Advanced dendritic glucan-derived biomaterials: From molecular structure to versatile applications

There is considerable interest in the development of advanced biomaterials with improved or novel functionality for diversified applications. Dendritic glucans, such as phytoglycogen and glycogen, are abundant biomaterials with highly branched three-dimensional globular architectures, which endow them with unique structural and functional attributes, including small size, large specific surface area, high water solubility, low viscosity, high water retention, and the availability of numerous modifiable surface groups. Dendritic glucans can be synthesized by in vivo biocatalysis reactions using glucosyl-1-phosphate as a substrate, which can be obtained from plant, animal, or microbial sources. They can also be synthesized by in vitro methods using sucrose or starch as a substrate, which may be more suitable for large-scale industrial production. The large numbers of hydroxyl groups on the surfaces of dendritic glucan provide a platform for diverse derivatizations, including nonreducing end, hydroxyl functionalization, molecular degradation, and conjugation modifications. Due to their unique physicochemical and functional attributes, dendritic glucans have been widely applied in the food, pharmaceutical, biomedical, cosmetic, and chemical industries. For instance, they have been used as delivery systems, adsorbents, tissue engineering scaffolds, biosensors, and bioelectronic components. This article reviews progress in the design, synthesis, and application of dendritic glucans over the past several decades.

Gold nanoparticles synthesis and immobilization by atmospheric pressure DBD plasma torch method

Herein, we report the impact of plasma on gold nanoparticles synthesis. We used an atmospheric plasma torch fed with an aerosolized tetrachloroauric(iii) acid trihydrate (HAuCl₄·3H₂O) solution. The investigation showed that using pure ethanol as a solvent for the gold precursor enabled a better dispersion compared to a water-containing solution. We demonstrated here that the deposition parameters are easy to control, presenting the influence of solvent concentration and deposition time. The advantage of our method is that no capping agent was used. We assume that plasma creates a carbon-based matrix around the gold nanoparticles preventing them to agglomerate. The XPS results revealed the impact of using plasma. Metallic gold was detected in the plasma-treated sample, whereas the no-plasma sample revealed only Au(i) and Au(iii) contributions originating from the HAuCl₄ precursor. Detailed HRTEM, EDS mapping, and SAED analyses led to more insights into the structure.

Electropotential-Inspired Star-Shaped Gold Nanoconfined Multiwalled Carbon Nanotubes: A Proof-of-Concept Electrosensoring Interface for Lung Metastasis Biomarkers

Herein, an innovative way of designing a star-shaped gold nanoconfined multiwalled carbon nanotube-engineered sensoring interface (AuNS@MWCNT//GCE) is demonstrated for quantification of methionine (MTH); a proof of concept for lung metastasis. The customization of the AuNS@MWCNT is assisted by surface electrochemistry and thoroughly discussed using state-of-the-art analytical advances. Micrograph analysis proves the protrusion of nanotips on the surface of potentiostatically synthesized AuNPs and validates the hypothesis of Turkevich seed (AuNP)-mediated formation of AuNSs. In addition, a facile synthesis of electropotential-assisted transformation of MWCNTs to luminescent nitrogen-doped graphene quantum dots (N_d-GQDs avg. ∼4.3 nm) is unveiled. The sensor elucidates two dynamic responses as a function of C_MTH ranging from 2 to 250 μM and from 250 to 3000 μM with a detection limit (DL) of ∼0.20 μM, and is robust to interferents except for tiny response of a similar -SH group bearing Cys (<9.00%). The high sensitivity (0.44 μA·μM^-1·cm^-2) and selectivity of the sensor can be attributed to the strong hybridization of the Au nanoparticle with the sp² C atom of the MWCNTs, which makes them a powerful electron acceptor for Au-SH-MTH interaction as evidenced by density functional theory (DFT) calculations. The validation of the acceptable recovery of MTH in real serum and pharma samples by standard McCarthy-Sullivan assay reveals the holding of great promise to provide valuable information for early diagnosis as well as assessing the therapeutic consequence of lung metastasis.

