A highly sensitive electrochemical sensor based on poly(3-aminobenzoic acid)/graphene oxide-gold nanoparticles modified screen printed carbon electrode for paraquat detection.

Herein, a modified screen printed carbon electrode (SPCE) based on a composite material, graphene oxide-gold nanoparticles (GO-AuNPs), and poly(3-aminobenzoic acid)(P3ABA) for the detection of paraquat (PQ) is introduced. The modified electrode was fabricated by drop casting of the GO-AuNPs, followed by electropolymerization of 3-aminobenzoic acid to achieve SPCE/GO-AuNPs/P3ABA. The morphology and microstructural characteristics of the modified electrodes were revealed by scanning electron microscopy (SEM) for each step of modification. The composite GO-AuNPs can provide high surface area and enhance electroconductivity of the electrode. In addition, the presence of negatively charged P3ABA notably improved PQ adsorption and electron transfer rate, which stimulate redox reaction on the modified electrode, thus improving the sensitivity of PQ analysis. The SPCE/GO-AuNPs/P3ABA offered a wide linear range of PQ determination (10-9-10-4 mol/L) and low limit of detection (LOD) of 0.45 × 10-9 mol/L or 0.116 µg/L, which is far below international safety regulations. The modified electrode showed minimum interference effect with percent recovery ranging from 96.5% to 116.1% after addition of other herbicides, pesticides, metal ions, and additives. The stability of the SPCE/GO-AuNPs/P3ABA was evaluated, and the results indicated negligible changes in the detection signal over 9 weeks. Moreover, this modified electrode was successfully implemented for PQ analysis in both natural and tapped water with high accuracy.

Revisited UV- spectra of chlorohydroxoaurate anions.

The most important ionic precursor of gold, [AuCl4]-, is used in aqueous solution leading to chlorohydroxoaurates species, [AuCl4-x(OH)x]- (x = 1-4) due to partial hydrolysis. Their UV spectral signatures are still relatively unknown though very useful in many domains of application. Individual spectra of each of them are determined for the first time thanks to a thorough experimental investigation comprising the range 200-250 nm, surpringly ignored up to now. New isosbestic points useful for species partition analysis are evidenced. Electronic transition attribution is obtained from quantum chemical calculations based on TD-DFT. The prediction of the experimental blueshifted bands of the [AuCl4-x(OH)x]-1 anions was possible only after applying energy corrections calibrated on the full UV range two-band spectrum of the [AuCl4]- complex.

Hepatic changes following a high-fat diet: effects of Cornus mas and gold nanoparticles phytoreduced with Cornus mas on oxidative stress, inflammation, and histological damage.

Background and aims: High fat diet (HFD) can lead to liver injury, through oxidative stress and inflammation. The use of natural compounds with antioxidant and anti-inflammatory properties can have a protective potential. We aimed to investigate the effects of Cornus mas (CM) and gold nanoparticles phytoreduced with CM (GNPsCM) on hepatic alterations induced by HFD in rats. Methods: Female Sprague Dawley rats were randomly divided into four groups: control, HFD, HFD +CM and HFD + GNPsCM. The high fat diet was administered for 32 weeks and CM and GNPsCM were administered for 4 weeks after the HFD period. The high fat diet induced oxidative stress in liver, with lipid peroxidation and decreased antioxidant capacity, inflammation and minimal histological alterations. Results: The administration of CM and GNPsCM reduced lipid peroxidation produced by HFD and increased antioxidant potential in liver homogenates, while increasing inflammatory markers. Histological alterations were slightly improved by the intervention of compounds, and hyaluronic acid content of the liver without statistical significance as compared to HFD group. Conclusion: These findings support the potential of these treatments in addressing liver oxidative stress, mitigating liver damage induced by a high-fat diet. This investigation sheds light on the oxidative stress dynamics and histological alterations associated with high-fat diet-induced liver injury, contributing to our understanding of potential therapeutic interventions.

