowest-lying 2D and 3D isomers of Au₁₀ likely coexist in the molecular beam during measurement of its FIR spectra. This result also suggests that the 2D-3D transition of neutral gold clusters occurs at the size Au₁₀.

Multimodal Gold Nanostars as SERS Tags for Optically-Driven Doxorubicin Release Study in Cancer Cells

Surface Enhanced Raman Scattering (SERS) active gold nanostars represent an opportunity in the field of bioimaging and drug delivery. The combination of gold surface chemical versatility with the possibility to tune the optical properties changing the nanoparticles shape constitutes a multimodal approach for the investigation of the behavior of these carriers inside living cells. In this work, SERS active star-shaped nanoparticles were functionalized with doxorubicin molecules and covered with immuno-mimetic thiolated polyethylene glycol (PEG). Doxorubicin-conjugate gold nanoparticles show an intense Raman enhancement, a good stability in physiological conditions, and a low cytotoxicity. The strong adsorption of the anticancer drug doxorubicin in close contact with the gold nanostars surface enables their use as SERS tag imaging probes in vivo. Upon laser irradiation of the nanoparticles, a strong SERS signal is generated by the doxorubicin molecules close to the nanostars surface, enabling the localization of the nanoparticles inside the cells. After long time irradiation, the SERS signal drops, indicating the thermally driven delivery of the drug inside the cell. Therefore, the combination of SERS and laser scanning confocal microscopy is a powerful technique for the real-time analysis of drug release in living cells.

Nanoparticle Systems for Cancer Phototherapy: An Overview

Photodynamic therapy (PDT) and photothermal therapy (PTT) are photo-mediated treatments with different mechanisms of action that can be addressed for cancer treatment. Both phototherapies are highly successful and barely or non-invasive types of treatment that have gained attention in the past few years. The death of cancer cells because of the application of these therapies is caused by the formation of reactive oxygen species, that leads to oxidative stress for the case of photodynamic therapy and the generation of heat for the case of photothermal therapies. The advancement of nanotechnology allowed significant benefit to these therapies using nanoparticles, allowing both tuning of the process and an increase of effectiveness. The encapsulation of drugs, development of the most different organic and inorganic nanoparticles as well as the possibility of surfaces' functionalization are some strategies used to combine phototherapy and nanotechnology, with the aim of an effective treatment with minimal side effects. This article presents an overview on the use of nanostructures in association with phototherapy, in the view of cancer treatment.

Harvesting Light To Produce Heat: Photothermal Nanoparticles for Technological Applications and Biomedical Devices

The photothermal properties of nanoparticles (NPs), that is, their ability to convert absorbed light into heat, have been studied since the end of the last century, mainly on gold NPs. In the new millennium, these studies have developed into a burst of research dedicated to the photothermal ablation of tumors. However, beside this strictly medical theme, research has also flourished in the connected areas of photothermal antibacterial surface coatings, gels and polymers, of photothermal surfaces for cell stimulation, as well as in purely technological areas that do not involve medical biotechnology. These include the direct conversion of solar light into heat, a more efficient sun-powered generation of steam and the use of inkjet-printed patterns of photothermal NPs for anticounterfeit printing based on temperature reading, to cite but a few. After an analysis of the photothermal effect (PTE) and its mechanism, this minireview briefly considers the antitumor-therapy theme and takes an in-depth look at all the other technological and biomedical applications of the PTE, paying particular attention to photothermal materials whose NPs have joined those based on Au.

Assessment of the Antibacterial Potential of Biosynthesized Silver Nanoparticles Combined with Vancomycin Against Methicillin-Resistant Staphylococcus aureus-Induced Infection in Rats

