Hydroxide assisted synthesis of monodisperse and biocompatible gold nanoparticles with dextran

Judd-Ofelt analysis and photoluminescence behavior of Tb3+-activated K7SrY2(B5O10)3 phosphors modified with alkali co-dopants for solid-state lighting applications

In this study, the structural and luminescent properties of alkali-modified K7SrY2(B5O10)3 phosphors activated with Tb3+ ions were systematically investigated for solid-state lighting and photonic applications. A combination of X-ray diffraction (XRD) with Rietveld refinement, vibrational spectroscopy (FTIR and Raman), and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) confirmed that the trigonal R32 structure of the host lattice is retained upon doping and co-doping, with Tb3+ ions preferentially occupying Y3+ sites. Photoluminescence (PL) studies revealed intense green emission centered at 540 nm (5D4 → 7F5 transition), with maximum intensity observed at 3 wt% Tb3+, beyond which concentration quenching occurred. The critical interaction distance (∼28 Å) and interaction parameter (θ ≈ 5.55) confirmed that dipole-dipole interactions govern the quenching mechanism. Co-doping with Li+ and Na+ resulted in a significant enhancement in both emission intensity and decay lifetime, with Li+ co-doping at 3 wt% yielding an ∼11.7-fold enhancement and increasing the average lifetime from 1.48 ms to 1.95 ms. This corresponds to a high radiative efficiency of ∼93 %, indicating effective suppression of non-radiative losses. These enhancements were attributed to improved crystallinity, suppression of non-radiative defects, and modulation of the local crystal field symmetry. Judd-Ofelt analysis of the well-resolved emission bands yielded Ω4 and Ω6 intensity parameters of 0.96 × 10-20 and 1.12 × 10-20 cm2, respectively, indicating moderate asymmetry in the ligand environment. The theoretical radiative lifetime (∼1.10 ms) showed excellent agreement with experimental values, indicating high radiative efficiency with minimal non-radiative losses. CIE chromaticity coordinates reached (0.3782, 0.6081) for 3 wt% Tb3+ and shifted toward the blue-green region (e.g., (0.2791, 0.4284) with Li+), demonstrating tunable and stable green emission. This work demonstrates the potential of Li+/Na+ co-doped KSYBO:Tb3+ phosphors as efficient, color-stable, and structurally robust green-emitting components for phosphor-converted white LED and optical display devices.

A dual-functional nanogold tablet as a plasmonic and nanozyme sensor for point-of-care applications

Point-of-care (POC) devices provide on-site disease diagnosis, particularly in resource-limited settings. Despite considerable progress in POC testing, the availability of commercial devices remains limited, primarily due to challenges in detection sensitivity and portability. Furthermore, advancements in existing POC devices are essential to better meet the needs of end-users. Herein, we present a colorimetric dual-functional tablet sensor using dextran-gold nanoparticles (dAuNPs) to detect and quantify uric acid and glucose levels in urine. Our tablet sensor combines the plasmonic and nanozyme properties of dAuNPs, resulting in highly sensitive detection of both biomarkers. Interestingly, we fabricated the nanogold tablet directly from the dAuNP solution without the addition of any external stabilizer or tablet-forming reagent, thus naming it a direct tablet. An enzyme-free approach was employed for uric acid detection, providing a wide detection range of 0.00187-7.8 mM and a low detection limit of 0.0037 mM, attributed to the hydrogen bonding between dextran and uric acid. On the other hand, the unique nanozyme properties of dAuNPs exhibited exclusive POx-mimetic activity for glucose detection (K m = 0.106 mM and V max = 369.72 mM min-1), with a lower detection limit of 0.625 mM. Our dual-functional tablet offers exceptional substrate selectivity for the colorimetric-chromogenic assay of both uric acid and glucose. This dual-functionality not only provides a highly sensitive, selective, and cost-effective detection strategy for resource-limited settings but also introduces a new avenue for designing customizable plasmonic-nanozyme nanogold tablet sensors as a powerful tool for rapid diagnosis.

Preparation and characterization of dextran-modified ZnO and Cu-doped ZnO nanohybrid material for enhanced antimicrobial delivery and activity

Zinc oxide (ZnO) nanoparticles are widely used in various applications, particularly in antimicrobial products. Efforts to enhance their performance and efficacy, including copper (Cu) doping and incorporating natural polymers. In this study, dextran-modified ZnO and Cu-doped ZnO nanohybrids were synthesized and characterized using exodextran isolated from Leuconostoc mesenteroides TISTR 473. Characterization results showed that dextran binds to the surface of ZnO particles through CO⋯Zn and C-OH⋯O interactions, particularly at oxygen vacancy sites. The incorporation of dextran improved the antibacterial efficacy of ZnO and Cu-doped ZnO nanoparticles against bacteria related to fruit and vegetable spoilage, including gram-positive Bacillus altitudinis and gram-negative Achromobacter mucicolens. These findings highlight the potential of dextran-modified ZnO nanomaterials in enhancing antimicrobial activity and biocompatibility for biomedical applications, as well as their use in food packaging to extend shelf life.