A case of pleural Mycobacterium tuberculosis infection with reversion of Quantiferon Gold Plus results from positive to negative.

Introduction. Mycobacterium tuberculosis (MTB) infections continue to have a high mortality and morbidity burden globally. Interferon-gamma release assays such as Quantiferon Gold Plus (QFG-Plus) aid in diagnosis of latent TB but diagnosis of pleural TB remains challenging. We present a case of active pleural MTB infection with reversion from positive to negative of IGRA result as well as negative Xpert MTB/RIF Ultra PCR result from tissues obtained from pleural biopsy. Case summary. A 52-year-old otherwise healthy male presented in August 2022 with a 2 week history of pleuritic chest pain associated with modest elevation in inflammatory markers. The patient had had a positive QFG-Plus result in 2018, however QFG-Plus during this admission was negative. Computed-tomography pulmonary angiogram and needle thoracocentesis showed an exudative left pleural effusion with predominant lymphocytes. The patient's symptoms failed to resolve with empiric antimicrobial therapy for community-acquired pneumonia. Broncho-alveolar lavage as well as biopsies of pleural tissues via video-assisted thoracoscopic surgery from the left lower lobe yielded negative results on routine microbiological culture as well as Xpert Ultra PCR. Growth of acid-fast bacilli was noted from mycobacterial cultures of pleural tissues which was identified as MTB. Conclusion. Despite significant technological advances, microbiological diagnosis of MTB infections remains challenging. We document QFG-Plus reversion during development from latent to active pleural TB. Decline in the ability of CD4+ and CD8+ T cells to produce interferon gamma in response to TB antigens (ESAT-6 and CFP-10) was likely associated with loss of host control of latent MTB. This case serves as a reminder that despite exhaustive testing with state-of-art diagnostic platforms, MTB infections can still elude discovery.

Doxorubicin-Loaded Ultrasmall Gold Nanoparticles (1.5 nm) for Brain Tumor Therapy and Assessment of Their Biodistribution.

Ultrasmall gold nanoparticles (1.5 nm) were covalently conjugated with doxorubicin (AuDox) and AlexaFluor647 (AuAF647) to assess their biodistribution and their efficiency toward brain tumors (glioblastoma). A thorough characterization by transmission electron microscopy, small-angle X-ray scattering, and differential centrifugal sedimentation confirmed their uniform ultrasmall nature which makes them very mobile in the body. Each nanoparticle carried either 13 doxorubicin molecules (AuDox) or 2.7 AlexaFluor-647 molecules (AuAF647). The firm attachment of the ligands to the nanoparticles was demonstrated by their resilience to extensive washing, followed by centrifugation. The particles easily entered mammalian cells (HeLa, T98-G, brain endothelial cells, and human astrocytes) due to their small size. The intravenously delivered fluorescing AuAF647 nanoparticles crossed the blood-brain barrier with ∼23% accumulation in the brain tumor in an orthotopic U87 brain tumor model in nude mice. This was confirmed by elemental analysis (gold; inductively coupled plasma optical emission spectroscopy) in various organs. The doxorubicin-loaded AuDox nanoparticles inhibited brain tumor growth and prolonged animal survival without adverse side effects. Most of the nanoparticles (84%) had been excreted from the animal after 24 h, indicating a high mobility in the body.

Green synthesis of silver and gold-doped zinc oxide nanocomposite with propolis extract for enhanced anticancer activity.