Methicillin-resistant Staphylococcus aureus (MRSA) is considered one of the most serious multidrug-resistant bacteria worldwide. MRSA resistance to methicillin antibiotics made vancomycin, the acceptable treatment option. Silver nanoparticles (Ag-NPs) are among the well-known antibacterial substances showing multimode antibacterial action. Therefore, Ag-NPs are appropriate applicants for use in combination with vancomycin in order to augment its antibacterial action. This study aimed to biosynthesize silver nanoparticles and to evaluate its antibacterial activity against MRSA alone and when combined with vancomycin both in vitro and in vivo. Agaricus bisporus is used to reduce the silver nitrate salts in solution to yield silver nanoparticles which was characterized by UV-visible spectrophotometric analysis that shows maximum absorption at 420 nm as a preliminary confirmation for nanoparticles synthesis, Energy-Dispersive Analysis of X-ray (EDX) which confirms the crystalline nature of silver nanoparticles and transmission electron microscopy (TEM) image shows the particles in spherical form with mean size 27.45 nm. The synthesized silver nanoparticles were tested for antibacterial activity against MRSA, and the synergetic effects of the combination of silver nanoparticles and vancomycin were evaluated. The results showed a strong synergistic antibacterial effect between Ag-NPs and vancomycin in vitro with fractional inhibitory concentration 0.37 and in vivo against MRSA strain. The result revealed that mycosynthesized silver nanoparticles (NPs) enhance the in vitro and in vivo antibacterial activity of vancomycin against MRSA. These results suggested that sliver nanoparticles have an effective antibacterial activity against MRSA count, histopathology, and liver enzymes as well as protective immune response specially when combined with vancomycin in the lungs of infected rats with MRSA.

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.

Photophysics of Ag and Au alloys of M25(SR)18 clusters

Superatom clusters, Au₂₅(SR)₁₈, and the silver analog and alloys of the two metals have been extensively investigated for their structure, stability, photoluminescence, and electronic properties. One can readily tune the physicochemical properties by varying the ratio of Au/Ag or the thiol ligand to attain desired properties, such as enhanced emission, increased stability, and catalytic activity. Herein, excitation emission matrix spectroscopy and pump-probe transient absorption spectroscopy are used to show that the excited state dynamics of Au₂₅(SR)₁₈, Ag₂₅(SR)₁₈, and their alloys differ significantly despite having similar structures. State-resolved excited state behavior that is well documented for gold clusters is largely affected by the metal composition, becoming less pronounced for silver analogs, resulting in diversity in terms of their excited state energy and relaxation dynamics and resultant photophysical properties, such as emission.

Near infrared photothermal conversion materials: mechanism, preparation, and photothermal cancer therapy applications

Photothermal therapy (PTT) has been widely applied in cancer therapy as a result of its non-invasive, localized treatment and good therapeutic effect. In general, the final therapeutic effect of PTT mainly depends on the photothermal materials, which can be further considered to be determined by the photothermal conversion efficiency, biocompatibility, and photothermal stability of photothermal materials. In this review, photothermal materials including inorganic materials, organic materials, and organic-inorganic composite materials in recent years have been summarized in terms of the mechanism, preparation, and cancer therapy applications. In the end, the perspectives and obstacles in their further development are overviewed.

Adsorption/Desorption Behaviors and SERS Chemical Enhancement of 6-Mercaptopurine on a Nanostructured Gold Surface: The Au20 Cluster Model

Computational approaches are employed to elucidate the binding mechanism and the SERS phenomenon of 6-mercaptopurine (6MP) adsorbed on the tetrahedral Au20 cluster as a simple model for a nanostructured gold surface. Computations are carried out in both vacuum and aqueous environments using a continuum model. In the gaseous phase and neutral conditions, interaction of 6MP with the gold cluster is mostly dominated by a covalent Au-S bond and partially stabilized by the Au⋅⋅⋅H-N coupling. However, in acidic solution, the nonconventional Au⋅⋅⋅H-S hydrogen-bond becomes the most favorable binding mode. The 6MP affinity for gold clusters decreases in the order of vacuum > neutral solution > acidic medium. During the adsorption, the energy gap of Au20 substantially declines, leading to an increase in its electrical conductivity, which can be converted to an electrical noise. Moreover, such interaction is likely a reversible process and triggered by either the low pH in sick tissues or the presence of cysteine residues in protein matrices. While N-H bending and stretching vibrations play major roles in the SERS phenomenon of 6MP on gold surfaces in neutral solution, the strongest enhancement in acidic environment is mostly due to an Au⋅⋅⋅H-S coupling, rather than an aromatic ring-gold surface π overlap as previously proposed.

The Therapeutic Effect of Second Near-Infrared Absorbing Gold Nanorods on Metastatic Lymph Nodes via Lymphatic Delivery System

