Carboxymethyl Chitosan as a Matrix Material for Platinum, Gold, and Silver Nanoparticles

Solvent-less carboxymethylation-induced electrostatic crosslinking of chitosan

The successful N-carboxymethylation and concomitant crosslinking of solid chitosan upon heating its mixture with solid monochloroacetic acid, without the use of solvents or catalysts, is reported. The N-carboxymethylation was confirmed through the analysis of the partially depolymerized product using NMR spectroscopy, as well as a control reaction with lysine. This transformation was facilitated by the nucleophilic nature of the free amine group in the repeating unit of chitosan, which possesses lone pair of electrons capable of attacking the carbon center bearing the leaving group and displacing the leaving group in a concerted manner. The crosslinking, on the other hand, was established by the observed insolubility in aqueous acidic solutions, even when subjected to prolonged heating at 60 °C. This crosslinking occurs due to the electrostatic interactions between the carboxylate groups and the adjacent ammonium groups, as supported by evidence from FTIR spectroscopy and a control reaction involving ethyl chloroacetate. The resulting crosslinked carboxymethyl chitosan demonstrated its usefulness in the adsorption of methyl orange and fluorescein, as well as functioning as an organic catalyst for aza-Michael addition, Hantzsch reaction, and substituted perimidine synthesis.

Parallel Monitoring of Glucose, Free Amino Acids, and Vitamin C in Fruits Using a High-Throughput Paper-Based Sensor Modified with Poly(carboxybetaine acrylamide)

Herein, a cost-effective and portable microfluidic paper-based sensor is proposed for the simultaneous and rapid detection of glucose, free amino acids, and vitamin C in fruit. The device was constructed by embedding a poly(carboxybetaine acrylamide) (pCBAA)-modified cellulose paper chip within a hydrophobic acrylic plate. We successfully showcased the capabilities of a filter paper-based microfluidic sensor for the detection of fruit nutrients using three distinct colorimetric analyses. Within a single paper chip, we simultaneously detected glucose, free amino acids, and vitamin C in the vivid hues of cyan blue, purple, and Turnbull's blue, respectively, in three distinctive detection zones. Notably, we employed more stable silver nanoparticles for glucose detection, replacing the traditional peroxidase approach. The detection limits for glucose reached a low level of 0.049 mmol/L. Meanwhile, the detection limits for free amino acids and vitamin C were found to be 0.236 mmol/L and 0.125 mmol/L, respectively. The feasibility of the proposed sensor was validated in 13 different practical fruit samples using spectrophotometry. Cellulose paper utilizes capillary action to process trace fluids in tiny channels, and combined with pCBAA, which has superior hydrophilicity and anti-pollution properties, it greatly improves the sensitivity and practicality of paper-based sensors. Therefore, the paper-based colorimetric device is expected to provide technical support for the nutritional value assessment of fruits in the field of rapid detection.

Polysaccharide‑platinum complexes for cancer theranostics

Platinum anticancer drugs have been explored and developed in recent years to reduce systematic toxicities and resist drug resistance. Polysaccharides derived from nature have abundant structures as well as pharmacological activities. The review provides insights on the design, synthesis, characterization and associating therapeutic application of platinum complexes with polysaccharides that are classified by electronic charge. The complexes give birth to multifunctional properties with enhanced drug accumulation, improved tumor selectivity and achieved synergistic antitumor effect in cancer therapy. Several techniques developing polysaccharides-based carriers newly are also discussed. Moreover, the lasted immunoregulatory activities of innate immune reactions triggered by polysaccharides are summarized. Finally, we discuss the current shortcomings and outline potential strategies for improving platinum-based personalized cancer treatment. Using platinum-polysaccharides complexes for improving the immunotherapy efficiency represents a promising framework in future.

Ni -chitosan/carbon nanotube: An efficient biopolymer -inorganic catalyst for selective hydrogenation of acetylene

This work developed an efficient Ni catalyst based on chitosan for selective hydrogenation of acetylene. The Ni catalyst was prepared by the reaction of the chitosan/carbon nanotube composite with NiSO₄ solution. The synthesized Ni-chitosan/carbon nanotube catalyst was characterized by inductively coupled plasma, FTIR, SEM and XRD. The results of FTIR and XRD demonstrated that Ni²⁺ successfully coordinated with chitosan. The addition of chitosan greatly improved the catalytic performances of Ni-chitosan/carbon nanotube catalyst. Over the Ni-chitosan/carbon nanotube catalyst, both the acetylene conversion and the selectivity to ethylene all achieved 100% at 160 °C and 190 °C, respectively. The catalytic performances of 6 mg Ni-chitosan/carbon nanotube catalyst were even better than that of 400 mg Ni single atom catalyst in literature. Extending the crosslinking time of chitosan and increasing the amount of the crosslinking agent were beneficial to enhance the catalytic effect of Ni-chitosan/carbon nanotube catalyst.