Spectrofluorometric method for detection glycogen using chemically gold nanoparticles: Cyanobacteria as biological model

There is a need for simple spectrofluorimetric method for detection of glycogen molecule based on binding to nanogold. Here we propose such a quantification method for glycogen using cyanobacteria as a biological model. Biologically, two strains of cyanobacteria were selected based on their previously tested nanogold biosynthetic abilities. Chemically, spherical gold nanoparticles were prepared and tested for binding to the glycogen molecule. Experimental analyses were conducted to determine the morphological and optical properties of the Au-glycogen hydrocolloids. Results: The plasmon band of biosynthesized AuNPs-glycogen was centered at 520-540 nm with size diameter was 41.7 ± 0.2 nm. The vibrational bands of glycogen were observed at 1,000 to 1,200 cm^-1. The Au³⁺/Au⁰ redox coupling cycle was observed. The luminescence of AuNPs showed more stability by the addition of gradual concentrations of glycogen molecules. The detection (LOD) and quantitation limits (LOQ) were observed to be 0.89 and 2.95 µmol L^-1 respectively (R² = 0.99). The good chemical stability of this colloidal system and the glycogen molecule studied via density functional theory (DFT). The HOMO level of glycogen unit was closed near to LUMO level of Au³⁺. Conclusion: The associations formed between the gold nanoparticles and glycogen resulted in good chemical stability. This indicates that the quantification method proposed can be stably applied.

Roles of chitosan in synthesis, antibacterial and anti-biofilm properties of bionano silver and gold

Antibiotic-resistance and bacterial bioburden on wound surfaces are the significant challenges to wound healing. Silver and gold nanoparticles (are termed as AgNPs and AuNPs) have been investigated as alternative antimicrobial agents to combat antibiotic-resistant bacterial infections owing to their antibacterial and anti-biofilm activities. Chitosan (CS) has largely been used in nanoparticle synthesis as a stabilizing or capping agent. In this study, AgNPs and AuNPs were synthesized using different concentrations of aqueous extract of tiger milk mushroom (Lignosus rhinocerotis) (WETMM) and CS as reducing and stabilizing agent, respectively. Particle size and morphology of both were determined by dynamic light scattering (DLS) method and transmission electron microscopic analysis (TEM). FTIR analysis was conducted to determine the interactions between nanoparticle precursors. The observed peaks at 450 nm and 534-565 nm using a spectrophotometer were corresponded to the surface Plasmon resonance of AgNPs and AuNPs respectively, indicating the formation of respective nanoparticles. FTIR analysis confirmed the role of WETMM as a reducing agent and CS as a stabilizer of AgNPs and AuNPs. Faster formation of nanoparticles was observed besides an increase in particle size when higher CS concentrations were used. TEM micrographs revealed the spherical shape of most nanoparticles with particle sizes in the range of 4 to 58 nm and 18 to 28 nm for AgNPs and AuNPs, respectively. Both nanoparticles exhibited antimicrobial activity against Gram-positive and -negative bacteria, with AgNPs showing a superior antibacterial efficacy than AuNPs. Both microbroth dilution and agar well diffusion assays indicated that CS was an important component to facilitate antibacterial activity for AuNPs. Contrarily, CS stabilization did not enhance the antibacterial efficacy of AgNPs. CS-stabilized AgNPs and AuNPs achieved biofilm inhibition of 53.21% and 79.39% for Pseudomonas aeruginosa and 48.71% and 48.16% for Staphylococcus aureus, respectively. Similarly, CS stabilization enhanced the anti-biofilm activity of AuNPs but no such effect was seen for AgNPs. In conclusion, CS-stabilized AgNPs and AuNPs possess both antimicrobial and anti-biofilm activities. However, CS acted differently when combined with AgNPs and AuNPs, needing further investigation and optimization to improve the antimicrobial activity of both nanoparticles.