Photothermal therapy has been established recently as a non-invasive treatment protocol for cancer metastatic lymph nodes. Although this treatment approach shows efficient tumour ablation towards lymph node metastasis, the monitoring and reporting of treatment progress using the lymphatic delivery channel still need to be explored. Herein, we investigated the anti-tumour effect of pegylated gold nanorods with a high aspect ratio (PAuNRs) delivered via the lymphatic route in a mouse model. In this study, breast carcinoma (FM3A-Luc) cells were inoculated in the subiliac lymph node (SiLN) to induce metastasis in the proper axillary lymph node (PALN). The treatment was initiated by injecting the PAuNRs into the accessory axillary lymph node (AALN) after tumour metastasis was confirmed in the PALN followed by external NIR laser irradiation under a temperature-controlled cooling system. The anti-tumour impact of the treatment was evaluated using an in vivo bioluminescence imaging system (IVIS). The results showed a time-dependent reduction in tumour activity with significant treatment response. Tumour growth was inhibited in all mice treated with PAuNRs under laser irradiation; results were statistically significant (** p < 0.01) even after treatment was concluded on day 3. We believe that this non-invasive technique would provide more information on the dynamics of tumour therapy using the lymphatically administered route in preclinical studies.

Facile synthesis of metal nanoparticle-loaded polymer nanocomposite with highly efficient an optically enhanced biocidal and anticancer agents

In this work, we prepared silver nanoparticles (AgNPs)-loaded poly(2,5-dimethoxyaniline;PDMA) nanocomposite via a simple chemical oxidative method to develop new effective biocidal and anticancer agents systems. In situ UV-vis and fluorescence spectroscopy has been used to monitor the formation of PDMA/Ag is strongly dependent on the concentration of PDMA in the present system. The FTIR and XRD studies exhibit that the rate of polymer formation and oxidation state of PDMA/Ag nanocomposite, which confirmed the AgNPs is strongly binding with the PDMA matrix. SEM and EDAX analysis revealed the presence of uniform size and the highest percentage of AgNPs (42.1%) in the PDMA/Ag nanocomposite. TEM and size distribution analysis revealed the presence of spherical AgNPs with an average diameter of 25 nm in the PDMA/Ag nanocomposite. In addition, the PDMA polymer with embedded AgNPs exhibited excellent antibacterial performance against Escherichia coli and Staphylococcus aureus. Interestingly, the prepared PDMA/Ag nanocomposite exhibited enhanced bactericidal performance compared with the PDMA polymer, presumably because of the antibacterial properties of the AgNPs substrate. The anticancer effects of combined treatment with PDMA polymer and AgNPs were evaluated using a series of cellular and biochemical assays. The findings from this study revealed that the PDMA/Ag nanocomposite treatment significantly inhibited cell viability and proliferation of the human cervical cancer cell line (HeLa). The PDMA/Ag nanocomposite exhibits better antibacterial and anticancer activities compare to pristine PDMA.

Gold Nanorods are Selective Cytotoxic Agents

BACKGROUND

Gold nanorods (GNRs) are very promising agents that have multiple applications in medicine and biology. However, the cytotoxic effects of GNRs have not been fully explored.

OBJECTIVE

Therefore, the main objective of this study was to determine the selective cytotoxic effect of GNRs towards several human tumor cell lines.

METHODS

To address this issue, three sizes of GNRs (10-nm, 25-nm, and 50-nm) were tested against two human tumor cell lines, namely, human hepatoma HepG2 and human prostate PC3 cancer cells. As GNRs are usually stored in soft tissues inside living bodies, we also tested the effect of GNRs on murine splenocyte viability. To determine if the GNRs displayed selectivity cytotoxicity towards cancer cells, active GNRs with the size showing the least cytotoxicity to splenocytes were then tested against a panel of 11 human tumor cell lines and two human non-tumor cell lines.

RESULTS

Our results showed that the most cytotoxic size of GNRs is 10-nm, followed by the 25-nm GNRs, while the 50-nm GNRs did not show a significant effect. In addition, the 25-nm GNRs were the least cytotoxic to splenocytes when tested for 24 and 48 h. These GNRs showed a selective cytotoxic effect to prostate cancer PC3 cells with median inhibitory concentration (IC50) = 8.3 + 0.37 µM, myeloblastic leukemia HL60 cells (IC50 = 19.7 + 0.89 µM), cervical cancer HeLa cells (IC50 = 24.6 + 0.37 µM), renal adenocarcinoma 786.0 cells (IC50 = 27.34 + 0.6 µM), and hepatoma HepG2 cells (IC50 = 27.79 + 0.03 µM) when compared to the effect on the non-tumor human cells; skin fibroblast BJ cell line (IC50 = 40.13 + 0.7 µM) or epithelial breast MCF10A cells (IC50 = 33.2 + 0.89 µM). A high selectivity indices (SI) were observed in GNRs-treated PC3 and HL60 cells with values ranging from 1.69 to 4.83, whereas moderate SIs were observed in GNRs-treated HeLa, 786.0, and HepG2 cells with values ranging from 1.19 to 1.63. Other cells did not show a similar selective effect, including human laryngeal HEp2 cells, colon HCT116, metastatic renal adenocarcinoma ACHN cells, and human breast cancer cells (MCF7, MDA-MB-231, and MDA-MB-468 cells). The effect of GNRs was confirmed using the colony formation assay and the effect was found to be cell cycle specific. Finally, it was shown that laser treatment can potentiate the cytotoxic effect of the 25-nm GNRs.