Hyperbranched Polymer Network Based on Electrostatic Interaction for Anodes in Lithium-Ion Batteries

Silicon is considered as one of the ideal anode materials for the new generation of lithium-ion batteries due to its extremely high theoretical specific capacity. Nevertheless, in the actual charging and discharging process, the Si electrode will lose its electrochemical performance due to the huge volume change of Si nanoparticles resulting in detachment from the surface of the fluid collector. The polymer binder can bond the Si nanoparticles together in a three-dimensional cross-linking network, which can thus effectively prevent the Si nanoparticles from falling off the surface of the fluid collector due to the drastic change of volume during the charging and discharging process. Therefore, this study developed a new polymer binder based on electrostatic interaction with hyperbranched polyethylenimine (HPEI) as the main body and water-soluble carboxylated polyethylene glycol (CPEG) as the cross-linker, where the degree of cross-linking can be easily optimized by adjusting the pH value. The results demonstrate that, when the density of positive and negative charges in the binder is relatively balanced at pH 7, the stability of the battery's charge-discharge cycle is significantly improved. After 200 cycles of constant current charge-discharge test, the specific capacity retention rate is 63.3%.

Facile synthesis of nanomaterials as nanofertilizers: a novel way for sustainable crop production

Nutrient fertilization plays a major role in improving crop productivity and maintaining soil fertility. In the last few decades, the productivity of current agricultural practices highly depends on the use of chemical fertilizers. Major drawback of traditional fertilizers is their low crop nutrient use efficiency and high loss into water. Nanomaterial in agriculture is a multipurpose tool for increasing growth, development, and yield of plants. Nanotechnology facilitates the amplifying of agriculture production by reducing relevant losses and improving the input efficiency. Nanotechnology has emerged as an attractive field of research and has various agriculture applications, especially the use of nano-agrochemicals to increase nutrient use efficiency and agricultural yield. Nanofertilizers are more effective as compared to chemical fertilizers due to their cost-efficient, eco-friendly, non-toxic, and more stable in nature. Overall, this chapter focuses on synthesis of nanofertilizers through physical, chemical, and biological methods. This chapter will also explore the use of nano-enabled fertilizers to enhance the nutrient use efficiency for sustainable crop production, and global food safety.

Retardation of Bacterial Biofilm Formation by Coating Urinary Catheters with Metal Nanoparticle-Stabilized Polymers

Urinary catheter infections remain an issue for many patients and can complicate their health status, especially for individuals who require long-term catheterization. Catheters can be colonized by biofilm-forming bacteria resistant to the administered antibiotics. Therefore, this study aimed to investigate the efficacy of silver nanoparticles (AgNPs) stabilized with different polymeric materials generated via a one-step simple coating technique for their ability to inhibit biofilm formation on urinary catheters. AgNPs were prepared and characterized to confirm their formation and determine their size, charge, morphology, and physical stability. Screening of the antimicrobial activity of nanoparticle formulations and determining minimal inhibitory concentration (MIC) and their cytotoxicity against PC3 cells were performed. Moreover, the antibiofilm activity and efficacy of the AgNPs coated on the urinary catheters under static and flowing conditions were examined against a clinical isolate of Escherichia coli. The results showed that the investigated polymers could form physically stable AgNPs, especially those prepared using polyvinyl pyrrolidone (PVP) and ethyl cellulose (EC). Preliminary screening and MIC determinations suggested that the AgNPs-EC and AgNPs-PVP had superior antibacterial effects against E. coli. AgNPs-EC and AgNPs-PVP inhibited biofilm formation to 58.2% and 50.8% compared with AgNPs-PEG, silver nitrate solution and control samples. In addition, coating urinary catheters with AgNPs-EC and AgNPs-PVP at concentrations lower than the determined IC50 values significantly (p < 0.05; t-test) inhibited bacterial biofilm formation compared with noncoated catheters under both static and static and flowing conditions using two different types of commercial Foley urinary catheters. The data obtained in this study provide evidence that AgNP-coated EC and PVP could be useful as potential antibacterial and antibiofilm catheter coating agents to prevent the development of urinary tract infections caused by E. coli.

The Effect of Nano-chitosan and Nano-curcumin on Radiated Parotid Glands of Albino Rats: Comparative Study

Decreasing the salivary flow rate manifested by xerostomia occurs early during the irradiation treatment. The duration of depressed salivary function varies among patients. Various histopathological changes occur in the salivary glands. The current study was performed to investigate and compare between the possible anti-radiotherapeutic effect of the gamma rays-synthesized curcumin nanoparticles (Cur NPs), and chitosan nanoparticles (Cs NPs). They were utilized to overcome the histopathological changes associated with radiation therapy in albino rats’ parotid glands. Sixty adult male Albino rats were utilized, fifteen as control group, fifteen as radiated group and thirty as Cur NPs and Cs NPs treatment groups. The parotid glands were dissected and examined histologically, immunohistochemically for vascular endothelial growth factor (VEGF) as well as histo-morphometrically. The histological results proved the antiradio-therapeutic effect of Cur NPs, and Cs NPs, with the least degenerative changes in the Cur NPs treated group. A high significant increase in VEGF was recorded in the radiated group as compared to the other treated groups. Cs NPs have proved to be an anti-radiotherapeutic and anti-oxidant substrate in treating the histopathological changes in radiated parotid glands of albino rats. However, it was lagging behind Cur NPs in all analyses but non-significant differences between them have been recorded.