Metal and metal oxide nanocomposites have unique properties and are promising for antibacterial and anticancer applications. In this work, we aimed to highlight the relationship between the biosynthesis ways of silver and gold-doped zinc oxide nanocomposites and their functions as anticancer on cell lines (MCF-7 and HepG2). The propolis was used to biosynthesize four different nanoparticles with the same components, including zinc, gold and silver. The nanocomposites were characterized using various techniques, including ultraviolet-visible spectroscopy (UV-Vis), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Energy Dispersive X-ray analysis (EDX) and cytotoxicity assays. The result of this study showed that formed nanocomposites have a similar level of Zn, Au, and Ag, ranging from 23-34%, 2-6%, and 2-3%, respectively. In addition, adding the components simultaneously produces the fastest color change, and the fabricated nanoparticles have spherical shapes with different layers. In addition, the prepared nanoparticles influenced the cell viability of the cancer cell lines, with the most effective one when Zn, Au, and Ag were added spontaneously to form a nanocomposite called (All) with IC50 of 24.5 µg/mL for MCF7 cells and 29.1 µg/mL for HepG2 cells. Thus, the study illustrates that the preparation of nanocomposite generated through green synthesis with different methods significantly affects the structure and function and may improve the synthesis of nanocomposite to be developed into an efficacious therapeutic agent for cancers. In addition, this study opens the door toward a novel track in the field of nanocomposites as it links the synthesis with structure and function. Further anti-cancer properties, as well as animal testing are needed for those nanocomposites.

Assessment of heavy metal levels in cow's milk and associated health risks in the vicinity of the MIDROC Laga Dambi gold mine in Ethiopia.

INTRODUCTION: The possible health effects of consuming milk contaminated with heavy metals have been the subject of considerable concern worldwide. OBJECTIVE: The aim of this study was to determine the level of heavy metals in cow's milk in the vicinity of MIDROC Laga Dambi gold mine and to assess their possible health risks for consumers. METHODS: Nine composite samples were formed by aggregating 243 milk samples obtained in triplicates from 81 domestic milk-producing households. Inductively coupled plasma-optical emission spectroscopy was used to measure the amount of heavy metals after samples digestion under optimal conditions. RESULTS: The heavy metals concentrations obtained were 13.913-7.843, 9.505-3.589, 5.972-3.147, 2.288-1.851, 0.403-0.143, 0.436-0.128, 0.26-0.153, 0.143-0.048, 0.160-ND (not detected), and 0.140-ND mgkg-1for Fe, Zn, Pb, Mn, Hg, Cr, Cd, As, Ni, and Co, respectively. Of the heavy metals identified, the levels of Pb, As, Cd, and Hg exceeded the recommended value. Based on the estimated daily intake (EDI), the total health quotient (THQ) is higher than unity even for Pb alone. It has been found that the consumption of cow milk increases the health index (HI) by 2.972. Ninety five percent of the HI in the study area was explained by the toxic heavy metals (Pb, Cd, As, and Hg) in the cow milk, which were found to be beyond the safe limit. CONCLUSION: This demonstrates that there is a health risk to the population who consume cow's milk sourced from the vicinity of MIDROC Laga Dambi gold mine. To safeguard the public's health, we advised strict monitoring and legislative control for the safety of cow's milk originating from study area.

Diagnostic accuracy of QuantiFERON-TB Gold Plus with Chemiluminescence Immunoassay: a systematic review and meta-analysis.

INTRODUCTION: Tuberculosis (TB) remains a global health challenge, underscoring the need for accurate diagnosis, particularly for Latent TB Infection. This meta-analysis assesses the diagnostic performance of QuantiFERON-TB Gold Plus (QFT) using Enzyme-Linked Immunosorbent Assay (ELISA) with Chemiluminescence Immunoassay (CLIA). AREAS COVERED: We systematically reviewed studies comparing QFT-CLIA with QFT-ELISA for TB detection. The literature search was carried out on PubMed, Scopus, and Web of Science, covering publications up to September 15, 2023. We included studies that assessed sensitivity, specificity, positive and negative likelihood ratios (PLR and NLR), Diagnostic Odds Ratio (DOR), and concordance. EXPERT OPINION: QFT-CLIA demonstrated high sensitivity of 0.97 (95% CI: 0.95-0.99) and specificity of 0.99 (95% CI: 0.92-1.0), with PLR of 72.19 (95% CI: 11.25-463.17), NLR of 0.03 (95% CI: 0.02-0.05), and DOR of 2494.55 (95% CI: 301.67-20627.87). The overall agreement between QFT-CLIA and QFT-ELISA was strong (0.92, 95% CI: 0.88-0.97), although the agreement for indeterminate results was slightly lower (0.83, 95% CI: 0.70-0.96). The high diagnostic accuracy and broader quantitative range of QFT-CLIA compared to ELISA may lead to more positive results and better classification of borderline cases. However, further research is needed to validate its diagnostic capabilities.