CONCLUSION

GNRs are selective cytotoxic agents and they have the potential to act as candidate anticancer agents.

Computational and Experimental Analysis of Gold Nanorods in Terms of Their Morphology: Spectral Absorption and Local Field Enhancement

A nanoparticle's shape and size determine its optical properties. Nanorods are nanoparticles that have double absorption bands associated to surface plasmon oscillations along their two main axes. In this work, we analize the optical response of gold nanorods with numerical simulations and spectral absorption measurements to evaluate their local field enhancement-which is key for surface-enhanced Raman spectroscopic (SERS) applications. Our experimental results are in good agreement with finite element method (FEM) simulations for the spectral optical absorption of the nanoparticles. We also observed a strong dependence of the optical properties of gold nanorods on their geometrical dimension and shape. Our numerical simulations helped us reveal the importance of the nanorods' morphology generated during the synthesis stage in the evaluation of absorption and local field enhancement. The application of these gold nanorods in surface-enhancement Raman spectroscopy is analyzed numerically, and results in a 5.8×104 amplification factor when comparing the values obtained for the nanorod deposited on a dielectric substrate compared to the nanorod immersed in water.

Nanomedicine: A Diagnostic and Therapeutic Approach to COVID-19

The SARS-CoV-2 virus is causing devastating morbidity and mortality worldwide. Nanomedicine approaches have a high potential to enhance conventional diagnostics, drugs and vaccines. In fact, lipid nanoparticle/mRNA vaccines are already widely used to protect from COVID-19. In this review, we present an overview of the taxonomy, structure, variants of concern, epidemiology, pathophysiology and detection methods of SARS-CoV-2. The efforts of repurposing, tailoring, and adapting pre-existing medications to battle COVID-19 and the state of vaccine developments are presented. Next, we discuss the broad concepts and limitations of how nanomedicine could address the COVID-19 threat. Nanomaterials are particles in the nanometer scale (10-100 nm) which possess unique properties related to their size, polarity, structural and chemical composition. Nanoparticles can be composed of precious metals (copper, silver, gold), inorganic materials (graphene, silicon), proteins, carbohydrates, lipids, RNA/DNA, or conjugates, combinations and polymers of all of the aforementioned. The advanced biochemical features of these nanoscale particles allow them to directly interact with virions and irreversibly disrupt their structure, which can render a virus incapable of replicating within the host. Virus-neutralizing coats and surfaces impregnated with nanomaterials can enhance personal protective equipment, hand sanitizers and air filter systems. Nanoparticles can enhance drug-based therapies by optimizing uptake, stability, target cell-specific delivery, and magnetic properties. In fact, recent studies have highlighted the potential of nanoparticles in different aspects of the fight against SARS-CoV-2, such as enhancing biosensors and diagnostic tests, drug therapies, designing new delivery mechanisms, and optimizing vaccines. This article summarizes the ongoing research on diagnostic strategies, treatments, and vaccines for COVID-19, while emphasizing the potential of nanoparticle-based pharmaceuticals and vaccines.

Biomaterials-Based Delivery of Therapeutic Antibodies for Cancer Therapy

Considerable breakthroughs in the treatment of malignant tumors using antibody drugs, especially immunomodulating monoclonal antibodies (mAbs), have been made in the past decade. Despite technological advancements in antibody design and manufacture, multiple challenges face antibody-mediated cancer therapy, such as instability in vivo, poor tumor penetration, limited response rate, and undesirable off-target cytotoxicity. In recent years, an increasing number of biomaterials-based delivery systems have been reported to enhance the antitumor efficacy of antibody drugs. This review summarizes the advances and breakthroughs in integrating biomaterials with therapeutic antibodies for enhanced cancer therapy. A brief introduction to the principal mechanism of antibody-based cancer therapy is first established, and then various antibody immobilization strategies are provided. Finally, the current state-of-the-art in biomaterials-based antibody delivery systems and their applications in cancer treatment are summarized, highlighting how the delivery systems augment the therapeutic efficacy of antibody drugs. The outlook and perspective on biomaterials-based delivery of antitumor antibodies are also discussed.