Graphical Abstract

An Overview of Green Synthesis and Potential Pharmaceutical Applications of Nanoparticles as Targeted Drug Delivery System in Biomedicines

Nanotechnology-based nanomedicine offers several benefits over conventional forms of therapeutic agents. Moreover, nanomedicine has become a potential candidate for targeting therapeutic agents at specific sites. However, nanomedicine prepared by synthetic methods may produce unwanted toxic effects. Due to their nanosize range, nanoparticles can easily reach the reticuloendothelial system and may produce unwanted systemic effects. The nanoparticles produced by the green chemistry approach would enhance the safety profile by avoiding synthetic agents and solvents in its preparations. This review encompasses toxicity consideration of nanoparticles, green synthesis techniques of nanoparticle preparation, biomedical application of nanoparticles, and future prospects.

Role of Polysaccharides Mimetic Components in Targeted Cancer Treatment

Organic or inorganic compounds are synthesized or formulated in a manner that they completely show their therapeutic actions like as a natural polysaccharide in the body. Polysaccharides, the major type of natural polymers, are efficiently biologically active, non-toxic, hydrophilic, and biodegradable and show various properties. In this manuscript, the main focus is on delivering anticancer drugs with the help of mimetic components of polysaccharides. All data collected for this manuscript was from PubMed, Elsevier, Taylor, and Francis Bentham science journals. Most chemotherapeutics are therapeutically toxin to the human body, have a narrow therapeutic index, sluggish pharmaceutical delivery mechanisms, and are poorly soluble in water. The use of mimetic components of polysaccharides leads to the enhancement of the solubility of drugs in the biological environment. The manuscript summarizes the use of mimetic components of polysaccharides along with anticancer agents which are capable to inhibit the growth of cancerous cells in the body which shows lesser adverse effects in the biological system compared to other therapies.

Synthesis of Chitosan-Silver Nanoparticle Composite Spheres and Their Antimicrobial Activities

Synthesis of silver nanoparticles–chitosan composite particles sphere (AgNPs-chi-spheres) has been completed and its characterization was fulfilled by UV–vis spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and zetasizer nano. UV–vis spectroscopy characterization showed that AgNPs-chi-spheres gave optimum absorption at a wavelength of 410 nm. The XRD spectra showed that the structure of AgNPs-chi-spheres were crystalline and spherical. Characterization by SEM showed that AgNPs-chi-spheres, with the addition of 20% of NaOH, resulted in the lowest average particle sizes of 46.91 nm. EDX analysis also showed that AgNPs-chi-spheres, with the addition of a 20% NaOH concentration, produced particles with regular spheres, a smooth and relatively nonporous structure. The analysis using zetasizer nano showed that the zeta potential value and the polydispersity index value of the AgNPs-chi-sphere tended to increase with an increased NaOH concentration. The results of the microbial activity screening showed that the AgNP-chi-Spheres with highest concentration of NaOH, produced the highest inhibition zone diameters against S. aureus, E. coli, and C. albicans, with inhibition zone diameters of 19.5, 18.56, and 12.25 nm, respectively.

Magnetic Resonance Imaging of Transplanted Porcine Neonatal Pancreatic Cell Clusters Labeled with Chitosan-Coated Superparamagnetic Iron Oxide Nanoparticles in Mice

Neonatal pancreatic cell clusters (NPCCs) are potential tissues for the treatment of diabetes. Different from adult cells, they continuously proliferate and differentiate after transplantation. In this study, we utilized magnetic resonance imaging (MRI) to detect and monitor implanted NPCCs. NPCCs were isolated from one-day-old neonatal pigs, cultured for three days, and then incubated overnight with the contrast agent chitosan-coated superparamagnetic iron oxide (CSPIO) nanoparticles. In vitro, Prussian blue staining and MR scans of CSPIO-labeled NPCCs were performed. In vivo, we transplanted 2000 CSPIO-labeled NPCCs under the kidney capsule of nondiabetic nude mice. Recipients were scanned with 7.0T MRI. Grafts were removed for histology with insulin and Prussian blue staining. After being incubated overnight with CSPIO, NPCCs showed positive iron staining and appeared as dark spots on MR scans. After transplantation of CSPIO-labeled NPCCs, persistent hypointense areas were observed at recipients’ implant sites for up to 54 days. Moreover, histology showed colocalization of the insulin and iron staining in 15-, 51- and 55-day NPCC grafts. Our results indicate that transplanted NPCCs survived and differentiated to β cells after transplantation, and that MRI is a useful tool for the detection and monitoring of CSPIO-labeled NPCC grafts.