Chitosan-thioglycolic acid composite cross-linked with glutaraldehyde for selective recovery of Au(III) ions from e-waste leachate via reduction-coupled adsorption and incineration.

The recovery of gold (Au) from electronic waste (e-waste) has gained significant attention due to its high Au content and economic feasibility compared to natural ores. This study presents a facile, single-step approach to prepare the chitosan-thioglycolic acid composite crosslinked with glutaraldehyde (CS-TGA-GA) and demonstrates its unique capability for precious metal management, which is a less investigated application area for thiolated chitosan materials. The novel cost-effective biosorbent CS-TGA-GA demonstrated a very high adsorption capacity of 1351.9 ± 96 mg/g and selectivity for Au(III) from an acidic e-waste solution at pH 1 and 298 K. The high adsorption capacity and selectivity of the sorbent can be attributed to the abundance of -NH2, -OH, and -SH groups present on its surface. Various characterizations, such as scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffractometry, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy, as well as sorption experiments, including pH, kinetic, and isotherm studies, were performed. The kinetic data align with a pseudo-second-order model and the isotherm data can be well expressed by the Freundlich model. The CS-TGA-GA composite effectively facilitated the conversion of Au(III) to Au(0), leading to the formation of Au nanoparticles that aggregated in the reaction vessel over time. Subsequently, the Au-loaded CS-TGA-GA underwent an incineration procedure, yielding recovered Au with a purity of 99.6%, as measured by X-ray fluorescence. In addition to its large uptake capacity, acid stability, and recyclability, the prepared sorbent showed a highly selective uptake of Au(III) ions in a solution containing various metal ions leached from waste printed circuit boards. These results highlight the potential of CS-TGA-GA as an adsorbent for the recovery of Au from e-waste leachate, thereby contributing to sustainable resource management.

Generalized Optical Binding for Multiple Assemblies of Nanoparticles under Multiple Laser Beams.

Optical forces enable noncontact manipulation of micro- and nanoscale objects, offering diverse applications. When a laser beam irradiates multiple nanoparticles in a solvent, it induces the formation of an ordered array with a finite distance between particles due to optical binding, which results from the optical force exerted by scattered light. This scattered light extends beyond the irradiation area, facilitating interactions between spatially separated nanoparticle assemblies under multiple laser beams. However, the extension of optical binding in this context remains underexplored. In this study, we propose a concept of generalized optical binding between particle assemblies using two focal laser beams. Under carefully designed conditions, the scattered light between assemblies leads the particles to stable positions and impedes rotational dynamics driven by the circular polarization of the lasers. We demonstrate the fusion and reordering of two hexagonal assemblies, offering a blueprint for creating on-demand particle arrays through laser beam manipulation.

Myco-nanotechnological approach to synthesize gold nanoparticles using a fungal endophyte, Penicillium oxalicum and unravelling their antibacterial activity and anti-breast cancer role via metabolic reprogramming.