Gold nanoclusters as prospective carriers and detectors of pramipexole

Pramipexole (PPX) is known in the treatment of Parkinson's disease and restless legs syndrome. We carried out a theoretical investigation on pramipexole-Au cluster interactions for the applications of drug delivery and detection. Three Au N clusters with sizes N = 6, 8 and 20 were used as reactant models to simulate the metallic nanostructured surfaces. Quantum chemical computations were performed in both gas phase and aqueous environments using density functional theory (DFT) with the PBE functional and the cc-pVDZ-PP/cc-pVTZ basis set. The PPX drug is mainly adsorbed on gold clusters via its nitrogen atom of the thiazole ring with binding energies of ca. -22 to -28 kcal mol-1 in vacuum and ca. -18 to -24 kcal mol-1 in aqueous solution. In addition to such Au-N covalent bonding, the metal-drug interactions are further stabilized by electrostatic effects, namely hydrogen-bond NH⋯Au contributions. Surface-enhanced Raman scattering (SERS) of PPX adsorbed on the Au surfaces and its desorption process were also examined. In comparison to Au8, both Au6 and Au20 clusters undergo a shorter recovery time and a larger change of energy gap, being possibly conducive to electrical conversion, thus signaling for detection of the drug. A chemical enhancement mechanism for SERS procedure was again established in view of the formation of nonconventional hydrogen interactions Au⋯H-N. The binding of PPX to a gold cluster is expected to be reversible and triggered by the presence of cysteine residues in protein matrices or lower-shifted alteration of environment pH. These findings would encourage either further theoretical probes to reach more accurate views on the efficiency of pramipexole-Au interactions, or experimental attempts to build appropriate gold nanostructures for practical trials, harnessing their potentiality for applications.

Effect of various synthesis parameters on the stability of size controlled green synthesis of silver nanoparticles

In this study, we have focused on the green method using Litchi Chinensis Leaf Extract (LCLE) for the synthesis of silver nanoparticles (AgNPs). Here, the experimental control parameters (reducing/stabilizing agent quantity, reaction time and temperature, silver ion concentrations) were studied during the size controlled synthesis of silver nanoparticles and their physicochemical properties have been studied. For biological studies, the stability of AgNPs at physiological pH is of vital importance; hence, post-synthesis solution stability of AgNPs was examined at various pH conditions. Stable AgNPs are formed by treating the aqueous solution of AgNO3 with LCLE. Formation of AgNPs was observed visually by the change in the color and further characterized by the surface Plasmon resonance (SPR) peak observed at 436 nm by UV–vis spectroscopy. The synthesized AgNPs were also characterized for their size distribution by Dynamic Light Scattering (DLS), Scanning Electron Microscopy (SEM), Transmission electron microscope (TEM), crystalline nature by X-Ray Diffraction (XRD) and Fourier Transform infrared (FITR) for the functional groups present. The size of AgNPs was in the range of 40–50 nm, spherical in with face centered cubic (FCC) structure. The biomolecules (epicatechin) present in LCLE were responsible for reduction, capping, and stabilizing agent of AgNPs. Post- synthesis, the stability of AgNPs has been studied by changes in the SPR peaks at various pH (2–11) conditions using UV–vis spectroscopy. This size controlled nanoparticles are very stable at physiological pH and retain their intrinsic SPR property.

Evaluating Phospholipid-Functionalized Gold Nanorods for In Vivo Applications

Gold nanorods (AuNRs) have attracted a great deal of attention due to their potential for use in a wide range of biomedical applications. However, their production typically requires the use of the relatively toxic cationic surfactant cetyltrimethylammonium bromide (CTAB) leading to continued demand for protocols to detoxify them for in vivo applications. In this study, a robust and facile protocol for the displacement of CTAB from the surface of AuNRs using phospholipids is presented. After the displacement, CTAB is not detectable by NMR spectroscopy, surface-enhanced Raman spectroscopy, or using pH-dependent ζ-potential measurements. The phospholipid functionalized AuNRs demonstrated superior stability and biocompatibility (IC₅₀  > 200 µg mL^-1 ) compared to both CTAB and polyelectrolyte functionalized AuNRs and are well tolerated in vivo. Furthermore, they have high near-infrared (NIR) absorbance and produce large amounts of heat under NIR illumination, hence such particles are well suited for plasmonic medical applications.