Electrochemiluminescent biosensor for ultrasensitive detection of lymphoma at the early stage using CD20 markers as B cell-specific antigens

Herein, by taking advantage of the special binding of an aptamer to the membrane surface of a B cell and accumulation of the positive charges of a nanocomposite, including luminol-chitosan-platinum nanoparticles (L-Cs-Pt NPs), on the negatively charge of the aptamer phosphate backbone, a sensitive, simple, selective and rapid strategy for the detection of lymphoma cells by a new label-free electrogenerated chemiluminescence (ECL) aptasensor has been introduced. With increasing concentrations of B lymphoma cells, the nanocomposite detaches from the aptamer, leading to a decrease in the ECL of a luminol and H₂O₂ system. With high loading of luminol and Pt NPs on a chitosan, together with the electrocatalytic effect of Pt NPs, enhanced sensitive detection of cancer cells with a limit of detection of 31 cells/mL was achieved. Step-by-step modification and biosensor response to cancer cells was monitored by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and ECL. The aptasensor exhibited excellent specificity for lymphoma cells vs breast cancer (MCF-7) and human embryonic kidney (HEK293) cell lines as potential interferents. Finally, the performance of the aptasensor in blood samples was assessed against a commercial flow cytometric method. Satisfactory results confirmed the applicability of the proposed biosensing platform.

Small AgNP in the Biopolymer Nanocomposite System

In this work, ultra-small and stable silver nanoparticles (AgNP) on chitosan biopolymer (BP/AgP) were prepared by in situ reduction of the diamminesilver(I) complex ([Ag(NH₃)₂]⁺) to create a biostatic membrane system. The small AgNP (3 nm) as a stable source of silver ions, their crystal form, and homogeneous distribution in the whole solid membrane were confirmed by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The X-ray photoelectron spectroscopy (XPS) and Auger analysis were applied to investigate the elemental composition, concentration, and chemical state of surface atoms. It was found that ultra-small metallic nanoparticles might form a steady source of silver ions and enhance the biostatic properties of solid membranes. Ultra-small AgNP with disturbed electronic structure and plasmonic properties may generate interaction between amine groups of the biopolymer for improving the homogeneity of the nanometallic layer. In this work, the significant differences between the typical way (deposition of ex-situ-prepared AgNP) and the proposed in-situ synthesis approach were determined. The improved thermal stability (by thermogravimetry and differential scanning calorimetry (TG/DSC) analysis) for BP/AgP was observed and explained by the presence of the protective layer of a low-molecular silver phase. Finally, the antibacterial activity of the BP/AgP nanocomposite was tested using selected bacteria biofilms. The grafted membrane showed clear inhibition properties by destruction and multiple damages of bacteria cells. The possible mechanisms of biocidal activity were discussed, and the investigation of the AgNP influence on the bacteria body was illustrated by AFM measurements. The results obtained concluded that the biopolymer membrane properties were significantly improved by the integration with ultra-small Ag nanoparticles, which added value to its applications as a biostatic membrane system for filtration and separation issues.

Crosslinked chitosan embedded TiO2 NPs and carbon dots-based nanocomposite: An excellent photocatalyst under sunlight irradiation

Herein, a new hybrid nanocomposite, comprising of titania nanoparticles (TiO₂ NPs) and carbon dots (CDs) deposited polyvinyl imidazole crosslinked chitosan [cl-Ch-p(VI)/TiO₂NPs-CDs] has been developed. The nanocomposite has been synthesised by in-situ deposition of TiO₂ NPs and CDs onto the surface of the copolymer under microwave irradiation. To the best of our knowledge, this in-situ approach has effectively been applied for the first time to fabricate green fluorescent CDs from sugar cane juice at moderate temperature (75 °C) under microwave irradiation. The developed nanocomposite has been characterized using UV-Vis spectroscopy, ¹³C NMR, XRD, HR-TEM, STEM and XPS analyses. The results suggest that the successful deposition of TiO₂ NPs and CDs onto the surface of crosslinked chitosan is achieved. The experimental studies indicate that the NPs/CDs-impregnated nanocomposite allows efficient photocatalytic degradation of toxic organic compounds (~98.6% degradation of 2,4-dicholorophenol, ~95.8% degradation of Reactive Blue 4, ~98.2% degradation of Reactive Red 15) in the presence of sunlight. Finally, LC-MS analysis of the resultant degraded materials reveals the formation of organic molecules with lower molecular mass.