The present study has been designed to fabricate fungal endophyte assisted gold nanoparticles and elucidate their anti-breast cancer potential. The aqueous extract of fungal endophyte, Penicillium oxalicum, associated with the medicinal plant Amoora rohituka has been used for the fabrication of gold nanoparticles (POAuNPs). The physicochemical characterization using UV-Vis spectroscopy, FTIR, XRD, DLS, Zeta potential, TEM and FESEM analysis revealed stable, uniform distribution, spherical-shape and crystalline nature of POAuNPs with size range of 3-46 nm. Further, POAuNPs potentially inhibited the growth of pathogenic bacterial strains, E. coli and S. aureus. The synthesized POAuNPs has shown potential antioxidant effects against DPPH, superoxide and nitric oxide radical scavenging assay with an EC50 value of 8.875±0.082, 52.593±2.506 and 43.717±1.449 µg/mL, respectively. Moreover, the value of EC50 for total antioxidant capacity of POAuNPs was found to be 23.667±1.361 µg/mL. The cell viability of human breast cancer cells, MDA-MB-231 and MCF-7 was found to be reduced after treatment with POAuNPs and IC50 values were found to be 19.753±0.640 and 35.035±0.439 µg/mL respectively. Further, in vitro biochemical assays revealed POAuNPs induced metabolic reprogramming in terms of reduced glucose uptake and increased LDH release and, disruption of oxidative balance through depletion of GSH level, increased nitric oxide level and lipid peroxidation as a possible pathway to suppress the human breast cancer cell proliferation. Apoptosis-specific nuclear modulations induced by POAuNPs in human breast cancer cells were validated through DAPI nuclear staining. The present investigation thus attempted to show first ever fabrication of gold nanoparticles using aqueous extract of P. oxalicum associated with A. rohituka. The results revealed unique physico-chemical characteristics of myogenic gold nanoparticles and screening their effect against breast cancer via metabolic reprogramming and induction of apoptosis thus adds great significance against cancer therapeutics, suggesting further exploration to develop nanotherapeutic drugs.

Unveiling the cytotoxicity of a new gold(I) complex towards hepatocellular carcinoma by inhibiting TrxR activity.

Hepatocellular carcinoma (HCC), the predominant type of liver cancer, is an aggressive malignancy with limited therapeutic options. In this study, we assess a collection of newly designed gold(I) phosphine complexes. Remarkably, the compound GC002 exhibits the greatest toxicity to HCC cells and outperforms established medications, such as sorafenib and auranofin, in terms of antitumor efficacy. GC002 triggers irreversible necroptosis in HCC cells by increasing the intracellular accumulation of reactive oxygen species (ROS). Mechanistically, GC002 significantly suppresses the activity of thioredoxin reductase (TrxR), which plays a crucial role in regulating redox homeostasis and is often overexpressed in HCC by binding directly to the enzyme. Our in vivo xenograft study confirms that GC002 possesses remarkable antitumor activity against HCC without severe side effects. These findings not only highlight the novel mechanism of controlling necroptosis via TrxR and ROS but also identify GC002 as a promising candidate for the further development of antitumor agents targeting HCC.

Targeting superficial cancers with gold nanoparticles: a review of current research.

Superficial cancers typically refer to cancers confined to the surface layers of tissue. Low-targeting therapies or side effects prompt exploration of novel therapeutic approaches. Gold nanoparticles (AuNPs), due to their unique optical properties, serve as effective photosensitizers, enabling tumor ablation through photothermal therapy (PTT). PTT induced by AuNPs can be achieved through light sources externally applied to the skin. Near-infrared radiation is the main light candidate due to its deep tissue penetration capability. This review explores recent advancements in AuNP-based PTT for superficial cancers, specifically breast, head and neck, thyroid, bladder and prostate cancers. Additionally, challenges and future directions in utilizing AuNPs for cancer treatment are discussed, emphasizing the importance of balancing efficacy with safety in clinical applications.

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Superior Single-Entity Electrochemistry Performance of Capping Agent-Free Gold Nanoparticles Compared to Citrate-Capped Gold Nanoparticles.