Microwave-Assisted Synchronous Nanogold Synthesis Reinforced by Kenaf Seed and Decoding Their Biocompatibility and Anticancer Activity

The combination of green-nanotechnology and biology may contribute to anticancer therapy. In this regard, using gold nanoparticles (GNPs) as therapeutic molecules can be a promising strategy. Herein, we proposed a novel biocompatible nanogold constructed by simply microwave-heating (MWI) Au3+ ions and kenaf seed (KS) extract within a minute. The phytoconstituents of KS extract have been utilized for safe synthesis of gold nanoparticles (KS@GNPs). The biogenic KS@GNPs were characterized by UV-vis Spectra, TEM, HR-TEM, XRD, FTIR, DLS, EDX, and SEAD techniques. The legitimacy and toxicity concern of KS@GNPs were tested against RAW 264.7 and NIH3T3 cell lines. The anticancer efficacy was verified using LN-229 cells. The pathways of KS@GNPs synthesis were optimized by varying the KS concentration (λmax 528 nm), gold salt amount (λmax 524 nm), and MWI times (λmax 522 nm). TEM displayed spherical shape and narrow size distribution (5-19.5 nm) of KS@GNPs, whereas DLS recorded Z-average size of 121.7 d·nm with a zeta potential of -33.7 mV. XRD and SAED ring patterns confirmed the high crystallinity and crystalline face centered cubic structure of gold. FTIR explored OH functional group involved in Au3+ ions reduction followed by GNPs stabilization. KS@GNPs exposure to RAW 264.7 and NIH3T3 cell lines did not induce toxicity while dose-dependent overt cell toxicity and reduced cell viability (26.6%) was observed in LN-229 cells. Moreover, the IC50 (18.79 µg/mL) treatment to cancer cell triggered cellular damages, excessive ROS generation, and apoptosis. Overall, this research exploits a sustainable method of KS@GNPs synthesis and their anticancer therapy.

Alpha-ketoglutarate decorated iron oxide-gold core-shell nanoparticles for active mitochondrial targeting and radiosensitization enhancement in hepatocellular carcinoma

The ability of some tumours to impart radioresistance serves as a barrier in the cancer therapeutics. Mitochondrial metabolism significantly persuades this cancer cell survival, incursion and plays a crucial role in conferring radioresistance. It would be of great importance to target the active mitochondria to overcome this resistance and achieve tumoricidal efficacy. The current report investigates the improved radiosensitization effect (under Gamma irradiation) in hepatocellular carcinoma through active mitochondrial targeting of alpha-ketoglutarate decorated iron oxide-gold core-shell nanoparticles (GNP). The loading of a chemotherapeutic drug N-(4-hydroxyphenyl)retinamide in GNP allows adjuvant chemotherapy, which further sensitizes cancerous cells for radiotherapy. The GNP shows a drug loading efficiency of 8.5 wt% with a sustained drug release kinetics. The X-Ray diffraction (XRD) pattern and High-Resolution Transmission Electron microscopy (HRTEM) indicates the synthesis of core iron oxide nanoparticles with indications of a thin layer of gold shell on the surface with 1:7 ratios of Fe: Au. The GNP application significantly reduced per cent cell viability in Hepatocellular carcinoma cells through improved radiosensitization at 5 Gy gamma radiation dose. The molecular mechanism revealed a sharp increment in reactive oxygen species (ROS) generation and DNA fragmentation. The mitochondrial targeting probes confirm the presence of GNP in the mitochondria, which could be the possible reason for such improved cellular damage. In addition to the active mitochondrial targeting, the currently fabricated nanoparticles work as a potent Magnetic Resonance Imaging (MRI)/Computed Tomography (CT) contrast agent. This multifunctional therapeutic potential makes GNP as one of the most promising theragnostic molecules in cancer therapeutics.

Rapid in-situ growth of gold nanoparticles on cationic cellulose nanofibrils: Recyclable nanozyme for the colorimetric glucose detection

Novel microwave-assisted green in-situ synthesis of positively charged gold nanoparticles (AuNPs) supported by cationic cellulose nanofibrils (C.CNF) within 30 s and devoid of additional reducing agent is reported. Peroxidase activity of these positive AuNPs was studied and that appeared to be superior over its negative charged counterpart. Further the AuNPs@C.CNF is casted into a film which makes it reusable. Using TMB substrate, simple and sensitive colorimetric detection methods for H₂O₂ and glucose were established. Under optimal conditions, the linear ranges were found to be 0.5-30 μM and 1-60 μM, and the detection limits were 0.30 and 0.67 μM for H₂O₂ and glucose, respectively. The film was potentially reused for the detection of glucose up to five cycles without a decrease in the activity. Further, this technique was employed to quantify glucose in human serum samples, and the obtained results were comparable with those of the standard GOD-POD method.