Green Synthesis of Metallic Nanoparticles and Their Potential Applications to Treat Cancer

Nanoparticle synthesis using microorganisms and plants by green synthesis technology is biologically safe, cost-effective, and environment-friendly. Plants and microorganisms have established the power to devour and accumulate inorganic metal ions from their neighboring niche. The biological entities are known to synthesize nanoparticles both extra and intracellularly. The capability of a living system to utilize its intrinsic organic chemistry processes in remodeling inorganic metal ions into nanoparticles has opened up an undiscovered area of biochemical analysis. Nanotechnology in conjunction with biology gives rise to an advanced area of nanobiotechnology that involves living entities of both prokaryotic and eukaryotic origin, such as algae, cyanobacteria, actinomycetes, bacteria, viruses, yeasts, fungi, and plants. Every biological system varies in its capabilities to supply metallic nanoparticles. However, not all biological organisms can produce nanoparticles due to their enzymatic activities and intrinsic metabolic processes. Therefore, biological entities or their extracts are used for the green synthesis of metallic nanoparticles through bio-reduction of metallic particles leading to the synthesis of nanoparticles. These biosynthesized metallic nanoparticles have a range of unlimited pharmaceutical applications including delivery of drugs or genes, detection of pathogens or proteins, and tissue engineering. The effective delivery of drugs and tissue engineering through the use of nanotechnology exhibited vital contributions in translational research related to the pharmaceutical products and their applications. Collectively, this review covers the green synthesis of nanoparticles by using various biological systems as well as their applications.

Impact of nanosystems in Staphylococcus aureus biofilms treatment

Staphylococcus aureus (S. aureus) is considered by the World Health Organization as a high priority pathogen for which new therapies are needed. This is particularly important for biofilm implant-associated infections once the only available treatment option implies a surgical procedure combined with antibiotic therapy. Consequently, these infections represent an economic burden for Healthcare Systems. A new strategy has emerged to tackle this problem: for small bugs, small particles. Here, we describe how nanotechnology-based systems have been studied to treat S. aureus biofilms. Their features, drawbacks and potentialities to impact the treatment of these infections are highlighted. Furthermore, we also outline biofilm models and assays required for preclinical validation of those nanosystems to smooth the process of clinical translation.

Mitigating effects of Bean yellow mosaic virus infection in faba bean using new carboxymethyl chitosan-titania nanobiocomposites

Bean yellow mosaic virus (BYMV) is the main cause of the mosaic and malformation of many plants, worldwide. Thus, the triggering of plant systemic resistance against BYMV is of great interest. In this endeavor, we aimed to explore the capacity of new carboxymethyl chitosan-titania nanobiocomposites (NBCs, NBC1,2) to trigger faba bean plants resistance against BYMV. Effects of NBCs on faba bean (Vicia faba L.) disease severity (DS), growth parameters, and antioxidant defense system activity were investigated under BYMV stress. Noticeably that the DS in NBCs-treated faba bean was significantly reduced compared to untreated plants. Moreover, treatment with NBCs was remarkably increased growth indices, photosynthetic pigments, membrane stability index, and relative water content compared to challenge control. Additionally, enzymatic and non-enzymatic antioxidants and total soluble protein were significantly increased. Contrary, electrolyte leakage, hydrogen peroxide, and lipid peroxidation were reduced. Interestingly that NBC1 has higher efficacy than NBC2 in triggering plant immune-system against BYMV as indicated from DS percentage (DS = 10.66% and 19.33% in case of plants treated with NBC1 and NBC2, respectively). This could be attributed to the higher content of TNPs in NBC1 (21.58%) as compared to NBC2 (14.32%). Overall, NBCs offer safe and economic antiviral agents against BYMV.

In situ generation of silver nanoparticles and nanocomposite films based on electrodeposition of carboxylated chitosan

Herein, for the first time the electrodeposition of carboxylated chitosan is studied and utilized for the synthesis of silver nanoparticles (AgNPs) and generation of AgNPs/carboxylated chitosan nanocomposite films. Particularly, AgNPs are in situ synthesized on electrodes or substrates during the electrodeposition. Carboxylated chitosan not only acts as the green reducing agent and stabilizing agent for preparing AgNPs, but also serves as the main component in the electrodeposited nanocomposite film. The experimental results indicate that a smooth and homogeneous film is formed on the silver plate after electrodeposition, and the electrodeposited film can be detached from the silver plate as an independent film. The TEM observation and spectroscopic analysis results confirm the existence of AgNPs (the average size of 10 nm) in the nanocomposite film. The nanocomposite films with various shapes can be fabricated by the spatial selectivity of electrodeposition. In addition, the nanocomposite film containing AgNPs shows favorable antibacterial properties.

A new way to prepare gold nanoparticles by sputtering - Sterilization, stability and other properties