Highlighting the use of micro and nanoparticles based-drug delivery systems for the treatment of Helicobacter pylori infections

Due to the high adaptability of Helicobacter pylori and the low targeting specificity of the drugs normally used in pharmacological therapy, the strains are becoming increasingly resistant to these drugs, making it difficult to eradicate the infection. Thus, the search for new therapeutic approaches has been considered urgent. The incorporation of drugs in advanced drug delivery systems, such as nano and microparticles, would allow the improvement of the retention time in the stomach and the prolongation of drug release rates at the target site. Because of this, the present review article aims to highlight the use of micro and nanoparticles as important technological tools for the treatment of H. pylori infections, focussing on the main nanotechnological systems, including nanostructured lipid carriers, liposomes, nanoemulsion, metallic nanoparticles, and polymeric nanoparticles, as well as microtechnological systems such as gastroretentive dosage forms, among them mucoadhesive, magnetic and floating systems were highlighted.

Noble Metal Nanomaterials for NIR-Triggered Photothermal Therapy in Cancer

It is of great significance to develop anticancer therapeutic agents or technologies with high degree of specificity and patient compliance, while low toxicity. The emerging photothermal therapy (PTT) has become a new and powerful therapeutic technology due to its noninvasiveness, high specificity, low side effects to normal tissues and strong anticancer efficacy. Noble metal nanomaterials possess strong surface plasmon resonance (SPR) effect and synthetic tunability, which make them facile and effective PTT agents with superior optical and photothermal characteristics, such as high absorption cross-section, incomparable optical-thermal conversion efficiency in the near infrared (NIR) region, as well as the potential of bioimaging. By incorporating with various functional reagents such as antibodies, peptides, biocompatible polymers, chemo-drug and immune factors, noble metal nanomaterials have presented strong potential in multifunctional cancer therapy. Herein, the recent development regarding the application of noble metal nanomaterials for NIR-triggered PTT in cancer treatment is summarized. A variety of studies with good therapeutic effects against cancer from impressive photothermal efficacy of noble metal nanomaterials are concluded. Intelligent nanoplatforms through ingenious fabrication showing potential of multifunctional PTT, combined with chemo-therapy, immunotherapy, photodynamic therapy (PDT), as well as simultaneous imaging modality are also demonstrated.

Nanosystem functionalization strategies for prostate cancer treatment: a review

Prostate cancer (PC) has a high morbidity and mortality rate worldwide, and the current clinical guidelines can vary depending on the stage of the disease. Drug delivery nanosystems (DDNs) can improve biopharmaceutical properties of encapsulated anti-cancer drugs by modulating their release kinetics, improving physicochemical stability and reducing toxicity. DDN can also enhance the ability of specific targeting through surface modification by coupling ligands (antibodies, nucleic acids, peptides, aptamer, proteins), thus favouring the cell internalisation process by endocytosis. The purposes of this review are to describe the limitations in the treatment of PC, explore different functionalization such as polymeric, lipid and inorganic nanosystems aimed at the treatment of PC, and demonstrate the improvement of this modification for an active target, as alternative and promising candidates for new therapies.

PEGylation of Dendronized Gold Nanoparticles Affects Their Interaction with Thrombin and siRNA

The use of nonviral carriers based on nanomaterials is a promising strategy for modern gene therapy aimed at protecting the genetic material against degradation and enabling its efficient cellular uptake. To improve the effectiveness of nanocarriers in vivo, they are often modified with poly(ethylene glycol) (PEG) to reduce their toxicity, limit nonspecific binding by proteins in the bloodstream, and extend blood half-life. Thus, the selection of an appropriate degree of surface PEGylation is crucial to preserve the interaction of nanoparticles with the genetic material and to ensure its efficient transport to the site of action. Our research focuses on the use of innovative gold nanoparticles (AuNPs) coated with cationic carbosilane dendrons as carriers of siRNA. In this study, using dynamic light scattering and zeta potential measurements, circular dichroism, and gel electrophoresis, we investigated dendronized AuNPs modified to varying degrees with PEG in terms of their interactions with siRNA and thrombin to select the most promising PEGylated carrier for further research.