Exploiting the Tunneling Coffee Ring Effect of Universal Colorimetric Nanomaterials for Ultrafast On-Site Microbial Monitoring

The coffee-ring effect is an eye-catching circle originating from a material-suspended liquid droplet at a solid substrate after liquid evaporation, but the low speediness has restricted practical applications. When nanomaterial aqueous solutions are dropped onto porous nitrocellulose (NC), the liquid is immediately absorbed through the porous tunnels of paper fibers, and nanomaterials are rapidly enriched on the contact lines between droplets and membranes. We called this ultrafast variant of the coffee ring effect the "tunneling coffee ring" (TCR). When nanomaterial sizes are smaller than that of pores, a larger-diameter ring of nanomaterials quickly materializes. The real-time particle size-dependent TCRs and liquid diffusion rings exhibit a dual-ring pattern on the NC membrane. The tunneling speed of the capillary effect is so fast that the pattern appears within seconds. We apply the TCR effect as a size-surface affinity-particle/fluid separation sensor for bacteria. Dextran-modified Au and MoS2 nanostructures are proposed to be antibody-free microbe kits. Our TCR effect is used to distinguish between particles of different sizes and affinities, which are highly relevant in complicated systems without electricity and equipment in resource-poor settings.

HAuCl4-mediated green synthesis of highly stable Au NPs from natural active polysaccharides: Synthetic mechanism and antioxidant property

Polysaccharide-functionalized gold nanoparticles (Polysaccharide-Au NPs) with high stability were successfully prepared by a straightforward method. Notably, the Au (III) ion acts as a strong Lewis acid to facilitate glycosidic bond breaking. Subsequently, the polysaccharide conformation was transformed to an open-chain form, exposing highly reduced aldehyde or ketone groups that reduce Au (III) to Au (0) crystal species, further growing into Au NPs. As-prepared Au NPs displayed excellent stability over a longer storage period (more than 70 days), a wide range of temperatures (25-60 °C), and pH range (3-11), varying concentrations (0-200 mM) and types of salt ions (Na+, K+, Ca2+, Mg2+), and glutathione solutions (5 mM). More interestingly, polysaccharide-Au NPs retained the antioxidant activity of polysaccharides and reduced oxidative damage at the cellular level through decreased reactive oxygen species (ROS) production. The intracellular levels of ROS pretreated with polysaccharide and polysaccharide-Au NPs were decreased 53.12-75.85 % compared to the H2O2 group, respectively. Therefore, the green synthesized Au NPs from natural active polysaccharides exhibit potential applications in biomedical fields.

Tailoring plasmonic sensing strategies for the rapid and sensitive detection of hypochlorite in swimming water samples

A tunable plasmonic sensor has been developed by varying the dextran content in the initially synthesized dextran-gold nanoparticle (dAuNPs) solution. A colloidal nanogold solution (dAuNPs-Sol) was initially prepared using dextran and gold salt in alkaline media by a one-pot green synthetic route. The dAuNPs-Sol was combined with varying amounts of dextran (ranging from 0.01 to 30.01%) to create a tunable probe, along with different solid formats, including tablet (dAuNPs-Tab), powder (dAuNPs-Powder), and composite (dAuNPs-Comp). Both the liquid and solid phase plasmonic probes were characterized using UV-vis spectroscopy, transmission electron microscopy (TEM) dynamic light scattering (DLS), and zeta potential analysis. The impact of dextran content in the dAuNP solution is studied in terms of surface charge and hydrodynamic size. The influence of operational treatments used to achieve solid dAuNPs probes is also explored. All plasmonic probes were employed to detect a broad range of OCl¯ concentrations (ranging from µM to mM) in water through aggregation followed by calculating a lower and upper limit of detection (LLoD, ULoD) of the proposed colorimetric sensors. Results indicate that the most sensitive detection is achieved with a lower dextran content (0.01%), which exhibits an LLoD of 50 µM. The dAuNPs-Sol sensor is selective and demonstrates real-world applicability, as confirmed by interference analysis and successful testing with various water samples. Additionally, it is found that a 20 × concentration of dextran-coated gold nanoparticles could be attained without any changes in the particle morphology. This concentration is achieved through a straightforward process that does not require the use of a centrifuge machine. This finding highlights the practicality and simplicity of the method, indicating its potential for scalable and cost-effective production of concentrated dAuNPs without compromising their structural integrity.