We have developed a novel simple method for effective preparing gold nanoparticles (AuNPs) intended for utilization in biomedicine. The method is based on gold sputtering into liquid poly(ethylene glycol) (PEG). The PEG was used as a basic biocompatible stabilizer of the AuNP colloid. In addition, two naturally occurring polysaccharides - Chitosan (Ch) and Methylcellulose (MC) - were separately diluted into the PEG base with the aims to enhance the yield of the sputtering without changing the sputtering parameters, and to further improve the stability and the biocompatibility of the colloid. The colloids were sterilized by steam, and their stability was measured before and after the sterilization process by dynamic light scattering and UV-Vis spectrophotometry. The results indicated a higher sputtering yield in the colloids containing the polysaccharides. The colloids were also characterized by atomic absorption spectroscopy (AAS) to reveal the composition of the prepared nanoparticles by transmission electron microscopy (TEM) to visualize the nanoparticles and to evaluate their size and clustering, and by rheometry to estimate the viscosity of the colloids. The zeta-potential of the AuNPs was also determined as an important parameter indicating the stability and the biocompatibility of the colloid. In addition, in vitro tests of antimicrobial activity and cytotoxicity were carried out to estimate the biological activity and the biocompatibility of the colloids. Antimicrobial tests were performed by a drip test on two bacterial strains - Gram-positive Staphylococcus epidermidis and Gram-negative Escherichia coli. AuNP with chitosan proved to possess the highest antibacterial activity, especially towards the Gram-positive S. epidermidis. In vitro tests on eukaryotic cells, i.e. human osteoblastic cell line SAOS-2 and primary normal human dermal fibroblasts (NHDF), were performed after a 7-day cultivation to determine the effect and the toxic dose of the colloids on human cells. The studied colloid concentrations were in the range from 0.6 μg/ml to 6 μg/ml. Toxicity of the colloids started to reappear at a concentration of 4.5 μg/ml, especially with chitosan in the colloid, where the colloid with a concentration of 6 μg/ml proved to be the most toxic, especially towards the SAOS-2 cell line. However, the PEG and PEG-MC containing colloids proved to be relatively non-toxic, even at the highest concentration, but with a slowly decreasing tendency of the cell metabolic activity.

Effect of electrical discharge plasma on cytotoxicity against cancer cells of N,O-carboxymethyl chitosan-stabilized gold nanoparticles

Electrical discharge plasma in a liquid phase can generate reactive species, e.g. hydroxyl radical, leading to rapid reactions including degradation of biopolymers. In this study, the effect of plasma treatment time on physical properties and cytotoxicity against cancer cells of N,O-carboxymethyl chitosan-stabilized gold nanoparticles (CMC-AuNPs) was investigated. AuNPs were synthesized by chemical reduction of HAuCl₄ in 2 % CMC solution to obtain CMC-AuNPs, before being subjected to the plasma treatment. Results showed that the plasma treatment not only led to the reduction of hydrodynamic diameters of CMC-AuNPs from 400 nm to less than 100 nm by the plasma-induced degradation of CMC but also provided the narrow size distribution of AuNPs having diameters in the range of 2-50 nm, that were existing in CMC-AuNPs. In addition, the plasma-treated CMC-AuNPs could significantly reduce the percentage of cell viability of breast cancer cells by approximately 80 % compared to the original CMC and CMC-AuNPs.

Elemental Silver Nanoparticles: Biosynthesis and Bio Applications

The data on the specifics of synthesis of elemental silver nanoparticles (Ag-NP) having various geometric shapes (pseudo spherical, prismatic, cubic, trigonal-pyramidal, etc.), obtained by using various biological methods, and their use in biology and medicine have been systematized and generalized. The review covers mainly publications published in the current 21st century. Bibliography: 262 references.

Modification of Chitosan for the Generation of Functional Derivatives

Today, chitosan (CS) is probably considered as a biofunctional polysaccharide with the most notable growth and potential for applications in various fields. The progress in chitin chemistry and the need to replace additives and non-natural polymers with functional natural-based polymers have opened many new opportunities for CS and its derivatives. Thanks to the specific reactive groups of CS and easy chemical modifications, a wide range of physico-chemical and biological properties can be obtained from this ubiquitous polysaccharide that is composed of β-(1,4)-2-acetamido-2-deoxy-d-glucose repeating units. This review is presented to share insights into multiple native/modified CSs and chitooligosaccharides (COS) associated with their functional properties. An overview will be given on bioadhesive applications, antimicrobial activities, adsorption, and chelation in the wine industry, as well as developments in medical fields or biodegradability.

Photo-reduction of Ag nanoparticles by using cellulose-based micelles as soft templates: Catalytic and antimicrobial activities

Amphiphilic cellulose derivatives were synthesized from allyl cellulose (AC) and cystein (Cys)/n-dodecyl mercaptan (NDM) via the thiol-ene click reactions. The derivatives were self-assembled into micelles in distilled water, and the micelles sizes increased with an increase of the DS_NDM. The amphiphilic cellulose micelles were served as the soft templates for the controllable synthesis of Ag nanoparticles (NPs) through the photo-reduction. Ag NPs were embedded and stabilized by the amphiphilic cellulose micelles, and their sizes increased from 3.1 to 14.4 nm with an increase of the original template sizes. The catalytic properties of the Ag-loaded micelles were evaluated by the reduction of p-nitropheonl to p-aminophenol. The results demonstrated that the Ag-loaded micelles exhibited excellent catalytic activity. The reduction followed the first-order rate law, and the reaction constant decreased with increasing size of Ag NPs. Moreover, the Ag-loaded micelles displayed good antimicrobial activities to both S. aureus and E. coli. Therefore, the Ag-loaded cellulose-based micelles have potential applications in various fields.