Synthesis of gold nanostructures using glycine as the reducing agent

Biological synthesis of gold nanostructures could potentially offer an environmentally friendly alternative to traditional chemical synthetic methods. During the last decades, various biomolecules, including amino acids, have been successfully used as reducing and capping agents to synthesize multi-shaped gold nanostructures. A grand challenge in this field is to increase our ability to control the size and shape of gold nanostructures formed precisely by systematic synthetic approaches based on the understanding of the mechanism for structural determination. In this study, using glycine as the model amino acid and chloroaurate (AuCl₄ ^-) ions as the precursor solution, we report the finding that the shape of the gold nanostructures synthesized showed a strong correlation with the speciation of gold complexes determined by the pH, precursor concentration and chloride concentration of the solvent system. The gold chloro-hydroxy speciation [AuCl_x(OH)_4-x]^- (with x = 0-4) influenced the shape of the gold nanostructures formed, with gold nanoplatelets, nanotriangles, nanokites and nanoribbons observed at x = 4, 3, 2 and 1, respectively, and spherical nanoparticles observed at x = 0. Glycine was found to play a role as a reducing agent, but no significant effect on the morphology was observed, indicating the dominance of gold chloro-hydroxy speciation in the structural formation. These results collectively provide synthetic considerations to systematically synthesize non-spherical to spherical biosynthesized gold nanostructures by controlling the speciation of [AuCl_x(OH)_4-x]^-.

Glycogen as a Building Block for Advanced Biological Materials

Biological nanoparticles found in living systems possess distinct molecular architectures and diverse functions. Glycogen is a unique biological polysaccharide nanoparticle fabricated by nature through a bottom-up approach. The biocatalytic synthesis of glycogen has evolved over time to form a nanometer-sized dendrimer-like structure (20-150 nm) with a highly branched surface and a dense core. This makes glycogen markedly different from other natural linear or branched polysaccharides and particularly attractive as a platform for biomedical applications. Glycogen is inherently biodegradable, nontoxic, and can be functionalized with diverse surface and internal motifs for enhanced biofunctional properties. Recently, there has been growing interest in glycogen as a natural alternative to synthetic polymers and nanoparticles in a range of applications. Herein, the recent literature on glycogen in the material-based sciences, including its use as a constituent in biodegradable hydrogels and fibers, drug delivery vectors, tumor targeting and penetrating nanoparticles, immunomodulators, vaccine adjuvants, and contrast agents, is reviewed. The various methods of chemical functionalization and physical assembly of glycogen nanoparticles into multicomponent nanodevices, which advance glycogen toward a functional therapeutic nanoparticle from nature and back again, are discussed in detail.

Self-assembled drug loaded glycosyl-protein metal nanoconstruct: Detailed synthetic procedure and therapeutic effect in solid tumor treatment

Nanotechnology-based drug delivery research has largely focused on developing well efficient localized delivery therapeutic agents to overcome the limitations of non-specificity and toxicity of conventional chemotherapy. Herein, we constructed a nanoplatform based on a self-assembled polysaccharide-protein conjugate to deliver anti-tumor drug doxorubicin and gold nanoparticles (DOX@PST-BSA AuNPs) for cancer therapy. The self-assembled DOX@PST-BSA AuNPs exhibited higher stability and thermal properties which enable them for drug delivery via passive targeting. The fluorescent property of the drug contributes to the self-monitoring of NPs Biodistribution in vitro and in vivo. Furthermore, the NPs showed negligible cytotoxicity and tissue accumulation in normal cells in vivo. Importantly, the NPs could load the anti-tumor drug with high encapsulation efficiency and competently delivered into the tumor microenvironment thereby inhibit tumor growth significantly through apoptotic induction. Notably, DOX@PST-BSA AuNPs exhibits low systemic toxicity and very few side effects in vivo. Based on the explored features, these NPs could serve as a promising multifunctional drug delivery nanoplatform for cancer therapy.