A general one-pot, solvent-free solid-state synthesis of biocompatible metal nanoparticles using dextran as a tool: Evaluation of their catalytic and anti-cancer activities

We propose a general green method coupled with a solid-state vibration ball milling strategy for the synthesis of various metal nanoparticles (MNPs), employing a polymeric carbohydrate dextran (Dx) as a reducing and stabilizing molecule. The synthesis of size-controlled Dx-based MNPs (Dx@MNPs), featuring comparatively narrow size distributions, was achieved by controlling the mass ratio of the reactants, reaction time, frequency of the vibration ball mill, and molecular weight of Dx. Notably, this process was conducted at ambient temperatures, without the aid of solvents and accelerating agents, such as NaOH, and conventional reductants as well as stabilizers. Thermal properties of the resulting Dx@MNPs nanocomposites were extensively investigated, highlighting the influence of metal precursors and reaction conditions. Furthermore, the catalytic activity of synthesized nanocomposites was evaluated through the reduction reaction of 4-nitrophenol, exhibiting great catalytic performance. In addition, we demonstrated the excellent biocompatibility of the as-prepared Dx@MNPs toward human embryonic kidney (HEK-293) cells, revealing their potential for anticancer activities. This novel green method for synthesizing biocompatible MNPs with Dx expands the horizons of carbohydrate-based materials as well as MNP nanocomposites for large-scale synthesis and controlled size distribution for various industrial and biomedical applications.

Peptide-Hydrogel Nanocomposites for Anti-Cancer Drug Delivery

Cancer is the second leading cause of death globally, but conventional anticancer drugs have side effects, mainly due to their non-specific distribution in the body in both cancerous and healthy cells. To address this relevant issue and improve the efficiency of anticancer drugs, increasing attention is being devoted to hydrogel drug-delivery systems for different kinds of cancer treatment due to their high biocompatibility and stability, low side effects, and ease of modifications. To improve the therapeutic efficiency and provide multi-functionality, different types of nanoparticles (NPs) can be incorporated within the hydrogels to form smart hydrogel nanocomposites, benefiting the advantages of both counterparts and suitable for advanced anticancer applications. Despite many papers on non-peptide hydrogel nanocomposites, there is limited knowledge about peptide-based nanocomposites, specifically in anti-cancer drug delivery. The aim of this short but comprehensive review is, therefore, to focus attention on the synergies resulting from the combination of NPs with peptide-based hydrogels. This review, which includes a survey of recent advances in this kind of material, does not aim to be an exhaustive review of hydrogel technology, but it instead highlights recent noteworthy publications and discusses novel perspectives to provide valuable insights into the promising synergic combination of peptide hydrogels and NPs for the design of novel anticancer drug delivery systems.

Polysaccharide-based gold nanomaterials: Synthesis mechanism, polysaccharide structure-effect, and anticancer activity

Polysaccharide-based gold nanomaterials have attracted great interest in biomedical fields such as cancer therapy and immunomodulation due to their prolonged residence time in vivo and enhanced immune response. This review aims to provide an up-to-date and comprehensive summary of polysaccharide-based Au NMs synthesis, including mechanisms, polysaccharide structure-effects, and anticancer activity. Firstly, research progress on the synthesis mechanism of polysaccharide-based Au NMs was addressed, which included three types based on the variety of polysaccharides and reaction environment: breaking of glycosidic bonds via Au (III) or base-mediated production of highly reduced intermediates, reduction of free hydroxyl groups in polysaccharide molecules, and reduction of free amino groups in polysaccharide molecules. Then, the potential effects of polysaccharide structure characteristics (molecular weight, composition of monosaccharides, functional groups, glycosidic bonds, and chain conformation) and reaction conditions (the reaction temperature, reaction time, pH, concentration of gold precursor and polysaccharides) on the size and shape of Au NMs were explored. Finally, the current status of polysaccharide-based Au NMs cancer therapy was summarized before reaching our conclusions and perspectives.