The Performance of p-Aminosalicylic Acid As Reducing and Stabilizing Agent in Silver Nanoparticles Synthesis

In this study, silver nanoparticles (AgNPs) were successfully synthesized using p-aminosalicylic acid as a reducing and stabilizing agent simultaneously. The AgNPs was synthesized by mixing silver nitrate solution as a precursor with the pH adjusted by p-aminosalicylic acid solution and heating it in a boiling water bath. The formed AgNPs were analyzed using UV-Vis spectrophotometry to evaluate their SPR absorbance in the wavelength range of 400-500 nm. The optimum reaction time is 10 min and the optimum pH is 11. The AgNPs with the optimum synthesis condition have average size of 32.3 nm when characterized using PSA, spherical morphology when characterized using TEM, and face-centered cubic crystal when chara­cterized using XRD. The formed AgNPs had good stability for more than 2 months. The mechanism of silver ion reduction and AgNPs stabilization by p-aminosalicylic acid were also proposed in the paper based on the FTIR analysis result.

Chitosan based metallic nanocomposite scaffolds as antimicrobial wound dressings

Chitosan based nanocomposite scaffolds have attracted wider applications in medicine, in the area of drug delivery, tissue engineering and wound healing. Chitosan matrix incorporated with nanometallic components has immense potential in the area of wound dressings due to its antimicrobial properties. This review focuses on the different combinations of Chitosan metal nanocomposites such as Chitosan/nAg, Chitosan/nAu, Chitosan/nCu, Chitosan/nZnO and Chitosan/nTiO2 towards enhancement of healing or infection control with special reference to the antimicrobial mechanism of action and toxicity.

3D-macroporous chitosan-based scaffolds with in situ formed Pd and Pt nanoparticles for nitrophenol reduction

3D-macroporous chitosan-based scaffolds (cryogels) were produced via growth of metal-polymer coordinated complexes and electrostatic interactions between oppositely charged groups of chitosan and metal ions under subzero temperatures. A mechanism of reduction of noble metal complexes inside the cryogel walls by glutaraldehyde is proposed, which produces discrete and dispersed noble metal nanoparticles. 3D-macroporous scaffolds prepared under different conditions were characterised using TGA, FTIR, nitrogen adsorption, SEM, EDX and TEM, and the distribution of platinum nanoparticles (PtNPs) and palladium nanoparticles (PdNPs) in the material assessed. The catalytic activity of the in situ synthesised PdNPs, at 2.6, 12.5 and 21.0 μg total mass, respectively, was studied utilising a model system of 4-nitrophenol reduction. The kinetics of the reaction under different conditions (temperature, concentration of catalyst) were examined, and a decrease of catalytic activity was not observed over 17 treatment cycles. Increasing the temperature of the catalytic reaction from 10 to 22 and 35 °C by PdNPs supported within the cryogel increased the kinetic rate by 44 and 126%, respectively. Turnover number and turnover frequency of the PdNPs catalysts at room temperature were in the range 0.20-0.53 h^-1. The conversion degree of 4-nitrophenol at room temperature reached 98.9% (21.0 μg PdNPs). Significantly less mass of palladium nanoparticles (by 30-40 times) was needed compared to published data to obtain comparable rates of reduction of 4-nitrophenol.

Nanosilver: new ageless and versatile biomedical therapeutic scaffold

Silver nanotechnology has received tremendous attention in recent years, owing to its wide range of applications in various fields and its intrinsic therapeutic properties. In this review, an attempt is made to critically evaluate the chemical, physical, and biological synthesis of silver nanoparticles (AgNPs) as well as their efficacy in the field of theranostics including microbiology and parasitology. Moreover, an outlook is also provided regarding the performance of AgNPs against different biological systems such as bacteria, fungi, viruses, and parasites (leishmanial and malarial parasites) in curing certain fatal human diseases, with a special focus on cancer. The mechanism of action of AgNPs in different biological systems still remains enigmatic. Here, due to limited available literature, we only focused on AgNPs mechanism in biological systems including human (wound healing and apoptosis), bacteria, and viruses which may open new windows for future research to ensure the versatile application of AgNPs in cosmetics, electronics, and medical fields.

Electrospun Polymer Nanofibers Decorated with Noble Metal Nanoparticles for Chemical Sensing

The integration of different noble metal nanostructures, which exhibit desirable plasmonic and/or electrocatalytic properties, with electrospun polymer nanofibers, which display unique mechanical and thermodynamic properties, yields novel hybrid nanoscale systems of synergistic properties and functions. This review summarizes recent advances on how to incorporate noble metal nanoparticles into electrospun polymer nanofibers and illustrates how such integration paves the way towards chemical sensing applications with improved sensitivity, stability, flexibility, compatibility, and selectivity. It is expected that further development of this field will eventually make a wide impact on many areas of research.