A review on the green and sustainable synthesis of silver nanoparticles and one-dimensional silver nanostructures

The significance of silver nanostructures has been growing considerably, thanks to their ubiquitous presence in numerous applications, including but not limited to renewable energy, electronics, biosensors, wastewater treatment, medicine, and clinical equipment. The properties of silver nanostructures, such as size, size distribution, and morphology, are strongly dependent on synthesis process conditions such as the process type, equipment type, reagent type, precursor concentration, temperature, process duration, and pH. Physical and chemical methods have been among the most common methods to synthesize silver nanostructures; however, they possess substantial disadvantages and short-comings, especially compared to green synthesis methods. On the contrary, the number of green synthesis techniques has been increasing during the last decade and they have emerged as alternative routes towards facile and effective synthesis of silver nanostructures with different morphologies. In this review, we have initially outlined the most common and popular chemical and physical methodologies and reviewed their advantages and disadvantages. Green synthesis methodologies are then discussed in detail and their advantages over chemical and physical methods have been noted. Recent studies are then reviewed in detail and the effects of essential reaction parameters, such as temperature, pH, precursor, and reagent concentration, on silver nanostructure size and morphology are discussed. Also, green synthesis techniques used for the synthesis of one-dimensional (1D) silver nanostructures have been reviewed, and the potential of alternative green reagents for their synthesis has been discussed. Furthermore, current challenges regarding the green synthesis of 1D silver nanostructures and future direction are outlined. To sum up, we aim to show the real potential of green nanotechnology towards the synthesis of silver nanostructures with various morphologies (especially 1D ones) and the possibility of altering current techniques towards more environmentally friendly, more energy-efficient, less hazardous, simpler, and cheaper procedures.

Nano Metal based Herbal theranostics for Cancer management: coalescing nature's boon with nanotechnological advancement

Cancer is amongst the leading public health problems globally with continuously increasing prevalence rate that demands for extensive and expensive treatment. Despite availability of number of potential cancer therapies, inadequate success has been achieved due to complexity and heterogeneity of tumors. Moreover, late/ terminal stage cancer leads to multidrug resistance, excruciating side effects, recurrence, etc. This is because of low penetrability and deleterious effects of drug on non-target cells/ tissues. This requires for cost effective, efficacious, alternative/ adjunct, complementary medicines with targeted drug delivery approach. A potential strategy to resolve this difficulty is to use theranostics i.e., formulations having both a therapeutic element and an imaging agent. Phytotherapeutics have been extensively used since times immemorial, having wide acceptability, easy availability, minimal side effects and comparatively inexpensive. These herbal formulations are mostly orally administered and thus subjected to adverse pH, enzymatic degradation, poor gut absorption, low bioavailability and non-targeted delivery that ultimately lead to their poor effectiveness. Constraints associated with conventional phyto-pharmaceuticals can be improved by designing and using "Nano Delivery Systems" (NDS). The foremost aim of metal based NDS is to provide sustained drug release, site-specific action, improved patient's compliance and enhanced efficacy. Metal Nanocarriers carrying herbal drugs will avoid these obstructions, so the drug can circulate into the blood for a longer period of time and provide optimal amount of the drug to the site of action. Besides, Herbal drugs with NDS thus would be efficacious as alternative/ complementary cancer theranostics. Present review describes about novel theranostic systems employing metal nanocarriers with diagnostic and therapeutic properties as are an effective strategy for cancer treatment. These systems when conjugated with herbal drugs provide an efficient management strategy for cancer.

Advances in Hollow Inorganic Nanomedicines for Photothermal-Based Therapies

Nanotechnology has prompted the development of hollow inorganic nanomedicine. These medicines are now widely investigated as photothermal-based therapies for various diseases due to their high loading capacity, tuneable wavelength, relatively small size and low density. We begin this review with a brief introduction, followed by a summary of the development of imaging-guided photothermal therapy (PTT) for cancer treatment during the last three years (from 2017 to 2020). We then introduce the antibacterial effects of these medicines on some bacterial infections, in which the pathogenic bacteria can be killed by mild photothermal effects, ions and antibiotic release. Other diseases can also be treated using hollow inorganic photothermal agents. Specifically, we discuss the use of PTT for treating Alzheimer's disease, obesity and endometriosis. Finally, we share our perspectives on the current challenges and future prospects of using hollow inorganic materials in clinical PTT for various diseases.

Pathogenic Virus Detection by Optical Nanobiosensors

The novel coronavirus pandemic is sweeping the world and causing global crises. The lack of effective methods of early diagnosis and accurate detection may result in severe infection as well as mortality. Therefore, it is urgently required that rapid, selective, and accurate techniques for detecting pathogenic viruses are developed. Nanotechnology-based biosensors are finding many applications in biological detection, which may address these issues and realize direct detection of molecular targets in real time. Among various nanoplatforms, optical nanobiosensors have aroused much interest due to their inherent advantages of high sensitivity and direct readout. In this review, a summary of recent progress on the optical biosensors based on nanotechnology for pathogenic virus detection is provided, with focus on quantum dots (QDs), upconversion nanoparticles (UCNPs), noble metal nanoparticles, and organic fluorescent molecules-based nanoprobes and chemiluminescence assays. These representative studies demonstrate appealing performance as biosensors and hold great promise for clinical diagnosis.