Detection and discrimination of volatile organic compounds by noble metal nanoparticle functionalized MoS2 coated biodegradable paper sensors

In the current study, noble metal nanoparticle functionalized MoS₂ coated biodegradable low-cost paper sensors were fabricated for the selective detection of low concentrations of volatile organic compounds (VOCs).

Recovery of gold from electronic wastewater by Phomopsis sp. XP-8 and its potential application in the degradation of toxic dyes

Environmentally friendly, efficient, and economical methods of gold recovery are significant challenges for high-tech industries and environmental protection. In this study, Phomopsis sp. XP-8, a filamentous endophytic fungus, demonstrated great potential for selectively recovering gold from electronic wastewater without any pretreatment and was shown to be convenient and safe in practical application. Under optimum conditions, the gold recovery rate was more than 80% at a dilute concentration of Au³⁺. Model-fitting analysis indicated the adsorption of Au³⁺ was well described by the pseudo-second-order kinetic model and the Langmuir isotherm model. The maximum Au³⁺ adsorption was from 208 to 280 mg/g within the temperature range of 20-50 °C. The data from electronic wastewater revealed its great potential for selective recovery of gold from complex aqueous solutions. Additionally, the formed nanogold-bioconjugates exhibited efficient degradation of toxic dyes in wastewater, which demonstrated the potential application of these byproducts produced via the biosorption process.

Structure, bioactivity and applications of natural hyperbranched polysaccharides

In recent years, hyperbranched polymers, especially the natural hyperbranched polysaccharides (HBPSs), are receiving much attention due to their diverse biological activities and applications. With high degree of branching (DB), HBPSs mainly exist in the form of either a comb-brush shape, dendrimer-like particulate, or globular particle. HBPSs also possess some unique properties, such as high density, large spatial cavities, and numerous terminal functional groups, which distinguish them from other polymers. As a natural biopolymer, HBPS has excellent bioavailability, biocompatibility, and biodegradability, which have versatile applications in the fields of food, medicine, cosmetic, and nanomaterials. In this review, the source and structure of HBPSs from plant, animal, microbial and fungal origins as well as their biological functions and applications are covered, with the aim of further advancing the research of their structure and bioactivity.

Gold Nanoparticle-Functionalized Reverse Thermal Gel for Tissue Engineering Applications

Utilizing polymers in cardiac tissue engineering holds promise for restoring function to the heart following myocardial infarction, which is associated with grave morbidity and mortality. To properly mimic native cardiac tissue, materials must not only support cardiac cell growth but also have inherent conductive properties. Here, we present an injectable reverse thermal gel (RTG)-based cardiac cell scaffold system that is both biocompatible and conductive. Following the synthesis of a highly functionalizable, biomimetic RTG backbone, gold nanoparticles (AuNPs) were chemically conjugated to the backbone to enhance the system's conductivity. The resulting RTG-AuNP hydrogel supported targeted survival of neonatal rat ventricular myocytes (NRVMs) for up to 21 days when cocultured with cardiac fibroblasts, leading to an increase in connexin 43 (Cx43) relative to control cultures (NRVMs cultured on traditional gelatin-coated dishes and RTG hydrogel without AuNPs). This biomimetic and conductive RTG-AuNP hydrogel holds promise for future cardiac tissue engineering applications.

Role of TiO2 Nanoparticles and UV Irradiation in the Enhancement of SERS Spectra To Improve Levamisole and Cocaine Detection on Au Substrates