P-Y/G@NHs sensitizes non-small cell lung cancer cells to radiotherapy via blockage of the PI3K/AKT signaling pathway

Radioresistance represents a common phenomenon found in cancer treatment. Herein, the current study sought to evaluate the effects of a nanodrug delivery system of YSAYPDSVPMMS (YSA) peptide-modified gold nanoparticles-dextran-based hydrogel loaded with paclitaxel-succinic anhydride (P-Y/G@NHs) on non-small cell lung cancer (NSCLC) cell radiosensitivity. Firstly, utilizing the coupling reaction and layer-by-layer assembly technique, P-Y/G@NHs was prepared. The therapeutic effects of the P-Y/G@NHs in NSCLC cells in relation to the PI3K/AKT signaling pathway were examined by assessing the colony formation, apoptosis, and reactive oxygen species (ROS) generation of A549 cells under 10 Gy X-rays irradiation. Moreover, A549 tumor-bearing mice were generated to further validate the therapeutic effect in vivo. We confirmed the successful conjugation of the nanocomposite. Under 10 Gy X-rays irradiation, P-Y/G@NHs reduced the number of colonies of A549 cells, while inducing both cell apoptosis and ROS production. Moreover, P-Y/G@NHs enhanced the radiosensitivity of A549 cells by inhibiting the PI3K/AKT signaling pathway. In vivo fluorescence experiments validated that P-Y/G@NHs effectively-targeted and accumulated at the tumor site in nude mice, thus augmenting the radiosensitivity of tumors without significant immune toxicity or side effects. Conclusively, our findings highlighted that P-Y/G@NHs significantly enhanced the radiosensitivity of NSCLC cells by repressing the PI3K/AKT signaling pathway.

Substrate-Free Fabrication of Single-Crystal Two-Dimensional Gold Nanoplates for Catalytic Application

Two-dimensional (2D) gold nanoplates (AuNPLs) have shown potential in catalysis, photonics, electronics, sensing, and biomedicine fields due to their high aspect ratio, fascinating surface chemistry, and quantum-size effect. Therefore, the synthesis of substrate-free, size-controlled single-crystal gold (Au) nanoplates is highly desirable for the development of catalysis and optical near-field enhancement applications. EDTA and hydroxide anions were used in this study to stimulate the formation of microscale single-crystal gold nanoplates under hydrothermal conditions. The reaction temperature, amount of EDTA, and hydroxyl anions all have a significant effect on the morphologies and size distributions of the gold nanoplates. The gold nanoplates had an average side length of between 3 and 11 μm. The application of the microscale single-crystal gold nanoplates as a nanocatalyst proved their excellent catalytic activity and recyclability for the catalysis of 4-nitrophenol to 4-aminophenol, implying that the large-size gold nanoplates were promising in heterogeneous catalysis applications.

Gold Tablets: Gold Nanoparticles Encapsulated into Dextran Tablets and Their pH-Responsive Behavior as an Easy-to-Use Platform for Multipurpose Applications

Many applications using gold nanoparticles (AuNPs) require (i) their functionalization with a biopolymer to increase their stability and (ii) their transformation into an easy-to-handle material, which provide them with specific properties. In this research, a portable tablet platform is presented based on dextran-encapsulated gold nanoparticles (AuNPs-dTab) by a ligand exchange reaction between citrate-capped gold nanoparticles (AuNPs-Cit) and dextran. These newly fabricated tablets were characterized utilizing ultraviolet-visible spectroscopy (UV-vis), Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR), transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction spectroscopy (XRD), differential scanning calorimetry (DSC), and atomic force microscopy (AFM) techniques. The results showed that dextran-capped gold nanoparticles in a tablet platform (AuNPs-dTab) were well-dispersed and highly stable for at least a year at room temperature. In addition to particle and surface characterization of AuNPs-dTab, the tablet morphology in terms of thickness, diameter, density, and opacity was also measured using 6 and 10% dextran with 2, 4 and 8 nM AuNPs-Cit. We further investigated the pH-responsive behavior of AuNPs-dTab in the presence and absence of sodium chloride. Results showed that neutral and alkaline environments were suitable to render AuNPs dispersed in a tablet, while an acidic condition controls the aggregation rate of AuNPs as confirmed by concentration-dependent aggregation phenomena. Besides the easy fabrication, these tablets were portable and low-cost (approx. 1.22 CAD per 100 tablets of a 100 μL solution of dextran-capped gold nanoparticles (AuNPs-dSol)). The biocompatible nature of dextran along with the acidic medium trigger nature of AuNPs makes our proposed tablet a potential candidate for cancer therapy due to the acidic surrounding of tumor tissues as compared to normal cells. Also, our proposed tablet approach paves the way for the fabrication of portable and easy-to-use optical sensors based on the AuNPs embedded in a natural polymeric architecture that would serve as a colorimetric recognition indicator for detecting analytes of interest.