FRET-based fluorescent probe for drug assay from amino acid@gold-carbon nanoparticles

Biocompatible and luminescent nanostructures synthesized by capping gold-carbon nanoparticles (HOOC-4-C₆H₄-AuNPs) with amino acids tyrosine, tryptophan, and cysteine were used for the quantitative estimation of ranitidine (RNH), a peptic ulcer and gastroesophageal reflux drug. We applied a fluorescence quenching mechanism to investigate the viability of the energy transfer based on gold-carbon nanosensors. Förster resonance energy transfer (FRET) calculations showed a donor-acceptor distance of 1.69 nm (Tyr@AuNPs), 2.27 nm (Trp@AuNPs), and 2.32 nm (Cys@AuNPs). The constant time-resolved fluorescence lifetime measurements supported the static quenching nature. This method was successfully utilized in the detection and quantification of RNH, with a limit of detection (LOD) of 0.174, 0.56, and 0.332 μM for Tyr@AuNP, Trp@AuNP, and Cys@AuNP bioconjugates, respectively. This approach was also successful in the quantification of RNH in spiked serum samples.

Gold nanoparticles produce transient reactive gliosis in the adult brain

Gold nanoparticles (GNPs) have unique physical and chemical properties that allow them to function as a drug-delivery system for several tissues: skin, eye, liver, and others. However, information about the biological response of brain tissue against GNPs is limited. Astrocytes and microglia cells are the first line of defense against brain insults and proper indicators of the level of brain damage. This study was aimed to evaluate the astrocytic and microglia response after an intracerebral injection of polyethylene-glycol-coupled GNPs (PEGylated GNPs). We injected spherical PEGylated GNPs (85 × 10⁶ nanoparticles /nl) with a glass micropipette (inner diameter =35 μm) into the striatum of P60 CD1 mice. We evaluated the cellular response of astrocytes and microglia on days 3, 7, 14, 30, and 90 after intracerebral injection. For both astrocytes and microglia cells, our findings indicated that the glial response was transient and mainly circumscribed to the injection site. This evidence suggests that PEGylated GNPs are well-tolerated by the neural tissue. Understanding the effects of GNPs in the adult brain is a crucial step to design proper pharmacological vehicles to deliver long-lasting drugs.

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

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

Effect of AuNPs and AgNPs on the Antioxidant System and Antioxidant Activity of Lavender (Lavandula angustifolia Mill.) from In Vitro Cultures

The aim of this study was to determine the effect of gold and silver nanoparticles on the activity of antioxidant enzymes (ascorbate peroxidase (APX), superoxide dismutase (SOD), guaiacol peroxidase (POX), and catalase (CAT)), the free radical scavenging capacity, and the total polyphenol capacity of lavender (Lavandula angustifolia Mill.) cultivar “Munstead” propagated in vitro. In the experiment, fragments of lavender plants were cultivated in vitro on medium with the addition of 1, 2, 5, 10, 20, and 50 mg∙dm⁻³ of AgNPs or AuNPs (particle sizes 24.2 ± 2.4 and 27.5 ± 4.8 nm, respectively). It was found that the nanoparticles increase the activity of the antioxidant enzymes APX and SOD; however, the reaction depends on the NP concentration. The highest APX activity is found in plants propagated on media with 2 and 5 mg∙dm⁻³ of AgNPs. AuNPs significantly increase the APX activity when added to media with a concentration of 10 mg∙dm⁻³. The highest SOD activity is recorded at 2 and 5 mg∙dm⁻³ AgNP and AuNP concentrations. The addition of higher concentrations of nanoparticles to culture media results in a decrease in the APX and SOD activity. The addition of AuNPs to culture media at concentrations from 2 to 50 mg∙dm⁻³ increases the POX activity in comparison to its activity when AgNPs are added to the culture media. No significant influence of NPs on the increase in CAT activity was demonstrated. AgNPs and AuNPs increased the free radical scavenging capacity (ABTS^•+). The addition of NPs at concentrations of 2 and 5 mg∙dm⁻³ increased the production of polyphenols; however, in lower concentrations it decreased their content in lavender tissues.