The original goal of this study was the employment of surface-enhanced Raman spectroscopy (SERS) for the analysis of real cocaine samples (containing adulterants) on composite Au-TiO₂ nanomaterials to achieve low detection limits suitable for the analysis of illicit drugs and controlled substances and to exploit the photodegradation activity of TiO₂ to recycle the SERS substrate for repeated analyses. The photodegradation (self-cleaning) effects of the Au-TiO₂ composite nanomaterials by ultraviolet (UV) radiation are known. These effects were investigated on large-area SERS substrates immersed in the TiO₂ nanoparticle aqueous suspension. The cocaine samples were measured on electrochemically gold-plated platinum targets. Surprisingly, the intensity of SERS spectra of the pure cocaine did not change after immersion in a suspension of TiO₂ under UV irradiation. However, for some real cocaine samples, the overall intensity of the SERS spectra was even higher after the treatment by TiO₂ and UV radiation as compared to the usual Au substrate. This unexpected signal amplification (valuable for illicit drug detection) was found to be caused mainly by the contained levamisole, which is used as a medical drug and is one of the frequent adulterants of cocaine. Both the sole effect of TiO₂ on the levamisole spectrum intensity and the role of UV irradiation were inspected separately. Finally, an investigation of both the TiO₂ and UV radiation treatments was performed, demonstrating (i) the necessity of both factors for selective SERS signal enhancement of the adulterant and (ii) the revision of general anticipation of the role of TiO₂ in SERS systems.

Hierarchical Nanoparticle Assemblies Formed via One-Step Catalytic Stamp Pattern Transfer

The one-step catalytic stamp pattern transfer process is described for producing arrays of hierarchical nanoparticle assemblies. The method simply combines in situ nanoparticle synthesis triggered by free residual Si-H groups on PDMS stamps and the lift-off pattern transfer technique. No additional nanoparticle synthesis procedure is required before the pattern transfer process. Exquisitely uniform and precisely spaced hierarchical nanoparticle assemblies with designed geometry can be rapidly produced using the catalytic stamp pattern transfer process. Sequential catalytic stamp pattern transfer also is described to generate multilayered, hierarchical nanoparticle assemblies with various geometries. The hierarchical nanoparticle assemblies catalytically transferred onto the surface are not just nanoparticles but nanoparticle-polydimethylsiloxane residue composites. The in situ-synthesized nanoparticles retain optical properties. The hierarchical nanoparticle assemblies with precisely controlled geometry further show potential in the application of surface-enhanced Raman scattering. The capability of one-step catalytic stamp pattern transfer allows the scalable and reproducible fabrication of well-defined hierarchical nanoparticle assemblies.

Nanoparticle self-assembly: from interactions in suspension to polymer nanocomposites

Recent experimental results using in particular small-angle scattering to characterize the self-assembly of mainly hard spherical nanoparticles into higher ordered structures ranging from fractal aggregates to ordered assemblies are reviewed. The crucial control of interparticle interactions is discussed, from chemical surface-modification, or the action of additives like depletion agents, to the generation of directional patches and the use of external fields. It is shown how the properties of interparticle interactions have been used to allow inducing and possibly controlling aggregation, opening the road to the generation of colloidal molecules or potentially metamaterials. In the last part, studies of the microstructure of polymer nanocomposites as an application of volume-spanning and stress-carrying aggregates are discussed.

ZnO-modified cellulose fiber sheets for antibody immobilization

Cellulose fiber sheets impregnated with saccharide capped-ZnO nanoparticles were used as bioactive materials for antibody immobilization. First, ZnO nanoparticles were synthesized in the presence of glucose (monosaccharide), sucrose (disaccharide) as well as alginic acid and starch (polysaccharides). The pine cellulose fibers were then modified by the obtained saccharide capped nanoparticles and further incorporated into the sheets. The presence of ZnO significantly improved the immobilization of the antibodies on the surface of the sheets. After rewetting the alginic acid-ZnO modified sheets with saline solution, the retention of antibodies was about 95%. A high degree of the immobilization of biomolecules is an important feature for possible fabrications of bioactive- or biosensing-papers and we successfully tested the sheets on the detection of blood types using (A, B, and D blood antibodies). The ZnO nanoparticles affected also the other properties of the sheets. The ZnO-modified fiber sheets showed higher values of tensile index (strength), smoothness and opacity, while the value of porosity was substantially lower than that of the unmodified sheet. The presence of ZnO nanoparticles provided also the antimicrobial activity to the sheets. They showed a strong activity against bacteria (Escherichia coli and Staphylococcus aureus) and strong resistance to the attack of cellulase producing fungus Gloeophyllum trabeum.