Interactive Effects of Biosynthesized Nanocomposites and Their Antimicrobial and Cytotoxic Potentials

The present study investigated the biosynthesis of silver (AgNPs), zinc oxide (ZnONPs) and titanium dioxide (TiO2NPs) nanoparticles using Aspergillusoryzae, Aspergillusterreus and Fusariumoxysporum. Nanocomposites (NCs) were successfully synthesized by mixing nanoparticles using a Sonic Vibra-Cell VC/VCX processor. A number of analytical techniques were used to characterize the synthesized biological metal nanoparticles. Several experiments tested biologically synthesized metal nanoparticles and nanocomposites against two types of human pathogenic bacteria, including Gram-positive Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA), and Gram-negative Escherichia coli and Pseudomonasaeruginosa. Additionally, the antitumor activity in HCT-116 cells (colonic carcinoma) was also evaluated. Significant antimicrobial effects of various synthesized forms of nanoparticles and nanocomposites against E. coli and P. aeruginosa bacteria were detected. Various synthesized biogenic forms of nanoparticles and nanocomposite (9.0 to 29 mm in diameter) had high antibacterial activity and high antitumor activity against HCT-116 cells (colonic carcinoma) with IC50 values of 0.7-100 µg/mL. Biosynthesized NPs are considered an alternative to large-scale biosynthesized metallic nanoparticles and nanocomposites, are simple and cost effective, and provide stable nanomaterials.

Understanding the influence of experimental factors on bio-interactions of nanoparticles: Towards improving correlation between in vitro and in vivo studies

Bionanotechnology has developed rapidly over the past two decades, owing to the extensive and versatile, functionalities and applicability of nanoparticles (NPs). Fifty-one nanomedicines have been approved by FDA since 1995, out of the many NPs based formulations developed to date. The general conformation of NPs consists of a core with ligands coating their surface, that stabilizes them and provides them with added functionalities. The physicochemical properties, especially the surface composition of NPs influence their bio-interactions to a large extent. This review discusses recent studies that help understand the nano-bio interactions of iron oxide and gold NPs with different surface compositions. We discuss the influence of the experimental factors on the outcome of the studies and, thus, the importance of standardization in the field of nanotechnology. Recent studies suggest that with careful selection of experimental parameters, it is possible to improve the positive correlation between in vitro and in vivo studies. This provides a fundamental understanding of the NPs which helps in assessing their potential toxic side effects and may aid in manipulating them further to improve their biocompatibility and biosafety.

Multifunctionality of gold nanoparticles: Plausible and convincing properties

In a couple of decades, nanotechnology has become a trending area in science due to it covers all subject that combines diverse range of fields including but not limited to chemistry, physics and medicine. Various metal and metal oxide nanomaterials have been developed for wide range applications. However, the application of gold nanostructures and nanoparticles has been received more attention in various biomedical applications. The unique property of gold nanoparticles (AuNPs) is surface plasmon resonance (SPR) that determine the size, shape and stability. The wide surface area of AuNPs eases the proteins, peptides, oligonucleotides, and many other compounds to tether and enhance the biological activity of AuNPs. AuNPs have multifunctionality including antimicrobial, anticancer, drug and gene delivery, sensing applications and imaging. This state-of-the-art review is focused on the role of unique properties of AuNPs in multifunctionality and its various applications.

Seed-Mediated Electroless Deposition of Gold Nanoparticles for Highly Uniform and Efficient SERS Enhancement

A seed-mediated electroless deposition (SMED) approach for fabrication of large-area and uniform gold nanoparticle films as efficient and reproducible as surface-enhanced Raman scattering (SERS) substrates was presented. This approach involved a seeding pretreatment procedure and a subsequent growth step. The former referred to activation of polylysine-coated glass slides in gold seed solution, and the latter required a careful control of the reactant concentration and reaction time. With the aid of gold seeds and appropriate reaction conditions, a large-area and uniform nanofilm with evenly distributed gold nanoparticles (Au NPs) was formed on the surface of the substrates after adding a mixed solution containing ascorbic acid and trisodium citrate. The morphology of the Au nanofilm was examined by scanning electron microscopy. The size evolution of Au NPs on the surface of the substrates was analyzed in detail. The nanofilm substrate was prepared by reaction conditions of the seeded activation process: 10 mL ascorbic acid and trisodium citrate mixture and 30 min of soaking time, which exhibited an excellent uniformity and reproducibility of SERS enhancement with relative standard deviation (RSD) values of less than 8% (particularly, a RSD value of 3% can be reached for the optimized measurement). Compared to the common electroless deposition, the seed-mediated electroless deposition possessed inherent advantages in controllability, reproducibility, and economic benefit.