In observing the electrocatalytic current of nanoparticles (NPs) using single-entity electrochemistry (SEE), the surface state of the NPs significantly influences the SEE signal. This study investigates the influence of capping agents on the electrocatalytic properties of gold (Au) NPs using SEE. Two inner-sphere reactions, hydrazine oxidation and glucose oxidation, were chosen to explore the SEE characteristics of Au NPs based on the capping agent presence. The results revealed that "capping agent-free" Au NPs exhibited signal magnitudes and frequencies consistent with theoretical expectations, indicating superior stability and catalytic performance in electrolyte solutions. In contrast, citrate-capped Au NPs showed signals varying depending on the applied potential, with larger magnitudes and lower frequencies than expected, likely due to an aggregation of NPs. This study suggests that capping agents play a crucial role in the catalytic performance and stability of Au NPs in SEE. By demonstrating that minimizing capping agent presence can enhance effectiveness in SEE, it provides insights into the future applications of NPs, particularly highlighting their potential as nanocatalysts in energy conversion reactions and environmental applications.

Controlling Gold-Assisted Exfoliation of Large-Area MoS2 Monolayers with External Pressure.

Gold-assisted exfoliation can fabricate centimeter- or larger-sized monolayers of van der Waals (vdW) semiconductors, which is desirable for their applications in electronic and optoelectronic devices. However, there is still a lack of control over the exfoliation processes and a limited understanding of the atomic-scale mechanisms. Here, we tune the MoS2-Au interface using controlled external pressure and reveal two atomic-scale prerequisites for successfully producing large-area monolayers of MoS2. The first is the formation of strong MoS2-Au interactions to anchor the top MoS2 monolayer to the Au surface. The second is the integrity of the covalent network of the monolayer, as the majority of the monolayer is non-anchored and relies on the covalent network to be exfoliated from the bulk MoS2. Applying pressure or using smoother Au films increases the MoS2-Au interaction, but may cause the covalent network of the MoS2 monolayer to break due to excessive lateral strain, resulting in nearly zero exfoliation yield. Scanning tunneling microscopy measurements of the MoS2 monolayer-covered Au show that even the smallest atomic-scale imperfections can disrupt the MoS2-Au interaction. These findings can be used to develop new strategies for fabricating vdW monolayers through metal-assisted exfoliation, such as in cases involving patterned or non-uniform surfaces.

Dr. Carolyn Meltzer: Pioneer, innovator, mentor, and 2023 ACR Gold Medal winner.

Dr. Carolyn Meltzer is an extraordinary radiologist, researcher, mentor, and distinguished leader who deserves recognition for her immense impact on the discipline of radiology. This article serves to acknowledge and celebrate Dr. Meltzer for winning the 2023 American College of Radiology (ACR) Gold Medal. The ACR Gold Medal award is the highest honor awarded to distinguished radiologists with exceptional contributions to the field, and Dr. Meltzer is no exception. She is the 14th woman to win this prestigious award, compared to 191 male winners, although it began as an annual tradition in 1927. Throughout this piece, Dr. Meltzer discusses her journey to where she is today as the dean of Keck School of Medicine at USC, the guidance and development that lead her to this point and provides sound advice for those who seek to follow in her footsteps as a leader and mentor committed to seeking ways to advance and contribute immensely to the field of radiology.

Loading Lewis Acid/Base Pair on Metal Nanocluster for Catalytic Ugi Reaction.

Constructing structurally robust and catalytically active metal nanoclusters for catalyzing multi-component reactions is an interesting while challenging task. Inspired by Lewis acid and Lewis base catalysis, we realized the combination of both Lewis acid and Lewis base sites on the surface of a stable gold nanocluster Au35Cd2. The catalytic potential of Au35Cd2 in four-component Ugi reaction was explored, demonstrating high activity and exceptional recyclability. In-depth mechanism studies indicate that the catalytic synergy of the Lewis acid/base pair is crucial for the high efficiency of Au35Cd2-catalyzed Ugi reaction. Bearing the stable structure, multiple activation sites and hierarchical chirality, Au35Cd2 is expected to display further interesting catalytic performance such as asymmetric catalysis.