Sugar-based micro/mesoporous hypercross-linked polymers with in situ embedded silver nanoparticles for catalytic reduction

Porous hypercross-linked polymers based on perbenzylated monosugars (SugPOP-1–3) have been synthesized by Friedel–Crafts reaction using formaldehyde dimethyl acetal as an external cross-linker. Three perbenzylated monosugars with similar chemical structure were used as monomers in order to tune the porosity. These obtained polymers exhibit microporous and mesoporous features. The highest Brunauer–Emmett–Teller specific surface area for the resulting polymers was found to be 1220 m² g⁻¹, and the related carbon dioxide storage capacity was found to be 14.4 wt % at 1.0 bar and 273 K. As the prepared porous polymer SugPOP-1 is based on hemiacetal glucose, Ag nanoparticles (AgNPs) can be successfully incorporated into the polymer by an in situ chemical reduction of freshly prepared Tollens’ reagent. The obtained AgNPs/SugPOP-1 composite demonstrates good catalytic activity in the reduction of 4-nitrophenol (4-NP) with an activity factor k_a = 51.4 s⁻¹ g⁻¹, which is higher than some reported AgNP-containing composite materials.

Biobased Chitosan Nanocomposite Films Containing Gold Nanoparticles: Obtainment, Characterization, and Catalytic Activity Assessment

A "green" two-step methodology to prepare biobased gold-chitosan nanocomposite films using chitosan and AuCl₄^- as a stabilizer and precursor, respectively, is reported. The biobased nanocomposites were prepared in situ by a wet chemical reduction method. Effects of hydrazine and l-ascorbic acid as different strength reducing agents on the characteristics of gold nanoparticles were observed. In addition, the performance of these nanocomposite films as catalytic materials was assessed. The relevance of this work underlies that the catalytic activity, conversion degree and order of the reaction of the 4-nitrophenol-sodium borohydride (4NP-NaBH₄) reduction system depend on the size distribution, content and mainly to the location of gold nanoparticles in the nanocomposite films. Finally, the potential recyclability of these nanocomposite films as catalytic materials was studied.

In situ green synthesis of antimicrobial carboxymethyl chitosan-nanosilver hybrids with controlled silver release

In order to fabricate antimicrobial carboxymethyl chitosan-nanosilver (CMC-Ag) hybrids with controlled silver release, this study demonstrated comparable formation via three synthetic protocols: 1) carboxymethyl chitosan (CMC) and glucose (adding glucose after AgNO3), 2) CMC and glucose (adding glucose before AgNO3), and 3) CMC only. Under principles of green chemistry, the synthesis was conducted in an aqueous medium exposed to microwave irradiation for 10 minutes with nontoxic chemicals. The structure and formation mechanisms of the three CMC-Ag hybrids were explored using X-ray diffraction, ultraviolet-visible spectroscopy, transmission electron microscopy, and Fourier-transform infrared analyses. Additionally, antimicrobial activity and in vitro silver release of the three synthesized hybrids were investigated in detail. The results revealed that a large number of stable, uniform, and small silver nanoparticles (AgNPs) were synthesized in situ on CMC chains via protocol 1. AgNPs were well dispersed with narrow size distribution in the range of 6-20 nm, with mean diameter only 12.22±2.57 nm. The addition of glucose resulted in greater AgNP synthesis. The order of addition of glucose and AgNO3 significantly affected particle size and size distribution of AgNPs. Compared to CMC alone and commercially available AgNPs, the antimicrobial activities of three hybrids were significantly improved. Of the three hybrids, CMC-Ag1 synthesized via protocol 1 exhibited better antimicrobial activity than CMC-Ag2 and CMC-Ag3, and showed more effective inhibition of Staphylococcus aureus than Escherichia coli. Due to strong coordination and electrostatic interactions between CMC and silver and good steric protection provided by CMC, CMC-Ag1 displayed stable and continuous silver release and better performance in retaining silver for prolonged periods than CMC-Ag2 and CMC-Ag3.

Blend Hydrogel Microspheres of Carboxymethyl Chitosan and Gelatin for the Controlled Release of 5-Fluorouracil

Carboxymethyl chitosan (CMCS) was synthesized and blended with gelatin (GE) to prepare hydrogel microspheres by w/o emulsion cross-linking in the presence of glutaraldehyde (GA), which acted as a cross-linker. 5-Fluorouracil (5-FU) was encapsulated to investigate its controlled release (CR) characteristics in acidic (pH 1.2) and alkaline (pH 7.4) buffer media. The microspheres which formed were spherical in nature, with smooth surfaces, as judged by the scanning electron microscopy (SEM). Fourier transform infrared spectroscopy (FTIR) confirmed the carboxymethylation of CS and the chemical stability of 5-FU in the formulations. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) confirmed the physical state and molecular level dispersion of 5-FU. Equilibrium swelling of microspheres was performed in water, in order to understand the water uptake properties. The in vitro release of 5-FU was extended up to 12 h in pH 7.4 phosphate buffer, revealing an encapsulation efficiency of 72%. The effects of blend composition, the extent of cross-linking, and initial drug loading on the in vitro release properties, were investigated. When analyzed through empirical equations, the release data suggested a non-Fickian transport mechanism.