Diagnosing fungal infections in clinical practice: a narrative review.

BACKGROUND: Invasive fungal infections (IFI) present a major medical challenge, with an estimated 6.5 million cases annually, resulting in 3.8 million deaths. Pathogens such as Aspergillus spp. Candida spp. Mucorales spp. Cryptococcus spp. and other fungi species contribute to these infections, posing risks to immunocompromised individuals. Early and accurate diagnosis is crucial for effective treatment and better patient outcomes. AREAS COVERED: This narrative review provides an overview of the current methods and challenges associated with diagnosing fungal diseases, including invasive aspergillosis and invasive candidiasis, as well as rare and endemic fungal infections. Various diagnostic techniques, including microscopy, culture, molecular diagnostics, and serological tests, are reviewed, highlighting their respective advantages and limitations and role in clinical guidelines. To illustrate, the need for improved diagnostic strategies to overcome existing challenges, such as the low sensitivity and specificity of current tests and the time-consuming nature of traditional culture-based methods, is addressed. EXPERT OPINION: Current advancements in fungal infection diagnostics have significant implications for healthcare outcomes. Improved strategies like molecular testing and antigen detection promise early detection of fungal pathogens, enhancing patient management. Challenges include global access to advanced technologies and the need for standardized, user-friendly point-of-care diagnostics to improve diagnosis of fungal infections globally.

Gold Nanoparticles for Retinal Molecular Optical Imaging.

The incorporation of gold nanoparticles (GNPs) into retinal imaging signifies a notable advancement in ophthalmology, offering improved accuracy in diagnosis and patient outcomes. This review explores the synthesis and unique properties of GNPs, highlighting their adjustable surface plasmon resonance, biocompatibility, and excellent optical absorption and scattering abilities. These features make GNPs advantageous contrast agents, enhancing the precision and quality of various imaging modalities, including photoacoustic imaging, optical coherence tomography, and fluorescence imaging. This paper analyzes the unique properties and corresponding mechanisms based on the morphological features of GNPs, highlighting the potential of GNPs in retinal disease diagnosis and management. Given the limitations currently encountered in clinical applications of GNPs, the approaches and strategies to overcome these limitations are also discussed. These findings suggest that the properties and efficacy of GNPs have innovative applications in retinal disease imaging.

Microdosimetric Simulation of Gold-Nanoparticle-Enhanced Radiotherapy.

Conventional X-ray therapy (XRT) is commonly applied to suppress cancerous tumors; however, it often inflicts collateral damage to nearby healthy tissue. In order to provide a better conformity of the dose distribution in the irradiated tumor, proton therapy (PT) is increasingly being used to treat solid tumors. Furthermore, radiosensitization with gold nanoparticles (GNPs) has been extensively studied to increase the therapeutic ratio. The mechanism of radiosensitization is assumed to be connected to an enhancement of the absorbed dose due to huge photoelectric cross-sections with gold. Nevertheless, numerous theoretical studies, mostly based on Monte Carlo (MC) simulations, did not provide a consistent and thorough picture of dose enhancement and, therefore, the radiosensitization effect. Radiosensitization by nanoparticles in PT is even less studied than in XRT. Therefore, we investigate the physics picture of GNP-enhanced RT using an MC simulation with Geant4 equipped with the most recent physics models, taking into account a wide range of physics processes relevant for realistic PT and XRT. Namely, we measured dose enhancement factors in the vicinity of GNP, with diameters ranging from 10 nm to 80 nm. The dose enhancement in the vicinity of GNP reaches high values for XRT, while it is very modest for PT. The macroscopic dose enhancement factors for realistic therapeutic GNP concentrations are rather low for all RT scenarios; therefore, other physico-chemical and biological mechanisms should be additionally invoked for an explanation of the radiosensitization effect observed in many experiments.